Home

Design of an Unmanned Aerial Vehicle for Martian Exploration

1. 8 L 9 S D A L eDpug Aeujer Ag NMYYA 30 0 39vd NOISIA3H nl quu 0 UOISIJA eue dyoeg L epuc e L Zpun e LU Banzereq E L BeNzeieg e p99Azsng m po9Azsng Vr psogzeriea Es psogzeiea E Eepuo Sr L pnup Sr ZH LOIS zd 1018 Eepuo Ss L pnup Se L BeNzeieg benzeyeq ET 1 banzereg e Ver 99AZSn 99AZSnN O Ors L 99AcSng 7 1 99 Zsng sodzejeq Ce sodzeyeq Ge AL Vou o 1 SOJZe1eQq Lo Lepuo gt L zpuo So l v 9 c9 LOIS gO LOIS Lzpuo lt gt 0 O i 1 99AZSNg z Lo Lcpuo Ca L gpuy s 14V zsng Banzereq 3 Bbeanzereq LUH 1 99AZSNg pooAzsng B L Sogzereq ES L Sogzeieq Ss 6 bencejeq Ligpu5 Si b gpu or O Ok 24 1018 za LOIS AL deu L pun d L gpuo 5 psogzeieq 2 GO LU banzereq e 1 banzereg m O Long 2 LO 1 00AZSng Lo9Azsng s O 1 99AZSNG Z O L sogzeyeq Se psogzeieg WA 3403 zsng Lizpu 5i L gpug SI bird 23 1018 eV LOIS 8 yA 9 S D E L 156 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS jo y aBed EQ uosa aJempey pipoq auejd
2. eDpug Aer A9 NMYYA 30 LO 39vd L 99A NOISIA3H qu il z s i quu ana ATS c0 UOISISA peog OIpEH LX1gsng b az kaya Z GE va r aesng 3q 8 Lux Lesng 3 SL z Exyesng lt Ar TI OF H esna 2LGAHS9NS vn 1 99 i ONS 99 Pg og 9 L XLesng pra az y n l 00AZSng 4 30 GES 8 Lugxiesng d 5 i Ar d un Or EXHesng d zsng c LOAHS9NS en 1 99 ill an9 99 g img 9 LXLLSng cf az y n 00ALSng 30 EIS JS 8 Lu LL sng 3 d gt z ii EXHiSng lt ep T OL g Isna c LOAHS9NS en LEIDA uf S 9 WOr1LSdlS nena an PANS ji J va ZA L xLosng por g z v L vis LooA0sng e HEEE 1 99AZSNg vo O 29 19 30 gt E 8 JN ed kuga osng 3 d gt 2 z ni np n nu LA Nor iSd1S 00prsng ps J cd i Exgosng 47 7 L 09Asng EIDA H osna WOPTISdLS L o0A0sna J LO 2LGAHS9NS LA 6 Z 9 S z L 166 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS JO Z abed EQ UoISIA 1 aJempey pyeoq oipe JO JIJWOYOS WOU g pg anbi
3. 8 L 9 S v z L eDpug Aeujer Ag NMYYA 30 20 39vd NOISIA3H nl quu 0 UOISIJA eue dyoeg E Pu e pue e 1 Ban era E L Don Leea e 1 99 sng ES 99A 1SNg 3 1 SOg eq e SOd Leeq e ELPU 5i E pu En LH 1078 LO 1018 L LPU e pue 5 LU Don eea B N peyeq ET Bon eea e vir 99 SN 99 LSN O Ors 1 09 1sng 7 29A Lsng SOd rereq Ce SOd e eq Ge AL VIH o sog Leieq Lo L Pu gt pue So VI Io LOTS L9 1018 ELpug lt gt 0 Oo L 399A Lsng z Lo LLDUE Ce pue s 14V isng B N era 3 1 6aN eea LUH 1 99 Lsng 3 99A LSng sog Lereq ES sog L amp a Ce Do Leea dir PU m LLDUp 5i S ok Ld LOIS id LOIS AL dtd HELPUS J L pue L sogpereq 2 GO L N LEI e Dan eea m O pub C oro p o9ALsng 1 99 Leng O L 399A sng Z O Sog Leled Se sog L amp a WA SE pub T l puD OL 13 1018 Lv LOIS 8 yA 9 S r 4 L 155 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS JO aBed EQ UuoISsIA 1 aJempey pipoq auejdy9eq JO JIJWayYos WOU e g anbi
4. 8 L 9 S v z L eDpug uJj r Ag NMYYA 30 20 39vd NOISIA3H qi qui ZO UOISJOA peog OIpey 49 0J10090J9 A oL 024 9 S 7 do y L zo z ge IN lad 13S3u 1I9SOL LTV1X IHd ye ZHN 80264 T X T do Ps T T T T z L ye Viva Idd zoSO L 1V LX Od gg 029 n n 7 24004 dnOL 3U001 3U001 4U00L ANOL KIJA HAV Idd Zei 920 ScO ved E zz j ar Verte Ree 1 2 peog L i i E VA d iss A Zp 20d M9S LOX1 00X1 0090 3d ec gt a Lal 021 l Sem Skies L99AV KIJA HAV Geld asna 5 3si 904 osiwaxe 0ax 0000 zaa Pag lt lt Hesna PuaxLisng lt et S9d ISO LO 19S 049X 8090 kid 6z gt HUAXLesn8 anyo aeo 70d SS V190 vas vooo 03d gz maoni gr 0d oqxi qooo 001 KE Lxyosng kid opey L o9A gsn8g A ju gt 1zo4 00Xu 2090 4OS LOXL Gd Zz zt i ecu eu pudxiosnH lt j Tp Od 198 049X 8090 OSIW LGX saa lt Od DPE WW d peu OLY anyo T ozo o 09d vas vooo ISOW LMOX 8190 SQd az Loza TU SSN190 vdd ye Se 19 L NGHS olpey L xLesng L o9qzsng L n lt g vd 290 04X1 0090 dd gz gt 924 Sed FXL DE L 2 sva goqv oqxu o0oo zaa lt Fxdesng anyo gz9 LO 1X8 Opey Lie
5. 8 L 9 S r z L eDpug Aeujer Ag NMYYA 30 LO 39vd NOISIA3H nl qui 0 UOISIJA eue dyoeg LODUE e L 0puS e LU DoNOEIEO E Bbenoereq e 1 990SNg a L 99A0sng Z Lisogoereq 5 Lisogoereq 5 L 0puo Sr L 0puS Sr 0H 1018 0d 1018 L 0puo Ss L 0puS Se 1 Danoe1reg 1 B9NOe1eg ET L DeNoeieg e vor 99 AOSN 99A0Sn O Ors L 99A08ng 7 1 99 0sng sOJOR1eQ Ce L soqoejeq 6 AL voy o L sogoerea o HOPUI gt US bi I v 9 09 101S 09 1078 Lopuo lt gt 0 Oo A 1 992A0SNg z Lo LODUE Ca L opu5 s 14V osng LU Banoereq 3 Banoereq LUH kodAosng ur L 99A0sng B L soq0eleq ES L sogoeieq Ss LC Banoereq Se Lopuen i L opuo Si o ok 04 1018 08 10718 AL 304 m KOPUI d L opuy S psogoeieq 2 GO 1 banoe1eq e Banoereq m O popup lt gt 2 0 1 0040Sng 1 090sNg s O 99A0SNG Z O L sogoereq Se sOJOe1eg E 3403 0sna L 0puo Ss L 0puS E LUH 03 101S ov LOIS 8 L 9 S r z L 154 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS JO Z abed EQ UuoISsIA 1 aJempey pipoq auejdy9eq JO JI wayos WOU z g anbi
6. 6 8 Z 9 E n z ueubpoJg ueqog Aa NMVEO 40 0 39vd a NOISIA3H nig E wer marum Z0 ue preog Odo 77 oeo oe GeO ved S ZOd ISOdN LeWd Pa 1 2 FISOdN S il jm 389 ZSOdN LOUW OEVd ap 1 00 6eu ZITO Pip BAC SE broyresaszva Peg 1 2 F39 Od E u le I do zaou Ialaisiawoauzvd 7g gt FOI 91H Y FISH WHY lt gt 689 Sege zerg T zvoLL LQOQ tLaWod Szvd Foz 1 sey do CN zg NONOA NIX Znma 1s 10 29 d savd Lg PAM keser dT8VSIG DVIP 401 db i inox IWMd ISLU Z LOWS a v Peg e SH L 09A OWMd iXos LLawodiezva LC HOS Wav L EDDA Hisy aworg Fd d lt gt yaa ESOdN LOXLOLWOdzevd y KHAKI Wav 3 I PRAT enaa 4 waa biogrtaxuieawodnzva r L FHGXH Way A L oz er 10 LdOW EDA DEN caviooHl du eaWod 0zvd Poy si ISi u ren Z zg asvua ZWO MIZANI Ld gr wren o ha a SI awa sch 0 eu op isl oav bod QL SaWod Z Wd 6 E m I igoLLPLsQWod eiva Fer Pd ld dd far m GE LSHN ivoiu4ueqwodeivd gg JE 4 9 HRH IESEL eM dpiods zaWod vivd iz PAOS Way u ag Tasovir ZWMdISOW LANDd elvd zz 2 FISON Way le KR t gg NOL iWwq osiwoqwoqzivq zz lt _ FOSIN Wav ho 1 gl snu OWMd OSOdN EWWDd t Lyd sl gt OSOdN s odL ZSOdN OXLO ZWWOd 0L vd Paz 1 allt LSOdN OXHQ LINWOd 6vd Fog _ g r ouiav ios
7. J i ange 1 MW106L OTT za SEET N a o ow 4u004 an any HNOOL a o Elte 1297 0 23 dE T WILD 8 MSA E EDDA 071 du04 S S 1 ELO L go T UlA L EN VvWOOr nol es Wain DE ACC MOA z z O O e on AGL 01 01 UA 185 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 6 JO 8 Abed 20 UOISIAJI aJempJey pueoq Oc JO JIJWOYIS 1In9JI ee g anliy 8 S ueuooJg H qOY A8 NMYYA 30 90 39vd NOISIA3H END quiu ZO UOISJOA pJeog Od5 eoepelu uog eues 6 OL Gau 31osNoo lt cl KIKI 3OSNOO gt mo xd ul xd Ul XL MO ZXL N 3J3n0O 089 by EDDA Ol Di nrollego 9 9 gt npo llega O nro llego 21 9 nro ll 180 Len ZEZXYN 186 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 6 Jo 6 Abed 20 UOISIAJI aJempJey pueoq Od JO JIJWOYIOS PNN pe g n6i j S eDpug Aer A9 NMYYA NOISIA3H 30 60 39vd Ald ZO UOISJOA pJeog Od5 390 O oul eed TUIL La 014 nor Old C H OTOL OH _ 2
8. 140 A 7 3 Step 3 Model FittingandAnalysis i 141 deg A Ree ded oe dos 2 144 A 8 Compiling the ARM Development Toolchaini 146 A 9 CompilingopenOCD 150 A 10 Safety Precautions 151 A 10 1 Lithium Polymer Batteries 151 A 10 2 R C RVING 3 24 2 te bees Sus mam Eve Ge Q ma S an hd deos 151 A 10 3Constructionj 152 A liLegalReguiremenitsi 152 A 11 1 FCC Radio Frequency Regulations 152 A 11 2 FAA Flight Regulations 152 153 Electric Owl Final Report 4 CONTENTS C Assembly Instructions and Bill of Materials C 1 AircraftHardware ee Poe WA aa Wa WE C 2 1 Backplane revision 03 C 2 2 Servo Board revision 03 C 2 3 Radio Board revision 03 C 2 4 Sensors Board revision03 C 2 5 GPC Board revison02 _ __ C 3 Additional Tools C 3 1 Airframe Construction C 3 2 Software Development C 3 3 Testing Supplies D 2 Expenses Electric Owl Final Report List of Figures 2 1 System block diagram of some of the features that might be needed for a Mars Le nh hk eh OO A RAR a eee de A 16 3 1 Photograph showing all four t
9. 168 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS JO y abed EQ UOISIA 1 SJeMpey pyeoq oipe JO JIJWIAYOS WOU 9 g anbi L 9 S v z eDpug uJj r Ag NMYYA 30 90 39vd NOISIA3H nl TUL ZO UOISIJA pJeog oipey iddns Jamod OIPey AG wt n Sa L MV1081 T 088 3 MV10 L9 2 o a any Ant any Hn o m 299 199 099 T UAW MS z 8 091 20011 H 8LLIZZbbL eo 1 1008 INSZ9ZZW1 UIA 1 uA Vi nol z z L 3909ASng AG 1noA precio O loo ro 09n AGI 9101 UIA L 9 S Y z 169 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS JO G abed EQ UoISIA 1 SIEMPIEY pyeoq oipe JO Ol euu uos WOU Z pg anbi L S eDpug Aer A9 NMYYA NOISIA3H 30 40 39Vd ad ZO UOISIJA peog OIpey TUL iddns Jamog 21601 A DE MV108L HOT wa STE s a o a 3u00l nt nt HNO F o O zo LOFT 0403 elt T VA A 8 MSA z z Kai 01 La 29 IO m UA 7 mie VWOOp INO zig erai L 00Asng A InOA z z O O o I 04n AS 9101 UA 170 Report ina F Electric Owl APPENDIX B SCHEMATICS
10. 39 O I 10S 1994 208150 ONE 2 299 L EN oen ZH 8977 L F uoot 069 EDDA 187 Report ina F Electric Owl C Assembly Instructions and Bill of Mate rials C 1 Aircraft Hardware The final prototype aircraft began as an off the shelf Senior Telemaster from Hobby Lobby International Inc This is a large model aircraft frame with a 2 m wingspan and is available pre assembled in a almost ready to fly ARF kit Qty Part Mfr Description 1 Senior Telemaster Hobby Lobby ARF RC airframe kit 1 4120 18 Axi Main drive motor 5 HS 322HD Hitec RC Servomotors 1 511 Steel Rod Sullivan Control Set straight linkage 2 580 Precision Rod Sullivan Control Set carbon fiber reinforced 2 3 25 in rubber wheels Dubro Main landing gear 1 LP 13080E 1 AR6200 Spektrum 1 VEN 15021 1 JSP91010 JR Sports 1 DXei Spektrum APC Propellers Venom Power Composite propeller 13x8E RC receiver 5000mah 22 2V Li Po battery 4 8V 700mah NiCd battery 6 channel RC transmitter 2 4 GHz Table C 1 Bill of Materials for Test Airframe Electric Owl Final Report 188 APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS C 2 Avionics Package Once the bare circuit boards have been divided solder paste can be placed on all of the populated pads This can be done eithe
11. b Power the backplane by plugging the wall adapter end of the shore power cable into an available wall socket and the other end into one of the RS 485 jacks on the backplane c Take the AVR programmer and attach the PDI programming header to the appro priate site on the target board Note that the connector is keyed and will only attach to the target site in one way Plug the USB end of the AVR programmer into an available USB port on the PC Check that the status light on the AVR programmer is green If it is red double check that the system is powered d Change to the software majortom directory and use the avr program sh script to do the programming As an example if the program to be loaded is located in the software majortom build avr directory and is called prog hex then the following command sequence will carry out the programming avr program sh build avr prog hex The status light on the AVR programmer will blink as the program is written into memory When it is finished a line like the following will be displayed avrdude verifying avrdude 11298 bytes of flash verified avrdude safemode Fuses OK avrdude done Thank you The program will automatically begin execution NB This step may require root permissions if the account of the user doing the programming does not have access rights to the system s USB hardware Electric Owl Final Report 116 APPENDIX A USER S AND SAFETY MANUAL
12. Electric Owl Final Report 111 APPENDIX A USER S AND SAFETY MANUAL from the range checkpoint 3 Pre Flight Assembly and Testing Follow these steps to get the plane ready for flight The ground control computer s should be set up while this is occurring for maximum efficiency a Attach wings to plane using rubber bands looped around the wooden pegs on the top of the airplane The wings should be attached with several rubber bands con nected in each of the following three configurations e Fore to aft parallel to body e Fore to aft diagonal across body e Left to right parallel to wings transverse to body b Inspect the propeller for damage and replace it if needed c Ensure that the NiCd battery switch is flipped to the off position d Install the main lithium polymer propulsion battery in the plane but do not connect it yet e Perform a weight and balance check Make sure that the plane s center of gravity is in an acceptable position If necessary try to enlist one of the experienced RC pilots to assist with this task f Turn on the 6 channel RC transmitter g Flip the manual override switch to the on position towards the operator h Flip the NiCd battery switch to the on position i Use the RC transmitter to check that at least one of the control surfaces moves correctly j Move the plane manually out to the motor testing area At Dick Scobee Field this is jus
13. A 3 2 GPC ARM Microcontroller The procedure for programming the GPC ARM microcontroller is only slightly more com plicated than that for programming the AVRs Programming the ARM requires the fol lowing The target board to be programmed The program to be flashed in the form of a e1f file This should be produced automatically when the program is built using the project make scripts One backplane board with at least one RS 485 connector and at least one row of circuit board connection headers One ARM USB OCD programmer One shore power cable One PC with all necessary software dependencies installed a copy of the project Git repository and at least one USB port To program the ARM follow these steps a b c Take the backplane board and insert the target GPC board to be programmed into an available row of circuit board connection headers Power the backplane by plugging the wall adapter end of the shore power cable into an available wall socket and the other end into one of the RS 485 jacks on the backplane Take the ARM USB OCD programmer and attach the programming header to the appropriate site on the target board Note that the connector is keyed and will only attach to the target site in one way Plug the USB end of the programmer into an available USB port on the PC Electric Owl Final Report 117 APPENDIX A USER S AND SAFETY MANUAL d Inside the software majortom s
14. apal rice edu jabI rice edu SLOT_D3 SLOT_D2 SLOT_D1 SLOT_D8 00000 00000 OO OOO 00000 00009 000091 00009 00009 rtb1 rice edu pch1 rice edu SLOT_E3 SLOT_E2 SLOT_E1 SLOT_E 00000 00000 00000 00000 00009 00009 00009 000009 SLOT F3 SLOT_F2 SLOT_F1 SLOT_FA 00000 00000 00000 00000 00009 00009 00009 00009 SLOT_63 SLOT_62 SLOT_61 SLOT GB 00000 OO OOO 00000 00000 00009 00009 000009 00009 HET SLOT H3 SLOT_H2 SLOT_H1 SLOT_HA 00000 00000 00000 00000 00009 00009 00009 000091 Sa a Si CR ooo ooo ooo ooo L OO CN Cu q Electric Owl Final Report 190 Ier Figure C 1 Front assembly diagram for Backplane Rev 03 reproduced to scale The silkscreen indicates the component reference designators for the corresponding pads Part information for each reference designator is in Table C 2 APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS Figure C 2 Front assembly diagram for Servo Board Rev 03 reproduced to scale The silkscreen indicates the component reference designators for the corresponding pads Part information for each reference designator is in Table Figure C 3 Front assembly diagram for Radio Board Rev 03 reproduced to scale The silkscreen indicates the component reference designators for the corresponding pads Part information for each reference designator is in Tablet A Electric Owl Final Report 191 APPENDIX C ASSEMBLY INSTRUCTI
15. 166 B 14 Radio board revision 03 circuit schematic 2 5 167 B 15 Radio board revision 03 circuit schematic 3 5 168 B 16 Radio board revision 03 circuit schematic 4 5 169 B 17 Radio board revision 03 circuit schematic 5 5 170 B 18 Sensors board revision 03 circuit schematic 1 8 171 B 19 Sensors board revision 03 circuit schematic 2 8 172 Sup hua aan 173 B 21 Sensors board revision 03 circuit schematic 4 8 174 B 22 Sensors board revision 03 circuit schematic 5 8 175 B 23 Sensors board revision 03 circuit schematic 6 8 176 B 24 Sensors board revision 03 circuit schematic 7 8 177 Electric Owl Final Report 6 LIST OF FIGURES B 25 Sensors board revision 03 circuit schematic 8 8 178 B 26 GPC board revision 02 circuit schematic 1 9 179 B 27 GPC board revision 02 circuit schematic 2 9 180 B 28 GPC board revision 02 circuit schematic 3 9 181 B 29 GPC board revision 02 circuit schematic 4 9 182 B 30 GPC board revision 02 circuit schematic 5 0 o 183 IET LLL 184 B 32 GPC board revision 02 circuit schematic 7 9 185 B 33 GPC board revision 02 circuit schematic 8 9 3J 18
16. CHAPTER 3 FINAL DESIGN Navigation The navigation component takes low level sensor readings such as accelerom eters and gyroscopes and integrates them into a coherent picture of the state of the vehicle Internally it uses quaternions to track the attitude in three dimensions to avoid the problem of gimbal lock From this internal state it outputs the more traditional heading pitch and roll angles which are then used by the other software components Guidance The guidance component is primarily concerned with interpreting the step by step flight plan which has been input by the user Its job is to decide when a given flight segment has been completed so that the plane can begin executing the next flight segment It also has a facility to watch for various possible error conditions altitude not sustained wind too strong location too far from home base etc and automatically switch to a contingency plan when necessary Using the current step in the flight plan it calculates a desired orientation to move the vehicle closer to the right position The desired orientation is then used as input data for the control component Control The control component performs low level vehicle attitude and thrust manipulations It compares the current attitude as calculated by the navigation component to the desired attitude output by the guidance component then decides what control surface movements will best move the vehicle toward the desired
17. plete receipt of a bus packet 3 8 3 Hardware Revision Ill The third revision of the hardware adds mounting holes to the circuit boards and fixes the yaw gyro issue in the servo board by replacing it with the analog sensor that was mistakenly ordered Backplane 03 e Labels should be added to the bus connectors to simplify use Sensors 03 e The EOC pin on the Bosch BMP085 pressure sensor is not connected to anything Hook ing up to a pin on the AVR would save the need to use a timer counter to delay for 25 5 ms while waiting for the sensor to complete a conversion GPC 02 e The numbering of GPC boards is confusing This originated because the second revision of the hardware was the first to include the GPC board In the future the numbers should be aligned Electric Owl Final Report 84 4 Testing and Results 4 1 Basic Functionality Testing 4 1 1 Electrical Testing The electrical connectivity of each circuit board was thoroughly checked after assembly with a digital multimeter DMM before the board was ever powered up for the first time This allowed the team to detect electrical problems due to open or shorted traces before they could damage any of the sensitive chips Once a board passed its check for opens and shorts it was attached to a backplane and powered up The DMM was again used to verify the voltage levels at the output of each board s power regulators were correct If they were then the team
18. 644 Data Figure 3 4 Byte structure of a downlink packet Protocol Signature Protocol signature bytes were added to the downlink header in antici pation that the downlink protocol would evolve in the future The signature bytes encode the version of the downlink protocol being used These bytes allow users to easily distinguish between sets of hardware using different versions of the downlink protocol Packet Types There are three types of downlink packets These types and the correspond ing values for the packet type field in the downlink packet header are given in table 3 9 Like for bus packets since the system uses few of the possible values for the packet type byte it is easy to expand the system to accommodate more packet types by defining new bytes as needed Packet Type Byte Description DL TYPE TELEMETRY 0x40 Telemetry packet DL TYPE STEP READ 0x42 Read flight plan step from memory DL TYPE PTR READ 0x44 Currently executing flight plan step Table 3 9 Downlink packet types and corresponding identification bytes Electric Owl Final Report 67 CHAPTER 3 FINAL DESIGN Telemetry Packets The most common type of downlink packet is the telemetry packet indi cated by a DL_TYPE_TELEMETRY packet type byte The structure of the data field for a telemetry packet is similar to that for a BCMD_TELEM_REPLY bus packet it consists of a list of telemetry channel codes each immediately followed by a piece of t
19. continuously print information about the sensor data it had received and how it was processing it The debug stream was then carefully checked to make sure that the results of its processing conformed to the desired behavior outlined in section 8 3 2 In particular the team was able to confirm the correct operation of the outlier rejection procedure by watching the GPC identify and set aside wild values from one of the noisier pitch gyroscopes on one of the sensors boards The team also performed tests in which all three redundant sensors boards were loaded into the airplane and the GPC was programmed to maintain a fixed pitch Tilting the airframe off pitch would cause the GPC to respond by moving the plane s elevator to compensate The team then yanked the sensors boards out of the airframe one by one to confirm that the plane could react to the loss of sensor data on the fly and still respond correctly when tilted Finally the team also tested the ability of the system to process redundant sensor data in a real flight environment The results of the flight test are described in section 4 4 6 4 2 Sensors Calibration Before the sensors could be used to determine the plane s orientation they first had to be calibrated to remove zero offsets and scale their outputs into the ranges expected by the au topilot algorithm This section describes the team s general approach to sensor calibration Electric Owl Final Report 86 CHAPTER
20. layer does not display the track history on its own during live operations A saved telemetry log file can instead be loaded using the UAV telemetry static vector layer 3 4 4 UAV Support The ground software has a number of features to support development and testing of the UAV some of which were mentioned in the previous section The application can connect to the Electric Owl Final Report 56 CHAPTER 3 FINAL DESIGN telemetry radio over USB plug into one of the onboard communication buses using a USB to RS485 adapter and connect over a network or locally to another PC running the X Plane flight simulator In addition a joystick can be connected to provide a form of manual flight control with some differences from the R C transmitter discussed elsewhere All of these links can be active at once and the communications are handled in a separate software thread to avoid delays caused by other components of the application There are several modes available under the UAV menu to accommodate different testing and flight profiles The X Plane mode is used merely to fly a remote X Plane instance using a joystick attached to the ground software The HITL Hardware In The Loop mode connects the X Plane flight simulator to a GPC board running the autopilot algorithm for development and testing of the autopilot The Live mode receives and records telemetry using the radio link displaying the airplane position both o
21. the same way that the Earth s gravitational field serves as a reference for the accelerometers Unfortunately while the Earth s magnetic field is locally of approximately constant strength and uniform direction when away from buildings and large metal objects as desired it is difficult to precisely determine the field direction Knowing the field direction is important because it gives the direction along which the magnetometers should register their largest values Knowing this maximum is critical for choosing scaling constants that make the magnetometer values range as large as possible for maximum sensitivity while keeping it confined to the range Electric Owl Final Report 87 CHAPTER 4 TESTING AND RESULTS representable using a 16 bit integer type Thus a slightly different calibration technique had to be developed The procedure the team came up with is as follows The Earth s magnetic field is still used as a reference but instead of trying to take measurements along each axis separately a large number of measurements from all three axes are taken simultaneously with the magnetometer oriented in a variety of different directions These measurements are then plotted as points in three dimensional space one coordinate dimension for each axis of the magnetometer where they form an ellipsoidal point cloud By taking a large number of measurements with the sensor oriented in many different directions the equation of this ell
22. there would still be no collisions Electric Owl Final Report 43 CHAPTER 3 FINAL DESIGN 3 2 7 2 Custom Real Time Kernel Overview The ARM microcontroller runs a custom written kernel named MAL This ker nel provides scheduling timing interprocess communication IPC and interrupt management features Because the microcontroller does not have a Memory Management Unit the kernel does not provide memory protection between different threads Furthermore the kernel also does not provide dynamic memory allocation this eliminates the program space runtime and memory overhead costs associated with an allocator as well as helping the developer to ensure that the firmware remains strictly within the bounds of the available RAM resources Tasks and Contexts The kernel allows for an arbitrary number of user threads to be present and provides a separate user stack registers and instruction pointer for each thread The kernel uses only a single privileged mode stack so there is only one kernel context This means that context switching between different user threads is performed when the kernel returns out from kernel mode to user mode rather than switching from one kernel context to another The kernel provides a macro called STATIC_TASK which statically allocates all memory required for a thread and adds it to the scheduler One of the arguments is a stack size for the new thread so the developer must take care to choose a suff
23. 2 4 GHz for the 6 channel Spektrum transmitter by placing the one pilots AMA ID in an appropriate slot at the frequency registration station and taking the corresponding frequency tag c If no member of the team is a competent RC pilot and the plane will need to be flown under manual control for at least part of the flight test negotiate with the pilots at the field and see if one would be willing to assist the team with flying the plane manually If one agrees instruct him or her in how to operate the team s hardware in particular give the procedure for manually activating and deactivating the autopilot 2 Transmitter Range Check Use the following procedure to check the range on the RC transmitter a Ensure that the plane is unpowered b Have one member of the team take the RC transmitter out to the range check point At Dick Scobee Field this is marked by a large pole in the ground on the west side of the flight field c Have a member of the team power the plane s control surfaces by flipping the NiCd battery switch to the on position d Have the team member out at the range point test movement of all control surfaces using the RC transmitter Be sure to check the functioning of the autopilot manual override toggle switch as well e If everything worked remove power from the plane by flipping the NiCd battery switch to the off position and have the team member with the transmitter return
24. 2010 10 08 59 AeroVironment Inc Small Unmanned Aircraft Systems Puma AE avinc com uas small uas puma last checked 2010 10 08 60 Real Time Engineers Ltd The FreeRTOS Project http www freertos org Electric Owl Final Report 106 A User s and Safety Manual This User s and Safety Manual contains procedures for performing the most common tasks required during development and testing of the team s project and guidelines for safe operation of the aircraft Procedures for performing tasks on the computer are written assuming a Linux based operating environment with all of the project s software dependencies installed see section A 2 If a different environment is used then the procedures will need to be changed accordingly A 1 Flight Test Procedures This section summarizes the team s recommended procedures for carrying out a flight test In particular section contains a checklist of items that should be brought to the test site A 1 1 The Day Before The day before the flight test be sure to do the following e Check the weather forecast In particular be sure to check wind speeds and plan to test during periods of low wind activity The team has found that in Houston the best times to fly are in the early morning between 7 00 A M and 11 00 A M e Check that all of the circuit boards have been programmed with the appropriate version of the code e Perform a ground test of the functionali
25. 4 TESTING AND RESULTS For specific step by step calibration procedures using the programs and scripts developed see section Accelerometers Each axis of the three axis accelerometer is calibrated individually First the sensors board is oriented such that the axis to be calibrated is aligned pointing directly at the ground Several measurements are taken with the accelerometer in this configuration and then averaged together to curtail noise to form an estimate for the sensor s value with the axis aligned with the direction of gravity i e for an acceleration of 1 G Next the board is rotated such that the axis to be calibrated is aligned pointing directly upward Again several measurements are taken and averaged together this time to get an estimate of the sensor s value with the axis antiparallel to the direction of gravity i e for an acceleration of 1 G These two points lie on a line The slope and vertical intercept of this line can be used to correct for any zero offsets and to scale the axis output into the same range as that of the other axes This calibration procedure cannot correct for cross axis correlations due to non orthogonality of the axes however practice has found these effects to be negligible and the above procedure to be adequate Magnetometers Ideally the magnetometers could be calibrated in the same way as the accelerometers one axis at a time using the Earth s native magnetic field as a reference
26. 898UU019 9909V SIXV dul Gee IXav s d Bojeuy oSA L VO1 9L SIXV 19S SWIN AdOOSOYAD H1VOESA1 SOUONIDASOIMALS Lyn 1 S080 HZX AY ANZ YAO dVO AN UZA Zaza ZANE uapn ore dvo gro c S080 HZX OIINVH3O AOS 4d00001 dVO CO Le NHM oabe avo Yro c CWS S080 M8 L WHO M0 OI S3H 2001 4dZ30LYON wyoy rH OVH c S080 HZX AOS 9601 ANZ INH3O dVO VZ1WX 21955080 XAV Gto OvO VO CWS S080 M8 L WHO M0 SJH c0 JdZ30LHON wyoy FEU Zvu lb VOT 9L SIXV 1VNG SWIN 3dO9SOHA9 TWOEGHd1 SoIuoJoe eoJ9IIALS om S080 HZX 9601 AY 4NF 439 AVI GLOVMTOLOLZH6LZINHO ereny v0 Oro c ANS 0Z A 9 4N0L LNVL dvO H8W90LPOdOL wyoy PPO IPO 3 S080 HZX 9601 ASZ ANGI H39 AVI TLOVMESI3LZHSLZINHO ereny 9 9 ANS S080 GL M8 L WHO M0 Z2 S3H ZOL24dZ50LHOW wyoy SEH AWS S080 L M8 L WHO 0 02 SAY Z00 4dZ50LHOW wyoy ley OSH zc ANS S080 GL M8 L WHO M0 OI S3H 2004244230 HOW wyoy EECH J911 duy euore Jedo SONO lddnS lBu S xew O ANGO 0 GIVS vdO LL zen S080 HNO H3AV ILETQGIN YOLINAONI LINOOL37Z LOZZ TIN yal 0 1 G ER TWN dOS siosu s eunsseJqd JUNON pieog dQ200ZAXdlN 9 e959914 len 1 ZED S080 HZX 960L AY 4NF H3O dVO GLOVMTOLOLZH6LZINHO ejem GEO EEO ZED LED S AWS 9602 A 9 ANOL LNVL dvO H8W90LPOdOL wyoy vyeo OED c uonduoseq Med JUN JUN sopjeg O g0 eH PIBOg SIOSUSS JO s eueje N JO 118 CG eiqer 201 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS A
27. A USER S AND SAFETY MANUAL 12 After collecting data for about 60 90 seconds stop the busmonitor data capturing pro cess by sending it a CTRL C character Take the data file and save it somewhere where it can be accessed for use in the pre processing step that follows 13 Disconnect the nickel cadmium battery Be sure to recharge it before its next use A 7 1 3 Gyroscopes The procedure for acquiring gyroscope calibration data requires the following materials e One backplane board with at least two RS 485 connectors and at least four rows of circuit board connection headers Make sure that no circuit boards are plugged into it e Sensors board with gyroscopes to be calibrated e One servo board e One radio board programmed with the radio firmware that will be used in actual flight In particular it must be capable of transmitting telemetry packets e One GPC board programmed with the GPC firmware that will be used in actual flight In particular it must be capable of issuing requests for high rate sensors data and using the replies to assemble telemetry packets containing the gyroscope data which it then ships to the radio board for transmission e One nickel cadmium battery with a connector attached for use with the low voltage bat tery input on the servo board e One shore power cable e One AVR programmer e XTend radio ground module Electric Owl Final Report 132 APPENDIX A USER S AND SA
28. AND CAD DRAWINGS 8 Jo Z abed EQ UoISIA 1 BIEMPJEY pipoq sJosues JO 9rjeuleuos Pno pz g anb L S eDpug Aer A9 NMYYA NOISIA3H 30 40 39Vd ad go UOISIJA peog siosuas TUIL iddns 1 Mm0d A AGA L MV1081 HOT wa STE s a o a 4u00L an Ant SEN o O zo LOFT 0403 elt T VA A 8 MSA z z gt 1 99 071 AUOL H S 2 1 99 m UA 7 mie VWOOp INO zig erai L 00Asng AE Ges poA z z O O o I 04n AS 9101 UA 177 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS g Jo g eDed go uolsIA 1 aJempey pseOg SIOSUAS JO orreuieuos PNO Se g anb 8 L 9 S e L II upguuyooig Yeqoy A8 NMVHG 3JO 80 39vd NOISIA3H ald anu CO VOISI9A pipog slosuas JEUOS 00N SdH Ja awojeubeyy ESdd Sd Himnos ueu s 9 op ut exi MO 2XL 77 S Em LXL Sad lt zi o Lou ul Xd Fer y yoz zeu mE XH Sd9 Wb ano p Eg Kale L L XL HVNOS Kg 9 oa NNOO Sd5 npo 11689 npo 1
29. After one GPC has been marked inoperative the remaining three boards still form a voting set and can correctly detect errors After a second failure the system is reduced to two working boards and is forced to depend on heuristics to determine which board is faulty if the two differ Electric Owl Final Report 80 CHAPTER 3 FINAL DESIGN 3 8 Errata and Revision History The electrical hardware within the aircraft has undergone three major revisions 3 8 1 Hardware Revision The first revision of the hardware was ordered in July 2010 Only the servo board was ordered and populated This allowed the team to produce initial firmware implementing the manual override and allowed initial flight testing The following is a complete list of known errata for Servo Rev 01 All Schottky diode silkscreens D40 D50 D60 D70 show the line at the wrong end of the diode The SOT23 6 footprints U30 U31 do not have any orientation marker The power jumper section could be improved by adding labels to indicate which side is LV_BUS and which HV_BUS The servo wire holes S_IN1 thru S_IN6 LV_BATT are too small for the 22 gauge stranded wires to easily fit in Also putting the wires straight in like that may lead to early stress breaking The ground plane vias near U40 and U60 should probably be filled in style instead of thermal relief style The HV battery connector should have reverse polarity protection in
30. Flight Test Il 04 02 2011 94 98 ARE III EII 98 5 2 RecommendationsandFutureWork 99 Electric Owl Final Report 3 CONTENTS 6 Acknowledgements 101 6 1 lechnical AdVISOIS oi caia ca fore A eke 101 6 2 lebt TESNO uod xot e os Eom ERS 102 6 3 PUNGING SOUICES us dee dci dae s Aa ASCE e 102 7 References 103 A User s and Safety Manual 107 A 1 light Test POSA _ u WA RR E Kex os x s 8 E 107 A 1 1 The Day Before 107 A 1 2 PackingChecklisti 108 A A HL 2 x Qos u rice 110 A 2 Software Dependenciesi 113 A 3 Programming the Circuit Boards 115 A 3 1 AVR Microcontrollers 115 A 3 2 GPC ARM Microcontroller 117 A 4 AssigningBoardiDsi 119 A 5 Hardware In the Loop Testing 121 A 6 Software Utilities 124 Tv 125 A 7 1 Stepi DataCollectioni 126 A 1 1 Accelerometerss 126 oh ae e eae eee EI 130 A 7 1 3 Gyroscopesi 132 A 1 4 Differential Pressure Sensor 137 A 7 2 Step2 Pre Processing 139 A 7 2 1 Accelerometer Magnetometer and Differential Pressure Data 139 A 2 2 GyroscopeData
31. Mars UAV would require significantly more complex control system tuned to the charac teristics of the final airframe to achieve high performance Such considerations were deemed outside the scope of the project 2 2 3 Sensor Redundancy The team also implemented sensor redundancy with the flight computer able to accept be tween an arbitrary number of sensor inputs from up to three modular sensor boards Scaling up to accept data from more sets of sensors is straightforward to do The software can handle situations in which data from one or more of the boards is absent and is also capable of iden tifying and rejecting wildly outlying data as might be produced by a faulty sensor Because of the way that this functionality has been implemented the sensor boards may be added and removed while the autopilot is active and the system will seamlessly transition to using the new configuration Electric Owl Final Report 19 CHAPTER 2 DESIGN STRATEGY 2 2 4 Potential for Expansion The system hardware was designed with the potential for further expansion in mind especially in the form of computer redundancy Specifically four flight computer boards can each master one of the four system buses allowing for a fault tolerant arrangement similar to that used on the Space Shuttle Electric Owl Final Report 20 3 Final Design 3 1 Electrical Hardware Radio Sensors Autopilot Computer Servo Control Quad Bus Back
32. PJEOG 095 d W L A8Su9S AH So ME L J l Auoo Aseyeg ebeyo UD LO Sh 60 EN d Peony 1 00 AV Lo Sin F Yo KO ALS 9e V0 INE SEC pru cry Lv nw An xD a KUMOPINUS AH Poyo OvO AGE 0191 UA a Live AH Jjnee L 1 09 50d stor T ova u l QNO 440 NO 4u004 JnoL z Hn9s evo OvO L 9 0r1 9 92W1 OLO O AUOL eve pro g 150099 UIA FS I z l A Ve mo ER ON L BEqAH NEL OA S 0 AG0 Z SEH B t 21 89792WN1 Si iA L SnqAH OrH poU Ce 8v9 z ano z l a ar ien noho gt PERS AH em EIDA 1 99 8 L 9 S n z L 161 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 8 Jo S abed EQ UoISIA 1 SJEMPIEY pipoq omas JO 9I euJleuos HOI 6 g aunbl4 6 8 L 9 S e L II Uewyo01g 14900H A8 NMVHG 30 S0 39vd NOISIA3H ald zo uoisJoA peog oues H I Jo1oAu02 Asayeg abeo moj n9eezvdo Ln y L A8Su8S A1 S Bs Co au 9 96L0 59 96L0 4081 d 4 854 Sed HeqA1 GLO O 3u0L ML 0S7 ani vau sar SGH ISH JI 1 GP g Dee dugg Aug gen 954 T Ce eso zen mM S ONDA ONE a I Al anzz Ak vue 9
33. Potential for Expansion 3 Final Design 3 1 ectrical Hardware oon 3 1 1 Backplane 3 1 2 Servo Board 3 1 3 RadioBoardi 3 1 4 SensorsBoardi 3 1 5 General Purpose Computer GPC Board 3 2 Avionics Firmware 2 s EE ee ah 3 2 2 Bus Firmware 3 2 8 ServoBoard 3 24 HRadioBoard a a a s ea ns s qa nn ns n a ena b a 3 25 SensorsBoardJ 3 2 6 GPC Board AVR 327 GPC Board ARM 3 2 7 1 System Master 3 2 2 Custom Real Time Kernel 3 2 3 Autopilotlask 3 3 AutopilotSoftware 3 3 1 General Structure Electric Owl Final Report CONTENTS 3 3 2 Sensor Redundancy Management 49 3 3 3 Flight PlanFormati 50 3 4 Houston GroundSoftware 52 Ou does RR E Ee E Ee A 53 3 4 2 RasterData 54 3 4 3 VectorData 55 344 UAVSupporti 56 3 4 5 LoggingFormati 57 3 5 Communications Protocols 58 aoo BUS s s os
34. RS 485 transceiver cable to the bus that the GPC will use to issue it packet requests Connect the other end of the USB cable to an available USB port on the PC that will run the ground software Be sure to note its assigned device node 2 If X Plane is to be run on a computer different from the ground software connect the ethernet ports of the computers together with an ethernet cable Use the computers network configuration utilities to set up an ad hoc wired network between them Take note of the IPv4 address assigned to each NB If no network cable is available a wireless ad hoc network can also be used 3 Start up Houston on the PC that will run the ground software From the UAV menu select I O Configuration When the I O Configuration dialog appears select the Net work tab In the Local IP field enter the IPv4 address of the computer running the ground software More precisely if the computer running the ground software is also the computer that will run X Plane set this field to 127 0 0 1 otherwise set it to the address Electric Owl Final Report 122 APPENDIX A USER S AND SAFETY MANUAL assigned to the network interface on the computer running the ground software that is connected to the computer that will run X Plane 4 Set the the local IP port number to 38000 5 In the X Plane IP field enter the IP address of the computer running X Plane Again if this is the same as
35. a AA A WA RUNG UR DR 58 3 5 2 Radio Downlink Protocol 66 3 5 3 Radio Uplink Protocol 71 I 74 AR se s ke ek be oe GS e Bae ee aed Pace eed bas 74 pF Eum 76 363 AGCGIUaIOrS lt lt lt lt ob unde mox de eee oe Red E x Rue YA x 78 3 6 4 AvionicsMountingi 78 3 65 Non Integrated Sensorsi 79 3 7 FutureEkpansioni 79 3 8 Errata and RevisionHistory 81 3 81 HardwareRevisioni 81 3 82 Hardware Revision ll 0 o o 82 3 8 3 Hardware Revision It 84 85 4 1 Basic Functionality Testing 85 4 1 1 ectrical Testing 85 4 1 2 Software Testing ee 85 4 1 3 Sensor Redundancy Testing 86 4 2 SensorsCalibrationj 86 4 3 Hardware in the Loop HITL Simulation 89 4 4 Fl ghtlesis A Te E ei EO Rn n 90 4 4 1 Servo Board Flight Test 08 22 2010 90 4 4 2 Three Board Flight Test 01 07 2011 91 4 4 3 Initial Autopilot Flight Test 03 06 2011 92 4 4 4 Basic Autopilot Flight Test 03 19 2011 93 4 4 5 Redundant Sensors Flight Test 1 03 27 11 94 4 4 6 Redundant Sensors
36. a simple primary plus backup redundancy scheme as opposed to multi way redundancy appears a reasonable solution because communications failures are easily detectable and the power required for sending transmissions to Earth is large 2 1 3 Flight State Sensors In order to function the UAV s autopilot must be capable of measuring the state of the air craft An inertial navigation system INS can be supplemented with barometric laser or radar altimeters for above ground level measurement and pitot tubes to detect relative air speed Each sensor plays an important role in determining the flight state of the aircraft and to pre vent mission failure should be duplicated 2 1 4 Flight Computer NASA s unmanned probes typically sport at least a full backup computer In at least once case 5 this has prevented a computer error from prematurely terminating a mission however the use of dual redundant systems severely limits the opportunities for automatic error correction In contrast The Space Shuttle employs four redundant flight computers which simulta neously execute identical programs 9 along with a fifth computer executing independently developed code to mitigate the risk of mission failure due to software errors lf one computer suffers an error its output will disagree with that of the other flight control computers The sys tem can take a majority vote and disable the failed system automatically With four computers a
37. a single complete downlink packet structured according to the radio downlink protocol see section 8 5 2 There are three packet types for processing packets received by the radio from the ground computer When the GPC is ready to handle an uplinked packet it sends a BCMD_MAILBOX_PEEK command to the radio board The data field for packets of this type is empty The radio then replies with a BCMD_MAILBOX_CONTENTS packet The data field of this packet begins with the mailbox sequence number byte which is immediately followed by an uplink packet as specified by the uplink protocol see section 3 5 3 If there are no uplink packets waiting Electric Owl Final Report 62 CHAPTER 3 FINAL DESIGN the sequence number field in the data section of the BCMD_MAILBOX_CONTENTS reply packet will have the value 0x00 and no uplink packet data will follow it If the GPC receives the BCMD_MAILBOX_CONTENTS packet correctly it can then send a BCMD_MAILBOX_POP command to remove the uplink packet from the mailbox queue The data field of the BCMD_MAILBOX_POP command is one byte in size and consists only of the sequence number of the packet to re move For more information on the radio mailboxing system see section Sensors Board Commands There are four packet types associated with the retrieval of data from the sensors board The BCMD_SENSORS_FETCH_HIRATE packet type is sent by the GPC to the sensors board to retrieve high rate sensor data such as IMU
38. and medium screwdrivers of both Phillips and flathead variety as well as a complete hex wrench set are used for a variety of tasks A specialized prop boring tool is necessary for modifying propellers to fit on the drive shaft of the electric motor correctly Electric Owl Final Report 208 APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS C 3 2 Software Development Qty Part Mfr Description 3 ATAVRISP2 Atmel AVR INSystem mkll Programming Kit 2 PGM 07834 Sparkfun JTAG USB OCD Programmer Debugger for ARM processors 1 DEV 00774 Sparkfun Atmel ARM SAM7 256 Development Board 3 custom custom Shore Power Supply made from standard 12V 800mA wall supply 3 BOB 09822 Sparkfun USB to RS 485 Converter Table C 7 List of development tools C 3 3 Testing Supplies Qty Part Mfr Description 1 213046 SkyRC Charger iC6 LiPo NiCd Battery Charger 1 102989 Saitek Cyborg EVO PC USB Joystick 1 58318 Hitec Hitec R C Transmitter to USB interface 3 std various 6 plug power strip 2 177 Fluke Digital Multimeter 2 std various Extra Sharp multimeter Probes Table C 8 List of development tools Electric Owl Final Report 209 D Budget D 1 Revenue The team was allocated 2 500 from the Rice Electrical and Computer Engineering depart ment and 2 025 from the Texas Space Grant Consortium for project development work dur ing the 2010 2011 school year Development work over the sum
39. apeay ajew a Bue zyn uo z Uldgxz HV 229 0L2196 NE fez osna v uonduoseq Med JUN JUN s pj y O 0 Ae p1eog oipeu JO speuerey JO III p O lqeL 0 UOISIAS pjeog oipeH Ezo 198 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS ANS ATOd 19373 A91 ANGE dvd DO9JINOGEVEVO9LWXAW V uoO luu 8uO uoddiN YLO ANS Hf1001 HMd GTSIHS HOLONGNI Y LOL pZYa SO UOIIOD 071 I1 ZLGOS ADE VIL AMLLOHOS 30010 3 MV10 L9 ou s polq 0 0 S080 HZX OIINVH3O AOS 4400001 dVO 01886H Xu 8 08000 oabe ezo 4 S080 HZX ASZ 9601 3010 t INH3O dVO VZ1VMV0LO S080 XAV eo t 9031 HZX OIINVH3O ASZ 200 L dvO N LOVHEASOLDIOZLD EEN ECH E 91088 NGd S VINOOS A MS DAH Ol E INYL9ZINT euoneN OZN QNS ATOd 193 3 AOL 4N9S dvd DO9JNO9SVEVOOLOXAW uoO luu8uO uoddIN v90 AWS vg HN8L H3MOd HOLINANI 8LLLZZVVZ YN 091 ZLGOS ADE VIL AMLLOHOS 30010 3 MV10 9 ou s polq 090 S080 HZX OIINVH3O AOS 4d00001 dvd N LOVESAE0LIG0809 EEN 90 S080 HSX ASZ 310 L YAO dVO 1 9MSOLP SZ LZMIN L uepna o rep 299 9031 HZX OIINVH3O ASZ 30 l dvO f11LOVH 3S01990219 EEN 199099 c dOSd8 AS VI MONE HOLIMS 93H OI g8dON 0 S 3HINSZ922W1 euoneN 090 ANS S080 M8 L WHO A0 0Z SAY e0024dZ30L1HON wyoy 9eH reH zeH O H v ANS S080 M8 L WHO M0 OI S3H 200LJdZ30LHON wyoy 1 u seu eeH IeH y uonduoseq Med JUN JUN sopjeg O 0 Ae p1eog OIpey 10 speuerey JO lla p O lqeL 199 Electric Owl Final Report
40. bus 0 and the other into the data capture bus defined in step 2 Be sure to note the device node assigned to each transceiver For convenience it will be assumed for the remainder of this procedure that the transceiver connected to bus 0 has device node dev ttyUSBO and that the one connected to the data capture bus is on dev ttyUSB1 9 Open up a minicom serial console on bus 0 minicom D dev ttyUSBO Set the serial speed to 921600 bps This console will be used to signal the sensors board when it is time for it to capture data 10 Capture of the data will be done using using the busmonitor program If necessary build it by issuing the command make build pc busmonitor in the software majortom directory Electric Owl Final Report 128 APPENDIX A USER S AND SAFETY MANUAL 11 Enter the software majortom build pc directory and set the busmonitor program to begin listening on the data capture bus and saving any packets to an output file For example busmonitor dev ttyUSB1 921600 gt caldata dat will monitor the bus connected to the RS 485 transceiver with device node dev ttyUSB1 and will save all data to a file named caldata dat 12 Position the sensors board in the desired orientation for measurement by rotating the board assembly Calibration requires data from six different orientations three with each principal axis aligned parallel to the direction of gravity and three with each principal a
41. complete To get around this problem the sensors board performs sixteen dummy conversions in between states of the analog sensors state machine to flush the ADCs before beginning the conversions used to read the sensors I2C Sensors Interface Two of the sensors on the sensors board communicate using the 12C protocol the HMC5843 magnetometer chip from Honeywell and the Bosch BMP085 static pressure and temperature sensor see section 8 1 4 The sensors board uses the AVR s built in 12C interface capabilities to manage the low level aspects of communicating with these sensors The I2C bus on the sensors board runs at a rate of 100 kHz The I2C sequence begins with several initialization transactions carried out upon boot that set the gain and update rates of the magnetometers and read calibration values from the BMP085 Then the 12C system enters a cycle of transactions that repeatedly read values from each of the 12C sensors The firmware for querying the 12C sensors is built around two software state machines a high level state machine that dictates the order in which the different sensors are read and a low level state machine that manages the sending and receiving of individual bytes over the I2C bus When the DC system is ready to handle the next transaction e process the next state in the high level state machine the low level state machine is set to an idle state This condition is detected when the state of the 12C system is next p
42. decade counter is pulled high and held there for an amount of time equal to the desired pulse duration When pulse length is reached the decade counter is advanced and the system proceeds to the next servo output The system cycles through setting outputs to the different servos by stepping through the states of the decade counter Because this procedure requires precise timing to ensure that the control pulses last ex actly as long as they need to one of the AVR s built in timer counter units is used to measure the amount of time to be taken between steps of the decade counter When the decade counter is stepped and a new control pulse begins the timer is set with a period equal to the pulse duration and begins counting When the timer expires an interrupt is triggered that steps the decade counter to the next servo in the cycle and resets the timer period to the duration of the next servo s pulse The interrupt routine is written to take as few cycles as possible so that the Electric Owl Final Report 34 CHAPTER 3 FINAL DESIGN servo board can return to polling in the main event loop as quickly as possible The use of interrupts introduces one additional minor complication in the servo firmware operations that are not atomic must be protected by disabling interrupts before beginning them and reenabling them after they are complete In particular since the AVR is an 8 bit microcon troller this includes any operation that reads a
43. differential pressure sensor used for measuring the plane s indicated airspeed the team connected one of the pitot tubes that had been purchased for use with airsoeed measurement to the sensor s input ports and mounted the tube inside a wind tunnel Several pressure measurements were taken with the wind tunnel set to produce airstreams with a variety of flow rates between 10 and 30 mph At the same time the team recorded the readings of the wind tunnel s own pitot static pressure measurement system and used these to compute a linear model for the behavior of the pressure sensor 4 3 Hardware in the Loop HITL Simulation To enable ground development and testing of the autopilot algorithm the team created a hardware in the loop HITL test framework centered around the commercially available flight simulator X Plane 21 The term hardware in the loop refers to the fact that the autopilot algorithm is running on the actual GPC hardware during the test as opposed to a software in the loop test in which the algorithm would be running inside a software emulator for the GPC ARM To perform HITL testing the only change to the firmware that must be made is that the GPC board must be programmed to handle sensor data from X Plane instead of from a sensors board During each pass of the main system loop the GPC requests data from X Plane by sending a BCMD_SENSORS_FETCH_AHPRS request packet out on the system bus see section 8 5 1 This is pic
44. flight test the team collected a full stream of telemetry data and used this to gauge the autopilot s performance and find ways to improve it for the next test Electric Owl Final Report 93 CHAPTER 4 TESTING AND RESULTS 4 4 5 Redundant Sensors Flight Test I 03 27 11 The goal of this flight test was the same as the previous one to demonstrate basic functionality of the autopilot in the form of the ability of the plane to maintain a fixed heading however this flight test also added the extra element of sensor redundancy By the time of this flight test the team had constructed two additional copies of the sensors board calibrated them and had written the sensor redundancy management code for the GPC This flight test would try out these new features in a real flight environment As with the previous two flight tests the team had one of the experienced pilots at Dick Scobee Field take the plane off under manual control While the pilot was in the process of bringing the plane up to altitude the plane suddenly began performing a series of successive rapid vertical loops all under manual control Despite the pilot s best efforts to bring the aircraft out of this pattern the plane continued to perform loops for just under two minutes before crashing into a tree Thankfully the damage to the airframe was minimal A post mortem analysis of the teleme try gathered during the flight which included the commands the plane was send
45. has a nasty tendency to stall while climbing if the carburetor is incorrectly adjusted the procedure for avoiding this is to hold the plane straight up in the air and apply full power to check for proper operation Electric Owl Final Report 77 CHAPTER 3 FINAL DESIGN 3 6 3 Actuators The plane has four flight controls ailerons to control roll rate elevators to adjust angle of attack throttle for climb rate and rudder for ground steering and to compensate for the adverse yaw effect caused by the ailerons The current prototype has a separate servo for each aileron they are wired together to form a single PCM channel for control Throttle control is provided by the motor controller as described earlier The rudder is controlled by a single servo while the elevator is split into two independent sections each connected to its own servo Like the aileron servos the two elevator servos are wired together to form a single PCM channel All of the servos are of the same standard model the Hitec HS 322HD The servos are connected to the appropriate flight control surface with control rods The control rods for the ailerons are metal with plastic clevises connecting them to plastic con trol horns on both ends Small sections of fuel tubing have been used to secure the plastic clevises The elevator control rods are carbon fiber while the rudder control rod has been replaced with steel to prevent flutter Both elevator and rudder control r
46. is copied into a radio packet construction buffer XTend protocol headers and frame delimiters are processed and stripped as they arrive and XTend escape bytes are unescaped before being added to the buffer Computation of the XTend protocol checksum is advanced as each byte arrives When a complete packet is received its XTend checksum is verified and if the checksum passes the packet is assigned a mailbox sequence number and is placed in the uplink packet mailbox queue see Uplink Packet Mailboxing below Transmission to the XTend radio is also handled in the main event loop When a packet is ready to be sent to the radio the AVR adds it to a radio packet transmit queue In the event loop the AVR checks to see if the radio transmit queue is nonempty If it is and if no packet is currently being sent to the radio the AVR takes a packet from the radio transmit queue and sends a byte byte It polls in the event loop waiting for the byte to finish sending and then transmits the next and so on until the entire packet is sent Uplink Packet Mailboxing As uplink packets are received they are stored in the uplink mailboxing queue where they await retrieval by the GPC When the radio board receives a BCMD RADIO MAILBOX DEER request from the GPC it copies the contents of the packet at the front of the queue i e the oldest uplink packet in the mailbox into a bus packet and then sends this bus packet to the GPC Each uplink packet is
47. j 8 p 9 S n z L unsny d Auoujuy Ag NMYYG 30 G0 39vd NOISIA3H END quiu 20 UOISJOA pJeog Od5 eoeyelu PIED qs ALV ALV ALV Jy Sau vsu esy eau uA LH gt LO gt EdM E c L MOdS WHV N gt EOSIW WHY An Zt elvd Ka C C lt LISOW WHY L 0SOdN mlo lili jojo ONIN A OWW d e S xr OSU 1 92 183 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 6 yO 9 eDed Zo UOISIASA SIEMPAEY pseOg Od JO JIJWAYOS UO LC anp 8 9 S ueuioJg H qOY A8 NMYYA NOISIA3H 30 90 39vd 3114 ZO UOISJOA pJeog OdH iddns 16wod Od A8 L FULL Pall N3 zL Wwog 1n0 A8 100A 199 N9 999 Ge HnZy 3 wre GIMS Wu l 1 Kal 09n KIOJA L 8409A A0 t 820rHHS 8 Z 9 184 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 6 Jo Z abed 20 UoISIA 1 aJempJey DipoQ Oc JO 9l euu u2os UO ze g anliy L S eDpug Aer A9 NMYYA NOISIA3H 30 40 39Vd ad 20 UOISJOA pJeog Od5 TUL iddns Jamog 21601 A
48. measurements Similarly the BCMD_SENSORS_FETCH_LORATE packet type is sent to retrieve low rate sensor data such as GPS positioning information The data fields for packets of these types are empty The sensors board replies to packets of type BCMD_SENSORS_FETCH_HIRATE with ones of type BCMD_SENSORS_REPLY_HIRATE The layout of the data field for these packets is given in table Sensor data values are stored in in the data section in little endian order The units of the values were chosen to match the input expectations of the autopilot algorithm see section and are scaled to preserve a reasonable number of significant digits while remaining within the confines of variables of integer type A BCMD_SENSORS_REPLY_LORATE packet is used to reply to a BCMD_SENSORS_FETCH_LORATE request Since low rate sensor data consists entirely of GPS data at this time the layout of the data field for a BCMD_SENSORS_REPLY_LORATE packet is identical to that for GPS data encoded in Garmin s proprietary binary format see section 3 1 4 For convenience this format is pre sented in table 3 6 but for more detail the user should consult the Garmin Device Interface Specification datasheet 1 The GPS data is stored in the packet in little endian order exactly as it comes out of the GPS Electric Owl Final Report 63 CHAPTER 3 FINAL DESIGN Field Type Name Description int16 accel z acceleration in cm s int16 accelY y acceleration in cm s in
49. mm mm S S mm mm mm mm mm mm zm mm mm 21 1l mm mmm we mm mm mm mm zm mm mm mm zm mm mm mm mm 24 General Purpose Computers Servo Control 222 4 e s arenes 5 I V i HX 3 3 4 4 Pi a AS 13 i a a 9 Pd aI i i a I 4 Four Buses lt gt gt E pps S AED ALE E 1 2 3 is 1112 H q 2 Nena Sensor Sets Radios The project Expansion this year required for Mars e e a g Figure 2 1 System block diagram of some of the features that might be needed for a Mars capable system 2 1 2 Radio Communication The current Mars rovers avoid high power radio requirements by relaying data to the orbit ing Mars Odyssey and Mars Global Surveyor which in turn transmit to NASA s Deep Space Network 8 Because the Martian atmosphere and dust on ground based solar panels signif icantly attenuate power from the Sun these satellites have a much larger power budget they can use for interplanetary communication A Mars UAV would also be able to make use of this infrastructure however if the link to Electric Owl Final Report 16 CHAPTER 2 DESIGN STRATEGY these satellites is lost even if the UAV remains airborne then the mission is effectively termi nated because it is unable to relay any gathered scientific data back to Earth Because of this redundancy in the radio links is a reasonable design criterion For this component
50. policy Federal Aviation Administration February 2007 Federal Register Document E7 2402 29 P L Walter The History of the Accelerometer 1920s 1996 January 2007 findarticles com p articles mi_qa4075 is_200701 ai_n18705234 pg_16 last checked 20090726 Electric Owl Final Report 104 REFERENCES 30 An Introduction to AC Propulsion s Split Phase Drives for Brushless Motors tech rep AC Propulsion 2003 31 R Miura M Maruyama M Suzuki H Tsuji M Oodo and Y Nishi Experiment of tele com broadcasting mission using a high altitude solar powered aerial vehicle Pathfinder Plus in The 5th International Symposium on Wireless Personal Multimedia Communica tions vol 2 pp 469 473 October 2002 32 AC Propulsion SoLong UAV Flies for 48 Hours on Sunlight Two Nights Aloft Opens New Era of Sustainable Flight press release AC Propulsion June 2005 33 SkySite Network amp SkySite Telemetry Services Overview tech rep Soace Data Cor poration December 2005 34 RAD750 MRQW 2002 tech rep BAE Systems December 2002 35 AeroVironment Online poll on where small unmanned aircraft systems can offer the greatest benefit outside the military July 2009 http www avinc com poll_ last checked 20090726 36 NASA Solar Aircraft Sets Altitude Record and Communications and Environmental Breakthroughs Expected press release NASA Dryden Flight Research Cente
51. power the complete avionics package see section 3 1 2 under real flight conditions The team was concerned that the high current draw from the plane s powerful electric motor might cause microcontroller resets which would necessitate a hardware revision with re designed power supplies Fortunately these were not observed and the system appeared to operate correctly 4 4 2 Three Board Flight Test 01 07 2011 Over the course of the Fall 2011 term and the winter recess the team worked on developing the bus protocol wrote the firmware for the radio board and wrote a first draft of the GPC firmware that was not based on the MAL kernel which was still being developed In particular the basic facilities for command uplink and telemetry downlink had been established The goal of the three board flight test was to try out these facilities and see what needed to be improved The test was dubbed the three board flight test is because the test involved three of the four types of circuit boards the GPC board the radio board and the servo board The GPC was programmed to retrieve bus and battery voltages and battery currents from the servo and radio boards and downlink them over the radio where they would be picked up by the ground software The team had also developed some code for flying the plane using a PC joystick and planned to use this to test the ability of the plane to receive uplinked commands Unfortunately the flight test ended too
52. prevents proper functionality but avoids Electric Owl Final Report 22 CHAPTER 3 FINAL DESIGN catastrophic failure Distinctive unconnected traces are used to indicate the proper orientation of the boards The bus physical layer uses the RS 458 standard which bears some similarity to the mil itary avionics data bus standard MIL STD 1553 RS 485 is a three wire bus with differential data and ground but specifies neither a cable nor a connector Integrated circuits such as the TI SN65HVD12 are commercially available for integrating this protocol with a variety of micro controllers and a variety of debugging terminals are available for interfacing with a desktop computer Hardware connection Up to eight boards are each physically attached to the backplane with four 3M 10 pin 2mm header connectors one to each of the electrical buses These connectors provide a redundant electrical link between the boards as well as a fairly stable mechanical linkage Although the newest revision of the other boards features mounting holes for a more rigid mechanical connection this has not proven to be a pressing requirement Indeed in one flight test that led to uncontrolled impact with terrain see section 4 4 2 the boards separated from the backplane without significant damage harmlessly bouncing off the grassy field rather than shattering External connections The complete backplane includes four RJ 45 jacks at each end that expose th
53. program by issuing Electric Owl Final Report 140 APPENDIX A USER S AND SAFETY MANUAL make build pc teldecode in the software majortom directory Change to the software majortom build pc direc tory and run the following commands teldecode lt gyro_axisi_pitch log grep gyro_axisi cut f 2 d caldata_gyro_rot1 dat teldecode lt gyro_axis2_roll log grep gyro_axis2 cut f 2 d caldata_gyro_rot2 dat teldecode lt gyro_axis3_roll log grep gyro_axis3 cut f 2 d caldata_gyro_rot3 dat teldecode lt gyro_stationary log grep gyro_axisi cut f 2 d N caldata_gyro_stat1 dat teldecode lt gyro_stationary log grep gyro_axis2 cut f 2 d caldata_gyro_stat2 dat teldecode lt gyro_stationary log grep gyro_axis3 cut f 2 d N caldata_gyro_stat3 dat This will save the rotational and stationary data for axis 1 to the files caldata_gyro_rot1 dat and caldata_gyro_stat1 dat respectively and similar for the other axes Take these output files and save them for use in the next step A 7 3 Step 3 Model Fitting and Analysis In this step models are fit to the calibration data but the model parameters are not prepared for loading into the EEPROM on the sensors board The user examines the quality of the computed models and decides if they are suitable for use or if another set of calibration data should be taken instead Electric Owl Final
54. the autopilot 3 3 3 Flight Plan Format The flight plan is formatted as a series of steps where each step contains all the information needed for its own execution Each step includes a criterion used to determine when it has been completed so the autopilot can switch to the next step In addition each step can optionally contain one or more error conditions If the criteria for an error condition is met the guidance component will skip the normal step increment and follow a pointer to an arbitrary step The user is responsible for writing a flight plan which includes alternate contingency steps to be used in case of an error condition in one of the normal steps The autopilot software currently supports five types of steps e Glide The motor powers off a slight down pitch is maintained and a given heading is maintained During flight testing extra code was written to grab the current heading when manual to automatic switchover occurred and use this heading for a glide step e Takeoff The motor is commanded to a tunable high throttle setting and the vehicle tries to travel straight down the centerline of the runway The tail wheel is used for steering on the ground while the ailerons attempt to maintain zero roll so the wingtips don t scrape the ground The takeoff continues until a given elevation is reached or fails to be reached e Waypoint The airplane attempts to fly toward a specified waypoint without regard for its
55. the build directory e 99 gcc arm elf multilib patch INSTALL txt do binutils do gcc e do newlib gcc_config_arm_t arm elf 3 Acquire the following standard source packages from the Internet and save them in the build directory e binutils 2 20 1 tar bz2 e Qcc core 4 4 4 tar bz2 e newlib 1 18 0 tar gz 4 Unpack each of these files in the build directory cd usr src build arm elf bunzip2 cd binutils 2 20 1 tar bz2 tar xv bunzip2 cd gcc core 4 4 4 tar bz2 tar xv gunzip cd newlib 1 18 0 tar gz tar xv Electric Owl Final Report 147 APPENDIX A USER S AND SAFETY MANUAL This will create the following directories e usr src build arm elf binutils 2 20 1 e usr src build arm elf gcc 4 4 4 e usr src build arm elf newlib 1 18 0 5 To keep everything clean and separated these builds for these packages will be per formed in separate directories Create them by running cd usr src build arm elf mkdir build binutils build gcc build newlib at the command prompt 6 Configure build and install the binutils package by running the following commands cd usr src build arm elf build binutils sh do binutils make PS A AA HF sudo make install It will take a while for the build to complete The last command will install programs into usr local bin and will also create the usr local arm elf directory and several subdirectories 7 The next step in the pro
56. the computer being used to run the ground software set this field to 127 0 0 1 Otherwise enter the IP assigned to the network interface on the computer running X Plane that is connected to the computer running the ground software 6 Set the X Plane IP port number 49000 7 If the computer hosing X Plane runs on a different computer architecture from the com puter running the ground software check the Endian box if the endianness of the ar chitectures are different In particular if the computer running the ground software is running on an x86 platform and the machine running X Plane is a Mac this box must be checked to prevent X Plane from crashing 8 Fill in the RS485 bus field with the device node of the RS 485 transceiver that will be used to receive packets from the GPC Set the serial rate to 921600 9 Click the Apply button and close out of the I O Configuration dialog 10 Start up X Plane Set X Plane to listen for UDP packets on the correct IP Select the airframe model and world location to be be used for the test 11 Set the ground software to operate in HITL testing mode by selecting Hardware in the Loop from the UAV menu 12 When everything else is ready select Activate from the UAV menu to begin the HITL test Electric Owl Final Report 123 APPENDIX A USER S AND SAFETY MANUAL A 6 Software Utilities This section describes some of the PC uti
57. the form of either a crowbar diode and fuse crowbar zener diode and fuse or forward bias Schottky diode Current sense outputs have no low pass filtering Electric Owl Final Report 81 CHAPTER 3 FINAL DESIGN e There is no good reason not to add more bypass capacitors to the input of U21 and the outputs of U21 and U22 e To increase safety a different connector should be used for HV_BATT which has more physical spacing between the pins e Board fails to power up with just the HV battery This problem only manifests if you try to transition from fully off no LV battery no external power on buses 0 3 to connecting the HV battery input The HV_Shutdown line is held low by the Vcc static protection diodes on the ATxmega32A4 As a workaround cut the HV_Shutdown trace between the XMEGA and the LM2676S 12 not yet tested In the future this straight wire will be replaced with a MOSFET and a gate pull down resistor e LED missing 3 8 2 Hardware Revision Il The second revision of the hardware reduced the height of all of the boards to ease fitting them into the aircraft All of these boards were built and tested An improper option in one of the software packages resulted in several mis labelings of components on the silkscreen It was discovered that the yaw gyro on the sensor board was ordered incorrectly and the desired part was no longer available which required the creation of the third revision The remainder
58. the trajectory plot shows that barring an initial transient the plane successfully maintained its heading over an extended distance with some mild oscillations Having accomplished the main objective the team decided to try a third flight test this time with the autopilot programmed to maintain a fixed horizontal path like it had been during the flight test on March 6 The hope was that the improvements that had been made to the autopilot over the weeks since the March 6 test might have fixed the problems the team had observed then Unfortunately the autopilot showed similar oscillatory behavior In the weeks since this flight test the team has conducted extensive tuning of the autopilot using HITL simulation in an attempt to improve this behavior and hopes to try out the modifications along with a fully waypointed version of the autopilot which has also been verified to operate correctly in HITL simulation see section 4 3 in another flight test soon Electric Owl Final Report 96 CHAPTER 4 TESTING AND RESULTS Figure 4 2 Plot of plane s trajectory during the second flight test on 04 02 2011 The red lines indicate parts during which the autopilot was active Arrows on the line segment indicate the plane s direction of travel Electric Owl Final Report 97 5 Summary and Recommendations 5 1 Summary The team successfully designed and fabricated a complete set of avionics hardware for a fixed wing UAV from sc
59. to safely discharge 175 amps which is well in excess of what the three phase motor can draw The charger listed in Section C 3 3Jis capable of safely charging the main battery The backup battery in the aircraft and the R C transmitter use Nickel Cadmium batteries The charger in Section C 3 3 will also charge the backup battery safely when configured prop erly A 10 2 R C Flying There are many hazards involved in R C flying Following established R C flight regulations as documented in the AMA safety code 41 can reduce the risk of injury and mishap during flight operations When in an active configuration the propeller poses a potential hazard If the R C trans mitter is not turned on when the aircraft is powered it may start in an undefined state Before activating the motor controller ensure that the R C transmitter is on Additionally metal bladed propellers may not be used according to regulations R C flying should only be performed in safe areas where there is minimal risk to others and to property Team Electric Owl recommends designated R C fields such as Dick Scobee Field in George Bush Park in west Houston Electric Owl Final Report 151 APPENDIX A USER S AND SAFETY MANUAL A 10 3 Construction Standard precautions should be taken when handling Cyanoacrylate based adhesives in air frame construction as these can adhere to flesh Additionally soldering components to the boards provides a potential so
60. uses a similar radio from the same vendor that connects to Electric Owl Final Report 25 CHAPTER 3 FINAL DESIGN the computer with a USB cable Bus Voltage Monitoring Aside from the radio module the radio board also features hard ware for monitoring the voltages of each of the four system buses This consists of a set of simple voltage dividers connected between each bus and ground together with some capac itors for filtering out oscillations in the voltage due to traffic traveling on the bus The center points of each voltage divider are connected to ADC pins on the radio board s AVR for reading 3 1 4 Sensors Board The sensors board gives the avionics system the ability to determine flight state The sensors mounted on the board are capable of measuring the following aircraft states 1 Relative airspeed 2 Three axis acceleration 3 Three axis rotation 4 Three axis magnetic direction 5 Absolute air pressure External connections allow the sensors board to interface with a serial GPS unit and allow expansion to include an ultrasonic altimeter and motor telemetry input A front assembly diagram of the sensors board is shown in Figure C 4 with the relevant parts enumerated in Table C 5 Analog Sensors A three axis analog MEMS accelerometer the ADXL335 from Analog De vices is used to provide acceleration measurements These are numerically integrated to es timate absolute velocity in all three axes The raw anal
61. 0 SAd az Aoza lu li OL ss1v100 vaa z 1 FXL VIVO ETOS ECH e vd OGv 0ax1 G090 dd Fez gt F Xeng x0L Gen Zoe gt a goqv oqxu o0oo zaa lt Fxtdesng vas ie Loi L gt sva soqv oxox 8000 iaa yg L 2 bsLesnd 1 99 a F d33dStlV d gt va roay vooo vaa lt 1 FXL YVNOS P LAOD Leva eoaw la E la m sn AXOJ D Lwa zoav Lovd LLOaY tad 777 N anol 9 9 9 9 SUOO EXOMO gt iva oov oovaroroav zaa y L Zle09V 629 ON NGHS ezo aed g I woo oy OVd 434v 090v 6oav ar lt L Al899V moa 29999171 un z 3u001 SS exe AZ len es 33uv eoav 08d y xleo v LAGS L 99AV sn pyzeebowx y Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 8 Jo aBed EO UOISIAJI BIEMPJEY pipoq sJosues JO 9rjeuleuos ynon Deg anb 8 9 S v e ueunpoJg 14900H A8 NMVHG 30 0 39Wd NOISIA3H END JILL CO UOISIJA p eog SIOSUeS S eyed Jv 3u001 0 Sey 33 33 sse ppy OZI ZED e ON dada ey Can AUOOL Ano SE 91198 vaan veas LEO ogo 1 t vas 903 P z mis e HIN aNd FAV 0 pey 0 n 4u001 MZ zen SEO FM X0L eed Zed LAG SE 99 EAV lao 4u001 no L
62. 0 S3H H 0 91 l HOINH ejodxyoeis LEY 9EH c Gey AWS S080 M8 L WHO SO Ap SAY c0 vJdZ3OLHON wyoy veu SEH LEH OSH S AWXIs veo AWS S080 M8 L WHO A0 0L SAY 2004244230 LH wyoy 8 H c 1OS MOT A00 HOSIAYAdNS 2I LL I00 LO LdOIN diyo LEN H AWS 080 N33H9 MOTT3A 031 YL HZLELAd 099110913 ajue s oed CWS S080 M8 L WHO 0Zv S3H 007vJdZ30LHON wyoy EECH S080 HZX 0 AOS 4400001 H3O AVI GLOVMEOLHLZHOLZINHO ereny 30 S080 dIHO WHAD A0S 4d0001 dVO QN LONS20LOOd 093 9luoseued de9 AWS S080 26 L M8 L WHO MOS I SAY LOS LHdZ30LHOIN wyoy 6 H AWXI4 629869 c 1 Azq ANS dd 81 ZHW Z v 81 IVLSAYO 8L ZHINZEV 81 D8NQV uooeJqy eX 9 9 GED VED 090 HZX A9L 9601 4NF INH3O AVI V 1V3F0 LOAS090 uogeJ10d10 XAY EEO ZED IED OED A uonduoseq Med JUN JUN sopjeu O c0 eH peog Od JO S EUSIE N JO 118 9 D 9Iaer 205 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS ANS HN00 HMd GTSIHS HOLONGNI Y LOL pZYa SO UOIIOD 071 I1 ZLGOS ADE VL AMLLOHOS 30010 3 NV 10818 ou s polq 0 0 S080 HZX OIINVH3O AOS 4d00001 dVO 01886H Xu9 08000 oabe O 1 S080 HZX ASZ 9601 4N0 t INH3O dVO VZ1VMVY0LO S080 XAV e k 9031 HZX OIINVH3O ASZ 40 L dvO N LOVHEASOLDIOZLD EEN 14ZO D O v 91088 NGd S VINOOS A MS DAH Ol INVL92W1 euoneN 0 0 1 9031 0Z HSX AOL 4NOL HAD dVO IN90L VIHSX9L2 O yal 199 9031 9601 HZX A9L ANZ HAO AVI MSLVOLYZX9IZEO yal 099 820v WSZ 0 H
63. 1 00X1 0090 3d ec gt kel he D Lu Lsng Lixyesng F 99AV L99A HAV KOSA gt 904 OSINW LOX8 0ax4 9090 zada kupasi lt et S9d ISOW LMOX 8L9O 195 049X 8090 I3d es gt buaxtesna 70d SS V190 vas v02o 03d gz maoni gr 0d oqxi qooo Fxu0sng gt 1zo4 0ax4 2090 MOS L OX lad gg 2 F2Gd kupona lt Tp Od 198 049X 8090 osiwiqxu ai gt F9dd EIOS Wav or 094 vas v090 sowhiowatoo Sad sz lt gt FSQd Gad 0 9cH ELSOdN _ ioo tee JE LISON WHY cM ve 0 Scu g Zvd OGv 0ax1 G090 dd Fez gt Xing z 9vd eoav 00x4 9090 zaa 1 EXuesna gt FIn wav sva soav oxox 8000 iaa yg L 2 F uaXLesng L ZOd O vey bp bd voav 090 0dd oz LMOdS Wuv vy Pd voav v020 0dd Foz 0 Edy ey vd coay P red peu OLY FISH Wav lt gt wa zoqv Lovd L LOGY dd 7 Voge Lu I ELOXL WHV Tr iva Loav oova oroav zad 0 cc 190d a oy ovd 438v 000V 60av rad EOSIN WHY 0 LZH LI 33uv eoav 08d y sn pyzeebowx y 8 9 S y z L 180 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 6 JO e Bed Zo UoISIA 1 aJempJey pleoq Oc JO Ji wayos PNN gz g eJn6rJ
64. 16 bit value from memory Servo Inputs From GPC Autopilot The servo board accepts input values from the GPC board running the autopilot via bus packets of the type BCMD_SERVO_SETSERVOS These pack ets contain values that are used in setting the period of the output pulse width control timer for each servo see Servo Outputs above The servo board will use values sent to it over the bus to control the servos unless it is also receiving commands from a manual RC transmitter which are given priority see Servo Inputs From RC Transmitter below In the future this facility may be enlarged to accept commands from multiple GPC boards connected in a redundant configuration The servo firmware would be expanded to arbitrate between the different sets of received values and use them to determine the final set of servo outputs Servo Inputs From RC Transmitter The servo board is also capable of accepting com mands from a standard six channel hobbyist RC transmitter for manual backup control The inputs from the receiver come in as servo control pulses The servo firmware uses AVR s timer counter units and AIXMEGA32A4 compare and capture events to precisely time the du rations of these pulses which are then stored in memory to be used to set the period of the pulse width control timer for each servo see Servo Outputs above More precisely a rise in the voltage on one of the lines for the RC input channels triggers a timer ca
65. 189 Jno wo 188 ol i 882 1 a nro llega 2 tf t npo l logo ten 2 2XVMW LIDA e il EAS NNOO HVNOS E GE OE SSAPPY OZI gen Kg OONAG NI3S For i m anda dias 189 e 6 ego t9 ON KE x02 veu yi OLAS NB _ EH S adaa dddO ro EXL VLVQW 4 LA N N3HA ON rs x0L eau jnoL 4uo0ol 9 r8SOWH poli 80 SEET SE a Me 8 adAv d De re L 99AV EN mE z er Aqua dvds z ul EAS L EVaS lt gg vas EE ETOS NNOO LYC LOW osn 0 88H 0 v8u 8 z 9 S e L 178 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 6 JO aBed 20 UuoISIA 1 aJempJey pleoq Oc JO OIJeuayos 1in9JI 9z g ant L S eDpug Aer A9 NMYYA 30 LO 39vd 1 99 NOISIA3H END iH z gu a Aja CO UOISISA peog DDD Lxpesng ie al 4 ty 1 eoeyeju sng 9 ere Lomwgerg 30 8 U3xXJesng 3 SL s Exyesng lt Ar TI OF y esna cLOAHS9NS vn 1 99 ONS 99 g NV 9 L XLzsng pra a
66. 1984 18 Y Yeh Safety critical avionics for the 777 primary flight controls system in Digital Avion ics Systems 2001 DASC The 20th Conference vol 1 pp 1C2 1 1C2 11 vol 1 2001 19 T Coleman and Y Li An Interior Trust Region Approach for Nonlinear Minimization Subject to Bounds Siam Journal on Optimization vol 6 pp 418 445 1996 20 T Coleman and Y Li On the Convergence of Reflective Newton Methods for Large Scale Nonlinear Minimization Subject to Bounds Mathematical Programming vol 67 no 2 pp 189 224 1994 21 Laminar Research X Plane http www x plane com last checked 2011 05 05 22 R P G Collinson Introduction to Avionics Systems Kluwer Academic Publishers sec ond ed 2003 23 D McRuer Ashkenas and D Graham Aircraft dynamics and automatic control Prince ton University Press July 1990 24 C K Chui and G Chen Kalman filtering with real time applications Springer 2009 25 R Langton Stability and control of aircraft systems introduction to classical feedback control John Wiley and Sons Oct 2006 26 Code of Federal Regulations Title 47 Telecommunication Pt 0 19 Revised as of Octo ber 1 2009 Government Printing Office 2010 27 Model Aircraft Operating Standards Advisory Circular 91 57 Federal Aviation Adminis tration June 1981 28 Unmanned Aircraft Operations in the National Airspace System notice of
67. 2 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS CWS S080 L M8 L WHO A0 0Z SAY 2002344230 HOW WYOH vey 28H c CWS S080 L M8 L WHO M0 0L SAY 2001444230 HON WYOH 8H 18H c WAS SOd ACIS HZ H3QV3H NNOO NS 41 HZ dES 1sr NNOO HVNOS ININS SOd ACIS HZ H3QV3H NNOO NS 31 uz aes isr NNOO 1Vd LOW ANS 0Z A 9 INOL LNVL AVID Y8NI90LPOdOL wyoy G80 t89 2 689 S080 HZX 0 A91 ANL HAO dVO QLOVMTOLOLZH6LZINHO ejem 880 280 980 89 S OIOS 9L HAOU HAG INM ZEZESH Ol HGI32 2 XVIN IL en NIL WWE 3qIS SOd9 HS YIAVIH NNOO NS 41 81 SSuS g90NS 1sr NNOD Sd5 4 xond Sdd 19419991 SAD SVVM 9ANISUSS ON X81 SAD UIE preoqyo S080 HZX AOS ANZe HAO AVID 1 DAPZZL8ZLEMINN u pnA O ISL 289 OLZL 9602 HZX ASZ ANOL H3O AVI IN90L31HZXS22 O di 189 901 02 SIXV OILINOVIN HOSN3S r8SONH eMABUOH osn uonduoseq Med JUN JUN sopjeu O g0 AG pJeog sJosueg JO s eueje N JO llg CG eiqer 203 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS AWS 0Z A 9 INOL LNVL dvO H8W90LPOdOL wyoy O O HEO Z dJO 179 9S2 LIGZE NOW ZINHV Ol L00 v 9S2SZINVS L6 1V Jeu OEN OCH SZH CWS 090 MOL L WHO 0 0 S3H Y 0 91 l HOINH ejodxpeis PZH EZH ceu IZH 9 AWS S080 qati q31 YIL HZLELHS 09910913 ejueis oza CWS S080 L M8 L WHO 0Zv SAY 007vJdZ30LHON wyoy la I S080 HZX 9601 A9L 4NF 439 dVO GLOVMTOLOLZH6LZINHO ereny 12cO S
68. 20 2 CWS 448 ZHW 824 4 IVLSAYO L AYQ ZHIN824 7 28 18V uooeJqy IX dJO L vrt A9 L USBI AZE NOW HAV nv rveeeDeuix Iy pwy cnt 12181 319V113S38 OGAS VSZ L Old YdSZI 12181 esnjlenr ed 241404 f NVOE SOd Z STGNVH M dI LNNHS c SvSI88 oo L euou uonduoseq Med JUN JUN sopjeu AD 0 ed peog OAJAS 104 SJEN JO Hd CO AQEL 194 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS veel INH3 L v MZ WHO 200 S3H H3J200HS2MAT1 SHWYO OSH G EZLOS 96 HOLINOW LN3HHfO JI HASGIVS6LVNI LL sn 109 SOd 19S 1H3A H3QV3H NNOO yV v0p9 01 196 NE liva M L 2 LOS VWO002 ADS HO N LIASON VL8ELSSd X9 9Z SEPOlq ovo ANS S080 L M8 L WHO M0 OI S3H 2001 4dZ30LYON wyoy vod S080 HZX 960L A9L 4NF 439 dVO GLOVMTOLOLZH6LZINHO ereny 6vO 9vO ZVO 9031 INH3 L v Mei WHO LO SAY H3JO0LOHZ HANI SHWYO rH G EZLOS 96 HOLINOIN LN3HHfO JI HASGIVS6LVNI LL ev S080 9601 HZX AOL 310 L H3O AVI xS0LVIHZXZLOZO yal 9vO CWS S080 L M8 L WHO ALS SAY AE LGg3V9 vu3 093 oruoseueg cry CWS S080 M8 L WHO INL SAY AS0LG3V9 VH3 093 9oIuoseueg Wu OIOS8 ZHA00 H H d9 dINVdO JI NYEEZVdO LL lyn 1 CWS S080 S MOL L WHO AS0 Z SAY IN Q LS02 dOZZ L HH nunsns OrH QNS ATOd 19373 A91 ANGE dvd 2094IN06 VHVO9IVXdV uLoO luu 8uO uoddiN Gyo Hngg sJojonpu Jamog INO9S 0L2 LHHS sunog Orl SIqHMd A09 VE AM LLOHOS 30010 1 09 Sad Sul s polq ova S080 HZX OIINVH3O AOS 4d00001 dVO 01886H Xu9 08000 o
69. 6 B 34 GPC board revision 02 circuit schematic 9 9 187 C 1 Front assembly diagram for Backplane Rev 03 190 C 2 Front assembly diagram for Servo Board Rev03 191 C 3 Front assembly diagram for Radio Board Rev03 191 GA Front assembly diagram for Sensors Board Rev03 192 C 5 Front assembly diagram for GPC Board Rev0O2 192 Electric Owl Final Report 7 List of Tables 3 1 Microcontroller ADC pin assignments on Sensors Board Rev 03 28 204 E oe pie Saar oe a RUE E 59 AAA 61 oS E A EE NC NR RAE UN EE EE 62 DEE 64 Sor AE A AA 65 fig eae Bee See ee ae ee s 65 ere 66 IE 67 3 10 Telemetry channel types and corresponding marker Dies 68 3 10 Telemetry channel types and corresponding marker Dies 69 3 10 Telemetry channel types and corresponding marker Dies 70 n 73 peso ata 74 A 1 Software dependencies required for Electric Owl development 114 C 1 Bill of Materials for Test AlrfraMel 188 C 2 Bill of Materials for Backplane Rev 03 193 C 3 Bill of MaterialsforServoBoardRev03 193 C 3 Bill of Materials for Servo Board Rev0O3 194 C 3 Bill of MaterialsforServoBoardRev0O3 195 C 3 Bill of MaterialsforServoBoardRev0O3 196 C 3
70. 9 EEN 299 GO80 HSX ASZ 4NO L YAO dVO 1 9MS0LP 82 L2MIN L uepna o rep 199 uonduoseq Med HN JUN sopjeg O 0 ed peog OM 104 s euetey JO III CO AQEL 197 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS S080 HZX 0 A91 ANL HAO dVO GLOVMTOLOLZH6LZINHO ereny O 0 O Z 9 EZLOS 1191 ISNYYL TAT LIOA Ol HASGIOLOSXL LL len oBuey aw Or YNSdH ML 006 PuaLx W3O 006Dpu l X Did OEN CWS S080 M8 L WHO M00 S3H 00l4dZ50 HOW wyoy 8cH 9cu vzu ceH v AWS S080 M8 L WHO M08 9 SAY L0894dZ30LHOIN wyoy 1eud seu eeH IleH v aNs S080 qati q31 YIL HZLELHS 09910913 ajue s oza ANS S080 GL M8 L WHO 0Zv SAY 007vJdZ30LHON wyoy la I azo 929 Azo ve S080 HZX 0 L A9L 4NF 439 dVO GLOVMTOLOLZH6LZINHO ejem ZZO SZO vcO Szo 8 AWS 9602 A 9 ANOL LNVL dvd H8IN90LPOdO L wyoy 929229 7 S080 VW00l SWHOZ9Z dIHO 3118434 01 H2S2V9S08041 pureq IZI 1 S080 HNO YJAVIILINN YOLONGNI LWOO LAZ LOZZ TIN yal 071 AWS S080 M8 L WHO M0 0L SAY 2004244230 LH wyoy 0cH NIL 89d WNZ SOd9 143938 NNOO s0 vsae sae rL4d 9SOJIH Idd S080 OdN AOS S Adz INH3O AVI VZ 1WP0Z1WSS080 XAV 129029 2 QNS 4481 ZHIN 824 7 IVLSAYO L AYQ ZHIN824 7 28 18V uooeJqy IX E d401 pp A9 L USBI AZE NOW HAV nv rveeeDeuix y Jeu sn VV9LZ OG VI AO AM LLOHOS 20010 INOY1LSALS GIE va eded id v OIOS 8 AEE S8VSY H3AISOSNVUL Ol GZLGAHS9NS LL YAENZNIN v S080 HZX 960L AY 4NF 439 dVO GLOVMTOLOLZH6LZINHO ereny vVO O 70 p
71. 9 arem H T ABS EE ei g VS mo GGO H j 0S V3 doD AZL 1noA n oso 298 el g IA E live Aq HS 2U004 ange ESNngAT osa 0S1 osn ISO T e 4 1 00 S8 l 20070 i OSH i i zs as Lega GE y uA g z SO Z owo z 1 a ni seim inoj L 2 Hlesues Al zen 99A a 6 8 9 S E rd L 162 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 8 jo 9 9Bed EQ uosa aJempey pseog OAJAS JO DIJEWSYOS JINDID 01 g e1n6iJ 9 S eDpug Aer Ag NMYYA NOISIA3H 30 90 39vd ad 20 uoisJoA peog oues H iddns 160g OAJ9S AG 7 l E EE 1S e3 ep 9047 09q 149 63 48 e N any anot eee ES Q m 199 0904 L z mis 091 3uo1 O W0SI 09ZIHHS zg59 oo 19 922W1 uA d VE mo z 1 99ASNg B gd O 1no 9 AS A a oon AS O10 7 UA Z 9 S y z 163 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 8 jo 7 abed EQ uosa aJempey DipOQ OAJAS JO 9euleuos PNI pg NDI S eDpug Aer A9 NMYYA NOISIA3H 30 40 39Vd ad ZO UOISIJA peog oA19S iddns Jamog 21601 A TUIL HOT oza SEET a a u o a AUOOL Ant
72. A dsc H osna WOr1LSd1S E J La cLOAHS9NS LA 6 9 S z L 171 I Report ina F Electric Owl 8 Jo z abed EQ UOISIAJI BIEMPJEY pipoq sJosues JO 9rjeulieuos UDO 6L g anb APPENDIX B SCHEMATICS AND CAD DRAWINGS 172 8 L 9 S y z L eDpug Aeujer Ag NMYYA 30 20 39vd NOISIA3H qi qui 0 UOISJ8A peog SIOSUBS 49 0410090J9 A OL 02H I c doi Le E m ge 19 lag 13Sau LOSOL LIWLX Lud 7g ZHN 8c4E 7 XT dol Tio f T t e T z i ye VL VQ Idd 2OSO LZ1VLX 08d gg 029 20001 dnOL 3400 4U001 3U00L SNOL KIJA HAV Idd Z29 92O G ved 829 22d ar eebe i xLesng 1 J EE L i i E VA d A Zp 20d M9S LOX1 00X1 0090 3d ec gt E kel he D xy Lsng Lxyesng F 99AV L99A HAV KOSA gt ooa OSINW LOX8 0ax4 9090 zada 1 kupasi lt et S9d ISOW LbMOX 8L9O 195 049X 8090 I3d es gt buaxtesna pudxiosng lt PL P9d SS VLOO vas vooo oad gg FSdd Sd9 Fxiosng lt gt gr 0d oqxi qooo Fxu0sng L gt 1zo4 oaxw 9090 MOS LOXL Odd 7z gt FXH Sd9 F19S lt een 19d 19S 049X 4090 oSsiW Laxu 9d tam lt FXL Sd9 peu W vas lt gt pr 1008 vas v090 ISOW LMOX 8 19
73. ACH OxOE Motor tachometer Table 3 10 Telemetry channel types and corresponding marker bytes Electric Owl Final Report 68 CHAPTER 3 FINAL DESIGN Channel Byte Description CH_MOTOR_CURRENT OxOF Motor current draw CH_SERVO_OUTO 0x10 Servo output 0 Throttle CH_SERVO_OUT1 0x11 Servo output 1 Ailerons CH_SERVO_OUT2 0x12 Servo output 2 Elevator CH_SERVO_OUT3 0x13 Servo output 3 Rudder CH_SERVO_OUT4 0x14 Servo output 4 Manual Override CH SERVO OUT5 0x15 Servo output 5 CH BUSO VOLTAGE 0x16 Bus 0 voltage CH BUS VOLTAGE 0x17 Bus 1 voltage CH_BUS2_VOLTAGE 0x18 Bus 2 voltage CH_BUS3_VOLTAGE 0x19 Bus 3 voltage CH_TEMPERATURE Ox1A BMP085 temperature reading CH_RC_CHAN1 0x20 Received RC channel 1 CH_RC_CHAN2 0x21 Received RC channel 2 CH_RC_CHAN3 0x22 Received RC channel 3 CH_RC_CHAN4 0x23 Received RC channel 4 CH_RC_CHAN5 0x24 Received RC channel 5 CH_RC_CHAN6 0x23 Received RC channel 6 CH_BUS1ERRCNT 0x30 Bus 1 packet error count CH_BUS2ERRCNT Ox31 Bus 2 packet error count CH_BUS3ERRCNT 0x32 Bus 3 packet error count CH_BUS4ERRCNT 0x33 Bus 4 packet error count CH_ERR_SERVO_TELEM_NOREPLY 0x40 Servo data no reply counts CH_ERR_RADIO_TELEM_NOREPLY 0x41 Radio data no reply counts CH_ERR_RADIO_MAILBOX_NOREPLY 0x42 Radio mailbox no reply counts CH_ERR_SENSORS_HIRATE_NOREPLY 0x43 Sensors high rate data no reply counts CH_ERR_SENSORS_LORATE_NOREPLY 0x44 Sensors low rate data no reply counts CH_ERR_SENSORS_AHPRS_NOREPLY 0x45 AHPRS n
74. ACKET The board will send the radio downlink packet attached to the bus packet via the radio e BCMD_MAILBOX_PEEK The boad will reply with a BCMD_MAILBOX_CONTENTS packet con taining the contents of the uplink packet at the front of the uplink mailbox queue e BCMD_MAILBOX_POP The board will remove the uplink packet at the front of the uplink mailbox queue if the uplink packet s mailbox sequence number matches that sent in the pop request packet XTend Radio Module Interface In addition to interfacing to the system bus the radio board also communicates with the on board XTend radio module using a serial line The communi cations are structured according to the XTend API mode 2 protocol described in the XTend datasheet 15 which forms an additional protocol layer on top of the downlink see section and uplink see section 3 5 3 protocols Since the AVR only has four DMA controllers and since these are all allocated to handling bus communications see section 3 2 2 receiving from the XTend module is accomplished by polling the radio s assigned USART receive register for new bytes inside the main event loop Because the serial link to the radio runs at the relatively slow speed of 230400 bps compared Electric Owl Final Report 37 CHAPTER 3 FINAL DESIGN e g to the 921600 bps system bus the likelihood of the polling loop missing radio bytes is reasonably small When a new byte arrives from the radio it
75. AND CAD DRAWINGS 8Jo aBed EQ UoISIA 1 aJempJey pipoq sJosues JO 9rjeuieuos UDO g rg anb 6 Z 9 S z L eDpug Aer Ag NMYYA 30 LO 39vd 1 99 NOISIA3H END 4L suu aya om lg E P go UOISJ9A peog SIOSUSS T hsp SR eoeyeju sng 9 ere Lomwgerg 30 8 U3xXJesng SL e 3u z 6 Lixyesng lt Ar mes OL H esna cLOAHS9NS vn 1 99 i ONS 99 Pg og 9 L XLzsng pra az Z f 299 AZSN a V 9 1 99A3SNg lt 7 S Lux L sng d e 3u z 6 Ar iHe OF Exyzsng lt y zsng cLOAHS9NS en EI i e an9 99 g img 9 LxLLSng cf al z n el OALSNG H 30 E dic 8 Lux LLsng d gt e 3u z 6 i OF Gauteng A p H Isna cLOAHS9NS en EI uf i aNd 99 Pg S 9 INOyT1LSALS 1 00 A SNG _ S JN va Lx Losng por al Z D Z vis I 55A0sng tic A ae 1 09AZsng vO 9 ZO 10 ad C lt 8 JN eq Luz 10sng 3 d gt 2 z n n onp nu LA Mor1ESALS ioonisng js SM Xgosng IA p L 3909ASng s sa L 99
76. APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS HSNS dunssdHd OlHl3WOHVS8 VLIOIQ G80dWd uosog OEN AYAN XVIN IS Sri SYNSSAYd SNIS SV2OLZINXdlN 9 e959914 L dOSA 8N12O3Hd 45H OI 4d G 2 8SIWHEZS990111 Jeaury len aNs S080 qati 031 YI HZLELHS 09910913 ajue s oza ANS S080 L M8 L WHO 0Zv SAY 007vJdZ30LHON wyoy la I V2O 829 S080 HZX 960L A9L 4NF 439 AVI GLOVMTOLOLZH6LZINHO ejem 220 SZO beren 9 AWS 9602 A 9 ANOL LNVL dvd H8IN90LPOdO L wyoy 620 920 ZZO S080 VW00l SWHOZ9Z dIHO 31184834 01 H2S2V9S08041 pare Pet S080 HNO YAAVTILINN YHOLONGNI LINOOL37Z LOZZ TIN yal 071 AWS S080 M8 L WHO A0 0L SAY 20014dZ30LHON wyoy ced 12H OCH NIL 89d WNZ SOd9 143938 NNOO s0 wsaz sa9 1140 9SOJIH Idd S080 OdN AOS S Adz INH3O AVI VZ 1WP0Z1WSS080 XAV IZo OZO E AWS 4481 ZHIN 82262 IVLSAYO L AYQ ZHIN824 7 28 18V uooeJqy pc E dJO L vr A9 L USBI AZE NOW HAV nv rveeeDeuix Iy Jeu GSN 4 YY9LZ OQ VI A0 AM LLOHOS AGOIA WOV1LSdLS GIE va ea ea La OIOS 8 A S8FSH H3AISOSNVUL Ol GZLGAHS9NS LL yn en n In v S080 HZX 960L AY 4NF 439 AVI GLOVMTOLOLZH6LZINHO ereny YO 9 co io t esna apeay jew a Bue juu tuutuu0 z uldgxz HV 229 0L2196 We zsng sng osna uonduoseq Med JUN JUN sepjoy O g0 eH PIBOg SIOSUSS JO s eueje N JO 118 CG eiqer CO UOISIA9A p1BOg SIOSUIS G 200 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS DE 19
77. Ant HNO F o O zo LOFT 0403 elt T VA A 8 MSA z z KE o1 d 29 IO m UA 7 mie YWOO r 1no s 9m kosasnd AE InOA z z O O o I ozn ASL 9101 UA 164 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 8 jo g aBed EQ uosa aJempey preoq OAJAS JO OIJEWISYOS JINDID z pg NDI 8 S ueuooJg 1jeqod A8 NMYYA 30 90 39vd NOISIA3H END quiu ZO UOISJOA peog oA19S sjndu oues 402 01 il 88H KI z L L 9ul0A19S lt HAS H L 9NI S 402 01 il 68H 88H z ele L SuI0A49S lt LAS H L SNI S 402 01 A 18H 98H z zl L FUIOA49S lt EAS uf L YNI S 402 01 A S8H vey z L L UI0A49S lt EAS uf L NI S 402 01 il ES c8H z L L Gul0A49S lt EAS H L ZNI S 402 01 i 18d 084 z I SR ELUS LAS A L INI S 165 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS Jo bed EQ UoISIA 1 aJempey pyeoq oipe JO OPeuIayos WOU e pg anbi S
78. Bill of Materials for Servo Board Rev0O3 197 C 4 Bill of Materials for Radio Board Rev03 198 C 4 Bill of MaterialsforRadioBoardRev0O3 199 C 5 Bill of MaterialsforSensorsBoardRev03 200 C 5 Bill of MaterialsforSensorsBoardRev03 201 C 5 Bill of Materials for SensorsBoardRev03 202 C 5 Bill of Materials for SensorsBoardRev03 203 C 6 Bill of Materials for GPC Board Rev02 204 GG Bill of Materials for GPC Board Rev02 205 GG Bill of Materials for GPC Board Rev0O2 206 C 6 Bill of Materials for GPC Board Rev0O2 207 C 7 Listofdevelopmenttools 209 C 8 Listofdevelopmenttools 209 Electric Owl Final Report 8 LIST OF TABLES D 1 Expenses for the 2010 2011 School Year 210 Electric Owl Final Report 9 1 Introduction 1 1 Mars The Next Frontier From the dawn of time human beings have held a special fascination with the universe and its objects Be it the early Greeks astronomers from the Middle Ages or scientists of the modern age humanity has always looked up at the night sky with wonder and amazement at what lies beyond the borders of Earth s atmosphere On July 20 1969 mankind made one giant leap towar
79. C Board AVR Bus Passthrough The sole purpose of the GPC AVR is to serve as a passthrough between each of the buses and the GPC s ARM microcontroller As discussed in section 8 1 5 it is used to make up for the fact that the ARM does not have enough serial ports to interface with all of the buses Like the bus firmware on the AVRs on the other boards the GPC AVR polls for incoming bytes on the four system buses When a completed packet is received it immediately begins transmitting the packet to the ARM using DMA Unlike the bus firmware on the other AVRs the GPC AVR does not strip frame delimiters process escape sequences or check the packet s CRC or destination ID leaving those tasks to be handled by the ARM This minimizes the likelihood that the AVR will miss an incoming byte by ensuring that it returns to the polling loop as rapidly as possible ARM Interface In addition to listening on the buses the GPC AVR polls for incoming bytes sent to it by the ARM buffering them as they enter All traffic from the ARM to the GPC AVR is wrapped using the bus protocol When the GPC AVR receives a complete packet from the ARM it checks to see if it is a special packet addressed to it see Special Commands Electric Owl Final Report 42 CHAPTER 3 FINAL DESIGN below and if so processes it Otherwise the packet is immediately transmitted to the board s assigned bus using DMA The GPC AVR is also responsible for forwardin
80. Chip Debugger for use with programming the ARM It is assumed that the user has already installed 1ibFTDI version 0 18 or later and libconfuse version 2 5 or later These packages are straightforward to compile and install and do not require any special compile time options for them to work for this project 1 Get the source for Open OCD from the Internet e g from the Open OCD project page on SourceForge As of this writing the latest version of Open OCD is 0 4 0 and the name of the file containing the source is openocd 0 4 0 zip 2 Navigate to the directory in which the source was saved and run unzip openocd 0 4 0 zip cd openocd 0 4 0 to unpack the source and switch to the build directory 3 Issue configure enable parport enable ft2232_libftdi make sudo make install to build and install Open OCD The enable parport option sets up Open OCD to work with the parallel port ARM JTAG cable and enable ft2232 libftdi enables support for the ARM USB OCD cable 4 If desired the build directory may be removed after the previous step is complete cd rm r openocd 0 4 0 Electric Owl Final Report 150 APPENDIX A USER S AND SAFETY MANUAL A 10 Safety Precautions A 10 1 Lithium Polymer Batteries The Lithium Polymer batteries used in the aircraft have a surprising energy density These must be charged and stored carefully and safely to avoid short circuits The batteries are rated
81. FETY MANUAL e One PC with all necessary software dependencies installed a copy of the project Git repository and at least one USB port The computer must be capable of running the Houston ground control software e One 333 RPM turntable with printed calibration pattern Turntables with other rotational rates can also be used e One LED with through hole leads Brighter is better this LED will be used to create a stroboscope tachometer to make a more precise measurement of the turntable s rota tional rate e One function generator with a BNC output connector e One oscilloscope with BNC input connectors It is very helpful if the oscilloscope has a built in frequency measurement feature e One pair of BNC clip leads e One BNC cable e One BNC T connector To take gyroscope calibration data use the following procedure 1 Complete step li Jof the accelerometer calibration procedure 2 Re compile the main set of sensors firmware by issuing make build avr main_sensors03 hex in the software majortom directory Note that the firmware must be configured to at least have the sensors board respond properly to requests for high rate data Electric Owl Final Report 133 APPENDIX A USER S AND SAFETY MANUAL 3 Plug the servo board target sensors board radio board and GPC board into the back plane 4 Power the backplane by plugging the wall adapter end of the shore power cable into an available wal
82. Final Report 45 CHAPTER 3 FINAL DESIGN must wait until either the recipient is ready to receive the message or a timeout occurs Similarly when a thread attempts to receive a message it will return immediately if another thread is currently blocked waiting to send Otherwise the receiver will block until either some one else sends a message to it or a timeout is reached Special timeout values of zero and infinity are available The simplicity of the IPC subsystem means that the required kernel support code is very small and thus its correctness is relatively easy to verify If more complicated IPC interactions are desired by user threads they can be built on top of this single low level primitive Interrupt Management The kernel includes device drivers for only the two timers required to implement preemptive multitasking and other scheduling timing events All other device drivers are handled inside user threads Since the ARM microcontroller has no memory protection it is important for the programmer to ensure that only one thread attempts to use a given I O device at a time Although the drivers for I O devices are implemented outside of the kernel the kernel does provide some support to make these drivers more efficient Specifically it provides a facility for a thread to sleep until a given hardware interrupt is triggered This is done through an extension of the IPC primitive mentioned in the previous section When an interrupt
83. GQLOVME8931 H88LINHO ereny eso S080 HZX OIINVH3O AOS dd00 dVO c gg6u Xu s08000 oabe ego dOSW8 HO N 93H MS YIELO 9l gSdON ININ8ZvYEIWT euonen OSN S080 HZX 960L AI 4NF 439 AVI GLOVMTOLOLZH6LZINHO ereny ISO ANS ATOd 19913 A91 ANEE dvO OL9JNOEEVEVO9LIXAW uoO llu8uO uoddiN oso S080 HZX 960L AY 4NF H3O dVO GLOVMTOLOLZH6LZINHO ereny 4S0 uonduoseq Med JUN JUN sopjeg O 0 Ae peog OM 104 SJEN JO III CO AQEL 196 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS d8u 68H CWS S080 M8 L WHO A0 0Z S3H 7200244230 LH wyoy Su 98H 8H 18H 9 vey 88H AWS S080 M8 L WHO A0 0L SAY 20014dZ30LHON wyoy 984 Fo zeu 08H 9 S EW 9 EW Z ejJqeo uoisuejxe oAJ8s yr Gre LIN S 9 QNS ATOd 103 13 91 ANGE dvd 2094IN06EVHVO9ILVXdV X U09D 1uayo uoddiN tO ANS HN00 HMd GTSIHS HOLONGNI Y LOL pZYG SO UOIIOD 071 I1 ZLGOS ADE VL AMLLOHOS 30010 3 MV10 1L9 ou s polq 0 0 S080 HZX OIINVH3O AOS 4d00001 dVO 01886H Xu 8 08020 oabe elo 4 S080 HZX ASZ 9601 NO INH3O dVO VZlVMT0LO S080 XAV ZLO 9031 HZX OIINVH3O ASZ 200 L dVO N LOVHEASOLDIOZLD EEN tZ 020 2 91088 NAd LS VINOOS A MS DAH Ol INVL92WT1 jeuoneyN 0 0 QNS ATOd 193 13 AOL 4N9S dvO DO9JNO9SVEVOOLOXAW uoO luu89uO uoddiN 90 QNS VO S HNSI H3MOd HOLONGNI WOS L 092 LHHS suinog 091 OWS ADE Vr AM LLOHOS 30010 1 9 3 v18 Keusi 090 S080 HZX OIINVH3O AOS 4d00001 dVO N LOVESAE0LIG080
84. ICK packets Flight Plan Packets There are four types of packets used to for reading and changing the plane s on board flight plan see section from the ground computer Packets of type UL_CMD_PTR_READ are sent to request the number of the flight plan step that the plane is currently executing The data section for such packets is empty Similarly UL_CMD_PTR_WRITE packets are used to set the plane to execute a specific step in the current flight plan The data field for packets of this type consists of a single byte the number of the step to begin executing UL_CMD_STEP_READ commands are sent to read back the flight plan entry for a specific flight plan step The data field for such packets contains one byte that holds the number of the step to read back Likewise UL_CMD_STEP_WRITE commands can be used to write a new entry to the onboard flight plan The data section of UL_CMD_STEP_WRITE packets consists of a flight plan step laid out as specified by the flight plan mechanism see section 3 3 3 followed immediately by one byte indicating the step to modify 3 6 Prototype Aircraft Hardware 3 6 1 Airframe In order to simplify development a popular oversized hobby R C aircraft was chosen to carry the avionics package This aircraft the Senior Telemaster from Hobby Lobby is a high wing monoplane with a 7 foot 10 inch wingspan conventional landing gear and lifting tail In the absence of the avionics package the plane weighs about 11
85. IH NNOO L0 Sd2 d 40 9SOJIH JJOSNOO ANS ATOd 19373 91 ANGE dvd DO9JINOGEVEVO9LVWXAW Uu09 Iueu uoddIN YLO uonduoseq Med JUN JUN sopjeg O c0 eH peog Od 40 SJENSJEN JO 118 9 D 31QEL 207 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS C 3 Additional Tools C 3 1 Airframe Construction Although the Senior Telemaster kit comes largely pre built some essential tools are still needed for final assembly and for modifications needed to mount the avionics All of these tools can be obtained from any reputable hobby store selling R C aircraft Attachment of balsa and plywood components requires gap filling cyanoacrylate glue in most cases Attaching the tail assembly should be done with 5 minute epoxy A set of X acto knives is needed for removing damaged covering material and cutting balsa A hacksaw is sufficient for cutting thick balsa and plywood in combination with coarse grained sandpaper to remove unevenness Most of the additional wood needed for modifying the airframe consists of pieces fashioned from simple half inch square balsa sticks As minor damage to the airframe is inevitable the material covering it will need to be patched This requires a supply of Mylar covering ideally Super Monokote from TopFlite A monokote sealing iron will also be needed Scissors are necessary for cutting pieces of Monokote Installing new pushrods will require strong wire cutters Small
86. IX B SCHEMATICS AND CAD DRAWINGS 8 Jo aBed go UoISIA 1 BIEMPIeY p1eoq omas JO 9r euJeuos HOI g g aunbi4 6 8 p 9 S z L obpug Last Ag NMVEO 30 L0 39vd ESDA 0022 T NOISIA3H END 5 quu GT ONS A g LIH ZO UOISJOA pJeog oAJes Lxiesng b S n via Ssoepsjuy sng Kar LooAgsng L z 3d iu3xiesng E 3 SL s 0022 3 E de 0r exes Lie b SEN een Sra 2LGAHS9NS vn ET E cb CC Lang o lt gt Esga ESDA 0022 I i 9 b KR N gt FS9Agsng 20 VS N gt L99AISng s SNS ATS Sly 4 4 ld L xLesng sta pra a z yA p lt erann Pp sane eq Tel reza L ugx Lzsn uMd esna Md Leg GE SIS A 00 2 Lxycsng blu L se cb Lang go EsnqA1 lt Lu lt FIDA zsng Joan ES 1 0935ng ppc ee L 99A0sng ZLOAHGONS en FA W I EIDA 0022 b lt ESNqgAH p k SNQAH L k i s GND 99 g ely 9 KI k sn i HAM zsng HAM OSNd SE via ps ls 09A len
87. JO oreuleuos HOI ze d anb 8 Z 9 S v z II ueu poig aqoy Ag NMVEO 30 GO 39vd NOISIA3H 3n quu go uolsi8A peog siosuas s18 W018 399Y Dellt L 99AV xs OSU AOL LG L Al995V gt LAS L ele L zieoov woe Lk hs vau LJ uos Teso x0z SSH host vso UNION MO Su no LAS L 7g oN se Or NOA WOO Geh 9N WOO 402 EE LL EN inox INOO ES ad GON SEEIXAW ON bos leso F yr Sn Woo N snot 4u004 AS 40e Cen ISO oso 3i 9N ON osn L 09AV 175 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 8 Jo 9 abed EQ UOISIAJI SJEMPIEY pipoq sJosues JO JIWayos 1inoJl ez g anll L S eDpug Aer A9 NMYYA NOISIA3H 30 90 39vd Ald go UOISIJA peog siosuas iddns Jamog AG qi VuJOG mo AS 1nOA wt 1 ange MV108L VITA 09d STE o a an4 3n tl Hnos o m 299 099 T VA A 8 NS z 091 3uo1 g I LNPSLZ9Lld een p 1008 NSZ922W1 uA J z z L 39ASng y ad O O loo ro 09n AGI 9101 UIA 176 Report ina F Electric Owl APPENDIX B SCHEMATICS
88. Lo 0WNWod 8vd Fig LP Hed Id Sv1r g 1noaa eWMd OSLH OMVANNOd L d Fzg L PTO 91H j NIQdA oxod oaxL 3oNiNod evd yg L XL 310SNOO esodnoaxe Ademod svd es L gt XH 3 T0SNOO te Ee api Lav ONTOLMOML ONONAO d bVd Pag seu S veu lt zeu S ieu S oey 9 V ee en aa suoo1 Auen 3u001 y sav OXOS ZINMd ZN3IOd 2vd pp Em d i i grav OSOLLMNMd NSWOd Nd 7 gen eco zen teo ogo d y 3aunaw OVOLL OWMd ON3INDd Ovd Pap a oen VISZNVS L61V L 9109A 6 8 1 9 S n z 181 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 6 JO y aBed 20 UoISIA 1 QIeEMPIeY pueoq Oc JO 9l euu u2os Pno ez g an 8 9 S ueuioJg SQOy A8 NMYYA NOISIA3H 30 vO 39vd ad ZO UOISJOA pJeog Od5 eoeneju gen TUL 7 001 Edid d Oru AL ave Is Ho VrH EIDA dg oc d ose T _ ssh 3 Ja 3 T P lwo2 ewm zro2 eva zz d ru dee z le 340 1 asn 9v4 taaa uooL ut wo uz 2 Y _ kwaa lt gt Kaisi tr 7 001 GW WA Led AL eru Ly vert ovo ery ESDA 8 z 9 S v e 182 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 6 JO Abed 20 UoISIA 1 aJempJey pIeoq Oc JO 9euleuos 1In9JI 0g g n6i
89. NS ATOd 19373 A91 ANGE dvd DO9JINOGEVEVO9LWXAW OuoO lui 8uO uoddIN YLO ANS HNOOL HMd Q T3IHS HOLONGNI Y LOL pZYd SO UOIIOD 071 I1 ZLGOS ADE VL AMLLOHOS 30010 3 NV 10818 ou s polq za S080 HZX OIINVH3O AOS 4d00001 dVO 01886H Xu 9 08000 oabe ezo 4 S080 HZX ASZ 0 4NOL INH3O AVI VZ1WAV010 5080 XAV eo t 9031 HZX OIINVH3O ASZ 40 L dvO N LOVHEASOLDIOZLD Joen 119029 E 91088 NGd S VINOOS A MS DAH Ol INVL92W1 euoneN OZN OWS x4 ASZ ANEE 19313 dvd dO 3 D43 333 093 oIuoseueg PO ANS HELL Jd T3IHS HMd YOLONGNI LINTSLZ9LLd asind 091 ZLGOS ADE VIL AMLLOHOS 30010 3 MV10 9 ou s polq 090 S080 HZX OIINVH3O AOS 4d00001 dvd 01886H Xu 9 08000 oabe 90 S080 HSX ASZ 310 L YAO dVO 1 OMSOLP SZ l ZMN L u pnA o rep 299 9031 HZX OIINVH3O ASZ ANO dvO NLOVHEASOLDIOZLD EEN 099 dOSd8 AS VI MONE HOLIMS 938 OI S8dON 0 S HINSZ922W1 euoneN 090 S080 HZX 9601 ASZ ANGI H39 AVI TLOVMESI3LZHSLZINHO ereny GSO VSO EGO Su 99H CWS S080 M8 L WHO A0 0Z S3H 7200244230 LH wyoy 99H pay Cou ee 9 AWS S080 M8 L WHO A0 0L SAY 00LJdZ30LHON wyoy ISH AWS S080 M8 L WHO MO SI SAY 20Sl4dZ50LYOW wyoy OSH S080 HZX 960L AY 4NF 439 dVO GLOVMTOLOLZH6LZINHO ereny 299059 c ANS 0Z A 9 4N0L LNVL dvO H8W90LPOdOL wyoy ISO dwy dO SONO lluq 0197 UOISIDAId ewogoJoru yiyse ABL HdIVO rvdO LL isn uonduoseq Med JUN JUN sopjeg O g0 eH PIBOg SIOSUSS JO s eueje N JO llg CG eiqer 20
90. NUAL_DATA_CAPTURE symbol configures the sensors firmware to dump calibration values out to the data capture bus only when the user tells it to by sending a specific character over a different bus If this symbol is not defined the sen sors board will stream data continuously onto the data capture bus For accelerometer calibration manual data capture is used 4 Compile the sensors03_take_caldata hex firmware program by running make build avr sensors03_take_caldata hex in the software majortom directory 5 Plug the sensors board with the accelerometers to be calibrated into the backplane 6 Power the backplane by plugging the wall adapter end of the shore power cable into an available wall socket and the other end into one of the RS 485 jacks on the backplane Electric Owl Final Report 127 APPENDIX A USER S AND SAFETY MANUAL 7 Connect an AVR programming header to a USB port on the PC and to the appropriate site on the target sensors board Write the calibration data dump program into memory on the sensors board AVR by running avr program sh build avr sensors03_take_caldata hex at the command prompt inside the software majortom directory If the programming of is successful unplug the AVR programmer from the PC and the sensors board and set it aside Otherwise fix any errors that arise and make sure that the board is programmed before continuing 8 Connect two RS 485 transceivers to the PC Plug one into
91. OISIAJI SJEMPIEY pipoq omas JO 9I euJleuos HOI 7 g N 8 Z 9 S n eDpug uJj r Ag NMYYA 30 0 39Yd NOISIA3H qi quu ZO UOISJOA peog oes sindino ones z n L d LAS 91nO S LT l Ji LAS 9 imo e sey Fgy rja y vig 1008 D Sino S Tris na Pg s 3o 9 ano zi o 768 BE 899A V99A al z ren 1 S L m LAS 9 EAS KIOJA 1no s s ris mo ja 3 vr lt _JPomes e v 30 Q an9 d z sf 0L S E z L Ju EAS ze 9 en YA ER 1no s oen v EAS L 99A z 4 t e o L d LAS ZLOv UO S cen np ni LED DECH YA E Ju Wo OPNS EAS KO LINO S 8 L 9 S Y 160 Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 8 jo y aBed go UOISIAJI SJEMPIEY pipoq onas JO DIJEWSYOS HOI g g aunbi4 8 L S uewyoosg USQOY Ad NM vH 30 YO 39vd NOISIA3H 3714 SE gt WA quu WA CO UOISISA
92. ONS AND BILL OF MATERIALS Figure C 4 Front assembly diagram for Sensors Board Rev 03 reproduced to scale The silkscreen indicates the component reference designators for the corresponding pads Part information for each reference designator is in Table C 5 s ORA SI I inne 048 Fa t ER E Carm ug ETE d USB PACCO aT o Figure C 5 Front assembly diagram for GPC Board Rev 02 reproduced to scale The silkscreen indicates the component reference designators for the corresponding pads Part information for each reference designator is in Table C 6 Electric Owl Final Report 192 APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS 109 SOd 19S 1434 H3QV3H NNOO YV v0V9 01 196 WE HMd lez L ojsna v 9d VV9LZ OG VI AO AM LLOHOS 20010 INOY11SALS ONIS sa va ed za lq 9 OIOS 8 A S8VSY H3AISOSNVUL Ol GZLGAHS9NS LL yn en n In v S080 HZX 960L A9L 4NF 439 dVO GLOVMTOLOLZH6LZINHO ereny YO O cO IO t LIH OLY GLY v LH AWS S080 M8 L WHO M0Z Z SAY L0Z2JMdZ30LHOIN uuoH ELH ly IIH OLY 8 Jepeeu ajew a Bue juu uo z uldgxz HV 229 0L2196 NE fez osna v uonduoseq Med JUN JUN sapjoy O 0 Ae PIBOg oA48S 10 SIPL EN JO Nd CO AQEL CO UOISIASA PIBOG OAJ9S 7779 Gerd ddd 9 9 LX L 87S912 oo L 14V Sng 3HO4 sna y 9 jo1d MO LHOd 9 9 VH LOL9 Z0Z V xeiowN 14v Sng 3uod sna SOd2 3 1 NVH d1 LNNHS L Gv 6188 oo L 8 1059 SOdZ 19S 143 H3Q
93. Report 141 APPENDIX A USER S AND SAFETY MANUAL Fitting models to the calibration data is accomplished through the use of the following MATLAB scripts e cal accel m Generate accelerometer calibration values e cal mag m Generate magnetometer calibration values e cal gyro m Generate gyroscope calibration values e cal airspeed m Generate differential pressure sensor calibration values For more information on these routines and how they work see section 4 2 and the com ments within the individual files themselves The user should not need to access any of these routines directly but should instead use the interface provided to them through the caltest m and gen cal prog m scripts There are only two exceptions to this e The RP ROTATION RATE variable in the cal_gyro m file needs to be updated with the rotation rate of the turntable measured in step of the gyroscope calibration proce dure Convert the measurement made to have units of mrad s and store the result in RP ROTATION RATE e f different pressure levels from those listed in step 5 of the differential pressure sensor calibration procedure were used for taking differential pressure data these values in inches of water will need to be substituted into the p array at the start of the function in the cal airspee m file At the same time their corresponding airspeed in miles per hour will need to be substituted into the a array in the same f
94. Team Electric Owl Design of an Unmanned Aerial Vehicle for Martian Exploration Final Report Rice University Department of Electrical and Computer Engineering 6100 Main St MS 366 Houston TX 77005 Anthony Austin Senior Electrical Engineering apai rice edu Jeffrey Bridge Senior Electrical Engineering jab3 rice edu Robert Brockman ll Senior Electrical Engineering rtbi rice edu Peter Hokanson Senior Electrical Engineering pchi rice edu Faculty Advisor Dr Gary Woods Elec and Comp Eng gary woods rice edu JSC Mentor David Fuson ESGC Jacobs david fuson escg jacobs com TSGC Mentor Dr Hum Mandell UT Center for Space Research mandell csr utexas edu Spring 2011 Contents 1 Introduction 1 1 Mars The Next Frontier 1 2 Unmanned Martian Exploration 1 3 Airborne Mission Requirements 1 3 1 ight Environment 1 3 2 ErtremeDistance 1 33 Component Failure 1 4 eProject 2 Design Strategy 2 1 Fault Tolerant Mars Capable Avionics E e a 2 1 2 Radio Communication 2 1 3 Flight StateSensorsi 2 1 4 Flight Computer 2 2 Project Focus 2 2 1 Flight CapableHardware 2 2 2 Basic Autopilot 2 23 SensorRedundancy 2 2 4
95. Team Electric Owl considered some of the details of the fault tolerance that would be required for an actual Mars mission The canonical approach for improving fault tolerance is to eliminate single points of system failure by using redun dant components This design technique is currently used in nearly every piece of space exploration technology from unmanned probes to the Space Shuttle Because of the unique requirements of extra terrestrial flight system failure must be accounted for and recovered from very quickly Thus any fault tolerant design must employ an automated failover scheme whereby the system immediately switches over to redundant backup components in the event of failure A high level block diagram of the team s proposed solution to the design problem is shown in Figure 2 1 1 Control Surface Actuation Because mechanical systems are prone to failure especially in harsh extra terrestrial envi ronments duplicating at least minimal control function to ensure that a single stuck actuator would not cause catastrophic failure is needed On the Space Shuttle this is done using me chanical redundancy with multiple actuators 7 a frangible pin will shear off a faulty actuator disconnecting it from the control surface It seems reasonable that any Mars UAV would need to have a similar system for dealing with faulty mechanical actuators Electric Owl Final Report 15 CHAPTER 2 DESIGN STRATEGY mm mm zm mm S S
96. UE H3MOd HOLINANI A0Lb 8Z07YHHS sunog 091 G Z LOS NMOQ d3LS 90 90 ANOD 9l 8 L 4INOZ9EWT euoneN on SSH pay AWS S080 6L M8 L WHO M0 Zr SAY c0 vJdZ3OLHON wyoy GH CGH ISH OSH 9 A 9QINS 0Z A 9 ANZ LNVL dvO H98IN9ZvPl OVO L uluod oso 2103 HNZv 0 H3AVTILETOIN HOLONGNI ALVY OZ LOS yal ost dod dOL IVNHON QHVO AHOWSW NNOO 698 L 1Z6008 9S 1 XAV ONW AS S080 HZX 960L AY 4NF 439 AVI GLOVMTOLOLZH6LZINHO ereny YVO S080 OdN A00 S AdEE INH3O dVO VZ 1WPO V1S080 XAV ERC 1 S080 OdN A0S S ddS INH3O AVI VZ 1WPOSLWSS080 XAV evO MO c EZLOS VWOEL AOS HO d LIASON 3 48SS9 ou sapolg WOOD Zz AWS S080 M8 L WHO MOS I SAY LOS LHdZ30LHOIN wyoy VEER c AWS S080 M8 L WHO A0 S3H 0 JdZ30LHON uluod 6rH evH c CWS S080 M8 L WHO 0 22 S3H 0422344230 HOW WYOH Lvyd ovH c uonduoseq Med HN JUN sopjeu O CU eH peog Od 40 SJENSJEN JO 118 9 D 31QEL 206 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS ave AS S 30 L H3AV1 318NOU dVO 1s0rasus aa eoueuly EU 169 CWS dd 0 9 ZHM 8972 WLSAYO 1 1 9 ZH389Z 2 S2Sg8V uooeJqy X S080 HZX 960L AY 4NF 439 AVI GLOVMTOLOLZH6LZINHO ereny 069 OIOS8 GNI SDYVHO L HSdSSMANWIL Ol NZZ0 1Sd UIIXelA 060 S080 HZX 960L AI 4NF 439 AVI GLOVMTOLOLZH6LZINHO ereny v89 89289 189 ANS 0Z A 9 INOL LNVL dvO H8W90LPOdOL wyoy 089 9 0S 91 HAOH HAG INN ZEZESH OI YdIIZEZEXYN IL isn 07109 V d WNZ SOd YJOV
97. V3H NNOO yV v0v9 201 196 NE eran 8 AWS S080 M8 L WHO A00 L SAY LO0LJdZ30LHOIN wyoy cy lu 8 nv SHALL 3NOYOIN 9Z YA d3O3H 183A dOl 37101 ESpE9 194 H L 1H3A WNZ SOJOL L3MOOS NNOO HV 2019 0170S6 NE 9Y sna ze uonduoseq Med JUN JUN seopjoy O 0 Ady eue dxoeg 104 SIENAN Jo 118 z 2 AQEL CO UOISIASA ue dy52eg 129 193 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS 109 SOd 19S 1H3A H3QV3H NNOO HV v0Tv9 01196 We lesveciuinos Y OIOS 9I HALNNOD 3avoaa 1n0O 0L 9I 96 N8Z Ordo LL zen S080 HZX 0 L AY 4NF 439 dVO GLOVMTOLOLZH6LZINHO ereny LEO 060 2 9 EZLOS 1191 ISNVHL TAT LIOA Ol HASGLIOLOSXL LL Len OEN Z AWS S080 M8 L NHO 4001 SAY LO0LJdZ30LHOIN wyoy SCH IZH zZ Jads amp evo c dOSW 8 N1 04d dati 9l 8SWHdZS99011 1e ur eon dOSW 8 N1 DJHd 45H OI d8d S 2 8SNH82S99O 11 seaun IZN aNs S080 qati q31 YL HZL L H4 099110913 ajue s oza CWS S080 L M8 L WHO 0 r SAY 007vJdZ30LHON wyoy la I AZO 629 829 S080 HZX 960L A9L 4NF 439 dVO GLOVMTOLOLZH6LZINHO ejem ZZO SZO veo Szo 4 azo ozo ANS 9602 A 9 ANOL LNYL dvO H8W90LPOdOL uuoH gzo veo 920 ad 9 S080 VW00l SWHOZ9Z dIHO 31184834 01 H2S2VS08041 pare IZI 1 S080 HNO YAAVTILINN YOLONGNI LINOOL37Z LOZZ TIN yal 071 ANS S080 M8 L WHO A0 0L SAY 2001 JdZ30LHON wyoy DEU NIL 89d WNZ SOd9 143938 NNOO s0 wsaz sa9 1140 9SOJIH Idd S080 OdN AOS S Adz INH3O AVI VZ 1WP0Z1WSS080 XAV IZo 0
98. abe YVO S080 HZX OIINVH3O AOS ANOL dvO N LOVESAV01950809 Joway evo 9602 HZX SHOADG JNOL OZZZ LWS AWS DITIN IN90LHLHZX0S7SO SOL Ovo 2 92 OL H3HOLIMS 3T1dNIS 93H OI g8dON 21 S9 92W1 euonen om 0709 1H3A 001 SOdv YIAVIH NNOO 000 7S0Z X ON liva AH uonduoseq Hed HN JUN sopjeg O 0 ed peog OAJAS 104 SJEN JO III CO eiae 195 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS OLZL 9602 HZX ASZ 4NOL HAO dVO IN90L31HZXS22 O SOL 099 L 9ZOL AS VE MONE HOLIMS 93U Ol g8dON 0 S 3r19 922W1 euonen 090 S080 9601 HZX AOL 310 L H3O AVI MSOLVLYZXZLOZO yal 959 CWS S080 M8 L WHO M9 SAY AE 9 g3Vv9 vu3 093 9oIuoseueg 854 CWS S080 M8 L WHO MOL SAY Ar8183V9 vu3 093 9luoseued ZLGH CWS S080 M8 L WHO MS 8 S3H LSr84dZ30LHON WYOH 9SH CWS S080 M8 L WHO A00 L S3H LO0LJdZ30LHOIN wyoy GSH SHOAGZ 4NZZ 2181 LINS GINS 991N IN9223LHZXe SvO SOL GSO OWS VS AOE AM LLOHOS 30010 4 1 00 S8 du sepoiq osa AOE HO N 19S 8 OS SLI SON V0699SqJ pyiyoure 0SO ANS HN8 L GAQ7SIHS HMd HOLONGNI LIN2Z2291LLd asind ost CWS 9021 Yo MZ L WHO SLO O SAY 1 SLO O Z L USO ejodypeis vSH S080 HZX OIINVH3O AOS 4d00001 dVO 01886H Xu 8 08000 oabe YSO CWS S080 968 MOL L WHO 0SZ S3H Q 187 d022LHH nunsns esy CWS S080 M8 L WHO AL 08 S3H LO JHZ30LHOIN wyoy Ace AWS S080 968 MOL L WHO 0SZ S3H 0 19 d033 LH nunsns ISH 090 HZX 9601 ASZ 4400089 H3O AVI
99. ach peripheral controller one for transmitting and one for receiving The chip is programmable using a standard JTAG interface A software development toolchain based on the GNU Compiler Collection s GCC ARM compiler and the Open On Chip Debugger OpenOCD is available for Linux Bus Interface Hardware Like the other circuit boards the GPC board is equipped with an Atmel ATXMEGA32A4 AVR microcontroller for interfacing to the system bus Unlike the AVRs on the other boards the GPC AVR only handles bus traffic and does not communicate with any on board devices other than the bus transceivers and the ARM The AT91SAM7S ARM microprocessor does not have enough serial ports to listen to traffic on all four buses at once so the board s AVR serves as a go between sending received bus traffic upstream to the ARM Electric Owl Final Report 30 CHAPTER 3 FINAL DESIGN and forwarding packets constructed by the ARM that are intended for other boards onto the bus Communication between the ARM and the GPC AVR is accomplished using a serial link Serial Debug Console The GPC board has a connector that provides direct access to one of the ARM s serial ports for a software debug console to assist with development SD Card Interface The GPC board has an SD MMC connector that can hold a single SD card for storing data on board such as system logs The team has developed some firmware to read from an attached SD card but the firmware for
100. aken for all three axes simultaneously A 7 1 4 Differential Pressure Sensor The easiest method for calibrating the differential pressure sensor is to use an already calibrated sensor as a reference The team was fortunate enough to have access to such a system at the wind tunnel located in the basement of Rice s Ryon Laboratory The procedure outlined here assumes the use of this or a similar setup The procedure for acquiring differential pressure calibration data requires the following materials One backplane board with at least two RS 485 connectors and at least one row of circuit board connection headers Make sure that no circuit boards are plugged into it Sensors board with sensor to be calibrated One shore power cable e One RS 485 transceiver cable One AVR programmer Electric Owl Final Report 137 APPENDIX A USER S AND SAFETY MANUAL e One pitot tube with plastic tubing for connection to the input ports on the differential pressure sensor e One PC with all necessary software dependencies installed a copy of the project Git repository and at least one USB port To take differential pressure calibration data use the following procedure 1 The firmware setup for gathering differential pressure calibration data is the same as that for magnetometer data collection Complete steps 1 6 of the magnetometer calibration procedure above 2 Use plastic tubing to attach a pitot tube to the i
101. and Byte Data 644 Data Figure 3 3 Byte structure of a bus packet Electric Owl Final Report 59 CHAPTER 3 FINAL DESIGN Validation Checksum Each packet contains a 16 bit CRC CCITT checksum that can be used to help detect errors in packet transmission Every byte in the packet is included in the CRC calculate except the start and end delimiters and the checksum bytes themselves Since the checksum must be computed before escape bytes are added in case the checksum bytes themselves need escaping the CRC calculation is not performed on escape sequences but on the underlying bytes being escaped For example if a packet s data section contains the byte 0x7E the CRC will be calculated using the byte 0x7E instead of the sequence 0x7D Ox5E At the receiving end the destination board strips off the frame delimiters de escapes any escaped bytes in the received packet and then computes the CRC of the result This is then compared to the checksum bytes sent in the packet header If there is a mismatch a trans mission error has occurred and the board can execute an error recovery procedure to handle the bad packet Command Bytes The command byte field in the packet header designates what type of data the packet is carrying The name command byte is derived from the idea that a packet sent by the GPC board typically contains a command for another board to execute Possible values for the command byte are given in table 3 3 Th
102. antly it dictates the procedure for uploading flight plans to the plane The chief reason for having a different protocol to govern uplink operations instead of just using the downlink protocol for bidirectional communication is security Uplinked commands need to be received by the UAV securely and reliably in order to ensure that the plane behaves as desired and is not hijacked by unwanted third parties This entails the addition of a few extra fields to the packet header as described below By contrast downlink communications need as much bandwidth as possible so that telemetry may be transmitted to the ground at the fastest possible rate Thus for downlink packets keeping the packet overhead to a minimum is desirable Packet Structure The structure of an uplink packet is depicted in figure The uplink packet header begins with a two byte protocol signature followed by a 32 bit message au thentication code MAC This is succeeded by a 32 bit sequence number and the header is completed with a byte that identifies the type of uplink packet The rest of the uplink packet contains data pertinent to the packet type Note that unlike downlink packets uplink packets do not have a field for specifying data size The data fields of all uplink packet types have fixed known sizes and so sending a size byte along with the packet is unnecessary Protocol Signature Like for the downlink protocol uplink packets have a two byte protocol signatur
103. apture data as described in steps 10 and 11 of the accelerometer calibration procedure 8 Connect the shore power cable to the backplane The sensors board should begin streaming its data over the bus and the busmonitor program should capture this data and save it to a file 9 After collecting data for about 15 seconds disconnect the shore power cable from the backplane Stop the busmonitor data capturing process by sending it a CTRL C char acter Take the data file and save it somewhere where it can be accessed for use in the pre processing step that follows 10 Repeat steps 5 9 for each desired flow rate You should end up with six data files one for each flow rate tested A 7 2 Step 2 Pre Processing In this step the raw data dumps generated by the previous step are converted to the formats required by the calibration scripts A 7 2 1 Accelerometer Magnetometer and Differential Pressure Data To pre process calibration data from these sensors run the raw data file produced in the data collection step through the cd2mat1ab program This program strips away frame delimiters and escape bytes added by the sensors03_take_caldata c program to help determine bound aries between data packets First if necessary build the cd2matlab program by running Electric Owl Final Report 139 APPENDIX A USER S AND SAFETY MANUAL make build pc cd2matlab in the software majortom directory The cd2matlab program ta
104. assigned a mailbox sequence number this is not the same as the uplink protocol sequence number see section 3 5 3 that identifies its position in the mailbox queue A packet is removed from the mailbox queue only when the radio board receives a BCMD RADIO MAILBOX POP command carrying that packet s sequence number in the data field The reason for this is so that the GPC can request retransmission of an uplink packet Electric Owl Final Report 38 CHAPTER 3 FINAL DESIGN over the bus by sending another BCMD_RADIO_MAILBOX_PEEK e g in the event that a bus error caused the original transmission to fail its CRC check Bus Voltage Monitoring The radio board is equipped with hardware for monitoring the volt ages of each of the four system buses Inside the event loop the radio board AVR periodically sets the ADC channels attached to the voltage monitoring hardware to begin a conversion It polls the ADC conversion flags for each channel and when a conversion is complete it converts the ADC value into a voltage value and saves the result The radio board will send the most recent values of the bus voltages in response to a BCMD_TELEM_FETCH packet by the GPC 3 2 5 Sensors Board Bus Interface The sensors board listens for the following bus commands see section 3 5 1 e BCMD_SENSORS_FETCH_HIRATE The board will reply with a BCMD_SENSORS_REPLY_HIRATE packet containing a set of high rate sensor data including measurements from
105. ation data collection procedure 6 Re compile the main set of sensors firmware by issuing make build avr main_sensors03 hex in the software majortom directory 7 Write the main sensors0O3 hex program into flash on the target sensors board AVR using the standard AVR programming procedure given in section A 3 1 The sensors board should now be loaded with the set of main sensors firmware set to use the calibration values just written to EEPROM A 8 Compiling the ARM Development Toolchain While compilation of the AVR development toolchain is fairly straightforward the ARM devel opment toolchain requires a slightly more specialized procedure in order to enable software emulated floating point operations If for some reason the user is unable to use the team s provided binary package see section A 2 the ARM toolchain can be built from source using the following procedure This assumes the user is working in a Linux environment with the usual development utilities gcc make etc installed Electric Owl Final Report 146 APPENDIX A USER S AND SAFETY MANUAL 1 Create a directory in which to perform the build For the sake of this procedure it will be assumed that the build directory is usr src build arm elf If a different directory is used the instructions below will need to be modified accordingly 2 Copy the following files from the software toolchains arm elf directory in the Git repository into
106. azadsela CL CH 402 dns z 2 Ee ved YMO y MONA a HNOL L Ley SATE QE L E dazooZaxdW EAS l ren uOgL 989 RE 0 u 8 9 S v rd 173 I Report ina F Electric Owl 8 jo y aBed go UoISIA 1 BIEMPJEY pipoq sJosues JO 9rjeuleuos UDO Leg anb 174 APPENDIX B SCHEMATICS AND CAD DRAWINGS Report ina F 8 d 9 S r E e ueunpoJg 14900H A8 NMVHG 30 vO 39vd NOISIA3H ald 31111 CO UOISJOA p1eog siosuas SOJ O EZOJ D Sto u0ZL gt ZNIXp Z1nOxr AEE B LJeuA ZOAD 0L ZLNO JOA gt tr z LL et ta Qd sed ES zH sed m soy 1NO9A jnoi 2u001 v H1VOESAT uoz T 401 soy adad vvO era FP 3v9 E gru a 9i PPA ON E99AV Hen uo avo KKOO gt Lan AXOJ D uoz evo gt EAAS XNIXp X1NOXy yee 6 gt or KINO JOA Cru 1S ALNOXy LE uocL OVO Tar dd ANIXE oesud1 AEE dH ALNO EL bb Ly N s y LNOOA ano 4uoo1 Ke u0Zr T 401 soy adad LOT oro si gro E Ory Be M 9L PPA ONG L 99AV Ov uoL vvo 8 z 9 S v e Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS g Jo eDed go uolsIA 1 eyewpueu pseOg SIOSUAS
107. ble the frequency of the LED and see if the pattern still stops If it does then the previous frequency was too low Additionally one can compare the measured rotational rate to the rated speed of the turntable If these numbers do not match fairly closely it is possible that the measured Electric Owl Final Report 135 APPENDIX A USER S AND SAFETY MANUAL rate was made using an alias frequency instead of the true value 13 Disconnect the stroboscope tachometer setup and set it aside 14 Mount the system on the turntable in the desired orientation There are three orientations for which measurement data must be taken one for rotation about each gyroscope axis The system should be mounted so that it rotates in the clockwise direction about the axis being measured Depending on the axis this corresponds to one of pitch down roll left or yaw right motion 15 Connect the nickel cadmium battery to the low voltage battery connection site on the servo board It may be easier to remove the servo board from the backplane connect the battery and then plug the board back into the backplane Since the system should now be powered telemetry data should be being sent to the PC You can verify this by checking for the flashing lights on the ground radio module but do not set the ground software to being saving the telemetry just yet 16 Set the turntable to begin rotating and wait for it to reach a steady state speed 17 Ins
108. c Owl Final Report 113 APPENDIX A USER S AND SAFETY MANUAL gcc 4 4 4 GNU compiler collection make 3 81 GNU make utility to maintain groups of programs perl 5 10 1 The Practical Extraction and Report Language Table A 1 Software dependencies required for Electric Owl development The arm dev avr dev and dev extralibs32 packages have been specially compiled by the team for work on this project and are provided in binary form as bzip2 compressed tar archives on the team s internal website To install them download the corresponding archive and unpack it in the system s root directory For example to install the ARM cross compilation toolchain use the following command sequence su cd mv path to arm dev 20100728 tar bz2 bunzip2 cd arm dev 20100728 tar bz2 tar xv rm arm dev 20100728 tar bz2 It is highly recommended that the developer use the team s provided binary packages for these toolchains and libraries but if this is not possible they can be built from source Instructions for building the arm dev package from source are given in section avr dev and dev extralibs32 are more straightforward to compile The remaining packages in Table A 1 can either be built from source by the user or obtained as standard binary packages shipped with most Linux distributions Only Open OCD should require a special build procedure this is outlined in section A 9 Note that some of these packages have depend
109. cO veo cO v AWS 9602 A 9 ANOL LNVL dvO H8W90LPOdOL wyoy 929229 7 S080 VW00l SWHOZ9Z dIHO 3118834 01 H2S2V9S08041 pare IZI d S080 HNO YAAVTILINN YHOLONGNI LINOOL37Z LOZZ TIN yal 071 AWS S080 M8 L WHO A0 0L SAY 2004244230 LH wyoy 0cH NIL 89d WNZ SOd9 143938 NNOO s0 vsae sae r Ldd 9SOJIH Idd S080 OdN AOS S Adz INH3O AVI VZ 1WP0Z1WSS080 XAV ergoe E QNS 4481 ZHW 82262 IVLSAYO L AYQ ZHIN824 7 28 18V uooeJqy pc E dJO L vr A9 L USBI AZE NOW HAV nv rveeeDeuix Iy Jeu sn VV9LZ OG VI AO AM LLOHOS AGOIA WOV1LSdLS GIE va ed za La v OIOS 8 A S8FSH H3AISOSNVUL Ol GZLGAHS9NS LL vn en en in v S080 HZX 960L AY 4NF 439 AVI GLOVMTOLOLZH6LZINHO ereny rO 8 O 2O IO t esna apeay jew a Bue juu tuutuu0 z uldgxz HV 229 0L2196 We zsng Lemg osna uonduoseq Hed JUN JUN sepjoy O c0 eH peog Od 40 SIENEN JO 118 9 D oO Z0 uoisi a1 pieog DAD STD 204 Electric Owl Final Report APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS AWS S080 L M8 L WHO 0 22 SAY 720242344230 LH wyoy vvH AWS S080 M8 L WHO M0 Ap SAY ZOLb4dZ50LHOW wyoy Spy abu cru ANS S080 GL M8 L WHO 001 SAY 0004244230 HOW wyoy ovu lvu c IWS 8 3dAL ISN ININ 143938 NNOO L0000L 00 S00 b 268 XEN asn i NVOE SOd Z STGNVH M dI LNNHS Z SrSL88 oo L euou z 109 SOd 19S 1H3A H3QV3H NNOO HV v0v9 01196 We lSl 31gvSiq DIr Zz 07109 SOd02 WWS 2 H30V3H NNOO M81S 0Ld Od8d LLHSS SUI INS OVE CWS 090 MOL L WHO 0
110. ce flying RC aircraft is relatively limited the team enlisted the help of one of the pilots Mr Keith Klix in flying the aircraft under manual control to reduce the risk of damaging the airframe during takeoff and landing Mr Klix flew the plane up to a reasonable altitude and then turned control over to the autopi lot by engaging the manual override switch on the RC transmitter The plane was programmed to fly in a straight line adhering to the horizontal path it was last on before the autopilot was engaged While the plane appeared to try and maintain this path as programmed it exhibited substantial undesirable oscillations in its heading At the end of the test Mr Klix landed the plane perfectly leaving the hardware in good condition for future testing Though the autopilot did not perform quite as well as the team had hoped this test was valuable because it was the first test of the fully integrated system in a real flight environment The team successfully collected a full stream of telemetry data from the flight including sensor Electric Owl Final Report 92 CHAPTER 4 TESTING AND RESULTS values and the autopilot s estimates of the plane s state for every flight frame This gave strong confirmation of the correct operation of the radio downlink and gave the team some data to analyze to improve the autopilot for the next flight 4 4 4 Basic Autopilot Flight Test 03 19 2011 After the previous test the team made som
111. cess is to build gcc but first some of the header files from newlib must be coped into the new usr 1ocal arm elf directory structure Run mkdir p usr local arm elf include cp av usr src build arm elf newlib 1 18 0 newlib libc include usr local arm elf include Electric Owl Final Report 148 APPENDIX A USER S AND SAFETY MANUAL to do this 8 Also prior to building gcc the multilib configuration file must be patched Run cd usr src build arm elf patch p1 lt 99 gcc arm elf multilib patch to do this 9 Build gcc by running the following commands cd usr src build arm elf build gcc sh do gcc make sudo make install It will take a long time for the build to complete The last command will put programs into usr local bin and lots of files into usr local arm elf usr local lib gcc arm elf and usr local libexec gcc arm elf 10 Configure and build newlib cd usr src build arm elf build newlib sh do newlib make sudo make install All of newlib s files should go into usr local arm elf include and usr 1local arm elf lib 11 With the completion of the last step the ARM toolchain has been built If desired the build directory can now be removed rm rf usr src build arm elf Electric Owl Final Report 149 APPENDIX A USER S AND SAFETY MANUAL A 9 Compiling Open OCD This section describes the procedure for compiling the Open On
112. dditional data that may be useful in future expansion Serial Sonar Interface In the fall the possibility of using an external ultrasonic rangefinder to measure altitude above ground level was investigated for use during automated landing where precision of the altitude measurement is critical for glide slope computations Although automated landing was not enumerated as a goal for this project the hardware was created with the ability to easily add this sensor if time permits Motor Data Interface During the fall semester a prototype motor tachometer board was produced for a separate course capable of measuring the rotation rate of the propeller This used a Hall effect sensor to measure the six poles of the motor as they rotated past the fixed tachometer Because the autopilot was able to fly the aircraft without this input it was tabled Additionally there was trouble mounting the tachometer close enough to the motor to measure the rotation rate and rigidly enough to avoid contact with the motor in the turbulent wake of the propeller blades and no investigation into the drag penalty this board introduced because it was never tested in flight 3 1 5 General Purpose Computer GPC Board The general purpose computer GPC board acts as the system master controlling the other boards and querying them for data over the bus It gathers data on the plane s state from the sensors board and then feeds this data into the autopilot algorith
113. ds turning that vast enigmatic ex panse known as outer space into familiar territory Since then many other manned missions have been conducted and dozens of space exploration probes deployed however none of these efforts useful and enlightening though they have proved has been as successful at capturing the hearts and minds of the citizens of the world as the first lunar landing that oc curred over 40 years ago It time for humanity to take its next giant leap out into the universe and there could be no better objective for this leap than to have a human being set foot on Earth s next nearest neighbor in the solar system the planet Mars But before one can even think about sending humans to Mars one first has to get the lay of the land In order to further this objective Team Electric Owl is interested in the development of a fully autonomous unmanned aerial vehicle UAV to perform efficient exploration of Mars Such a probe would be able to fly quickly over the planet s landscape and survey large swaths of territory with great detail thus helping prepare the way for eventual human landing and colonization Electric Owl Final Report 10 CHAPTER 1 INTRODUCTION 1 2 Unmanned Martian Exploration Current unmanned Mars exploration strategies have significant limitations In the 1970s NASA sent the Viking series of probes which were the first successful Mars landers While the images and data acquired from these uni
114. e Using this external part allows for a 19 bit resolution of the pressure measurement which ideally corresponds to sub meter altitude res olution and also makes available the ambient temperature measurement used for calibration however atmospheric pressure also varies substantially with weather patterns and so the measurements may not be sufficient to safely land the aircraft The newest revision of the board features unpopulated zero ohm resistor pads on the 12C data and clock lines to each chip so that they can be cut and reestablished for testing if necessary Serial GPS Interface An OEM Garmin GPS unit intended for serial operation is included in the standard complement of sensors onboard This sensor has low precision even with a 3D fix on the satellites The accuracy is improved slightly by the addition of the FAA s WAAS system for differential measurement however even with these features the margin of error of the GPS is at least 3 m and only has a sample rate of 1 Hz Data from this sensor is input to a rudimentary Kalman filter meant to combine this with the inertial measurements to improve Electric Owl Final Report 28 CHAPTER 3 FINAL DESIGN accuracy The GPS is operated in Garmin s proprietary binary mode rather than the standard NMEA data This choice avoids the necessity of writing a parser for the text based NMEA format and instead allows the direct importation of binary C structures This also exposes a
115. e harsh radiation and the fact that the extreme distance makes manual intervention impossible pose some of the serious concerns that must be addressed Electric Owl Final Report 11 CHAPTER 1 INTRODUCTION before airborne exploration of Mars can be attempted 1 3 1 Flight Environment Martian Atmosphere The most immediate concern in designing a Mars aircraft is the thin Martian atmosphere The air pressure at the surface of Mars is approximately equivalent to that at 100 000 feet on Earth The thin atmosphere makes it difficult for an aircraft to generate the lift forces required to keep itself in the air This places severe constraints on the design of the airframe especially in terms of propulsive power and total aircraft weight Energy Gathering Because Mars lacks the infrastructure for any sort of chemical refueling energy for propulsion is likely limited to electrical energy gathered with photovoltaic cells and stored in chemical batteries Propelling the aircraft would have to be accomplished with an electric motor Although the technology for all of these has improved substantially in the past few decades gathering sufficient energy to ensure continued flight will be a stringent design constraint 1 3 2 Extreme Distance Interplanetary Transit In order to get to Mars any probe must be designed and built on Earth The aircraft would almost certainly need to be folded and compressed to fit into a rocket which would launc
116. e bus pins These can be used to daisy chain multiple backplanes together to con nect more than eight circuit boards or to provide shore power and debugging interfaces Eight modules has proven sufficient for redundant sensors measurement but expansion may be required if the other modules are made redundant in the future At the ends of each bus there are pad for terminating resistors R1 and R2 near each external header This exists to allow proper termination of the buses by matching impedances This reduces signal reflections in the line at the cost of a constant current through the low valued resistor Testing to date has not shown a need for this component although if boards Electric Owl Final Report 23 CHAPTER 3 FINAL DESIGN are connected together it is a potential issue of which to be aware Reflection issues should ideally be resolved by a terminating resistor on each end of each bus in a serially connected arrangement 3 1 2 Servo Board The servo board uses the standard ATxMEGA32A4 AVR microcontroller found in all of the boards This board interfaces with the R C controller and the control servomotors uses the main and backup batteries to provide 12 volt power for the avionics system bus A front view assembly diagram of the third revision servo board is shown in Figure C 2 for the parts enumerated in Table C 3 Analog servomotors commonly seen in R C aviation use a three wire interface 5 V power ground and a
117. e data payload types associated to each of these values are discussed in the sections below Since the system uses few of the available values for the command byte it is easy to expand the system to accommodate more packet types by defining new command bytes Generic Data Fetch Commands The BCMD_TELEM_FETCH command is used for retrieval of data from any of the boards in the system except for sensors data which has its own set of commands as described in the Sensors Board Commands section below For instance the GPC can issue this command to request battery voltage and current monitoring data from the servo board The data field of a BCMD_TELEM_FETCH packet is empty the list of data registers that are read back in a reply to a BCMD_TELEM_FETCH request is programmed into each board Electric Owl Final Report 60 CHAPTER 3 FINAL DESIGN Command Packet Type Command Byte Description BCMD_GPCAVR_WHOAMI BCMD_GPCAVR_BOARDID BCMD_SEND_DLPACKET BCMD_MATLBOX_PEEK BCMD_MATLBOX_POP BCMD_MATLBOX_CONTENTS BCMD_TELEM_FETCH BCMD_TELEM_REPLY BCMD_SENSORS_FETCH_HIRATE BCMD_SENSORS_REPLY_HIRATE BCMD_SENSORS_FETCH_LORATE BCMD_SENSORS_REPLY_LORATE BCMD_SENSORS_FETCH_AHPRS BCMD_SENSORS_REPLY_AHPRS BCMD_SERVO_SETSERVOS 0x07 0x08 0x09 OKOA OxOB OxOC 0x14 0x15 Ox1E Ox1F 0x20 0x21 0x22 0x23 0x28 ARM queries GPC AVR for board ID Reply to ARM board ID request Send downlink packet over radio Get message from radio mailb
118. e field that specifies the version of the uplink protocol in use See the paragraph in Electric Owl Final Report 71 CHAPTER 3 FINAL DESIGN Bit Offset 0 7 8 15 16 23 24 31 0 Protocol Signature MAC32 32 MAC32 Sequence Number 64 Sequence Number Packet Type Data 96 Data Figure 3 5 Byte structure of an uplink packet protocol signatures in section for more information Message Authentication Code The uplink protocol provides a mechanism for verifying the authenticity of received uplink commands in the form of a 32 bit message authentication code MAC attached to each uplink packet Matching encryption keys are stored on the UAV and on the ground computer When the ground computer sends an uplink packet it uses its key and cryptographic hashing algorithm to produce a 32 bit digest of the contents of the uplink packet and attaches this digest to the packet as the MAC When the plane receives an uplink packet it uses its key and the same hashing algorithm to produce its own digest of the uplink contents which is then compares to the MAC sent with the packet If the values match the packet is very likely to have come from the ground computer In addition to being used for authenticity verification the MAC also plays the role of the 16 bit CRC checksum in the downlink protocol If a transmission error occurs the digest computed onboard the plane will very probably not match the sent MAC enabling s
119. e modifications to the autopilot to try and fix the oscillating behavior that had been observed Specifically the autopilot code was altered to try and maintain a fixed heading for the aircraft instead of a fixed horizontal path as was done previously After performing a successful short flight test at a nearby location to see if the changes looked like they would work the team traveled out to Dick Scobee Field on March 19 2011 try a longer flight test and gather more data Additionally the team had finished calibrating the airspeed sensors and installing a pitot tube in the plane s wing so the team hoped to use this flight test to collect airspeed data for the first time As in the flight test that was conducted on March 6 the team had one of the experienced pilots at the field fly the plane to a reasonable altitude and engage the autopilot The plane was programmed to try and maintain its last heading just prior to the transition to autopilot The autopilot performed well and the magnitude of the oscillation in the plane s heading while under automatic control appeared to have been reduced substantially from the previous flight test With some advice from the pilot about the plane s handling the team adjusted some of the control constants in the autopilot feedback loop and conducted a second flight With these improvements the autopilot performed even better maintaining its heading with even less oscillation than before As with the previous
120. e performed almost simul taneously improving the sampling rate A documented erratum of the ATXMEGA32A4 forces the firmware to flush the ADC pipeline for 16 reads every time one of the multiplexed inputs is changed before the reading becomes stable DC Sensors The Honeywell HMC5843 is a digital DC three axis magnetometer This sensor has the correct sensitivity to detect the Earth s magnetic field The direction of the field in all three axes is used to determine the aircraft s heading and its absolute orientation relative to the Earth This has the 8 bit 12C address 3C and 3D depending on whether the master is sending or receiving from the sensor The firmware on the AVR is responsible for reading all of the registers on the chip regularly Electric Owl Final Report 27 CHAPTER 3 FINAL DESIGN Signal Channel Part Description GyroX ADC1 LPR530AL X axis gyroscope GyroXY_VRef ADC2 LPR530AL XY gyroscope reference GyroY ADC3 LPR530AL Y axis gyroscope P AIRSPEED ADC4 MPXV70002DP Differential pressure airspeed GyroZ ADC5 LY530ALH Z axis gyroscope GyroZ VRef ADC6 LY530ALH Z gyroscope reference AccelX ADC8 ADXL335 X axis acceleration AccelY ADC9 ADXL335 Y axis acceleration AccelZ ADC10 ADXL335 Z axis acceleration Table 3 1 Microcontroller ADC pin assignments on Sensors Board Rev 03 The BMP085 is a digital DC absolute pressure sensor from Bosch The absolute pressure in the aircraft decays exponentially with altitud
121. e vector roll radians CH STATE VEL X OxD6 State vector x velocity CH STATE VEL Y OxD7 State vector y velocity CH STATE VEL Z OxD8 State vector z velocity CH STATE GNDSPD OxD9 State vector ground speed CH STATE AIRSPD OxDA State vector air speed CH RADIO ERRCNT OxEO Radio error count CH FP STEP OxFO Flight plan step CH GLIDE HDG OxF1 Desired glide heading Table 3 10 Telemetry channel types and corresponding marker bytes Flight Plan Query Replies The other types of downlink packets are used as replies to queries from the ground computer about the state of the flight plan currently stored on the GPC TheDL TYPE PIR READ packet type is used to reply to uplink packets of type UL TYPE PIR READ see section 3 5 3 and have a data section consisting of a single byte which holds the number of the current step Similarly the DL TYPE STEP READ packet type is used to reply to uplink packets of type UL TYPE STEP READ see section 3 5 3 The data section of a DL TYPE STEP READ packet consists of a flight plan step laid out as specified by the flight plan mechanism see section Electric Owl Final Report 70 CHAPTER 3 FINAL DESIGN 3 3 3 followed by a single byte that is the number of the step that was read For more information about flight plans see section 3 3 3 3 5 3 Radio Uplink Protocol The radio uplink protocol specifies the structure of communications sent from the ground com puter to the UAV Import
122. egins with a two byte protocol signature After the signature is a byte that specifies the size of the data section in bytes Since this field is one byte the data section of a downlink packet may be anywhere from 0 to 255 bytes in size The size byte is followed by a two byte CRC checksum sent in big endian order Like the CRC checksums used in the bus protocol the checksum is used by the ground computer to check for transmission errors in received packets After the CRC is a byte that specifies the packet type analogous to the command byte for bus packets The packet type byte completes the header and the rest of the packet consists of data Electric Owl Final Report 66 CHAPTER 3 FINAL DESIGN Note that unlike the bus protocol the downlink protocol does not reserve any special bytes for frame delimiters etc These constructs are defined handled by separate protocol layer used for communication with the radio board s XTend radio module see sections 3 1 3 and 3 2 4 Before being sent to the radio downlink packets are wrapped using the XTend protocol framework At the receiving end received packets exit the radio encased in the XTend headers which are stripped away to expose the underlying downlink packet For more information about the XTend protocol see the datasheet for the XTend radio module 15 Bit Offset 0 7 8 15 16 23 24 31 0 Protocol Signature Data Size CRC16 MSB 32 CRC16 LSB Packet Type Data
123. eing programmed GPC Board gpc Radio Board radio Servo Board servo Sensors Board sensors When these changes have been made save the file 3 Build the board ID writing program by running make build avr write boardid hex in the software majortom directory 4 Plug the board to be programmed into the backplane Power the backplane using the shore power cable 5 Connect the AVR programmer to a USB port on the PC and to the appropriate site on the target sensors board Write the board ID writing program into memory on the board s AVR by running avr program sh build avr write_boardid hex at the command prompt inside the software majortom directory Electric Owl Final Report 120 APPENDIX A USER S AND SAFETY MANUAL 6 At this point the board should be programmed with its new board ID To see that check that the write was successful use an RS 485 transceiver cable to listen to traffic on bus 2 The program will continuously stream out the ASCII hexadecimal representation of the new ID on that bus Alternatively use the avrdude program s terminal mode to examine the contents of the EEPROM directly by connecting an AVR programmer to both the target board and the PC and running avr avrdude terminal sh at the command prompt inside the software majortom directory This will open up an interactive avrdude terminal session for the sensors board AVR Run the command dump eep
124. elemetry data Multi byte telemetry data values are stored in the packet in big endian order Possible values for the telemetry channel codes are given in table 8 10 Most of these codes are currently used by the existing system but a few such as the CH_MOTOR_TACH and CH_MOTOR_CURRENT channels have been added in anticipation of additional features a motor tachometer and current monitor in the case of the two explicitly mentioned As an example a telemetry packet containing all accelerometer data would have a data field that begins with the CH_ACCEL_AXIS1 marker followed by two bytes of data for accelerom eter axis 1 MSB first Next would come the CH_ACCEL_AXIS2 marker followed by two bytes of data for accelerometer axis 2 Following this would be the CH_ACCEL_AXIS3 marker and the data for accelerometer axis 3 Channel Byte Description CH_HVBATT_VOLTAGE 0x00 High voltage battery voltage CH_LVBATT_VOLTAGE 0x01 Low voltage battery voltage CH_HVBATT_CURRENT 0x02 High voltage battery current CH_LVBATT_CURRENT 0x03 Low voltage battery current CH_ACCEL_AXIS1 0x04 Accelerometer axis 1 CH_ACCEL_AXIS2 0x05 Accelerometer axis 2 CH_ACCEL_AXIS3 0x06 Accelerometer axis 3 CH_GYRO_AXIS1 0x07 Gyroscope axis 1 CH_GYRO_AXIS2 0x08 Gyroscope axis 2 CH_GYRO_AXIS3 0x09 Gyroscope axis 3 CH_MAG_AXIS1 OKOA Magnetometer axis 1 CH_MAG_AXIS2 OxOB Magnetometer axis 2 CH MAG AXIS3 OxOC Magnetometer axis 3 CH AIRSPEED OxOD Airspeed reading CH MOTOR T
125. encies not listed in Table A 1 that will also need to be installed e g Open OCD requires 1ibFTDI and libconfuse to run Electric Owl Final Report 114 APPENDIX A USER S AND SAFETY MANUAL Aside from the packages listed in Table lATlEXand doxygen are required to build some of the project documentation Any of the binary packages provided for most Linux distributions should suffice to satisfy these dependencies A 3 Programming the Circuit Boards This section gives the procedures for writing programs into the flash memory of the microcontrollers on the circuit boards A 3 1 AVR Microcontrollers Programming the AVR microcontrollers on each board requires the following e The target board to be programmed e The program to be flashed in the form of a hex file This should be produced automatically when the program is built using the project make scripts e One backplane board with at least one RS 485 connector and at least one row of circuit board connection headers e One AVR programmer e One shore power cable e One PC with all necessary software dependencies installed a copy of the project Git repository and at least one USB port To program one of the AVRs use the following procedure a Take the backplane board and insert the target board to be programmed into an available row of circuit board connection headers Electric Owl Final Report 115 APPENDIX A USER S AND SAFETY MANUAL
126. eness and as a convenience for the user In addition to recording all UAV communications into a log file the application can read ina previously recorded file and plot the aircraft s track in two dimensions as described in section 3 4 3 3 5 Communications Protocols In addition to the protocols used to communicate with the various peripherals on each board communication between the different parts of the system is accomplished using several custom designed protocols This section describes these custom protocols and how they operate 3 5 1 Bus Protocol The bus protocol defines the mechanism for communication between the different types of circuit boards over the system s 1 megabit RS 485 bus Delimiters and Escape Bytes The basic unit of bus traffic is the packet or frame which is a sequence of bytes structured in the appropriate manner for transmission over the bus see Packet Structure below The packets can be of variable length to accommodate data payloads of various sizes To make it easy to determine packet boundaries the bytes 0x7E and 0x81 are reserved for use as frame delimiters and may not appear anywhere inside a bus packet including the headers Prior to sending a packet the byte 0x7E is sent to indicate the Electric Owl Final Report 58 CHAPTER 3 FINAL DESIGN start of a new frame After the last byte of the packet s data section is transmitted 0x81 is sent to mark the end of the current
127. erface was used on all of the boards to reduce headaches due to incompatibilities and additional parts From the four power lines high current diodes are used to draw power from all four without any single failure pulling the other power lines low The standard hardware on each board also includes National Semiconductor switch mode power regulators to supply local 5 V and 3 3 V power rails This choice of power supply is capable of driving all of the necessary components on all four boards Because of the choice of components for the board power supplies the functional voltage on the power supply rail can range from 10 V to 15 V 3 1 1 Backplane A front view assembly diagram of the backplane is shown in Figure This board serves to connect the other types of boards both with each other and with various debugging tools including a DC shore power supply and bus debugging terminals Although the backplane contains no active components its design heavily dictates that of the other boards A full list of these components is listed in Electrical connection The five lines of each bus contain two ground lines on the outside pair with a 12 volt power supply line in the middle The inner pair of lines carries differential power and data This arrangement of the pins was chosen to minimize potential damage to the boards from improper connections In particular if the boards are inserted backwards only the polarity of the data pins is swapped which
128. es around twenty megabytes of RAM when loaded and is internally sorted using a tree data structure for efficient display of only the relevant data The G7T GPX and UAV telemetry files are all loaded and displayed in a similar manner The application loads all geographic path traces from a file and displays them as overlaid data as the user scrolls around Double clicking on the loaded file in the layer tree will cause the map view to center and zoom to see the whole contents of that one file The color of the displayed traces can be set on a file by file basis by right clicking on the name and going to the color selection dialog The GPS vector data source uses the open source gpsd program and library to interface to a GPS unit This GPS can be either connected directly to the computer the ground software runs on or remotely to another gpsd instance across a network The ground software displays a small icon indicating the current position reported by the GPS and also records the path history to display as a trace leading to the current position of the icon There is no provision for saving this trace as that function is easily accomplished using the tools which come with gpsd The UAV vector data source is similar to the GPS source except that its data comes from either the telemetry downlink radio or the X Plane flight simulator It displays an airplane icon on the map which rotates around as the live or simulated UAV heading changes This vector
129. for packets of this type is empty The GPC AVR replies with a BCMD_GPCAVR_BOARDID packet which has a one byte data field to hold the board ID Electric Owl Final Report 64 CHAPTER 3 FINAL DESIGN Field Type Name Description float32 alt Ellipsoid altitude in m float32 epe Estimated position error in m float32 eph Position error horizontal in m float32 epv Position error vertical in m uint16 fix Type of position fix float64 gps_tow GPS time of week in s float64 lat Latitude in rad float64 lon Longitude in rad float32 lon vel Longitude velocity in m s float32 lat_vel Latitude velocity in m s float32 alt vel Altitude velocity in m s float32 msl hght Height above mean sea level in m int16 leap_sec UTC leap seconds uint32 grmn_days Garmin days since 31 Dec 1989 Table 3 6 Layout of the data field for BCMD_SENSORS_REPLAY_LORATE packets Taken from the Garmin Device Interface Specification 1 Field Type Name Description uinti6 throttle Throttle servo setting uint16 aileron Aileron servo setting uint16 elevator Elevator servo setting uint16 rudder Rudder servo setting Table 3 7 Layout of the data field for BCMD SERVO SETSERVOS packets Note that the values must be sent in little endian order HITL Only Sensors Board Commands There are also two special packet types used for operating the system in HITL testing mode in which the GPC receives its sensors data from a computer runni
130. frame If a board needs to send a packet containing these values the offending bytes must be escaped prior to transmission Escaping is accomplished by first sending the byte 0x7D fol lowed by a second byte that depends on the value of the byte being escaped These values are given in table 3 2 For instance to send a data byte with value 0x7E one must send the sequence 0x7D Ox5E instead Special Byte Function Escape Sequence Ox7E Start of frame delimiter Ox7D Ox5E 0x81 End of frame delimiter Ox7D 0x51 0x7D Escape byte Ox7D Ox5D Table 3 2 Special bytes and escape sequences Packet Structure Bus packets have two major parts parts the header and the data section The layout of a bus packet is illustrated in figure 3 3 The packet header begins with a two byte CRC checksum sent in big endian order The next byte holds the ID of the board sending the packet and is followed by a byte with the ID of the destination board Following these the data length byte specifies the size of the packet s data field prior to the addition of escape bytes see Delimiters and Escape Bytes above Next comes the command byte which specifies what kind of data the packet is carrying The command byte is the last byte in the packet header Following the command byte there are the payload bytes which constitute the data being sent Bit Offset 0 7 8 15 16 23 24 31 0 CRC Checksum Source ID Destination ID 32 Data Length Comm
131. g all packets received from the system bus to the ARM for processing see Bus Passthrough above Because the ARM does not use a polling event loop as the basis for its interaction with peripheral devices the ARM must be signaled when it has been sent a complete packet Upon the completion of transmission to the ARM the GPC AVR toggles ones of the ARM s GPIO pins triggering an interrupt on the ARM that is picked up and handled by the ARM kernel Special Commands The GPC AVR board listens for the special bus commands sent to it from the ARM see section 3 5 1 They are called bus commands because they are defined as part of the bus protocol but these commands are never sent over the system bus e BCMD_GPCAVR_WHOAMI This is sent by the GPC s ARM microcontroller in order to as certain its board ID which is stored in the EEPROM of the GPC AVR The GPC AVR replies with a BCMD_GPCAVR_BOARDID packet containing the board ID 3 2 7 GPC Board ARM 3 2 7 1 System Master The software running on the ARM provides master timing of all system events By virtue of the command response nature of the bus protocol it is guaranteed that the GPC board will initiate all bus transmissions and the other boards will wait until a reply is demanded of them before transmitting In a future configuration with multiple GPC boards it is envisioned that each GPC would be the master of a different bus so that even without cross GPC synchronization
132. g datum is labeled an outlier and the remaining non outlier values are averaged together to form the final estimate which is sent to the autopilot If no datum is judged to be an outlier all three pieces of data are averaged together to form the final estimate The GPC keeps track of the number of outliers rejected for each sensor and can send these down to the ground computer over the radio with the rest of the telemetry Outlier detection in the three reply case is handled using the Dixon Q test at 90 con fidence 16 While not the most robust statistical criterion in general this test is good at handling very small sets of data and does not make any assumptions about the nature of the source distribution aside from its normality It is also straightforward to implement Redundant Low Rate Data Processing Redundant low rate data is handled in a different manner from the high rate data because performing averaging and outlier rejection on GPS Electric Owl Final Report 49 CHAPTER 3 FINAL DESIGN data is not appropriate Rather the GPC takes all sets of GPS data it receives and looks to see which one has the highest quality satellite fix and sends that to the autopilot GPS data from a unit with a 3D WAAS fix is preferred over data from one with just a 3D fix Data from units with no fix or only a 2D fix is discarded If multiple units are found to have the best fix data from them is chosen arbitrarily to be used as the input to
133. g i E 3G via E amp F 8 Luz Lang iu d gt S 0022 Y f 0t WorilSdls rs isa ee 2 TH HA isna JN 9a cLOAHS9NS en M tk Leer L SNQAH ESDA 0047 I f Gre s EE E i tK Eeer 1 90 ESN8 E LxLosng zu LP alz S J I A ws L 99A08ng W0r1LSd1S L o9Azsng vo 69 zo 19 e ad T gt lt 8 E ea S u3x1osng nl np np nu eat 00 2 W0r1LSd1S L lt HOontsng je rl eg B Exyosng lt 1 99ASNg pen ed ES Hose Lyd DI EDA osna Wor1isdls L 00A08ng J La 2LGAHS9NS LA 6 8 Z 9 S z L 158 I Report ina F Electric Owl 8 Jo z abed go UoISIA 1 SJEMPIEY pipoq onas JO JIJ wayos HOI 9 g auNnbi4 APPENDIX B SCHEMATICS AND CAD DRAWINGS 159 8 L 9 S t z L eDpug uJj r Ag NMYYA 30 20 39vd NOISIA3H qi qui ZO UOISJOA pIeog oA19S 49 0J10090J9 A OL 02H I c 4 do y ve ge 410 Iqg 13sSatu LOSOL LIWLX Lud 7g ZHN T FN T z L ye Viva Idd zoSO L 1V LX Od gg 029 L 99A HAV Idd tis 1 d t i pxusnH lt Zh 40d YOS LAKL 00X1 0090 3d gg gt PXLesng 24004 dnO 3400 40001 12000 ANOL i bo S
134. ground track or wind correction The motor and elevator are used in conjunction to Electric Owl Final Report 50 CHAPTER 3 FINAL DESIGN approach and maintain a desired altitude and airspeed e 2D Path This is similar to the waypoint mode except that the airplane attempts to fly a specific 2D line along the ground In order to maintain the desired ground path the airplane will automatically yaw to crab into the wind if required e Landing This is the most complicated type of step Similar to takeoff the step specifies the location of a runway centerline along the ground however in addition it incorporates a desired sink rate for the approach and a targeted touchdown point along the runway The vehicle is controlled to fly along the runway centerline in the horizontal dimension while maintaining the correct vertical approach speed and angle Once the vehicle is over the runway the motor is stopped and a flare pitch comes into effect This procedure has proven remarkably resilient to varying wind speed and direction in simulation There are currently five types of step completion criteria available e Never This is used for testing finishing a flight plan or for the final step in a contingency plan e Point cross This completion criteria is only valid for the Waypoint and 2D Path step types One difficulty is that the airplane can be expected to never follow a precise trajec tory arbitrarily close to the desired waypo
135. h it to Mars Traditional low cost orbital transit routes to Mars typically take several months in cold interplanetary space This environment can freeze components and irradiate electronic memory Once on Mars the probe must survive atmospheric re entry The aircraft would then need to unfurl and launch from midair 2 Light Propagation Delay The extreme distance between Mars and Earth causes one way a delay in any radio signal of between 10 and 20 minutes This delay is too extreme to al Electric Owl Final Report 12 CHAPTER 1 INTRODUCTION low any sort of manual control of the probe in flight the aircraft is almost certain to have impacted the terrain before notification even reaches a terrestrial operator Because of this fully autonomous flight is a necessity for an aerial Mars mission 3 Flight Infrastructure Mars lacks many of the amenities available to terrestrial aviation The constellation of satellites that enable GPS on Earth are not yet available on the Red Planet Furthermore there are no runways or refueling installations for the plane to return to when its internal power is exhausted 1 3 3 Component Failure High Radiation Environment The thin atmosphere of Mars does not have sufficient depth to shield the planet from space radiation Any Mars probe would need to be designed to function in this environment as well as to be able to survive the long journey in interplanetary space which features further rad
136. i and takeoff controllability The first prototype also had only one servo for controlling both ailerons Although this decreased drag it required the servo to be larger and specialized as well as decreased the volume available for payload The first prototype also had only one elevator surface driven by one servo The fuselage of the OWLbatross was destroyed during the first test of the sensor board because the center of gravity was too far aft Wind gusts were a contributing factor in the crash The motor batteries servos and avionics survived the crash largely unharmed The wing was slightly damaged and was retained as a spare Electric Owl Final Report 75 CHAPTER 3 FINAL DESIGN Because of the time and expense of assembling and covering the balsa airframe a second backup prototype the FOWLcon was purchased in an almost ready to fly ARF condition from the manufacturer Replacement parts for the ARF prototype are quite inexpensive with the entire fuselage costing a mere 40 Several spare fuselages and tail assemblies as well as one spare wing are kept on hand in case the originals are damaged in a crash After the destruction of the first prototype it was determined that modifying subsequent prototypes to have a tricycle landing gear would take too much time and would distract from the immediate focus of the project so the second and current prototype retains its stock conventional landing gear Repairs C
137. iation hazards Radiation can adversely affect the operation of electronics by causing memory errors and erroneous state changes Although radiation hardened chips exist they do not fully prevent these problems Component Failures In the harsh environment of space component failures must be antic ipated Failure of propulsion motors control surfaces and flight avionics should be considered likely NASA s unmanned probes typically sport redundant systems particularly in the elec tronics however a failure of the primary computer leaves the system in an unsafe state if the level of redundancy is insufficient as has been seen in the Mars Reconnaissance Orbiter 5 6 Electric Owl Final Report 13 CHAPTER 1 INTRODUCTION 1 4 The Project In order to explore some of the issues that that would need to be considered in the design of a Mars UAV the members of Team Electric Owl decided to use their capstone senior design project to design build and test a set of UAV flight control electronics avionics subject to some of the constraints faced by an actual Mars UAV Specifically the team aimed to produce a lightweight avionics package for a fixed wing aircraft that could accommodate redundancy in the various system components to improve the system s overall fault tolerance Electric Owl Final Report 14 2 Design Strategy 2 1 Fault Tolerant Mars Capable Avionics In order to better define the project
138. iciently large value The kernel does contain some checks to help detect stack overflow Scheduling and Timing The scheduling algorithm is designed to accommodate the real time requirement of the main autopilot thread while also allowing other threads to receive CPU cycles The scheduler is capable of waking up the autopilot thread to run a new calcu lation cycle every 40 milliseconds with vanishing jitter and zero long term systematic delay errors Priority is handled using a system of reservations rather than static or dynamic priority numbers Each thread is configured with a CPU percentage which could be from 0 to 100 Electric Owl Final Report 44 CHAPTER 3 FINAL DESIGN The sum of all percentages must be less than 100 Over the course of one 40 millisecond cycle any thread which has not yet used up all its reservation is given priority over a thread which has already used its guaranteed time The autopilot thread is configured with approxi mately a 50 reservation which is several times the amount of CPU cycles it needs for any given 40 millisecond cycle This way so long as the autopilot is ready to run the kernel will give it priority Other threads have been given small reservations such as 10 or 0 A small positive number will ensure that the thread does not starve During one calculation cycle the autopilot thread both communicates with other boards and runs computations During the communication the thread wi
139. ide the ground software select Activate from the UAV menu If everything is set up correctly the software should be receiving telemetry that contains the gyroscope values from the rotating assembly Note that it is extremely important that this step be performed after the assembly is set in motion and not before 18 After collecting data for 30 60 seconds de select the Activate option in the UAV menu of the ground software stop the rotating assembly and disconnect the nickel cadmium battery A telemetry file should have been created in the tmp directory with the data downlinked while the assembly was in motion Save this file somewhere where it can be accessed for the data pre processing step that follows Make sure that the filename indicates which axis was being measured Electric Owl Final Report 136 APPENDIX A USER S AND SAFETY MANUAL 19 Repeat steps for each remaining orientation 20 Repeat steps 15 and 17118 with the boards in a stationary non rotating configuration This measurement will be used to correct for zero offsets in the gyroscope values Save the data file somewhere where it can be accessed for the data pre processing step that follows Make sure that the filename indicates that the measurement was made with the boards stationary You should end up with four telemetry logs three that each have rotational data for one of the gyroscope axes apiece and one with stationary data t
140. ies of uplink packet joystick packets and packet types that are used for changing the plane s onboard flight plan The type of an uplink packet is determined by its packet type field Possible values for the packet type byte are given in table 3 11 Just as for bus and downlink packets new uplink packets can be defined by specifying new values of the packet type byte Packet Type Byte Description UL CMD JOYSTICK 0x10 Human input joystick control UL CMD STEP WRITE 0x20 Write flight plan entry UL CMD STEP READ 0x21 Read back flight plan entry UL CMD PIR WRITE 0x22 Set current flight plan step UL CMD PIR READ 0x23 Read which flight plan step is currently executing Table 3 11 Downlink packet types and corresponding identification bytes Joystick Packets Joystick packets have type UL CMD JOYSTICK and are sent when the plane is being flown under PC joystick control from the ground computer The data section of these packets contain servo output values to be used directly by the servo board for control ling the servos The servo values are stored as 16 bit unsigned integers in big endian order and are laid out as shown in table Electric Owl Final Report 73 CHAPTER 3 FINAL DESIGN Field Type Name Description uinti6 throttle Throttle servo setting uint16 aileron Aileron servo setting uint16 elevator Elevator servo setting uint16 rudder Rudder servo setting Table 3 12 Layout of the data field for UL_CMD_JOYST
141. ihood of the polling loop missing GPS bytes is reasonably small Failure here will result in the loss of a single GPS packet which seems acceptable A state machine is used to process the Garmin binary protocol for GPS data which is a thin wrapper around raw C structures that are transmitted as binary When a new data byte arrives from the GPS it is copied into a GPS packet construction buffer Garmin protocol headers and frame delimiters are processed and stripped as they arrive and Garmin escape bytes are unescaped before being added to the buffer Data packets other than the PVT location packets are ignored at present but satellite specific data is available Computation of the Garmin protocol checksum is advanced as each byte arrives When a complete packet is received its Garmin checksum is verified and if the checksum passes the GPS data is saved Electric Owl Final Report 41 CHAPTER 3 FINAL DESIGN in memory where it awaits request by the GPC board Sensor Calibration Calibration values for all of the sensors are stored in the EEPROM mem ory unit on the sensors board AVR except for the BMP085 which comes with factory loaded calibration values that are read during the 12C startup sequence The sensors firmware uses the stored calibration values to remove zero offsets and convert the sensor outputs into the units required by the autopilot algorithm For more information on sensor calibration see sec tions and 3 2 6 GP
142. ile The caltest m script is used for analyzing calibration data and the computed calibration models before the user is ready to commit to storing the values in the EEPROM on the ac tual sensors board for use It accepts a single string argument that indicates which type of calibration is to be performed Electric Owl Final Report 142 APPENDIX A USER S AND SAFETY MANUAL e accel Perform accelerometer calibration e mag Perform magnetometer calibration e gyro Perform gyroscope calibration e airspeed Perform differential pressure sensor calibration The paths to the data files used for calibration are coded into the script and must be changed before the script can be used to look at new set of data To use caltest m to analyze calibration data use the following procedure 1 Decide which sensor data to analyze and locate all of the corresponding data files 2 Edit the caltest m script file in the software majortom src utils directory At the top of the caltest function are some variables that hold the paths to the calibration data files e acc_dat_file Path to accelerometer calibration data file after pre processing with cd2matlab e mag_dat_file Path to magnetometer calibration data file after pre processing with cd2matlab e gyro_stat_dat_files Cell array of paths to files with gyroscope data extracted from the telemetry logs generated with the gyroscopes a
143. in the given number of seconds the error will trigger The user can configure the contingency plan step to shut off the motor to terminate further movement of the vehicle e Orientation error This can detect several types of errors including the exceeding of preprogrammed pitch or roll limits and the airplane attempting to go backwards during a Takeoff 2D Path or Landing step e Too long This condition will trigger if the current step has been executing for longer than a given time e Too low This condition will trigger if the airplane falls below a trigger altitude This may happen if for instance the main propulsion battery is drained and the airplane can no longer keep itself in the air 3 4 Houston Ground Software A graphical PC application has been designed to run on a ground support laptop and provide various real time and off line support functions for the UAV system The core functionality consists of a fast multithreaded Internet enabled two dimensional map viewer with support for Electric Owl Final Report 52 CHAPTER 3 FINAL DESIGN several vector and raster geo referenced data formats This software base was written prior to the 2010 2011 school year During the current school year the application was extended to add an interface for receiving displaying and recording real time telemetry from the UAV Loading a previously recorded telemetry file to view the two dimensional flight track is also
144. ing to the servos with the assistance of the team s NASA mentor David Fuson suggested that the re peated loops may have been inadvertently induced by the pilot while he was trying to save the plane Though the team was unable to gather any data on the performance of the autopilot the sensor telemetry gathered during the flight seemed to suggest that the system was correctly processing the data from the redundant sensors boards 4 4 6 Redundant Sensors Flight Test Il 04 02 2011 Since the team did not get the information it wanted during the flight test on March 27 the team conducted a second flight test on April 2 with the same objective to demonstrate the autopilot s ability to maintain a fixed heading while handling data from redundant sensors inputs As in Electric Owl Final Report 94 CHAPTER 4 TESTING AND RESULTS sas N 0 oO J bo 0 Ka Ner bd J qu O d 37500 37550 37600 37650 Time of day s Figure 4 1 Heading lock telemetry from second flight on 04 02 2011 The blue line indicates the plane s actual heading The gray regions indicate parts of the flight for which the autopilot was active and the orange lines indicate the plane s desired heading during those times the flight test on March 19 the plane was programmed to try and maintain its last heading just prior to the transition to autopilot Once again the team enlisted the services of Mr Keith Klix for help with flyi
145. int there must be some definition of close enough The original version of this criterion measured how quickly the angle from the airplane to the waypoint was changing to determine when the airplane had passed through a region close to the point however in recent testing this measure gave frequent false positives due to an unrelated packet dropout problem which affected the timebase It has been rewritten to work for only the 2D Path step by comparing the airplane s po sition to a line running through the destination waypoint perpendicular to the desired 2D ground path This new test does not depend on time and proved reliable This change effectively deprecates the Waypoint step type for now Electric Owl Final Report 51 CHAPTER 3 FINAL DESIGN e Above Match Below Elevation These three completion criteria simply measure if the plane has reached above crossed in either direction or fallen below a specified eleva tion This is used if the planner would like the UAV to change altitude and switch to the next phase of the plan as soon as the altitude change is finished There are currently four types of error conditions each of which can be enabled or disabled for any given flight plan step e Altitude attainment failure This error condition is intended to be used in conjunction with the Takeoff step type It has data fields for an altitude and a timeout timer If the vehicle has not reached the specified altitude
146. ipsoid can be deter mined The coordinates of the centroid of this ellipsoid gives the zero offsets for each of the magnetometer axes and the lengths of the ellipsoid axes can be used to adjust the relative scaling of the magnetometer axes To do the curve fitting the team cast the problem as a non linear least squares optimization problem in six dimensions three for the coordinates of the centroid three for the axis lengths and used MATLAB s 1sqnonlin routine to solve for the optimal set of parameters 1sqnonlin uses a trust region method to perform optimization For more information see the MATLAB manual page for 1sqnonlin and the papers and 20 Gyroscopes Calibration of the gyroscopes requires a souce of constant angular rotation The team procured a standard 333 RPM record player for this purpose measured its rate of rotation and took gyroscope measurements with the boards placed on the rotating plat form To avoid the need to hook cables up to the rotating assembly to tap into the bus the measurements were sent wirelessly to a PC using the radio link Two measurements were taken for each gyroscope axis one with the system rotating about the axis at the turntable speed and one with the boards in a stationary non rotating configuration The team used these data to generate a linear model for the behavior of the Electric Owl Final Report 88 CHAPTER 4 TESTING AND RESULTS gyroscopes Relative Airspeed To calibrate the
147. is not receiving any commands from a manual RC transmitter This should cause the aircraft to enter a gentle glide and reduce the risk of damage both to the plane and to objects on the ground should the plane eventually crash The status of the manual transmitter is assessed using the value of the manual control input line see Servo Inputs From RC Transmitter above The autopilot is deemed to have stopped responding if the board goes more than 200 ms without receiving a bus packet containing servo values Battery Monitoring As mentioned in section the servo board features hardware for monitoring voltages and currents of both the high voltage and low voltage batteries Once ev ery second the servo board AVR sets its ADC unit to begin conversions on the pins connected to this hardware The AVR then polls for these conversions to finish inside the main event loop and when they do it scales the values to have units of millivolts for voltages or milliamperes Electric Owl Final Report 36 CHAPTER 3 FINAL DESIGN for currents and then stores them in memory The GPC board can request the latest set of battery monitoring data by sending a BCMD_TELEM_FETCH command to the servo board 3 2 4 Radio Board Bus Interface The radio board listens for the following bus commands see section 3 5 1 e BCMD_TELEM_FETCH The board will reply with a BCMD_TELEM_REPLY packet containing the voltage level on each bus e BCMD_SEND_DLP
148. ith frame delimiters and escape sequences The DMA channel for the transmit bus is then switched from receive mode to transmit mode and the buffer is handed to the DMA unit to be written out to the bus This prevents the system from using any CPU time transmitting bytes allowing the microcontroller to continue processing other events while transmissions are occurring Electric Owl Final Report 33 CHAPTER 3 FINAL DESIGN 3 2 3 Servo Board Bus Interface The servo board listens for the following bus commands see section 3 5 1 e BCMD_TELEM_FETCH The board will reply with a BCMD_TELEM_REPLY packet containing the voltages and currents for both the high voltage and low voltage batteries the outputs being sent to every servo and whether or not the plane is currently being flown under manual override e BCMD_SERVO_SETSERVOS The board will set the servos to the values specified in the packet These are used when controlling the plane via autopilot Servo Outputs The primary job of the servo board firmware is to ensure the correct setting of the servo outputs In particular this entails ensuring that the servos are supplied with voltage pulses of the appropriate width at a regular rate This is accomplished by manipulating the board s 4017 decade counter see section 3 1 2 Each output of the decade counter is connected to a different servo When it is time to send a voltage pulse to one of the servos its output on the
149. ked up by the Houston ground software which is listening to traffic on the bus as part of its HITL testing mode see section 3 4 Houston then retrieves airplane state data from X Plane wraps it in a BCMD SENSORS REPLY AHPRS packet and sends it on to the GPC The GPC takes the data it has received and inputs it into the autopilot algorithm which decides how to manipulate the control surfaces to best adhere to the programmed flight plan The GPC Electric Owl Final Report 89 CHAPTER 4 TESTING AND RESULTS then sends these manipulations out over the bus in the form of a BCMD_SERVO_SETSERVOS packet Houston picks this up and forwards the data to X Plane which uses this information and its internal flight model to update the state of the simulated aircraft The team made extensive use of the HITL test framework for trying out changes to the autopilot prior to actual flight tests and for tuning autopilot control loop constants to improve the dynamic behavior of the aircraft This required the team to construct a simple X Plane model of the prototype Senior Telemaster used as the test airframe Most importantly the team used the HITL framework to demonstrate the ability of the au topilot to successfully follow a series of waypoints For instance in one particular test the GPC was programmed to fly repeatedly in a box like pattern through a series of waypoints whose coordinates form the four corners of a rectangle The plane exhibited s
150. kes the name of the data file to be processed as an input ar gument and writes the processed data to standard output For instance if raw accelerometer data was saved to raw_data dat in the software majortom build pc directory it can be processed by running cd2matlab raw_data dat gt caldata_accel dat in the software majortom build pc directory The processed data will be written to the file caldata_accel dat Process each data file generated in the data collection step in this manner For the ac celerometer and magnetometer data this means the one file that the procedures for each of these sensors generate For differential pressure data the data file from each individual flow rate must be processed separately Be sure to give each processed data file a different name that describes its contents and save them for use in the next step A 7 2 2 Gyroscope Data The gyroscope data must be extracted from telemetry logfiles generated during the data col lection process This is accomplished by using the teldecode program to read the telemetry log and the Unix utilities grep and cut to extract the relevant values For the purpose of this example it is assumed that the gyroscope telemetry logs are con tained in the files gyro_axis1_pitch log gyro_axis2_roll log gyro_axis3_yaw log and gyro_stationary log and that they have been moved to the software majortom build pc directory for processing First if necessary build the teldecode
151. l pressure sensor used for taking airspeed data The BMP085 static pressure and temperature sensor from Bosch see section 3 1 4 comes from the factory loaded with calibration values which the sensors board reads as part of the 12C startup sequence It may be desirable to perform additional calibration but procedures for doing this have not yet been developed The calibration procedures make use of the ground software in addition to several other software utilities For a description of these utilities see section A 6 A computer with MATLAB installed is required to run the calibration scripts Electric Owl Final Report 125 APPENDIX A USER S AND SAFETY MANUAL A 7 1 Step 1 Data Collection The first step in the calibration process is to take calibration data The procedure varies for each type of sensor A 7 1 1 Accelerometers The procedure for acquiring accelerometer calibration data requires the following materials e One backplane board with at least three RS 485 connectors and at least one row of circuit board connection headers Make sure that no circuit boards are plugged into it Sensors board with accelerometers to be calibrated One shore power cable Two RS 485 transceiver cables One AVR programmer One PC with all necessary software dependencies installed a copy of the project Git repository and at least two USB ports To take accelerometer calibration data use the following procedure 1 Ope
152. l socket and the other end into one of the RS 485 jacks on the backplane 5 Connect an AVR programming header to a USB port on the PC and to the appropriate site on the target sensors board Write the calibration data dump program into memory on the sensors board AVR by running avr program sh build avr main_sensors03 hex at the command prompt inside the software majortom directory If the programming of is successful unplug the AVR programmer from the PC and the sensors board and set it aside Otherwise fix any errors that arise and make sure that the board is programmed before continuing 6 Disconnect the shore power cable 7 Connect the XTend ground module to a USB port on the PC Be sure to note the device node that it is assigned For convenience it will be assumed for the remainder of this procedure that the radio has been assigned dev ttyUSBO 8 Load up the Houston ground software by running wx GroundControl at the command prompt inside the software houston directory If necessary build the ground software first by issuing make wx GroundControl Electric Owl Final Report 134 APPENDIX A USER S AND SAFETY MANUAL inside the same directory 9 Inside the ground software open the UAV menu and select I O Configuration In the dialog box that appears click on the Network tab Make sure that the device node and serial speed for the XTend radio are correct If you change a
153. lities the team created in addition to the Houston ground control software to help with processing telemetry data and other tasks teldecode The teldecode utility is used for processing logfiles generated by Houston In particular it is used for extracting and displaying downlinked telemetry data but it can also extract any of the other data stored in the logfile including logged RS 458 bus packets teldecode reads data from standard input and writes to standard output so it can be easily used as part of a data processing pipeline For instance running teldecode lt telemetry log grep gyro_axisi cut f 2 d will produce a list of all downlinked pitch gyroscope data stored in telemetry log tel2csv pl tel2csv pl is a Perl script which is used in conjunction with teldecode to convert logged telemetry data into the comma delimited CSV format so that it can be imported into a spreadsheet program for further analysis Like teldecode tel2csv reads all of its data on standard input and writes the results of its processing to standard output For example the command pipeline teldecode lt telemetry log tel2csv pl gt teldata csv will dump the telemetry data stored in telemetry log to the file teldata csv busmonitor and busmonitor2 busmonitor and busmonitor2 are both programs that can be used for monitoring traffic traveling on one of the four RS 485 system buses busmonitor writes all of the traffic it observes to sta
154. ll go to sleep to wait for the bus I O to complete While the autopilot is sleeping the scheduler will allow other ready threads to run until the autopilot UO completes and the autopilot thread wakes up again The kernel timer subsystem is designed to provide high granularity for timer events without wasting lots of CPU cycles with frequent clock interrupts One hardware timer is configured to operate in a free running mode and provides a reliable reference synchronized to the clock crystal with no drift It only fires an interrupt infrequently upon overflow A second hardware timer operates in a countdown mode and is only switched on when there is an event pending soon It is preloaded with the exact amount of delay needed between now and the next event In this way a timer interrupt only fires when a requested event is supposed to occur and provides near exact delay straight to the requested time Interprocess Communication The interprocess communication facility of the kernel was inspired by the minimalism of the L4 microkernel The kernel does not maintain variable length message queues or even buffer message contents inside the kernel at all There are only two system calls ipc_send and ipc_recv A valid message target identifier is simply a pointer to the target thread If the target thread is ready to receive a message then the message is communicated immediately and the sending call returns Otherwise the sender Electric Owl
155. m to decide how the plane should act to meet its next objective It then sends commands to the servo board to make the Electric Owl Final Report 29 CHAPTER 3 FINAL DESIGN appropriate manipulations of the plane s control surfaces A front view assembly diagram of the GPC board is shown in Figure C 5 A full list of the components is given in Atmel AT91SAM7S256 ARM Microprocessor When selecting a chip for the system s main computer the team had three requirements First the device needed to be highly integrated with a substantial amount of built in flash memory and facilities such as direct memory ac cess DMA and serial controllers Second it needed to be capable of running the autopilot algorithm fast enough to control the plane Simple estimates showed that this would require roughly ten thousand floating point operations per second Finally the chip needed to have a set of readily available software development tools Based on these considerations the team selected the 32 bit Atmel AT91SAM7S ARM microprocessor as the system s centerpiece This chip features software emulated floating point arithmetic and runs at a 50 MHz clock rate which is more than sufficient to run the autopilot control loop at the required update rate of 25 Hz Furthermore the chip has 256 KB of internal flash which easily holds all of the firmware code It has two integrated serial ports and has excellent DMA support with two DMA channels for e
156. mer was funded by the team members directly D 2 Expenses The expenses for the semester are detailed in Table D 1 Date Description Cost in USD October 30 AVR Microcontroller Programmers 68 00 November 6 RPSMA to SMA Connectors for Telemetry Radio Antenna 17 79 January 7 AMA Memberships 145 00 January 10 Spare Parts for Second Prototype Airframe 345 95 January 12 Anemometer 107 10 January 20 Panel 02 PCBs from Advanced Circuits 643 90 January 26 Backplane Headers 34 25 January 28 Components for Panel 02 455 83 January 28 Antennas for Telemetry Radio 20 31 January 29 Servo Y Connectors and Transmitter USB Interface 90 85 February 15 Pitot Static Tubes 59 85 March 26 Connectors for Pitot Static Lines 26 79 March 26 720p Video Camera for Second Prototype 186 27 Total 2201 89 Table D 1 Expenses for the 2010 2011 School Year Electric Owl Final Report 210
157. mmercial airliners 18 This plan calls for redundant placement of all of the boards rather than only the sensors This system would resemble the one shown in 2 1 Servo Boards With the design of the servo board it should be possible to drop in multiple boards although this requires redundant external control surfaces which significantly adds to the weight of the airframe Multiple power supplies should be supported transparently Radio Boards If the code for the bus master is changed somewhat it should be possible to add a second radio board in a failover capacity where only one functions until failure is reported With the radio board loss of signal can be interpreted as a failure and the backup system can be activated GPC Boards With significant software upgrades up to four GPC boards could be expected to work together in lockstep operation based on the design of the Space Shuttle 9 flight computer architecture In this situation each of the GPC boards controls a bus and operation proceeds with a single bus until the non primary boards detect an error and then disable the faulty GPC Four GPC boards were selected to provide failsafe fail operational behavior Specifically the first failure is easily detected as a difference between one computer and the other three Note that two pairs of computers reaching two separate conclusions is extremely unlikely be cause it depends on at least two computers failing in identical ways
158. n lines in that template Be cause MATLAB s native text processing facilities are poor the gen_cal_prog m calls the sed program to accomplish this task This means that sed must be present on the system for this procedure to work 3 Compile the sensors03_write_caldata c program by running make build avr sensors03_write_caldata hex at the command prompt inside the software majortom directory 4 Write the sensors03_write_caldata hex program into flash on the target sensors board AVR using the standard AVR programming procedure given in section To see that check that the write was successful use an RS 485 transceiver cable to listen to traffic on bus 2 The program will continuously stream out the calibration values just written on that bus Alternatively use the avrdude program s terminal mode to examine the contents of the EEPROM directly by connecting an AVR programmer to both the target sensors board and the PC and running avr avrdude terminal sh Electric Owl Final Report 145 APPENDIX A USER S AND SAFETY MANUAL at the command prompt inside the software majortom directory This will open up an interactive avrdude terminal session for the sensors board AVR Run the command dump eeprom two or three times at the avrdude prompt to view the EEPROM pages that were written 5 Open the sensors03 h file and comment out the line defining the SENSORS_USE_RAW_VALS symbol mentioned in step 1 of the accelerometer calibr
159. n the map and in X Plane The user can also connect to the onboard bus in live mode to record a combined radio bus telemetry stream This has proved useful for debugging 3 4 5 Logging Format The log format output by the ground software shares some elements in common with the byte oriented protocol used for the onboard buses Specifically each packet of data is encapsulated using start and stop delimiter bytes with escaping of data bytes to avoid any ambiguity for these delimiters This encapsulation proved to be far more robust than the first version of the log format It has even enabled the capability to start and stop external analysis programs on the live telemetry stream without interrupting the recording by using the Unix tail f command Inside of each encapsulated log packet is a timestamp with microsecond level resolution a marker indicating what sort of payload is in the packet and then the payload The payload consists of either a telemetry downlink packet a bus packet a command uplink packet or Electric Owl Final Report 57 CHAPTER 3 FINAL DESIGN a raw radio packet The timestamp is added by the PC running the ground software The microsecond resolution enables the user to ascertain timings even on closely spaced bus packets Each time one of the UAV modes is activated the ground software creates a new telemetry log file to record data The file is named with the date and time it was created to ensure uniqu
160. n the sensors03 h source file in the software majortom src avr subdirectory of the project repository Near the top of the file within the first 30 lines should be a line containing a define SENSORS_USE_RAW_VALS preprocessor directive If this line is commented out comment it in and save the file Defining this symbol sets up the sensors firmware to use raw sensor values instead of trying to apply any calibration values that may already be stored on the device It also Electric Owl Final Report 126 APPENDIX A USER S AND SAFETY MANUAL ensures that the values are stored in a manner that is compatible with the calibration MATLAB scripts 2 Open the sensors03_take_caldata c source file in the software majortom src avr subdirectory of the project repository Near the top of the file is a line with a preprocessor directive that defines the symbol DATA_CAPTURE_BUS e g define DATA_CAPTURE_BUS 2 The value of this preprocessor symbol is a number between and including O and 3 that corresponds to the bus to which calibration data will be dumped for capture For exam ple define DATA_CAPTURE_BUS 2 sets bus 2 as the data capture bus Change this value to the desired bus number and save the file 3 Still in sensors03_take_caldata c near the top of the file is a line with a preprocessor directive defining the USE_MANUAL_DATA_CAPTURE symbol Make sure that this line is not commented out and save the file Defining the USE_MA
161. ndard output and is capable of outputting observed bytes either in raw binary form or in ASCll encoded hexadecimal busmonitor2 offers only Electric Owl Final Report 124 APPENDIX A USER S AND SAFETY MANUAL ASCll encoded hexadecimal output but displays the traffic in a more organized format using a simple ncurses based interface Unlike busmonitor busmonitor2 also parses the traffic into packets and even parses the packet headers allowing the traffic to be displayed as a sequence of packets instead of just as a stream of bytes These programs were useful for early debugging efforts but were largely superseded with the advent of the logging capabilities of the Houston ground control software and the teldecode log parser Nevertheless they still a few specialized uses For instance busmonitor is used in binary output mode for acquiring sensor calibration data see section A 7 cd2matlab cd2matlab is a utility for taking raw sensors calibration data dumps and convert ing them to the format expected by the MATLAB calibration scripts For more information on this utility see section A 7 A 7 Sensor Calibration Procedure This section describes the procedures for taking sensor calibration data using it to generate calibration values and loading them into EEPROM on the sensors board for application There are four types of sensors that must be calibrated the accelerometers magnetome ters gyroscopes and the differentia
162. ng L ec 99d OSIW LaXu 00X4 9090 24d ze FXuesng Z 9cO 909 b i C eed a HN U3X I sn u3xJesng 1 1 Ger 4 i i ABA pa pudxii ng lt et SOd ISOW LxOX HLOO 19S 049X 8090 13d 6z gt A L 99A HAV 1 29 PXIOOMSS 70 vi P9d SS VLOO vas vooo 03d gz waona gr 0d 0ax1 a090 FXgosng za oaxw 9090 MOS LOXL dd us kupona lt Tp Eod 198 049X 8090 osIlWiqxu 9d Te T 1 1sSyonas Do OLY t lt ot 00d vas vooo ISOW LMOX 8190 SQd az A oza iu ql e N a A T Anol gt HUMOPINYS AH 9 9 9 9 4u00 SSN LOO vdd pz a a a a SES y 9N NGHS Te 9229 roueg L gt a oqv 04X1 0090 dd Fez gt xLesnd g mon 2599911 uni ESuOMeSS Lied 990v oaxw 0090 zaa zz CJ Fxtesng A8r0 z een ale L gujonas C gt u3x1zsng LOT JOA L 09AV Ljesues A1 Es y svd soav 049X 8090 tad TZ gt FA9SU9S AT L gt rove roay v090 0dd oz EASSUSS AH gt eva coav AL Sen Er id E la F la m _ zy 2Wd zoav 10va LLoQv tad 777 30 2 2 2 2 E Be T Tp Led 190V oovaoroav Sauer F LU OMES Ss SS ON Wee 629 uf gno oy Vd dauv 09Gv 6oav a lt keulomes g mon CS99911 un ei en yp VZO HISIA 43uv eoav oad pd PSP L AGS 3 L esuas AH 369 44001 LOA KOJAV IZH i en vvceeboeuix v 8 yA 9 S l4 z L I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 8 Jo aBed go U
163. ng X Plane instead of from a sensors board The GPC requests this data with a BCMD_SENSORS_FETCH_AHPRS command The data field for packets of this type is empty The computer replies with a BCMD_SENSORS_REPLY_AHPRS packet which is structured as showed in table 3 8 The data is stored in the reply packet in little endian order Electric Owl Final Report 65 CHAPTER 3 FINAL DESIGN Field Type Name Description float32 Gnormal Normal acceleration in G s float32 Gaxial Axial acceleration in G s float32 Gside Side acceleration in G s float32 Q Pitch rate in rad s float32 P Roll rate in rad s float32 R Yaw rate in rad s float32 pitch Pitch angle in rad float32 roll Roll angle in rad float32 hdg Heading in rad float64 lat Latitude in rad float64 lon Longitude in rad float32 elev_msl1 Elevation above mean sea level in m float32 hpath Horizontal pat in rad float32 Vtrue Velocity relative to ground in m s float32 VVI Vertical velocity indicator in m s Table 3 8 Layout of the data field for BCMD SENSORS REPLY AHPRS packets 3 5 2 Radio Downlink Protocol The radio downlink protocol governs communications sent by the plane down to the ground computer In particular it defines the structure of telemetry packets Packet Structure Like bus packets downlink packets can be of variable length to handle data payloads of varying sizes The layout of a downlink packet is illustrated in figure The packet header b
164. ng the plane Mr Klix flew the plane up to a reasonable altitude and then engaged the autopilot The plane did an excellent job maintaining the desired heading with fairly low levels of oscillation After Mr Klix landed the plane the team made a some adjustments to the plane s pitch and had Mr Klix take it up for a second flight The plane s flight characteristics showed a minor improvement Telemetry data from the second of these flight tests is illustrated in figure The blue line plots the plane s heading versus time The regions of the graph shaded in gray indicate portions of the flight during which the autopilot was engaged and the orange lines mark the heading which the plane was trying to maintain As the plot shows after a short start up transient following the transition to autopilot the plane does a reasonably good job maintaining the desired heading though it oscillates a bit Figure 4 2 displays the plane s flight trajectory during the second flight test overlaid on top Electric Owl Final Report 95 CHAPTER 4 TESTING AND RESULTS of a satellite image of Dick Scobee Field and the surrounding area The red lines indicate portions of the flight for which the autopilot was active The arrows on the path indicate the plane s direction of flight The telemetry data in figure 4 1 comes from the two long autopilot flight segments in the lower part of the image In agreement with the numerical data of the previous figure
165. nput ports on the differential pressure sensor Be sure to check the polarity is correct The easiest way to check polarity is to take a set of calibration data as described below and then look at the values The sensor should give positive readings for increased flow rates 3 Mount the pitot tube inside the wind tunnel Only the pitot tube should be placed in the wind tunnel the backplane with the sensors board must remain outside of the tunnel for easy access 4 Connect one RS 485 transceiver cable to the PC Plug it into the data capture bus de fined in the sensors03_take_caldata c source file Be sure to note the device node assigned to the transceiver For convenience we will assume for the remainder of this procedure that the transceiver is on dev ttyUSB1 5 Set the wind tunnel flow rate to the desired speed as measured by the wind tunnel s own pitot static system This procedure assumes the use of calibration flow speeds that generate differential pressures of 0 0 05 0 12 0 20 0 30 and 0 44 inches of water At the Ryon Lab wind tunnel these correspond to flows of 0 10 15 20 25 and 30 mph Electric Owl Final Report 138 APPENDIX A USER S AND SAFETY MANUAL respectively Other pressures flow rates can be used but this will require changes to the calibration scripts later on 6 Make sure that the backplane is unpowered 7 When the wind tunnel flow has stabilized set up the busmonitor program to c
166. ny values click the Apply button Close the I O Configuration dialog 10 Again inside the ground software open the UAV menu and select the Live Flight option With this the ground software is set up for data collection 11 Plug the BNC T adapter into the output port on the function generator Using the BNC cable connect one side of the T adapter to an oscilloscope and using the BNC clip leads connect the other side of the T adapter to the LED Set the function generator to output a square wave of a reasonable amplitude and frequency The frequency will be adjusted in the next step but the amplitude must not exceed the limits of the LED 12 Aim the LED at the calibration pattern on the turntable and have the turntable begin rotating Once the turntable has reached its steady state speed adjust the LED blink frequency using the function generator until it matches that of the rotating pattern The pattern will appear to stop rotating within the LED s field of illumination Measure this frequency using the oscilloscope and use it along with the pattern s spatial frequency to calculate the rotational rate of the turntable Write this number down for future reference NB Beware of aliasing effects For example if the LED is blinking at half the rate at which the pattern is rotating the pattern will still appear to be stopped even though the rates do not match One way to check for aliasing is to dou
167. o reply counts HITL only CH_RS_ACCELX_OUT 0x50 Count of x accelerometer outliers CH_RS_ACCELY_OUT 0x51 Count of y accelerometer outliers CH_RS_ACCELZ_OUT 0x52 Count of z accelerometer outliers CH_RS_GYROX_OUT 0x53 Count of x gyroscope outliers CH RS GYROY OUT 0x54 Count of y gyroscope outliers CH_RS_GYROZ_OUT 0x55 Count of z gyroscope outliers CH_RS_MAGX_OUT 0x56 Count of x magnetometer outliers CH_RS_MAGY_OUT 0x57 Count of y magnetometer outliers CH_RS_MAGZ_OUT 0x58 Count of z magnetometer outliers CH_RS_AIRSPEED_OUT 0x59 Count of airspeed outliers CH_RS_BARO_OUT Ox5A Count of barometer outliers CH_RS_TEMP_OUT Ox5B Count of temperature outliers Table 3 10 Telemetry channel types and corresponding marker bytes Electric Owl Final Report 69 CHAPTER 3 FINAL DESIGN Channel Byte Description CH_EXT_AIR_TEMP 0x80 External air temperature CH_GPS_FTX_STATUS 0x81 GPS fix status CH_MANUAL_OVERRIDE 0x82 Manual override status 1 override CH_FP_POINTER 0x90 Flight plan pointer CH_RED_VOTING_MATRIX 0x91 Redundancy failure voting matrix CH_RED_WORKING_SET 0x92 Redundancy working set CH_PRESS_ALT OxCO Pressure altimeter CH_GPS OxC1 GPS sentences CH_STATE_LAT OxDO State vector latitude degrees CH_STATE_LON OxD1 State vector longitude degrees CH_STATE_ALT OxD2 State vector altitude meters msl CH_STATE_HEADING OxD3 State vector heading radians CH_STATE_PITCH OxD4 State vector pitch radians CH_STATE_ROLL OxD5 Stat
168. occurs which the application wishes to receive the kernel creates a fake IPC message with a source address indicating that it is coming from an interrupt Thus in order to wait for an interrupt to occur a user thread can simply call ipc_recv with the appropriate arguments 3 2 7 3 Autopilot Task The autopilot program was originally developed as a user program running on a PC then ported into the embedded environment this year Currently it runs as a user thread under the custom kernel The thread runs infinitely in a main loop which polls other circuit boards for data Electric Owl Final Report 46 CHAPTER 3 FINAL DESIGN over the bus processes the data and sends replies back out At the end of each time through this processing cycle the thread sleeps until the beginning of the next 40 millisecond process ing window The autopilot s computations are split into a standard guidance navigation control GNC configuration Details on the autopilot algorithm can be found in section 3 3 3 3 Autopilot Software 3 3 1 General Structure The autopilot software is split into guidance navigation and control components The data flow between the different components is shown in figure 3 2 Interna ARE State Attitude Heading Position Vehicle Guidance Desired Orientation ontrol Surface Commands Control FID state Figure 3 2 Data flow in the autopilot Electric Owl Final Report 47
169. ode and finishing with two bytes of voltage data for bus 1 Electric Owl Final Report 61 CHAPTER 3 FINAL DESIGN Register Name Code Byte Description SERVO_REG_JOYSTICK 0x00 Servo joystick values unused SERVO_REG_OUTPUTO 0x01 Servo output 0 SERVO_REG_OUTPUT1 0x02 Servo output 1 SERVO_REG_OUTPUT2 0x03 Servo output 2 SERVO_REG_OUTPUT3 0x04 Servo output 3 SERVO_REG_OUTPUT4 0x05 Servo output 4 SERVO REG OUTPUT5 0x06 Servo output 5 SERVO REG OUTPUT6 0x07 Servo output 6 SERVO_REG_OUTPUT7 0x08 Servo output 7 SERVO REG OUTPUTS 0x09 Servo output 8 SERVO REG OUTPUT9 OKOA Servo output 9 SERVO_REG_LV_VOLTAGE 0x0B Low voltage battery voltage SERVO_REG_LV_CURRENT 0x0C Low voltage battery current SERVO_REG_HV_VOLTAGE 0x0D High voltage battery voltage SERVO_REG_HV_CURRENT OxOE High voltage battery current RADIO REG BUSO VOLTAGE OxOF Bus 0 voltage level RADIO REG BUS1 VOLTAGE 0x10 Bus 1 voltage level RADIO REG BUS2 VOLTAGE 0x11 Bus 2 voltage level RADIO_REG_BUS3_VOLTAGE 0x12 Bus 3 voltage level SERVO_REG_OVERRIDE 0x13 Manual override status Table 3 4 Data register codes used with BCMD_TELEM_FETCH and BCMD_TELEM_REPLY packets Radio Board Commands The radio board accepts a handful of commands for handling data transmitted and received over the radio link The BCMD_SEND_DLPACKET command is used to send a downlink packet to the radio board for transmission The data field for packets of this type consists of
170. ods are connected to plastic control horns on both ends with metal clevises secured with metal locking clips The stock radio control receiver used for manual override is the 2 4 GHz Spektrum AR6200 Because of limited servo cable length and the need for the servo board to be between the manual override receiver and the servos the receiver is located right next to the servo board The receiver has a remote which is located in the tail assembly and is oriented at right angles to the main receiver to improve reception 3 6 4 Avionics Mounting The avionics suite has been mounted in the plane in a crude but effective manner The main backplane has been glued to square balsa dowels which have in turn been glued to the bottom of the main compartment The rest of the modules plug into the backplane while two notched Electric Owl Final Report 78 CHAPTER 3 FINAL DESIGN balsa sticks glued to the sides of main compartment serve to prevent the modules especially the sensors boards from moving The modules are not at present held in place from the top since the connectors to the backplane seem to be stiff enough The servo board is installed in the slot closest to the front of the plane to allow space for the large number of servo and receiver wires as well as to shorten the wires running to the primary and secondary batteries in the battery compartment The positioning of the other modules is somewhat arbitrary although keeping the teleme
171. of this section documents known errata with this series of boards Backplane 02 e Mounting holes in bottom try not to expand total area e Missing board revision text e Additional timing lines 2 would be useful for synchronization Electric Owl Final Report 82 CHAPTER 3 FINAL DESIGN Servo 02 e Silkscreen labels for R87 and R89 are swapped in location Sensors 02 e Silkscreen for C4A sucks e R81 R82 R83 and R84 should be moved right near U5 to reduce EMI pickup concerns e Silkscreen for R54 and C55 are reversed Accelerometer channel Y e ATXMEGA32A4 errata number 7 applies to the ADC several ADC samples must be junked after switching the input MUX An analog output version of the LY530AL chip is available as the LY530ALH which could be used with the other analog inputs on the AVR U41 LY530AL has CS pin 10 connected to ground instead of Vdd IO This forces the chip into SPI mode when it should be in 12C mode C81 needs to be low ESR e GPS PPS line should be accessible ideally through backplane timing lines GPC 01 e The USB connector is placed backwards on the board e The mounting holes on the USB connector are too small e Silkscreen labels for R34 R30 and R35 are obscured by vias e TST line is not accessible via jumper Electric Owl Final Report 83 CHAPTER 3 FINAL DESIGN e Need to allocate a pin on the ARM for the AVR to use to trigger an interrupt upon com
172. og measurements from the accelerom Electric Owl Final Report 26 CHAPTER 3 FINAL DESIGN eter are fed through precision micro power op amps from TI to condition them before they are measured in three separate channels of the internal 12 bit ADC on the AVR microcontroller All three axes of gyroscope measurements are also performed with the AVR ADC Be cause all three axes are not currently available in a single convenient package the gyroscope functionality is divided between two separate parts from ST Microelectronics with an X Y gy roscope the LPR530AL and a separate yaw gyroscope the LY530ALH The third revision of the board replaced a digital DC yaw gyroscope with the equivalent analog part from the same vendor due to availability issues Each of these provides a reference voltage output that must also be measured using a total of five ADC channels The final analog component is the MPXV7002DP differential pressure sensor This sensor is attached to the pitot static tubes of the aircraft for measuring relative airspeed The part was selected to account for a airspeed range up to approximately 50 mph This signal is conditioned by a TI OPA335AID op amp to bring it to the input range for the AVR ADC Table 3 1 shows the pin assignments on the microcontroller The ATXMEGA32A4 uses multiplexed inputs to the four ADC channels which can map any input pin into each ADC channel The ADC itself is pipelined such that conversions can b
173. olled in the sensors board s Electric Owl Final Report 40 CHAPTER 3 FINAL DESIGN main event loop causing a function to be called that re initializes the low level state machine for the next transaction In particular it sets up a buffer containing the bytes that comprise the 12 command to be sent and prepares a second buffer for receiving the response The low level state machine then manipulates the AVR s I2C hardware to send the com mand and retrieve the reply At each pass of the event loop the I2C hardware is polled to see if it is ready for the next action and if so it is carried out When the full reply has been received it is processed the low level state machine is set to an idle state and the high level state machine is advanced causing the system to proceed to the next 12C transaction Garmin GPS Interface The sensors board receives GPS positioning information from the off board Garmin GPS unit over a standard serial link using the Garmin proprietary binary format described in 1 The GPS emits a packet with a new position record once every second Since the AVR only has four DMA controllers and since these are all allocated to handling bus communications see section 8 2 2 receiving from the GPS is accomplished by polling the GPS s assigned USART receive register for new bytes inside the main event loop Because the GPS serial link runs at only 9600 bps compared e g to the 921600 bps system bus the likel
174. oltage bat tery input on the servo board One shore power cable One RS 485 transceiver cable One AVR programmer One PC with all necessary software dependencies installed a copy of the project Git repository and at least one USB port To take magnetometer calibration data follow these steps 1 2 Complete steps 1 and 2 of the accelerometer calibration procedure above Still in sensors03_take_caldata c near the top of the file is a line with a preprocessor directive defining the USE_MANUAL_DATA_CAPTURE symbol Make sure that this line is commented out and save the file For magnetometer calibration manual data capture is not used data must be continuously streamed to the bus Complete step dot the accelerometer calibration procedure above Plug the servo board and the sensors board with the accelerometers to be calibrated into the backplane inside the airframe Electric Owl Final Report 130 APPENDIX A USER S AND SAFETY MANUAL 5 Complete steps 6 and 7 of the accelerometer calibration procedure above When con necting the AVR programmer it may be easier to remove the sensors board from the backplane attach the programmer and then plug the board back into the backplane 6 Disconnect the shore power cable from the backplane 7 Move the data collection setup to a location outdoors away from buildings and large metal objects These distort the Earth s magnetic field in their proximit
175. ome position overshoot as it turned when proceeding from one waypoint to the next but otherwise tracked the expected path reasonably well 4 4 Flight Tests In order to demonstrate the functionality of the system in a real flight environment the team conducted a series of flight tests over the course of the year Each flight test was performed with the aim of demonstrating a specific feature This section catalogues all the flight tests that the team carried out their purposes and their results 4 4 1 Servo Board Flight Test 08 22 2010 The purpose of this flight test which was conducted at the end of the summer just prior to the start of the Fall 2011 term had two goals First At this point in time the team had just finished writing the first version of the firmware for the servo control board and wanted to verify that the manual override feature worked properly In this test the team was able to successfully fly the Electric Owl Final Report 90 CHAPTER 4 TESTING AND RESULTS plane under manual control with only the servo board installed operating in manual override mode This confirmed the ability of the servo board to take correctly receive and process input from the manual RC receiver and also to provide control pulses to each of the servos with the appropriate timing and duration The second goal of this test was to verify the operation of the power supplies on the servo board which would eventually be used to
176. orientation This function is performed using a set of PID controllers one for each axis of elevators ailerons and throttle There are also some cross axis coupling terms which have been added manually Currently the controller gains are set at compile time it would be a useful future extension to allow these gains to be changed at runtime Electric Owl Final Report 48 CHAPTER 3 FINAL DESIGN 3 3 2 Sensor Redundancy Management The GPC ARM firmware processes redundant sensor data before supplying it to the autopilot algorithm First it queries all sensor boards attached to the system Then based on the number of replies it receives and on the type of data asked for high rate IMU measurements or low rate GPS data the GPC integrates the data it has received into a single set of sensor readings which it then passes to the autopilot Presently the system is configured to handle data for up to three sensors boards however it can be straightforwardly extended to process data from more Redundant High Rate Data Processing If only a single set of high rate data is received then that set is sent directly to the autopilot with no further processing If two sets of data are received the values for each sensor are averaged together before being sent to the autopilot If three sets of data are received the GPC inspects each piece of sensor data to see if one of the values deviates substantially from the other two If so the offendin
177. ox queue Remove from radio mailbox queue Radio mailbox contents reply Generic data fetch command Generic data reply Fetch high rate sensor data High rate sensor data reply Fetch low rate sensor data Low rate sensor data reply HITL fetch sensor data from X Plane HITL sensor data reply Set servo outputs to specified values Table 3 3 Bus command types and corresponding identification bytes ahead of time This saves both bus bandwidth and processing cycles on each board s AVR A BCMD_TELEM_REPLY command is sent to reply to a BCMD_TELEM_FETCH request The data field of a BCMD_TELEM_REPLY packet contains a list of data register code bytes that indicate which registers were read each followed immediately by the corresponding data Possible values for these codes are listed in table Multi byte data values are sent in big endian order The sizes of all data values are known beforehand at both the source and destination so no data length bytes are necessary As an example suppose that the radio board is programmed to reply to BCMD_TELEM_FETCH requests with the voltages on buses 0 and 1 When the GPC needs this data the GPC sends a BCMD_TELEM_FETCH packet addressed to the radio board The radio board replies in the form of a BCMD_TELEM_REPLY packet with a data section that begins with the RADIO_REG_BUSO_VOLTAGE register code followed by two bytes of voltage data for bus 0 then by the RADIO_REG_BUS1_VOLTAGE register c
178. plane Figure 3 1 Photograph showing all four types of boards plugged into the backplane In order to provide satisfactory redundancy it was decided early in the project to provide redundant electrical connections between the modular circuit boards It was reasoned that the quadruple computer redundancy on the Space Shuttle flight computer 9 was a good starting point In order to implement quadruple flight computers without additional failure due to bus shorts or latchups four buses were deemed necessary The four buses largely dictated the design of the backplane To reduce complexity with designing the remaining boards it was chosen to design them around a common microcontroller and bus interface To minimize the performance impact of communicating with multiple hardware buses the team sought a microcontroller with both adequate computational performance and sufficient hardware serial interfaces Atmel s AVR line of microcontrollers includes the ATXMEGA32A4 which offers 5 hardware serial ports in a Electric Owl Final Report 21 CHAPTER 3 FINAL DESIGN package with only 44 pins to reduce the complexity of manufacturing the avionics components This chip was also found to have sufficient analog inputs and other peripherals and so the team chose the ATXMEGA32A4 as the basis of all four varieties of boards After choosing RS 485 for the bus physical layer T s SN65HVD12 was chosen as the bus interface chip The same hardware bus int
179. pounds including motor servos Electric Owl Final Report 74 CHAPTER 3 FINAL DESIGN battery R C receiver and landing gear Features The Senior Telemaster is an exceptionally stable slow flying and generally well behaved aircraft and this simplified autopilot development considerably The fuselage of the plane is very open and has significant free space for payload thus allowing flexibility in po sitioning the avionics and auxiliary sensors The plane is quite light for its size while still remaining relatively durable Limitations The chosen aircraft does suffer from two limitations high parasite drag and the conventional landing gear The high drag is not particularly important for testing the avionics package but renders the plane quite unsuitable for high altitude flights or flights lasting over an hour The conventional landing gear complicates the takeoff roll because it makes the plane unstable in yaw This effect is particularly noticeable on grass fields The small tail wheel is also not very stable and is easily damaged furthermore damage to the tail wheel tends to propagate up into the tail assembly Revision History The first prototype the OWLbatross was built from a kit by Mr Brockman when he was in high school This prototype was modified to have a tricycle landing gear with a steerable nose wheel instead of a conventional landing gear This modification increased weight and drag but greatly improved tax
180. pture event causing the timer value to be recorded in a special compare and capture register An interrupt is then triggered which reads this value and sets up a timer capture event to occur when the RC input line voltage falls When the RC input line is pulled low the Electric Owl Final Report 35 CHAPTER 3 FINAL DESIGN timer is stamped once again and another interrupt is triggered that takes this value and uses it in conjunction with the rise timestamp to determine the duration of the pulse One of the RC servo input lines is used to determine if RC manual control is active When the user wants to engage manual control a switch is flipped on the RC transmitter that causes the manual override input line to be pulled high The servo board AVR checks for this to occur and sets the servos to use the manual control inputs when it does It is important to note that even when manual control is engaged the servo board continues to listen for and store servo values from autopilot control packets received over the bus This ensures that the transition to autopilot control is as smooth as possible should manual override be deactivated at the transmitter or should the transmitter go out of range Emergency Mode The servo firmware is programmed to disable the throttle and set all con trol surfaces rudder elevator and ailerons to their neutral positions in the event that the board both stops receiving servo commands from the autopilot and
181. pulse width modulated position value The servo is a closed loop motor control system with position feedback from a potentiometer The motor is heavily geared down to provide large amounts of torque although this reduces the maximum possible rotation rate Standard Hobbyist R C Input Standard servo wires connect the servo board with a stan dard six channel RC aircraft controller Each of the six channels is voltage divided to a safe input level for the microcontroller and then treated as a digital input Software is then able to either pass through the R C input to the output or to use the onboard control system to set the control surfaces Servomotor Control A TI CD4017BM96 decade counter is used to send control outputs to the servos Each servo is assigned to a one of the counter s ten outputs allowing control of up to ten servomotors at once with only two control signal lines from the servo board s AVR microcontroller Two TI TXB0101 level shifter ICs are used to convert the 3 3 V the control signals from the AVR to the 5 V levels needed to manipulate the servos Electric Owl Final Report 24 CHAPTER 3 FINAL DESIGN For more information on how the servo board controls the servos see section 8 2 3 Battery Interface In addition to the two regulators for the local power supplies the servo board also has connectors for the high voltage 15 V to 35 V and low voltage 4 5 V to 9 V batteries onboard the aircraft The distinc
182. quickly for any of these facilities to really be exer cised Due to what was later determined using video analysis to be a misbalanced center of gravity the plane crashed after about five seconds of flight shattering the front end of the Electric Owl Final Report 91 CHAPTER 4 TESTING AND RESULTS airframe and causing the electronics to become ejected from their mounted positions On the other hand the team was able to successfully collect a handful of telemetry frames demon strating that the telemetry downlink worked The team s experience with decoding the down linked packets also led the team to re design the telemetry logging capabilities of the ground software and spurred the development of the logging protocol see section 3 4 5 in particular 4 4 3 Initial Autopilot Flight Test 03 06 2011 The next flight test the team conducted was aimed at demonstrating basic autopilot function ality by having the plane maintain a fixed horizontal path By this time the team had written firmware for all of the different boards calibrated all of the sensors except for the airspeed sensor and integrated the autopilot code into the GPC firmware In order to avoid the problem with the plane s center of gravity that caused the previous flight test to end prematurely the team had some of the experienced RC pilots at the flying field help check to ensure that the plane was properly balanced Additionally since the team s experien
183. r August 2001 37 Space Shuttle General Purpose Computers fact sheet NASA Spaceflight April 2002 38 QinetiQ s Zephyr UAV exceeds official world record for longest duration unmanned flight press release QinetiQ September 2007 39 The Unveiling of the Solar Impulse HB SIA press release Solar Impulse June 2009 40 X 29 Fact Sheet fact sheet NASA Dryden Flight Research Center December 2009 41 2009 Official AMA National Model Aircraft Safety Code Document 105 Academy of Model Aeronautics January 2006 42 First Person View Operations Document 550 Academy of Model Aeronautics 43 ARRL Band Plans web page American Radio Relay League http www arrl org FandES field regulations bandplan html last checked 20090726 44 Frequency Chart for Model Operation web page Academy of Model Aeronautics www modelaircraft org events frequencies aspx last checked 20090726 45 Experimental certificates Regulation 14 CFR 21 191 Federal Aviation Administration 46 Experimental certificates general Regulation 14 CFR 21 193 Federal Aviation Admin istration Electric Owl Final Report 105 REFERENCES 47 Experimental certificates Aircraft to be used for market surveys sales demonstrations and customer crew training Regulation 14 CFR 21 195 Federal Aviation Administration 48 B Clinton Statement By The President Rega
184. r manually or by using a solder mask generated from the layout file The relevant parts may then be placed manually or with standard automated fabrication tools Care must be taken to observe the polarity of certain capacitors and active components The team recommends two solder reflow passes when using manual construction Several of the larger inductors and capacitors take significant time to heat to the melting point which may cause damage to the active components and should be installed first The remaining surface mount components may be installed at once Through hole components including the bus and debugging headers should be installed separately Note that on the sensors board there are several QFN packages that have no visible leads from the top Extreme care must be taken with these components when soldering to avoid solder bridges After construction it is advisable to check for solder bridges both visually with the aid of a microscope and electrically with a digital multimeter Electrically reported shorts should be compared with the system schematic to establish whether connectivity is expected Electric Owl Final Report 189 APPENDIX C ASSEMBLY INSTRUCTIONS AND BILL OF MATERIALS ooo ooo ooo ooo ooo ooo ooo ooo ES ES ES 3 SLOT R3 SLOT_A2 SLOT_A1 SLOT_R 00000 00000 00000 00000 000009 00009 00009 000009 align boards with markers Backplane Board reu03 ELEC494 2810 2811 SLOT_C3 SLOT_C2 SLOT_C1 SLOT_CA
185. ratch The hardware was designed in a modular manner separating the different pieces of system functionality onto four different types of circuit boards so as to make the system easily extensible to accommodate redundancy of the various components for the sake of improving the system s overall fault tolerance In particular the team focused on implementing redundancy in the system s sensors but designed the system so that other types of component redundancy can be easily added in the future The team wrote and tested a complete set of firmware for each of the circuit boards includ ing a basic autopilot algorithm and a custom real time kernel for the general purpose computer board The system is capable of sensing the plane s current state and using this information to manipulate the plane s control surfaces to get the aircraft to follow a stored on board flight plan It also continuously transmits telemetry about the plane s status to a computer on the ground using an on board radio link The team developed a PC ground software application for real time UAV monitoring telemetry analysis and system simulation and testing The team successfully demonstrated the basic functionality of the system operating with a triply redundant set of sensors in a real flight environment with the avionics package installed in a standard off the shelf RC airframe The plane successfully processed data from each of the redundant sets of sensors and used this da
186. rding The United States Decision To Stop Degrading Global Positioning System Accuracy press release The White House May 2000 49 WAAS Fact Sheet GNSS Library Federal Aviation Administration mww faa gov about office_org headquarters_offices ato service_units techops navservices gnss library factsheets q2 last checked 20090727 50 AC Propulsion s Solar Electric Powered SoLong UAV Fact Sheet AC Propulsion June 2005 51 Understanding Radio Language for RC Airplanes web page Hooked On RC Airplanes com http www hooked on rc airplanes com radio language html last checked 20090727 52 Cis Lunar MK5 Closed Cycle PLSS technical description Stone Aerospace http www stoneaerospace com products pages products cis lunar mk5 php last checked 20090727 53 tech rep http www technologyreview com blog deltav 23917 last checked 20090803 54 RADA Electronic Industries Ltd MAVINS Modular Avionics and INS GPS for UAV tech rep http www rada com solutions mavins html last checked 2010 10 07 55 Zephyr unmanned aerial vehicle tech rep QinetiQ 56 C Anderson ArduPilot DIY Drones http diydrones com notes ArduPilot last checked 2010 10 08 57 MicroPilot MP2028 Series Autopilots http www micropilot com last checked 2010 10 08 58 Rotomotion LLC UAV Helicopter Controller http www rotomotion com prd_UAV_ last checked
187. returns to the event loop Frame delimiters are not added to the packet buffer and escaped bytes are unescaped before they are added to the packet buffer The computation of the packet s CRC checksum is advanced as each byte arrives for maximum efficiency When a packet is complete a packet handler routine is called to verify the packet s CRC and process it before polling continues This firmware required several re writes before satisfactory performance was achieved Early attempts used interrupt handlers to receive bytes off of the bus but both the context switching overhead associated with entering and leaving the interrupt service routines and the length of the routines themselves proved too large for the system to handle and still run at the full 921600 bps bus speed This was the main driving force behind the decision to use an event driven software archi tecture on all of the AVRs By splitting each board s tasks into the smallest possible parts and polling for when each part is complete time spent in task handlers is kept to minimum This prevents any one piece of code from blocking up the system and ensures that all tasks get handled roughly in parallel As such the code on each AVR has been written to eschew inter rupts entirely except on the servo board where they are unavoidable but kept to a minimum in terms of execution time Transmission to each bus is handled using DMA A bus packet is first assembled in a buffer complete w
188. ric motor powered off of a lithium polymer battery Existing battery technology makes flights of longer than an hour impractical without the addition of solar panels A design team could enhance the existing power management system to use solar panels to recharge the batteries and run the motor e Improved Airframe A team of mechanical engineers could design an airframe capa ble of flying at very high Earth altitudes where the consistency of the atmosphere is similar to that on Mars The UAV could then carry sensors payloads up to such altitudes Electric Owl Final Report 99 CHAPTER 5 SUMMARY AND RECOMMENDATIONS and collect data Such an improved airframe would allow live testing of the avionics in extreme conditions more similar to those found on Mars Electric Owl Final Report 100 6 Acknowledgements 6 1 Technical Advisors The team would like to thank numerous mentors and advisors for their role in the success of this project David Fuson of ESCG Jacobs has been an invaluable resource for the team providing practical engineering experience and project management advice He has also provided feed back on presentation practices and slides Dr Humboldt Mandel was team s TSGC mentor He provided the team with insight into what it takes to make a Mars capable space probe and supported the team at both the spring and fall TSGC Design Showcase presentations Within the ECE department Dr Woods and Dr Wise ha
189. rom atthe avrdude prompt to view the EEPROM pages that were written A 5 Hardware in the Loop Testing Hardware in the loop HITL testing is useful for trying out changes to the autopilot using a flight simulator before testing them in an actual flight See section 4 3 for more details This section gives the procedure for setting up an HITL test Setting the system up for HITL testing requires the following materials One backplane board with at least two RS 485 connectors and at least one row of circuit board connection headers Make sure that no circuit boards are plugged into it One GPC board programmed with the firmware to be tested One shore power cable e One RS 485 transceiver cable Electric Owl Final Report 121 APPENDIX A USER S AND SAFETY MANUAL e One PC with all necessary software dependencies installed a copy of the project Git repository and at least one USB port It must be capable of running the Houston ground control software e One PC with the X Plane flight simulator installed This can be the same as the PC used to run the ground software or it can be a separate machine entirely If a separate ma chine is used both PCs must have ethernet ports and one standard ethernet connection cable is also required To test the system in HITL mode use the following procedure 1 Plug the GPC board into the backplane Power the backplane using the shore power cable and connect one end of the
190. round software currently supports two main raster image sources Microsoft Research Maps formerly TerraServer aerial photos and topographic maps and Shuttle Radar Topog raphy Mission SRTM digital elevation maps At the lowest zoom level some SRTM derived prerendered images are displayed The Microsoft Research Maps images come in resolutions ranging from 512 meters per pixel mpp down to 0 25 meters per pixel in some areas and use the Universal Transverse Mercator UTM projection Three image types are supported via toolbar buttons older black and white aerial photos down to 1 mpp newer color aerial photos down to 0 25 mpp in certain urban areas and old topographic maps down to 2 mpp The application supports automatic downloading of image tiles directly from the MSRMaps com web server as the user scrolls around the map The image tiles are cached locally on the hard drive to enable offline viewing later In this way the user can build up a local database of imagery for areas of interest then take it on the go to a location without Internet access The SRTM elevation maps come in two resolutions 1 arcsecond approximately 30 meters per pixel and 3 arcseconds This data is in unprojected direct latitude longitude coordinates so it has a distinctive x versus y scale difference which becomes greater when viewing farther away from the equator The files store actual elevation numbers measured in feet which are not suited for display direc
191. rtment of Electrical and Computer Engineering as part of the capstone design sequence and through the Texas Space Grant Consortium which funds educational NASA related projects Electric Owl Final Report 102 7 References 1 Garmin International Inc Garmin Device Interface Specification http eukles googlecode com svn history r2 trunk doc spec spec_garmin_interface pdf last checked 2011 05 03 2 R D Braun H S Wright M A Croom J S Levine and D A Spencer Design of the ARES Mars Airplane and Mission Architecture 2006 3 H S Wright J S Levine M A Croom W C Edwards G D Qualls and J F Gasbarre Measurements from an Aerial Vehicle A New Tool for Planetary Exploration 2004 4 NASA Mission News Preventative Care Continues Science on Hold September 04 2009 http www nasa gov mission pages MRO0 news mro 20090904 htm1 last checked 2010 10 08 5 NASA Mission News Spacecraft out of Safe Mode December 08 2009 nasa gov mission_pages MRO news mro 20091208 html last checked 2010 10 08 6 NASA Mission News NASA s Mars Reconnaissance Orbiter Resumes Observations December 16 2009 http www nasa gov mission_pages MRO news mro20091216 last checked 2010 10 08 7 Space Shuttle news reference tech rep NASA 1981 8 Telecommunications Innovations for the Mars Exploration Rover Mission tech rep NASA Jet Prop
192. s every street in the United States and Puerto Rico along with railroads and creek lake outlines The original Census Bureau data comes in an uncompressed text format with even more types of data making it unsuited for direct use Instead a custom intermediate data format has been created along with tools to reprocess the original data into the intermediate format With this compression the user can choose to copy around files on a county by county basis or grab the whole thing In the compressed format an individual file ranges up to ap proximately 5 megabytes for a populated county such as Harris County and the entire United States database weighs in at about 1 5 gigabytes Individual county files are loaded and un loaded automatically on demand as the user scrolls around the map with no further action required The global airport list comes as the same file used by the X Plane flight simulator for its internal airport database The source file has complete coordinates for individual runway locations lengths and widths as well as even taxiways for a large proportion of the airports The ground software skips over the taxiways and other auxiliary information but loads up all Electric Owl Final Report 55 CHAPTER 3 FINAL DESIGN the runways and displays them as four sided outlines overlaid on the map The four letter airport identifier and airport name are also displayed depending on the zoom level The entire world database us
193. signed using modern microcontrollers and other electronics 2 2 Project Focus To limit the scope of the investigation to a feasible senior capstone project the team decided to focus on developing first flight capable hardware with basic autopilot functionality Once this had been done the team focused on implementing redundant sensor capabilities in order to demonstrate the system s ability to accommodate redundancy Though this was the only form of redundancy the team actually implemented the team designed the hardware and the rest of the system to be capable of future expansion to provide the redundancy shown in Figure Electric Owl Final Report 18 CHAPTER 2 DESIGN STRATEGY 2 2 1 Flight Capable Hardware In order to demonstrate that the avionics system works it was necessary to test it under real flight conditions The team aimed to deliver hardware and firmware that have demonstrated their ability to control a test airframe in flight 2 2 2 Basic Autopilot Because any UAV operating on Mars must be capable of autonomous flight the team de veloped a basic autopilot algorithm that can run on an onboard microcontroller The team demonstrated the ability of the algorithm to fly the aircraft in a stable manner without any ground input The autopilot is capable of waypoint based navigation and the team tested this extensively using hardware in the loop simulation though time did not permit a flight test of this feature A
194. single failure leaves the system with three correctly functioning computers a safe configura tion that can still detect another error A second error fails the system back to an operational Electric Owl Final Report 17 CHAPTER 2 DESIGN STRATEGY mode though detection of further errors is severely hindered During his investigations of the Space Shuttle design as part of the Rogers Commission following the tragic loss of Space Shuttle Challenger noted physicist Richard Feynman remarked that the Shuttle s flight computer system was very well designed 11 In Shuttle s first approach and landing test this redundancy was inadvertently tested when one of the computers suffered an electrical short when the shuttle disconnected from the 747 that carried it to altitude 12 Because of the unique requirements that a Mars capable UAV must meet the team de cided that using quadruply redundant computers like the Space Shuttle would be an appropri ate method for improving the fault tolerance of the device s computing resources Specifically the round trip light propagation delay between Earth and Mars requires the ability for rapid au tomated failover in the event of a system error and only a system like that of the Space Shuttle allows this to happen in a manner that is at once fail safe and fail operational Furthermore the additional weight and power requirements imposed by adding the redundancy would be minimal if the system were de
195. st command sets the ARM to begin executing starting at its reset vector and the second actually runs the program A 4 Assigning Board IDs Board ID numbers are used to uniquely identify each board in the system for the purposes of addressing bus packets see section 3 2 1 This section describes how to write a board ID into the EEPROM of a board s AVR microcontroller Programming board IDs requires the following materials e One backplane board with at least two RS 485 connectors and at least one row of circuit board connection headers Make sure that no circuit boards are plugged into it e The board to which the ID is being assigned e One RS 485 transceiver cable e One shore power cable e One AVR programmer e One PC with all necessary software dependencies installed a copy of the project Git repository and at least one USB port To write the board ID into the EEPROM of an AVR follow these steps 1 Select an ID number for the board The ID should be different from the ID assigned to any other board and must be representable using an 8 bit unsigned integer value Electric Owl Final Report 119 APPENDIX A USER S AND SAFETY MANUAL 2 Open the write_boardid c file in the software majortom src avr directory Set the first value of the boardIDstr array to the ID number to be assigned to the board The remaining values in the array should form a null terminated string that identifies the type of the board b
196. supported In addition to the main graphical ground software the team developed a number of other standalone utilities to assist with development and data processing These are described in section A 6 of the User s Manual 3 4 1 General Interface Upon starting the ground software displays a default location with several data sources en abled Two toolbars provide controls to switch the set of data being displayed open a new data source zoom and pan or measure distances Several menus are available to open new files change settings configure UAV communications parameters and switch on an active tracking mode The main map display shows a combination of a background raster image plus one or more layers of vector data overlaid on top The raster images are always displayed in their original resolution this means that the map scale and map projection are determined by the selected raster data source and resolution All vector data is re projected on the fly from latitude longitude coordinates in order to match up with the raster map being displayed Be cause the resolution is taken from the raster data the available zoom levels are discrete and predetermined Along the left side of the main window is a list showing which data sources have been loaded Each source can be switched on or off for viewing by clicking on a box next to its name Electric Owl Final Report 53 CHAPTER 3 FINAL DESIGN 3 4 2 Raster Data The g
197. t in front of the runway Electric Owl Final Report 112 APPENDIX A USER S AND SAFETY MANUAL k Connect the main lithium polymer battery and wait for the motor controller to finish its start up sequence 1 Use the RC transmitter to make sure that the main motor spins correctly m Check the control surface polarity one more time n Check functionality of the manual override switch one more time o Use the telemetry downlink to ensure to that the plane s GPS has acquired a suit able fix p At this point the plane is ready for flight and the test can begin Be sure to invoke all necessary deities and request a safe and successful test prior to takeoff A 2 Software Dependencies Certain packages must be installed on the development workstation to successfully build the firmware and ground control software and program the microcontrollers A list of these is shown in Table A 1 The listed packages are for a Linux based operating envi ronment Package Version Description arm dev 20100728 Team compiled ARM cross compiler toolchain avr dev 20100709 Team compiled AVR cross compiler toolchain dev extralibs32 20100728 Team compiled 32 bit compatibility libraries geda gaf 1 6 1 gEDA electronics design suite including gschem pcb 20091103 gEDA PCB layout software openocd 0 4 0 The Open On Chip Debugger wxGTK 2 8 11 wxWidgets GUI library for GTK git 1 7 1 Git version control software Electri
198. t rest e gyro_rot_dat_files Cell array of paths to files with gyroscope data extracted from the telemetry logs generated with the gyroscopes in motion e airspeed_s_dat_files Cell array of paths to differential pressure sensor data files for each flow rate after pre processing with cd2matlab Electric Owl Final Report 143 APPENDIX A USER S AND SAFETY MANUAL Change the values of these variables to contain the locations of the data to be analyzed When finished make sure to save the file NB The order in which the paths are stored in the cell array variables above is very important Read the comments in the headers and bodies of the cal_gyro m and cal_airspeed m scripts for information on how these arrays must be structured 3 Run MATLAB Change the working directory to the software majortom utils direc tory and run the caltest m script at the prompt with the string argument corresponding to the sensor type to be analyzed For example caltest accel will run the ac celerometer calibration routine on the data file specified in the acc_dat_file variable defined in the caltest m script itself 4 The script will generate some plots of the data and the fit models and will print some numerical data e g mean square error etc to the command window Using this data decide if the model looks acceptable or if another round of data collection is necessary If the generated models are acceptable proceed
199. t16 accelZ z acceleration in cm s int16 gyroX Pitch up rate in mrad s int16 gyroY Roll right rate in mrad s inti6 gyroZ Yaw right rate in mrad s inti6 magX x direction magnetometer output unitless inti6 magY y direction magnetometer output unitless inti6 magZ z direction magnetometer output unitless int16 airspeed Pitot pressure sensor reading in dPa uint24 baro Air pressure in cPa int16 temp Temperature in tenths of degrees centigrade Table 3 5 Layout of the data field for BCMD_SENSORS_REPLAY_HIRATE packets Note that the sensor values are stored in little endian order Servo Board Commands The BCMD_SERVO_SETSERVOS command is issued by the GPC to set the servo outputs in accordance with the decisions made by the autopilot algorithm The data field contains the exact servo values to be set stored as four 16 bit unsigned integers in little endian order The exact layout of the data field is shown in table ARM GPC AVR Commands There are two special commands used privately between the ARM processor and AVR microcontroller on a GPC board Since they are used between chips on the same board packets of these types are not transmitted over the bus but are wrapped using the bus protocol headers anyway to avoid the need to design a special protocol just for these types of transactions The ARM uses a BMCD_GPCAVR_WHOAMI request to discover the ID number of the board it is on which is stored in the EEPROM on the AVR The data field
200. ta with a simple version of the autopilot to get the plane to maintain a fixed heading The team also performed successful hardware in the loop simulation testing of a more complete version of the autopilot that features waypoint based navigation and is ready to test it in actual flight at the next available moment Electric Owl Final Report 98 CHAPTER 5 SUMMARY AND RECOMMENDATIONS 5 2 Recommendations and Future Work There are many possible directions in which the project could be extended spanning a wide range of disciplines including electrical engineering computer science mechanical engineer ing and applied mathematics e Additional Redundancy Although sensor redundancy was implemented this year developing the software needed to support redundancy in the main computers would improve reliability Adding software support for redundancy in the servos and control surfaces would be useful as well Hardware support for these features is already built in to the design e Sensors Payloads A design team could work on developing payload suites of sensors other than those required to fly the actual plane e g a camera for live video downlink e Improved Autopilot The autopilot algorithm could be changed to be more robust and to support additional features including completely autonomous i e non waypoint based navigation and terrain avoidance e Alternate Power Sources The existing plane has an elect
201. tart up Open OCD by typing openocd at a com mand prompt This must be run inside software majortom since this is where the projects Open OCD configuration file resides e Again inside software majortom fire up GDB on the program to be loaded For example if it is located in software majortom build arm andis called prog elf running arm elf gdb build arm prog elf will do the trick f Open OCD runs a GDB local server on port 3333 Connect to it by issuing gdb target remote localhost 3333 at the GDB prompt g Run the following sequence of GDB commands gdb monitor halt gdb monitor reset gdb monitor flash erase_sector 0 0 15 gdb load The first two commands halt the ARM and reset it into a known state The third erases the flash memory in preparation for loading the new program Finally the fourth command writes the program into memory h Due to certain issues with the interaction between GDB and Open OCD the first attempt to load a program onto the ARM almost always fails in spite of the fact that GDB displays text indicating that the program has been successfully loaded To get around this quit out of GDB by typing quit at the GDB prompt Then repeat steps again to load the program a second time Electric Owl Final Report 118 APPENDIX A USER S AND SAFETY MANUAL i Have the ARM resume program execution by running gdb jump _vec_reset gdb continue at the GDB prompt The fir
202. the Houston ground software Laptop computer with X Plane installed for live 3 D visualization of the plane s trajectory e 6 channel Spektrum RC transmitter for manual control 3 Development Tools Box e AVR programmer e ARM programmer e RS 485 transceiver e Shore power cable 4 Repair Kit e Spare propellers e Wrench and prop axle coring tool e Extra mylar to patch holes e Mylar application iron e Superglue e Balsa sticks e Hacksaw e X Acto knives e Hex wrench set Electric Owl Final Report 109 APPENDIX A USER S AND SAFETY MANUAL Multitool Digital multimeter Spare fuses 5 Battery Charger Battery charge power supply Main charging unit LiPo and NiCd battery adapters Metal battery storage box for charging 6 Miscellaneous AMA Memberships for all pilots Video camera and camera operator for photographing and filming the flight from the ground Sunscreen hats sunglasses Water and snacks Cellular telephones First aid kit Safety glasses A 1 3 At the Field This section is written assuming that the test is being conducted at Dick Scobee Field in George Bush Park out in west Houston Other flying fields may have their own distinct set of procedures that will need to be followed Electric Owl Final Report 110 APPENDIX A USER S AND SAFETY MANUAL 1 Upon Arrival a Set up a workspace on one of the provided work tables b Reserve transmitter frequency
203. the ac celerometers magnetometers gyroscopes airspeed sensor static pressure sensor and temperature sensor e BCMD_SENSORS_FETCH_LORATE The board will reply with a BCMD_SENSORS_FETCH_LORATE packet containing the latest set of GPS data Analog Sensors Interface The accelerometers gyroscopes and differential pressure sen sor are all analog sensors see section 3 1 4 The sensors board reads values from these sensors using the AVR s built in ADC unit There are seven analog sensors three accelerometer axes three gyroscope axes and the airspeed sensor but the ADC unit on the AVR has only four channels so the AVR s ADC multiplexer is used to alternate channel assignments between the different sensors A Electric Owl Final Report 39 CHAPTER 3 FINAL DESIGN software state machine is used to control the order in which the sensors are read When the state machine is advanced a set of ADC conversions are initiated on the set of sensors being read The ADC conversion complete flags are polled inside the firmware s main event loop When the conversions are complete the state machine is advanced enabling the next set of sensors to be read Unfortunately due to an hardware erratum in the revision of the AVR being used on all the system boards switching the ADC multiplexer to accept input from a different bank of sensors causes the ADC to report bogus conversion values for several conversion cycles after the switch is
204. tion between these two is that the larger high voltage battery is connected through the motor controller to drive the propeller while the backup low voltage battery exclusively powers the avionics so that flight control may be maintained even after the drive power fails Both supplies feature current sensing resistors so that the dis charge rate and voltage of the battery can be measured in flight The power rail outputs on the servo board are connected through fuses to prevent a bus short from eliminating power to all of the buses 3 1 3 Radio Board The primary function of the radio board is to provide an interface to the on board the XTend 900 1W RPSMA radio used to provide air to ground digital data communication The standard AVR arrangement is used to provide bus connectivity and the standard power supply is capable of powering the radio module A front assembly diagram is shown in Figure C 3 along with the full bill of materials in Table C 4 XTend 900 1W RPSMA The XTend 900 1W RPSMA radio is an OEM module that is bolted onto the radio board and connected with a header The radio module interfaces with the microcontroller over a serial protocol and features a few additional control pins This module has a nominal range of 40 miles line of sight at the full 1 W transmit power This radio uses the 900 MHz ISM band that is unlicensed in the United States and uses frequency hopping to avoid interference The ground computer station
205. tly as pixel colors Instead the application looks for the maximum and minimum elevations in the current viewing area then automatically scales all points to a black and white rendering based on elevation In this way an individual point does not have a fixed color but its brightness will change as the map is scrolled by the user The source files with the elevation data are uncompressed and rather large so the application does not support automatic downloading for this map type The different resolution levels available have been interleaved in order of scale Thus Electric Owl Final Report 54 CHAPTER 3 FINAL DESIGN when zooming in or out the program automatically switches between the MSRMaps images and the SRTM images with the geographic projection switching simultaneously Although the map distorts in different ways in the two different projections the geographic point at the center of the current view remains constant when the switch is made 3 4 3 Vector Data The ground software supports a wide range of vector data sources both static and live updating The static sources include street data from the US Census Bureau the global airport list used in the X Plane flight simulator G7T and GPX log files and UAV telemetry files from this project The live sources include a network enabled GPS link and streaming data from the UAV The US Census Bureau data comes from their data product named TIGER line It in clude
206. to the polling loop The events listened for differ from board to board but the software on all boards adheres to this same basic pattern This description applies only to the programs running on each board s AVR microcontroller The software running on the GPC s ARM microprocessor has a completely different architec ture and is described in section Board ID Number Each board has a unique ID number written into the EEPROM of its AVR microcontroller This ID is read out of EEPROM by the AVR on startup and is used to identify the board in the address fields of bus packets see section 3 5 1 a board will ignore any packets with a destination ID other than its own 3 2 2 Bus Firmware Each board s AVR microcontroller implements the system bus protocol see section 3 5 1 To reduce the likelihood of missing incoming bytes due to time spent processing other tasks receipt of bytes is handled by the AVRs direct memory access DMA controller The DMA controller stores bytes in a receive buffer as they arrive with no intervention from the processor Each AVR has four DMA channels and there are four system buses so each bus is assigned its own DMA controller and receive buffer All AVRs poll for new bytes added to the DMA receive buffers for each bus as part of the Electric Owl Final Report 32 CHAPTER 3 FINAL DESIGN main event loop When a new byte is added it is copied into a packet construction buffer and then control
207. to the next step to store the calibration values in the EEPROM on the sensors board A 7 4 Step 4 Storing Values in EEPROM Writing the calibration values to EEPROM is accomplished by using the gen_cal_prog m script to create a program that loads the values into EEPROM when executed on the sen sors board AVR To do this use the following procedure 1 Edit the gen_cal_prog m file in the software majortom src utils directory Just as with the caltest m program the paths to the calibration data files to use are stored in variables within the gen_cal_prog m script itself and these must be updated to point to the data files to use For a list of the variables that need to be changed and their Electric Owl Final Report 144 APPENDIX A USER S AND SAFETY MANUAL functions see step 2 of the procedure for using caltest m in section above When finished make sure to save the file 2 Run MATLAB Change the working directory to the software majortom utils direc tory and run the gen_cal_prog m script at the prompt This will run all of the calibra tion procedures for all the sensors generate all of the calibration values and create a file called sensors03_write_caldata c in the software majortom src avr direc tory that will write them all into the EEPROM on the sensors board AVR NB The gen_cal_prog m program works by taking a pre constructed template source file and then substituting the calibration values into certai
208. try radio antenna connection far from the servo board and servo wires helps decrease servo jitter from EMI 3 6 5 Non Integrated Sensors In the present configuration the plane has two Garmin 18x LVC OEM GPS units for navigation One of these is integrated into the wing while the other is located above the main battery in the battery compartment behind the motor The GPS units are intentionally kept far apart to avoid oscillator interference The units are secured from moving with double stick foam tape The pitot static tubes extend from holes drilled in each wing about half way to the wing tips This positioning keeps them out of the propeller wash which would impair accuracy The pitot static tubes are glued into the wings and are each connected to two lengths of medical tubing This flexible tubing runs along the inside of the wing and emerges from the wing in the center where it can be connected directly to the sensors board 3 7 Future Expansion When considering the modular architecture used for this project thought was given to imple menting full redundancy even though this is outside the scope of the project for this year After considering the design of current NASA space systems including manned vehicles like the Space Shuttle 9 and autonomous probes like the Mars Reconnaissance Orbiter 4 5 Electric Owl Final Report 79 CHAPTER 3 FINAL DESIGN 6 Other inspiration came from the redundant systems used on co
209. ts were invaluable they were very limited in scope because the landers were stationary and could not move to explore the terrain More recently space exploration agencies from around the globe specifically NASA the European Space Agency and Russia have placed satellites into orbit around the Red Planet While many of these are still successfully operating the resolution of data they can gather is severely limited by their distance from the surface and rapid rate of travel although they are capable of exploring almost the entire planet Most recently several robotic rovers such as Sojourner Spirit and Opportunity have been deployed to roam the planet s surface These too have been quite successful however their effective range of exploration is limited to at most a few tens of kilometers due to the devices extremely slow rate of movement Recently NASA s ARES project 2 has suggested that using an unmanned aircraft as an alternative to these more traditional technologies could easily provide enough data to rewrite all of human knowledge of the Red Planet with only an hour of operation 3 An unmanned probe like this would be able to strike a balance between offering high resolution data like landers and rovers while remaining highly mobile like the orbital probes 1 3 Airborne Mission Requirements For an unmanned aerial mission to be successful there are several technical hurdles to over come The thin atmospher
210. ty that is to be tested e Check the airframe for flight readiness In particular Patch any holes in the surface with mylar Electric Owl Final Report 107 APPENDIX A USER S AND SAFETY MANUAL Verify the polarity of the drive motor Verify the polarity of the plane s control surfaces e Charge all the batteries including the following 1 Main propulsion battery 22 2V 6S1P LiPo 2 Avionics 4 cell NiCd backup battery 3 6 channel RC transmitter battery e Announce to interested parties that a flight test will be conducted e g by posting a notification message to the uav test announce listserv As a courtesy to individuals who may need more advance notice to plan their schedules it is best to do this as early as the flight test can be confirmed perhaps even earlier than on the day immediately before the flight test A 1 2 Packing Checklist 1 Airframe e Wings and fuselage e Battery compartment hatch Rubber bands for attaching the wings Avionics package and 900 MHz radio antenna mounted in the plane Batteries lithium polymer main propulsion battery and NiCd backup battery Motor controller Plane mounted flight camera 2 Ground Control Electric Owl Final Report 108 APPENDIX A USER S AND SAFETY MANUAL Extension cord and power strip Digi 900 MHz radio module and cables Laptop computer with all project development tools installed and which is capable of running
211. u soav 049X 8090 tad TZ gt F uax1esng py vva ray v090 odd Foz 3001 RER L 99A Lang 1 D ep vd oav vod ECH ap evd zoav Lova Loa ead waza gt FSIJNOO DIE anro vao Ip vd Loav oova oLoQv zad s gt FANO o peq oy Vd 434v 090v 69av Lad mz 4 FESLO eu 3001 RER _ L 29A08ng A D 33uv eoQv 08d gt gt Fd331S OH ceu Led sn pyze bowx y 8 yA 9 S l4 z L 167 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS JO e Abed EQ UoISIA 1 SIEMPIEY pyeoq oipe JO Oi euu uos WOU S pg anbi 6 8 L 9 S e L II Uewyo01g Yeqoy A8 NMVHG 30 0 39vd NOISIA3H ad qiu ZO UOISISA pyeog oipeg OIpeH gt Eso open F INOO lt gt y am Li ISsu oidNoo OWO SLY Hd Pop X cke ur ne DI i S Jano sos ZIONA N3 XLS8 sSu S19 LOdO Ley 92H pren ss Er ona daais aido pg FP EN O kod open 5 LEN L NGHS olpey nio Le EIDA LAS i 3 T 9 vi oNd NaHs 7 sbi ya Sr ONA jopua oa I de DINER Wee eu peu L 99A r oNa id a el i OO Ex open Zi 9Nd umd XL 8r oNa aaxu eodo Ke A PEN 8r 9Nd 99A Dee eu zu oe ONG ano Id gt kaamxu open DEN ogg FAS 301 402 li l ley 0H 6 8 z 9 S e L
212. uch errors to be detected Sequence Numbering Every uplink packet sent to the plane from the ground computer is given a 32 bit sequence number analogous to sequence numbers in TCP IP packets The sequence number plays two roles First it can be used to detect lost transmissions If the plane receives two uplink packets which do not directly follow each other in sequence i e have sequence numbers that differ by more than 1 then there must have been a packet transmitted in between them that the plane did not receive The plane can then send a packet Electric Owl Final Report 72 CHAPTER 3 FINAL DESIGN to the ground computer requesting re transmission of the lost data though this has not yet been implemented This is especially important for ensuring the integrity of flight plan upload see section 3 3 3 since flight plan steps must be updated in a specified order Second the sequence number bolsters system security by guarding against potential packet replay attacks If uplink packets were not numbered an attacker could conceivably sniff an uplink command out of the air and then re transmit it This could have disastrous effects if the plane carries out the instructions contained within the re transmitted packet such as overwriting the current flight plan With the sequence number the plane can know if a packet has already been transmitted once and ignore it if so Packet Types Presently there are two main categor
213. uired but the lighter weight of the motor made managing the center of gravity of the plane more difficult so its use was discontinued As of the time of this report the 4130 20 motor makes a high pitched whine when operated above 80 throttle setting This may indicate that the motor was damaged slightly during the crash which destroyed the first prototype s fuselage Since the motor is AC the DC voltage from the battery must be converted with a JETI motor controller rated for 70 amps This motor controller is connected to the servo control board which sees it as a normal servo thus allowing the avionics to control the throttle Alternative Propulsion The chosen electric motor is less powerful and has significantly less range than the glow fuel motor that the plane was originally designed for a 0 60 cubic inch 2 cycle motor capable of generating 1 8 horsepower The electric motor was chosen because it is much safer and more reliable than the glow fuel motor The glow fuel mixture contains about one third castor oil for lubrication a considerable amount of which ends up coating the wings and tail of the plane with sludge after a flight Starting the glow fuel motor requires standing precariously close to the propeller which is smaller and runs at twice the RPM of the electric motor The glow fuel motor s carburetor located about an inch behind the spinning propeller regularly requires hand adjustment while running The glow fuel motor also
214. ulsion Laboratory 9 J F Hanaway and R W Moorehead Space Shuttle Avionics System 1989 NASA Publication SP 504 10 Report of the presidential commission on the space shuttle challenger ac cident tech rep Presidential Commission on the Space Shuttle Challenger Accident 1986 last checked 20101007 11 Appendix F Personal observations on the reliability of the Shuttle tech rep Presiden tial Commission on the Space Shuttle Challenger Accident 1986 nasa gov shuttle missions 51 1 docs rogers commission Appendix F txt last checked 2010 10 09 12 Shuttle ALT Free Flight 1 GPC 2 Failure tech rep NASA Office of Logic Design klabs org DEI Processor shuttle alt_gpc2 index htm last checked 2010 10 07 13 T G Team GCC the GNU Compiler Collection http gcc gnu org last checked 2011 05 03 Electric Owl Final Report 103 REFERENCES 14 D Rath Open On Chip Debugger http openocd berlios de web last checked 2011 05 03 15 Digi International Inc XTend RF Module http ftp1 digi com support last checked 2011 05 03 16 R Dean and W Dixon Simplified statistics for small numbers of observations Analyt ical Chemistry vol 23 no 4 pp 636 638 1951 Accessed Online ACS Publications 05 03 2011 17 G D Carlow Architecture of the space shuttle primary avionics software system Com mun ACM vol 27 no 9 pp 926 936
215. urce of burns Food should be kept away from soldering equip ment to prevent lead contamination A 11 Legal Requirements A 11 1 FCC Radio Frequency Regulations Radio communications with the flying aircraft are subject to FCC regulations This falls under Title 47 of Federal Code Telecommunication 26 Operation within HAM bands should follow ARRL rules 43 At present the aircraft uses commercially available transmitters in the unlicensed 900MHz and 2 4GHz bands below transmission power limits however the operator should be aware of these restrictions and any additional radio links added to the aircraft verified to conform to these regulations A 11 2 FAA Flight Regulations Flight operations of model and unmanned aircraft are subject to regulation by the FAA Re strictions on model aircraft flight are documented in Model Aircraft Operating Standards 27 Additional regulations on unmanned autonomous flight are available in Unmanned Aircraft Operations in the National Airspace System 28 Electric Owl Final Report 152 B Schematics and CAD Drawings Electric Owl Final Report 153 APPENDIX B SCHEMATICS AND CAD DRAWINGS jo aBed go UuoISsIA 1 aJempey pipoq eue dyxoeq JO Ji wayos WOU g anp
216. ve both provided practical ad vice concerning technical issues ranging from reducing EMI issues to fixing mismatched PCB components Joe Gesenhues and the Mechanical Engineering Department graciously provided access to and assistance with operating the department wind tunnel which was used to calibrate the airspeed sensor Michael Dye Joe Gesenhues and Carlos Amaro provided assistance in ordering parts They also provided assistance with solving several issues including finding mounting standoffs for the radio board and locating an acceptable pitot tube Bob Ziegenhals and Cullen Newsom provided the team with some advice about selecting and mounting pitot tubes Electric Owl Final Report 101 CHAPTER 6 ACKNOWLEDGEMENTS 6 2 Flight Testing Team Electric Owl would like to thank the Bayou City Flyers for access to Dick Scobee Field Other model aviators at the field provided invaluable advice during flight testing with respect to flight dynamics equipment selection and RC flying Team Electric Owl owes a great debt to the members of the Bayou City Flyers that vol unteered to fly the test aircraft manually Although the team members are all licensed AMA members and can fly the aircraft an experienced hand was often necessary to ensure suc cess in flight testing Keith Klix among others has offered significant assistance 6 3 Funding Sources Funding for this project has been provided through Rice University s Depa
217. would attempt to program the board s AVR microcontroller with its assigned board ID see section and then with the main set of firmware If the programming was successful the board was then checked to ensure that all features of the current version of the firmware worked properly 4 1 2 Software Testing The team performed basic testing of the software functionality on an ad hoc basis vetting out each new feature as it was added This was typically accomplished by having each board being tested print debug text to an unused system bus and using the serial terminal program minicom to read it out on the PC Once the bus protocol was developed the need arose to test the ability of the boards to reply correctly to bus packets addressed to them Before the development of the GPC firmware this was usually accomplished using some simple test programs written for the PC that would inject packets onto the system bus The board s reply would then be captured using Electric Owl Final Report 85 CHAPTER 4 TESTING AND RESULTS minicom or the busmonitor or busmonitor2 programs see section A 6 Once the basic GPC firmware was written and the logging features of the Houston ground software were developed these programs were set aside in favor of using the GPC board to send packets and Houston to monitor the replies 4 1 3 Sensor Redundancy Testing Ground testing of the sensor redundancy was performed by using the GPC s debug console to
218. writing to one has not yet been written Real Time Clock The GPC board features a DS1302 real time clock RTC IC with an ac companying 1 Farad memory back up supercapacitor to prevent the clock from losing the time when the system is unpowered The team has not yet written any firmware to interact with the RTC but provisioned for it in the hardware design because it would be useful in providing timestamps for system logs USB Interface A mini USB connector has been provided to allow for easy interaction with the system in the field using a laptop and a USB cable The team has not yet written any firmware to use the USB interface but included it in the hardware design because of the improved ease of use that such an interface would provide 3 2 Avionics Firmware This section describes the firmware that runs on each of the AVRs on the different types of circuit boards and on the GPC board s ARM processor Electric Owl Final Report 31 CHAPTER 3 FINAL DESIGN 3 2 1 General Architecture Event Loop Upon boot each board s AVR firmware performs some initialization routines e g sets up the system clock activates the serial ports attached to the buses etc and then enters a main event loop The system sits in the event loop polling a number different condition flags waiting for an event to happen When one of the conditions becomes true the AVR immediately executes an event handler to process the event and then returns
219. xis aligned antiparallel i e pointing in the direction exactly opposite to the direction of gravity See the accelerometer datasheet for axis positioning The order in which each set of data is taken does not matter 13 Holding the board steady in the desired orientation use the minicom terminal to send the character A capital A ASCII 0x41 over bus O to the sensors board The board will respond by sending data back across the data capture bus which will be picked up by the busmonitor program and stored in the output file Repeat this step 10 times to take 10 measurements NB The number of measurements taken may be increased beyond 10 if desired how ever one must make sure to take the same number of measurements for each orienta tion in order to avoid biasing the zero offset measurements 14 Repeat steps for each remaining orientation 15 Stop the busmonitor data capturing process by sending it a CTRL C character Take the data file and save it somewhere where it can be accessed for use in the pre processing step that follows Electric Owl Final Report 129 APPENDIX A USER S AND SAFETY MANUAL A 7 1 2 Magnetometers The procedure for acquiring magnetometer calibration data requires the following materials e Airframe fuselage with backplane and motor installed Sensors board with magnetometers to be calibrated One servo board One nickel cadmium battery with a connector attached for use with the low v
220. y damaging the quality of the gathered data Be sure to take the nickel cadmium battery which will be used to power the system without shore power while data is being collected Make sure that the battery is charged 8 Connect one RS 485 transceiver cable to the PC Plug it into the data capture bus de fined in the sensors03 take caldata c source file Be sure to note the device node assigned to the transceiver For convenience we will assume for the remainder of this procedure that the transceiver is on dev ttyUSB1 9 The busmonitor program is used to capture the required data Complete steps 10 and of the accelerometer calibration procedure 10 Connect the nickel cadmium battery to the low voltage battery connection site on the servo board It may be easier to remove the servo board from the backplane connect the battery and then plug the board back into the backplane Since the system should now be powered data should now be streaming to the PC over the bus You can verify this by watching the size of the data dump file and seeing if it grows with time 11 Carefully pick up the plane and rotate it through a wide range of random orientations and headings Be sure to rotate it a full 360 degrees about each principal axis axial trans axial and normal at least once the more points collected from the various octants of the ellipsoid the better the resulting fit will be Electric Owl Final Report 131 APPENDIX
221. y9eq JO JIJWAYOS WOU y g anb 8 L 9 S r z L eDpug Aeujer Ag NMYYA 30 vO 39vd NOISIA3H nl qui 0 UOISIJA eue dyoeg L egpuo e L epuo e LDaoNCRIEO KE L BeNeeieq e 1 99 A SNG sr p 99Aesng Vr L Sogcereq 5 Lsogeereq 5 Hepu Sr Hepu Sr H 1018 ed 1018 L gpuo Ss E epuo Se p Boyeria L SeNeeieq ET L DeNeeieq e ver 99A SN 99A SN O Ors L 99Agsng 7 29Aesng L soqgeleq 6 Esogeeieq Se Al VEY o L soggereg o Fepuo bi Lrpug bi I v 9 9 LOIS O LOIS KEpuo lt gt 0 Oo kodnesng z Lo L egpuo Ca L gpuo s 14V esng Baneereq 7 1 baNge1eg LUH o9Aesng ur Loon esng B L Soggereq ES L Soggeieq Ss L Baneereq Se kepud i L gpuo Si o ok 4 1018 g 1018 AL ded L puS d Lepus 5 psogeeieq 2 GO LU Baneereq e L BeNeeiegq m O epup lt gt LO 1 00 A8Sng 1 09 esng s O Loo esng Z O sogea Se ksogeeleg E 3403 esna L gpuo rm L gpug SI LUH 3 1018 ev LOIS 8 L 9 S r z L 157 I Report ina F Electric Owl APPEND
222. yanoacrylate glue was used for the vast majority of the wood assembly and repair The entire fuselage and wings were originally covered with an inexpensive low temperature mylar coating from the factory Where this has been damaged it has been replaced with superior high temperature Super Monokote from Topflite Special care had to be taken to avoid burning the original covering at the interfaces between the original covering and the patches Landing Gear The stock landing gear has several inadequacies which have been addressed with varying degrees of success The foam main wheels shipped with the kit are too easily damaged and have been replaced by DuBro rubber wheels The tail wheel has likewise been replaced although the current tailwheel is sturdier it is not currently connected to the rudder and thus is not steerable limiting low speed taxi steering 3 6 2 Power System Propulsion for the plane is provided by an electric brushless motor from AXI the 4130 20 This motor is capable of delivering over 1000W of power to the propeller when equipped with an Electric Owl Final Report 76 CHAPTER 3 FINAL DESIGN 8S1P Lithium polymer battery and the correct 14x10 propeller The smaller 7S1P 5000mAh battery actually used decreases thrust somewhat but the motor remains greatly overpowered causing the plane to be able to take off in less than 15 meters with no wind and full payload A smaller motor the 4120 16 was also acq
223. ypes of boards plugged into the backplane 21 TONG a ed Sip PETERET an uw 47 3 3 Bytestructureofabuspacket 59 3 4 Byte structure of a downlink packet 67 3 5 Byte structure of an uplink packet 72 4 1 Heading lock telemetry from second flight on 04 02 2011 The blue line indi A Sra A e rd a S Z Z Eu 95 4 2 Plot of plane s trajectory during the second flight test on 04 02 2011 The red lines indicate parts during which the autopilot was active Arrows on the line IE 97 B 1 Backplane revision 03 circuit schematic 1 4 154 B 2 Backplane revision 03 circuit schematic 2 4 155 B 3 Backplane revision 03 circuit schematic 3 4 156 DA Backplane revision 03 circuit schematic 4 4 157 B 5 Servo board revision 03 circuit schematic 1 8 158 B 6 Servo board revision 03 circuit schematic 2 8 159 B 7 Servo board revision 03 circuit schematic 3 8 160 B 8 Servo board revision 03 circuit schematic 4 8 161 KEEN 162 B 10 Servo board revision 03 circuit schematic 6 8 163 B 11 Servo board revision 03 circuit schematic 7 8 164 B 12 Servo board revision 03 circuit schematic 8 8 165 B 13 Radio board revision 03 circuit schematic 1 5
224. z Z f aoazsng lt 30 ES E 8 L u3x1zsng 3 d Ar iHe OF Exyzsng lt y zsng cLOAHS9NS en EI i e an9 99 g img 9 LxLLSng cf al z n el 99 LSN ET V 9 1 99 1SNg lt S 3 Lux LLsng d gt s i e EXHiSng lt ep T OL H Isna cLOAHS9NS en EI uf i S 9 INOyT1LSALS 1 09AESNG SE E J va ZA L xLosng por g z v L vis L 99A05ng e tic A ae 1 09AZsng vO 9 ZO 10 ad C lt 8 J eq Lux L eng d z n n onp nu LA Mor1ESALS ioonisng iH J cd i Lixyosng L 399ASng EIDA SE H osna WOr11Sd1S EET J iq cLOAHS9NS LA 6 9 S z L 179 I Report ina F Electric Owl APPENDIX B SCHEMATICS AND CAD DRAWINGS 6 JO Z Abed 20 UoISIA 1 asempJey pleoq Oc JO Ii wayos PNN 4z g n6ij 8 L 9 S v z L eDpug Aer Ag NMYYA O Z0 39Vd NOISIA3H qi qui ZO UOISIJA DIEO Dd 49 0410090J9 A oL 02H I c 4 do y ve E m ge 19 lag 13Sau LOSOL LIWLX Lud 7g ZHN 8c4E 7 EJ ina dol Tio f T t e T z i ye VL VQ Idd 2OSO LZ1VLX 08d gg 029 20001 dnOL 3400 4U001 3U00L SNOL KIJA HAV Idd Zei G t GeO veo G Z it inoi LXLisng Uxiesng 1 J EE L i i E VA d iss A Zp 20d M9S LOX

Design of an Unmanned Aerial Vehicle for Martian Exploration

Contents

Download Pdf Manuals

Related Search

Related Contents