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NAV440 User Manual

1. n cs lt CR gt lt LF gt ASCII String Name Description Format Example Message ID GPGGA string GPGGA GGA protocol header hhmmss ss hhmmss sss 092725 00 UTC Time Current time Latitude dddmm mmmm 4717 11399 Latitude Degrees minutes N S Indicator N character N N north or S south Longitude Longitude dddmm mmmm 00833 91590 Degrees minutes E W indicator E character E E east or W west Position Fix Indicator FS 1 digit 1 See Table below 8 Satellites Used NoS V numeric 8 Range 0 to 12 HDOP numeric 1 01 HDOP Horizontal Dilution of Precision msl numeric 499 6 MSL Altitude m m character M Units Meters fixed field Altref blank 48 0 Geoid Separation m m blank M Units Meters fixed field 7 Age of Differential Corrections sec DiffAge numeric Blank Null fields when DGPS is not used DiffStation numeric 0 Diff Reference Station ID cs hexadecimal 5B Checksum lt CR gt lt LF gt End of message Doc 7430 0131 01 Rev E Page 69 440 Series User s Manual Crossb w Fix Status Description 0 No fix Invalid 1 Standard GPS 20 30 2 Differential GPS 6 Estimated DR Fix 12 Appendix C Sample Packet Parser Code 12 1 Overview This appendix includes sample code written in ANSI C for parsing packets from data sent by the 4
2. ASCII 2 byle payload Description Type Products Available Mnemonic packet byte type length U2 gt U1 gt Link Test PK 0x504B 0 Ping Command Input Reply ALL and Response Message CH 0x4348 N Echo Command Input Reply ALL and Response Message Interactive Commands GP 0x4750 2 Get Packet Input ALL Request Message AR 0x4152 0 Algorithm Reset Input Reply VG AHRS Message SR 0x5352 0 Software Reset Input Reply ALL Message NAK 0 1515 2 Error ALL Message WC 0x5743 2 Calibrate Input Reply 5 Command and Message Response CC 0x4343 8 Calibration Reply AHRS NAV Completed Message Output Messages Status amp Other Polled Only ID 0 4944 5 N Identification Output ALL Data Message VR 0x5652 5 Version Data Output ALL Message TO 0x5430 28 Test 0 Detailed Output ALL BIT and Status Message Output Messages Measurement Data Continuous or Polled 50 0 5330 30 Scaled 0 Output AHRS Data Message 51 0 5331 24 Scaled Sensor 1 Output ALL Data Message 52 0 5332 28 Scaled Sensor2 Output ALL Doc 7430 0131 01 Rev E Page 40 440 Series User s Manual Data Message A0 0x4130 30 Angle 0 Data Output AHRS NAV Message Al 0x4131 32 Angle 1 Data Output AHRS Message A2 0x4132 30 Angle
3. 42 7 1 1 Pig eR pee em o RI ee 42 TAD Ping Responses 42 7 1 3 Ree c eU ep ee ei ee cgi esie Agee 42 7 1 4 Echo ore Te EET EH TEUER 42 7 2 Interactive Commands is nur ee pape bees 42 7 2 1 Get Packet Request e RERO 42 7 2 2 Algorithm Reset Commands L RU rei tt p re Ree Linda 43 7 2 3 Algorithm Reset Resporse ate dp Oeo td 43 7 2 4 Software Reset Command i tefle ern na ee ec n onte eh 43 7 2 5 Software ResetREspoOnse ern ep te en e ore n at s ive peti sone 43 7 2 6 Calibrate Command r n L S u ede ieee 43 7 2 7 Calibrate Acknowledgement Response aaa susan A han iha ama A qhu 44 7 2 8 Calibration Completed Parameters Response a ener 44 7 2 9 Error Responses eben DI e mI 45 7 3 Output Packets Polled eoi eret ee eere rete eR ete ERE EU ES ete evan e Ree Euer ep des 45 7 3 1 Identification Data Packetu u onde fee RUE ei tt re REC ee rna 45 7 3 2 Version Data Packet 25 e nonu ore bane ate di Ota mated 45 7 3 3 Test 0 Detailed and Status Packet 46 7 4 Output
4. 3 1 3 1 Mechanical Size and Footprint ii Cuan ied orate a dam tea rame 3 1 3 2 Connector Pin amp Operating Voltage Cutrrent a nre nne nenne 3 1 3 3 Software Compatibilityua assays aku 3 1 3 4 Operating Performance and Accuracy as 3 Connections Antik Wea aa n a Gu ik h aaa 4 2 1 ConnectiopS et p RT AG rm D tse Ut u tip dae bebe 4 2 2 JJ O C ble s a repetere dida ba ede eei acere baie 4 2 3 Power Input and Power Input Ground u L SS nennen enne tene tree tret trente 4 2 44 Case Ground eno REG e RR RENE 5 2 5 Serial Data Interface A RR REOR E asa asus 5 2 6 Serial GPS Interface NA V440 B Port Output enne enne ener entente nns 5 24 External GPS Aiding VG440 AHRS440 B Port Input ener 5 2 8 Hardware BIT Error ed eth ee e ee Er enti n rt IH o npe en eo 6 2 9 1 PPS Input Interface IMU VG AHRS440 enne enne nennen nentes intent 6 2 10 1 PPS Output Interface NAAMAAO u eret tn t 6 2 11 GPS Antenna Co
5. 67 10 2 440 Series Outline Drawing AHRS NAV trennen 68 11 Appendix B NMEA Message Format needed te cenare a Fed RR Har Ede e 69 11 1 GGA GPS fix datas Suasana e atelente d Pie tie c ae E 69 12 Appendix C Sample Packet Parser Codes u u u eoe etel In ug decet citet 70 IPAE ODIUM 70 122 Gode lis ng 4 5er RR Dm EA EE Pt OPI m ee d P OPE ed 71 13 Appendix D Sample Packet D8606dIDpa l u eoa pte id eee a hec fa dee 76 14 Warranty and Support Informiati n u ocio cer terret eem qe tate creo Saas e E eem PORE E creer lo 79 I 79 14 2 Contact Directory iiis nos ae e bant ae eee D RR rite re ch E i ar reo EE 79 1453 Procedure E E 79 1433 1 Atathorizatione sc eere endete le e te eee ee eee e edet eese P dde ces 79 14 3 2 Identification and Protection i eee epe ter tree Fee He aee inde rn ede ordo tan 79 143 3 Sealingithe Contamert eso ies e ETE RU PO REDE 79 14 3 4 Marking stie ERR OP RE E REO de e bU ERO e REOR EAE e s 79 14 3 5 Shipping Address eite OH a ER die eed tue Eg 80 14 4 Waranty seti tee e ee ette nts fet eee ete E PL ER
6. 50 Payload Contents Byte Name Format Scaling Units Description Offset 0 xAccel 12 20 2 16 g X accelerometer 2 yAccel 12 20 2 16 g Y accelerometer 4 zAccel 12 20 2 16 g Z accelerometer 6 xRate 2 7 pi 2 16 rad s X angular rate 1260 2 16 sec 8 yRate 12 7 pi 2 16 rad s Y angular rate 12602716 sec 10 zRate 2 7 pi 2 16 rad s Z angular rate 12602716 sec 12 xMag 12 2 2 16 Gauss X magnetometer 14 yMag 12 2 2 16 Gauss Y magnetometer 16 zMag 12 2 2 16 Gauss Z magnetometer 18 xRateTemp 12 200 2 16 X rate temperature 20 yRateTemp 12 200 2 16 Y rate temperature 22 zRateTemp 12 200 2 16 deg C Zrate temperature 24 boardTemp 2 200 2 16 C CPU board temperature 26 GPSITOW U2 truncated ms GPS ITOW lower 2 bytes 28 BlTstatus U2 Master BIT and Status 7 4 2 Scaled Sensor Data Packet 1 Default IMU Data Scaled Sensor Data S1 0x5331 Packet Length Payload 0x5555 0x5331 S1 payload CRC U2 gt This packet contains scaled sensor data Data involving angular measurements include the factor pi in the scaling and can be interpreted in either radians or degrees Angular rates scaled to range of 3 5 pi pi or 630 deg sec to 630 deg sec Accelerometers scaled to a range of 10 10 g Temperature scaled to a range of 100 100 C 61 Payload Contents Byte Name Forma
7. 80 Page iv Doc 7430 0131 01 Rev E 440 Series User s Manual Crossb w About this Manual The following annotations have been used to provide additional information 4 NOTE Note provides additional information about the topic EXAMPLE Examples are given throughout the manual to help the reader understand the terminology IMPORTANT This symbol defines items that have significant meaning to the user WARNING The user should pay particular attention to this symbol It means there is a chance that physical harm could happen to either the person or the equipment The following paragraph heading formatting is used in this manual 1 Heading 1 1 1 Heading 2 1 1 1 Heading 3 Normal Doc 7430 0131 01 Rev E Page v 440 Series User s Manual 1 1 Manual Overview 1 Introduction Crossb w This manual provides a comprehensive introduction to Crossbow s 440 Series Inertial System products For users wishing to get started quickly please refer to the three page quick start guide included with each shipment content in each section and suggests how to use this manual Table 1 Manual Content The following table highlights the Manual Section Who Should Read Section 1 Manual Overview All customers should read sections 1 1 and 1 2 Customers who have previously used Crossbow s 300 400 Series or 420 Series products should also read Section 1 3 Section 2 Con
8. if DeleteQueue amp tempchar queue ptr break return i J E E K K K K k RR KA A k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k kk k k k kk k k k k k FUNCTION Size ARGUMENTS queue_ptr is pointer to the queue RETURNS return the number of items in the queue KK AR E E IK E AE A E E ck A E kk kCk k AR k k k k k kk k k k A k ck ck k k ck kck k k K k k I k k k int Size QUEUE TYPE queue ptr return queue ptr count BR RK KK RRR KK A RR AA RRR FUNCTION Empty ARGUMENTS queue ptr is pointer to the queue RETURNS return 1 if empty 0 if not k k k k k Ck k k ck ck k K k K K k K k K K K K Ck k ok K K k K k K K K K k K K K K Ok ok K K int Empty QUEUE TYPE queue ptr return queue ptr gt count lt 0 BRK KR RR k k RA RA k k k k k k k k k k k k k k k k k k k k k k k k kk k k k k k FUNCTION Full ARGUMENTS queue_ptr is pointer to the queue RETURNS return 1 if full 0 if not full K K K K K K K k A K K k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k S int Full QUEUE queue ptr return queue ptr count gt MAXQUEUE Doc 7430 0131 01 Rev E Page 75 440 Series User s Manual Crossb w 13 Appendix D Sample Packet Decoding Example payload from Angle Data Packet 2 A2 5555 4132 1e 0006ffe4ed91fff9fffdffedfff7fff9 3312c642ce12d48500010b51c0300 6945 preamble lensth CRC inva
9. char peekByte QUEUE TYPE queue ptr unsigned int index char byte int firstIndex firstIndex queue ptr front index MAXQUEUE byte queue ptr entry firstIndex return byte k k k k k k k kk k k FUNCTION peekWord returns 2 byte word from buffer without popping ARGUMENTS queue_ptr is pointer to the queue to return word from index is offset into buffer to which to return RETURNS 2 byte word REMARKS does not do boundary checking please do this first eA A unsigned short peekWord QUEUE queue ptr unsigned int index unsigned short word firstIndex secondIndex firstIndex queue ptr front index MAXQUEUE secondIndex queue ptr front index 1 MAXQUEUE word queue ptr entry firstIndex lt lt 8 amp OxFF00 word 0x00FF amp queue ptr entry secondIndex return word J E E d k k k k k k K K k K k K K K K k K K K K K K K K K k K K K K K K K K K K K K K K K K KOK K K KOK K K K K KOK KKK FUNCTION Pop discard item s from queue Crossbgw Doc 7430 0131 01 Rev E Page 74 440 Series User s Manual ARGUMENTS queue ptr is pointer to the queue numToPop is number of items to discard RETURNS return the number of items discarded A int Pop QUEUE TYPE queue ptr int numToPop int i 0 char tempchar for i 0 i lt numToPop i
10. WC Payload Contents Byte Name Format Scaling Units Description Offset 0 calibrationRequest U2 The requested calibration task Doc 7430 0131 01 Rev E Page 43 440 Series User s Manual Crossb w Currently magnetic alignment is the only function supported by the calibrate command There are two magnetic alignment procedures supported 1 magnetic alignment with automatic yaw tracking termination and magnetic alignment without automatic termination calibrationRequest Description Begin magnetic alignment without automatic termination Rotate vehicle through gt 360 degrees yaw and then send 0x000B calibration 0x0009 request to terminate Terminate magnetic alignment The unit will send a CC response containing the hard iron and soft iron values To accept the 0x000B parameters store them using the write magnetic calibration command Begin magnetic calibration with automatic termination Rotate the unit through 380 degrees in yaw The unit will send a CC response containing the hard iron and soft iron values upon completion of the turn To accept the parameters store them using the write magnetic 0x000C calibration command Write magnetic calibration The unit will write the parameters to 0x000E EEPROM and then send a calibration response 7 2 7 Calibrate Acknowledgement Response Calibrate WC 0x5743 Packet Type 0 5555 0x5743 lt WC payload
11. Orientation X Axis Y Axis Z Axis Field Value 0x0000 Ux Uy Uz 0x0009 Ux Uy Uz 0x0023 Uy Ux Uz 0x002A Uy Ux Uz 0x0041 Ux Uy Uz 0x0048 0 Uy Uz 0x0062 Uy Ux Uz 0 006 Uy Ux Uz 0x0085 Uz Uy Ux 0x008C Uz Uy Ux 0x0092 Uy Uz Ux 0x009B Uy Uz Ux 0x00C4 Uz Uy Ux 0x00CD Uz Uy Ux Doc 7430 0131 01 Rev E Page 55 440 Series User s Manual 0x00D3 Uy Uz Ux 0x00DA Uy Uz Ux 0x01 11 Ux Uz Uy 0x0118 Ux Uz Uy 0x0124 Uz Ux Uy 0x012D Uz Ux Uy 0x0150 Ux Uz Uy 0x0159 Ux Uz Uy 0x0165 Uz Ux Uy 0x016C Uz Ux Uy An example of orientation field value 0x12D is shown below Z Uy 85 User Behavior Switches This field allows on the fly user interaction with behavioral aspects of the algorithm Description Bits Meaning Free Integrate 0 0 use feedback to stabilize the algorithm 1 2 6DOF inertial integration without stabilized feedback Use Mags 0 Do not use mags to stabilize heading heading will run open loop or be stabilized by GPS track 1 Use mags to stabilize heading Use GPS 0 Do not use GPS to stabilize the system 1 Use GPS when available Stationary Yaw Lock 0 Do not lock yaw when GPS speed is near zero 0 75 m s 1 Lock yaw when GPS speed is near Zero Crossb w Doc 7430 0131 01 Rev E Page 56
12. C Doc 7430 0131 01 Rev E Page 48 440 Series User s Manual A0 Payload Contents Byte Name Format Scaling Units Description Offse 0 rollAngle 12 2 pi 2 16 Radians Roll angle 360 727161 3 2 pitchAngle 2 2 pi 2 16 Radians Pitch angle 360 727161 q 4 yawAngleMag 2 2 pi 2 16 Radians Yaw angle magnetic north 360 727161 q 6 xRateCorrected 12 7 pi 2 16 rad s X angular RateCorrected 1260 2 16 sec 8 yRateCorrected 12 7 pi 2 16 rad s Y angular RateCorrected 1260 2 16 sec 10 zRateCorrected 12 7 pi 2 16 rad s Z angular RateCorrected 1260 2 16 sec 12 xAccelCorrected l2 20 2 16 g X AccelCorrected 14 yAccelCorrected 12 20 2 16 g Y AccelCorrected 16 zAccelCorrected 12 20 2 16 g Z AccelCorrected 18 xMag 12 2 2 16 Gauss X magnetometer 20 yMag 12 2 2 16 Gauss Y magnetometer 22 zMag 12 2 2 16 Gauss Z magnetometer 24 xRateTemp 12 200 2 16 deg X rate temperature 26 GPSITOW U2 truncated ms GPS ITOW lower 2 bytes 28 BITstatus U2 Master BIT and Status Crossb w 7 45 Angle Data Packet 1 Default AHRS Data Angle Data 1 0x4131 Packet Type Payload 0 5555 0x4131 A1 payload CRC U2 gt This packet contains angle data and selected sensor data scaled in most cases to a signed 2 16 2 s complement number Data involving angular measurements include the factor pi in the scaling and c
13. RF Payload Contents Byte Offset Name Format Scaling Units Description 0 numFields U1 The number of fields read 1 fieldO U2 The first field ID read 3 fieldOData U2 The first field ID s data read 5 field1 U2 The second field ID read 7 field1 Data U2 The second field ID s data read ee U2 numFields 4 3 field 02 last field ID read numFields 4 1 field Data U2 The last field ID s data read 8 11 Get Fields Command Get Fields GF 0x4746 Doc 7430 0131 01 Rev E Page 59 440 Series User s Manual Crossb w PacketType Length Payload 0 5555 0 4746 1 numFields 2 GF Data CRC U2 gt This command allows the user to get the unit s current configuration fields NumFields is the number of fields to get The field0 fieldl etc are the field IDs to get GF may be used to get configuration calibration and algorithm fields from RAM Multiple algorithm fields will not necessarily be from the same algorithm iteration If at least one field is successfully collected the unit will respond with a get fields response with data containing the field IDs of the successfully received fields If any field is unable to be received the unit will respond with an error response Note that both a get fields and an error response may be received as the result of a get fields command GF Payload Contents Byte Offset Nam
14. 440 Series User s Manual Crossb w Restart on Over range 4 0 Do not restart the system after a sensor over range 1 restart the system after a sensor over range Dynamic Motion 5 0 is static force high gain corrections 1 vehicle is dynamic use nominal corrections Reserved 6 15 N A 8 6 Hard and Soft Iron Values These fields allow access to hard iron bias and soft iron scale ratio values for magnetometer alignment Field Name Field ID Format Scaling Units X Hard Iron Bias 0x0009 2 2M6 Gauss Y Hard Iron Bias 0x000A 2 2M6 Gauss 2 Soft Iron Scale Ratio 0 000 U2 2 216 The hard iron bias values are scaled from 1 1 Gauss These values are subtracted from the tangent plane magnetometer vector before heading is calculated The soft iron scale ratio is scaled from 0 2 and is multiplied by the tangent plane x magnetometer value before heading is calculated 8 7 Heading Track Offset This field is used to set the offset between vehicle heading and vehicle track to be used by the navigation mode filter when no magnetometer heading measurements are available Field Name Field ID Format Scalin Units Heading Track Offset 2 pi 2 16 Radians heading track 0x000C 12 360 2716 4 8 8 Commands to Program Configuration 8 8 1 Write Fields Command Write Fields WF 0x5746 Packet Type Length Payload 0x5555 0x5746 1 numFields 4
15. Valid Values description 0 1 2 5 10 quiet 100Hz 50Hz 25Hz 20Hz 10Hz Packet rate divider 0x0001 20 25 50 5Hz 2Hz Unit BAUD rate 0x0002 0 1 2 3 9600 19200 38400 57600 Not all output packets available for all Any output products See detailed product Continuous packet type 0 0003 packet type descriptions 1338 26785 Sets low pass cutoff for rate sensors Analog Filter Clock 1 0 0004 40 2 Hz Cutoff Freq 15e5 28 value 1 1338 26785 Sets low pass cutoff for z accel Cutoff Analog Filter Clock 2 0x0005 40 2 Hz Freq 15e5 28 value 1 1338 26785 Sets low pass cutoff for x and y accel Analog Filter Clock 3 0x0006 40 2 Hz Cutoff Freq 15e5 28 value 1 Pas MT Determine forward rightward and Orientation 0x0007 See below downward facing sides Free Integrate Use Mags Use GPS User Behavior Switches 0x0008 Any Stationary Yaw Lock X Hard Iron Bias An I2 scaled from 1 1 Y Hard Iron Bias I2 scaled from 1 1 Soft Iron Scale Ratio 0x000B U2 scaled from 0 2 Heading Track Offset Heading Track Offset to use in NAV filter 0x000C Any track update mode Note BAUD rate SF has immediate affect Some output data may be lost Response will be received at new BAUD rate 82 Continuous Packet Type Field This is the packet type that is being continually output The supported packet depends on the model number Please refer to Section 6 4 for a complete list of the av
16. www xbow com WARNING This product has been developed by Crossbow exclusively for commercial applications It has not been tested for and Crossbow makes no representation or warranty as to conformance with any military specifications or that the product is appropriate for any military application or end use Additionally any use of this product for nuclear chemical biological weapons or weapons research or for any use in missiles rockets and or UAV s of 300km or greater range or any other activity prohibited by the Export Administration Regulations is expressly prohibited without the written consent of Crossbow and without obtaining appropriate US export license s when required by US law Diversion contrary to U S law is prohibited 02009 Crossbow Technology Inc All rights reserved Information in this document is subject to change without notice Crossbow SoftSensor NAV440 AHRS440 VG440 VGS440 and IMU440 are registered trademarks of Crossbow Technology Inc Other product and trade names are trademarks or registered trademarks of their respective holders 440 Series User s Manual Crossb w 1 Table of Contents Introduction 5 eee E Dead HE 1 1 1 Manual Ov rvi W sura Bie ny beu eee iet 1 12 Overview of the 440 Series Inertial Systems essent nennen trennen inneren tenente trennen enne 2 1 3 Summary of Major Changes from the 300 400 Series and the 420
17. 4Hz Hz 557600 is the preferred baud rate for optimum performance Doc 7430 0131 01 Rev E Page 5 440 Series User s Manual Crossb w The GPS serial communication port should be configured to 8 data bits 1 start bit 1 stop bit no parity bit and no flow control 2 8 Hardware BIT Error Output The hardware BIT error output pin is the ultimate indication of system failure This indication is available in most software output packets as the masterFail flag It is the logical AND of the hardwareError comError and softwareError flags monitored by the system In the event of a communication failure the hardware BIT error pin may be used to detect a masterFail assertion This pin is open collector and requires a 1k to 10k ohm pull up resister The system will drive this pin low to assert a system failure 29 1 PPS input Interface IMU VG and AHRS440 The 1PPS input signal allows the user of IMU VG and AHRS 440 products to force synchronization of sensor data collection to rising edge signal The signal must maintain 0 0 0 2 V zero logic and 3 0 5 0 volts high logic and stay within 100ms of the internal system 1 second timing Sending this signal to the system will align the sensor data collection and algorithm processing to its rising edge and 105 boundaries thereafter When the system is synchronized to 1 PPS the hardwareStatus 2unlocked1 PPS flag will be zero otherwise it will be one 2 10 1 PPS Output Interface NAV44
18. Once the settings have been altered a Success box will appear at the bottom of the page gt IMPORTANT Caution must be taken to ensure that the settings selected are compatible with the system that is being configured In most cases FAIL message will appear if incompatible selections are made by the user however it is the users responsibility to ensure proper configuration of the unit gt IMPORTANT Unit orientation selections must conform to the right hand coordinate system as noted in Section 4 1 of this user manual Selecting orientations that do not conform to this criteria are not allowed Figure 5 Unit Configuration Unit Configuration General Advanced BIT Configuration Field Modify Current Value Value to Set Baud Rate 71 57600 baud 57600 baud Packet Type Navo gt Packet Rate 100 2 100 Hz X x Y z x 3f z Orientation a vpUy viz X UX Vey 254 GPS Baud Rate 38400 baud Auto baud GPS Protocol Novatel binary Auto detect Get All Values Set Values Temporary reset after reboot C Permanant saved after reboot Doc 7430 0131 01 Rev E Page 12 440 Series User s Manual Crossb w 3 40 Advanced Configuration Users who wish to access some of the more advanced features of NA V VIEW 2 X and the 440 Series products can do so by selecting the Advanced tab at the top of the Unit Configuration window WARNING
19. Users are strongly encouraged to read and thoroughly understand the consequences of altering the settings in the Advanced tab before making changes to the unit configuration These settings are discussed in detail in Chapter 4 below Behavior switches are identified at the top of the page with marked boxes A blue box will appear if a switch has been enabled similar to the figure below The values can be set in the same manner as noted in the previous section To set a value users select the appropriate Modify checkbox on the left side of the menu and select or enable the appropriate value they wish to set At the bottom of the page users have the option of temporarily or permanently setting values When all selections have been finalized simply press the Set Values button to change the selected settings Figure 6 Advanced Settings Unit Configuration General Advanced BIT Configuration Field Modify Current Value Value to Set User Behavior Switches Freely Integrate B use Mags Use GPS O Stationary Yaw Lock Restart Over Range Dynamic Motion 517115151711 X Hard Iron Bias 0 00000 ES Y Hard Iron Bias 0 00000 ij Soft Iron Scale Ratio 0 00000 Heading Track Offset 0 00 Turn Switch Threshold 0 40 Filter XZ Accel 10 00 ES Filter Y 10 00 Filter Rate Sensor Get Al Values Set Values Temporary reset after reboot Permanant
20. WF payload CRC U2 gt This command allows the user to write default power up configuration fields to the EEPROM Wiriting the default configuration will not take affect until the unit is power cycled NumFields is the number of words to be written The field0 fieldl etc are the field IDs that will be written with the fieldOData field Data etc respectively The unit will not write to calibration or algorithm fields If at least one field is successfully written the unit will respond with a write fields response containing the field IDs of the successfully written fields If any field is unable to be written the unit will respond with an error response Note that both a write fields and an error response may be received as a result of a write fields command Attempts to write a field with an invalid value is one way to generate an error response A table of field IDs and valid field values is available in Section 8 1 WF Payload Contents Byte Offset Name Format Scaling Units Description 0 numFields U1 The number of fields to write 1 fieldO U2 The first field ID to write 3 fieldOData U2 The first field ID s data to write 5 field1 U2 The second field ID to write 7 field1Data U2 The second field ID s data Doc 7430 0131 01 Rev E Page 57 440 Series User s Manual Crossb w s U2 YN numFields 4 3 field U2
21. position 5 3 Rotorcraft Rotorcraft is a category of heavier than air flying machines that use lift generated by rotors They may also include the use of static lifting surfaces but the primary distinguishing feature being lift provided by rotating lift structures Rotorcraft includes helicopters autogyros gyrodynes and tiltrotors The rotor blade dynamics itself is much faster than that of the fixed wing aircraft and contains high frequency components At the same time however it may cause severe vibrations on the airframe Also the overall dynamics translational and rotational motion of the rotor craft is much slower than the fixed wing aircraft due to a mechanical mechanism of rotors generating the aerodynamic forces and moments Table 18 provides the recommended advanced settings for two different dynamic conditions Doc 7430 0131 01 Rev E Page 34 440 Series User s Manual Table 18 Recommended Advanced Settings for Rotorcraft Crossb w D need AHRS440 or NAV440 Dynamic Condition Recommended High Dynamics Settings with uncoordinated tail motion UseMags ON ON UseGPS ON ON lt 4 Freelylntegrate OFF OFF lt 2g Stationary Yaw Lock OFF OFF Restart Over Range OFF ON Dynamic Motion ON ON Turn Switch Threshold 1 0 deg s 30 0 deg s 8 XY Filter Accel 5 Hz 5 Hz Z Filter Accel 5 Hz 5 Hz Filter Rate Sensor 20 Hz 20 Hz The helicopter can change its head
22. saved after reboot 3 11 Bit Configuration The third and final tab of the unit configuration window is Bit Configuration This tab allows the users to alter the logic of individual status flags that affect the masterStatus flag in the master BITstatus field available in most output packets By enabling individual status flags users can determine which flags are logically OR ed to generate the masterStatus flag This gives the user the flexibility to listen to certain indications that affect their specific application The masterFail and all error flags are not configurable These flags represent serious errors and should never be ignored Doc 7430 0131 01 Rev E Page 13 440 Series User s Manual Crossb w Figure 7 BIT Configuration Unit Configuration General Advanced BIT Configuration By enabling a given status the signal will be included the corresponding category BIT and in the master status sent by the DMU Field Modify Current Value Enable Disable Hardware Status Enable Unlocked 1PPS Unlocked Internal GPS No DGPS L Unlocked Eeprom Software Staus Enable 7 O Algorithm Initializing High Gain O Altitude Only Turn Switch Sensor Status Enable 7 Sensor Over Range Comm Status Enable 7 O No External GPS Get All Values Set Values Temporary reset after reboot C Permanant saved after reboot 3 12 Mag Alignment Procedure IMPORTA
23. 2 Data Output VG AHRS NAV Message NO Ox4E30 32 Nav 0 Data Output VG AHRS NAV Message NI Ox4E31 42 Nav 1 Data Output VG AHRS NAV Message Bl 0x4231 18 Short Packet Output OEM Only Angle B1 Data Message B2 0x4232 10 Short Packet Output OEM Only Angle B2 Data Message Advanced Commands WF 0x5746 numFields 4 Write Fields Input ALL 1 Request Message WF 0x5746 numFields 2 Write Fields Reply ALL 1 Response Message SF 0x5346 numFields 4 Set Fields Input ALL 1 Request Message SF 0x5346 numFields 2 Set Fields Reply ALL 1 Response Message RF 0x5246 numFields 2 Read Fields Input ALL 1 Request Message RF 0x5246 numFields 4 Read Fields Reply ALL 1 Response Message GF 0x4746 numFields 2 Get Fields Input ALL 1 Request Message GF 0x4746 numFields 4 Get Fields Reply ALL 1 Response Message Crossb w Doc 7430 0131 01 Rev E Page 41 440 Series User s Manual Crossb w 7 Communicating with the 440 Series 71 Link Test 7 1 1 Ping Command Ping PK 0x504B 0x5555 0x5048 The ping command has no payload Sending the ping command will cause the unit to send a ping response To facilitate human input from a terminal the length and CRC fields are not required Example 0x5555504B009ef4 or 0x5555504B 7 1 2 Ping Response Ping 0x504B Packet Type 0 5555 0x504B CRC U2 gt The unit will send this packet in response to a ping command 7 1 3 Echo Command E
24. DSP using FIR filters The factory calibration data stored in EEPROM is used by the DSP to remove temperature bias misalignment scale factor errors and non linearities from the sensor data Additionally any advanced user settings such as axes rotation are applied to the IMU data The 100Hz IMU data is continuously being maintained inside the IMU440 Digital IMU data is output over the RS 232 serial link at a selectable fixed rate 100 50 25 20 10 5 or 2 Hz or on as requested basis using the GP Get Packet command The digital IMU data is available in one of several measurement packet formats including Scaled Sensor Data S1 Packet and Delta Theta Delta V S2 Packet In the Scaled Sensor Data S1 Packet data is output in scaled engineering units In the Delta Theta Delta V format S2 Packet scaled sensor data is integrated with respect to the time of the last output packet and the data is reported in units of accumulated 1 delta degrees and meters second See Section 7 of the manual for full packet descriptions gt IMPORTANT The Delta Theta Delta V packet is only recommended for use in continuous output mode at 5Hz or greater Polled requests for this packet will produce values accumulated since the last poll request and thus are subject to overflow data type wrap around 4 2 1 IMU440 Advanced Settings The IMU440 advanced settings are described in Table 7 below of the advanced settings ar
25. P Sensor N Integration to N Integration to 100 Hz Chain Calibration Attitude Velocity GPS X Y Z Body n Axes Rotation Position Output Accelerometers a Li u LI Unit Settings amp Profile W Extended Kalman Filter EKF Built In Test W Drift Correction Module m amp Status Data i Availabe to W User LI B m a Kalman Filter and Dynamic State Model m B a K E E LI B LI Hard Soft Iron Free Integrate UseGPS Calibration TurnSwitch Stationary Yaw UseMags Threshold Lock d LI LI unuEEEREREEREEREE m s a E B Aiding Senso LI LI 2 Gravity Reference GPS Data a Magnetometers Internal Internal External 5 1 a LI Computation m u Simplified functional block diagrams for NAV AHRS and VG series products derived from Figure 10 are shown in Figure 11 to highlight key features of each product The 440 series products are mainly differentiated by types of aiding sensors used in the EKF for the drift correction of the 6 DOF inerti
26. Page 61 440 Series User s Manual Crossb w calibrationCRCError magAlignOutOfBounds gt masterStatus hardwareStatus e hardwareStatus Field unlocked1PPS enabled by default on NAV unlockedInternalGPS enabled by default on NAV noDGPS unlockedEEPROM comStatus e comStatus Field noExternalGPS enabled by default on VG and AHRS SoftwareStatus e softwareStatus Field algorithmInitialization enabled by default highGain enabled by default attitudeOnlyAlgorithm turnSwitch sensorStatus e sensorStatus Field overRange enabled by default 9 2 Master BIT and Status BlTstatus Field The BITstatus field is the global indication of health and status of the 440 Series product The LSB contains BIT information and the MSB contains status information There are four intermediate signals that are used to determine when masterFail and the hardware BIT signal are asserted These signals are controlled by various systems checks in software that are classified into three categories hardware communication and software Instantaneous soft failures in each of these four categories will trigger these intermediate signals but will not trigger the masterFail until the persistency conditions are met There are four intermediate signals that are used to determine when the masterStatus flag is asserted hardwareStatus sensorStatus comStatus and softwareStatus masterStatus is the logical OR of t
27. Rev E Page 25 440 Series User s Manual Crossb w comStatus 10 0 nominal 1 No External GPS Comm Status softwareStatus 11 0 nominal 1 Algorithm Initialization or Status High Gain sensorStatus 12 0 nominal 1 Sensor Over Range Status Reserved 13 15 N A The VG440 also allows a user to configure the Status byte within the BIT message To configure the word select the BIT Configuration tab from the Unit Configuration menu The dialog box allows selection of which status types to enable hardware software sensor and comm Like the IMU440 Crossbow recommends for the vast majority of users that the default Status byte for the VG440 is sufficient For users who wish to have additional visibility to when the VG440 EFK algorithm estimates that the VG440 is turning about its Z or Yaw axis the softwareStatus bit can be configured to go high during a turn In other words the turnSwitch will turn on the softwareStatus bit In the VG440 the turnSwitch is by default set at 10 0 deg sec about the z axis 44 5440 Theory of Operation The AHRS440 supports all of the features and operating modes of the IMU440 and VG440 and it includes an additional internal 3 axis magnetometer and associated software running on the DSP processor for the computation of dynamic heading as well as dynamic roll and pitch The product name AHRS440 stands for Attitude Heading Reference System 440 and it is indicative of
28. The GPS receiver requires proper antennae installation for operation See section 4 4 1 for information and tips regarding installation and calibration 4 5 1 440 Magnetometer Calibration and Alignment The 440 requires the three axis magnetic field sensor to be calibrated while installed in its operating environment See section 4 4 1 for information and tips regarding installation and calibration and why magnetic calibration is necessary Please review this section of the manual before proceeding to use the NA V440 4 5 2 NAV440 Advanced Settings In addition to the configurable baud rate packet rate axis orientation and sensor low pass filter settings the NA V440 provides additional advanced settings which are selectable for tailoring the NAV440 to a specific application requirements The NA V440 advanced settings are shown in Table 13 below Table 13 NAV440 Series Advanced Settings Setting Default Comments Baud Rate 38 400 9600 19200 57600 also available baud Packet 50 51 52 0 1 2 also available Packet 25 Hz This setting sets the rate at which selected Packet Type packets are output If Rate polled mode is desired then select Quiet If Quiet is selected the NA V440 will only send measurement packets in response to GP commands Orientation See To configure the axis orientation select the desired measurement for each axes Fig 12 NAV VIEW 2 X will show the corres
29. The last field ID to write numFields 4 1 field Data U2 The last field ID s data to write Write Fields Response Write Fields WF 0x5746 Packet Length Payload 0x5555 0x5746 1 numFields 2 WF payload CRC 02 gt The unit will send this packet in response to a write fields command if the command has completed without errors WF Payload Contents Byte Offset Name Format Scaling Units Description 0 numFields U1 The number of fields written 1 fieldO U2 The first field ID written 3 field1 U2 The second field ID written U2 More field IDs written numFields 2 Field U2 The last field ID written 1 8 8 2 Set Fields Command Set Fields SF 0 5346 Packet Type Payload 0 5555 0x5346 1 numFields 4 lt SF payload gt lt CRC U2 gt This command allows the user to set the unit s current configuration SF fields immediately which will then be lost on power down NumFields is the number of words to be set The field0 fieldl etc are the field IDs that will be written with the field0Data field Data etc respectively This command can be used to set configuration fields The unit will not set calibration or algorithm fields If at least one field is successfully set the unit will respond with a set fields response containing the field IDs of the successfully set fields If any field is unable to be set
30. details for configuring the masterStatus flags Table 14 shows the BIT definition and default settings for BIT programmable alerts in the NA V440 Table 14 NAV440 Default BIT Status Definitions BITstatus Field Bits Meaning Category masterFail 0 0 normal 1 fatal error has occurred BIT HardwareError 1 0 normal 1 internal hardware error BIT comError 2 0 normal 1 communication error BIT softwareError 3 0 normal 1 internal software error or BIT magAlignOutofBounds Reserved 4 7 masterStatus 8 0 nominal 1 one or more status alert Status hardwareStatus 9 0 nominal 1 Internal GPS unlocked or Status 1PPS invalid comStatus 10 Disabled Status softwareStatus 11 0 nominal 1 Algorithm Initialization or Status high gain sensorStatus 12 0 nominal 1 Sensor Over Range Status Reserved 13 15 N A The NA V440 also allows a user to configure the Status byte within the BIT message To configure the word select the BIT Configuration tab from the Unit Configuration menu The dialog box allows selection of which status types to enable hardware software sensor and comm Like the IMU VG and AHRS440 Crossbow recommends for the vast majority of users that the default Status byte for the NAV440 is sufficient For users who wish to have additional visibility or alerts relative to the GPS sensor status or algorithm status they can configure additional triggers
31. n Ovetvlew 4 d eh i ede usa eh n eee edens 14 3 12 2 Mag Alignment Procedure Using NAV VIEW 2 X 15 3 13 Read Unit Configuration URP eee ee e iR ERR 16 Theory of Operation reto ee iue tte Dre ente eee SS b eec elu tate rte c e en i P D eie 17 4 1 440 Series Default Coordinate System 20 4 1 1 Advanced Settings astieg oie cd aoe ee eam d aree Alec ai ir Pe ele E 21 4 2 IMU440 Theory of Operation oerte e er e e Re Oben Dan 21 4 2 1 IMU440 Ady anced Settin eee aec t td P re i eI Hie ee tec ner e e 21 4 2 2 IMU440 Built In Test o tbe te reti dese petite 22 4 3 VG440 Theory OP OperatiON diete det e edd dei e edet p e fefe n t pci t ene 23 Doc 7430 0131 01 Rev E Page i Crossb w 440 Series User s Manual 4 3 1 VG440 Adyanced Settings is E 24 4 3 2 VG440 Built In Test enne eo e ee eot p RE ite qr e dt PR t a CR 25 44 AHRS440 Theory of Operation u repente aS te Ege DE PH HE axes le ERE e Dao De eee de e eee ce Ped 26 4 4 1 AHRS440 Magnetometer Calibration and Alignment Theory of Operation sese 27 4 4 2 AHRS40 Advanced Settings oen bee nde eet oim a dada cb Die 28 4 4 3 AHRS440 Built Inn 1 ong er to D ERIT e ERR ee RR O ETES 29 4 5 NAV440 Theory of Operation u
32. n arare pO e REO A ERO noted 30 4 5 1 NAV440 Magnetometer Calibration and Alignment esee eene nennen 31 4 5 2 NAV440 Advanced Settings tete tert rete EU REND 31 4 5 3 NAV440 Built In Test iiem Str uqaqa D ER RP ERR aa a aq naa 33 5 Application Guides ame abeo need Ee eo IU dieto D t e eben dee eee its 34 5 1 Introduction PERDU See Shc Sa eda STE m DI HO UE 34 5 2 Fixed Wing u anu s u alpa eda pe teen Aid Peor e aided ai tec n ek 34 5 3 Rotorcraft ii unpu aaa Sa EH ROREM ien 34 5 4 Land Vehicles au usss hassan EU 35 9992 Water Vehicle 5 n poni eee tue OA n E ERE e ER e on D PEOR enin 36 6 Programming Guide nee pee RE RB d ORO REI UR e n RH Ree pide 38 6 1 General MEE 38 6 2 Number eet eet te e f i p tcd uay c tede eee e ut dc tees tds 38 6 3 Packet Format aasan alana siasa e e ERR d o e UE eie a i rec Qe eee 38 6 3 1 Packet Header P evs 39 6 3 2 Packet Types hs a asnu a ais fee aah th Rie nip UR aei nine 39 6 3 3 Paylodd en nea ee a eS Pe 39 6 3 4 P yload soupe Gath MG See eR tede 39 6 3 5 16 bit CRC CGLLEL ushay e n pic b o ODORE E 39 6 3 6 Messaging OVeEVIEW sieben Ee e OD RR RT d He pde 39 T Communicating with the 440 Series a D se plc be eto does 42 7 1 Dink C
33. pi 2 16 Radians Yaw angle true north 360 727161 9 6 xRateCorrected 12 7 pi 2 16 rad s X angular rate corrected 1260 2 16 sec 8 yRateCorrected 12 7 pi 2 16 rad s Y angular rate corrected 1260 2 16 sec 10 zRateCorrected 12 7 pi 2 16 rad s Z angular rate corrected 1260 2 16 sec 12 nVel 12 512 2 16 m s North velocity 14 12 512 2 16 m s East velocity 16 dVel 12 512 2 16 m s Down velocity 18 longitudeGPS l4 2 pi 2 32 Radians GPS Longitude 360 7 232 9 22 lattudeGPS l4 2 pi 2 32 Radians GPS Latitude 360 2 32 9 26 alttudeGPS 2 2 14 2 16 m GPS altitude 100 16284 Doc 7430 0131 01 Rev E Page 51 440 Series User s Manual Crossb w 28 GPSITOW U2 truncated ms GPS ITOW lower 2 bytes 30 BlTstatus U2 Master BIT and Status 7 4 8 Nav Data Packet 1 Default NAV Nav Data N1 0x4E31 Packet Length Payload 0 5555 0 4 1 lt 1 payload gt CRC U2 gt This packet contains navigation data and selected sensor data scaled most cases to a signed 2716 275 complement number Data involving angular measurements include the factor pi in the scaling and can be interpreted in either radians or degrees Angles scaled to a range of pi pi or 180 deg to 180 deg Angular rates scaled to range of 3 5 pi pi or 630 deg sec to 630 deg sec Accelerometers scaled to a range of 10 10
34. pi in the scaling and can be interpreted in either radians or degrees Delta Angle scaled to range of 3 5 A radians or 630 630 A degrees Delta Velocity scaled to a range of 100 100 A m s S2 Payload Contents Byte Name Format Scaling Units Description Offset 0 xDeltaVel 4 200 2 32 mis X delta velocity 4 yDeltaVel 14 200 2 32 A m s Y delta velocity 8 zDeltaVel 14 200 2 32 A m s Z delta velocity 12 xDeltaAngle 14 7 pi 2 32 A rad X delta angle 1260 2 32 A 16 yDeltaAngle 14 7 pi 2 32 A rad Y delta angle 1260 2 32 A 20 zDeltaAngle 14 7 pi 2 32 A rad Z delta angle 1260 2 32 A 24 Counter U2 packets Output packet counter 26 BITstatus 02 Master and Status 7 4 4 Angle Data Packet 0 Angle Data A0 0x4130 Packet Length Payload 0x5555 0x4130 A0 payload CRC U2 gt This packet contains angle data and selected sensor data scaled in most cases to a signed 2 16 2 s complement number Data involving angular measurements include the factor pi in the scaling and can be interpreted in either radians or degrees Angles scaled to a range of pi pi or 180 deg to 180 deg Angular rates scaled to range of 3 5 pi pi or 630 deg sec to 630 deg sec Accelerometers scaled to a range of 10 10 g Magnetometers scaled to a range of 1 1 Gauss Temperature scaled to a range of 100 100
35. poor data transfer Figure 4 Packet Statistics Packet Statistics Packets Received 146442 CRC Failures Avg Packet Rate Hz 102 30 Elapsed Time 00 24 23 Reset Done Doc 7430 0131 01 Rev E Page 11 440 Series User s Manual Crossb w 39 Unit Configuration The Unit Configuration window gives the user the ability to view and alter the system settings This window is accessed through the Unit Configuration menu item under the configuration menu Under the General tab users have the ability to verify the current configuration by selecting the Get All Values button This button simply provides users with the currently set configuration of the unit and displays the values in the left column of boxes There are three tabs within the Unit Configuration menu General Advanced and BIT Configuration The General tab displays some of the most commonly used settings The Advanced and BIT Configuration menus provide users with more detailed setting information that they can tailor to meet their specific needs To alter a setting simply select the check box on the left of the value that you wish to modify and then select the value using the drop down menu on the right side Once you have selected the appropriate value these settings can be set temporarily or permanently a software reset or power cycle is required for the changes to take affect by selecting from the choices at the bottom of the dialog box
36. sent with the unit is intended to provide the user with the ability to test the unit right out of the box and will not provide adequate shielding for all environments Case ground see below must be used to provide full EMI protection In addition users should take care to ground the cable shield on only one end of the cable WARNING The 440 Series is shipped with an EMI filter attached to the DB 15 connector This connector must remain in place to ensure proper shielding from EMI interference WARNING The cable sent with the unit is intended to provide the user with the ability to test the unit right out of the box and will not provide adequate shielding for all environments WARNING Case ground see below must be used to provide full EMI protection In addition users should take care to ground the cable shield on only one end of the cable 2 3 Power Input and Power Input Ground Power is applied to the 440 Series on pins 3 and 4 Pin 4 is ground Pin 3 should have 9 to 42 VDC unregulated at 350 mA If you are using the cable supplied with the 440 Series the power supply wires are broken out of the cable at the DB 9 connector The red wire is connected to the positive power input the black wire is connected to the power supply ground Doc 7430 0131 01 Rev E Page 4 440 Series User s Manual Crossb w WARNING Do not reverse the power leads or damage may occur 2 4 Case Ground The case is electrically conn
37. short duration lt 1 sec and a modest percentage over the maximum operating range it is recommended that the restart on over range setting be turned off Handling of an inertial rate sensor over range is controlled using the restartOnOverRange switch If this switch is off the system will flag the overRange status flag and continue to operate through it If this switch is on the system will flag a masterFail error during an over range condition and continue to operate with this flag until a quasi static condition is met to allow for an algorithm restart The quasi static condition required is that the absolute value of each low passed rate sensor fall below 3 deg sec to begin initialization The system will then attempt a normal algorithm start Crossb w Doc 7430 0131 01 Rev E Page 32 440 Series User s Manual Crossb w Dynamic ON The default setting is ON for the 440 Turning off the dynamic motion Motion setting results in a higher gain state that uses the accelerometer feedback heavily During periods of time when there is known low dynamic acceleration this switch can be turned off to allow the attitude estimate to quickly stabilize Turn 0 5 With respect to centripetal or false gravity forces from turning dynamics or Switch deg sec coordinated turn the NA V440 monitors the yaw rate If the yaw rate exceeds a threshold given Turnswitch threshold the feedback gains from the accelerometer s
38. successfully NAK Payload Contents Byte Name Format Scaling Units Description Offset 0 failedlnputPacketType U2 the failed request 7 3 Output Packets Polled The following packet formats are special informational packets which can be requested using the command 7 3 1 Identification Data Packet Identification Data 4 0x4944 Packet Length Payload 0 5555 0 4944 lt 10 payload gt CRC U2 gt This packet contains unit seriaINumber modelString model string is terminated with 0 00 model string contains the programmed versionString 8 bit Ascii values followed by the firmware part number string delimited by a whitespace ID Payload Contents Byte Name Format Scaling Units Description Offset 0 serialNumber U4 Unit serial number 4 modelString SN 2 gt Unit Version String 4 N 0x00 U1 Zero Delimiter 7 3 2 Version Data Packet Version Data VR 0x5652 Packet Length Payload 0x5555 0 5652 lt VR payload gt lt CRC U2 gt This packet contains firmware version information majorVersion changes may introduce serious incompatibilities minorVersion changes may add or modify functionality but maintain backward compatibility with previous minor versions patch level changes reflect bug fixes and internal modifications with little effect on the user
39. the softwareStatus and masterStatus flags to be asserted in the BITstatus field 9 16 4 sensorStatusEnable Field This field is a bit mask of the sensorStatus field see BIT and status definitions This field allows the user to determine which low level sensorStatus field signals will flag the sensorStatus and masterStatus flags in the BITstatus field Any asserted bits in this field imply that the corresponding sensorStatus field signal if asserted will cause the sensorStatus and masterStatus flags to be asserted in the BITstatus field Doc 7430 0131 01 Rev E Page 66 440 Series User s Manual Crossb w 10 Appendix A Mechanical Specifications 10 1 440 Series Outline Drawing IMU VG 10 2 Doc 7430 0131 01 Rev E Page 67 440 Series User s Manual Crossbgw 440 Series Outline Drawing AHRS NAV 0010 0948 0000 Doc 7430 0131 01 Rev E Page 68 440 Series User s Manual message packet formats are explained in this section Crossb w 11 Appendix B NMEA Message Format The GPS receiver outputs data in NMEA 0183 format at 9600 Baud 8 bits no parity bit and 1 stop bit The GGA and RMC 11 1 GGA GPS fix data Time and position together with GPS fixing related data number of satellites in use and the resulting HDOP age of differential data if in use etc SGPGGA hhmmss ss Latitude N Longitude l E FS NoSV HDOP msl m Altref m DiffAge DiffStatio
40. the unit will respond with an error response Note that both a set fields and an error response may be received as a result of one set fields command Attempts to set a field with an invalid value is one way to generate an error response A table of field IDs and valid field values is available in Section 8 1 SF Payload Contents Byte Offset Name Format Scaling Units Description 0 numFields U1 The number of fields to set 1 fieldO U2 The first field ID to set 3 fieldOData U2 The first field ID s data to set 5 field1 U2 The second field ID to set 7 field1 Data U2 The second field ID s data to set m A U2 let numFields 4 3 field U2 The last field ID to set numFields 4 1 field Data U2 The last field ID s data to set Write Fields Response Write Fields WF 0x5746 Packet Length Payload 0x5555 0x5746 1 numFields 2 WF payload CRC 02 gt The unit will send this packet in response to a write fields command if the command has completed without errors Doc 7430 0131 01 Rev E Page 58 440 Series User s Manual Crossb w WF Payload Contents Byte Offset Name Format Scaling Units Description 0 numFields U1 The number of fields written 1 fieldO U2 The first field ID written 3 field1 U2 The second field ID written ds 23 U2 More field IDs w
41. to power and black to ground The input voltage can range from 9 42 VDC with a maximum current draw of 350 mA 4 Allow at least 60 seconds after power up for the 440 Series product to initialize The 440 Series needs to be held motionless during this period WARNING Do not reverse the power leads Reversing the power leads to the 440 Series can damage the unit although there is reverse power protection Crossbow Technology is not responsible for resulting damage to the unit should the reverse voltage protection electronics fail 3 3 Setting up NAV VIEW 2 X With the 440 Series product powered up and connected to your PC serial port open the NAV VIEW 2 X software application 1 NAV VIEW 2 X should automatically detect the 440 Series product and display the serial number and firmware version if itis connected Doc 7430 0131 01 Rev E Page 8 440 Series User s Manual Crossb w 2 If NAV VIEW 2 X does not connect check that you have the correct COM port selected You will find this under the Setup menu Select the appropriate COM port and allow the unit to automatically match the baud rate by leaving the Auto match baud rate selection marked 3 If the status indicator at the bottom is green and states Unit Connected you re ready to go If the status indicator doesn t say connected and is red check the connections between the 440 Series product and the computer check the power supply and verify that the COM por
42. will flag the overRange status flag and continue to operate through it If this switch is on the system will flag a masterFail error during an over range condition and continue to operate with this flag until a quasi static condition is met to allow for an algorithm restart The quasi static condition required is that the absolute value of each low passed rate sensor fall below 3 deg sec to begin initialization The system will then attempt a normal algorithm start Dynamic ON The default setting is ON for the VG440 Turning off the dynamic motion setting Motion results in a higher gain state that uses the accelerometer feedback heavily During periods of time when there is known low dynamic acceleration this switch can be turned off to allow the attitude estimate to quickly stabilize Turn 10 0 With respect to centripetal or false gravity forces from turning dynamics or Switch deg sec coordinated turn the VG440 monitors the yaw rate If the yaw rate exceeds a threshold given Turnswitch threshold the feedback gains from the accelerometer signals for attitude correction are reduced because they are likely corrupted BIT See 4 3 2 4 3 2 VG440 Built In Test As with the IMU440 the VG440 Built In Test capability allows users of the VG440 to monitor health diagnostic and system status information of the unit in real time The Built In Test information consists of a BIT word 2 bytes transmitted in every measurem
43. 0 The 1PPS output signal is provided by the internal GPS receiver when GPS timing is known on NA V440 products On IMU VG and AHRS 440 products this signal is simply a buffered version of the 1PPS input signal provided by the user The 5 output signal is open collector and should be interfaced to a rising edge trigger with pull up resistor between 1k and 10k ohms The 440 Series products synchronize sensor data collection to this 1PPS signal internally when available Therefore the 100Hz navigation algorithm will run exactly 100 times each second with no slip when locked to 1PPS Packet data is valid on the rising edge of 1PPS and 10ms boundaries thereafter There is however up to 500us of additional latency in sensor data collection If 1 PPS is provided by the internal GPS receiver NAV products then the rising edge of 5 will correspond to the UTC second boundary When the system is synchronized to IPPS the hardwareStatus gt unlocked1PPS flag will be zero otherwise it will be one Figure 1 shows the sequential order of the signal present at 1 PPS OUT pin The 1 PPS signal is aligned to the sampling clock of 23 104 MHz This results in a timing resolution of 43 ns Figure 1 1PPS Output Signal GPS 8 30 00 GPS 8 30 01 2 11 GPS Antenna Connection TIMEPULSE 440 GPS receiver needs to receive signals from as many satellites as possible GPS i receiver doesn t work properly narrow streets and u
44. 0 to a specific application requirements The AHRS440 advanced settings are shown in Table 11 below Table 11 AHRS440 Series Advanced Settings Setting Default Comments Baud Rate 38 400 9600 19200 57600 also available baud Packet AI 50 51 S2 0 A2 NO also available Type Packet 25 Hz This setting sets the rate at which selected Packet Type packets are output If Rate polled mode is desired then select Quiet If Quiet is selected the VG440 will only send measurement packets in response to GP commands Orientation See To configure the axis orientation select the desired measurement for each axes Fig 12 NAV VIEW 2 X will show the corresponding image of the 5440 so it easy to visualize the mode of operation See section 8 4 Orientation Field settings for the twenty four possible orientation settings The default setting points the connector AFT Analog 5Hz The low pass filters are set to a default of 5Hz for the accelerometers and 20Hz Filter accels for the angular rate sensors There is one filter setting for all three angular rate Clocks 1 2 99 Hz sensors There are two settings for the accelerometers one for the X and Y axes amp 3 rates and a separate setting for the Z axis The reason for a separate setting in the Z axis is that in many installations the Z axis vibration level is much higher than in the X and Y axes and it can prove helpful to filter the Z axis at a lower cutoff than t
45. 000000000000000000 ffd8ffbaD000200000000ffffffZZff5cOlaeO0000000000000000000000000000 ffd8ffbbO000200000000fffeffZZff5cOlae0000000000000000000000000000 ffd8ffbbO00100000000fffeffZZff5cOlae0000000000000000000000000000 ffd8ffbbO00100000000fffeffZZff5cOlaeO0000000000000000000000000000 ffd8ffba000100000000ffffffZZff5cOlae0000000000000000000000000000 ffd7ffba000100000000fffeffZZff5cOlaeO0000000000000000000000000000 ffd7ffbaD000100000000ffffffZZff5cOlaeO0000000000000000000000000000 Doc 7430 0131 01 Rev E Page 10 440 Series User s Manual Crossb w 3 7 Horizon and Compass View If the 440 Series product you have connected is capable of providing heading and angle information see Table 2 NAV VIEW 2 X can provide a compass and a simulated artificial horizon view To activate these views simply select Horizon View and or Compass View from the View drop down menu at the top of the page Figure 3 Horizon and Compass View 3 8 Packet Statistics View Packet statistics can be obtained from the View menu by selecting the Packet Statistics option This view simply provides the user with a short list of vital statistics including Packet Rate CRC Failures and overall Elapsed Time that are calculated over a one second window This tool should be used to gather information regarding the overall health of the user configuration Incorrectly configured communication settings can result in a large number of CRC Failures and
46. 40 Series Inertial Systems This code can be used by a user application reading data directly from the 440 Series product or perhaps from a log file The sample code contains the actual parser but also several support functions for CRC calculation and circular queue access e process xbow packet for parsing out packets from a queue Returns these fields in structure XBOW PACKET see below Checks for CRC errors calcCRC for calculating CRC on packets e Initialize initialize the queue e AddQueue add item in front of queue e DeleteQueue return an item from the queue e peekWord for retrieving 2 bytes from the queue without popping e peekByte for retrieving a byte from the queue without popping e Pop discard item s from queue e Size returns number of items in queue e Empty return 1 if queue is empty 0 if not e Full return 1 if full 0 if not full The parser will parse the queue looking for packets Once a packet is found and the CRC checks out the packet s fields are placed in the XBOW PACKET structure The parser will then return to the caller When no packets are found the parser will simply return to the caller with return value 0 The XBOW PACKET stucture is defined as follows typedef struct xbow packet unsigned short packet_type char length unsigned short crc char data 256 XBOW PACKET Typically the parser would be called within a loop in a separate process or in some time tri
47. 41900288a3e0300 a3ad CRC lensth invalid 001bffdf3a5b fffe0000ffea fff8fff7f337 0015 9 4 00000000000000000000 2419 00288a3e 0300 Hex Value Data g FFF8 0 0024 FFF7 0 0027 F337 0 9988 Hex Value Data m s 0015 0 164 FDA9 4 680 FD4F 5 383 Hex Value Data deg 001b 0 148 FFFD 0 181 3A5B 82 062 Hex Value Data deg s GPS 00000000 0 000000000 Rad 00000000 0 000000000 Rad Hex Value Data deg C 2D19 35 233 timeITOW Value Hex Data lt 00288a3e 2656830 BIT status Field mesra n n sss re lt erved Doc 7430 0131 01 Rev E Page 78 440 Series User s Manual Crossb w 14 Warranty and Support Information 14 1 Customer Service As a Crossbow Technology customer you have access to product support services which include e Single point return service e Web based support service e Same day troubleshooting assistance e Worldwide Crossbow representation e Onsite and factory training available e Preventative maintenance and repair programs e Installation assistance available 14 2 Contact Directory United States Phone 1 408 965 3300 8 AM to 5 PM PST Fax 1 408 324 4840 24 hours Email techsupport xbow com Non U S Refer to website www xbow com 14 3 Return Procedure 14 3 1 Authorization Before returnin
48. 440 and AHRS440 B Port Input The VG440 AHRS440 allows the use of an external GPS receiver to be connected with its GPS port The user is required to configure the GPS receiver to output the GPS messages that the 440 Series expects The table below shows the supported GPS protocols and guidelines for configuration Note that the details of the GPS messages can be found in the respective GPS protocol documents The user must configure the VG AHRS440 to accept external GPS information using NAV VIEW 2 X as described in Chapter 3 If the VG AHRS440 is parsing valid external GPS data and the GPS receiver has 3D lock then the comStatus noExternalGPS flag will be zero otherwise it will be one See section 9 for a complete description of system status indications Since NMEA protocol does not provide vertical velocity the vertical velocity that the 440 Series estimates based upon GPS altitude changes may not be sufficient for airborne applications Therefore the NMEA protocol is not recommended for airborne applications Configuration of An External GPS Receiver for VG440 AHRS440 Protocols Required Messages Required Message Rate Ublox binary NAV LLH NAV 4Hz 9600 19200 38400 VELNED NAV 57600 STATUS NovAtel OEM4 PosVelNavDopA 19200 38400 57600 ASCII NMEA GPGGA GPVTG 4 9600 19200 38400 57600 Not recommended for airborne applications NovAtel OEM4 BestPosB BestVelB 9600 19200 38400 and OEMV 57600 Binary 4Hz
49. Accel 12 20 2 16 0 Z accelerometer 18 xRateTemp 12 200 2 16 deg C X rate temperature 20 yRateTemp 12 200 2 16 deg C Y rate temperature 22 zRateTemp 12 200 2 16 deg Z rate temperature 24 timelTOW U4 1 ms DMU ITOW sync to GPS 28 BlTstatus U2 Master BIT Status 7 4 7 Data Packet 0 Nav Data NO 0x4E30 Packet 0 5555 Ox4E30 lt N0 payload gt CRC U2 gt This packet contains navigation data and selected sensor data scaled in most cases to a signed 2716 275 complement number Data involving angular measurements include the factor pi in the scaling and can be interpreted in either radians or degrees Angles scaled to a range of pi pi or 180 deg to 180 deg Angular rates scaled to range of 3 5 pi pi or 630 deg sec to 630 deg sec Accelerometers scaled to a range of 10 10 g Magnetometers scaled to a range of 1 1 Gauss Temperature scaled to a range of 100 100 C Velocities are scaled to a range of 256 256 m s Altitude is scaled to a range of 100 16284 m using a shifted 2 s complement representation Longitude and latitude are scaled to a range of pi pi or 180 deg to 180 deg NO Payload Contents Byte Name Format Scaling Units Description Offset 0 rollAngle 12 2 pi 2 16 Radians Roll angle 360 727161 3 2 pitchAngle 12 2 pi 2 16 Radians Pitch angle 360 727161 9 4 yawAngleTrue 2 2
50. NT The following section only applies to 440 Series products with magnetometers AHRS and NA V440 If your particular model does not utilize magnetometers for heading or performance you can disregard Section 3 12 3 12 1 Hard lron Soft Iron Overview The AHRS and NAV440 products use magnetic sensors to compute heading Ideally the magnetic sensors would be measuring only earth s magnetic field to compute the heading angle In the real world however residual magnetism in your system adds to the total magnetic field measured This residual magnetism called hard iron and soft iron will create errors in the heading measurement if it is not accounted for In addition magnetic material can change the direction of the magnetic field as a function of the input magnetic field This dependence of the local magnetic field on input direction is called the soft iron effect The AHRS and NA V440 products can actually measure the constant magnetic field that is associated with your system and correct for it The AHRS and NA V440 products can also make a correction for some soft iron effects The process of measuring these non ideal effects and correcting for them is called the Mag Alignment Procedure Performing a Mag Alignment Procedure will help correct for magnetic fields that are fixed with respect to the 440 Series product It cannot correct for time varying fields or fields created by ferrous material that moves with respect to the 440 Series produc
51. Packets Polled or 01 nenne 46 Page ii Doc 7430 0131 01 Rev E 440 Series User s Manual Crossb w 7 4 1 Scaled Sensor Data Packet mao EE RPG pU S REEL 46 7 4 2 Scaled Sensor Data Packet 1 Default IMU Data n usss 47 7 4 3 Scaled Sensor Data Packet 2 Delta Theta Delta V enne 48 7 4 4 Anele Data Packet 0 4 nitate etate tiae emen 48 7 4 5 Angle Data Packet 1 Default AHRS Data eene enne nnne nennen trennen reinen nnns 49 7 4 6 Angle Da ta P cket2 Default VG a 50 TAT Nav Data Packet 05 4 5 51 7 4 8 Nav Data Packet 1 Default 2 2 171 2 12 4 anananaymi iaia anay sienne 52 7 4 9 Angle Data Packet Custom VG AEREE e R 53 7 4 10 Angle Data Packet B2 Custom VG 53 8 JAdvanced Commi nds u u u un etate de dide D aite aie ides ecd ed 54 8 1 Configuration Fields o SIR RE e etes D ee qr PEE Er RE de PEE ERN dns 54 82 Continuous Packet Type Field eene ie tec Ue t Pee eie Ee erede ed eer
52. Reserved 4 7 masterStatus 8 0 nominal 1 Alert Sensor Over Range Status hardwareStatus 9 Disabled Status comStatus 10 Disabled Status softwareS tatus 11 Disabled Status sensorStatus 12 0 nominal 1 Sensor Over Range Status Reserved 13 15 N A The IMU440 also allows a user to configure the Status byte within the BIT message To configure the word select the BIT Configuration tab from the Unit Configuration menu The dialog box allows selection of which status types to enable hardware software sensor and comm In the case of the IMU440 which has fewer features and options than other 440 Series products the only meaningful parameter is sensor over range It is recommended that users leave the default configuration which is sensorStatus enabled and flag on sensor over range The over range only applies to the rotational rate sensors Because instantaneous acceleration levels due to vibration can exceed the accelerometer sensor range in many applications none of the 440 Series products trigger over range on accelerometer readings 43 VG440 Theory of Operation The VG440 supports all of the features and operating modes of the IMU440 and it includes additional internal software running on the DSP processor for the computation of dynamic roll and pitch The product name VG440 stands for Vertical Gyro 440 and it is indicative of the vertical gyro functionality that the VG440 replicates by providing dynamic roll and pit
53. Soft Iron Ratio 0 00290 0 00128 0 99997 Perform Mew Alignment Rol 0 1 Magnetometer Output Cancel Instructions Blowhy rotate the unit on a level surface about the Z axis until NAV VIEW reports that the calibration is done Y Field Gauss The operation will timeout in 120 seconds 0 0 X Field Gauss Rotate the AHRS or NA V440 product through 380 degrees of rotation or until you receive a message to stop 5 Once you have completed your rotation you will be given data concerning the calibration accuracy The X and Y offset values indicate how far the magnetic field has been offset due to hard iron affects from components surrounding the unit In addition you will see a soft iron ratio indicating the effect of soft iron on the AHRS of NAV440 product 6 Save this data to the AHRS or NAV440 product by selecting the Apply button Doc 7430 0131 01 Rev E Page 15 440 Series User s Manual Magnetometer Alignment Mew Settings Hard Iron Offset 0 03580 Y Hard Offset Soft lron Ratio 0 99997 m Crossb w 7 Upon completion of the Mag Alignment Procedure the heading accuracy should be verified with all third party systems active using a known reference such as a compass rose GPS track or a calibrated compass Heading inaccuracies greater than the values specified on the data sheet or fluctuating heading performance may be an indication of magnetic
54. The build stage is one of the following 0 release candidate 12development 2 alpha 3 beta The buildNumber is incremented with each engineering firmware build The buildNumber and stage for released firmware are both zero The final beta candidate is v w x 3 y which is then changed to v w x 0 1 to create the first release candidate The last release candidate is v w x 0 z which is then changed to v w x 0 0 for release VR Payload Contents Byte Name Format Scaling Units Description Offset 0 majorVersion U1 Major firmware version 1 minorVersion U1 E gt Minor firmware version Doc 7430 0131 01 Rev E Page 45 440 Series User s Manual Crossb w 2 patch U1 Patch level 3 stage Development Stage O release candidate 1 development 2 alpha 3 beta 4 buildNumber U1 Build number 7 3 3 Test 0 Detailed BIT and Status Packet Test T0 0x5430 Packet Type Payload 03 3x5555 0x5430 TO payload CRC U2 gt This packet contains detailed BIT and status information The full BIT Status details are described in Section 9 of this manual TO Payload Contents Byte Name Format Scaling Units Description Offset 0 BlTstatus U2 Master BIT and Status Field 2 hardwareBIT U2 Hardware BIT Field 4 hardwarePowerBIT U2 Hardware Power BIT Field 6 hardwareE
55. U ITOW sync to GPS Doc 7430 0131 01 Rev E Page 52 440 Series User s Manual Crossb w 40 BlTstatus U2 Master BIT and Status 7 49 Angle Data Packet B1 Custom VG Data Angle Data B1 0x4231 Packet Type 0 5555 0x4231 B1 payload CRC U2 gt This packet contains selected angle and sensor data B1 Payload Contents Byte Name Format Scaling Units Description Offset 0 rollAngle 2 2 pi 2 16 Radians Roll angle 360 727161 9 2 pitchAngle 12 2 pi 2 16 Radians Pitch angle 36027161 9 4 yawAngleTrue 12 2 pi 2 16 Radians Yaw angle free 360 727161 9 6 zRateCorrected 2 7 pi 2 16 rad s Z angular rate corrected 1260 2 16 sec 8 xAccel 12 20 2 16 g X accelerometer 10 yAccel 12 20 2 16 0 Y accelerometer 12 timelTOW U4 1 ms DMU ITOW sync to GPS 16 BlTstatus U2 Master BIT and Status 7 4 10 Angle Data Packet B2 Custom VG Data Angle Data B2 0x4232 Packet Type 0 5555 0x4232 B2 payload CRC U2 gt This packet contains selected angle and sensor data B2 Payload Contents Byte Name Format Scaling Units Description Offset 0 rollAngle 2 2 pi 2 16 Radians Roll angle 360 927161 2 pitchAngle 2 2 pi 2 16 Radians Pitch angle 360 927161 4 zRateCorrected 2 7 pi 2 16 rad s Z angular rate corrected 1260 2 16 sec 6 xAcc
56. ailable packet types 83 Analog Filter Clocks 1 2 3 These three fields set hardware low pass filter cutoff frequencies Each sensor listed is defined in the default factory orientation Users must consider any additional rotation to their intended orientation Filter Clock Sensor analogFilterClock1 Ux Uz Accel analogFilterClock2 Uy Accel analogFilterClock3 Ux Uy Uz rate Doc 7430 0131 01 Rev E Page 54 440 Series User s Manual 8 4 Orientation Field Crossb w This field defines the rotation from the factory to user axis sets This rotation is relative to the default factory orientation connector aft baseplate down The default factory axis set is Ux Uy Uz defined by the connector pointing in the Ux direction and the baseplate pointing in the Uz direction The user axis set is X Y Z as defined by this field A depiction of the factory axis set is shown below U UX Uy Description Bits Meaning X Axis Sign 0 0 positive 1 negative X Axis 1 2 0 Ux 1 2 Uz 3 Y Axis Sign 3 0 positive 1 negative Y Axis 4 5 0 1 Uz 2 3 Z Axis Sign 6 0 positive 1 negative Z Axis 7 8 0 Uz 1 2 3 Reserved 9 15 There are 24 possible orientation configurations Setting Writing the field to anything else generates and has no effect
57. al sensor cluster For the AHRS product a 3 axis magnetometer is used for correcting the drift on yaw heading angle For the NAV product a 3 axis magnetometer and a GPS receiver are used for correcting the drift on yaw heading angle increasing the accuracy of the attitude estimation by incorporating these sensor signals into the EKF and providing a navigation solution The common aiding sensor for the drift correction for the attitude i e roll and pitch only is a 3 axis accelerometer This is the default configuration for the VG product Doc 7430 0131 01 Rev E Page 19 440 Series User s Manual Crossb w Figure 11 Functional Block Diagram of NAV AHRS and VG Default Operating Mode accels rates mags attitude velocity GPS position accels rates mags attitude cA NAV Mode NA V440 or AHRS440 with External GPS b AHRS Mode AHRS440 or NAV440 with loss of GPS accels rates attitude velocity GPS position accels rates attitude heading yaw free drifting c VGS Mode VG440 with External GPS d VG Mode VG440 4 1 440 Series Default Coordinate System The 440 Series Inertial System default coordinate system is shown in Figure 12 As with many elements of the 440 Series the coordinate system is configurable with either NAV VIEW 2 X or by sending the appropriate serial commands These configurable elements are known as Advanced Settings This section of the manual describes the defa
58. an be interpreted in either radians or degrees Angles scaled to a range of pi pi or 180 deg to 180 deg Angular rates scaled to range of 3 5 pi pi or 630 deg sec to 630 deg sec Accelerometers scaled to a range of 10 10 g Magnetometers scaled to a range of 1 1 Gauss Temperature scaled to a range of 100 100 C A1 Payload Contents Byte Name Format Scaling Units Description Offse t 0 rollAngle 12 2 pi 2 16 Radians Roll angle 360 7 2 16 4 2 pitchAngle 2 2 pi 2 16 Radians Pitch angle 3602716 3 Doc 7430 0131 01 Rev 49 440 Series User s Manual 4 yawAngleMag 2 2 pi 2 16 Radians Yaw angle magnetic north 360 72 16 9 6 xRateCorrected 12 7 pi 2 16 rad s X angular rate Corrected 126072 16 8 yRateCorrected 12 7 pi 2 16 rad s Y angular rate Corrected 126072 16 10 zRateCorrected 12 7 pi 2 16 rad s Z angular rate Corrected 126072 16 sec 12 xAccel 12 20 2 16 g X accelerometer 14 yAccel 12 20 2 16 g Y accelerometer 16 zAccel 12 20 2 16 0 Z accelerometer 18 xMag 12 2 2 16 Gauss X magnetometer 20 yMag 12 2 2 16 Gauss Y magnetometer 22 zMag 12 2 2 16 Gauss Z magnetometer 24 xRateTemp 12 200 2 16 Deg X rate temperature 26 timelTOW U4 1 ms DMU ITOW sync to GPS 30 BlTstatus U2 Master BIT and Status 7 46 Angle Data Packet 2 D
59. anced Settings for Water Vehicle ise ped NAV440 Recommended Application Settings Surfaced Submerged UseMags ONS ONS UseGPS ON OFF FreeIntegrate OFF OFF Stationary Yaw Lock OFF OFF Restart Over Range OFF OFF Dynamic Motion ON ON Turn Switch Threshold 10 deg s 5 deg s XY Filter Accel 5 Hz 2 Hz Z Filter Accel 5 Hz 2 Hz Filter Rate Sensor 15 Hz 10 Hz When not in distorted magnetic environment EXAMPLE Figure 13 shows a typical flight profile of the fixed wing aircraft and the corresponding advanced settings that one can configure adaptively depending on a flight phase e Prelaunch is the phase of flight in which an aircraft goes through a series of checkups hardware and software on the ground before takeoff The aircraft is a static condition e Takeoff is the phase of flight in which an aircraft goes through a transition from moving along the ground taxiing to flying in the air usually along a runway The aircraft is under horizontal acceleration and may suffer from vibrations coming from an engine and ground contact forces transmitted from its landing gear e Climb is the phase of a flight after take off consisting of getting the aircraft to the desired flight level altitude More generally the term climb means increasing the altitude The aircraft is under vertical acceleration until it reaches the steady state climb rate e Straight and level flight is the phase of fl
60. areStatusEnable Bit mask of enabled software status 0x0012 Any signals sensorStatusEnable 0x0013 Any Bit mask of enabled sensor status signals 9 16 1 hardwareStatusEnable Field This field is a bit mask of the hardwareStatus field see BIT and status definitions This field allows the user to determine which low level hardwareStatus field signals will flag the hardwareStatus and masterStatus flags in the BITstatus field Any asserted bits in this field imply that the corresponding hardwareStatus field signal if asserted will cause the hardwareStatus and masterStatus flags to be asserted in the BITstatus field 9 16 2 comStatusEnable Field This field is a bit mask of the comStatus field see BIT and status definitions This field allows the user to determine which low level comStatus field signals will flag the comStatus and masterStatus flags in the BITstatus field Any asserted bits in this field imply that the corresponding comStatus field signal if asserted will cause the comStatus and masterStatus flags to be asserted in the BITstatus field 9 16 3 softwareStatusEnable Field This field is a bit mask of the softwareStatus field see BIT and status definitions This field allows the user to determine which low level softwareStatus field signals will flag the softwareStatus and masterStatus flags in the BITstatus field Any asserted bits in this field imply that the corresponding softwareStatus field signal if asserted will cause
61. around the z axis The x and y axis rate sensors would measure zero angular rates and the z axis sensor would measure a positive angular rate The magnetic sensors are aligned with the same axes definitions and sign as the linear accelerometers For example when oriented towards magnetic North you will read approximately 0 25 Gauss along X 0 0 Gauss along Y and 40 35 Gauss along Z direction North America Magnetic values at other geographic locations can be found at http www ngdc noaa gov seg WMM DoDWMM shtml Pitch is defined positive for a positive rotation around the y axis pitch up Roll is defined as positive for a positive rotation around the x axis roll right Yaw is defined as positive for a positive rotation around the z axis turn right The angles are defined as standard Euler angles using a 3 2 1 system To rotate from the body frame to an earth level frame roll first then pitch and then yaw The position output from GPS is represented in Latitude Longitude and Altitude LLA convention on the WGS84 Ellipsoid This is the most commonly used spherical coordinate system The GPS velocity is defined in North East and Down reference frame The users can convert this into Cartesian coordinate system called Earth Centered Earth Fixed ECEF ECEF uses three dimensional XYZ coordinates in meters to describe the location of a GPS user or satellite Several online resources are available to help users with this transforma
62. cating Advanced Commands and BIT Customers who wish to communicate with the 440 Series system for sensor and navigation data should review Section 6 and 7 Section 8 is for users who wish to configure the 440 Series operating parameters e g baud rate or power up output rate without NAV VIEW 2 X Doc 7430 0131 01 Rev E Page 1 440 Series User s Manual Crossb w 1 2 Overview of the 440 Series Inertial Systems This manual provides a comprehensive introduction to the use of Crossbow s 440 Series Inertial System products listed in Table 2 This manual is intended to be used as a detailed technical reference and operating guide for the 440 Series Crossbow s 440 Series products combine the latest in high performance commercial MEMS Micro electromechanical Systems sensors and digital signal processing techniques to provide a small cost effective alternative to existing IMU systems and mechanical gyros Table 2 440 Series Feature Description Product Features IMU440 6 DOF Digital IMU VG440 6 DOF IMU plus Dynamic Roll Pitch AHRS440 6 DOF IMU with 3 Axis Internal Magnetometer Dynamic Roll Pitch and Heading NAV440 6 DOF IMU with 3 Axis Internal Magnetometer and Internal WAAS Capable GPS Receiver Position Dynamic Velocity and Dynamic Roll Pitch Heading The 440 Series is Crossbow s third generation of MEMS based Inertial Systems building on over a decade of field experience and encom
63. ch measurements in addition to the IMU data The dynamic roll and pitch measurements are stabilized by the using the accelerometers as a long term gravity reference Unlike the VG400 and earlier Crossbow VG Series products the VG440 can also output a free integrating yaw angle measurement that is not stabilized by a magnetometer or compass heading see AHRS440 or NAV440 for stabilized heading At a fixed 100Hz rate the VG440 continuously maintains both the digital IMU data as well as the dynamic roll and pitch data As shown in the software block diagram Figure 10 after the Sensor Calibration block the IMU data is passed into an Integration to Orientation block Please refer to the Figure 11 if external GPS aiding will be used The Integration to Orientation block integrates body frame sensed angular rate to orientation at a fixed 100 times per second within all of the 440 Series products For improved accuracy and to avoid singularities when dealing with the cosine rotation matrix a quaternion formulation is used in the algorithm to provide attitude propagation As also shown in the software block diagram the Integration to Orientation block receives drift corrections from the Extended Kalman Filter or Drift Correction Module In general rate sensors and accelerometers suffer from bias drift misalignment errors acceleration errors g sensitivity nonlinearity square terms and scale factor errors The largest error in the orientation propagatio
64. cho CH 0x4348 Packet Length Payload 0 5555 0 4348 CRC U2 gt command allows testing verification of the communication link unit will respond with response containing the echo data data is N bytes long 7 1 4 Echo Response Echo Payload Contents Byte Name Format Scaling Units Description Offset 0 echoDataO U1 first byte of echo data 1 echoData1 U1 Second byte of echo data M s U1 Echo data N 2 echoData U1 Second to last byte of echo data N 1 echoData U1 Last byte of echo data 7 2 Interactive Commands Interactive commands are used to interactively request data from the 440 Series and to calibrate or reset the 440 Series 7 2 1 Get Packet Request Get Packet GP 0x4750 Packet Type Payload 0x5555 0x4750 lt GP payload gt lt CRC U2 gt This command allows the user to poll for both measurement packets and special purpose output packets including VR and ID Doc 7430 0131 01 Rev E Page 42 440 Series User s Manual Crossb w GP Payload Contents Byte Name Format Scaling Units Description Offset 0 requestedPacketType U2 The requested packet type Refer to the sections below for Packet Definitions sent in response to the GP command 72 2 Algorithm Reset Command A
65. cks the yaw movement and after 380 degrees of rotation returns the calibration complete response The auto termination sequence falsely terminate if the 360 degree rotation is not completed within 2 minutes of the WC command initiation Manual termination requires the user to send a second WC command with the termination code the payload Manual termination is a good option when the user system moves very slowly e g large marine vessel and completing the 360 degree rotation may require more than two minutes The calibration complete CC command response message contains the X and Y hard iron bias as well as the soft iron ratio This information can be interpreted to give an indication of the quality of the calibration See Section 3 12 for more information the hard iron bias and soft iron ratio Section 7 has programming details for the WC and CC commands WARNING The AHRS440 and NAV440 units must be mounted at least 24 away from large ferrous objects and fluctuating magnetic fields Failure to locate the unit in a clean magnetic environment will affect the attitude solution Docit 7430 0131 01 Rev E Page 27 440 Series User s Manual Crossb w 4 4 2 AHHS440 Advanced Settings In addition to the configurable baud rate packet rate axis orientation and sensor low pass filter settings the AHRS440 provides additional advanced settings which are selectable for tailoring the AHRS44
66. count gt MAXQUEUE retval 0 queue is full else queue_ptr gt count queue ptr rear queue ptr rear 1 MAXQUEUE queue ptr entry queue ptr rear item retval 1 return retval LE dd k k k k K k K K k K k K K K K k K K K k K K K K K K K K K K K K K K K K KOK K K K KOK K K K KOK K K K KOK KOK K K K KOK K K KO KOK k k E K k k R K K FUNCTION DeleteQeue return an item from the queue ARGUMENTS item will hold item popped from queue queue ptr is pointer to the queue RETURNS returns 0 if queue is empty 1 if successful Doc 7430 0131 01 Rev E Page 73 440 Series User s Manual eR A A AAA A A RRA int DeleteQueue char item QUEUE TYPE queue ptr int retval 0 if queue_ptr gt count lt 0 retval 0 queue is empty else queue ptr gt count item queue ptr entry queue ptr front queue ptr front queue ptr 5front 1 MAXQUEUE retval 1 return retval k K k k k k k k K K k K k k K K K k K K K K k K K K K k K k K K K K k K K K K K K K K K KOK K K K K K K K KOK K KOK k K K KOK KOK K K K k K KOK K k K k K k FUNCTION peekByte returns 1 byte from buffer without popping ARGUMENTS queue ptr is pointer to the queue to return byte from index is offset into buffer to which byte to return RETURNS 1 byte REMARKS does not do boundary checking please do this first
67. d iie eI RR UR E ERR Ee RENI eid 63 9 7 comsSerialABIT Field aah ST mae 63 9 8 comsSerialBBIT Field ei red e a u RD 64 9 9 softwareBLIBieldz a a sho 64 9 10 s ftwareAlsonthimbIT Field oap Laban Ur UD amaba db ep sate 64 9 softwareDat BIT Field e mee e un e ee irt e e n e e s 64 9 12 r h ardwareStatus Field u stre ere t MUR EE HQ RE AE ETE DS PRAE 65 9 13 comitatus Fields ee PRIOR ERE RON NIRE INDIES PR 65 9 14 sottwarestatus Piel s ehe eere t hes oem rd P te E e e E A vere e REI ERE 65 9 T5 sens rstatus Fleld ui REC REFERRE UP oda E GUN ERREUR asua 66 916 Configuring the miasterStatus oo eee ted dtele itte Leti too epe Reiter e Doe et 66 9 1161 hardwareStatusEnable Field ree 66 9 16 2 ucometatusEnableFiglde Za a au uM eene nennen un tease sees inset assa W ushu 66 9 16 3 softwareStatusEnable n U kasa u Dau nennen rnnt awaqa Ba aya bis 66 9 16 4 sensorStatusEnable 66 10 Appendix A Mechanical Specifications eoi eee rete ete Ea ene pen kusasta ee 67 Docs 7430 0131 01 Rev E Page iii Crossb w 440 Series User s Manual 10 1 440 Series Outline Drawing IMU VG nnne rn
68. d magnetometers to continuously estimate and correct for roll pitch and heading yaw errors as well as to estimate X Y and Z rate sensor bias The AHRS440 digital data is output over the RS 232 serial link at a selectable fixed rate 100 50 25 20 10 5 or 2 Hz or on as requested basis using the GP Get Packet command AHRS400 supports the same scaled sensor and angle mode packet format of the VG440 The AHRS440 defaults to the Al Angle Packet which outputs the roll angle pitch angle yaw angle and digital IMU data In the 5440 the 0 and 1 packets contain accurate magnetometer readings See Sections and 7 of the manual for full packet descriptions gt IMPORTANT For proper operation the AHRS440 relies on magnetic field readings from its internal 3 axis magnetometer AHRS440 must be installed correctly and calibrated for hard iron and soft iron effects to avoid any system performance degradation See section 4 4 1 for information and tips regarding installation and calibration 4 4 1 5440 Magnetometer Calibration and Alignment Theory of Operation The AHRS440 uses magnetic sensors to compute heading Ideally the magnetic sensors would measure only the earth s magnetic field to compute the heading angle In the real world however residual magnetism in your system will add to the magnetic field measured by the 5440 This extra magnetic field will create errors the heading
69. e Format Scaling Units Description 0 numFields U1 The number of fields to get 1 fieldO U2 The first field ID to get 3 field1 U2 The second field ID to get m us U2 More field IDs to get numFields 2 Field U2 The last field ID to get 1 8 12 Get Fields Response Get Fields GF 0x4746 Packet Length Payload 0x5555 0x4746 1 numFields 4 lt GF Data gt lt CRC U2 gt The unit will send this packet in response to a get fields request if the command has completed without errors GF Payload Contents Byte Offset Name Format Scaling Units Description 0 numFields U1 The number of fields retrieved 1 fieldO U2 The first field ID retrieved 3 fieldOData U2 The first field ID s data retrieved 5 field1 U2 The second field ID retrieved 7 field1 Data U2 The second field ID s data U2 numFields 4 3 field 02 last field ID retrieved numFields 4 1 field Data U2 The last field ID s data retrieved Doc 7430 0131 01 Rev E Page 60 440 Series User s Manual Crossb w 9 Advanced BIT 91 Built In Test BIT and Status Fields Internal health and status are monitored and communicated in both hardware and software The ultimate indication of a fatal problem is a hardware BIT signal on the user connector which is mirrored in the software BIT field as the maste
70. e accessible thru NAV VIEW 2 X under the Configuration Menu Unit Configuration settings Doc 7430 0131 01 Rev E Page 21 440 Series User s Manual Crossb w Table 7 IMU440 Advanced Settings Setting Default Comments Baud Rate 38 400 9600 19200 57600 also available baud Packet 51 52 also available Type Packet 100Hz This setting sets the rate at which selected Packet Type packets are output If Rate polled mode is desired then select Quiet If Quiet is selected the IMU440 will only send measurement packets in response to GP commands Orientation See Fig To configure the axis orientation select the desired measurement for each axis 12 NAV VIEW 2 X will show the corresponding image of the IMU440 so it easy to visualize the mode of operation Refer to Section 8 4 Orientation Field settings for the twenty four possible orientation settings The default setting points the connector AFT Analog 25 Hz The low pass filters are set to a default of 25 Hz for the accelerometers and 25 Hz Filter for the angular rate sensors There is one filter setting for all three angular rate Clocks 1 2 sensors There are two settings for the accelerometers one for the X and Y axes amp 3 and a separate setting for the Z axis The reason for a separate setting in the Z axis is that in many installations the Z axis vibration level is much higher than in the X and Y axes and it can prove helpful to filter the Z axis at a l
71. ected to Pin 5 of the DB 15 connector The Pin 5 should be electrically connected to the user s cable shield especially if the chassis does not make good ground contact The case should be bolted to a good conducting surface that is grounded 2 5 Serial Data Interface A Port The serial interface is standard RS 232 9600 19200 38400 or 57600 baud 8 data bits 1 start bit 1 stop bit no parity and no flow control and will output at a user configurable output rate These settings allow interaction via a standard PC serial port The serial data settings can be configured on a 440 Series unit with NAV VIEW 2 X In order to set the serial data interface select Unit Configuration under the Menu Tab 2 6 Serial GPS Interface NAV440 B Port Output The internal GPS receiver in NA V440 products outputs data in NMEA 0183 format as defined by the National Marine Electronics Association NMEA Standard For Interfacing Marine Electronic Devices Version 2 20 January 1 1997 The packets are sent at 9600 Baud 8 data bits 1 start bit 1 stop bit no parity bit and no flow control The GPS receiver outputs the following messages as shown in Table 4 Refer to Appendix B for the detailed message format Table 4 GPS Output Packet Format NMEA Record Description GGA Global positioning system fixed data RMC Recommended minimum specific GNSS data VTG Course over ground and ground speed data 2 7 External GPS Aiding VG
72. efault VG Data Angle Data A2 0x4132 Packet Type Payload 0 5555 0x4132 A2 payload CRC U2 gt This packet contains angle data and selected sensor data scaled in most cases to a signed 2 16 2 s complement number Data Crossb w involving angular measurements include the factor pi in the scaling and can be interpreted in either radians or degrees Angles scaled to a range of pi pi or 180 deg to 180 deg Angular rates scaled to range of 3 5 pi pi or 630 deg sec to 630 deg sec Accelerometers scaled to a range of 10 10 g Magnetometers scaled to a range of 1 1 Gauss Temperature scaled to a range of 100 100 C A2 Payload Contents Byte Name Format Scaling Units Description Offset 0 rollAngle 2 2 pi 2 16 Radians Roll angle 360 72 16 q 2 pitchAngle 2 2 pi 2 16 Radians Pitch angle 360 72 16 3 4 yawAngleTrue 12 2 pi 2 16 Radians Yaw angle free 360 7 2 16 q 6 xRateCorrected 12 7 pi 2 16 rad s X angular rate corrected 1260 2 16 sec 8 yRateCorrected 12 7 pi 2 16 rad s Y angular rate corrected 1260 2 16 _ 10 zRateCorrected 2 7 pi 2 16 rad s Z angular rate corrected 126072 16 sec 12 xAccel 12 20 2 16 g X accelerometer Doc 7430 0131 01 Rev E Page 50 440 Series User s Manual Crossb w 14 yAccel 12 20 2 16 g Y accelerometer 16 z
73. el 2 20 2 16 9 X accelerometer 8 timelTOWtruncated U2 1 ms DMU ITOW sync to GPS truncated to two bytes Doc 7430 0131 01 Rev E Page 53 440 Series User s Manual Crossb w 8 Advanced Commands The advanced commands allow users to programmatically change the 440 Series settings This section of the manual documents all of the settings and options contained under the Unit Configuration tab within NAV VIEW 2 X Using these advanced commands a user s system can change or modify the settings without the need for NAV VIEW 2 X 8 1 Configuration Fields Configuration fields determine various behaviors of the unit that can be modified by the user These include settings like baud rate packet output rate and type algorithm type etc These fields are stored in EEPROM and loaded on power up These fields be read from the EEPROM using the RF command These fields can be written to the EEPROM affecting the default power up behavior using the WF command The current value of these fields which may be different from the value stored in the EEPROM can also be accessed using the GF command All of these fields can also be modified immediately for the duration of the current power cycle using the SF command The unit will always power up in the configuration stored in the EEPROM Configuration fields can only be set or written with valid data from the table below configuration fields field ID
74. ent packet In addition there is a diagnostic packet TO that can be requested via the Get Packet GP command which contains a complete set of status for each hardware and software subsystem in the VG440 See Sections 6 and 7 for details on the 0 packet The BIT word contained within each measurement packet is detailed below The LSB Least Significant Bit is the Error byte and the MSB Most Significant Bit is a Status byte with programmable alerts Internal health and status are monitored and communicated in both hardware and software The ultimate indication of a fatal problem is the masterFail flag The masterStatus flag is a configurable indication that can be modified by the user This flag is asserted as a result of any asserted alert signals which have been enabled See Advanced BIT Section 9 for details on configuring the masterStatus flags Table 10 shows the BIT definition and default settings for BIT programmable alerts in the VG440 Table 10 VG440 Default BIT Status Definition BITstatus Field Bits Meaning Category masterFail 0 0 normal 1 fatal error has occurred BIT HardwareError 1 0 normal 1 internal hardware error BIT comError 2 0 normal 1 communication error BIT softwareError 3 0 normal 1 internal software error BIT Reserved 4 7 N A masterStatus 8 0 nominal 1 one or more status alerts Status hardwareStatus 9 Disabled Status Doc 7430 0131 01
75. entire packet excluding the 0x5555 header and the CRC field itself A discussion of the 16 bit CRC CCITT and sample code for implementing the computation of the CRC is included at the end of this document This 16 bit CRC standard is maintained by the International Telecommunication Union ITU The highlights are Width 16 bits Polynomial 0x1021 Initial value OXFFFF No XOR performed on the final value See Appendix C for sample code that implements the 16 bit CRC algorithm 6 3 6 Messaging Overview The following table summarizes the messages available by 440 Series model Packet types are assigned mostly using the ASCII mnemonics defined above and are indicated in the summary table below and in the detailed sections for each command The payload byte length is often related to other data elements in the packet as defined in the table below The referenced variables are defined in the detailed sections following Output messages are sent from the 440 Series inertial system to the user system as Doc 7430 0131 01 Rev E Page 39 440 Series User s Manual Crossb w a result of a poll request or a continuous packet output setting Input messages are sent from the user system to the 440 Series inertial system and will result in an associated Reply Message or NAK message Note that reply messages typically have the same lt 2 byte packet type U2 gt as the input message that evoked it but with a different payload Message Table
76. eries User s Manual Crossb w 14 3 5 Return Shipping Address Use the following address for all returned products Crossbow Technology Inc 1421 McCarthy Blvd Milpitas CA 95035 Attn RMA Number XXXXXX 14 4 Warranty The Crossbow product warranty is one year from date of shipment Doc 7430 0131 01 Rev E Page 80 440 Series User s Manual Crossb w Crossb w Crossbow Technology Inc 1421 McCarthy Blvd Milpitas CA 95035 Phone 408 965 3300 Fax 408 324 4840 Email info xbow com Website www xbow com Doc 7430 0131 01 Rev E Page 81
77. ers can utilize the VCR style controls at the top of the page to start stop and pause the playback of the data 4 NAV VIEW 2 X also provides users with the ability to alter the start time for data playback Using the 1 slidebar at the top of the page users can adjust the starting time 3 6 Raw Data Console NAV VIEW 2 X offers some unique debugging tools that may assist programmers in the development process One such tool is the Raw Data Console From the View drop down menu simply select the Raw Data Console This console provides users with a simple display of the packets that have been transmitted to the unit Tx and the messages received Rx An example is provided below Figure 2 Raw Data Console Raw Data Console Tx 5555 9ef4 5555 4944 233d 5555 0300010003071c 49f9 5555 5652 4287 5555 9ef4 5555 4944 233d 5555 0300010003071c 49f9 5555 5652 4287 0002000000020000 21 5 01 0000000000000000000000000000 000200000002 21 5 01 000000000000000000000000000 000200000001 21 5 01 000000000000000000000000000 000200000001 21 5 01 000000000000000000000000000 ffd8ffbaD000200000001ffffffZlff5cOlae0000000000000000000000000000 ffd8ffba000200000001ffffffZlff5cOlaeO0000000000000000000000000000 ffdS8ffba000200000001ffffffZZff5cOlaeO0000000000000000000000000000 ffd8ffba000200000000ffffffZZff5cOlaeO0000000000
78. field contains flags that indicate low level power system errors The powerError flag in the hardwareBIT field is the bit wise OR of this hardwarePowerBIT field hardwarePowerBIT Field Bits Meaning Category inpPower 0 0 normal 1 out of bounds Soft inpCurrent 1 0 normal 1 out of bounds Soft inpVoltage 2 0 normal 1 out of bounds Soft fiveVolt 3 0 normal 1 out of bounds Soft threeVolt 4 0 normal 1 out of bounds Soft twoVolt 5 0 normal 1 out of bounds Soft twoFiveRef 6 0 normal 1 out of bounds Soft six Volt 7 0 normal 1 out of bounds Soft grdRef 8 0 normal 1 out of bounds Soft Reserved 9 15 N A 9 5 hardwareEnvironmentalBIT Field The hardwareEnvironmentalBIT field contains flags that indicate low level hardware environmental errors The environmentalError flag in the hardwareBIT field is the bit wise OR of this hardwareEnvironmentalBIT field hardwareEnvironmentalBIT Field Bits Meaning Category pcbTemp 0 0 normal 1 out of bounds Soft Reserved 9 15 N A 9 6 comBIT Field The comBIT field contains flags that indicate communication errors with external devices Each external device has an associated message with low level error signals The comError flag in the BITstatus field is the bit wise OR of this comBIT field Field Bits Meaning Category serialAError 0 0 normal 1 error Soft serialBError 1 0 normal 1 error Soft Reserved 2 15 N A 97 comSerialABIT Field The comSe
79. field disturbances near the unit gt IMPORTANT An acceptable calibration will provide X and Y Hard Iron Offset Values of 0 1 and a Soft Iron Ratio 20 95 If this procedure generates any values larger than stated above the system will assert the softwareError gt dataError gt magAlignOutOfBounds error flag See section 9 for details on error flag handling 3 13 Read Unit Configuration NAV VIEW 2 X allows users to view the current settings and calibration data for a given 440 series unit by accessing the Read Configuration selection from the Configuration drop down menu From this dialog users can print a copy of the unit s current configuration and calibration values with the click of a button Simply select the Read button at the top of the dialog box and upon completion select the Print or Print Preview buttons to print a copy to your local network printer This information can be helpful when storing hard copies of unit configuration replicating the original data sheet and for troubleshooting if you need to contact Crossbow s Support Staff Figure 8 Read Configuration Read Unit Configuration Unit ID Model Version Firmware Serial Number Unit Default Settings Packet Type Packet Rate Baud Rate External GPS GPS Baud GPS Protocol User Behavior Switch O Freely Integrate 0 Use Mags Use GPS L Stationary Yaw Lock Restart Over Range Dynamic Motion Filter C
80. for both the softwareStatus and hardwareStatus See Sections 9 of the user s manual for all the BIT fields Doc 7430 0131 01 Rev E Page 33 440 Series User s Manual Crossb w 5 Application Guide 5 1 Introduction This section provides recommended advanced settings for tailoring the 440 series of inertial systems to different types of application and platform requirements 5 2 Fixed Wing Aircraft A fixed wing aircraft is a heavier than air craft where movement of the wings in relation to the aircraft is not used to generate lift The term is used to distinguish from rotary wing aircraft where the movement of the wing surfaces relative to the aircraft generates lift The fixed wing aircraft can range in size from the smallest experimental plane to the largest commercial jet The dynamic characteristics of the fixed wing aircraft depends upon types of aircraft 1 g glider propeller aircraft and jet aircraft and mission phases i e launch landing and maneuver In order to meet application requirements users must dial in proper advanced settings so that the 440 series can provide the best possible solution under given dynamic conditions For example Table 17 provides the recommended advanced settings for four different dynamic conditions Table 17 Recommended Advanced Settings for Fixed Wing Aircraft 22 55 AHRS440 or 440 Dynamic Condition Recommended Pre launch or Nor
81. g Magnetometers scaled to a range of 1 1 Gauss Temperature scaled to a range of 100 100 C Velocities are scaled to a range of 256 256 m s Altitude is scaled to a range of 100 16284 m using a shifted 2 s complement representation Longitude and latitude are scaled to a range of pi pi or 180 deg to 180 deg N1 Payload Contents Byte Name Format Scaling Units Description Offset 0 rollAngle 2 2 pi 2 16 Radians Roll angle 360 727161 9 2 pitchAngle 2 2 pi 2 16 Radians Pitch angle 360 7 2 16 3 4 yawAngleTrue 2 2 pi 2 16 Radians Yaw angle true north 360 727161 9 6 xRateCorrected 12 7 pi 2 16 rad s X angular rate corrected 1260 2 16 sec 8 yRateCorrected 12 7 pi 2 16 rad s Y angular rate corrected 1260 2 16 sec 10 zRateCorrected 12 7 pi 2 16 rad s Z angular rate corrected 1260 2 16 sec 12 xAccel 2 20 2 16 g X accelerometer 14 yAccel 12 20 2 16 g Y accelerometer 16 zAccel 12 20 2 16 0 Z accelerometer 18 nVel 12 512 2 16 m s North velocity 20 12 512 2 16 m s East velocity 22 dVel 12 512 2 16 m s Down velocity 24 longitudeGPS l4 2 pi 2 32 Radians GPS Longitude 360 7 232 3 28 latitudeGPS l4 2 pi 2 32 Radians GPS Latitude 360 7 232 9 32 altitudeGPS 2 2 14 2 16 GPS altitude 100 16284 34 xRateTemp 12 200 2 16 deg X rate sensor temperature 36 timelTOW U4 1 ms DM
82. g any equipment please contact Crossbow to obtain a Returned Material Authorization number RMA Be ready to provide the following information when requesting a RMA e Name Address e Telephone Fax Email e Equipment Model Number e Equipment Serial Number e Installation Date e Failure Date e Fault Description e Will it connect to NAV VIEW 2 X 14 3 2 Identification and Protection If the equipment is to be shipped to Crossbow for service or repair please attach a tag TO THE EQUIPMENT as well as the shipping container s identifying the owner Also indicate the service or repair required the problems encountered and other information considered valuable to the service facility such as the list of information provided to request the RMA number Place the equipment in the original shipping container s making sure there is adequate packing around all sides of the equipment If the original shipping containers were discarded use heavy boxes with adequate padding and protection 14 3 3 Sealing the Container Seal the shipping container s with heavy tape or metal bands strong enough to handle the weight of the equipment and the container 14 3 4 Marking Please write the words FRAGILE DELICATE INSTRUMENT in several places on the outside of the shipping container s In all correspondence please refer to the equipment by the model number the serial number and the RMA number Doc 7430 0131 01 Rev E Page 79 440 S
83. ggered environment reading the queue looking for packets A separate process might add data to this queue when it arrives It is up to the user to ensure circular queue integrity by using some sort of mutual exclusion mechanism withing the queue access funtions Doc 7430 0131 01 Rev E Page 70 440 Series User s Manual 12 2 Code listing include lt stdio h gt buffer size define MAXQUEUE 500 circular queue typedef struct queue_tag int count int front int rear char entry MAXQUEUE QUEUE TYPE crossbow packet typedef struct packet unsigned short packet type char unsigned short crc char XBOW PACKET QUEUE TYPE circ buf BK k K k k K k K k K K K K k K K K K k K K K K k OK K K K K K k K KOK K KOK K K K KOK K K KOK K K K K KOK KOK K K K KOK KOK K K K k K EE K k k R K k FUNCTION process xbow packet looks for packets in a queue data 256 ARGUMENTS queue ptr is pointer to queue to process result RETURNS 0 when failed 1 when successful Fe KAR A RAR I E E E A I A I A A int process xbow packet QUEUE TYPE queue ptr PACKET result unsigned short myCRC 0 char packet 100 tempchar if Empty queue ptr return 0 empty buffer find header for numToPop 0 numToPop 41 Size queue ptr if 0x5555 peekWord queue_ptr Pop queue_ptr numToPop numToPop will contain the pa
84. gnals pass through one or more of the processing blocks and these signals are converted into output measurement data as shown Measurement data packets are available at fixed continuous output rates or on a polled basis The type of measurement data packets available depends on the unit type according to the software block diagram and Table 6 Aiding sensor data is used by an Extended Kalman Filter EKF for drift correction in the NAV AHRS and VG Series products Built In Test and Status data is available in the measurement packet or via the special Status Packet TO As shown in the software block diagram the 440 Series has a unit setting and profile block which configures the algorithm to user and application specific needs This feature is one of the more powerful features in the 440 Series architecture as it allows the 440 Series to work in a wide range of commercial applications by settings different modes of operation for the 440 Series Doc 7430 0131 01 Rev E Page 18 440 Series User s Manual Crossb w Figure 10 440 Series Software Block Diagram Measurement IMU Scaled Packets VG AHRS Angle m Data Available to S0 S1 S2 Packets 8 Packets m User Fixed Rate All Units A0 A1 A2 N orPolled EHEHEEEHEEHEEREREEH NAVAHRS VG IMU NAV AHRS VG BEEBE eee 6 DOF Sensor Cluster s as 100 2 gt
85. gt lt CRC U2 gt The unit will send this packet in response to a calibrate request if the procedure can be performed or initiated WC Payload Contents Byte Name Format Scaling Units Description Offset 0 calibrationRequest U2 The requested calibration task 7 2 8 Calibration Completed Parameters Response Calibrate Completed CC 0x4343 0 5555 0x4343 CC payload CRC U2 gt The unit will send this packet after a calibration has been completed Currently there is only one message of this type sent after a magnetic calibration has been completed with or without automatic termination and the parameters have been calculated Thus the calibrationRequest field will be 0x000B or 0x000C CC Payload Contents Byte Name Format Scaling Units Description Offset 0 calibrationRequest U2 2 The requested calibration task 2 xHardlron 12 2 2 16 G The x hard iron bias 4 yHardlron 2 2 2 16 G The y hard iron bias 6 softlronScaleRatio U2 2 246 The scaling ratio between the x and y axis Doc 7430 0131 01 Rev E Page 44 440 Series User s Manual Crossb w 7 2 9 Error Response Error Response ASCII NAK NAK z 0x1515 Packet Type Payload 0x5555 0x1515 lt payload gt CRC U2 gt The unit will send this packet in place of a normal response to a failedlnputPacketType request if it could not be completed
86. h outputs An unrecoverable error is one where can not stabilize the resulting roll and pitch reading If the over ranges are expected to be of short duration 1 sec and a modest percentage over the maximum operating range it is recommended that the restart on over range setting be turned off Handling of an inertial rate sensor over range is controlled using the restartOnOverRange switch If this switch is off the system will flag the overRange status flag and continue to operate through it If this switch is on the system will flag a masterFail error during an over range condition and continue to operate with this flag until a quasi static condition is met to allow for an algorithm restart The quasi static condition required is that the absolute value of each low passed rate sensor fall below 3 deg sec to begin initialization The system will then attempt a normal algorithm start Dynamic ON The default setting is ON for the AHRS440 Turning off the dynamic motion Motion setting results in a higher gain state that uses the accelerometer feedback heavily During periods of time when there is known low dynamic acceleration this switch can be turned off to allow the attitude estimate to quickly stabilize Turn 0 5 With respect to centripetal or false gravity forces from turning dynamics or Switch deg sec coordinated turn the AHRS440 monitors the yaw rate If the yaw rate exceeds a threshold given Turnswitch thres
87. h status flag Using the turn switch maintains better attitude accuracy during short term dynamic situations but care must be taken to ensure that the duty cycle of the turn switch generally stays below 10 during the vehicle mission A high turn switch duty cycle does not allow the system to apply enough rate sensor bias correction and could allow the attitude estimate to become unstable The VG440 algorithm has two major phases of operation The first phase of operation is the initialization phase During the initialization phase the VG440 is expected to be stationary or quasi static so the EKF weights the accelerometer gravity reference Doc 7430 0131 01 Rev E Page 23 440 Series User s Manual Crossb w heavily in order to rapidly estimate the roll and pitch angles and X Y rate sensor bias The initialization phase lasts approximately 60 seconds and the initialization phase can be monitored in the softwareStatus BIT transmitted by default in each measurement packet After the initialization phase the VG440 operates with lower levels of feedback also referred to as EKF gain from the accelerometers to continuously estimate and correct for roll and pitch errors as well as to estimate X and Y rate sensor bias If a user wants to reset the algorithm or re enter the initialization phase sending the algorithm reset command AR will force the algorithm into the reset phase The VG440 outputs digital measurement data over the RS 232 se
88. he X and Y axes Freely OFF The Freely Integrate setting allows a user to turn the AHRS440 into a free gyro Integrate In free gyro mode the roll pitch and yaw are computed exclusively from angular rate with no kalman filter based corrections of roll pitch or yaw When turned on there is no coupling of acceleration based signals into the roll and pitch or magnetometer based signals to the yaw As a result the roll pitch and yaw outputs will drift roughly linearly with time due to sensor bias For best performance the Freely Integrate mode should be used after the algorithm has initialized This allows the Kalman Filter to estimate the roll and pitch rate sensor bias prior to entering the free gyro mode Upon exiting the free gyro mode OFF one of two behaviors will occur 1 If the AHRS440 has been in freely integrate mode for less than sixty seconds the algorithm will resume operation at normal gain settings 2 If the AHRS440 has been in freely integrate mode for greater than sixty seconds the algorithm will force a reset and reinitialize with high gains automatically Use Mags ON The Use Mags setting allows users to turn on and off the magnetometer feedback for yaw heading stabilization The default setting is ON for the AHRS440 When Use Mags is turned ON the AHRS440 uses the magnetic field sensor readings to stabilize the drift in yaw and it slaves the yaw to the compass reading provided from the magnetic f
89. hese intermediate signals Each of these intermediate signals has a separate field with individual indication flags Each of these indication flags can be enabled or disabled by the user Any enabled indication flag will trigger the associated intermediate signal and masterStatus flag BITstatus Field Bits Meaning Category masterFail 0 0 normal 1 fatal error has occurred BIT HardwareError 1 0 normal 1 internal hardware error BIT comError 2 0 normal 1 communication error BIT softwareError 3 0 normal 1 internal software error BIT Reserved 4 7 N A masterStatus 8 0 nominal 1 hardware sensor com or Status software alert hardwareStatus 9 0 nominal 1 programmable alert Status comStatus 10 0 nominal 1 programmable alert Status softwareStatus 11 0 nominal 1 programmable alert Status sensorStatus 12 0 nominal 1 programmable alert Status Reserved 13 15 N A Doc 7430 0131 01 Rev E Page 62 440 Series User s Manual Crossb w 9 3 hardwareBIT Field The hardwareBIT field contains flags that indicate various types of internal hardware errors Each of these types has an associated message with low level error signals The hardwareError flag in the BITstatus field is the bit wise OR of this hardwareBIT field hardwareBIT Field Bits Meaning Category powerError 0 0 normal 1 error Soft environmentalError 1 0 normal 1 error Soft reserved 2 15 N A 94 hardwarePowerBIT Field hardwarePowerBIT
90. hold the feedback gains from the accelerometer signals for attitude correction are reduced because they are likely corrupted BIT See 4 4 3 44 3 5440 Built In Test As with the IMU440 and VG440 the Built In Test capability allows users of the AHRS440 to monitor health diagnostic and system status information of the unit in real time The Built In Test information consists of a BIT word 2 bytes transmitted in every measurement packet In addition there is a diagnostic packet that can be requested via the Get Packet GP command which contains a complete set of status for each hardware and software subsystem in the AHRS440 See Sections 6 and 7 of the Programming Guide for details on the TO packet The BIT word contained within each measurement packet is detailed below The LSB Least Significant Bit is the Error byte and the MSB Most Significant Bit is a Status byte with programmable alerts Internal health and status are monitored and communicated in both hardware and software The ultimate indication of a fatal problem is the masterFail flag The softwareError bit also provides useful information regarding the status and quality of the AHRS440 magnetic alignment If the AHRS440 has not been properly magnetically calibrated the AHRS440 shall indicate a softwareError The masterStatus flag is a configurable indication that can be modified by the user This flag is asserted as a result of any asserted aler
91. however accelerometer noise bias and attitude error will cause the velocity estimates to start drifting within a few seconds The attitude tracking performance will degrade the heading will freely drift and the filter will revert to the VG only EKF formulation The UTC packet synchronization will drift due to internal clock drift The status of GPS signal acquisition can be monitored from the hardwareStatus BIT as discussed in Section 4 5 3 NAV440 Built in Test From a cold start it typically takes 40 seconds for GPS to lock The actual lock time depends on the antenna s view of the sky and the number of satellites in view The DSP performs time triggered trajectory propagation at 100Hz and will synchronize the sensor sampling with the GPS UTC Universal Coordinated Time second boundary when available As with the AHRS440 and VG440 the algorithm has two major phases of operation Immediately after power up the NAV440 uses the accelerometers and magnetometers to compute the initial roll pitch and yaw angles The roll and pitch attitude will be initialized using the accelerometer s reference of gravity and yaw will be initialized using the leveled magnetometers X and Y Doc 7430 0131 01 Rev E Page 30 440 Series User s Manual Crossb w axis reference of the earth s magnetic field During the first 60 seconds of startup the NA V440 should remain approximately motionless in order to properly initialize the rate sensor bias The initializa
92. ield sensor readings When Use Mags is turned OFF the heading yaw angle measurement of the AHRS440 will drift and freely integrate In effect this setting converts an AHRS440 into the functionality of the VG440 However unlike a VG440 this can be done on a selectable basis and changed in real time during a mission The reason for this setting is to give the user an ability to turn off the magnetometer stabilization when severe magnetic distortion may be occurring This setting is desirable when the user system temporarily moves Doc 7430 0131 01 Rev E Page 28 440 Series User s Manual Crossb w in close proximity to a large ferrous object When the Use Mags switch is turned from OFF to ON the AHRS440 will reinitialize the yaw heading angle with the compass reading provided from the magnetic field sensor readings Restart On OFF This setting forces an algorithm reset when a sensor over range occurs i e a Over rotational rate on any of the three axes exceeds the maximum range The default Range setting is OFF for the 5440 Algorithm reset returns the AHRSA40 to a high gain state where the AHRS440 rapidly estimates the gyro bias and uses the accelerometer feedback heavily This setting is recommended when the source of over range is likely to be sustained and potentially much greater than the rate sensor operating limit Large and sustained angular rate over ranges result in unrecoverable errors in roll and pitc
93. ight in which an aircraft reaches its nominal flight altitude and maintains its speed and altitude The aircraft is under equilibrium e Maneuver is the phase of flight in which an aircraft accelerates decelerates and turns The aircraft is under non gravitational acceleration and or deceleration e Descent is the phase of flight in which an aircraft decreases altitude for an approach to landing The aircraft is under vertical deceleration until it captures a glide slope e Landing is the last part of a flight where the aircraft returns to the ground Doc 7430 0131 01 Rev E Page 36 440 Series User s Manual Crossb w Figure 13 Typical flight profiles of fixed wing aircraft and the corresponding advanced settings Pre launch or known straight and level un accelerated flight Straight and level Normal Dynamics Normal Dynamics Pre launch or Climb Maneuver Descent known straight and level un accelerated High Dynamics Prelaunch Takeoff Landing __ Recommended Advanced Settings Doc 7430 0131 01 Rev E Page 37 440 Series User s Manual Crossb w 6 Programming Guide The 440 Series contains a number of different products which have different measurement capabilities Depending on the model you purchased various commands and output modes are supported However all models support a common packet structure that includes both command or input data packets data sent to the 440 Series and measure
94. ignals for attitude correction are reduced because they are likely corrupted BIT See 4 5 3 4 5 3 NAV440 Built In Test As with the IMU VG and AHRS440 the Built In Test capability allows users of the NA V440 to monitor health diagnostic and system status information of the unit in real time The Built In Test information consists of a BIT word 2 bytes transmitted in every measurement packet In addition there is a diagnostic packet that can be requested via the Get Packet GP command which contains a complete set of status for each hardware and software subsystem in the 440 See Section 6 and 7 Programming Guide for details on the 0 packet The BIT word contained within each measurement packet is detailed below The LSB Least Significant Bit is the Error byte and the MSB Most Significant Bit is a Status byte with programmable alerts Internal health and status are monitored and communicated in both hardware and software The ultimate indication of a fatal problem is the masterFail flag The softwareError bit also provides useful information regarding the status and quality of the NAV440 magnetic alignment If the 440 has not been properly magnetically calibrated the NA V440 shall indicate a softwareError The masterStatus flag is a configurable indication that can be modified by the user This flag is asserted as a result of any asserted alert signals which have been enabled See Advanced Settings for
95. ing angle rapidly unlike the aircraft which requires banking A turn switch threshold that is too low may cause turn switch activation with high duty cycle causing random walk in roll and pitch angles due to low feedback gains A cutoff frequency must be far away from major frequency components caused by the rotor vibration 5 4 Land Vehicle Some examples of land vehicles are Automobiles trucks heavy equipment trains snowmobiles and other tracked vehicles Table 19 provides the recommended advanced settings for two different types of application Table 19 Recommended Advanced Settings for Land Vehicle Recommended Product VG440 or NAV440 Dynamic Condition Recommended Settings Heavy Equipment Automotive Testing Application IMU and VG default UseMags ONS ONS UseGPS ON ON lt 4g FreelyIntegrate OFF OFF Stationary Yaw Lock OFF OFF Restart Over Range ON OFF Dynamic Motion ON ON Turn Switch Threshold 5 0 deg s 10 0 deg s XY Filter Accel 5 Hz 5 Hz Z Filter Accel 5 Hz 5 Hz Filter Rate Sensor 20 Hz 20 Hz When not in distorted magnetic environment Doc 7430 0131 01 Rev E Page 35 440 Series User s Manual Crossb w 5 5 Water Vehicle Water vehicle is a craft or vessel designed to float on or submerge and provide transport over and under water Table 20 provides the recommended advanced settings for two different types of application Table 20 Recommended Adv
96. ing command using the full packet formation with payload 0 and correctly calculated CRC Example 0x5555504B009ef4 6 3 1 Packet Header The packet header is always the bit pattern 0x5555 6 3 2 Packet The packet type is always two bytes long in unsigned short integer format Most input and output packet types can be interpreted as a pair of ASCII characters As a semantic aid consider the following single character acronyms P packet fields Refers to Fields which are settings or data contained in the unit E EEPROM Refers to factory data stored in EEPROM R read Reads default non volatile fields G get Gets current volatile fields or settings W write Writes default non volatile fields These fields are stored in non volatile memory and determine the unit s behavior on power up Modifying default fields take effect on the next power up and thereafter S set Sets current volatile fields or settings Modifying current fields will take effect immediately by modifying internal RAM and are lost on a power cycle 6 3 3 Payload Length The payload length is always a one byte unsigned character with a range of 0 255 The payload length byte is the length in bytes of the variable length payload portion of the packet ONLY and does not include the CRC 6 3 4 Payload The payload is of variable length based on the packet type 6 3 5 16 bit CRC CCITT Packets end with a 16 bit CRC CCITT calculated on the
97. ion packet must be transmitted to the 440 Series inertial system within a 4 second period 6 2 Number Formats Number Format Conventions include e as prefix to hexadecimal values e single quotes 7 to delimit ASCH characters e prefix or delimiters to specify decimal values The following table defines number formats Table 21 Number Formats Descriptor Description Size bytes Comment Range Ul Unsigned Char 1 0 to 255 U2 Unsigned Short 2 0 to 65535 U4 Unsigned Int 4 0 to 2 32 1 D Signed Short 2 2 s Complement 2 15 to 2 15 1 D Signed Short 2 Shifted 2 s Shifted to specified Complement range I4 Signed Int 4 2 s Complement 2431 to 2431 1 F4 Floating Point 4 IEEE754 Single 1 24127 to 24127 Precision SN String N ASCII 6 3 Packet Format AII of the Input and Output packets except the Ping command conform to the following structure 2 byte packet payload byte variable length 2 byte CRC 0x5555 type U2 length U1 payload U2 Doc 7430 0131 01 Rev E Page 38 440 Series User s Manual Crossb w The Ping Command does not require a CRC so a 440 Series unit can be pinged from a terminal emulator To Ping a 440 Series unit type the ASCII string UUPK If properly connected the 440 Series unit will respond with PK All other communications with the 440 Series unit require the 2 byte CRC Note A 440 Series unit will also respond to a p
98. ish to have additional visibility to when the AHRS440 EFK algorithm estimates that the AHRS440 is turning about its Z or Yaw axis the softwareStatus bit can be configured to go high during a turn In other words the turnSwitch will turn on the softwareStatus bit In the AHRS440 the turnSwitch is by default set at 0 5 deg sec about the Z axis 4 5 440 Theory of Operation The NAV440 supports all of the features and operating modes of the IMU VG AHRS440 and it includes an additional internal WAAS capable GPS receiver and associated software running on the DSP processor for the computation of navigation information as well as orientation information The product name NAV440 stands for Navigation System 440 it is indicative of the navigation reference functionality that the NAV440 provides by outputting GPS information Latitude Longitude and Altitude inertially aided 3 axis velocity information as well as heading roll and pitch measurements in addition to digital IMU data An AHRS440 configured and properly connected to an external GPS also behaves as a NAV440 At a fixed 100Hz rate the NA V440 continuously maintains the digital IMU data the dynamic roll pitch and heading data as well as the navigation data As shown in the software block diagram in Figure 10 after the Sensor Calibration block the IMU data is passed into an Integration to Orientation block The Integration to Orientation block integrates body frame sensed ang
99. lgorithm Reset AR 0x4152 Packet Type Payload 0x5555 0 4152 O00 1 This command resets the state estimation algorithm without reloading fields from EEPROM current field values will remain in affect The unit will respond with an algorithm reset response 7 2 3 Algorithm Reset Response Algorithm Reset AR 0x4152 0 5555 0 4152 U2 gt The unit will send this packet in response algorithm reset command 7 2 4 Software Reset Command Software Reset SR 0x5352 Packet Type Payload 0x5555 0x5352 o00 CRC U2 This command performs a core CPU reset functionally equivalent to a power cycle All default power up field settings will apply The unit will respond with a software reset response before the system goes down 7 2 5 Software Reset Response Software Reset SR 0x5352 Packet Type 0 5555 0x5352 CRC U2 gt The unit will send this packet in response to a software reset command 7 2 6 Calibrate Command Calibrate WC 0x5743 Packet Type Length Payload 0x5555 0x5743 lt WC payload gt lt CRC U2 gt This command allows the user to perform various calibration tasks with the 440 Series See the calibration command table below for details The unit will respond immediately with a calibrate response containing the calibrationRequest received or an error response if the command cannot be performed
100. lid 0006ffe4ed91 fff9fffdffed fff7fff9f331 2c642ce12d85 00010blc 0300 timeITOW Hex Data Value s 00010b1c 68380 Hex Value Data deg 0006 0 033 roll Hex Value Data 9 FFF7 0 0027 x FFE4 0 154 FFF9 0 0021 pitch y ED91 25 922 F331 1 0007 yaw z Hex Value Hex Value Data deg s Data deg C 2C64 34 680 FFF9 0 13 roll 2CE1 35 062 itch PCR 2D85 35 562 FFED 0 37 yaw BIT status Field Field Value masterFail hardwareError comError softwareError reserved 0000 masterStatus hardwareStatus comStatus PEN softwareStatus lo o oo sensorStatus reserved Doc 7430 0131 01 Rev E Page 76 440 Series User s Manual Crossb w Example payload from Scaled Sensor 1 data packet S1 5555 5331 18 0000fffef332 fff30001fff8 23b9242624ca2aff 9681 0300 248a nreamhle lenoth counter invalid status Field n Hex Value Data deg C 23B9 28 241 2426 28 741 24CA 33 591 2AFF 38 968 Hex Value Data deg s Hex Value Data g FFFE 0 001 0 om n o antares J comsiatis 0 Doc 7430 0131 01 Rev E Page 77 440 Series User s Manual Example payload from Nav Data Packet 1 N1 5555 4e31 2a ee 001bffdf3a5bfffe0000ffe preamble tvne Crossb w fff8fff70000002
101. lock Rate FilterClocks FilterClock1 FilterClock2 FilterClock3 LP Cutoff Hz Print Preview Product Configuration O Contains Mags L Algorithm Enabled Architecture Internal GPS External Aiding Magnetometers Parameters Value mii X hard iron offset Y hard iron offset Soft iron ratio Axes Orientation Customer Axes Unit Reference Axes x jr z Heading Track Offset Turn Switch Threshold Hardware Status Enable Fields O Unlocked 1PPS L Unlocked Internal GPS No DGPS Unlocked Eeprom Software Status Enable Fields algorithm Initializing High Gain O Altitude Only Alg O Turn Switch Sensor Status Enable Fields L Sensor Over Range Comm Status Enable Fields No External GPS Doc 7430 0131 01 Rev E Page 16 440 Series User s Manual Crossb w 4 Theory of Operation This section of the manual covers detailed theory of operation for each member of the 440 Series starting with the basic IMU440 and then reviewing each major variant VG AHRS and NAV with their associated additional features outputs and performance Table 6 shows the basic features of each member of the 440 Series with cross references to important sections for review Table 6 440 Series Overview Product Features Learning More IMU440 6 DOF Digital IMU Read 4 1 and 4 2 440 6 DOF IMU plus Dynamic Roll Pitch optional Read 4 1 4 2 a
102. ly record the raw hex strings as they are sent from the unit 5 Users can also select a predetermined Test Duration from the menu Using the arrows simply select the duration of your data recording 6 Logging Rate can also be adjusted using the features on the right side of the menu 7 you have completed the customization of your data recording you will be returned to the main screen where you can start the recording process using the button at the top of the page or select Start Logging from the File menu Stopping the data recording be accomplished using the button and the recording can also be paused using the ll button 3 5 Data Playback In addition to data recording NAV VIEW 2 X allows the user to replay saved data that has been stored in a log file 1 To playback data select Playback Mode from the Data Source drop down menu at the top Data Source LIVE Mode from DMU LIVE Mode From DMU 2 Selecting Playback mode will open a text prompt which will allow users to specify the location of the file they wish to play back All three file formats are supported Engineering Hex and Raw for playback In addition each time recording is stopped started a new section is created These sections can be individually played back by using the drop down menu and associated VCR controls Doc 7430 0131 01 Rev E Page 9 440 Series User s Manual Crossb w 3 Once the file is selected us
103. mal Settings a i Dynamics High Dynamics accelerated flight pea UseMags ON ON ON ON UseGPS ON ON lt 4g ON ON lt 4g FreelyIntegrate OFF OFF OFF OFF lt 2 17 Tow OFF OFF OFF OFF Restart Over Range ON OFF OFF OFF Dynamic Motion OFF ON ON ON Suai 0 5 deg s 0 5 deg s 051 0 5 deg s XY Filter Accel 5Hz 5Hz 5 Hz 15 Hz Z Filter Accel 5Hz 5Hz 5 Hz 15 Hz Filter Rate Sensor 20 Hz 20 Hz 20 Hz 20 Hz A cutoff frequency of filters may be varied depending on the fastest dynamic mode of the aircraft For example the conventional aircraft has five dynamic modes short period phugoid spiral dutch roll and roll and the fastest one is the roll mode The natural frequency of this mode is around 6 8 radian sec or about 2 Hz in most cases Therefore the recommended filter setting would not reject desired frequency components or dynamic modes that one wants to capture However the larger the bandwidth or cutoff frequency is the noisier the corresponding signal is which may result in the performance degradation If the aircraft is operated under severe vibrations also the recommended filter setting may need to be further reduced in order to reject the frequency components caused by the vibration FreelyIntegrate should only be set to for severe launch conditions Normal takeoff dynamics that a standard aircraft would experience will see the best performance with this setting in the OFF
104. measurement if they are not accounted for These extra magnetic fields are called hard iron magnetic fields In addition magnetic material can change the direction of the magnetic field as a function of the input magnetic field This dependence of the local magnetic field on input direction is called the soft iron effect The 5440 actually measure any constant magnetic field that is associated with your system and correct for it The 5440 can also make a correction for some soft iron effects The process of measuring these non ideal effects and correcting for them is called hard iron and soft iron calibration This calibration will help correct for magnetic fields that are fixed with respect to the AHRS440 It cannot help for time varying fields or fields created by parts that move with respect to the AHRS440 Because time varying fields cannot be compensated selection of a proper installation location is important During the calibration procedure the AHRS440 makes a series of measurements while the user system is being turned through a complete 360 degree circle 360 degree rotation gives the AHRS440 visibility to hard and soft iron distortion in the horizontal plane Using NAV VIEW 2 X a user can see the hard and soft iron effects by selecting the Misalignment option on the Configuration Menu and viewing the magnetic circle during the calibration The AHRS440 uses these measurements to model the hard iron and soft iron environme
105. ment output or response packet formats data sent from the 440 Series This section of the manual explains these packet formats as well as the supported commands NAV VIEW 2 X also features a number of tools that can help a user understand the packet types available and the information contained within the packets This section of the manual assumes that the user is familiar with ANSI C programming language and data type conventions For an example of the code required to parse input data packets please see refer to Appendix C For qualified commercial OEM users a source code license of NAV VIEW 2 X can be made available under certain conditions Please contact your Crossbow Technology representative for more information 6 1 General Settings The serial port settings are RS232 with 1 start bit 8 data bits no parity bit 1 stop bit and no flow control Standard baud rates supported are 9600 19200 38400 and 57600 Common definitions include e A word is defined to be 2 bytes or 16 bits e All communications to and from the unit are packets that start with a single word alternating bit preamble 0x5555 This is the ASCII string UU e All multiple byte values are transmitted Big Endian Most Significant Byte First e communication packets end with a single word CRC 2 bytes CRC s are calculated on all packet bytes excluding the preamble and CRC itself Input packets with incorrect CRC s will be ignored e Each complete communicat
106. n is associated with the rate sensor bias terms The Extended Kalman Filter EKF module provides an on the fly calibration for drift errors including the rate sensor bias by providing corrections to the Integration to Orientation block and a characterization of the gyro bias state In the VG440 the internally computed gravity reference vector provides a reference measurement for the EKF when the VG440 is in quasi static motion to correct roll and pitch angle drift and to estimate the X and Y gyro rate bias Because the gravity vector has no horizontal component the EKF has no ability to estimate either the yaw angle error or the Z gyro rate bias The VG440 adaptively tunes the EKF feedback in order to best balance the bias estimation and attitude correction with distortion free performance during dynamics when the object is accelerating either linearly speed changes or centripetally false gravity forces from turns Because centripetal and other dynamic accelerations are often associated with yaw rate the VG440 maintains a low passed filtered yaw rate signal and compares it to the turnSwitch threshold field user adjustable When the user platform to which the VG440 is attached exceeds the turnSwitch threshold yaw rate the VG440 lowers the feedback gains from the accelerometers to allow the attitude estimate to coast through the dynamic situation with primary reliance on angular rate sensors This situation is indicated by the softwareStatus gt turnSwitc
107. nable field The hardwareStatusEnable field is a bit mask that allows the user to select items of interest that will logically flow up to the masterStatus flag hardwareStatus Field Bits Meaning unlocked1PPS 0 0 not asserted 1 asserted unlockedInternalGPS 1 0 not asserted 1 asserted noDGPS 2 0 DGPS lock 1 no DGPS unlockedEEPROM 3 0 WE disabled 1 unlocked WE enabled Reserved 4 15 N A 9 13 comsStatus Field The comStatus field contains flags that indicate various external communication conditions and alerts that are not errors or problems The comStatus flag in the BITstatus field is the bit wise OR of the logical AND of the comStatus field and the comStatusEnable field The comStatusEnable field is a bit mask that allows the user to select items of interest that will logically flow up to the masterStatus flag comStatus Field Bits Meaning noExternalGPS 0 0 external GPS data is being received 1 no external GPS data is available Reserved 1 15 N A 9 14 softwareStatus Field The softwareStatus field contains flags that indicate various software conditions and alerts that are not errors or problems The softwareStatus flag in the BITstatus field is the bit wise OR of the logical AND of the softwareStatus field and the softwareStatusEnable field The softwareStatusEnable field is a bit mask that allows the user to select items of interest that will logically flow up to the masterStatus flag softwareStat
108. nd 4 3 external GPS AHRS440 6 DOF IMU with 3 Axis Internal Magnetometer Read 4 1 4 2 4 3 and 4 4 Dynamic Roll Pitch and Heading Optional External GPS NAV440 6 DOF IMU with 3 Axis Internal Magnetometer Read 4 1 4 2 4 3 4 4 and 4 5 and Internal WAAS Capable GPS Receiver Position Dynamic Velocity and Dynamic Roll Pitch Heading Figure 9 shows the 440 Series hardware block diagram At the core of the 440 Series is a rugged 6 DOF Degrees of Freedom MEMS inertial sensor cluster that is common across all members of the 440 Series The 6 DOF MEMS inertial sensor cluster includes three axes of MEMS angular rate sensing and three axes of MEMS linear acceleration sensing These sensors are based on rugged field proven silicon bulk micromachining technology Each sensor within the cluster is individually factory calibrated using Crossbow s automated manufacturing process Sensor errors are compensated for temperature bias scale factor non linearity and misalignment effects using a proprietary algorithm from data collected during manufacturing Accelerometer rate gyro and magnetometer sensor bias shifts over temperature 40 to 71 are compensated and verified using calibrated thermal chambers and rate tables The 6 DOF sensor cluster data is fed into a high speed A D and DSP processor after passing thru a series of programmable low pass filters The DSP processor outputs attitude and navigation data via the RS 232 port As
109. nderground parking lots or if objects or human beings cover the antenna Poor visibility may result in position drift or a prolonged Time To First Fix TTFF A good sky visibility is therefore a prerequisite Even the best receiver can t make up for signal loss due to a poor antenna in band jamming or a poor RF cable The 440 Series unit ships with external active antenna that must be connected properly to SMA jack located next to the DB 15 connector Placing the antenna on a 4 inch or larger ground plane is highly recommended gt IMPORTANT Place the antenna with optimal sky visibility and use a ground plane Route the GPS Antenna RF cable away from sources of radiated energy i e switching power supplies 2 12 No Connection During normal operation of the 440 Series no connection is made to the factory test pins These pins have internal pull up mechanisms and must have no connections for the 440 Series to operate properly Doc 7430 0131 01 Rev E Page 6 440 Series User s Manual 2 43 Quick Digital interface connection On a standard DB 9 COM port connector make the connections as described in Table 3 Table 5 DB 9 COM Port Connections COM Port Connector 440 Series Connector Pin Signal Pin Signal 2 RxD 1 TxD 3 TxD 2 RxD 5 GND 9 GND Crossb w Doc 7430 0131 01 Rev E Page 7 440 Series User s Manual Crossb w 3 Installation and Operati
110. ne of two behaviors will occur 1 If the VG440 has been in freely integrate mode for less than sixty seconds the algorithm will resume operation at normal gain settings 2 If the VG440 has been in freely integrate mode for greater than sixty seconds the algorithm will force a reset and reinitialize with high gains automatically Doc 7430 0131 01 Rev E Page 24 440 Series User s Manual Crossb w Restart On OFF This setting forces an algorithm reset when a sensor over range occurs 1 Over rotational rate on any of the three axes exceeds the maximum range The default Range setting is OFF for the VG440 Algorithm reset returns the VG440 to a high gain state where the VG440 rapidly estimates the gyro bias and uses the accelerometer feedback heavily This setting is recommended when the source of over range is likely to be sustained and potentially much greater than the rate sensor operating limit Large and sustained angular rate over ranges result in unrecoverable errors in roll and pitch outputs An unrecoverable error is one where the EKF can not stabilize the resulting roll and pitch reading If the over ranges are expected to be of short duration 1 sec and a modest percentage over the maximum operating range it is recommended that the restart on over range setting be turned off Handling of an inertial rate sensor over range is controlled using the restartOnOverRange switch If this switch is off the system
111. nections Customers who are connecting the 440 Series products into a system with their own power supply and cable Section 3 Installation and Operation of NAV VIEW 2 X Customers who are installing the 440 Series products into a system and need details on using NAV VIEW 2 X Section 4 Theory of Operation All customers should read Section 4 As the 440 Series products are inter related use the chart at the beginning of Section 4 to ensure that you get an overview of all of the functions and features of your 440 Series system For example if you have purchased a NA V440 you should read not only the section on the 440 but also familiarize yourself with the theory of operation for the IMU440 VG440 and AHRS440 The NAV440 builds on the capabilities of the IMU440 VG440 and AHRS440 Section 5 Application Guide Customers who want product configuration tips for operating the 440 Series Inertial Systems in a wide range of applications fixed wing rotary wing unmanned vehicles land vehicles marine vessels and more Review the part of Section 5 that is relevant to your application Note NAV and AHRS 440 Series units are preconfigured for airborne applications with normal dynamics VG440 Series units are preconfigured for land applications with automotive testing dynamics All 440 series products allow for complete flexibility in configuration by the user Section 6 9 Programming Communi
112. nnection NAV440 neta te ae eet Ba d iie a ea i i iste dr ii NE 6 2 12 No Connections e oes RELIER OU Hae n eae V DE dete 6 2 13 Quick Digital interface connection eue cedes e 7 Installation and Operation of NA V VIEW 2 Xu a sasa pupun puak then b 8 3 1 NAV VIEW 2 X Computer Requirement itte t ERE E ee He RD haha TR Det 8 3 1 1 VEM Z A uwa h a perdi i de nO Ete taps 8 3 2 eio e e he tie i epe spas EP i d duce int eio te opti ree dre een 8 3 3 Setang up NAV VIEW 2 X etie i uve boi queo Dee eb beu de 8 3 4 Data Recordmg zou RID EU ee etl eee 9 3 5 Data Playback aaa ah oet ase ty te bi iste betreut gu 9 2 0 Raw Data Console SAI a liens OE RO B eI d anie 10 3 7 Horizon and Compass ene pce Ee qaa rete ere eret 11 3 8 Packet Statistics VIEW ie epe pue epe ie Ae u Rr et 11 3 9 Umt Configuration iiie RED RERO a 12 3 10 Advanced Configuration iih rede be poer ebbe nite iets 13 3411 Bit Configuration ere etii i eto p Rte te o eonim e d t i ee ipte Dite 13 3 12 Mag Ahgnment Procedure ette re ea tene eat oases ates erem ic avete tt ient 14 3 12 1 H rd Iton S ft Ir
113. nt in your system and store these as calibration constants in the EEPROM status of the AHRS440 magnetometer calibration is indicated by the softwareError gt dataError gt magAlignOutOfBounds error flag available in the TO packet The user can access the hardIron and softIronScaleRatio calibration data as configuration fields in NAV VIEW 2 or by using the communication protocol Also the softwareError bit of the masterFail byte within the BIT word is transmitted in every measurement packet When the AHRS440 has not been properly calibrated this softwareError bit will be set to fail high In order for the 5440 calibration to work properly the AHRS440 must be installed in your system prior to calibration If you perform the calibration process with the AHRS440 by itself you will only correct for the magnetism in the AHRS440 itself If you then install the AHRS440 in a vehicle for instance and the vehicle is magnetic you will still see errors arising from the magnetism of the vehicle The AHRS440 must be calibrated after installation and prior to use of the system The AHRS440 also provides a command interface for initiating the hard iron soft iron calibration without the using NAV VIEW 2 X The user can send a WC command to initiate the calibration and then rotate the user system through 360 degrees The WC command has two options auto termination and manual termination With auto termination the AHRS440 tra
114. nvironmentalBIT U2 Hardware Environmental BIT Field 8 comBIT U2 communication BIT Field 10 comSerialABIT U2 Communication Serial A BIT Field 12 comSerialBBIT U2 Communication Serial B BIT Field 14 softwareBIT U2 Software BIT Field 16 softwareAlgorithmBIT U2 Software Algorithm Field 18 softwareDataBIT U2 Software Data BIT Field 20 hardwareStatus U2 Hardware Status Field 22 comStatus U2 Communication Status Field 24 softwareStatus U2 Software Status Field 26 sensorStatus U2 Sensor Status Field 7 4 Output Packets Polled or Continuous 7 4 1 Scaled Sensor Data Packet 0 Scaled Sensor Data S0 0x5330 Packet Length Payload 0x5555 0x5330 S0 payload CRC U2 gt This packet contains scaled sensor data The scaled sensor data is fixed point 2 bytes per sensor MSB first for 13 sensors in the following order accels x y z gyros x y z mags x y z temps x y z board Data involving angular measurements include the factor pi in the scaling and can be interpreted in either radians or degrees Angular rates scaled to range of 3 5 pi pi or 630 deg sec to 630 deg sec Accelerometers scaled to a range of 10 10 g Doc 7430 0131 01 Rev E Page 46 440 Series User s Manual Crossb w Magnetometers scaled to a range of 1 1 Gauss Temperature scaled to a range of 100 100 C
115. oft dataError 1 0 normal 1 error Soft Reserved 2 15 N A 9 10 softwareAlgorithmBIT Field The softwareAlgorithmBIT field contains flags that indicate low level software algorithm errors The algorithmError flag in the softwareBIT field is the bit wise OR of this softwareAlgorithmBIT field SoftwareAlgorithmBIT Field Bits Meaning Category initialization 0 0 normal 1 error during Hard algorithm initialization overRange 1 0 normal 1 fatal sensor over Hard range missedNavigationStep 2 0 normal 1 fatal hard deadline Hard missed for navigation Reserved 3 15 N A 9 11 softwareDataBIT Field The softwareDataBIT field contains flags that indicate low level software data errors The dataError flag in the softwareBIT field is the bit wise OR of this softwareDataBIT field Doc 7430 0131 01 Rev E Page 64 440 Series User s Manual Crossb w SoftwareDataBIT Field Bits Meaning Category calibrationCRCError 0 0 normal 1 incorrect CRC on Hard calibration EEPROM data or data has been compromised by a WE command magAlignOutOfBounds 1 0 normal 1 hard and soft iron Hard parameters are out of bounds Reserved 2 15 N A 9 12 hardwareStatus Field The hardwareStatus field contains flags that indicate various internal hardware conditions and alerts that are not errors or problems The hardwareStatus flag in the BITstatus field is the bit wise OR of the logical AND of the hardwareStatus field and the hardwareStatusE
116. om the accelerometers to allow the attitude estimate to coast through the dynamic situation with primary reliance on angular rate sensors This situation is indicated by the softwareStatus gt turnSwitch status flag Using the turn switch maintains better attitude accuracy during short term dynamic situations but care must be taken to ensure that the duty cycle of the turn switch generally stays below 10 during the vehicle mission high turn switch duty cycle does not allow the system to apply enough rate sensor bias correction and could allow the attitude estimate to become unstable As described in 4 3 VG440 theory of operation the 5440 algorithm also has two major phases of operation The first phase of operation is the high gain initialization phase During the initialization phase the AHRS440 is expected to be stationary or quasi static so the EKF weights the accelerometer gravity reference and Earth s magnetic field reference heavily in order to rapidly estimate the X Y and Z rate sensor bias and the initial attitude and heading of the AHRS440 initialization phase lasts approximately 60 seconds and the initialization phase can be monitored in the softwareStatus BIT transmitted by default in each measurement packet After the initialization phase the AHRS440 operates with lower levels of feedback also referred to Doc 7430 0131 01 Rev E Page 26 440 Series User s Manual Crossb w as EKF gain from the accelerometers an
117. on of NAV VIEW 2 X NAV VIEW 2 X has been completely redesigned to allow users to control all aspects of the 440 Series operation including data recording configuration and data transfer For the first time you will be able to control the orientation of the unit sampling rate packet type hard iron calibration and filter settings through NAV VIEW 31 2 X Computer Requirements The following are minimum requirements for the installation of the NAV VIEW 2 X Software CPU Pentium class 1 5GHz minimum e RAM Memory 500MB minimum 1GB recommended Hard Drive Free Memory 20MB Operating System Windows 2000 or XP Properly installed Microsoft NET 2 0 or higher 3 1 1 Install NAV VIEW 2 To install NAV VIEW 2 X onto your computer 1 Insert the CD 440 Series Inertial System in the CD ROM drive 2 Locate the NAV VIEW 2 X folder Double click on the setup exe file 3 Follow the setup wizard instructions You will install NAV VIEW 2 X and NET 2 0 framework 3 2 Connections The 440 Series Inertial Systems products are shipped with a cable to connect the 440 Series to a PC Serial port 1 Connect the 15 pin end of the digital signal cable labeled DMUAA0 to the port on the 440 Series product 2 Connect the 9 pin end of the cable marked DMU440 to User to the serial port of your computer 3 The additional black and red wires on the cable connect power to the 440 Series product Match red
118. otprint of Crossbow s new 440 Series Inertial Systems is compatible with prior generation Inertial Systems including Crossbow s 400 Series IMU400 VG400 AHRS400 and the NA V420 Series products The mounting plate foot print is the same and the connector location is identical The 440 Series products are shorter than their equivalent 400 Series product i e the AHRS440 is shorter than the AHRS400 etc The NA V440 is dimensionally equivalent to the NAV420 For detailed mechanical and installation drawings see appendix A of the manual 1 3 2 Connector Pin Out amp Operating Voltage Current The DB 15 male connector on Crossbow s 440 Series Inertial Systems has a backward compatible pin out with the 400 Series and 420 Series However the 440 Series has a secondary optional use communications port for internal or external GPS 1 3 8 Software Compatibility Crossbow s 440 Series Inertial Systems are NOT software compatible with any previous Crossbow products The 440 Series products utilize a new extensible communication protocol which is documented in section 7 of this manual Additionally the 440 Series includes numerous enhancements and features that allow for better performance in many applications than the comparable 400 or 420 Series products 1 3 4 Operating Performance and Accuracy The 440 Series has been characterized in a wide range of land and airborne applications In the qualification testing the dynamic accuracy of the 440 Serie
119. ower cutoff than the X and Y axes See note on Filter settings below BIT See 4 2 2 NOTE on Analog Filter Clocks Why change the filter settings Generally there is no reason to change the low pass filter settings on the IMU440 or other 440 Series Inertial Systems However when a 440 Series product is installed in an environment with a lot of vibration it can be helpful to reduce the vibration based signal energy and noise prior to further processing on the signal Installing the IMU440 in the target environment and reviewing the data with NAV VIEW 2 X can be helpful to determine if changing the filter settings would be helpful Although the filter settings can be helpful in reducing vibration based noise in the signal low filter settings e g 1Hz also reduce the bandwidth of the signal i e can wash out the signals containing the dynamics of a target Treat the filter settings with caution The analog filter clock settings are shown in default IMU440 coordinate system If the user has configured the coordinate system to a non standard or custom configuration the user must take care to apply the appropriate rotation and configure the filter settings accordingly 4 2 2 IMU440 Built In Test The IMU440 Built In Test capability allows users of the IMU440 to monitor health diagnostic and system status information of the unit in real time The Built In Test information consists of a BIT word 2 bytes transmitted in every meas
120. passing thousands of deployed units and millions of operational hours in a wide range of land marine airborne and instrumentation applications At the core of the 440 Series is a rugged 6 DOF Degrees of Freedom MEMS inertial sensor cluster that is common across all members of the 440 Series 6 DOF MEMS inertial sensor cluster includes three axes of MEMS angular rate sensing and three axes of MEMS linear acceleration sensing These sensors are based on rugged field proven silicon bulk micromachining technology Each sensor within the cluster is individually factory calibrated for temperature and non linearity effects during Crossbow s manufacturing and test process using automated thermal chambers and rate tables Coupled to the 6 DOF MEMS inertial sensor cluster is a high performance DSP processor that utilizes the inertial sensor measurements to accurately compute navigation information including attitude heading and linear velocity thru dynamic maneuvers actual measurements are a function of the 440 Series product as shown in Table 2 In addition the DSP processor makes use of internal and external magnetic sensor and or GPS data to aid the performance of the inertial algorithms and help correct long term drift and estimate errors from the inertial sensors and computations The navigation algorithm utilizes a multi state configurable Extended Kalman Filter EKF to correct for drift errors and estimate sensor bias values This algorithm
121. ponding image of the NA V440 so it easy to visualize the mode of operation See section 8 4 Orientation Field settings for the twenty four possible orientation settings The default setting points the connector AFT Analog 5Hz The low pass filters are set to a default of 5Hz for the accelerometers and 20Hz Filter 20 Hz for the angular rate sensors There is one filter setting for all three angular rate Clocks 1 2 sensors There are two settings for the accelerometers one for the X and Y axes amp 3 and a separate setting for the Z axis The reason for a separate setting in the Z axis is that in many installations the Z axis vibration level is much higher than in the X and Y axes and it can prove helpful to filter the Z axis at a lower cutoff than the X and Y axes Freely OFF Freely Integrate setting allows a user to turn the NA V440 into a free gyro Integrate In free gyro mode the roll pitch and yaw are computed exclusively from angular Doc 7430 0131 01 Rev E Page 31 440 Series User s Manual rate with no kalman filter based corrections of roll pitch and yaw When turned on there is no coupling of acceleration based signals into the roll and pitch or magnetometer based signal to the yaw As a result the roll pitch and yaw outputs will drift roughly linearly with time due to sensor bias For best performance the Freely Integrate mode should be used after the algorithm has initialized Thi
122. rFail flag This flag 18 thrown as a result of a number of instantly fatal conditions known as a hard failure or a persistent serious problem known as a soft failure Soft errors are those which must be triggered multiple times within a specified time window to be considered fatal Soft errors are managed using a digital high pass error counter with a trigger threshold The masterStatus flag is a configurable indication as determined by the user This flag is asserted as a result of any asserted alert signals which the user has enabled The hierarchy of BIT and Status fields and signals is depicted here BlTstatus Field gt masterFail hardwareError e hardwareBIT Field powerError gt hardwarePowerBIT Field inpPower inpCurrent inpVoltage fiveVolt threeVolt twoVolt twoFiveRef sixVolt grdRef environmentalError gt hardwareEnvironmentalBIT Field pcbTemp comError comBIT Field serialAError comSerialABIT Field transmitBufferOverflow receiveBufferOverflow framingError breakDetect parityError serialBError gt comSerialBBIT Field transmitBufferOverflow receiveBufferOverflow framingError breakDetect parityError softwareError e softwareBIT Field algorithmError gt softwareAlgorithmBIT Field initialization overRange missedIntegrationStep dataError gt softwareDataBIT Field Doc 7430 0131 01 Rev E
123. rial link at a selectable fixed rate 100 50 25 20 10 5 or 2 Hz or on as requested basis using the GP Get Packet command In addition to the scaled sensor packets described in the IMU440 section the VG440 has additional measurement output packets including the default 2 Angle Packet which outputs the roll angle pitch angle and digital IMU data 0 and 1 packets are also available for use with an external GPS receiver See Section 6 and 7 of the manual for full packet descriptions 4 39 1 VG440 Advanced Settings In addition to the configurable baud rate packet rate axis orientation and sensor low pass filter settings the VG440 provides additional advanced settings which are selectable for tailoring the VG440 to a specific application requirements These VG440 advanced settings are shown in Tabel 9 below Table 9 VG440 Series Advanced Settings Setting Default Comments Baud Rate 38 400 9600 19200 57600 also available baud Packet A2 51 52 0 also available Packet 25Hz This setting sets the rate at which selected Packet Type packets are output If Rate polled mode is desired then select Quiet If Quiet is selected the VG440 will only send measurement packets in response to GP commands Orientation See To configure the axis orientation select the desired measurement for each axes Fig 12 NAV VIEW 2 X will show the corresponding image of the VG440 so it easy to vis
124. rialABIT field contains flags that indicate low level errors with external serial port the user serial port The serialAError flag in the comBIT field is the bit wise OR of this comSerialABIT field Doc 7430 0131 01 Rev E Page 63 440 Series User s Manual Crossb w comSerialABIT Field Bits Meaning Category transmitBufferOverflow 0 0 normal 1 overflow Soft receiveBufferOverflow 1 0 normal 1 overflow Soft framingError 2 0 normal 1 error Soft breakDetect 3 0 normal 1 error Soft parityError 4 0 normal 1 error Soft Reserved 5 15 N A 9 8 Field The comSerialBBIT field contains flags that indicate low level errors with external serial port B the aiding serial port The serialBError flag in the comBIT field is the bit wise OR of this comSerialBBIT field comSerialBBIT Field Bits Meaning Category transmitBufferOverflow 0 0 normal 1 overflow Soft receiveBufferOverflow 1 0 normal 1 overflow Soft framingError 2 0 normal 1 error Soft breakDetect 3 0 normal 1 error Soft parityError 4 0 normal 1 error Soft Reserved 5 15 N A 9 9 softwareBIT Field The softwareBIT field contains flags that indicate various types of software errors Each type has an associated message with low level error signals The softwareError flag in the BITstatus field is the bit wise OR of this softwareBIT field softwareBIT Field Bits Meaning Category algorithmError 0 0 normal 1 error S
125. ritten numFields 2 Field U2 The last field ID written 1 8 9 Read Fields Command Read Fields RF 0x5246 0x5555 0x5246 1 numFields 2 RF payload lt CRC U2 gt This command allows the user to read the default power up configuration fields from the EEPROM NumFields is the number of fields to read The field0 field etc are the field IDs to read RF may be used to read configuration and calibration fields from the EEPROM If at least one field is successfully read the unit will respond with a read fields response containing the field IDs and data from the successfully read fields If any field is unable to be read the unit will respond with an error response Note that both a read fields and an error response may be received as a result of a read fields command RF Payload Contents Byte Offset Name Format Scaling Units Description 0 numFields U1 The number of fields to read 1 fieldO U2 The first field ID to read 3 field1 U2 The second field ID to read x ks U2 More field IDs to read numFields 2 1 Field U2 The last field ID to read 8 10 Read Fields Response Read Fields RF 0x5246 Packet Length Payload 0x5555 0x5246 1 numFields 4 HF payload CRC 02 gt The unit will send this packet in response to a read fields request if the command has completed without errors
126. rrection Module In general rate sensors and accelerometers suffer from bias drift misalignment errors acceleration errors g sensitivity nonlinearity square terms and scale factor errors The largest error in the orientation propagation is associated with the rate sensor bias terms The Extended Kalman Filter EKF module provides an on the fly calibration for drift errors including the rate sensor bias by providing corrections to the Integration to Orientation block and a characterization of the gyro bias state In the AHRS440 the internally computed gravity reference vector and the distortion corrected magnetic field vector provide an attitude and a heading reference measurement for the EKF when the AHRS440 is in quasi static motion to correct roll pitch and heading angle drift and to estimate the X Y and Z gyro rate bias The AHRS440 adaptively tunes the EKF feedback gains in order to best balance the bias estimation and attitude correction with distortion free performance during dynamics when the object is accelerating either linearly speed changes or centripetally false gravity forces from turns Because centripetal and other dynamic accelerations are often associated with yaw rate the AHRS440 maintains a low passed filtered yaw rate signal and compares it to the turnSwitch threshold field user adjustable When the user platform with the AHRS440 attached exceeds the turnSwitch threshold yaw rate the AHRS440 lowers the feedback gains fr
127. rsed info when return value is 1 packetCRC 0 packet Lype dataLength numToPop t 1 break numToPop 0 counter 0 Crossb w Doc 7430 0131 01 Rev E Page 71 440 Series User s Manual if Size queue ptr lt 0 header was not found return 0 make sure we can read through minimum length packet if Size queue_ptr lt 7 return 0 get data length 5th byte of packet dataLength peekByte queue ptr 4 make sure we can read through entire packet if Size queue ptr lt 7 dataLength return 0 check CRC myCRC calcCRC queue ptr 2 dataLengtht 3 packetCRC peekWord queue ptr dataLength 5 if myCRC packetCRC bad CRC on packet remove the bad packet from the queue and return Pop queue ptr dataLength 7 return 0 fill out result of parsing in structure result gt packet_type peekWord queue ptr 2 result gt length peekByte queue ptr 4 result crc packetCRC for counter 0 counter lt result length counter result gt data counter peekByte queue ptr 5tcounter Pop queue ptr dataLength 7 return 1 BR KK RR KK RR A k k k k k k k k k k k k k k k k k FUNCTION calcCRC calculates a 2 byte CRC on serial data using CRC CCITT 16 bit standard maintained by the ITU International Telecommunications Union ARGUMENTS queue ptr is pointer to queue holding area to be CRCed Star
128. runs on a 150MHz 32 bit DSP Digital Signal Processor that has approximately four times the computational power of Crossbow s earlier generation Inertial Systems Another unique feature of the 440 Series is the extensive field configurability of the units This field configurability allows the 440 Series of Inertial Systems to satisfy a wide range of applications and performance requirements with a single mass produced hardware platform The basic configurability includes parameters such as baud rate packet type and update rate and the advanced configurability includes the defining of custom axes and how the sensor feedback is utilized in the Kalman filter during the navigation process The 440 Series is packaged in a fully sealed lightweight housing which provides EMI vibration and moisture resistance to levels consistent with most land marine and airborne environments The 440 Series utilizes an RS 232 serial link for data communication and each data transmission includes a BIT Built In Test message providing system health status The 440 Series is supported by Crossbow s NAV VIEW 2 X a powerful PC based operating tool that provides complete field configuration diagnostics charting of sensor performance and data logging with playback Doc 7430 0131 01 Rev E Page 2 440 Series User s Manual Crossb w 1 3 Summary of Major Changes from the 300 400 Series and the 420 Series 1 3 1 Mechanical Size and Footprint The mechanical fo
129. s allows the Kalman Filter to estimate the roll and pitch rate sensor bias prior to entering the free gyro mode Upon exiting the free gyro mode OFF one of two behaviors will occur 1 If the NAV440 has been in freely integrate mode for less than sixty seconds the algorithm will resume operation at normal gain settings 2 If the NA V440 has been in freely integrate mode for greater than sixty seconds the algorithm will force a reset and reinitialize with high gains automatically Use GPS ON The Use GPS setting allows users to turn on and off the GPS feedback The default setting is ON for the 440 When Use GPS is turned OFF the NAV440 s behavior will revert to that of an AHRS440 See the AHRS440 Theory of Operation for detailed description Stationary Yaw Lock OFF This setting defaults to OFF on the NAV440 and it is recommended to be OFF for the NAV440 The stationary yaw lock setting is only recommended for consideration when the NAV440 is operating with GPS Use GPS ON and WITHOUT magnetometer feedback Use Mags OFF Stationary yaw lock may be appropriate if the user platform is a wheeled land vehicle Use Mags ON The Use Mags setting allows users to turn on and off the magnetometer feedback for yaw heading stabilization The default setting is ON for the NAV440 When Use Mags is turned ON the NAV440 uses the magnetic field sensor readings to stabilize the drift in yaw and it slaves the
130. s has shown superior performance when compared to the equivalent model of 400 and 420 Series reducing attitude estimation errors in half during certain critical dynamic maneuvers without the use of GPS aiding With GPS aiding in the NA V440 attitude estimation is improved by an order of magnitude compared with 400 series products Recommended product configuration settings are discussed in Section 5 and theory of operation is discussed in Section 4 Doc 7430 0131 01 Rev E Page 3 440 Series User s Manual Crossb w 2 Connections 2 1 Connections The 440 Series has a male DB 15 connector The signals are as shown in Table 3 15 Pin D Connector Male Pinout 0 Table 3 Connector Pin Assignments 3 5 Signal RS 232 Transmit Data A Port RS 232 Receive Data A Port Positive Power Input Vcc Power Ground Chassis Ground Factory use only RS 232 GPS Tx B Port RS 232 GPS Rx B Port Signal Ground 1 PPS OUT 1 PPS IN IMU VG AHRS only NC factory use only O O N EN E Hardware Error m NC factory use only NC factory use only 2 2 Cable The user must provide a shielded cable with the shield connected to the I O connector shell in order to provide the required EMI protection The cable
131. shown in the block diagram Figure 9 the NA V440 and AHRS440 include an internal 3 axis magnetometer and the NA V440 includes an internal WAAS capable GPS receiver In addition the AHRS440 and VG440 can accept input from external GPS sources as noted in Chapter 2 of this manual Docit 7430 0131 01 Rev E Page 17 440 Series User s Manual Crossb w Figure 9 440 Series Hardware Block Diagram System Digital Outputs and Inputs X Y Z XY Z High Speed Pins 1 2 Gyros Programmable Sampling amp RS 232 MEMS Low Pass Filters DSP A Port X Y Z XYZ Sensor Crossbow Serial Protocol X Y Z Acceleration m Roll Pitch Yaw Rate X Y Z Magnetic Fields NAV AHRS only Accelerometers Programmable Compensation m Roll Pitch Yaw Angle MEMS Low Pass Filter Position Velocity NAV only Navigation amp m Euilt In Test Attitude Sensor RS 232 B Port Temperatures Kalman Filter Optional use port Pins 7 8 External GPS Input VG AHRS 6 amp DOFSensor i Cluster BEB 2 Rs 232 Internal GPS Output GPS Receiver NAV Magnetometer B Port e n on NAV only GPS Antenna m NAV only Figure 10 shows the software block diagram 6 DOF inertial sensor cluster data is fed into a high speed 100Hz signal processing chain These 6 DOF si
132. t Doc 7430 0131 01 Rev E Page 14 440 Series User s Manual Crossb w The AHRS and NA V440 products account for the extra magnetic field by making a series of measurements and using these measurements to model the hard iron and soft iron environment in your system using a two dimensional algorithm The AHRS and NA V440 products will calculate the hard iron magnetic fields and soft iron corrections and store these as calibration constants in the EEPROM The Mag Alignment Procedure should always be performed with the AHRS or NAV440 product installed in the user system If you perform the calibration process with the 440 Series product by itself you will not be correcting for the magnetism in the user system If you then install the 440 Series product in the system i e a vehicle and the vehicle is magnetic you will still see errors arising from the magnetism of the vehicle 3 12 2 Mag Alignment Procedure Using NAV VIEW 2 X The Mag Alignment Procedure using NAV VIEW 2 X can be performed using the following steps below 1 Select Mag Alignment from the Configuration drop down menu at the top 2 Ifyou can complete your 360 degree turn within 120 seconds select the Auto Terminate box 3 Select the Start button to begin the MagAlign Procedure and follow the instructions at the bottom of the screen as shown in the figure below Magnetometer Alignment Current Settings X Hard Iron Offset Y Hard Iron Offset
133. t Scaling Units Description Offset 0 xAccel 12 20 2 16 0 X accelerometer 2 yAccel l2 20 2 16 g Y accelerometer 4 zAccel 12 20 2 16 g Z accelerometer 6 xRate 12 7 pi 2 16 rad s X angular rate 12602716 sec 8 yRate 12 7 pi 2 16 rad s Y angular rate 12602716 sec 10 zRate 12 7 pi 2 16 rad s Z angular rate 12602716 sec Doc 7430 0131 01 Rev E Page 47 440 Series User s Manual Crossb w 12 xRateTemp 12 200 2 16 deg C X rate temperature 14 yRateTemp 12 200 2 16 deg C Y rate temperature 16 zRateTemp 2 200 2 16 deg Z rate temperature 18 boardTemp 2 200 2 16 deg CPU board temperature 20 Counter U2 packets Output packet counter 22 BITstatus U2 Master BIT and Status 7 4 3 Scaled Sensor Data Packet 2 Delta Theta Delta V Scaled Sensor Data S2 0x5332 Packet Length Payload 0 5555 0x5332 lt S2 payload gt CRC U2 gt This packet contains scaled sensor data in the traditional delta theta and delta velocity format with integration time equivalent to the packet rate Changes in body axis angles and velocities are accumulated during the interval between successive packets as determined by the packet rate Polled requests for this packet will produce values accumulated since the last poll request and thus are subject to overflow data type wrap around Data involving angular measurements include the factor
134. t is not occupied by another device 4 Under the View menu you have several choices of data presentation Graph display is the default setting and will provide a real time graph of all the 440 Series data The remaining choices will be discussed in the following pages 3 4 Data Recording NAV VIEW 2 X allows the user to log data to a text file txt using the simple interface at the top of the screen Customers can now tailor the type of data rate of logging and can even establish predetermined recording lengths To begin logging data follow the steps below 1 Locate the icon at the top of the page or select Log to File from the File drop down menu 2 The following menu will appear Log to File LogFile I Browse Log Type Logging Rate Enginerring Data Fractional Rate Full Sample Rate Hex Data 4 2 Sample Rate Raw Packets Hex C 4 4 Sample Rate 1 10 Sample Rate Test Duration 4 100 Sample Rate Days 0 Hours 0 i Samples Second hoa Minutes 0 Seconds Sample h 4 Seconds 10 Cancel 3 Select the Browse box to enter the file name and location that you wish to save your data to Select the type of data you wish to record Engineering Data records the converted values provided from the system in engineering units Hex Data provides the raw hex values separated into columns displaying the value and the Raw Packets will simp
135. t signals which has been enabled See Section 9 Advanced BIT for details on configuring the masterStatus flags Table 12 shows the BIT definition and default settings for BIT programmable alerts in the AHRS440 Table 12 AHRS440 Default BIT Status Definitions BITstatus Field Bits Meaning Category masterFail 0 0 normal 1 fatal error has occurred BIT HardwareError 1 0 normal 1 internal hardware error BIT comError 2 0 normal 1 communication error BIT Doc 7430 0131 01 Rev E Page 29 440 Series User s Manual Crossb w softwareError 3 0 normal 1 internal software error or BIT magAlignOutofBounds Reserved 4 7 masterStatus 8 0 nominal 1 one or more status alerts Status hardwareStatus 9 Disabled Status comStatus 10 0 nominal 1 No External GPS Comm Status softwareStatus 11 0 nominal 1 Algorithm Initialization or Status High Gain sensorStatus 12 0 nominal 1 Sensor Over Range Status Reserved 13 15 N A The AHRS440 also allows a user to configure the Status byte within the BIT message To configure the word select the BIT Configuration tab from the Unit Configuration menu The dialog box allows selection of which status types to enable hardware software sensor comm Like the VG440 and IMU440 Crossbow recommends for the vast majority of users that the default Status byte for the AHRS440 is sufficient For users who w
136. tIndex is offset into buffer where to begin CRC calculation num is offset into buffer where to stop CRC calculation RETURNS 2 byte CRC Crossbgw Doc 7430 0131 01 Rev E Page 72 440 Series User s Manual Crossbgw eR A AR A RRA unsigned short calcCRC QUEUE TYPE queue ptr unsigned int startIndex unsigned int num unsigned int i 0 3 0 unsigned short crc 0x1DOF non augmented inital value equivalent to augmented initial value OxFFFF for i20 i num 1 1 crc peekByte queue ptr startIndex i lt lt 8 for j 0 j 8 j 1 if crc amp 0x8000 cre cre lt lt 1 0 1021 else crc crc 1 return crc BKK RRR A RK k k RR FUNCTION Initialize initialize the queue ARGUMENTS queue ptr is pointer to the queue KKK KK k k k k k k k k k k k k k k k k k k k k k k k k k k k void Initialize QUEUE TYPE queue ptr queue ptr count 0 queue ptr front 0 queue ptr gt rear 1 BRK k K k K K k K k A K K k K K K k K K K K KOK K K K A K K K K K KOK KOK K KOK K K K A KOK K KOK KOK K K K KOK KOK K KOK k k k k k k k k k k FUNCTION AddQueue add item in front of queue ARGUMENTS item holds item to be added to queue d queue ptr is pointer to the queue RETURNS returns 0 if queue is full 1 if successful A A ok int AddQueue char item QUEUE TYPE queue ptr int retval 0 if queue_ptr gt
137. te bee HP Or ces 54 8 3 Analog Filter Clocks 152 3 sa 5 rore ter ee e T m 54 8 4 Orientation Eields eot roasted anite atau 55 8 5 User Behavior S witehes 5 sion denn ma I im hae 56 8 6 Soft Iron Val es 5235 su uma tet end enit RU men 57 8 7 Heading Track Offset eei teo bee eo tee bad 57 8 8 Commands to Program Configuration ssns ieie E a p aeae e raen a ai a eae eaea oi Saione 57 8 8 1 Waite Fields Command ade e ite e nte a Sa acd ie it 57 8 8 2 Command EGREDIENS Sas 58 8 9 Read Fields Command Ai aya ip benedi bU 59 8 10 Read Fields iie I REPERI n Re deo ea 59 8 11 Get Fields Command eee tbe tested ette to dec dre deret ipei es 59 8 12 Response in UR E HERE OP ac Rp Rep a ny RETE Rate 60 9 xAdvanced ii ine cet Sel uuu iets a Cag te a Go cecil A a aspa Aa uk e 61 9 1 Built In Status Fields reet e ER ERR ETE EGER TREE 61 9 2 Master and Status BITstatus Field n nn susunan 62 9 3 rJ EK 63 9 4 hardwarePowerBLT Field e I be 63 9 5 hardwareEnvironmentalBIT Field s ee eet ro e a i e hes i RC EO e a REGE 63 9 6 combBIT Eiel
138. the attitude and heading reference functionality that the AHRS440 replicates by providing dynamic heading roll and pitch measurements in addition to the VG and IMU data The dynamic heading measurement is stabilized using the 3 axis magnetometer as a magnetic north reference As in the VG440 the dynamic roll and pitch measurements are stabilized using the accelerometers as a long term gravity reference Unlike the AHRS400 and earlier Crossbow AHRS Series products the AHRS440 can be configured to turn on and off the magnetic reference for user defined periods of time see Section 8 Advanced Commands In addition the AHRS440 can accept external GPS data refer to the NAV440 section for details for improved performance At a fixed 100Hz rate the AHRS440 continuously maintains the digital IMU data as well as the dynamic roll pitch and heading As showing in Figure 10 after the Sensor Calibration Block the IMU data is passed to the Integration to Orientation block The Integration to Orientation block integrates body frame sensed angular rate to orientation at a fixed 100 times per second within all of the 440 Series products For improved accuracy and to avoid singularities when dealing with the cosine rotation matrix a quaternion formulation is used in the algorithm to provide attitude propagation As also shown in the software block diagram the Integration to Orientation block receives drift corrections from the Extended Kalman Filter or Drift Co
139. tion For example refer to the application note on Crossbow website http www xbow com Support appnotes htm 4 1 1 Advanced Settings The 440 Series Inertial Systems have a number of advanced settings that can be changed The specific settings available vary from unit to unit and a detailed description of each unit IMU VG AHRS and NAV is found in the subsequent sections of this manual All units support baud rate power up output packet type output rate sensor low pass filtering and custom axes configuration The units can be configured using NAV VIEW 2 X as described in Section 3 and also directly with serial commands as described in Sections 6 9 4 2 IMU440 Theory of Operation The product name IMU440 stands for Inertial Measurement Unit 440 and the name is indicative of the inertial measurement unit functionality that the IMU440 provides by providing inertial rate and acceleration data in 6 DOF six degrees of freedom The IMU440 signal processing chain consists of the 6 DOF sensor cluster programmable low pass filters analog to digital conversion and the DSP signal processor for sensor error compensation The IMU440 as with other 440 Series variants has an RS 232 serial communications link After passing thru a digitally controlled programmable analog low pass filter the rate and acceleration analog sensor signals are sampled and converted to digital data at 1 kHz The sensor data is filtered and down sampled to 100Hz by the
140. tion phase lasts approximately 60 seconds and the initialization phase can be monitored in the softwareStatus BIT transmitted by default in each measurement packet After the initialization phase the NA V440 operates with lower levels of feedback also referred to as EKF gain from the GPS accelerometers and magnetometers Digital data is output over the RS 232 serial link at a selectable fixed rate 100 50 25 20 10 5 or 2 Hz or on as requested basis using the GP Get Packet command In addition to the angle mode packets of the AHRS440 and scaled sensor packets of the IMU440 the NA V440 has additional output measurement packets including the default 1 Navigation Packet which outputs the Latitude Longitude Altitude X Y Z velocities accelerations and roll angle pitch angle yaw angle and digital IMU data See Section 6 and 7 of the manual for full packet descriptions IMPORTANT For proper operation the NA V440 relies on magnetic field readings from its internal 3 axis magnetometer NA V440 must be installed correctly and calibrated for hard iron and soft iron effects to avoid any system performance degradation See section 4 4 1 for information and tips regarding installation and calibration and why magnetic calibration is necessary Please review this section of the manual before proceeding to use the NAV440 gt IMPORTANT For optimal performance the NA V440 utilizes GPS readings from its internal GPS receiver
141. ualize the mode of operation See Section 8 4 Orientation Field settings for the twenty four possible orientation settings The default setting points the connector AFT Analog 5Hz The low pass filters are set to a default of 5Hz for the accelerometers and 20 Hz Filter accels for the angular rate sensors There is one filter setting for all three angular rate Clocks 1 2 20Hz sensors There are two settings for the accelerometers one for the X and Y axes amp 3 rates and a separate setting for the Z axis The reason for a separate setting in the Z axis is that in many installations the Z axis vibration level is much higher than in the X and Y axes and it can prove helpful to filter the Z axis at a lower cutoff than the X and Y axes Freely OFF Freely Integrate setting allows a user to turn the VG440 into a free gyro In Integrate free gyro mode the roll pitch and yaw are computed exclusively from angular rate with no kalman filter based corrections of roll pitch or yaw When turned on there is no coupling of acceleration based signals into the roll and pitch As a result the roll pitch and yaw outputs will drift roughly linearly with time due to sensor bias For best performance the Freely Integrate mode should be used after the algorithm has initialized This allows the Kalman Filter to estimate the roll and pitch rate sensor bias prior to entering the free gyro mode Upon exiting the free gyro mode OFF o
142. ular rate to orientation at a fixed 100 times per second within all of the 440 Series products except IMU440 For improved accuracy and to avoid singularities when dealing with the cosine rotation matrix a quaternion formulation is used in the algorithm to provide attitude propagation Following the integration to orientation block the body frame accelerometer signals are rotated into the NED level frame and are integrated to velocity At this point the data is blended with GPS position data and output as a complete navigation solution As shown in Figure 10 the Integration to Orientation and the Integration to Velocity signal processing blocks receive drift corrections from the Extended Kalman Filter EKF drift correction module The drift correction module uses data from the aiding sensors when they are available to correct the errors in the velocity attitude and heading outputs Additionally when aiding sensors are available corrections to the rate gyro and accelerometers are performed The NAV440 blends GPS derived heading and accelerometer measurements into the EKF update depending on the health and status of the associated sensors If the GPS link is lost or poor the Kalman Filter solution stops tracking accelerometer bias but the algorithm continues to apply gyro bias correction and provides stabilized angle outputs The EKF tracking states are reduced to angles and gyro bias only The accelerometers will continue to integrate velocity
143. ult coordinate system settings of the 440 Series when it leaves the factory With the 440 Series product connector facing you and the mounting plate down the axes are defined as follows Figure 12 440 Series Default Coordinate System X axis from face with connector through the 440 roll unit Y axis along the face with connector from left to right pion Z axis along the face with the connector from top to yaw bottom The axes form an orthogonal SAE right handed coordinate system Acceleration is positive when it is oriented towards the positive side of the coordinate axis For example with a 440 Series product sitting on a level table it will measure zero g along the x and y axes and 1 g along the z axis Normal Force acceleration is directed upward and thus will be defined as negative for the 440 Series z axis The angular rate sensors are aligned with these same axes The rate sensors measure angular rotation rate around a given axis The rate measurements are labeled by the appropriate axis The direction of a positive rotation is defined by the right hand rule With the thumb of your right hand pointing along the axis in a positive direction your fingers curl around in the positive rotation Doc 7430 0131 01 Rev E Page 20 440 Series User s Manual Crossb w direction For example if the 440 Series product is sitting on a level surface and you rotate it clockwise on that surface this will be a positive rotation
144. urement packet In addition there is a diagnostic packet 0 that can be requested via the Get Packet command which contains a complete set of status for each hardware and software subsystem in the IMU440 See Sections 6 8 Programming Guide for details on the TO packet The BIT word which is contained within each measurement packet is detailed below The LSB Least Significant Bit is the Error byte and the MSB Most Significant Bit is a Status byte with programmable alerts Internal health and status are monitored and communicated in both hardware and software The ultimate indication of a fatal problem is the masterFail flag The masterStatus flag is a configurable indication that can be modified by the user This flag is asserted as a result of any asserted alert signals which have been enabled See Advanced BIT Section 9 for details regarding the configuration of the masterStatus flags Table 8 shows the BIT definition and default settings for BIT programmable alerts in the IMU440 Table 8 IMU440 Default BIT Status Definition BITstatus Field Bits Meaning Category masterFail 0 0 normal 1 fatal error has occurred BIT Doc 7430 0131 01 Rev E Page 22 440 Series User s Manual Crossb w HardwareError 1 0 normal 1 internal hardware error BIT comError 2 0 normal 1 communication error BIT softwareError 3 0 normal 1 internal software error BIT
145. us Field Bits Meaning algorithmInit 0 0 normal 1 the algorithm is in initialization mode highGain 1 0 low gain mode 1 high gain mode attitudeOnlyAlgorithm 2 0 navigation state tracking attitude only state tracking turnSwitch 3 0 off 1 yaw rate greater than turnSwitch Doc 7430 0131 01 Rev E Page 65 440 Series User s Manual Crossb w threshold Reserved 4 15 N A 9 15 sensorStatus Field The sensorStatus field contains flags that indicate various internal sensor conditions and alerts that are not errors or problems The sensorStatus flag in the BITstatus field is the bit wise OR of the logical AND of the sensorStatus field and the sensorStatusEnable field The sensorStatusEnable field is a bit mask that allows the user to select items of interest that will logically flow up to the masterStatus flag sensorStatus Field Bits Meaning overRange 0 0 not asserted 1 asserted Reserved 1 15 N A 9 16 Configuring the masterStatus The masterStatus byte and its associated programmable alerts are configured using the Read Field and Write Field command as described in Section 8 Advanced Commands The Table below shows the definition of the bit mask for configuring the status signals configuration fields field ID Valid Values Description hardwareStatusEnable Bit mask of enabled hardware status 0x0010 An signals comStatusEnable Bit mask of enabled communication 0x0011 Any status signals softw
146. yaw to the compass reading provided from the magnetic field sensor readings When UseMags is turned OFF the heading yaw angle measurement of the NAV440 will be slaved to the GPS heading if GPS is available otherwise the heading will drift feely The reason for this setting is to give the user an ability to turn off the magnetometer stabilization when severe magnetic distortion may be occurring This setting is desirable when the user vehicle temporarily moves in close proximity to a large ferrous object When the Use Mags switch is turned from OFF to ON the NAV440 will reinitialize the yaw heading angle with the compass reading provided from the magnetic field sensor readings Restart On Over Range OFF This setting forces an algorithm reset when a sensor over range occurs i e rotational rate on any of the three axes exceeds the maximum range The default setting is OFF for the NAV440 Algorithm reset returns the NAV440 to a high gain state where the NAV440 rapidly estimates the gyro bias and uses the accelerometer feedback heavily This setting is recommended when the source of over range is likely to be sustained and potentially much greater than the rate sensor operating limit Large and sustained angular rate over ranges result in unrecoverable errors in roll and pitch outputs An unrecoverable error is one where can not stabilize the resulting roll and pitch reading If the over ranges are expected to be of

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