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1. 69 Figure 56 Protected Digital lO nana 69 Fig re57 T of 2 power outputs i dene i EET aat 70 Figure 5S FLASELEMOeITIOTV he eroe ee eee 71 Figure 59 User n Uto e bese pan Eee ee oe Eco vae eae Ue eiua ee dae e EE Teneo e Eee aeo 73 Figure 60 RS 485 1 3 transceivers 74 Figure 61 Autoswitch Power Mux 3 3V LDO Regulator 75 Fig re 62 OS d Tool 77 63 e ante neenon IS 80 Figure 64 Packaged bb Map db octo 80 Figure 65 Visual representation of the function timings 84 Figure 66 Unipolar 4 Quadrant PWMs Texas Instruments 86 Figure 67 FlexSEA Execute Motor Control PSoC Diagram 89 Figure 68 PWM signals rotating BLDC motor 89 Figure 69 Load test bench equivalent to a stalled Maxon brushless motor
2. 100 qd CF t reWoerlexzua s uu nn ivo he aai Gd 102 5 5 cuore katama mu eee ta n tte dee sedet eo ied be secrete ut Su 104 SL FlexSEA EX cut ev aei tipp ipaq usni T BIRD cO PUE osa 104 5 1 1 Motor Half Bridge Load 104 5 1 2 Strain Gauge Amplifier Force Calibration 106 5 1 3 Power Supplies tte eR ISP RN DIRE ISIN MIU 106 5 1 3 1 Preliminary q alifiCatiOrty u aus umu u S ennemis 106 5432 SMPS Load Testihg ee etse utet qa Stet 107 51 3 3 SV SMPS Load Testigo reuse tM uenia ima amp tpa e ig 109 5 1 Safety Eeatul 65 iere rH CRETA dee TR u SS k YI eda 110 5 14 Watchdog tete e 110 5 1 4 2 asas essa 112 5 1 4 3 VB Voltage Range ua L u a 113 5 1 4 4 Disconnected Battery 114 5 2 deze encoded amu a Ghee dawns 115 5 2 1 Level shifting FlexSEA Plan and FlexSEA Manage Interface 115 5 2 1 1 Analog Inputs With Programmable Features 116 5 2 2 Power Multiplexer and Linear Regulator Load Test
3. 118 5 3 System Benchmark Snerre ieaie usan ma aap aqyapa 120 5 3 1 SPI Frequency and Data Gb EIU 120 5 3 2 Communication Plan amp EXeCUte age 121 5 3 3 Communication Manage amp Execute 123 5 3 4 bEVMRor rip 125 6 JApplicatlOn test CASES cao n ted dte iva Gatos pd bedeutet 128 6 1 Clutched Series Elastic CSEA Knee ennemis 128 6 2 AUTONOMOUS Exoskeleton 129 7 Results u 130 7 1 Evaluation Criteria legacy 130 4 Q EVAl Uati Criteria az n A ua a a a a a at auo edt 130 Peo RESUMES PE 132 82 i Man unas Qs s S 134 e 135 10 Q qua a buy ak Qaqa kaqka 137 10 1 G SSapyu s an ya u Q ay astana 137 10 2 Execute esos em nti ede Rte Medi m a tees alten aypaq 139 10 3 Manage Schematic Sete OD EIS WI 153 10 4 Sa rot pi deba diste da ben NEMUS SE Rete G aad d 165 TOSS User soo dei ead empaque dep Ula n MA 167 Table o
4. 24 3 Hardware designs s uuu a EVER E e ees 27 3 1 SRIexSEASEXOCUEGO n lb Rute bees ach u dun 27 3 1 1 s su rtr UG Aere 29 3 1 1 1 Microcontroller selectiofiaa teer te pene te da eqs toon etie 29 3 1 1 2 Programmable System on Chip PSoC 31 3 1 2 PSOGA Safety Co ProCessOr iuo tie eterne Pete avia catus os 32 3 1 3 Brushless OR D eue dri a bee d a boda 34 3 1 3 1 Half bridges i ceto itte teni 36 3 1 3 2 Motor current saa sn setatis 39 3 1 3 3 Shorted leads protection sacs ssie S s abya assia iaia 40 Beli estan be 43 3 1 5 Strain Gauge Amplifier i u mu u lu u uu uui 45 u us 48 3 1 6 1 P MOSFET power dissipation 49 3 1 6 2 level Shifting notitia een a e 50 3 1 7 50 3 1 8 lO ProtectioBS au nun oi ette e ete mia Sa rele Eie ERU di eere eid ete 51 3 1 9 User Intel ettet bcp Mod 53 221210 rPOWSF SUDIDIIBS 12 20 on Cer aret re ole ci d matti
5. i Ath eel de Doct Had uoce OR 109 Figure 84 Load testing constant current a 110 Figure 85 Watchdog Clock Pulse Width Measurement 111 Figure 86 Over temperature detection a nee 112 Figure 87 VB Voltage in Range detection code 114 Figure 88 Disconnected Battery Detection Code 115 Figure 89 SPI signals Plan side of the level translator 116 Figure 90 Testing the variable frequency filter 117 Figure 91 Testing the programmable gain 117 Figure 92 Load testing ua repe ua ete ina aasan a due UN Nee ERE Rer ut OREMUS 119 Figure 93 Automatic switching of the input power source 120 Figure 94 SPI Data Rate 83ns 12Mbits s eit eda ert a e etras 121 Figure 95 Communication Plan amp Execute 2 packets 122 Figure 96 Communication Plan amp Exe
6. control 7 0 0 2 55ms Figure 85 Watchdog Clock Pulse Width Measurement The Edge Detector detects both edges and is synchronized by a 100kHz clock Control_Reg_1 is software controlled It is programmed with a value of 150 to measure a maximum pulse width of 1 5ms 667 2 Special test code was used on the PSoC 5 to test the limit void wdclk test blocking void uint8 toggle wdclk 0 while 1 toggle wdclk 1 WDCLK Write toggle wdclk CyDelayUs 1200 The CyDelayUs function is imprecise the actual delay was always longer than programmed It was increased up to the point where the software would detect a problem programmed value of 1200ys measured value of 1485us During normal operation the worst case WDCLK period measured was 10 5 Every time the PSoC 5 is being programmed the PSoC 4 goes into error mode confirming that non functional software will trigger a safety mechanism 111 5 1 4 2 Over temperature Test code Test code temperatur if err temp T NORMAL ELED Write 0 lse if err temp T WARNING togg eled 1 ELED Write togg eled ELED Write 1 T WARNING is 75 and T ERROR is 80 Heat was applied directly on the temperature sensor with a Weller 160W soldering iron ELED will be low when the temperature is under the 2 thresholds alternating between digital values of 0 and 1 between 75 and 80
7. B Main Debugger e startup S Source 1 Common gt E C C Application GDB Setup Ei c Ce Attach to Application GDB Command Debug Configurations E Postmortem Debugger arm none eabi gdb Sy v C C Remote Application E manage Debug 1 Remote Target Y E GDB Hardware Debugging Use remote target Spenco Debug Device Generic TCP IP E OpenOCD Debugging El GDB SEGGER Link Debugging Host name or IP address localhost gt Launch Group Port number 3333 Force thread list update on suspend l Using GDB DSF Hardware Debugging Launcher Select other Filter matched 12 of 12 items 9ging M l 178 Debug Configurations Create manage and run configu x BP Name OpenOCD Debug J B Main 9 Debugger gt startup 8 Source Common gt S C C Application Attach to Application Postmortem Debugger v E C C Remote Application manage Debug 1 Y E GDB Hardware Debugging E OpenOCD Debug OpenOCD Debugging E GDB SEGGER J Link Debugging gt Launch Group Filter matched 12 of 12 items o Initialization Commands 8 Reset and Delay seconds 3 Halt monitor halt reset Load Image and Symbols Load image Use project binary manage elf D Use file Image offset hex Load symbols Use project binary manage elF D Use file
8. numb tx cmd special l FLEXSEA EXECUTE 1 payload str PAYLOAD BUF LEN KEEP 0 KEEP O 77 0 numb comm gen str payload str PAYLOAD BUF LEN numb COMM STR BUF LEN flexsea spi transmit numb comm str 0 Can decode what we received tmp decode spi rx lines good tmp Log to file 125 t time NULL tm localtime amp t fprintf logfile d d 1i 1i 1i 1i i i i n tm tm min N tm tm_sec execl encoder execl current N execl imu x execl imu y execl imu z execl strain execl analog 0 Delay 500us usleep 500 Close log file fclose logfile printf Nn i lines i with valid data n lines good t time NULL tm localtime amp t printf n i lines logged n lines printf Log file closed d d d d d d Exiting n n n tm tm year 1900 tm tm mon 1 tm tm mday tm tm hour tm tm min tm tm sec When the CMD_SPECIAL_1 command is received it stores 16 bytes exec ptr imu x intl6 t BYTES UINT16 buf CP DATA1 0 buf CP DATA1 1 exec s ptr imu y intl6 t BYTES UINT16 buf CP DATA1 42 buf CP DATA1 3 exec ptr gt imu z intl6 t BYTES UINT16 buf CP_DATA1 4 buf CP DATA1 5 exec s ptr gt s
9. 06 5 2SA1774G __ R48 3 99 Qu SDMA0E20LS 7 F GND GND GND ge x 2 5 g z 3 55 8 010 CPC3703CTR CPC3703CTR CPC3703CTR D24 V4PANSO 145 o 2 8 g E ES 4 Oy az o GND GND GND GND 2 Biomechatronics Execute Shorted Leads 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 l media Date 2015 03 05 Time 12 28 59 Sheet of USA lab File BIOM FLEXSEA EXECUTE 0 1 Shorted Leads SchDoc 1 2 3 4 VB n 1 AWGI6 TH DS p SMAJ33A 1 AWG16_TH GND GND LM25011 TPS62163 BIOM FLEXSEA EXECUTE 0 1 LM25011 DCDC SchDoc BIOM FLEXSEA EXECUTE 0 1 TPS62163 DCDC SchDoc VB VB VB VB VB VB Pe REL ie Ag gt eg e R nal a L L L Xx GND GND GND GND GND GND 3 C66 i NB 42 10k VG 5V 8 9 4 10k 7 5k k t t 5 5 al e a a 5 5 GND GND GND UI2 1700 33 VIN VOUT 2 67 di luF Gp we LNJ347W83RA DI NB VB VB VB VB VB VB GND GND GND GND GND GND GND Execute Power Supplies Biomechatronics Size Letter Number Revision Date 2015 03 05 T
10. 55 3 1 10 1 Brown out protections 55 3 1 10 2 Low voltage power supplies 56 3 124013 2EM25011 TOV SOOM 556 Urn ricevi e Lot RU a 58 3 1 10 4 T9862163 SV 500MA a Ee ee Pu hen eat d ia 59 3 1 11 Future Work and Circuit Modifications secet o am eO i CU PREISE 60 3 27 FlexSEA ManaBge iio cire n EDI eerie e E ens 61 3 2 1 Microcontrollefy E ETT OE 63 3 2 2 Interface to Plaas uu uu saa as 64 3 2 3 Inputs and Outputs D a NUM 67 3 2 3 1 Analog Inputs with Programmable Features 67 3 2 3 2 Digital Inputs amp Outputs eene eden n eere 69 3 2 3 3 Power QUtpDUts ss Su eret e Roe Sua 70 32 O eroi e uM cutus d neni a 71 222252 PREAS C 71 3 2 6 User Interface 73 3 27 CRSA Ba ais u as aka aaa E 74 3 2 8 Q u a Su QQ tee oe nee 75 3 2 9 Future Work and Circuit Modifications 76 Software Desig Merican aeee eei ln n q edet getestet 77 4 1
11. 15V 52 arn 10nF GND GND GND GND 2 2 Biomechatronics Tite Execute Strain Amplifier MIT Media Lab E14 274 75 Amherst Street mit fe Size Letter Number Revision Cambridge MA 02139 media Date 2015 03 05 Time 12 28 59 Sheet of US4 lab File BIOM FLEXSEA EXECUTE 0 1 Strain Gauge SchDoc 2 3 5 33V3 3V3 33V3 33V3 33V3 17 L ie a B 3k 100nF 100F lt SDA 3V3 4 P o 2 SCL 3V3 SCLSCIK AUXDA iwa a gt E so c R20 DI7 NC 5 1 3k LNJ347W83RA NC 6 14 5 NC His 2 NC 75 NM GND E MPU 6500 61 100nF D6 GND GND TPD2EUSB30DRTR mam v3 150 66 67 47 MS SCLI 2 sci A SDAI SDA2 z 2 g amp z 2 Y Y 7 Biomechatronics Execute UI amp IMU NDA ALOR S BRE 3 75 Amherst Street mit X X Size Letter Number Revision Cambridge MA 02139 l media Date 2015 03 05 Time 12 28 59 Sheet of USA lab File BIOM FLEXSEA EXECUTE 0 1 UI IMU ScliDoc 1 2 a 4 RN1106MFV it Biomechatronics Tite Execute Clutch ELE E Rem m mE 75 Amherst Street mit Letter uet Cambridge 02139 l media Date 2015 03 05 Time 12 28 58 Sheet of USA lab
12. 93 Figure 70 Current PID setpoint versus measured phase current kp 50 ki 50 94 Figure 71 First implementation of an Impedance Controller 2014 94 Figure 72 Calculated trajectory acceleration speed and position over time 95 Figure 73 Knee position 1 1 020 0 02 0440000000000000004050000000000001 96 Figure 74 Streaming sensor 0 nennen nennen enirn nnns 97 Figure 75 Logging Data at 5OOHz ist t URBES EE RES e 98 Figure 76 Streaming Data in Python n 102 Figure 77 ExperImenta S t D u aa Su natan en a 105 Figure 78 Force calibration test on the FitSocket 106 Figure 79 500mA load DC 2V div anes korr Ner ka re e ener ud 107 Figure 80 500mA load AC 20mV div em deesdocd ip nauta t a 108 Figure 81 Load testing with constant current 108 Figure 82 500mA load DG 1V div oe Reb dente rab ERR RP AE 109 Figure 83 500mA load AC 20mV div
13. 1 LSB PTR uintl6 curr PWM 1 WriteComparel uint16 curr SET 16 1 2 LSB PTR 011516 PWM2DC curr pwm PWM 1 WriteCompare2 uint16 curr gt gt 1 1 Compare 2 can t be 0 or the ADC won t trigger return ctrl current error To avoid destroying expensive Maxon motors during the calibration phase a test bench was designed and assembled In the present configuration the phase to phase specs are 120uH and 0 40 The power resistors are rated for 200W The larger inductance makes it safer for the power electronics under test The current ripple will be half of the Maxon s Figure 69 Load test bench equivalent to a stalled Maxon brushless motor Figure 70 is the result of a test session where the PID was hand tuned to minimize the noise The setpoint was incremented by 50 for every sample and the current was measured with a Tektronix A622 current probe 93 Current vs setpoint 50 ki 50 16 14 12 eo 10 lt P t S97 we 6 c 4 yi 2 g y 0 0105 0 6347 R 0 9999 0 0 200 400 600 800 1000 1200 1400 Setpoint Figure 70 Current PID setpoint versus measured phase current kp 50 ki 50 The sense resistor is 5mQ the analog gain is 20 and the ADC is 12bits over 5V The theoretical current resolution is 12 2mA bit Wi
14. Using GDB DSF Hardware Debugging Launcher Select other Revert Debug Configurations Create manage and run configurations x B Name Debug Main Debugger Startup 5 Source 1 Common gt E C C Application Attach to Application S Postmortem Debugger Y S Remote Application E manage Debug 1 v S GDB Hardware Debugging OpenOCD Debug OpenOCD Debugging E GDB SEGGER J Link Debugging gt Launch Group Filter matched 12 of 12 items Source Lookup Path gt 2 Default 71 Search for duplicate source files on the path Using GDB DSF Hardware Debugging Launcher Select other Add Remove Apply Revert m m 4 OpenOCD Debug B Main Debugger gt Startup 87 Source Common gt s C C Application Attach to Application Postmortem Debugger E Remote Application E manage Debug 1 Y E GDB Hardware Debugging E OpenOCD Debug OpenOCD Debugging S GDB SEGGER J Link Debugging Launch Group Filter matched 12 of 12 items o Saveas Local file Shared file Display in favorites menu amp 3 Debug Standard Input and Output Allocate console necessary for input File 8 Launch in backg
15. woo sa GND GND 1 The power supply from the application board is connected to the ST LINK V2 debugging and programming board to ensure signal compatibility between both boards 2 Connectto GND for noise reduction on the ribbon 3 Atleastone of this pin must be connected to the ground for correct behavior connecting all of them is recommended Optional for Serial Wire Viewer SWV trace Available on ST LINK V2 only and not connected ST LINK V2 OPTO Pin mapping Manage STLink 1 1 2 9 3 8 4 7 5 15 6 13 The adapter shown below uses a 6 pin male header because it was originally made for the MiddleMan 0 1 board Prog Adapt was built with a female header to interface with the old cable As we are not using the MiddleMan anymore it is now possible to solder the wired directly to Prog Adapt same pinout 204 Use the flipped FFC connector position The FFC conductors have to face the PCB Pin 1 is Red 03 19 2015 First make that your board is powered Connect Manage to Plan Connect the STLink v2 programmer debugger to Manage using the Prog Adapt cable Make sure that it s seen by your VM Debugging Open a terminal and call Leave that window open x Flexsea ubuntu flexsea ubuntu openocd s Documents embedded arm openocd bin share openocd scripts f interface stlink v2 cfg f target stm32f4x_stlink cfg Open On Chip Debugger 0 8 0 2015 03 09 14 36
16. 1 000 0 000 3 500 3 000 2 500 2 000 1 500 1 000 0 500 0 000 TPS2111 5V Output Current 0 100 200 300 400 500 600 700 800 900 mA TPS73733 Regulator output Current 0 100 200 mA 300 400 500 600 700 800 900 Figure 92 Load testing The TPS1111 has a current limit of 1A Its output was dropping around 900mA in the test consistent with the datasheet when the current consumed in the circuit is taken into account The 5V signal was dropping before the 3V3 limit was reached A conservative specification for peripherals attached to the Expansion connector will be 500mA at 3 3V 119 Mean Min No period found Figure 93 Automatic switching of the input power source The lowest 5V voltage measured was 4 6V close to the calculated value of 4 8V The 3V3 signal is unaffected by the input power source transition 5 3 System Benchmarks 5 3 1 SPI Frequency and Data Rate Criteria All serial interfaces SPI and RS 485 should have a minimum bitrate of 2MBits s FlexSEA Plan is the SPI Master it generates the clock Without any termination resistors the highest value that was successfully tested using the Stream application and test equipment was 12Mbits s as shown on Figure 94 This is 6x the criteria 120 ek Run Tria d f M ka AAJ Atm umor sta NIV tjt PP ada Figure 94 SPI Data Rate 83ns 12Mbits s For typical application for the other be
17. Eq 8 lin 6W 23 5V 255 32mA Eq 9 Pin Viv 24V 255 32mA 6 13W Eq 10 6W 6 13W 97 8 Eq 11 3 1 10 2 Low voltage power supplies It is important to minimize the power consumption of prostheses and other wearable robots to minimize the volume and weight of the batteries used they have a direct effect on system efficiency and to minimize heat generation a potential cause of discomfort for the users The MOSFET gate drivers require 10V and the microcontroller and most sensors are powered at 5V 56 Using a linear regulator to provide 50mA at 5V 250mW requires 50mA at 24V 1 2W 21 efficient energy conversion with almost 1 watt of heat that requires to be dissipated this is unacceptable The only sensible solution is to use one or more switched mode power supplies SMPS The current requirement on the 10V bus being small it was decided to use the 10V as a pre regulation stage for the 5V power supply Using 10V rather than 24V as an input voltage allows a wider range of ICs to be used The core of both circuits was designed with TI WEBENCH Design Center The same list of modifications was applied to both designs as detailed below 14 http www ti com Isds ti analog webench overview page DCMP sva web webdesigncntr en amp HOS sva web webdesigncntr vanity lp en 57 3 1 10 3 LM25011 10V 500mA D26 VG D9 0580 C38 luF
18. The version I M using is 11 1 0 build 2496824 I created the VM with minimalist specs FlexSEA P gt Power on this virtual machine Edit virtual machine settings CF Upgrade this virtual machine Devices Memory 2GB Processors 4 Hard Disk SCSI 20 GB 3 CD DVD SATA Auto detect CD DVD 2 SATA Auto detect If Network Adapter NAT USB Controller Present Sound Card Auto detect de Printer Present Display Auto detect v Description Type here to enter a description of this virtual machine If you use it a lot you should assign more processors and RAM to it to make it snappier Installing it on your SSD is also a good idea 180 The VM is 6 83GB You can access it on the Biomech Hub hub media mit edu mas biomech storage shared jfduval FlexSEA Make a local DO NOT MODIFY THE SERVER VERSION Launch VMware File gt Open gt navigate to where you are storing the VM gt FlexSEA vmx Click on the green arrow to launch the machine then click on I Copied It Ubuntu will boot you might see a black screen for 20s before is starts displaying information login flexsea password flexsea Ubuntu Desktop Eclipse Luna Common Commands txt It s ready to be used Hint Alt Ctrl Enter will make it full screen FlexSEA Execute 0 1 Hardware overview 03 16 2015 Expansion Connector Top view 181
19. manage gt Debug As gt Debug Configurations Do exactly like on that picture more details in Eclipse OpenOCD GDB Debugging for the Manage Board Debug Configurations Create manage and run configurations E Name manage Debug B Main Debugger gt P gt Startup 7 Source Common c C C Application GDB Setup C C Attach to Applicatio c C C Postmortem Debug c C C Remote Application Browse Variables Remote Target Use remote target DB OpenOCD Debugging Manage Debug OpenOCD t GDB SEGGER J Link Debugc Launch Group JTAG Device Generic TCP IP Host name IP address localhost Port numbe 3333 71 Force thread list update on suspend Using GDB DSF Hardware Debugging Launcher Select other Apply Revert Filter matched 10 of 10 items 9 DSF 94119 Close o debug open terminal launch openocd openocd s Desktop FlexSEA embedded arm openocd bin share openocd scripts f interface stlink v2 cfg f target stm32f4x stlink cfg and leave that window open In Eclipse click Debug and use the configuration you just made It will open the Debug perspective and you ll be able to do step by step code execution watch variables etc o program the chip 188 Compile in Release mode Open a terminal and navigate to manage Release You should see manag
20. Licensed under GNU GPL v2 For bug reports read http openocd sourceforge net doc doxygen bugs html Info This adapter doesn t support configurable speed Info STLINK v2 JTAG v17 API v2 SWIM v4 VID 0x0483 PID 0x3748 Info using stlink api v2 Info Target voltage 3 244269 Info stm32f4x cpu hardware has 6 breakpoints 4 watchpoints 205 In Eclipse compile for Debug Compile the Manage project Click on the Bug icon use OpenOCD Debug FlexSEA The IDE will switch to the Debug perspective Click Resume F8 to start the code The RGB LED will be green for a few seconds then blue LEDO will blink You can use the Pause button to pause the code execution the Step Into and Over buttons to navigate in the code the Variables and Watch windows to inspect values etc When you are done you can hit Terminate Ctrl F2 In your terminal Ctrl C will close OpenOCD Programming In Eclipse compile for Release Compile the Manage project Open a terminal navigate to the release folder cd Desktop FlexSEA biomech ee svn Code flexsea_1_0 manage Release and call openocd s Desktop FlexSEA embedded arm openocd bin share openocd scripts f interface stlink v2 cfg f target stm32f4x_stlink cfg c init c reset halt c sleep 100 c wait halt 2 c flash write image erase manage elf c sleep 100 c verify image manage elf c sleep 100 c reset run c shutdown flexsea ubuntu Desktop FlexSEA biomech ee svn Code fle
21. 10 24s If the last sample is lower than 81 25 of the average value the code interprets this as a disconnected battery In the test code the ELED output is high when the battery is disconnected simulated with a sudden voltage drop 114 Figure 88 Disconnected Battery Detection Code The circuit was initially powered at 19V calculated threshold of 15 44V The disconnected battery flag was raised at 77 8 of the average close to the calculated 81 25 5 2 FlexSEA Manage 5 2 1 Level shifting FlexSEA Plan and FlexSEA Manage Interface In the current application both sides of the level translator are powered at 3 3V To confirm that it is functional a simple SPI packet was sent from the Plan board BeagleBone Black In yellow is the MOSI line and in blue is MISO confirming that data is properly exchanged between the two processors 115 Mean Figure 89 SPI signals Plan side of the level translator 5 2 1 1 Analog Inputs With Programmable Features To test the two filtering options a 1kHz 0 3 3V sine wave was applied to AINO FCO was changed by software every 100ms 116 m wm em With the same test signal 1kHz 0 3 3V sine wave applied to AIN2 simple test code was used to incremen t the gain by 10 out of 256 every 10ms illl hal lle lle lale de Lll jii eid il diii Ji JE i T 117 The 1 lt G lt 10 spec was calculated
22. 2 11 17 Communication Interfaces MPLAB ID MP32 Power Electronics Figure 1 Microcontroller based architecture example 1 Low Level Control Actuation 200W Brushless Motor w Encoder Electromagnetic Clutch 24V LiPo Battery 1200 mAH Power High Level Control 400W Brushless Motor Drive 802 11n Wireless Adapter 2 kHz Audible Alarm Smart LED Status Indicator Communication Single Board Computer 16 Bit A D Conversion Inertial Measurement Unit Flexure Based Load Sensor Absolute Encoder Signal Processing and Sensing Figure 2 Embedded computer based architecture example 2 Table 1 presents a general comparison of the two design approaches Table 1 Architecture comparison Microcontroller Embedded Computer Pros e Small form factor that can easily be adapted to different mechanical designs e Low power e Unit costis low e Low level software C and or ASM processor efficient e Quick design phase e High level software C Python Java Matlab ease of development e Minimize the number of specialized skills required to modify the system Cons e Development prototyping cost can be higher e Longer design phase e Requires Electrical Engineering skills for the design maintenance and modification Low level software C and or ASM less portable requires specialized skills e High l
23. Create the file with sudo nano etc udev rules d stlinkv2 rules add line of text ATTRS idVendor 0483 ATTRS idProduct 3748 MODE 0666 Update sudo udevadm control reload rules Update bash Open the file with nano bashrc Add this line at the end just below the GCC ARM line that you added before export PATH PATH home flexsea Desktop FlexSEA embedded arm openocd bin bin Update bash with source bashrc Test installation with openocd s Desktop FlexSEA embedded arm openocd bin share openocd scripts f interface stlink v2 cfg f target stm32f4x stlink cfg You should see Open On Chip Debugger 0 8 0 date and time e project under Eclipse Launch Eclipse then File gt Import gt General gt Existing Projects into Workspace gt browse to your directory Code flexsea_1_0 manage You will see the project in the Project Explorer Right click on the manage project gt Properties gt C C Build gt Settings gt Toolchain and update the Global toolchain path by clicking on global and navigating up to home flexsea Desktop FlexSEA embedded arm gcc arm none eabi 4 9 2014g4 bin You can now build the project hammer icon You ll get warnings because I m a bad programmer but no Errors A hex file will be generated 187 o The Debug configuration is saved in the Workspace and not in the project file so you have to do it manually Right click
24. FFC Pin assignment 10 pin connector Table 3 2 Communication Protocol Pin Assignments SWV trace is only available in conjunction with SWD debugging Pin assignment 6 pin connector on Prog Adapt 201 Mapping Cable 6 pin connector Q N OA QO N 0 Another representation of the same information 3 2 2 10 Connector 10 pin connector is configured as dual row with 50 mil pitch It is used with a ribbon cable provided to mate to a similar connector on the target board The recommended mating connectors are the Samtec FTSH 105 01 L DV K surface mount and the FTSH 105 01 L D K through hole or similar connectors available from other vendors The signal assignment is shown in Figure 3 3 When programming JTAG devices note that MiniProg3 does not support nTRST pins Figure 3 3 10 Pin Connector with Pin Assignments XRES Note The ribbon XRES cable connector extends beyond the JE body of the Tm connector Be sure 2 to allow room GND ud gt SWD CLK lt TCK TTO epo GND GND TMS O VTARG gt 5 VTARG in 1 TMS gt SWD_IO Step 1 Cut the cable that came with the MiniProg3 in two By cutting it in the middle you can make two adapters from 1 cable 202 Step 2 Separate the wires Keep 1 2 3 4 6 10 and cut down the others Strip 2 3mm of insulation of the wires
25. FlexSEA eclipse At this point it probably won t launch no valid JRE installed by default Use the software manager to get a JRE or follow this website to get sudo add apt repository ppa webupd8team java sudo apt get update sudo apt get install oracle java8 installer Eclipse should launch when you double click on eclipse home flexsea Desktop FlexSEA eclipse eclipse You can create a shortcut by right clicking on the program and Make Link I like having that shortcut on the Desktop default I m placing the workspace in home flexsea Desktop FlexSEA workspace e Eclipse CDT tools Launch Eclipse click on Help gt Install new software Paste that URL http gnuarmeclipse sourceforge net updates in the search box more details http gnuarmeclipse livius net blog plugins install Wait a few seconds while it refreshes click on the plugin to install it Follow the wizard e ARM GCC compiler I was following this tutorial http hertaville com 2013 09 02 stm32f0discovery part 1 linux Get sources from there https launchpad net gcc arm embedded download I used gcc arm none eabi 4_9 2014q4 20141203 linux tar bz2 Unzip in FlexSEA embedded arm It will add a folder named home flexsea Desktop FlexSEA embedded arm gcc arm none eabi 4 9 2014q4 Install 32 bits libs if using a 64 bits OS ia32 libs is obsolete add the 3 libs that are suggested to you when
26. The selection of a P channel or N channel load switch depends on the specific needs of the application The N channel MOSFET has several advantages over the P channel MOSFET For example the N channel majority carriers electrons have a higher mobility than the P channel majority carriers holes Because of this the N channel transistor has lower RDS on and gate capacitance for the same die area Thus for high current applications the N channel transistor is preferred DI 1 P BS C42 2 01 100nF luF luF 100nF MBROSSO TP 1 47 5 615 L vB ay S luF 100nF GND GND GND GND 3 s 2 7 O M 24 ww p m o moim vs LS 1 1 amp 2 4 Io 5 LO R2 _ a 47 5 G IH IRS21867 s GD GND T R27 20005 GND Figure 16 Half bridge on Execute 1 of 3 A voltage of 10V from the Gate to the Source noted Vas is required to fully turn on an N Channel MOSFET The source of the high side switch can swing from the lowest system voltage to the highest To turn the high side switch on we need a voltage higher than the motor voltage typically the highest voltage in a system 8 http www onsemi com pub link Collateral AND9093 D PDF 37 gate driver power amplifier that accepts a low power input from a controller IC produces a high current drive input for the gate of
27. Their gain being limited to 1000V V a dual stage design is used The design was first simulated in TINA TI Variable gain now 45 R3 1k R2 8k 2 5 AA Fixed G 105 gain Adjust offset here AS i Figure 24 TINA TI Spice simulation of the two stage differential amplifier design Amplifying with gains in the thousands right next to a BLDC motor can easily be problematic While the first page of the datasheet claims a 94dB common mode rejection ratio CMRR the first set of experiments were inconclusive The CMRR is strongly dependent on the signal frequency 45 COMMON MODE REJECTION RATIO vs FREQUENCY N T e o CMRR dB 40 20 10 100 1k 10k 100k Frequency Hz Figure 25 CMRR vs Frequency TI INA331 233110 instrumentation amplifier Typical motor PWM frequencies are from 20 to 100kHz Analog filtering was added before the first amplification stage limiting the bandwidth to 500Hz and offering 44dB of rejection at 20kHz 100nF 100nF DDA TPD4E004DRYR GND GND GND R36B TPD4E004DRYR GND GND GND Figure 26 Input filtering and protection Two 2 digital potentiometers Microchip MCP4661 dual potentiometer U5 used to adjust the offset and the second stage gain U5B allows the user to adjust the output reference of
28. jl d dg The beige connector on the bottom right is the Expansion connector On the bottom Left is the USB Micro B connector The red wires are for power and motor detailed below Bottom view open source ardware The blue connectors to program and debug the PSoC microcontrollers The silkscreen indicates 4 PSoC 4 co processor and 5 PSoC 5 main microcontroller 182 Motor and power connections Expansion connector A JO 4 1 4 EN i 183 EXP8E EXP9E IE 2 EXPIE EXP6E RS485_A3 RS485_B3 RS485_A2 RS485 B2 RS485 AI RS485 BI 5V 1 2 CC O 7 8 t Ct rt 17 Ci comin 21 22 BENE 24 LI 29 2 4 E 2 29 32 tf T 38 UI 40 V S GND GND IMU Position Top view IMU is on the bottom lt CLUTCH POW HALL3E HALL2E HALLIE 5 4 EXP7E EXP10E SG P SG N 184 X 31 445mm Y 15 621mm Installing the Plan amp Manage Development Environment on your host computer 01 18 2015 updated 03 09 2015 amp 16 03 2015 Host computer Ubuntu 14 04 LTS 64bits Can also be used for Ubuntu 14 04 LTS 32bits A pre configured VMWare 10 virtual machine with 32 bits Linux is available The list of steps below is sequential It keeps everything separated and logical if you wish to insta
29. slots 177 BBB x SCP X jfduval ubuntu ssh beaglebone local l root Debian GNU Linux 7 BeagleBoard org BeagleBone Debian Image 2014 04 23 Support FAQ http elinux org Beagleboard BeagleBoneBlack Debian root beaglebone local s password Last login Wed Apr 23 20 57 41 2014 fr root beaglebone flexsea_bbb_init FlexSEA is ready to be used root beaglebone home debian Desktop ubuntu 2 local Eclipse OpenOCD GDB Debugging for the Manage Board 02 24 2015 Create manage and run configurations Name OpenOCD Debug Main Debugger gt Startup Source Common gt E C C Application E C c Attach to Application Postmortem Debugger C C Application Debug manage elf Variables Search Project Browse v S C C Remote Application manage Debug 1 Project 7 GDB Hardware Debugging manage me S OpenOCD Debug E GDB OpenOCD Debugging E SEGGER J Link Debugging gt Launch Group Filter matched 12 of 12 items o Build if required before launching Build configuration Select configuration using C C Application Enable auto build Disable auto build Use workspace settings Confiqure Workspace Settings Using GDB DSF Hardware Debugging Launcher Select other Close Create manage and run configurations 850i Debug
30. 12 1 1 3 H3 BIOM FLEXSEA EXECUTE 0 1 Half Bridge SchDoc Nt AQ AWGI6_TII as MOT 1 MOT gt MOT 3 4 J7 AWGI6 J8 AWGI6 TH Shorted Leads BIOM FLEXSEA EXECUTE 0 1 Shorted Leads SchDoc Figure 11 BLDC schematic top level 34 MCP9700A Le 56 100nF GND GND 4 5 5V MOT 1 MOT MOT 3 R53 R54 R55 50k 5 101 103 s e gt gt 86 47 gt 56 R57 R58 k z 10k Z 210k z 28 5 ga ac NGC Z x NA GND GND GND GND GND GND Figure 12 BLDC sensors phase voltage amp temperature U7 is routed close to the power MOSFETs Figure 13 shows the decoupling capacitors present on the Power Supply schematic sheet They are mainly used for the BLDC driver C11 14 amp C22 27 are relatively small ceramic capacitors Their total value 100pF is not sufficient to guarantee that the bus voltage won t exceed the limits if a large amount of regeneration is done C5 to C7 are used to absorb all this energy and to provide power during switching transitions as well but they are bulky In applications were volume is highly constrained C5 7 can be removed if an external protection circuit is added to the system typically a bus dump semiconductor or resistor This should be done with care 1 VB L 5 ail OY 180uF 180uF 180uF GND GND
31. B4 RS485 AS RS485 B5 RS485 A6 RS485 B6 RS485 AI Title FlexSEA Manage 0 1 Size Letter Number Revision Date 2015 04 08 Time 12 52 46 Sheet of Biomechatronics MIT Media Lab E 14 274 75 Amherst Street Cambridge MA 02139 USA 4 mit lab File BIOM FLEXSEA MANAGE 0 I SchDoc 3 153 UISA uIsD ULE UISF 0156 INT Hio PDO PEO 1 pro PAI eo PDI PEI H PGI PA2 PD2 PE2 tet iri PD3 tie PES Sie PG3 Eum Em m Mio 485 45 SPI4 MOST SPIS NSS hi SIS 385 RXS 97 SPISSCK 1 9 185 PEZ SPIS MISO 202 DIO4 SSG 91 GT PAS et PES le inh PGR 9 sae 9 SER h pro md PGI PAIO Uie pcio PE10 asm pcio ae PCL SEEREL S piosmisos 5591 PGI PAI2 PCI PEI 504 Dr DEBE oo 22 285 DE2 53 DIOS SCK6 1 PAIS PCL PED 334 Dr PGIS q PCI4 PEM Sie PF14 D PAIS PEIS 3555 PF15 PGIS STM32FA27ZITG STM32F427ZIT6 STM52F427ZIT6 STM52F427ZIT6 STM52F427ZIT6 STM52F427ZIT6 STM32F427ZIT6 DC PU DIOO SDA2 DIOUSCL2 DIO2 U3TX DIO U3RX 0104556 DIOS SCK6 gt DIO6 MISOS SPI4 NSS 2 DIO7 MOSI
32. Compact routing using polygon pours 58 Fig re42 5V S00mA SNIDS uu uz erre nea oa Te edd eoe ea Reli E A aa 59 Figure 43 Compact routing using polygon pours 59 Figure 44 FlexSEA Manage 0 1 iieri eb bae e i eee 61 Figure 45 Manage 0 1 Hardware n 62 Figure 46 STM32FA sub famllies sus tette ie Peste does te EE ada 64 Figure 47 MiddleMan 0 1 predecessor to Manage 0 1 on top of a BeagleBone Black 65 Fig re 4A8 Int rfaceto Plan SEWER e EI WIE IIR 65 Figure 49 Level translation SPl 66 Figure 50 Level shifting external reset signal 66 Figure 51 Expansion connector eese eater e eo tonne ena a Ra Ea SR nae Re RE ede PU Nee godes 67 Figure 52 ANO amp AN1 1 10kHz 1 or Retos det n bl er Ratio aur Un bs 68 Figure 53 AN2 amp AN3 1 10kHz LPF 1 lt G lt 10 du 68 Figure 54 AN4 amp ANS Buffered input a 68 Figure 55 AN6 amp AN7 Programmable voltage divider
33. Downto 12 Down to 3 034x3 22 STM32F401 84 12810512 96 Downto 128 Downto 10 Down to 3x3 Figure 46 STM32F4 sub families16 The STM32F427ZI was selected because it is 180MHz and has the largest amount of memory possible The F437 and F4x9 chips only add TFT controllers and video accelerators that are not required in our application The LQFP 144 package was the smallest package that allowed the use of all the required peripherals 3 2 2 Interface to Plan Most of the work presented in this thesis was using a BeagleBone Black embedded computer as the FlexSEA Plan board While the previous version of the FlexSEA Manage board MiddleMan 0 1 was designed to fit its form factor the Manage 0 1 was designed with polyvalence in mind Multiple new embedded computers are released every year Having the option of using new generation hardware can extend the life of the FlexSEA system 16 http www st com web en catalog mmc FM141 SC1169 SS1577 sc stm32f4 64 Figure 47 MiddleMan 0 1 predecessor to Manage 0 1 on top of a BeagleBone Black The only specific requirement is to have a fast full duplex SPI bus The connector that interfaces with Plan has 8 pins 5V to power the circuits on Manage 4 wires for SPI MOSI MISO SCK amp NSS a reset signal and a VP Plan Voltage line 5VP VP J3 1 Plan 2 BIOM FLEXSEA MANAGE 0 1 Plan SchDoc 3 4 5 6 8 PC8H Z GND Figure 48 Interface to Plan The VP line is
34. Execute deals with all the motor control functions Has enough computing power to run advanced algorithms Most control loops current speed impedance force can be closed on this board 171 More details FlexSEA Execute 0 1 Hardware overview Development Tools The Execute boards has two microcontrollers one PSoC 4 the safety co processor and one PSoC 5LP the main computing element The Safety Co Processor runs safety critical code only a user with a deep understanding of the safety features should modify its code To reprogram the PSoC you ll need a proprietary but free IDE names PSoC Creator I m using 3 1 SP1 http www cypress com psoccreator It s Windows only Programmation is done with a mix of graphical programming and C it uses GCC I m using a MiniProg3 with a special cable to program and debug the code What s in the box 03 17 2015 FlexSEA kit part list 1x Plan BeagleBone Black new in box 1 Manage in a metallic bag new in box 1x Execute with cables soldered and initial software 2x USB Mini B cable 1x MiniProg3 1x STLink v2 2x Prog Adapt 1x Plan Manage cable 1x Manage Execute cable 1x Execute power cable with adapter 1x Output device big LED 172 elementiu Other than that you ll need one DC power supply and an Ethernet cable connected to the network only for a few minutes 03 19 2015 Connec
35. GND L l S L L L S 10uF 10uF 10uF 10uF 10uF 10uF 10uF 10uF 10uF 10uF GND GND GND GND GND GND GND GND GND GND Figure 13 VB Decoupling capacitors 35 3 1 3 1 Half bridges Figure 14 H Bridge circuit DC motors are commonly driven by a circuit called an H Bridge An H bridge is an electronic circuit that enables a voltage to be applied across a load in either direction Closing S1 and S4 will make the motor turn in one direction while closing S2 and S3 will make it rotate in the opposite direction Closing S1 and S3 or S2 and S4 can be used to brake the motor Closing S1 and S2 or S3 and S4 will create a short circuit on the power supply and can lead to catastrophic failure The switches in the above schematic be relay contacts bipolar transistors MOSFETs or IGBTs MOSFETs offer the best efficiency for low voltage applications Voltage V MOSFET 20 100 Fsw kHz Figure 15 MOSFET vs IGBT when to use B http en wikipedia org wiki H bridge http www renesasinteractive com file php 1 CoursePDFs DevCon_On the road DevCon_On the Road Power IGBT 20vs 20MOSFET_Which 20Device 20to 20Select pdf 36 For low voltage high frequency application such as ours MOSFETs are the most common solution A good reason not to use IGBTs is that a distributor like Digikey doesn t carry devices rated for less than 300V and the smallest SMT package available is DPAK
36. Sheet of USA File BIOM FLEXSEA MANAGE 0 1 IMU SchDoc 1 2 3 j 10 4 User Study FlexSEA User testing MIT Media Lab Biomechatronics 03 19 2015 Part 1 Before the experiment Have you heard of FlexSEA before this experiment Have you tested the FlexSEA system before this experiment Are you by training an engineer Are you by training an electrical software or computer engineer Do you have a basic proficiency with C Do you have a basic proficiency with Linux Were you given documentation about the system Did you receive 3 circuit boards 1x Plan 1x Manage 1x Execute and accessories Were the 3 circuit boards connected together From this point on please follow FlexSEA How to use in the provided documentation Part 2 Testing FlexSEA Plan and FlexSEA Manage Did you use the pre configured virtual machine Did you install the development tools yourself Were you able to successfully configure a new BeagleBone Black Can you cross compile the plan program Release mode Can you connect to the Plan board over SSH via USB Can you transfer a file from your host computer to the BBB Can you use the plan executable on the BBB Can you compile the manage program Can you program the Manage board Can you read the state of the Manage pushbutton from Linux Estimate
37. Step 3 Solder the surface mounted FFC connector to the PCB Use the Flipped position Step 4 Solder the 6 wires to the PCB according to the mapping presented above Step 5 Connect an FFC cable and test your work The conductors need to face the PCB If it works ie you can detect the PSoC in PSoC Creator go to step 6 Step 6 Hot glue everything together Prog Adapt 0 1 for FlexSEA Manage 0 1 03 19 2015 We use the STM32F4 Discovery board as a reference for the pinout manual http www st com st web ui static active en resource technical document user_manual DM00039084 pdf Table 3 Debug connector CN2 SWD VDD_TARGET VDD from application 4 swpdetainputoutput EL NRST RESET of target MCU 8 sw The ST Linv V2 has 20 pins cable manual http www st com st web ui static active en resource technical document user_manual DM00026748 pdf 203 3 2 Connection with STM32 applications For STM32 developments the ST LINK V2 needs to be connected to the application using the standard 20 pin JTAG flat ribbon provided Table 4 summarizes the signals names functions and target connection signals of the standard 20 pin JTAG flat ribbon Table 4 JTAG SWD cable connections ST LINK V2 connector ST LINK V2 function Target connection Target connect CN3 JTAG k jm ll mersswo soon Not connected GND 9
38. TPD4F004DRYR 24 2 100 1 GND Title Manage Analog inputs Size Letter Number Revision Date 2015 04 08 Time 12 52 47 Sheet of Biomechatronics MIT Media Lab E14 274 l USA lab File BIOM FLEXSEA MANAGE 0 1 AnalogIn SchDoc 3 157 3 4 R13 Disp TPD4E004DRYR GND D3B TPD4E004DRYR TPD4E004DRYR TPD4F004DRYR 4 3V3 DE 100nF 5 me Biomechatronics Manage Digital Inputs Outputs MIT Media Lob ET amp 274 ER z Um 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 l media GND Date 2015 04 08 Time 12 52 47 Sheet of USA lab File BIOM FLEXSEA MANAGE 0 1 DigitallO SchDoc 3 158 Title Manage Power outputs Biomechatronics MIT Media Lab E14 274 p EX 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 LH media Date 2015 04 08 Time 12 52 48 Sheet of USA lab File BIOM FLEXSEA MANAGE 0 1 PowerOut SchDoc 3 4 159 160 1 2 3 4 A 33 3 VP 3V3 B 53 54 100nF 100nF GND GND z 5 m Biomechatronics Manage Plan Interface MIT Media
39. and software for precise motion control data acquisition and networking Scalability is obtained through the use of fast industrial communication protocols between the modules and the standardization of the peripheral interfaces Hardware and software encapsulation is used to provide high performance real time control of the actuators while keeping the high level control development fast safe and simple The FlexSEA kits are composed of two custom circuit boards advanced brushless motor driver and microcontroller board one commercial embedded computer a complete software stack and documentation During its development it has been integrated into a powered prosthetic knee as well as an autonomous ankle exoskeleton To assess the usability of the FlexSEA kit a new user successfully used a kit to read sensors and control an output device in less than three hours FlexSEA simplifies and accelerates wearable robotics prototyping Thesis Supervisor Hugh Herr Ph D Title Associate Professor of Media Arts and Sciences FlexSEA Flexible Scalable Electronics Architecture for Wearable Robotic Applications by Jean Fran ois Duval The following served as readers on this thesis committee Research advisor Hugh Herr Ph D Associate Professor of Media Arts and Sciences Program in Media Arts and Sciences Thesis Supervisor Thesis supervisor Joseph Paradiso Ph D Associate Professor of Media Arts and Sciences Program
40. are in section 4 Software Design 2 6 Design solutions short answers While all the details are available further in this document this section offers quick answers and solutions to all the issues identified in the introduction Lack of reliability The issue of reliability is addressed at the board level with good design practice documented unit tests and the use of safety mechanisms such as ESD protected inputs At the system level the number of connections is reduced by embedding more features in the boards and robust yet miniature connectors are used Lack of processing power overloaded microcontroller A dedicated microcontroller with a wide array of sensor inputs on the motor controller FlexSEA Execute offloads the other computing units FlexSEA Mange and FlexSEA Plan from the intensive motor control functions The microcontrollers used are also high performance The optional embedded computer can be used for processor intensive applications 24 The original designer left amp No electrical engineer in the team Documentation must be exhaustive and accurate in order to fully enable the user One of the graduation criteria is a user test The system is designed in a modular way the least intrusive way of using FlexSEA is to use a simple Linux terminal Slow communication peripherals Closing control loops requires deterministic timings and fast refresh rates it places a lot of stress on the board to boar
41. compatible with any physical interface Currently we use full duplex Serial Peripheral Interface SPI bus from the FlexSEA Plan to one FlexSEA Manage and multi drop RS 48522 busses from FlexSEA Manage boards to FlexSEA Execute boards At this level the data is in the forms of bits and bytes represented by varying electrical levels In software all the data structures linked to the physicallayer are named tx_buffer or rx_buffer with a suffix associated to the bus used To send a command the user will copy a packaged payload generated by the Data Link layer to the relevant transmission buffer 4 1 4 Receiving commands In the layers description the emphasis was on the transmission of commands When bytes are received by a physical communication interface the inverse sequence is done First either after new data is received or on a fixed timing the RX buffer is parsed by the unpack_payload function That function searches for a header then for a footer in the right position the position is calculated from the Bytes field that follows a valid header and then for a valid checksum Data with a valid Header and Footer is known as properly framed When a properly framed command fails at the checksum test it is eliminated buffer erased If the checksum is valid it is copied to a new buffer and the original version is erased to avoid double detection This new buffer containing the unpacked payload will be parsed by the payl
42. driver 38 ooooo 0 00 9 T T 60000 Figure 17 The 3 channels use the same compact layout B highlighted As can be seen on Figure 17 a large number of vias are used They serve two purposes thermal transfer and layer tying This PCB has 6 layers Layer 1 Top components signals and small planes e Layers 2 and 5 Ground planes Layer 3 Power Top half is plane Bottom half is 5V plane e layer 4 Mixed In the context of the bridges it is used for the nets and for VB e Layer 6 Bottom components interface to the heat sink so a maximum plane area is used around the bridges The critical power paths are always shared by a minimum of two layers 3 1 3 2 Motor current sensing The programmable analog blocks of the PSoC can be used to design a small low cost motor current sensor One shunt resistor per bridge is used Two resistors and one capacitor are required for the feedback In the PSoC we use one operational amplifier one DAC and one analog multiplexer 39 Circuit 2 With Offset Works with Regen SINE 0 20 20k 0 lt gt v1 24V 2m Power rating of the sens 3 1 3 3 Shorted Quadrants 1 and 3 be the 1V ref 4mVlbit V n002 1 Figure 18 simulation 20 motor current sensing e resistor Pegs I R 2042 0 0050 2W leads protecti
43. line The master PSoC the 5LP toggles that line in its main loop The safety microcontroller use programmable hardware to measure the pulse width and determine if the main microcontroller is behaving normally ie if the timings are respected I2C is used to share sensor data not for safety critical functions Multiple sensors are read by the Safety CoP to evaluate the system state All the PWM lines are going through the safety coprocessor If a problematic situation code not executing properly over temperature disconnected battery etc is detected the safety coprocessor can open all the signals and place the motor in a free wheeling mode More elaborate protection software will then assess the situation and put the system in a safe mode such as a highly damped system shorted leads protection 33 PWMH1 H1 PWML1 s fe L1 PWMH2 ss Bs H2 PWML2 951 4 L2 PWMH3 ssi PWML3 s L3 Control 1 Figure 10 PWM signals passing through the Safety CoP The Safety CoP is also in charge of the negative voltage generation and the gate driving for the shorted lead protection see 3 1 3 3 More details about the safety features are available in section 5 1 4 Safety Features 3 1 3 Brushless DC Motor The BLDC schematic consists of 3 copies of the Half bridge sheet motor commutation the Shorted Leads protection circuit phase voltage sensing and bridge temperature sensing HI
44. mit Size Letter Number Revision Cambridge MA 02139 media Date 2015 04 08 Time 12 52 47 Sheet USA lab File BIOM FLEXSEA MANAGE 0 1 FLASH SchDoc 3 4 163 164 3V3 33V3 Pin Number Pin Mame Pin Description 7 AUX CL PC Master serial clock lor connecting lo extemal sensors VO supply voltage ADO 500 Stave Address LSB SP serial data output SDO 10 REGOUT Regulator titer capacitor connection FSYNC Frame synchrorszalbon digital input Connect to GND it unused Interrupt igea output totem pole or open drain 2 Note The Interrupt ine should be connected a pin on the Application Processor AP that can bring the AP out of suspend mode vob Power supply voltage and Otai UO supply voltage 18 GND Power supply ground RESV Reserved Do not connect 20 RESV Reserved Connect to GND n AUXDA PCmaster seri data for connecting to external sensors Chip select SP mode onty T 25 SELI SCUK FC serui dock SCL SPI serial dock SCUK Manage IMU MIT Media Lab E14 274 24 SDA7SDI PC serai data SOA SPI seal data input 500 75 Amherst Street w NC No Connect pins Do not connect Size Letter Number Revision Cambridge MA 02139 Tabie 10 Signal Descriptions Date 2015 04 08 Time 12 52 47
45. no optimizations Function Time us Time ext us motor_position_pid 6 6 11 55 motor impedance encoder 6 4 112 rgb_led_ui 6 6 1155 filter_adc 5 16 9 03 strain_filter_dma 2 84 4 97 unpack payload 485 1 17 48 30 59 motor current pid 5 78 10 115 Sum 50 86 89 005 The motor current pid function at 10us safety factor included can be problematic When it s called at 20kHz it consumes 2096 of the computing power available A manual optimization of the function was done minimized the number of function calls unified the safety checks and 83 the timing was reduced from 5 8 to 4 2us With the optimizations enabled and the use of an inline function the execution time dropped 1 42us 2 8 of the computing budget 100 5 timer is used as the main time base In the main while loop all the functions that are not purely interrupt driven are called based on that timer Time us Category Function Refresh Hz O 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 500 510 520 530 540 550 Gyroscope 250 12C Accelerometer 250 Safety CoP 250 Strain 1000 DelSi Averaging 1000 pwm PWMISR 100000 NN um K gt m E s SAR DMA ISR 20000 Figure 65 Visual representation of the function timings The following code details the time sharing strategy implement
46. of a Self Contained Anthropomorphic Transfemoral Prosthesis IEEE ASME TRANSACTIONS MECHATRONICS VOL 14 NO 6 DECEMBER 2009 E J Rouse L M Mooney E C Martinez Villalpando H Herr Clutchable Series Elastic Actuator Design of a Robotic Knee Prosthesis for Minimum Energy Consumption 2013 IEEE International Conference on Rehabilitation Robotics S Hodges N Villar J Scott A Schmidt A New Era for Ubicomp Development IEEE Pervasice Computing Vol 11 Issue 1 January March 2012 Y A Badamasi The Working Principle Of An Arduino 11 International Conference on Electronics Computer and Computation ICECCO 2014 Abuja A Y Benbasat S J Morris J A Paradiso A Wireless Modular Sensor Architecture and its Application in On Shoe Gait Analysis IEEE Sensors Conference Toronto Canada October 22 24 2003 Y Meng K Johnson B Simms M Conforth A generic architecture of modular embedded system for miniature mobile robots 2008 IEEE RSJ International Conference on Intelligent Robots and Systems Nice France Sept 22 26 2008 A O Nursal Modular embedded system design for mechatronic education 2010 IEEE ASME international conference on mechatronic and embedded systems applications Qingdao ShanDong 15 17 July 2010 R J Mitchell J B Grimbleby R J Loader C Kambhampati Modular embedded system for teaching real time control International Conference on Contro
47. photons The span between these two extremes is divided is layers Open Systems Interconnection model OSI is composed of 7 layers OSI Model Layer Data unit Function Examples S HTTP SMTP ASCII EBCDIC JPEG Host layers IPv4 IPv6 IPsec AppleTalk layers PPP IEEE 802 2 L2TP DSL USB Figure 62 OSI model 18 http en wikipedia org wiki OSI_model 77 While the OSI model can represent systems as complex as Internet for embedded applications it is possible to simplify by merging layers 4 through 7 into a single Application layer With a limited need for packet routing layer 3 Network is absorbed by layer 2 Data link 4 1 1 Application Layer At the highest abstraction level intelligent information is exchanged between different FlexSEA boards without any regards for the physical media used The list of commands available to the user is presented in Table 10 Table 10 List of FlexSEA Commands Command Details ping Ping Ping status Board Status reset Reset ack Acknowledge mem Memory acqui Acquisition strategy rs485_config RS485 Configuration usb_config USB Configuration usb_write USB Write temp Temperature switch Switch imu IMU encoder Encoder strain Strain gauge load cell strain_config Strain Gauge amplifier gain amp offset volt Voltage measurements b
48. should see a new network connection and or a storage device 3 Open a terminal and connect to the BBB ssh beaglebone local root 4 On your host navigate to Code flexsea_1_O misc scripts official BBB in your SVN folder 5 SCPthe 3 scripts and the DTS file to the BBB scp config bbb 1 config bbb 2 flexsea bbb init BB SPIO 01 00A0 dts root beaglebone local 6 On the if you Is you should see the 3 scripts and the DTS file 7 We need to change the permissions chmod 755 config bbb 1 config bbb 2 flexsea bbb init 2 Configuration first part 1 In the BBB terminal call the first script with config bbb 1 enter flexsea twice when prompted for a password 2 Inthe Adafruit lib install say Yes when prompted 3 nano will open uEnv txt Paste that line capemgr enable partno BB SPI0 01 Ctrl X to save Y then Enter 199 3 Reboot command reboot After few seconds you ll loose the connection then it will come back to life 4 Connect to the BBB ssh beaglebone local root enter flexsea as the password 5 Configuration first part 1 config bbb 2 6 Configuration complete you are now ready to use the BBB 1 To enable SPI and move to the Desktop call flexsea bbb init 2 You ll get the message FlexSEA is ready to be used To test you need to send a plan program See Using a pre configured BeagleBone Black Plan board skip the Connect section Copy of the scripts config bbb 1 Z bin bash Configur
49. to date code Programming FlexSEA Execute 0 1 Connect to the Plan board Connecting to the Plan board BBB transfer the latest Plan code Transferring a program to the Plan board BBB Call plan execute 1 stream The RGB LED will turn green on Manage and on Execute Stream is currently tweaked for the ShuoBot Exoskeleton it will soon be generalized it will display all the sensors that she needs 208 in 1070 62 Encoder 9998 You can move the board and observe the IMU values changing Ctrl D to quit The code isn t 100 stable yet If the LED is Blue while Stream is running something is wrong Either reprogram Manage or power cycle it and it should be fine Transferring a program to the Plan board BBB 03 15 2015 While it s possible to compile your code on the BBB it is not the most efficient way of working Cross compiling on the Host is a lot faster but it means that we need to transfer the executable from the host to the BBB jai Open a new terminal tab enter cd Desktop FlexSEA biomech ee svn Code flexsea_1_0 plan 2 Depending on what you compiled for you ll have different Release_x folders Navigate to the one you want to use In it you ll find your executable 3 We use Secure copy scp to transfer files To send plan to the desktop of the BBB use scp plan root beaglebone local home debian Desktop 1 If you need to get plan from the BBB reverse operation use scp root beaglebone
50. with G 1 Ruse Rso assuming that Russ could take a value of practice the lowest resistance is the wiper s resistance While the typical value is 75 ohms it can go as high as 300 ohm Ro is 1 resistor Ryap Guin 1 U3B MINI 1 3009752608 1 303 9 20 minimum gain measured the Manage 0 1 boards was 1 21 For application requiring a lot of precision a calibration will be required 5 2 2 Power Multiplexer and Linear Regulator Load Test FlexSEA Manage was powered from its Plan connector 5VP at 5V The voltage was measured after the TPS2111 on the 5V net with a Tektronix MDO3024 oscilloscope The STM32F4 was running application code 8500 programmable load was connected in parallel to the circuit In all the tables below the current is the current programmed on the load not the true total current total current is higher than the load current because of the current used by the circuit After the 5V multiplexer was tested the programmable load was connected to 3V3 Again the circuit was not disconnected the current is higher than what s displayed 118 Current mA 5V V 0 4 945 100 4 900 200 4 853 300 4 800 400 4 755 500 4 700 600 4 655 700 4 609 800 4 554 900 0 500 1000 Current mA 3V3 V 0 3 303 100 3 303 200 3 297 300 3 292 400 3 292 500 3 292 600 3 289 700 3 281 800 3 281 900 0 500 1000 6 000 5 000 4 000 3 000 2 000
51. you try apt get install ia32 libs follow Hertaville if you need to do this Alternatively try to install ia32 libs and follow what the terminal tells you Update bash 186 Open the file with nano bashrc Add this line at the end export PATH PATH home flexsea Desktop FlexSEA embedded arm gcc arm none eabi 4 9 2014g4 bin Update bash with source bashrc Test your installation with arm none eabi gcc v You should see a big chunk of text that ends with gcc version 4 9 3 20141119 release ARM embedded 4 9 branch revision 218278 GNU Tools for ARM Embedded Processors e OpenOCD to debug and program the STM32 get info follow same Hertaville tutorial as for Get the sources for 0 8 0 http sourceforge net projects openocd files openocd Extract to FlexSEA embedded arm You ll get a new directory home flexsea Desktop FlexSEA embedded arm openocd 0 8 0 We can now install OpenOCD Dependencies sudo apt get install git zlib1g dev libtool flex bison libgmp3 dev libmpfr dev libncurses5 dev libmpc dev autoconf texinfo build essential libftdi dev libusb 1 0 0 dev Navigate to openocd 0 8 0 and call configure enable maintainer mode enable stlink prefixz home flexsea Desktop FlexSEA embedded arm openocd bin make make install You will get a new directory home flexsea Desktop FlexSEA embedded arm openocd bin Modify the USB rules
52. 0 0 eene nennen enne 47 Figure 28 PSoC Programmable Analog Blocks Strain Gauge Amplifier 47 Figure 29 Clutch driver schematic nennen nhan 48 Figure SO IMU schemiatiG eedem etr mete EE enne eene Ip Q si nete d agn 51 Figure 31 External I O protection circuit ener ener eene nnne 51 Fig re 32 EXPANSION 6 OnneCtU r uu a etes eee oti tna abe Lern 52 Figure 33 04 004 ESD Clamping a a 53 Figure 34 ESD diode routed right under the Expansion connector 53 Figure 35 RGB LED and Green heartbeat LED 54 Figure 36 USB ESD exa Edo eda acd 54 Figure 37 USB protection routing au aqa tastes sess na suat 54 Figure 38 Power Supplies Schematic esses enne enhn 55 Figure 39 Brownout protection 56 Figur 40 10V 500m SMPS hei dete dan tee aee dept ect fes 58 Figure 41
53. 060 Figure 84 Load testing constant current Vas 4 865V 4 317V Load regulation 100 NLD MAX L04D 100 12 69 Vuax LoAD 4 317V Eq 19 Same conclusion as for the 10V power supply the PTC is too resistive A conservative specification for peripherals attached to the Expansion connector will be 200mA at 5V 5 1 4 Safety Features Safety code such as the over temperature protection and the battery disconnection detection runs on the Safety Cop MCU Special test code was used in the main while loop to test the limits of the system Due to the limited number of IOs available the ELED Error LED output was used as the output flag signal For all the analog measurements temperature and voltages Channel 4 Green is connected to ELED while Channel 2 Blue is connected to parameter being measured 5 1 4 1 Watchdog Clock As explained in Section 3 1 2 PSoC 4 Safety Co Processor a digital clock line links the two microcontrollers The PSoC 5 is in charge of generating the clock and the PSoC 4 Safety CoP measures the time between transitions If the code hangs in an interrupt or in a function the WDCLK line won t toggle quickly enough a sign that the software is not behaving as expected and that safety actions need to be taken 110 The pulse width measurement is done in hardware as detailed on Figure 85 BasicCounter_1 Edg eDetect_1 clk_200kHz Control_Reg_1 200 kHz
54. 1 Use RX12 amp TX12 Ful 1 2 Transmit on TP1 TX12 receive on TP2 RX12 Synchronous Full 1 2 3 Transmit TP1 12 receive on TP2 RX12 clock Note For port 2 replace RX TX 12 45 and use TP4 to 6 Figure 23 RS 485 Modes synchronous asynchronous half or full duplex Three transceivers allow the user to select between three modes asynchronous half duplex asynchronous full duplex and synchronous full duplex The trade off is between simplicity and data transfer speed The PSoC 5LP UART module can be configured for 8x or 16x oversampling and has a maximum baud rate of 4Mbits s The Master Clock is 80MHz and we can only use fractional dividers Using 8x we can calculate the baud rate versus the clock divider Table 3 Baud rate versus clock divider Divider Baud rate Comment 1 10M Over 4M invalid 2 5M Over 4M invalid 3 3 33M 4 2 5M 5 2M 43 The baud rate selected on FlexSEA Execute has to be closely matched with the baud rate selected on FlexSEA Manage baudratewanage fcuk 8 2 OVER8 USARTDIV Eq 2 fuk is 84MHz and OVERS is 0 for 16x oversampling USARTDIV fc g 16 baudrate Eq 3 In the STM32 register the fractional part of USARTDIV is stored in 3 bits 8 possible values The fractional part has to be a multiple of 1 8 0 125 Different values have to be approximated thus introducing averaging e
55. 11 Eq 4 PDswircHInG Cass Vin fow loap leare Eq 5 Where 174mA Vour ViN D 10V 24V 0 42 Rps oN 0 315 Q worst case Cass 19pF Vin 24V fsw 20kHz Igate 10 9mA We obtain PDpgsistive 4mW amp PDswrrcuiNG 3 49mW The total power dissipation is 7 5mW If the clutch is powered at 24V 10W no switching the dissipation will be 55mW The thermal resistance of the SuperSOT 3 package from junction to ambient is 270 C W C Eq 6 1 Based on http electronicdesign com boards calculate dissipation mosfets high power supplies 49 3 1 6 2 Level shifting A pre biased NPN BJT RN1106MF and two resistors are used to allow one 0 5V microcontroller output to turn on and off the P MOSFET The battery voltage can span from 15 to 28V Vas is determined by the ratio of R32 and R33 by the saturation voltage Vcr sar of the BJT 0 3V max Vct sar being less than 2 of the minimum voltage it is negligible Ves Vp 1 R33 R33 Rs2 0 5 Eq 7 Vp ranging from 15 to 28V VGS will be from 7 5 to 14V below the maximum of 20V and high enough to provide a low Rpsow 3 1 7 IMU Accelerometer and gyroscope are commonly used for the control system of prostheses and exoskeleton They are used to measure angular velocities angles and impacts The MIT CSEA Knee 2 used a sensor board populated with an ADXL345 accelerometer 3 axis 2 to 16g and an ITG 3200 gyroscope 3 axis 2000
56. 15 16 19 dee ils 29 luF 100nF 100nF 100nF 100nF 100nF 100nF GND GND GND GND GND GND GND DC OPT PU FH19C 6S 0 5SH 05 as 46 47k HK 22 Biomechatronics Tue Execute PSoC5 MIT Media Lab E14 274 p T 75 Amherst Street mi Sis Letter Number Revisions Cambridge MA 02139 l media Date 2015 03 05 Time 12 2858 Sheet of USA lab File BIOM FLEXSEA EXECUTE 0 1 PSoCS SchDoc 8 140 3V3 SUSESISS WN Re CY8C4245LQI 483 GND CY8C4245LQI483 U8A zz 333 aous u n g 3 3 CY8C4245LQI 483 PL 4 PL CY8C4245LQI 483 USE 32 33 I 1 U8F CY8C4245L 42451 01 483 E 22 vcc 22 B NA 58 luF GND GND 45y 5 5 23 FHI9C 68 0 5SH 05 LNJ247W82RA GND 59 60 luF 100nF GND GND GND Biomechatronics Tile Execute Safety CoP ise eh ede eee TER 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 l media Date 2015 03 05 Time 12 28 59 Sheet of USA lab File BIOM FLEXSEA EXECUTE 0 1 Safety CoP SchDoc 3 141 Execute 3x RS 485 MIT Media Lab E14 274 se 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 l media 3V3 SN65
57. 32 0 39 39192 32 0 39 39192 3 39 39192 3 39 39192 3 21 39 39192 3 1350 148 1350 148 1349 150 1349 150 2 2 2 2 0 2 0 0 2 0 0 2 0 0 2 0 0 2 0 0 2 0 0 2 0 0 0 2 0 0 0 2 0 0 0 2 0 0 0 Get Help WriteOut Read File Prev Page Cut Text Cur Pos Exit ae Justify Where Is Y Next Page WH UnCut To Spell Figure 99 Data logging with the Log application Figure 99 shows the Log interface on the left and the log file on the right The date and time are not adjusted on the Plan board but they can be used differentially 57 39 18 seconds 13844 lines in 18 seconds is 769Hz Each line stores the equivalent of 16 bytes for a total of 98kbits s 15x higher than the criteria 127 6 Application test cases 6 1 Clutched Series Elastic CSEA Knee The original electronics of the MIT CSEA Knee 2 11 was replaced an early prototype of FlexSEA in 2014 The main goal was to test the electronics and prepare the knee for future experiments In 2015 the latest generation FlexSEA was integrated in the knee It has been used as a demonstration project and as atest bench for control algorithms such as the impedance controller The system has one degree of freedom and uses all 3 FlexSEA boards Inputs e Incremental encoder e Hall effect e Analog angle sensor e Analog force sensor Figure 100 CSEA Knee wit
58. 35 Figure 14 H Bridge GIF au L a nu u u D a 36 Figure 15 MOSFET vs IGBT when to use 36 Figure 16 Half bridge on Execute 1 of 3 OR corda 37 Figure 17 The channels use the same compact layout B highlighted 39 Figure 18 Spice simulation 20A motor current sensing 40 Figure 19 Shorted leads protection implemented with depletion mode MOSFETS 41 Figure 20 Shorted leads protection negative voltage generation and gate control 41 Figure 21 Spice simulation voltage inverter a 42 Figure 22 One of the 3 RS 485 transceivers present on FlexSEA Execute 43 Figure 23 RS 485 Modes synchronous asynchronous half or full duplex 43 Figure 24 TINA TI Spice simulation of the two stage differential amplifier design 45 Figure 25 CMRR vs Frequency TI INA331 2331 instrumentation amplifier 46 Figure 26 Input filtering and protection 46 Figure 27 Two stage 0
59. 38 Power Supplies Schematic Table 5 Power Supplies Symbol Voltage Source Details VB 15 28 typ 24V Battery Battery voltage VG 10V VB Gate driver voltage input for low voltage regulators 5V 5V VG Logic supply almost everything 3V3 3 3V 5V Logic supply RS 485 amp IMU 3 1 10 1 Brown out protections When turned on inductive loads such as motors will draw a current that is only limited by their equivalent series resistance This current can be extremely high because the resistance is kept to a minimum to limit thermal losses During such events it is important to keep the control electronics powered To prevent those currents from stealing energy from the logic power supplies we use a simple circuit consisting of a diode and a capacitor 55 Vin Vout GND Figure 39 Brownout protection Vin is the input voltage that would normally go to the next circuit Instead the diode prevents the input filter capacitor from being discharged by anything else than the current on Vout The capacitor can be sized to provide a sufficient energy reserve to keep the output voltage regulated when the bus voltage drops The diode decreases the efficiency of the power supply Using a Schottky with a small voltage drops keep the losses to a minimum Efficiency loss for a theoretical circuit that converts from 24 to 12V with 100 efficiency with a 500mA load on its output 6W Vin 24V Vprop 24V 0 5V 23 5V
60. 96 4 4 FlexSEA Plan The FlexSEA Plan software is written entirely in C to maximize portability and efficiency Its main features are e Can be cross compiled for embedded computers or natively compiled for ease of debugging e Supports the full FlexSEA Network communication stack e Interfaces to the network via SPI only when cross compiled e Can be used as a terminal application e Can be interfaced with high level code e Can display and log data in human readable formats The Eclipse project is configured to offer 3 compilation options Release Single Release Multiple and Debug Debug uses the native GCC compiler to generate code that can be tested on the host computer All the SPI functions are disabled Release Single is used for C applications and Release Multiple is used to interface with other programming languages 4 4 1 Displaying and logging data In Stream mode Plan will display sensor values on the terminal The refresh rate is limited to tens of Hertz by the time it takes to write data on the terminal printing less data will allow a faster refresh rate Stream should only be used to test a system not in a final application Figure 74 Streaming sensor values 97 Similar to Stream Log will save data in a text file rather than displaying on the terminal This writing operation is much faster speeds north of 500Hz can easily be obtained Figure 75 is an example of multi
61. APB1 48MHz With a 84MHz clock the two USARTs can achieve baud rates up to 10 5Mbits s 74 3 2 8 Power The Manage board requires 5V It can be provided by the Plan board or by an external supply connected to the Plan connector or via the USB connector An autoswitch power multiplexer is used to select the power source When 5VP from the Plan connector is available it is used Using USB power is useful for simple tests and debugging when an external supply is not available 5VP 5VU V 5V 3V3 1 MBR0580 TP U7 TPS73733 R40 393 7 R4I 2 T iotr EY GN GND GND GND GND GND GND GND Figure 61 Autoswitch Power Mux and 3 3V LDO Regulator 2619 luF GND A TPS73733 linear regulator is used to obtain 3 3V from 5V As shown on the schematic note its junction temperature shouldn t rise above 115 C in the absolute worst case scenario To test the autoswitching feature the Manage 0 1 board was powered from an external supply and from USB The yellow trace is 5V the blue trace is 3V3 The external power supply was turned off and the event was caught by the oscilloscope triggering on a negative slope at 4 75V 75 3 2 9 Future Work and Circuit Modifications List of modifications for the next hardware revision e When hot plugged the STM32 doesn t not always properly power on Evaluate the use of a power sequencer e The 2 power outputs have tiny di
62. Amplifier Force Calibration The same amplification circuit was used on another Biomechatronics project the FitSocket Figure 78 shows a force calibration test A brushed DC motor 20kHz PWM is compressing linear spring and the resulting force is measured with the strain gauge Force Calibration Test y 0 0022x 16 422 R 0 9928 Force N 9700 10700 11700 12700 13700 14700 15700 16700 17700 16 bit analog voltage reading Figure 78 Force calibration test on the FitSocket 5 1 3 Power Supplies 5 1 3 1 Preliminary qualification Upon reception of the first assembled FlexSEA Execute 0 1 boards a global power supply test was made A lab power supply was connected to VB with a current limit of 100mA and an initial voltage of OV The voltage was ramped up slowly while voltage measurements were taken with 106 a Fluke 189 digital multimeter The microcontrollers were not programmed and nothing was connected to the Expansion connector Table 16 summarizes the results Table 16 Preliminary power supply test VB V VG V 5 V 3V3 V Comments 5 000 0 128 0 131 0 310 VB LED slightly ON 7 020 5 483 4 945 3 379 All the LEDs turned ON shortly after 6V 10 010 7 585 4 944 3 378 15 030 9 906 4 944 3 378 25 090 9 915 4 944 3 378 All the LEDs are ON equal brightness 5 1 3 2 10V SMPS Load Testing Mean Y Figure 79 500mA load DC 2V d
63. Communications and networking 77 4 1 1 Application Layer a 78 4 1 2 Data link MM 80 4 1 3 Physical TR 81 4 1 4 Receiving comnaands He T 81 4 1 5 Hierarchy ayka D PS bum aa aa ku i uH 82 4 1 6 Special Command Sres Ue ese 82 43 LS Ou S 82 4 2 1 Organization and timlngs u inte EUER IEEE 83 4 2 2 BLD COMMUTALION d n e et eai ett esee hg cone ede 86 4 2 3 Dos da 90 4 2 4 Impedarice controll r i et eap de eai 94 4 2 5 X Trapezoidal trajectory generation 95 4 3 BlexXSEA M nage iine eet ee Eie etnies etm 96 4 4 u oet ro e OO Mn aR 97 4 4 1 Displaying and logging data 97 4 4 2 High level state machine in C os eoe o segete tne earnest roe nb ep Dea 98 4 4 3 Interfacing with higher level languages
64. File BIOM FLEXSEA EXECUTE 0 1 Clutch SchDoc 3 151 5V TPD4E004DRYR TPD4E004DRYR TPD4E004DRYR TPD4E004DRYR lt a DI4B 7 D7D 5V 102 TPD4F004DRYR TPD4E004DRYR TPD4E004DRYR TPD4E004DRYR E 8 z S E amp DI4D D7B D7A D8B D8A GND itv 103 104 TPD4E004DRYR TPD4E004DRYR ES E D8C D8D DI0C D10D GND 152 g ES 5 za za GND GND ie Biomechatronics Title Execute Protection MIT Media Lab E14 274 2 TNR 75 Amherst Street mit SNP E Revisions Cambridge MA 02139 media Date 2015 03 05 Time 12 28 58 Sheet of USA File BIOM FLEXSEA EXECUTE 0 1 Protection SchDoc 1 2 3 4 10 3 Manage Schematic IMU BIOM FLEXSEA MANAGE 0 1 IMU SchDoc FLASH BIOM FLEXSEA MANAGE 0 1 FLASH SchDoc 105 BIOM FLEXSEA MANAGE 0 1 IOs SchDoc Plan BIOM FLEXSEA MANAGE 0 1 Plan SchDoc STM32F4_A FLEXSEA MANAGE 0 1 STM32F4 A SchDoc Ur BIOM FLEXSEA MANAGE 0 1 UI SchDoc RS 485 Power BIOM FLEXSEA MANAGE 0 1 Power SchDoc RS485 A4 BIOM FLEXSEA MANAGE 0 1 RS 485 SchDoc RS485 AI RS485 RS485 A2 RS485 B2 RS485 A3 RS485 B3 RS485 A4 RS485
65. FlexSEA Flexible Scalable Electronics Architecture for Wearable Robotic Applications by Jean Fran ois Duval B Eng Electrical Engineering Universit de Sherbrooke 2012 Submitted to the Program in Media Arts and Sciences School of Architecture and Planning In partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology June 2015 Licensed under Creative Common Attribution NonCommercial ShareAlike CC BY NC SA 2015 Jean Francois Duval Signature of Author Program in Media Arts and Sciences May 8 2015 Certified Hugh Herr Ph D Associate Professor of Media Arts and Sciences Thesis Supervisor Accepted by Prof Pattie Maes Academic Head Program in Media Arts and Sciences FlexSEA Flexible Scalable Electronics Architecture for Wearable Robotic Applications by Jean Fran ois Duval Submitted to the Program in Media Arts and Sciences School of Architecture and Planning on May 8 2015 in partial fulfillment of the requirements for the degree of Master of Science Abstract The work of this thesis aims to enable the fast prototyping of multi axis wearable robotic systems by developing a new modular electronics system The flexible scalable electronics architecture FlexSEA developed for this thesis fills the void between embedded systems used in commercial devices and in research prototypes This system provides the required hardware
66. HVD75 GND 33V3 1 o O B s Du 7 SN65HVD75 GND 33V3 3V3 3V3 3V3 100nF 100nF 100nF 142 Biomechatronics Date 2015 03 05 Time 12 28 59 Sheet USA File BIOM FLEXSEA EXECUTE 0 1 RS 485 SchDoc 1 2 3 4 REPEA T HalfB 1 3 BIOM FLEXSEA EXECUTE 0 1 Half Bridge SchDoc Shorted Leads BIOM FLEXSEA EXECUTE 0 1 Shorted Leads SchDoc a 3 TPD4E004DRYR R TPD4E004DRYR DISA FA TPD4F004DRYR DISD DISC 143 Biomechatronics Execute BLDC MIT Media Lab E14 274 es T 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 L media Date 2015 03 05 Time 122857 Sheet of USA lab File BIOM FLEXSEA EXECUTE 0 1 BLDC SchDoc 2 3 4 MBR0580 TP IRS21867 GND VB GND VB 4VG C42A Mm 100nF luF luF 100nF GND GND GND Execute Bridge Size Letter Number Revision Date 2015 03 05 Time 12 28 57 Sheet of Biomechatronics MIT Media Lab E14 274 75 Amherst Street Cambridge MA 02139 USA File BIOM FLEXSEA EXECUTE 0 1 Half Bridge SchDoc 3 144
67. Lob m 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 media Date 2015 04 08 Time 12 52 47 Sheet USA File BIOM FLEXSEA MANAGE 0 1 Plan SchDoc 1 2 3 4 3 4 45y vs MBROSSO TP 38 39 16k 8I 4 lt Vsns Tlim on amp 4 45 100nF 100nF GND GND GND Tite Manage Power ag MIT Media Lab E14 274 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 jia Date 2015 04 08 Time 125247 Sheet of USA lab File BIOM FLEXSEA MANAGE 0 1 Power SchDoc 3 161 81 LNJ347W83RA DII GND D12 33V3 ea Lt lt s a z a 3V3 pc TPD4E00SDRYR GND GND DI3 TPD2EUSB30DRTR Title Manage UI Biomechatronics MIT Media Lab E14 274 Wm 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 l media Date 2015 04 08 Time 12 52 48 Sheet of USA lab File BIOM FLEXSEA MANAGE 0 1 ULSchDoc 3 162 3 4 13 100nF GND Biomechatronics Title Manage FLASH MIT Media Lab 14 274 M 75 Amherst Street
68. M cycle Figure 67 FlexSEA Execute Motor Control PSoC Diagram The look up table is registered with the PWM edge to avoid transitions from happening in the middle of a PWM cycle when the Hall code is changed in such an event the dead time would not apply The 6 PWM outputs were connected to a logic analyzer while the motor was spinning to confirm the validity of the table Figure 68 PWM signals rotating BLDC motor Brushless motors such as the Maxon EC 30 commonly used in wearable robotics have low inductance and resistance 48V version phase to phase 65 3uH 0 3860 89 1 t pe al V t dt Eq 14 We can calculate the current rise per us at 24V 1 115 I 24V dt 850mA j Eq 15 Motor drivers typically use 20kHz PWM just above the audible spectrum At 95 duty cycle a pulse is 47 55 long allowing the current to ramp up by 40 375A At 100kHz the PWM resolution is reduced from 12bits to 9 65bits but the current rise is limited to a much safer value 8A 4 2 3 Current controller The hardware implementation is presented in Figure 18 and Figure 67 The PWM2 output has a rising edge in the middle of the PWM1 pulse that is used to start the ADC conversions ensuring that the sampling is done far from the transitions and at a constant timing The SAR ADC is programmed to generate a DMA transfer every 5 samples 100kHz PWM 20kHz DMA interrupt rate In the ISR the last 5 samples are aver
69. Maxon EC 30 used in this experiment The 5 look up table LUT component supports a maximum of 5 inputs and 8 outputs The 3 Hall sensors and the 2 PWM phases use all the inputs the Direction signal to change from clockwise to counter clockwise rotation cannot be integrated in the table Table 14 shows the relation between the input signals and the output signals MUXO and MUX1 are used for the analog multiplexer that controls the current sampling 87 Table 14 4Q BLDC Commutation Table Q5 04 03 Q Q1 OutHex Shoot 06 z 2 x 5 gt PHI PH2 H3 H2 Hl Table 15 presents a second LUT used to control the direction of the rotation Table 15 Hall Sensors amp Direction HA Out Hex HB 2 88 The complete system can be seen in Figure 67 Motor control ADC_SAR_2 Syn isa isr_dma 2 vref_out P fe EXP3 BUS CLKHUL VDAC8_1 B0 MHz 0 ADC CLK nunj MASTER CLK 6 LUT HALL DIR AOP OUT f PWMH1 AMuxHw 1 PWML 1 CS1 sj R1 PWMH2 52 5 AN f PWML2 CS3 xj 10K i imn PWMH3 P AOP_IN f j PWML3 BUS cLKg U E 80MHz Q 1 MotorDirection currmux 1 currmux 1 0 gt EdgeDetect_1 EdgeDetect_2 d det d det gt e Register PWM outputs with L phase edges to avoid BUS BUS_CLKBUU p clock p clock weirdness when Hall changes in the middle of a PW
70. RGB LED will be green for a few seconds then blue LEDO will blink Programming FlexSEA Execute 0 1 03 19 2015 Important if your board has never been programmed if you have 4 steady green power LEDs ON and nothing else no flashing red LED you need to follow this first Preparing the FlexSEA Execute 0 1 board Software Open the execute project in PSoC Creator Code flexsea_i_0 execute execute cywrk Open main h and make sure that the modules you want are enabled Enable Disable sub modules define USE RS485 define USE USB 206 define USE_COMM Requires USE RS485 and or USE USB define USE 1 define USE TRAPEZ USE DIETEMP define USE I2C INT define USE I2C EXT define USE IMU Requires USE I2C INT define USE STRAIN Requires USE I2C INT Build the code Release mode Connect the FFC to Execute leftmost connector as viewed from the top Click Program Programming started for device PSoC 51 CY8C5888AX LPO096 Device ID Check Erasing Programming of User NVL Succeeded Programming of Flash Starting Protecting Verify Checksum Device PSoC 5LP CY8C5888AX LP096 was successfully programmed at 03 17 2015 14 59 09 After a few seconds the RGB LED should be Blue a green LED should be flashing and the red LED should be gently pulsing as an indication that both PSoC are work
71. S MISO SPI4 MOST SPI4 SCK B PWROUTO B PWROUTI SPI5 NSS SPIS MISO SPIS MOSI DIO0 SDA2 DIOI SCL2 8pF 2MHz C C 3l 1 1 18pF GND GND GND 33V3 33V3 33V3 3V3 33V3 33V3 3V3 3V3 3V3 33V3 33V3 3V3 3V3 38 39 40 41 L 1 T 106 47 48 I I ir 1000F 100nF 100nF 100nF 100nF 100nF 100nF 100nF 100nF 100nF 100nF 100nF 2u2F 2u2F FH19C 6S 0 5SH 05 GND GND GND GND GND GND GND GND GND GND GND GND GND 154 Biomechatronics Title Manage STM32 MIT Media Lab E14 274 Iu 5 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 l media Date 2015 04 08 Time 12 52 48 Sheet USA lab File BIOM FLEXSEA MANAGE 0 1 STM32F4 SchDoc 1 2 3 4 33V3 SN65HVD75 SN65HVD75 Sa 7 D vec gt DE GND vce m Ja mm 4 24 GND 3N3 3V3 sN6sHVD75 vi SN65HVD75 RO gt OM gt 7 R50 RE S E aTe 120 DE 2 8 DI GND GND 3V3 3V3 5 SN65HVD75 114 SN65HVD75 1 e 7 R52 EREITEN OE 120 B A 3 A 8 i N GND GND 3V3 43V3 3 33 43V3 Asynchronous Transmit and receive on TP1 Use RX12 amp TX12 Asynchron
72. a high power transistor such as an IGBT or power MOSFET Gate drivers can be provided either on chip or as a discrete module In essence a gate driver consists of a level shifter in combination with an amplifier The IRS21867 was selected because of its robustness especially for its tolerance to negative transient voltages For the MOSFETs the QFN 5x6 package also known as 8 PowerTDFN and PG TDSON 8 was selected for its small size its wide industry acceptance and the convenience of doing bottom cooling BSCO14NO6NS MOSFETs were selected for their availability price low Rpsou and low gate capacitance As a safety margin MOSFETs rated for at least twice the bus voltage 28V Max were selected At 60V the BSCO14NO6NS are protected in case of really bad inductive spikes The R1 and R2 gate resistors were selected from what could be called an educated arbitrarily decision as a compromise value between fast switching and slow switching Switching too slowly can introduce shoot through and increase switching losses while switching too fast can increase the transient voltages generated can lead to more noise and to component destruction in extreme cases The efficiency of the motor driver can be augmented by carefully selecting gate resistors and by doing a careful selection of semiconductors but this optimization is outside of the scope of this work R27 is used for current sensing http en wikipedia org wiki Gate
73. a large computer in the network The cables connectors and special ASICs required for EtherCAT add to the cost volume and complexity of the system With the relatively small number of nodes on a typical Biomechatronics project less than 8 a simpler and slower interface can be used RS 485 is often associated with old technology but its simplicity low cost robustness and speed in theory up to 100Mbps 20Mbps achievable in our application makes it an appealing option for FlexSEA 2 5 3 Communication software custom communication protocol was developed for this project It is used for the Plan Manage interface for the Manage Execute interface s and with the onboard USB The hardware layer can be modified as long as it can deliver bits from point A to point B the system will be transparent to the changes To avoid conflicts and to simplify the system the communication is 23 highly hierarchical The Master always initiates the transfer It can request a Read from a Slave Slaves will only emit after a Read request was received All the details are in section 4 1 Communications and networking 2 5 4 Software FlexSEA Plan FlexSEA Manage and FlexSEA Execute have three different microcontrollers microprocessors but they all have to communicate together To simplify the development all the controllers are ARM based GCC is used as the compiler and a set of common code is shared by the three software projects All the details
74. able 1x Plan Manage cable Plan Manage Cable 1x Manage programming cable Prog Adapt 0 1 for FlexSEA Manage 0 1 Step 1 Plug the Plan Manage cable to both the Plan and the Manage boards Step 2 Power the Plan board with the USB Mini B cable The 3V3 and 5V LED on Manage will light up 176 Connecting to the Plan board BBB 03 19 2015 1 Connect the BBB to your host computer with a USB Mini B connector If you power a lot of peripherals on Manage and or if you use WiFi you ll need more power than what USB can provide In that case connect a wall adapter to P1 2 Make sure that it s connected to your VM In the VMWare top menu you can see the list of attached peripherals under VM gt Removable Devices 3 After a few seconds it should appear as a new network device 4 Open terminal and type ssh beaglebone local root 5 1 When asked for a key say yes to add it to the list of known hosts 2 Ifthere is a key conflict will happen if you use multiple BBB use the key removal command that s in the error message 6 Use the configuration script by typing flexsea_bbb_init Please not that you can hit Tab after you typed f and it will auto complete for you 1 The terminal prompt will now be root beaglebone home debian Desktop 2 Alternatively if you do not want to use the script or if it doesn t work you can call 7 1 1 home debian Desktop 2 echo 5 0 01 gt sys devices bone capemgr
75. aged and the current controller function is called PI Current controller 2 speed optimized wanted curr amp measured curr are centered at zero and are in the SPAN range The sign of wanted curr will change the rotation direction not the polarity of the current I have no control on this inline int32 motor current pid 2 int32 wanted curr int32 measured curr volatile int32 curr p 0 curr i 0 volatile int32 curr 0 int32 sign 0 int32 uint wanted curr 0 int32 motor current 0 int32 shifted measured curr 0 90 Clip out of range values if Wanted curr gt CURRENT POS LIMIT wanted curr CURRENT POS LIMIT if wanted curr lt CURRENT NEG LIMIT wanted curr CURRENT NEG LIMIT ctrl current setpoint val wanted curr Sign extracted from wanted curr if wanted curr lt 0 sign 1 MotorDirection Control 0 uint wanted curr wanted curr else sign 1 MotorDirection Control 1 uint wanted curr wanted curr At this point uint wanted curr is always a positive value This is our setpoint From ADC value to motor current shifted measured curr measured curr CURRENT ZERO if shifted measured curr CURRENT ZERO We are driving the motor Q1 or Q3 motor current CURRENT ZERO shifted measured cu
76. an appropriate embedded system solution had a direct impact on the system design and performance 2 11 After reading papers grant reports and interviewing wearable robotic designers the following list of general system problems and reasons justifying new designs was compiled e Lack of reliability Lack of processing power overloaded microcontroller e The original designer left the laboratory e No electrical engineer on the team e Slow communication peripherals e Can only support brushed motors e Can only support one motor 15 Commercial motor driver has to be tricked into running a special control loop no built in functionality e Power consumption e Size mechanical integration issues These problems are shared by many researchers in related fields such as humanoid robotics and wearable computers therefore many designers and companies have attempted to design a unified embedded system that could be used in a broad range of projects Commercially available modular hardware platforms include the Microsoft NET Gadgeteer system an open source toolkit for building small electronic devices using the NET Micro Framework 3 the popular Arduino and its Shields Shields are boards that can be plugged on top of the Arduino PCB extending its capabilities the BeagleBone Black embedded computer with the Capes and the Intel Edison with the Blocks SparkFun popularized the use of breakout boards minimalist c
77. and will be high when above 80 ek Prevu Figure 86 Over temperature detection 112 The analog signal started at 830mV 33 and reached 1 33V 83 C The temperature conversion function was using a moving average of the last 1 28s which explains the detection lag The averaging was lowered to 640ms after this experiment 5 1 4 3 VB Voltage Range Test code Test code VB if err v vb V NORMAL ELED Write 0 else if err v vb V LOW togg eled 1 ELED Write togg eled else ELED Write 1 V LOW is 15V and V HIGH is 28V The power supply voltage was manually adjusted starting with a voltage in range but close to the lower limit dropping below V LOW then going above V HIGH ELED will be low when the voltage is between the 2 limits alternating between digital values of 0 and 1 below V LOW and will be high when above V HIGH 113 ek Prevu Figure 87 VB Voltage in Range detection code 5 1 4 4 Disconnected Battery While using a fixed voltage threshold to detect an out of range VB works this technique cannot be used to detect a disconnected battery The battery voltage will change over time and it is extremely important to detect the disconnection while the VB voltage is as high as possible to maximize the time available to place the circuit in a safe mode VB is sampled every 10ms and a moving average of the last 1024 samples is calculated
78. are soldered clean the flux with alcohol I use 91 and a toothbrush 194 Step 4 Link the PowerPole connectors together according to the order shown on the picture below Twist the cable assemblies Step 5 using a phase change thermal transfer pad made by Laird TPCM 585 Digikey 926 1155 ND It comes in sheets of 9x9 in I laser cut 16 pads per sheet Epilog settings 90 speed 80 power 2500Hz 195 Remove the plastic protection stick the thermal pad to the PCB and screw it to the aluminum plate Make sure that the two FFC programming ports are in the unlocked position first 196 Next step Preparing the FlexSEA Execute 0 1 board Software Preparing the FlexSEA Execute 0 1 board Software 03 17 2015 Previous step Preparing the FlexSEA Execute 0 1 board Hardware List of parts 1x FlexSEA Execute 0 1 with connectors 1x MiniProg3 1x Prog Adapt configured for the MiniProg3 Prog Adapt 0 1 for PSoC PSoC Creator and 2x code projects Estimated time 0h20 Step 1 Connect a power cable between Execute and a lab power supply It is recommended to start with 0V and a low current limit then slowly increase the voltage while making sure that the current stays low the first time that you power a new board When you reach 7V 4 LEDs should turn on You can use any voltage from 15 to 24V 197 Step 2 Open PSoC Creator 3 1 File gt Open gt Project Workspace gt navigate to Code
79. at exc print Unhandled exception in main loop e time sleep 1 print Iterations 2f i print Elapsed Time 2f time time t0 stdin _handle write quit n Save data ddl writeOut BBB x Encoder 10176 Current 102 IMU Gyro x 233 IMU Gyro y 155 IMU Gyro z 590 Strain 18457 Angle 144 Figure 76 Streaming Data in Python 4 5 Future Work As mentioned earlier the FlexSEA software is a work in progress it will never be completed Each new wearable robot design will have its own challenges and requirements Users will add new Special Commands new signal processing algorithms etc The next paragraphs describe 3 ideas that could improve the system independent of the use case 102 Network Bootloader The three boards are programmed with different development environments and tools Changing software from the Common Code folder communication stack requires that all the boards be reprogrammed to support the new commands As more and more degrees of freedom are added this task becomes time consuming network bootloader would allow the user to reprogram all the boards in one simple operation Graphical User Interface GUI The Stream and Log tools allow data visualization and collection but they are limited to raw text Adding a GUI that can plot variables over time would be useful for debugging Being able to send FlexSEA commands with a few mouse clicks could also simp
80. ation interface specification used for short distance communication TX short version of transmission 138 10 2 Execute Schematic RS485 BIOM FLEXSEA EXECUTE 0 1 Clutch SchDoc LUTCH POW Strain BIOM FLEXSEA EXECUTE 0 1 Strain Gauge SchDoc SDA LSCL L Gum LJ SD Protection BIOM FLEXSEA EXECUTE 0 1 Protection SchDoc PSoC5 FLEXSEA EXECUTE 0 1 PSoCS SchDoc MI M2 M M M DE LEE T k Top Safety CoP BIOM FLEXSEA EXECUTE 0 1 Safety CoP SchDoc 1 i L Power BIOM FLEXSEA EXECUTE 0 1 Power SchDoc l UI IMU BIOM FLEXSEA EXECUTE 0 1 UI IMU SchDoc al pul U il SCL SDA RS 85 BIOM FLEXSEA EXECUTE 0 1 RS 485 SchDoc RS485 AI l RS485 BI E RS485 A2 Ee RS485 B2 Sz RS485 1 S s RS485 B3 wi F C a F asi Title FlexSEA Execute 0 1 Biomechatronics Size Letter Number Revision MIT Media Lab E14 274 75 Amherst Street mit Cambridge MA 02139 media USA lab Date 2015 03 05 Time 12 28 57 Sheet of File BIOM FLEXSEA EXECUTE 0 1 SchDoc FERE 3 139 100nF 100nF CYSCSS88AXI LPO96 z Z z Z 5V 5V 5V 5V C
81. ation of a brand new Rev BBB Part 1 JFDuval 03 19 2015 echo FlexSEA Type new password use flexsea by default passwd echo FlexSEA Updating the time servers ntpdate u ntp ubuntu com pool ntp org echo FlexSEA Installing the Adafruit Python libs apt get install python pip python setuptools python smbus Pip install Adafruit_BBIO echo FlexSEA 1 Paste this line capemgr enable partno BB SPIO0 01 no quotation marks 2 Ctrl x Yes Enter cd mnt mkdir boot nano uEnv txt echo FlexSEA When you are ready reboot the BBB command reboot End of script 1 config bbb 2 Configuration of a brand new Rev Part 2 JFDuval 03 19 2015 echo FlexSEA Configuring the SPI driver pins dtc O o BB SPIO 01 00A0 dtbo b 0 BB SPIO 01 00A0 dts cp BB SPIO 01 00A0 dtbo lib firmware 200 echo BB SPI0 01 gt sys devices bone capemgr slots home debian Desktop of script 2 flexsea bbb init echo BB SPI0 01 gt sys devices bone capemgr slots home debian Desktop echo FlexSEA is ready to be used Prog Adapt 0 1 for FlexSEA Execute 03 17 2015 We use a MiniProg3 to program and debug the PSoC It comes with a 10 pins connector that is out of proportion with the size of the PCBs I design A small PCB called Prod Adapt 0 1 is used to convert the 10 pin connector to a small 0 5mm flat flexible cable
82. att Battery status and values power_out Power Outputs clutch Clutch adv_ana_config Advanced Analog Periph Configuration analog Analog Inputs digital Digital 1 05 digital config Digital Os Configuration 78 exp_periph_config Expansion Periph Configuration ctrl_mode Control Mode ctil i g Current I Controller Gains ctrl p g Position P Controller Gains ctrl z g Impedance Z Controller Gains ctrl o Open O Loop Controller PWM ctrl i Current I Controller ctrl p Position P Controller shorted leads Shorted Leads spcl Special Command 1 spc2 Special Command 2 The command codes are 7 bits long left justified The LSB of the command byte is 1 for Read commands and 0 for Write commands All the commands that are to be transmitted have the function prefix tx_cmd_ followed by the category communication control data external expansion sensors system or user and the command name As an example the prototype for the Clutch command is uint32_t tx_cmd_exp_clutch uint8_t receiver uint8_t cmd_type uint8_t buf uint32_t len uint8_t clutch The first 4 arguments are common for all the TX functions receiver is the Slave name cmd_type can be CMD_READ or CMD_WRITE buf is the byte array that will hold the payload generated by the function and en is the length of buf The last parameter clutch contains the duty cycle of the clutch 0 to 255 0 to 100 To turn the clutch
83. aximum value tested takes only 22 5 of the time available It is expected that in future experiments this data rate can easily be quadrupled 122 A second design evaluation criteria linked to the communication between FlexSEA Plan and FlexSEA Execute was to support two Execute boards 1kHz sampling and 20 bytes per FlexSEA Execute test setup was made with 1 FlexSEA Plan 1 FlexSEA Manage and 2 FlexSEA Execute RS 485 bus FlexSEA Manage was auto sampling its two slave every millisecond exchanging 96 bytes per board 48 bytes transmitted 48 bytes received for a total of 768kbits s A special command that included the payload from both FlexSEA Execute boards was used to read write from FlexSEA Plan to FlexSEA Manage That way a single command had to be sent every millisecond even though two circuits were controlled The command used had 48 bytes and was full duplex for a data rate of 768kbits s 5 3 3 Communication Manage amp Execute Criteria Both RS 485 serial interfaces should have a minimum bitrate of 2MBits s The baud rate calculation is details in Section 3 1 4 RS 485 A value of 2Mbits s is expected On FlexSEA Plan the tx_cmd_ctrl_special_1 command was used FlexSEA Execute replies to FlexSEA Manage with a fixed length of 36 bytes An MDO3024 oscilloscope was used to probe the receive line of FlexSEA Manage s RS 485 transceiver reading the values sent by Execute when it replies Figure 97 a
84. cMaster 6659T48 PowerPole housings and crimps Estimated time 1h00 1h15 if Step 0 is required Step 0 If you are using the first batch of PCBs the pull ups I selected for the on board I2C bus are too resistive for speeds above 100kHz we are using 400kHz R45 and R46 are currently 4 7k and they should be 1 8k You can de solder the 4 7k and solder 1 8k resistors recommended or add a 3k resistor in parallel to the 4 7k one Failure to change these resistors will lead to inconsistent behavior as the code will sometimes hang in the I2C routines 192 Step 1 Cut 3 pieces of wire 4 long one piece per color Cut 2 pieces of wire 3 long black and red Remove 3mm of insulation from one end and 5mm from the other end Step 2 Crimp the terminals to the 5 wires on the end with 5mm of exposed copper Make sure to crimp on the sleeve and not just on the copper Insert the crimped wires in their housings 193 Step 3 Solder the wires to the PCB VB Red GND Black A White B Black C Red There is copper planes on all 6 layers a regular 60 80W soldering iron will have a hard time melting solder Use a high power soldering iron such as a Weller WD 1 M 160W or pre heat the PCB with a hot air gun careful you can easily de solder components with that On the picture below you can see the solder joints on the white and black wires The red solder joint was cut close to the PCB with cutters When all 5 wires
85. cmd acq mode write arg fcp_list 16 stream arg 0 fcp_list 17 104 arg 0 fcp_list 18 shuobot arg 0 fcp_list 19 set_z_gains arg 3 fcp_list 20 11 arg 6 Sending 48 bytes 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 9 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 8 00 00 00 00 00 00 00 00 00 00 root beaglebone home debian Desktop Please note that the list of commands is currently being updated to both clarify what they do and expand the available functions 210
86. ctronics but it is a critical component that can in the worst case situation invalidate a revolutionary artificial limb concept This thesis is not about the design of a novel wearable robotic device that contains an embedded system it s purely about the design of the embedded system itself The objective of the thesis is to advance an accessible and capable embedded system architecture that is useable across all wearable robotic research initiatives eliminating the need to design a new embedded system for each and every research project Ironically enough once more the goalis to redesign the wheel but hopefully for the last time Through a careful analysis of wearable robotic requirements across sensor actuator and computational modalities will demonstrate in this thesis that an embedded system design can be achieved that is scalable across a plethora of wearable robotic research programs and therefore will be used henceforth for more than one year in one project There are two main ways of designing electronic architectures for active wearable robotics 1 microcontroller based and 2 embedded computer based Figure 1 shows typical microcontroller based architecture with a single 80MHz processor 1 Figure 2 shows an architecture based on an embedded computer a Raspberry Pi running at 800MHz 2 13 Commercial products are mostly microcontroller based while research prototypes tend to favor systems with embedded computers
87. cture Figure 3 presents the simplest full stack all three FlexSEA boards design typical of what can be used for a one degree of freedom DOF research project such as a powered knee 20 Remote Computer Figure 3 FlexSEA System Architecture 1 DOF While developing and testing a new system it is expected to have most of the algorithms running on the embedded computer FlexSEA Plan FlexSEA Manage is mostly used as a bridge translator between different communication busses but it can also be used to add extra sensors to the system FlexSEA Execute is in charge of all the motor control algorithms As the software behavior stabilizes the high level control algorithms can be re written in C if they were not already in C and ported on FlexSEA Manage and or FlexSEA Execute Over time the role of the embedded computer will be less and less important On a commercial or pre commercial application it could be completely removed from the system Remote Computer Figure 4 FlexSEA System Architecture 1 axis 2 DOF 21 2 5 System wide technical decisions The main goal of that thesis is to provide researchers at the completion of this project with a set of electronics boards that can be used to quickly prototype new prostheses and exoskeleton ideas The broad range of applications user s technical abilities from neuroscientists to mechanical engineers and the diversity of actuators and sensors used in Biomechatronics make
88. cute zoom on the 1st 122 Figure 97 RS 485 Data 48 Dyt S uuu 124 Figure 98 RS 485 Data ZOOMING on 1 bit a 124 Figure 99 Data logging with the Log application 127 Figure 100 CSEA Knee with FlexSEA n n NR CE UR ec 128 Figure 101 Student wearing an early prototype of the dual autonomous exoskeleton 129 12 1 Introduction Reinventing the wheel is an idiom often associated with engineering and design While innovators use the expression to describe a ground breaking solution or design it mostly has a negative connotation Engineers will be told not to reinvent the wheel when they are struggling with details or technicalities rather than focusing on the big picture the problem worth solving But what if that metaphorical wheel was indeed broken Looking back at previous work in the field of exoskeletons and powered prostheses can be depressing for an embedded system designer The wheel in the form of the embedded electronics is redesigned year after year project after project with no clear progression and many system redesigns The big picture problem is to give mobility to people that lost it to augment able bodied people not to design ele
89. d communication interfaces By closing the critical control loops on FlexSEA Execute we offload the communication interfaces The FlexSEA Manage board is also used as a bridge communicating with FlexSEA Plan via a high speed interface and communicating with other boards peripherals via a variety of other communication protocols Can only support brushed motors The Execute board is designed for brushless motors it can inherently support brushed motors Can only support one motor FlexSEA has been designed with scalability in mind With its two serial interfaces FlexSEA Manage can support two FlexSEA Execute without any bandwidth restrictions More than one FlexSEA Execute can be on each bus the total bandwidth being divided between the boards Commercial motor driver has to be tricked into running a special control loop no built in functionality The user has full control over the hardware and the software of the motor driver Any type of controller can be programmed in C and can run at high speed on the Execute board The Expansion connector supports a wide variety of external sensors they can all be used in control loops Power consumption The power consumption of the embedded system can be high when an embedded computer is used Better energy efficiency can be obtained by using a simpler computer HD video peripherals audio amplifiers and wired Ethernet connections are not 25 required in wearable robotics app
90. d principles The perfect architecture should e Combine the power of efficient low level code and the flexibility of high level languages e Allow for quick prototyping of new prostheses and exoskeletons both on the hardware and the software side e Allow quick modifications and additions of sensors and actuators Bescalable Prevent errors on the high level code to cause safety issues e Beuseable both on research prototypes and on early production units Minimize and simplify wiring e Have built in safety features 2 3 Subsystems These specifications can be obtained by using one or many microcontrollers and an embedded computer in the same system with a clear boundary between their tasks and functions The embedded computer is used only for one task high level controls such as finite state machines or continuous control laws One powerful microcontroller per axis is used to interface with all of the sensors and simple output devices A separate printed circuit board assembly PCBA interfaces with the electronics required for motion control Following a business organization naming strategy the three FlexSEA boards are named Plan Manage and Execute 19 2 3 1 FlexSEA Plan FlexSEA Plan is an embedded computer used for high level computing It boasts a powerful processor and can run an operating system such as Linux Developing code on this platform is similar to the regular i e non embedded software development pr
91. d time required to complete part 2 3 If you were able to successfully read the state of the Manage pushbutton from Linux please proceed to Part 3 Otherwise please stop the experiment Part 3 Adding FlexSEA Execute to the system Yes No Were you able to connect Manage and Execute together you stream the Execute sensor values Linux 4 Were you able to connect the output device to Execute ES control the output device from Linux 165 166 10 5 User Manual An offline HTML website was created for the User Study It guides the user through the installation of the development tools the configuration of the system and through simple tasks reading sensors controlling outputs copy of the documentation pages is included in the following pages of this thesis It is recommended to obtain the website from the archive and to use this documentation in a browser to benefit from all the links FlexSEA Documentation 03 19 2015 Table of Contents25 General e FlexSEA How to use e Introduction to FlexSEA e FlexSEA Virtual Machine e What s in the box e Update your SVN Hardware amp connections e FlexSEA Execute 0 1 Hardware overview Prog Adapt 0 1 for FlexSEA Execute e Prog Adapt 0 1 for FlexSEA Manage 0 1 e Plan Manage Cable e Connect Manage to Plan e Connect Execute to Manage Preparing the FlexSEA Execute 0 1 board Hardware Software amp programm
92. e elf Use that command openocd s Desktop FlexSEA embedded arm openocd bin share openocd scripts f interface stlink v2 cfg f target stm32f4x_stlink cfg c init c reset halt c sleep 100 c wait_halt 2 c flash write_image erase manage elf c sleep 100 c verify image manage elf c sleep 100 c reset run c shutdown e ARM GCC compiler Note this isn t the same as for Manage we now using the Embedded Linux version of GCC Get and install with sudo apt get install gcc arm linux gnueabi The executables in usr bin You can test your installation by typing arm linux gnueabi gcc v in a terminal You should see a large block of text followed by a statement similar to gcc version 4 7 3 Ubuntu Linaro 4 7 3 12ubuntu1 e Plan project under Eclipse Launch Eclipse then File gt Import gt General gt Existing Projects into Workspace gt browse to your directory Code flexsea_1_0 plan You will see the project in the Project Explorer You can compile the project by clicking on the Hammer icon Please note that 3 options are available Debug use this for debugging on your host computer This uses a native compiler not a croiss compiler You can test your work by opening a terminal navigating to the Debuf directory cd Desktop FlexSEA biomech ee svn Code flexsea_1_0 plan Debug and launching Plan with plan default info You will see the list of supported Fl
93. ead of 100 ohm This is reflected in the Future Work section Ahigher degree of protection would be gained from using a higher value resistor The main trade off of designing a system that can be used for any situation is that one cannot optimize every single detail Using a value such as 1k or 10k for un buffered analog inputs would introduce too much noise in the ADC conversion 3 1 9 Userinterface A RGB LED is used to display the state of the code normal communication loss warning error A flashing green LED is used as a heartbeat signal when the code is running properly it flashes 13 http www ti com lit ds symlink tpd4e004 pdf 53 5V E R17 3k 9 Nn X R20 D17 1 3k wY LNJ347W83RA GND Figure 35 RGB LED and Green heartbeat LED The white balance of the RGB LED is poor due to a bad assumption constant current across colors does not lead to white light when R G amp B are turned fully ON The Future Work section specifies different resistor values A USB port is present on board for debugging Users can use it to send FlexSEA commands to Execute without the need of Manage and or Plan D6 TPD2EUSB30DRTR Figure 36 USB ESD protection Figure 37 USB protection routing 54 3 1 10 Power Supplies 4 different voltages are required on Execute Table 5 specifies the naming convention and the voltage ranges Tod Figure
94. ecided not to design a custom embedded computer but to rather use a standard communication interface SPI that would allow the user to select any product on the market Processing power can easily be added to the FlexSEA system as new embedded computers become available 22 2 5 2 Communication hardware FlexSEA Plan and FlexSEA Manage have to exchange information While embedded computers offer a lot of processing power communication isn t always optimal On one hand some of them have simple interfaces such as serial UART and 12 that could be used to directly interface with sensors and microcontrollers but the data rates are limited At the other extreme the Ethernet port can be used but it requires substantial hardware and software overhead on the FlexSEA Manage board SPI offers a communication compromise with typical data rates above 20 Mbits s more than enough for our application Due to data rate dropping quickly with distance FlexSEA Manage has to be physically close to Plan For the interface between FlexSEA Manage and FlexSEA Execute s the common choices in robotics CAN 12 and EtherCAT While CAN is cheap robust and safe its 1Mbps bandwidth is an important bottleneck for application with multiple motor drivers EtherCAT offers 100Mbps but that speed comes with a price the bus requires a Master When this project was started no embedded computer was certified as an EtherCAT master thus requiring the presence of
95. ed It allows functions to be called at either 10kHz 1kHz or 250Hz with deterministic timings and constant offsets The t1_new_value t1_time_share variables are controlled by 100 5 timer interrupt if tl new value 1 If the time share slot changed we run the timing FSM Refer to timing xlsx for more details tl new value updates at 10kHz each slot at 1kHz tl new value 0 Timing FSM switch tl time share Case 0 I2C case 0 i2c time 9 i2c time share 4 ifdef USE I2C INT Subdivided in 4 slots switch i2c time share Case 0 0 Accelerometer case 0 ifdef USE IMU get_accel xyz imu last request IMU RQ ACC zal ee 84 endif US break Case 0 1 Gyroscope case 1 ifdef USE IMU get_gyro xyz imu last request IMU fendif US break Case 0 2 Safety Cop case 2 IMU RQ GYRO IMU safety cop get status break Case 0 3 Free case 3 can be the I2C RGB LED break default break endif USE I2C INT break Case 1 case 1 break Case 2 case 2 break Case 3 Strain Gauge DelSig ADC SAR ADC case 3 Start a new conversion ADC DelSig 1 StartConvert Filter the previous results strain filter dma break 85 At the end of this function not shown in the code sample is a section reserved for code that needs to be
96. ed in the interest of full disclosure An updated list of criteria is available in Section 7 2 e Users read sensors and control actuators C and in Python e The system can be used without the Plan board by executing code on Manage e Anew user can unbox a FlexSEA kit and o control a motor from Linux in less than one working day 8h o read a sensor from Linux in less than one working day 8h e The Execute board can run an impedance loop at more than 1kHz without being connected to any other board e The Plan board can communicate with an Execute board at a minimum of 2MBits s through a Manage board e The Manage board can connect to a minimum of two Execute boards with a data rate of at least 2MBits s per board e The Execute board will default to a shorted leads protection in a hazardous situation tested by disconnecting the main battery 7 2 Evaluation Criteria The criteria presented in Section 7 1 have been sub divided to ease the evaluation process Whenever possible quantifiable objectives have been set Section 7 3 summarizes the results in one table 1 Users can read sensors and control actuators in Linux Software will be provided to a Display live sensor values on a terminal computer screen Section 4 4 1 130 b Record sensor values in a human readable text files A minimum of 8 bytes of data can be logged at least every 10ms 100Hz 6 4kbits s Section 5 3 4 c Demonstrate a high level controlle
97. en to maximize the performance of the system While the table above mentions 67MHz the device used in this project CY8C5888AXI LP096 is 80MHz 100DMIPS The hybrid hardware software implementation will be described in the Software section of this document 3 1 2 PSoC 4 Safety Co Processor FlexSEA being a development platform it is expected that users will reprogram the FlexSEA Execute board to add new commands or control strategies Timings are critical in embedded programming especially in systems without an operating system such as ours Adding a long routine in an interrupt using complex floating point math or poorly managing communication with peripherals can disrupt the code execution significant delays can be added control loops can be rendered unstable Running the debugger or reprogramming the microcontroller while the BLDC motor is turning can also have dangerous consequences To add one layer of safety we use a second microcontroller the Safety Coprocessor Safety CoP A small PSoC 4 device was selected because of the convenience of its programmable logic and the availability of the development tools same as for the PSoC 5 32 3x Current 3x Phase voltage Temperature SL_GATE VG Measure RGB LED VB Measure Figure 9 FlexSEA Execute hardware safety features diagram The two PSoC are linked via an 2 bus same bus that is used for the IMU and the digital potentiometers and via a Watchdog Clock
98. ent design Upon close inspection of the layout a comment was added to the list of future modifications the drain should be attached to a bigger copper area Another option is to replace the FDN5618 by a SI2319CDS 77 MOSFET same package 10 cents more 3 2 4 IMU Please refer to Section 3 2 4 IMU in FlexSEA Execute hardware The two designs use the same IMU 3 2 5 FLASH The Manage board has an onboard FLASH memory for data logging during experiments It can be used for systems that do not include a Plan board C13 100nF GND 25 128 GND GND Figure 58 FLASH Memory 71 Table 8 Bits of storage needed per second of data logging Data bytes Frequency Hz 2 4 8 16 32 1 16 32 64 128 256 10 160 320 640 1 28k 2 56k 100 1 6k 3 2k 6 4k 12 8k 25 6k 1000 16k 32k 64k 128k 256k Typical science experiments are limited to 30 minutes 1800s and logging rates from 100Hz 11 to 200Hz 1 are sufficient Saving 16 bytes at 100Hz requires 23Mbits No memories of less than 32Mbits were considered The main part selection criteria were 1 5 interface 2 small size and 3 common industry standard package The M25P128 has 128Mbits of storage and is convenient 8 VDPFN package Table 9 Minutes of data logging in a 128Mbits FLASH memory Data bytes Frequency Hz 2 4 8 16 32 100 1333 667 333 167 83 1000 133 67 33 17 8 The trace
99. eripherals Analog inputs Up to 8 12 bit SAR 8 20 bits Sigma Delta Serial PC SPI UART Other 1 optical encoder 1 1 Hall effect encoder 3 pins X mm 49 Dimensions mm 49 Z mm From 12 to 15mm depending on capacitors Layers 6 Copper 102 technology 5 Assembly 5 5 mils trace space 8 20 mils blind vias Double sided Other 6 axis IMU RGB LED 3 1 1 PSoC 5 LP Microcontroller 3 1 1 1 Microcontroller selection Since the invention of the microcontroller in the seventies hundreds of companies are producing and selling microcontrollers Most manufacturers have broad portfolios of parts some of them offering hundreds of part numbers per family of controllers Motor control applications are an important market for microcontrollers Many manufacturers sell devices optimized for this application The dsPIC series of Digital Signal Controllers by Microchip is a popular choice for low volume products and hobby designs They have dsPICs spanning from small device that can control a 29 single motor to large chips able to drive two motors Having designed multiple dsPIC based BLDC drivers for various companies before joining MIT decided to stay away from Microchip products First wanted to generate new and avoid possible conflicts Second wanted to explore outside of my area of expertise The main problem was facing with dsPIC based designs is t
100. evel software C Python Java Matlab not processor efficient e Higher power less energy efficient e Relies on commercial parts no control over the production and life cycle e Harder to modify 14 e Integration issues between different subsystems Suboptimal wiring The two approaches have been used in a multitude of published wearable robotic systems with various degrees of success A few examples are described here 1 2 13 17 Since the embedded system aspect of a design is considered a means to an end documentation is considered unimportant and is usually scarce Following the evolution of a wearable robotic design one will read sentences such as Developed a new embedded electronic system without a clear justification as to why the previous design had to be abandoned rather than improved In all of the designs made in the MIT Biomechatronics Group over the last 11 years only one project AAKP Agonist Antagonist Active Knee Prosthesis 18 used two actuators in one joint Due to issues with the control electronics of previous prototypes brushed DC motors lieu of brushless DC motors were used thus impacting the efficiency and mass of the prosthesis When experiments were conducted with trans femoral amputees wearing an active ankle foot and an active knee the two joints were controlled independently without an overarching high level controller Consequently the lack of availability of
101. exSEA commands Release Single one task per program call Convenient for sending commands on the terminal as it will give you feedback Release Multiple multiple tasks per program call Use this to interface with Python or other languages as it s much faster than spawning a new instance of the program everytime you want to send a command to a board Plan Manage Cable 03 17 2015 We need a cable to link a Plan board BBB to a Manage board The BBB is powering the Manage board For the BBB I m using a 2x23 male header For space sensitive applications wires could be soldered under the PCB rather than adding this extra connector Pin assignment 189 MISO BBB SPIO DI SPIO SCLK BBB UITX BBB UIRX On the Manage board we use J3 5VP is used to power the Manage board VP Voltage Plan is used to level shift the SPI signals It needs to be at the same voltage as the SPI signals coming out of the Plan board 3 3V in that case The Reset signal is not currently used but in the future it will allow the Plan to reset the Manage Plan BIOM FLEXSEA ON tn 5V Red VP Orange GND Black SCK Green NSS Yellow MOSI Orange MISO Blue 190 191 Preparing the FlexSEA Execute 0 1 board Hardware 03 17 2015 List of parts 1x FlexSEA Execute 0 1 assembled PCB 1x aluminum mounting plate 1x thermal pad 1 5x M2x4 screws AWG16 wire in red black and white M
102. executed every 100 5 It is called after one of the time slots 4 2 2 BLDC Commutation A four quadrant PWM commutation table is required to support bidirectional motor control with regenerative currents Figure 66 is part of So Which PWM Technique is Best by Texas Instrument Figure 66 Unipolar 4 Quadrant PWMs Texas Instruments Table 12 was created from Figure 66 A and B are the intermediary signals at the output of the AND gates The red text indicate a problem this table sets steady state high values on the high side MOSFETs The gate drivers used on FlexSEA Execute can t support this The two NOT gates were moved from the high side to the low side to fix this problem as presented in Table 13 A test was made to confirm that the half bridges are using complementary switching and that they are never ON at the same time shoot through 23 http e2e ti com blogs b motordrivecontrol archive 2012 03 29 so which pwm technique is best part 3 86 Table 12 Original 4Q Table Table 13 Modified 4Q Table em o o a i sem 0_ _1_ Q1 2 Comp Lene ow cw Q1 2 Shoot Qi 2Comp TRUE TRUE TRUE Q3 4 Comp Q1 2 Shoot FALSE FALSE FALSE Q3 4 Shoot Q3 AComp TRUE TRUE TRUE 93 4 FALSE FALSE FALSE This table has to be expanded for three phase brushless motors The order of the phases is determined by the Hall Effect sensors present in most research grade brushless motors such as the
103. extremities 19 This thesis presents the design of a modular embedded system optimized for wearable robotic applications A flexible architecture allows FlexSEA to be used in a wide variety of projects with or without an embedded computer All the safety features of commercial devices are included onboard as well as all the typical sensors and output device interfaces required for wearable robotic applications The highly integrated circuit board designs presented in the thesis minimize the weight of the embedded system require a minimal amount of wired connections and are proven to be easy to use by students The design was evaluated by a user test and by multiple quantifiable metrics related to the electrical performance of the different circuit board and of the system as a whole 17 2 System Design 2 1 Combining architectures The main trade off between microcontroller and embedded computer based systems is ease of development versus optimal design A company designing a new product will likely opt for the microcontroller based system to allow a tight integration with the mechanical and industrial design of the device while keeping unit cost at a minimum A research lab will likely opt for the embedded computer system to allow students and researchers without advanced electrical engineering skills to develop and test new control schemes and wearable robot concepts 11 One important limitation of both systems is the presence of a s
104. f Figures Figure 1 Microcontroller based architecture example 1 14 Figure 2 Embedded computer based architecture example 2 14 Figure 3 FlexSEA System Architecture 1 DOF 21 Figure 4 FlexSEA System Architecture 1 axis 2 DOF 21 Figure 5 FlexSEA Execute 0 1 Hardware 27 Figure 6 FlexSEA Execute System Diagram 28 Figure 7 PSoC 5 ad excellent visualization 31 Figure 8 PSoC Families re n eR ee De b eri S 31 Figure 9 FlexSEA Execute hardware safety features diagram 33 Figure 10 PWM signals passing through the Safety CoP 34 Figure 11 BEDC schemati topi eveluu r uu un l a SU emen 34 Figure 12 BLDC sensors phase voltage amp temperature 35 Figure 13 VB Decoupling capacitors
105. flexsea_1_0 execute cop execute cop cydsn and select the cywrk file Build execute cop and make sure that there is no error message Connect the FFC to the Execute board using the right FFC connector as seen from above The FFC conductors need to face the PCB seen from above they ll be visible Click Program You ll get a log similar to this Programming started for device PSoC 4200 424510 483 Device ID Check Erasing Programming of Flash Starting Protecting Verify Checksum Device PSoC 4200 CY8C4245LQ 483 was successfully programmed at 03 17 2015 14 54 08 The Red LED right next to the PSoC 4 should flash aggressively because the PSoC 5 isn t programmed Step 3 Programming FlexSEA Execute 0 1 Preparing the Plan board BeagleBone Black 03 19 2015 198 This page explains how to configure a brand new Rev C BeagleBone Black for FlexSEA I m using the Element 14 BeagleBone Black Rev C 4GB Pre installed Debian Element 14 Version from Adafruit http www adafruit com products 1996 Scripts are provided to simplify the user s life Estimated time 0h30 Step by step instructions 1 Connecting to the BBB and transfering files 1 Connectthe USB Mini B cable between your host computer and the BBB Connect an Ethernet cable to the BBB to give it internet access 2 If you are using a VM make sure that the BBB is listed as a connected Removable Device After a few seconds you
106. h FlexSEA Outputs e C RGB LED e Clutch e Maxon 30 Brushless DC Motor 128 The FlexSEA Plan board runs a Python state machine that interfaces with the FlexSEA C software The impedance loop is closed on FlexSEA Execute at 1kHz The Python algorithms are simple enough that they could run on the FlexSEA Manage board a convenient feature for a future version of this project 6 2 Autonomous Exoskeleton A 2 DOF system such as the one presented in Figure 4 was used for a dual leg autonomous exoskeleton developed at the MIT Media Lab Biomechatronics Group an extension of the work presented in 19 Inputs e Incremental encoder e Hall effect e Analog angle sensor potentiometer e Strain gauge based torque sensor e Motor current sensing Output e Maxon EC 30 Brushless DC Motor The embedded computer is used for the high level controller and for datalogging The control code does not require the processing power of this embedded computer as soon as the Figure 101 Student wearing an early prototype of the dual autonomous exoskeleton algorithms stable they should be programmed on the Execute board This will simplify the wiring and reduce the system complexity 129 7 Evaluation and Results 7 1 Evaluation Criteria legacy In November 2014 the following list of design criteria was proposed and accepted Most elements lack details and are as stated hard to evaluate This list is includ
107. he limited analog integration Adding hardware safety features such as current control and protection requires many external ICs and large surface area or inefficient software Power consumption is also an issue as the dsPICs are power hungry controllers 1 9mA DMIPS vs 228uA DMIPS for PSoC 5 and 414 for STM32F4 TI DSPs are commonly used for advanced motion controllers one example being the DLR Joint 14 The lack of either an open source or a free closed source development environment prevented me from prototyping with their devices STMicroelectronics is aggressively marketing some of its STM32 ARM based MCU for motor control applications Looking at their datasheet they use the same design blocks as the whole industry therefore no real technical gain could be had FPGA CPLD can offer high performance but at the cost of complexity 13 power and minimal analog integration One family of mixed signal microcontrollers the Cypress programmable system on chips PSoC offers a hybrid solution between an FPAA a microcontroller and FPGA CPLD 30 3 1 1 2 Programmable System on Chip PSoC 8 bit M8C core 8 bit 8051 core single cycle 32 bit ARM Cortex M0 32 bit ARM Cortex M3 up to 24 MHz 4 MIPS up to 67 MHz 33 MIPS up to 48 MHz MIPS up to 67 MHz 84 MIPS Flash 4 KB to 32 KB Flash 8 KB to 64 KB Flash 16 KB to 32 KB Flash 32 KB to 256 KB SRAM 256 bytes to 2 KB SRAM 3 KB to 8 KB SRAM 2 KB to 4 KB SRAM 8 KB
108. hling M E Abdallah N A Radford L B Bridgwater A M Sanders R S Askew D M Linn J D Yamokoski F A Permenter B K Hargrave R Platt R T Savely and R O Ambrose Robonaut 2 The First Humanoid Robot in Space 2011 IEEE International Conference on Robotics and Automation May 9 13 2011 L B Bridgwater C A Ihrke M A Diftler M E Abdallah N A Radford J M Rogers S Yayathi R s Askew D M Linn The Robonant 2 Hand Designed To Do Work With Tools 2012 IEEE International Conference on Robotics and Automation May 14 18 2012 S K Au H Herr J Weber E C Martinez Villalpando Powered Ankle Foot Prosthesis for the Improvement of Amputee Ambulation Proceedings of the 29th Annual International Conference of the IEEE EMBS August 23 26 2007 E C Martinez Villalpando J Weber G Elliott and H M Herr Design of an agonist antagonist active knee prosthesis Proceedings of IEEE BlORobotics Conference Scottsdale AZ 2008 Mooney et al Autonomous exoskeleton reduces metabolic cost of human walking Journal of NeuroEngineering and Rehabilitation 2014 11 151 136 10 Annexes 10 1 Glossary ADC Analog to digital converter ARM microcontroller core and instruction set developed by ARM Holdings and licensed to microcontroller companies BLDC Brushless DC Motor ASIC Application Specific Integrated Circuit BJT bipolar junction transistor COTS Commercial off the shelf used t
109. icient way to do so The Special Commands are designed with efficiency in mind Every project should define one or more Special Command that supports only the required fields Decoding a Special Command is faster than decoding multiple commands sent back to back because only one parser call has to be used 4 2 FlexSEA Execute FlexSEA Execute uses a PSoC system on chip controller as its main computing unit refer to section 3 1 1 for more details The PSoC was chosen because its analog and digital programmable blocks can be used to offload the main CPU from time consuming tasks and to 82 minimize the number of external circuits required Figure 28 is a good example of analog programming 4 2 1 Organization and timings Timings are critical on the Execute board Control loops have to be called at fixed intervals to guarantee stability and some data conversion have timings dependant on other software functions One example is the Delta Sigma ADC used for the Strain Gauge Amplifier its conversion needs to be done when the C bus is in idle otherwise the digital potentiometer are coupling noise in the circuit With the compiler optimizations turned off and the Global Interrupt disabled test code was executed and an oscilloscope was used to measure the time it takes to call and execute some key functions 314 column uses a safety factor of 1 75 to take interrupts into account Table 11 Function timing benchmark
110. ime 12 28 58 Sheet MIT Media Lab E14 274 75 Amherst Street mit Cambridge MA 02139 l media of USA lab File BIOM FLEXSEA EXECUTE 0 1 Power SchDoc 3 4 146 TG MBR0580 TP cu 5 sGND LM25011Q1 GND GND GND GND GND GND GND 147 Biomechatronics Execute LM25011 10V DC DC Biomechatronics 2 75 Amherst Street Size Letter Number Revision Cambridge MA 02139 Date 2015 03 05 Time 12 28 58 Sheet of USA n File BIOM FLEXSEA EXECUTE 0 1 LM25011 DCDC SchDoc 2 3 4 TG D27 5V 47uF 10uF 562163 GND GND GND GND GND GND 148 Execute TPS62163 5V DC DC MIT Media Lab E14 274 75 Amherst Street Size Letter Number Revision Cambridge MA 02139 Date 2015 03 05 Time 12 28 59 Sheet of USA E33 File BIOM FLEXSEA EXECUTE 0 1 TPS62163 DCDC SchDoc 1 2 3 4 45y 38 7 5k RGA SHDNA PIA ERG VoutA PIB MCP4661T 103 C31 GKp GND DDA TPD4E004DRYR 100nF 100nF m TPD4E004DRYR 149 GND GND GND 45y gt sc gt NA2331 5V
111. in tm tm sec xecl encoder execl current execl imu x execl imu y execl imu z execl strain execl analog 0 Your state machine would be here gt gt gt Delay usleep 10000 Should be much shorter in a real application Close log file fclose logfile printf Logfile is named s n str printf lines i with valid data n lines good printf Log file closed Exiting n n n 4 4 3 Interfacing with higher level languages To interface with languages other than C the Release Multiple compile option should be used In Single a new process is spawned for every FlexSEA command In Multiple the user can keep feeding commands to the process and get data back As an example here is Python code to stream sensor values on a terminal usr bin python This code uses the speciall command to demonstrate writing and reading from an Excecute board from Linux in Python speciall is the special command used by the ShuoBot Exoskeleton It displays a few sensor values on the terminal db db dk import time math random subprocess traceback from subprocess import Popen PIPE 100 import pty import os Based on State Machine vl 8 8 14 J Rouse J F Duval Modified for BBB from original versino on RPi See Rouse et al 2014 IJRR Clutchable series elastic actuator implications for prosthetic knee de
112. in Media Arts and Sciences Thesis supervisor David Perreault Ph D Professor of Electrical Engineering Electrical Engineering and Computer Science EECS Table of Contents PEE 3 X 13 2 System DESIG Mi ic ere iret eie desee u Sha QQ u Rae 18 21 architectures a 18 2 2 5 core ideas and principles inset L u u a ui 19 2 3 S bsystems x aen t teretes 19 22345 FISK SE APU AN cct 20 2 3 2 5 ERE ONERATUS ree ETUR 20 2 3 3 FHeXSEASEXGCULUG boi RE 20 2 4 iSystem ArchiteCture e au S ua 20 2 5 System wide technical decisions 22 2 5 1 FlexSEA Plan Embedded computer eese eene enne enne 22 2 5 2 Communication hardware euet oda od atm cip e 23 2 5 3 Communication soft sse 7 23 2450 aspe end qa 24 2 6 Design solutions short answers
113. ing e Installing the Plan amp Manage Development Environment on your host computer Preparing the Plan board BeagleBone Black e Using a pre configured BeagleBone Black Plan board e Eclipse OpenOCD GDB Debugging for the Manage Board e Compile the Plan project e Connecting to the Plan board BBB 25 Red titles indicate new HTML files 167 Transferring a program to the Plan board BBB Compile the Manage project Program debug Manage Preparing the FlexSEA Execute 0 1 board Software Programming FlexSEA Execute 0 1 Application Read a simple sensor from Linux Pushbutton on Manage Read multiple sensors from Linux Execute Add and control an output device Execute FlexSEA How to use 03 16 2015 First time user introduction and preparation Read Introduction to FlexSEA to get a general idea of the system Get SVN access o Give your Media Lab username to the admin jfduval o Change your password to a random one they are not encrypted o Update your SVN Read What s in the box and make sure that you have everything that you need Get a copy of the FlexSEA Virtual Machine recommended or install all the sources and development tools on your machine Installing the Plan amp Manage Development Environment on your host computer Follow Preparing the Plan board BeagleBone Black to configure a new BBB If your Execute PCB is in a metallic bag without any wires it s not ready to be used Follow these two note
114. ing on the system architecture In the simplest system designs it will act as a communication protocol translator allowing Plan and Execute to communicate When multiple FlexSEA Execute are used it routes packets and can manage communication timings It can be used to add extra sensors and output devices to the system In systems that do not require the computing power of an embedded computer Manage can host the high level state machines Figure 45 presents the hardware diagram of FlexSEA Manage 0 1 In orange are the schematic sheets and in grey are the sub circuits present on certain sheets 61 Expansion Connector 2x G 1 2 G 1 2x 1 lt G lt 10 2x 0 10k V 10kHz LPF Divider Figure 45 Manage 0 1 Hardware Table 6 FlexSEA Manage 0 1 Specifications Electrical Supply voltage V 5V in from Plan or USB on board 3V3 regulator specifications Current mA 90mA Reference STM32F427ZIT6 Microcontroller Special features CPU RAM IOs Package Software IDE Floating point co processor can be software enabled 180MHz ARM Cortex M4 2MB FLASH USB Eclipse C C GNU Tools for ARM Embedded Processors arm none eabi gcc OpenOCD GDB Serial interfaces Type Bandwidth Type Bandwidth 2x half duplex asynchronous full duplex or synchronous full duplex RS 485 2 10Mbps Full duplex SPI 20 Mbps Onboard USB Full Speed FS High Speed HS Peripherals FLASH memor
115. ing properly Power cycling might be required Read a simple sensor from Linux Pushbutton on Manage 03 19 2015 Program the latest code to Manage Program debug Manage in Release mode The RGB LED will initially be green then after a few seconds steady blue It means that the board isn t receiving commands from Plan LEDO will blink Connect to the Plan board Connecting to the Plan board BBB transfer the latest Plan code Transferring a program to the Plan board BBB Call plan manage 1 stream The RGB LED will turn green and the switch state will be displayed It will turn to 0 if you press on the pushbutton It s tiny use your fingernail 207 ELS um 9 oe 9 Emamma M The code isn t 10096 stable yet If the LED is Blue while Stream is running something is wrong Either reprogram Manage or power cycle it and it should be fine To stop streaming quit the program with Ctrl D For now manage 1 stream is calling one function SWITCH In the future it will display more information Read multiple sensors from Linux Execute 03 19 2015 Program the latest code to Manage Program debug Manage in Release mode The RGB LED will initially be green then after a few seconds steady blue It means that the board isn t receiving commands from Plan LEDO will blink Power Execute and make sure that it s running up
116. ingle computing element excluding the microcontrollers that are present in some sensors and motor drivers to manage all the sensors and actuators Changing a high level gate control algorithm has the potential to introduce bugs in safety critical motor control functions Embedded programmers know how easily one can break poorly written code functionality simply by adding one line at the wrong location breaking the precise flow of the program A public example of a safety critical software bug is the unintended acceleration problem of Toyota cars For sure well written code should prevent safety issues but it s not always what researchers have access to This brings us to a core idea of the flexible and scalable electronics architecture FlexSEA hardware and software encapsulation In object oriented programming encapsulation refers to a language mechanism for restricting access to some of the object s components The programmer determines what needs to be accessible from the outside and what should be kept private It s possible to build an electronic architecture with the same principle used both for hardware and software One example is NASA s Robonaut system Modularity is prevalent throughout the hardware and software along with innovative and layered approaches for sensing and control 15 http www edn com design automotive 4423428 Toyota s killer firmware Bad design and its consequences 18 2 2 FlexSEA core ideas an
117. ircuit boards that simply prototyping These products are now commonly integrated in academic research projects 2 3 9 11 Custom embedded system designs have been published for wireless sensing 5 miniature mobile robots 6 and mechatronics education and teaching 7 8 The common goals are to minimize the number of circuit redesigns and simplify prototyping 5 The price to pay for modularity is often the increase of the number of circuit boards required for an application and the increase of inter board connections Wearable robotics projects have different requirements than most pure robotics and wearable sensing projects Safety and reliability are major issues especially in powered prosthetic devices Simplifying the devices by using a minimal number of circuit boards and by minimizing the number of interconnections helps with safety and reliability The number of degrees of freedom is relatively small compared to humanoid robotics but the instantaneous power requirements are high 2 19 a greater emphasis has to be placed on power electronics than on digital communication between the t http www netmf com gadgeteer http www arduino cc en Main ArduinoShields Shields Capes and Blocks are different name for the same product category stackable expansion boards 16 modules The volume and the weight of the embedded system must be minimized because of their direct impact on the efficiency of devices attached to body
118. it was powered at 24V The programmed resistive load started at 100 0 9 V2 R 51 84W The temperature was constantly monitored and the load was reduced every few minutes when the temperature had stabilized After 5 minutes at 50 the temperature was 35 C The lowest resistance tested at 24V was 2 50 pulses of 9 6A 230W average of 207W After 7 minutes with that load and a total of 15 minutes with varying loads the temperature was stable at 50 6 C The BK 8500 has a power limit of 300W the maximum current at 24V is 12 5A To maximize the amount of heat generated the voltage was lowered to 15V and the load resistance decreased enough to reach the 15A limit of both the power supply and the programmable load After 6 minutes and a total of 25 minutes with varying loads the temperature was stable at 61 7 C and the experiment was stopped This test confirmed that the FlexSEA Execute 0 1 circuit can be used with a minimalist heat sink and no forced airflow for steady loads up to 15A 225W with a safe margin of more than 20 C before the temperature rating of some semiconductors present on the circuit is reached Due to the absence of more powerful test equipment a 20A test was not conducted Modelling the 105 thermal properties of the assembly will be done in the future It is safe to assume that with some precautions the circuit can be used at 20A the first one being the use of a better thermal transfer pad 5 1 2 Strain Gauge
119. ituation such as a Microcontroller doesn t execute code or exhibits significant delays See 5 1 4 1 b Over temperature warning at 75 C error at 80 C See 5 1 4 2 c Battery voltage out of range See 5 1 4 3 131 d Disconnected battery See 5 1 4 4 7 3 Results Table 17 shows a summary of the results associated with the design criteria described in the previous section Table 17 Summary of Results Criteria Metric Goal Measured Status Details 1 Pass a Pass Fail Pass Section 4 4 1 b 100Hz 6 4kbits s 769Hz 98kbits s Exceeded Section 5 3 4 Pass Fail Pass Section 4 4 2 d Pass Fail Pass Section 4 4 2 2 Pass Fail Pass 3 Under 16h 2h35 Exceeded Sections 10 4 and 10 5 4 1kHz 1kHz Pass Section 0 5 Pass a 2Mbits s 2Mbits s 12Mbits s 2Mbits s Exceeded Sections 5 3 1 amp 5 3 2 b 320kbits s 1 3Mbits s Exceeded Section 5 3 2 6 Pass a 2 4 Exceeded b 2Mbits s 2Mbits s Pass Section 5 3 3 7 640kbits s 768kbits s Exceeded 8 Incomplete a Pass Fail Pass See 5 1 4 1 b Pass Fail Pass See 5 1 4 2 Pass Fail Pass See 5 1 4 3 d Pass Fail Pass See 5 1 4 4 132 The Execute board will default to a shorted leads protection in a hazardous situation criteria 8 is the only incomplete criteria While all the detection circuits and software were tested functional the overarching safety code could not be de
120. iv 107 ek Run Figure 80 500mA load AC 20mV div VG VG Current mA Voltage V Voltage V 25011 10v S00mA 0 9 863 9 834 12 000 50 9 841 9 751 100 9 796 9 667 10 000 150 9 771 9 595 200 9 729 9 528 8 250 9 700 9 461 i 300 9 662 9 372 6 000 VG Before 350 9 617 9 282 Aer PTE 400 9 573 9 193 gt 450 9 527 9 081 T 500 9 463 8 991 550 9 416 8 858 600 9 349 8 702 650 3 900 3 420 0 000 50 100 150 200 250 300 350 400 450 500 550 600 650 700 700 Figure 81 Load testing with constant current During the experiment the PTC did not trip open the current limit kicked in before It introduces significant load regulation 9 834V 8 991V Load regulation 100 19 040 ___ 100 9 38 Vuax LoAD 8 991V Eq 18 108 The next design will use a less resistive PTC 5 1 3 3 5V SMPS Load Testing 1 ii Figure 82 500mA load DC 1V div ek Fun ution Figure 83 500mA load AC 20mV div 109 5V Current mA Voltage V Voltage V 562163 5 500mA SMPS 0 4 925 4 865 6 000 50 4 914 4 820 5 000 F 100 4 895 4 768 150 4 881 4 719 4000 200 4 880 4 675 3 000 250 4 869 4 619 300 4 858 4 563 2 000 350 4 847 4 507 400 4 836 4 451 1000 450 4 825 4 390 E 500 4 805 4 317 F gt E 550 4 791 4 239 d 600 4 780 4 138 o 650 4 769 3 949 5V Before 45V After 700 4 746 0
121. l Coventry UK 21 24 March 1994 M A Rosly Z Samad M F Shaari Feasibility Studies of Arduino Microcontroller Usage for IPMC Actuator Control 2014 IEEE International Conference on Control System Computing and Engineering 28 30 November 2014 Penang Malaysia G A Pratt M M Williamson Series Elastic Actuators MIT Artificial Intelligence Laboratory and Laboratory for Computer Science 1995 135 11 12 13 14 15 16 17 18 19 E J Rouse L Mooney and H Herr Clutchable series elastic actuator Implications for prosthetic knee design The International Journal of Robotics Research 9 October 2014 A Harris K Katyal M Para J Thomas Revolutionizing Prosthetics Software Technology 2011 IEEE International Conference on Systems Man and Cybernetics SMC 9 12 Oct 2011 M Grebenstein A Albu Schaffer T Bahls M Chalon O Eiberger W Friedl R Gruber S Haddadin U Hagn R Haslinger H Hoppner S Jorg M Nickl A Nothhelfer F Petit J Reill N Seitz T Wimbock S Wolf T Wusthoff G Hirzinger The DLR Hand Arm System 2011 IEEE International Conference on Robotics and Automation May 9 13 2011 Z Xie J Zhao J Huang K Sun G Xiong H Liu DSP FPGA based Integrated Flexible Joint Robot The 2009 IEEE RSJ International Conference on Intelligent Robots and Systems October 11 15 2009 Diftler 1 5 Me
122. l the inputs and outputs that are connected to the Expansion connector have the same basic protection circuit The E suffix denotes the pin that is linked to the external world while the same net without the suffix is linked to the circuit CLUTCH POW HALL3E ENCI IE t2 t EXPIOE EXPITE GND GND Figure 32 Expansion connector A special diode pair TI TPD4E004 is connected to each pin as close to the connector as possible The TPD4E004 is designed to provide ESD protection up to 8 kV IEC 61000 4 2 Contact Discharge The diodes having a forward voltage of 0 8V they will clamp a steady input voltage from 0 8V to 5 8V In case of an 8kV ESD contact discharge the voltage will be limited to 80V 100x less The PSoC 5 is protected up to 500V the extra diodes will prevent pin destruction TYPICAL OPERATING CHARACTERISTICS continued Amplitude V 0 5 10 15 20 25 30 35 40 45 50 Time ns Figure 5 IEC ESD Clamping Waveforms 8 kV Contact 52 Figure 33 TPD4E004 ESD Clamping 3 Figure 34 ESD diode routed right under the Expansion connector A series 100 ohm resistor limits the current to 5 0 100 50mA in case a high output is shorted to ground The same series resistor will also limit the current when the diodes are clamping the input voltage The maximum rating for PSoC 5 pins is 41mA A resistor of 120 ohm should be used inst
123. le named Common Commands txt Copying amp pasting long commands will be faster than typing them o It s useful to open one Terminal program with multiple tabs Shift Ctrl t to open a new tab I usually have tabs named BBB SVN SCP OpenOCD and Misc e Connecting to the Plan board BBB e Transferring a program to the Plan board BBB e Executing the program e o For the first test it is recommended that you use the single command plan executable named plan in Release Single folder scp plan to the BBB o In your BBB terminal confirm that you transfered the executable by calling 15 on the Desktop o plan default info will list the available FlexSEA commands flexsea ubuntu root beaglebone flexsea_bbb_init FlexSEA is ready to be used root beaglebone home debian Desktop plan default info FlexSEA Plan v1 0 02 11 2015 FlexSEA SPI Mode 0 Bits 8 Max Speed Hz 5000000 fcp list 1 cmd imu read arg 2 fcp list 2 cmd encoder write arg 1 fcp_list 3 cmd_encoder_read arg fcp_list 4 cmd_strain_read fcp_list 5 cmd_strain_config fcp list 6 cmd_clutch_write cmd_analog_read cmd_ctrl_mode_write ar cmd ctrl i gains write arg 3 fcp_list 10 cmd_ctrl_p_gains_write arg 3 fcp list 11 cmd ctrl o write arg fcp_list 12 cmd_ctrl_i_write arg fcp_list 13 cmd_ctrl_i_read arg fcp_list 14 cmd_mem_read arg 2 fcp list 15
124. lications By maximizing the use of FlexSEA Execute and FlexSEA Manage the FlexSEA Plan computing requirements are lowered A slower device can be used or it can be placed in sleep mode between actions Eliminating FlexSEA Plan and programming the high level algorithms on FlexSEA Manage or FlexSEA Execute can be extremely energy efficient Size mechanical integration The Execute and Manage boards were designed to be as small and light as possible They have an integration level comparable to commercial products while having accessible connectors for inputs and outputs 26 3 Hardware design 3 1 FlexSEA Execute At its core the FlexSEA Execute board is a BLDC motor driver It is specialized for robotic and prosthetic applications The high level design goals were to maximize the system integration small physical dimensions large number of integrated peripherals and interfaces support for externalinput and output devices allow fast communication and networkability via the use of a fast multi drop communication interface and have built in safety features The design went through three major revisions this document focusses on the last generation FlexSEA Execute 0 1 Figure 5 FlexSEA Execute 0 1 Hardware 27 Figure 6 presents the logical organization of the FlexSEA Execute 0 1 board In orange are the schematic sheets and in grey are the sub circuits present on certain sheets Temperature Figure 6 FlexSEA Exec
125. lify a new user s life Embedded computer coprocessors TI Sitara processor used on the BeagleBone Black has two PRU that could be used to synchronize processes and manage communication A user space driver needs to be written 103 5 Unittests 5 1 FlexSEA Execute 5 1 1 Motor Half Bridge Load test FlexSEA Execute 0 1 was attached to its heat sink 6061 aluminum black anodization 5 14cm with 5 M2x4 screws A TFLEX 220V0 0 508mm silicone elastomer thermal transfer pad was placed between the PCB and the aluminum heat sink The load was a BK 8500 programmable DC load 120V 30A 300W connected to phases and B The power was coming from a 40V 15A Kepco linear power supply Temperature was measured with the onboard bridge temperature sensor Microchip MCP9700A Its output was read on a Tektronix MDO3024 mixed domain oscilloscope as an analog voltage Vour T4 Vosc Eq 16 Where Tc 10mV C and Vorc 500mV Vour Voyr 0 5V 10mV Eq 17 The initial temperature after the circuit was powered for a few minutes and before the load was applied was 30 C 24 t was noted during the assembly that the PCB was bowing due to the thickness of the transfer pad Better options such as the TPCM 585 0 127mm 0 02 C W phase change were used after this test was completed 104 Figure 77 Experimental setup A PWMduty cycle of 90 was used for the test The circu
126. ll only certain tools It can be optimized by grouping similar tasks like all the bashrc edits Getting the sources installing the common software e Before you get started All the commands below assume that your user name is flexsea Start by creating a folder named FlexSEA on the Desktop home flexsea Desktop FlexSEA All the commands that need to be typed in a terminal are in orange The text that needs to be pasted in text files is in light blue If you are not familiar with Linux commands read this http www dummies com how to content common linux commands html If you are not familiar with nano read this http mintaka sdsu edu reu nano html Install Subversion sudo apt get install subversion 185 Eclipse Create biomech ee svn folder home flexsea Desktop FlexSEA biomech ee svn navigate to that folder and checkout the code repo svn co https src media mit edu r biomech ee Code You need to get access to the SVN first Ask JFDuval the admin Accept the key and enter your SVN password Done you have all the FlexSEA code You ll be using the code in Code flexsea 1 0 Download Eclipse C Luna Make sure to get the right version for your operating system 32 64bits http www eclipse org downloads download php filez technology epp downloa ds release luna R eclipse cpp luna R linux gtk tar gz Extract via to FlexSEA It will create
127. local home debian Desktop plan home flexsea Documents 2 scp can be used to move multiple files folders etc More info http www hypexr org linux scp help php 4 Atthis point if you 5 on the BBB desktop you ll see the plan program Tip if you need to send plan and planm you can navigate to Code flexsea 1 0 and use the following two commands scp Release Single plan root amp beaglebone local home debian Desktop amp scp Release Multiple planm root amp beaglebone local home debian Desktop 5 BBB x SCP X OpenocD SVN x jfduval ubuntu Documents jfduval ubuntu Documents biomech ee svn Code flexsea_1_0 plan scp Release_Single plan root beaglebone local home debian Desktop Debian GNU Linux 7 x jfduval ubuntu Documents x BeagleBoard org BeagleBone Debian Image 2014 04 23 Support FAQ http elinux org Beagleboard BeagleBoneBlack_Debian root beaglebone local s password 100 42 42 2KB s 00 00 n jfduval ubuntu Documents biomech ee svn Code flexsea_1_0 plan I Update your SVN 03 19 2015 1 Ina terminal navigate to home flexsea Desktop FlexSEA biomech ee svn flexsea 1 0 209 2 Update the SVN with the command svn up 3 If asked accept the key and provide your Media Lab username and SVN password Using a pre configured BeagleBone Black Plan board 03 16 2015 e Before you get started e o If you are using the pre configured VM look on the Desktop for a fi
128. luF Z GND GND GND GND GND GND GND Figure 40 10V 500mA SMPS Figure 41 Compact routing using polygon pours D9 C38 and C39 were added to provide brown out protection Size constraints limited the capacity of C38 and C39 leading to an extremely short protection period C40 L2 and C8 form a PI filter It is used to minimize the output noise to avoid transferring that switching noise down 58 to the 5V supply F1 is a PTC Positive Temperature Coefficient also known as a resettable fuse The circuit was designed with a 650mA current limit by selecting Rs 0 2Q the PTC should only trip in case of a catastrophic failure 3 1 10 4 TPS62163 5V 500mA VG D27 MBR0580 TP 5V 0580 14 F2 VIN sw BRL LIN tN P 2 2 2uH luH 500 EN vos 6 n R16 PGND p 110k C33 C34 5 C35 C36 ir T UND 2 1 22uF 10uF 0 4 TPS62163 7 lt GND GND GND GND GND GND Figure 42 5V 500 5 5 Figure 43 Compact routing using polygon pours 59 3 1 11 Future Work and Circuit Modifications List of modifications that do not require circuit modifications only BOM changes e Lower the C resistor pull ups R45 R46 to 1 8kQ currently 4 7 e Change the IO protection resistors R10 R13 R64 R65 to 1200 currently 1000 e Less resistive PTCs F1 F2 e Lower the Gate resistor value
129. mable Features 8 analog inputs are available on the Expansion connector To minimize the number of external components required to interface with common sensors 4 different circuits are used e ANO amp AN1 1 or 10kHz low pass filter unity gain buffered AN2 amp AN3 1 or 10kHz low pass filter IC programmable gain 1 G 10 8 bits AN4 amp AN5 unity gain buffered 67 e AN6 amp AN7 programmable pull down 0 lt R lt 10kQ to use as a voltage divider unity gain buffered All the inputs have ESD protection and weak pull downs to force a low level when the input is floating 03 DIC Z TPD4E004DRYR GND GND GND Figure 52 ANO amp 1 1 10kHz LPF G 1 MCP4661T 103 C10 100nF DID TPD4E004DRYR GND GND GND GND Figure 53 AN2 amp AN3 1 10kHz LPF 1 lt G lt 10 9 x TPD4E004DRYR GND GND Figure 54 AN4 amp AN5 Buffered input 68 3V3 DID TPD4E004DRYR MCP6004 MCP4661T 103 GND Figure 55 AN6 amp AN7 Programmable voltage divider Four 2 digital potentiometers Microchip MCP4661 dual potentiometer U3 amp 04 used to adjust the gains and the voltage divider resistances They share the same lC bus as the IMU 3 2 3 2 Digital Inputs amp Outputs 9 digital signals are available on the Expansion connector en TPD4E004DRYR GND GND Figure 56 Protected Digital IO Table 7 Special Digital IO functi
130. nchmarks the conservative value of 6Mbits s was used 5 3 2 Communication Plan amp Execute Criteria Plan can send or receive a minimum of 1000 communication packets of a minimum of 20 bytes each from Execute 160kbits s for pure writing 320kbits s for half duplex read write The following test code was used on Plan Plan lt gt Manage Communication void test code plan manage comm void printf Plan lt gt Manage Communication Speed Test CodeNn while kbhit 121 Prepare the command tx cmd switch FLEXSEA MANAGE 1 CMD READ payload str PAYLOAD BUF LEN Communicate with the slave send cmd slave Delay usleep 100 usleep is based on cycles and is therefore not accurate The actual delay measured is 460 5 not 100 Figure 95 and Figure 96 were captured with a Saleae Logic Logic16 USB logic analyzer connected to the SPI port linking Plan BeagleBone Black and Manage O 1 2 MOSI 3 MISO 4 Execute RX gt YAni mnn Ti A Figure 96 Communication Plan amp Execute zoom on the 1st packet The refresh rate is 1 68kHz 68 above the criteria For every transaction 48 bytes are sent and received full duplex 96 bytes for an effective half duplex data rate of 645kbits s 4x the criteria The full duplex data rate is 1 3Mbits s As can be seen on the screen captures the communication at 6Mbits s half the m
131. nd Figure 98 show two different measurements made to confirm the 2Mbits s 123 CH Fi 11 Apr 2015 A ZUG C EH 10M points 1 44 V 18 32 09 Figure 97 RS 485 Data 48 bytes 173us 36 bytes 10 bits character 2 08Mbits s To confirm one bit mas measured CH 2 506S s 11 2015 int 10M points 1 44 V 18 35 17 Figure 98 RS 485 Data zooming 1 bit 1 520ns 1 92Mbits s The RS 485 bus has the expected baud rate The two busses present on FlexSEA Manage have the same timings 5 3 4 Data Logging Criteria Record sensor values in a human readable text files A minimum of 8 bytes of data can be logged at least every 10ms 100 2 6 4kbits s Test code used void flexsea_console datalogger uint8 t slaveid uint8 t offs unsigned int numb 0 uint32 t tmp 0 lines 0 good 0 Clear terminal system clear printf FlexSEA Plan Datalogging n printf n n Log file FILE logfile time t t time NULL struct tm tm localtime amp t File will be named with the date amp time char str 100 sprintf char str log d d d d d d txt tm tm year 1900 tm tm mon 1 tm tm mday tm tm hour tm tm min tm tm sec logfile fopen str wt printf Logfile created s Nn str printf nPress any key to exit n n while kbhit
132. o describe components or systems that can be bought DAC Digital to analog converter GCC GNU Compiler Collection open source compilers GDB GNU Debugger GNU GNU s Not Unix Unix like computer operating system composed wholly of free software High side switching a high side switch is placed between the positive supply and the load The other terminal of the load is connected to the negative supply 12C I C Inter Integrated Circuit computer bus used to link low speed peripherals in embedded systems and computers IC integrated circuit Low side switching a low side switch is placed between the negative supply typically the system ground and the load The other terminal of the load is connected to the positive supply MCU pC Microcontroller unit a single computer chip designed for embedded applications MOSFET metal oxide semiconductor field effect transistor OpAmp Operational Amplifier PCB printed circuit board Pulse width modulation In this context PWM is used to encode a variable voltage as the average value of a digital pulse train 137 RS 485 standard defining the electrical characteristics of drivers and receivers for use in balanced digital multipoint systems RX short version of reception SMPS Switched mode power supply an electronic power supply that incorporates a switching regulator to convert electrical power efficiently SPI Serial Peripheral Interface bus synchronous serial communic
133. oad parse str function If the Receive ID belongs to another board the packet will be rioted to the appropriate interface If the packet belongs to the board that received it it will be decoded by the appropriate RX function as determined by the P CMD1 field 21 http en wikipedia org wiki Serial Peripheral Interface Bus 22 http en wikipedia org wiki Rs 485 81 4 1 5 Hierarchy As mentioned before to avoid data collisions and keep the communication protocol as simple as possible a strict hierarchy is used The Master always initiates the communication Upon request a Slave will transmit data to its Master a Reply message In this convention Execute is always a Slave to manage and Manage is a Slave to Plan There is no fundamental reason forcing us to keep the system hierarchical With software modifications two Execute could talk together one acting as the Master and the other as the Slave A set of files used by all the FlexSEA boards is available in the source common sub directory They contain all the communication stack They are designed to be hardware agnostic they can be compiled with the three main projects Plan Manage and Execute 4 1 6 Special Commands To maximize the efficiency of the network communication one needs to minimize the overhead minimize the number of extra bytes required to send the information and minimize the computing requirements Using many commands per communication string is an eff
134. ocess High level languages such as Python can be used saving experimental data is as simple as writing to a text file and interacting with the system can be done via USB or WiFi FlexSEA Plan should be used when ease of development is important and when complex algorithms and control schemes require significant computing power 2 3 2 FlexSEA Manage FlexSEA Manage is used for mid level computing tasks It serves as an interface between FlexSEA Plan and FlexSEA Execute communication protocols translation data routing time sharing It has an Expansion connector that can interface with a wide variety of input and output devices Data acquisition processing and aggregation can be done on this board thus unloading FlexSEA Plan from these simple tasks For applications that do not require intensive computing FlexSEA Plan can be taken out of the system and FlexSEA Manage can host the high level state machines 2 3 3 FlexSEA Execute FlexSEA Execute is an advanced brushless motor driver Wearable robotics applications require different control loops than the typical position and current controllers found on commercial drives FlexSEA Execute has onboard sensors 6 axis IMU temperature voltage current interfaces strain gauge amplifier processing power and connectivity to make it possible to close most control loops onboard It is well suited for the series elastic actuators SEA 10 commonly used in prostheses 2 4 System Archite
135. off on FlexSEA Execute the user call cmd exp clutch FLEXSEA EXECUTE 1 CMD WRITE tmp payload xmit PAYLOAD BUF LEN 0 The tx cmd exp clutch function will fill the payload buffer with the fields specified in Figure 63 79 Emitter ID Receiver ID Number of commands sent First command First data byte if needed Figure 63 Payload bytes The payload will be framed by the data link layer before it is ready to be transmitted 4 1 2 Data link Layer To preserve data integrity we cannot send raw bytes on the physical layer The FlexSEA communication software automatically adds a header and a footer an indicator of the number of bytes the frame a packet ID a checksum to detect invalid data and escape characters Figure 64 shows how the payload generated by the Application layer is packaged 0b11101101 0 127 0b11101110 237d OxED 238d OxEE Start of frame Number of Unique packet Error End of frame Pa tes Figure 64 Packaged Payload High values are used for the Header Footer and Escape bytes to avoid confusion with the command codes The Sequence byte is used to keep track of the commands exchanged between the boards and to detect missed packets At this point the command is ready to be transmitted on any physical bus 19 http en wikipedia org wiki Escape character Not implemented in the current software release 80 4 1 3 Physical Layer The system is designed to be
136. on Eq 1 For prostheses a safe fail safe mode is to short the leads of the motor maximizing the mechanical damping Given a large enough transmission ratio and a small enough shorted lead resistance a patient could keep walking on his or her unpowered device Failing with the motor bridge open is a hazardous situation since the reduced joint stability may cause the patient to trip and fall A disconnected or completely empty battery means that the control logic will lose power and that the H Bridge MOSFETs will turn off One solution is to use a backup battery to power safety circuits but there are many downsides cost volume finite lifetime Another option used in this design is to design a circuit that will short the leads when un powered To achieve that we used depletion mode MOSFETs 40 D SL a 9 9 G G 2 m m lt 9 o s 69 R50 a oo 5 gt 200k SZ N GND GND GND GND GND 2 D D z 3 G 2 5 58 x 99 as GND GND GND GND D E p 8 3 G G Z 5 sy Se a 95 95 as x N N GND GND GND GND Figure 19 Shorted leads protection implemented with depletion mode MOSFETs Q6 C53 28A1774G R48 2 3 SL GATE R47 th 9 T 100nF D19 SDM40E20LS 7 F GND GND GND Figure 20 Shorted leads protection negative voltage generation and gate control 41 KZ volt 2
137. ons Signals Special function DIOx0 1 12 2 DIOx2 3 UART3 DIOx 4 5 6 7 SPI6 69 For DIO2 to 0108 a series 1 resistor limits the current to 3 3V 0 10000 3 3mA in case a high output is shorted to ground The same series resistor will also limit the current when the diodes are clamping the input voltage The maximum rating for STM32 pins is 25mA DIOO and DIO1 do not have pull downs and series resistors to prevent conflicts with I2C For more info about the ESD protection please refer to Section 3 1 8 IO Protections 3 2 3 3 Power Outputs Two high side switched power outputs are available on the Expansion connector VB needs to be provided by the user When used with AWG 28 crimps the contacts are rated for 1A Both outputs are also rated for 1A their total should not be more than 1A AB VB QI FDN5618P GND Figure 57 1 of 2 power outputs The thermal calculations are simpler than for the Execute clutch output see 0 because these drivers not intended to be used with PWM The worst case of the FDN5618 5 is 0 3150 and the junction to ambient thermal resistance is 270 C W PDnzgsisrivE Rps oN 1A 0 315 0 315W Eq 12 70 Eq 13 Itleaves 30 margin before the maximum junction temperature is reached 270 C W being for the smallest pad possible it is expected that the thermal resistance will be lower in the curr
138. ot a croiss compiler You can test your work by opening a terminal navigating to the 174 Debug directory cd Desktop FlexSEA biomech ee svn Code flexsea_1_0 plan Debug and launching Plan with plan default info You will see the list of supported FlexSEA commands o Release Single one task per program call Convenient for sending commands on the terminal as it will give you feedback o Release Multiple multiple tasks per program call Use this to interface with Python or other languages as it s much faster than spawning a new instance of the program every time you want to send a command to a board The Release versions are cross compiled for the BBB They will not execute on your host computer To test your work you have to copy the executables to the BBB All the details are in Using a pre configured BeagleBone Black Plan board Connect Execute to Manage 03 19 2015 For this experiment we are using asynchronous half duplex RS 485 between Manage and Execute It requires a single twisted pair We use the connectors 1 amp 1 By convention A will have an orange wire while B will have a blue wire Manage 0 1 OOO 2 Y 0000 00000000000 0 0 0 EE Z S O When the board is flat a table the twisted pair is in the top row of the connector Execute 0 1 175 03 17 2015 Part list 1x Plan BBB 1x Manage 1x USB Mini B c
139. ous TP1 TP2 Transmit on TP1 TX12 receive on 2 RX12 1 TP2 Transmit on 1 TX12 receive on TP2 RX12 clock 23 C24 C25 26 27 C28 Note For port 2 replace RX TX 12 by 45 and use 4 to 6 100nF 100nF 100nF 100nF 100nF 100nF Biomechatronics Title Manage 6x RS 485 MIT Media Lab E 14 274 k EC 75 Amherst Street mit Size Letter Number Revision Cambridge MA 02139 l media GND GND GND GND GND GND Date 2015 04 08 Time 12 52 48 Sheet of USA lab File FLEXSEA MANAGE 0 1 RS 485 SchDoc 155 1 2 3 4 Analogin BIOM FLEXSEA MANAGE 0 1 AnalogIn SchDoc DigitallO BIOM FLEXSEA MANAGE 0 1 DigitalIO SchDoc PowerOut BIOM FLEXSEA MANAGE 0 1 PowerOut SchDoc Title Manage Expansion IOs Biomechatronics MIT Media Lab 14 274 75 Amherst Street base Detter Nahe Cambridge 02139 LH media Date 2015 04 08 Time 12 52 47 Sheet of USA lab File BIOM FLEXSEA MANAGE 0 1 IOs SchDoc 1 2 3 4 156 2 3 4 3V3 3V3 5 ae E m o m 8 2 2 z 21 zi OnF SZ TPD4E004DRYR GKp GND GND GND 4N3 333 SZ TPD4F004DRYR GND GND SZ TPD4F004DRYR GND GND NZ TPD4F004DRYR GND GND MCP4661T 103 MCP4661T 103 43V3 DID TPD4F004DRYR 3V3 5
140. ple sensors being logged at 500H Encoder Coumn B 2000 4000 6000 8000 10000 12000 Z Position analog CoumnH X y Z Figure 75 Logging Data at 500Hz 4 4 2 High level state machine in C The following code example demonstrates all t he functionalities of FlexSEA in one simple example The code comments guide the user through the configuration of a log file the initialization of the Execute board in Current Control mode the writing and reading operations the data logging and displaying etc Demonstration test code Calling plan Motor is placed in current control mode execute 1 shuobot will call this Current will change periodically reset it to 0 will be slow because of Stream When th ncoder gets out of limit we This code will both Stream and Log Log The final application should log but no static void shuobot demo 1 void unsigned int numb 0 uint32 t cnt 0 int16 t current 0 open 0 uint8 t enc rw KEEP int32 t enc cnt 0 t Stream 98 uint32 t lines 0 good 0 tmp 0 Log file FILE logfile time t t time NULL struct tm tm localtime amp t File will be named with the date amp time char str 100 sprintf char str log d d d d d d txt tm tm year 1900 tm tm mon 1 tm tm mday tm tm hour tm tm min tm tm sec logfile fopen str wt prin
141. possible to add functionalities to the system by simply plugging additional cards Hardware and software encapsulation is used to provide high performance real time control of the actuators while keeping the high level algorithmic development and prototyping simple fast and easy Simplest full stack system Remote Computer Additional output Additional input devices devices Brushless motor sensors FlexSEA Plan Embedded computer for high level computing Can run a full Linux operating system and execute Python or Matlab scripts Can connect to the network through WiFi or Bluetooth Currently a BeagleBone Black COTS 169 Development Tools All the development is done in Linux but it could be done in OSX or Windows An Eclipse project allows the user to compile for host debugging and to cross compile for the BBB FlexSEA Manage mid level computing Deals with all the sensor functions data acquisition signal processing and aggregation the simple output devices including visual and audible notifications clutches and solid state relays and sends commands to the motor driver Has a simple API and protocol to communicate with the embedded computer 2x G 1 2x 1 lt G lt 10 2x 0 10k 1 10kHz LPF Divide 170 S T DET wut U10 4 84 4 445 4 25 RA RAT Development Tools All the Manage code is in Eclipse To program and debug we use an STLink v2 and OpenOCD FlexSEA
142. r in C Section 4 4 2 d Demonstrate how to use FlexSEA in Python Python calling the C program Section 4 4 2 The system can be used without the Plan board by executing code on Manage Anew user can unbox a FlexSEA kit 1 Plan 1 Manage 1 Execute and using only the provided documentation and tools can read one sensor and control one actuator from Linux in less than two business days 16h Sections 10 4 and 10 5 The Execute board can run an impedance loop at more than 1kHz without being connected to any other board Section O The Plan board can communicate with an Execute board through a Manage board a All serial interfaces SPI and RS 485 should have a minimum bitrate of 2Mbits s Sections 5 3 1 amp 5 3 2 b Plan can send or receive a minimum of 1000 communication packets of a minimum of 20 bytes each from Execute 160kbits s for pure writing 320kbits s for half duplex read write Section 5 3 2 The Manage board can connect to more than one Execute board a Minimum of two Execute boards b Both RS 485 serial interfaces should have a minimum bitrate of 2Mbits s Section 5 3 3 Plan can be connected to one Manage and two Execute and send or receive a minimum of 1000 communication packets of a minimum of 20 bytes each from each Execute total of 320kbits s for pure writing 640kbits s for half duplex read write Section 5 3 2 The Execute board will default to a shorted leads protection in a hazardous s
143. raw E VF4v5 J gt R2 c1 D2 i V1 470 400 D1 BAT54 T c2 R1 Da 54 100n 100k lt Vv PULSE 0 5 0 1n 1n 0 5u 1u 0 tran 2m Figure 21 Spice simulation voltage inverter There is inherent safety in this circuit To turn the MOSFETs off we need a negative voltage this voltage is only generated when the Safety CoP clocks the inverter circuit When there is no power no negative voltage or no gate signal the MOSFETs are ON shorting the leads The Ros on resistance of depletion MOSFETs available at the time of design was either large few ohms or the devices were extremely large The CPC3703 are relatively small cheap and not too resistive By using 3 devices in parallel we get 1 330 and 1 8A of pulsed drain current This current rating is not enough to handle all the energy present in a system that would suddenly get disconnected The decoupling capacitors and the brownout protection circuits will keep the logic circuits powered for a few milliseconds after the battery gets disconnected The software after detecting a loss of power will use the h bridge MOSFETs to absorb most of the energy then enable the depletion mode MOSFETs for the unpowered state 42 3 1 4 RS 485 SN65HVD75 GND Figure 22 One of the 3 RS 485 transceivers present on FlexSEA Execute Mode Clock plex Twisted pair s 1 Asynchronous Half Transmit and receive on TP
144. river schematic Locking the position of a motorized joint requires power even when there is no motion This is an inefficient use of energy 2 Designs such as the CSEA Knee use an electro magnetic clutch to hold a joint in place without requiring power from the motor 2 When not engaged the air gap between the two pieces of the clutch reduces the attraction force of any magnetic field that the clutch can generate More current is required to engage the clutch than is necessary to keep it locked Using PWM it is possible to use maximum power to engage the clutch then reduce the voltage applied across its terminal as an energy saving feature Use of a high side switch is preferred because it is typical to link the metal chassis of prostheses to ground and some clutches have their casing grounded Using a high side switch can simplify the electromechanical integration The power requirements being low it is possible to use a P Channel MOSFET as a switch D13 is used as a free wheeling diode for inductive loads as a protection for Q3 48 3 1 6 1 P MOSFET power dissipation The clutched used in the experimental setup and in the CSEA Knee is rated for 24V 250mA 6W The unit in hand was tested at 242mA To accommodate bigger clutches and other output devices the calculations will be done for 24V 10W 417mA used at 10V The current at 10V will be 174mA Using an FDN5618P P MOSFET PDnzsisrivE oan Vour Vin
145. rom the same family as on Execute another PSoC would have simplified the development process no PSoC had enough computing power 1 05 to fulfill all the requirements 100DMIPS 62 10515 Instead an industry standard Cortex M4 core was implemented to benefit from the Floating point Unit FPU Many vendors license the Cortex M4 Texas Instruments Atmel Freescale STMicroelectronics NXP etc The STM32F4 family from STMicroelectronics was selected primarily because it has a 15 With the newly released chip scale BGA package more 105 are available then at the time of this design 63 large base of customers and part references affordable development tools and comprehensive public documentation ART Accelerator H H Z Upto 2x US820 OTG FS HS i STM32F439 512Kto m S STMs2F429 0 2 2 spes que 91 USART SPI i STM32F437 H 1 3 PS audio PLL STM32F427 80 1 2 256 2 B 50K6 un a K i STM32F407 1M u Upto3x 12 bit ADC 04105 STM32F415 2 512Kto z i lemmar 8 192 2 Extemal memory controller except ACU J 2500 2 lt s forSTM32F411 E STM32F401 a 5 RUN STOP Small DMA Batch T Flash Dynamic Ex 5 c current current package Acquisition Low voltage 1 7 to MHz KB KB Efficiency i pA mm Mode 1 STM32F411 100 25810512 128 Down to 100
146. round Using GDB DSF Hardware Debugging Launcher Select other Encoding Default inherited UTF 8 Other A Workspace File System Apply Revert 179 Always start OpenOCD in a terminal openocd s Desktop FlexSEA embedded arm openocd bin share openocd scripts f interface stlink v2 cfg f target stm32f4x_stlink cfg first To program the chip build in Release mode then in a terminal openocd s Desktop FlexSEA embedded arm openocd bin share openocd scripts f interface stlink v2 cfg f target stm32f4x_stlink cfg c init c reset halt c sleep 100 c wait_halt 2 c flash write_image erase manage elf c sleep 100 c verify image manage elf c sleep 100 c reset run c shutdown FlexSEA Virtual Machine 03 16 2015 The Installing the Plan amp Manage Development Environment on your host computer note contains a lot of cryptic statements and can be intimidating To simplify the user s life I created a virtual machine VM with all the tools pre installed I m using VMware Workstation You can get it from IS amp T http ist mit edu vmware workstation Note The key is in the compressed folder Details on the installation and license key http kb mit edu confluence display istcontrib VMware Workstation 10 0 x for Windows Installing or Upgrading As soon as I installed 11 0 x and started it it offered an update to 11 1 It un installed 11 0 and installed 11 1
147. rr else motor current shifted measured curr CURRENT ZERO ToDo above code seems complex for no valid reason 91 At this point motor current is always a positive value This is our measured value Error and integral of errors ctrl current error uint wanted curr motor current Actual error ctrl current error sum ctrl current error sum ctrl current error Cumulative error Saturate cumulative error if ctrl current error sum gt MAX CUMULATIVE ERROR ctrl current error sum MAX CUMULATIVE RROR if ctrl current error sum lt MAX CUMULATIVE ERROR ctrl current error sum CUMULATIVE ERROR Proportional term curr p int ctrl current gain I KP ctrl current error 100 Integral term curr i int ctrl current gain I KI ctrl current error sum 100 Add differential term here if needed In both cases we divide by 100 to get a finer gain adjustement w integer values Output curr curr p curr i Saturates PWM if curr pwm gt POS PWM LIMIT curr pwm POS PWM LIMIT if curr pwm 0 Should not happen curr pwm 0 Apply PWM motor open speed 2 curr pwm sign Integrated to avoid a function call and a double saturation Write duty cycle to PWM module avoiding double function calls CY SET 16 1
148. rrors in the communication timings Table 4 Error versus baud rate Baud rate USARTDIV Rounding error Error 2M 2 625 0 0 2 5M 2 100 0 025 1 19 3 33M 1 575 0 050 3 17 To minimize the communication errors 2Mbits s is used That limit can easily be overpassed by using synchronous communication SN65HVD75 transceivers were selected for their high tolerance against ESD events 12kV small size and wide availability No dual ortriple transceivers offered the same protection level integration was sacrificed to increase robustness The 8 TSSOP was only selected because of a bad filter selection on Digikey While designing the FlexSEA Manage 0 1 board it was found out that a 3x3 mm 8 SON package is available The latter one is used on FlexSEA Manage and will be used in the next FlexSEA Execute revision 44 3 1 5 Strain Gauge Amplifier Strain gauge load cells are used as force and torque sensors in industrial and research applications Due to the commoditization of products such as digital scales it is now possible to purchase inexpensive sensors The sub millivolt output signal range isn t suited for typical ADC inputs amplification is required The large common mode voltage half supply is well suited for differential instrumentation amplifiers INA331 2331 single supply instrumentation amplifiers ICs are economical small and require a minimum number of external components
149. s 2 11 The MIT Autonomous Exoskeleton 19 uses a LPYSSOALTR dual axis gyroscope 500 s These parts were selected because their range covers the angular velocities and accelerations of human walking For the FlexSEA Execute board a single chip solution is used The MPU 6500 integrates a 3 axis accelerometer 2 to 16g a 3 axis gyroscope 250 to 2000 s and a temperature sensor same IMU is present on the FlexSEA Manage board An example application that would require IMUs on both the FlexSEA Manage and the FlexSEA Execute boards is a dual leg exoskeleton with waist mounted control electronics The Execute boards would be located on the feet while 12 https www sparkfun com products 10121 50 FlexSEA Manage s IMU can record whole body motion and user intent such as sitting leaning etc 3V3 3V3 3V3 3V3 3V3 L gtd GND GND MPU 6500 GND GND GND Figure 30 IMU schematic The main limitation that was found during software development was the low frequency of the 2 bus 400kHz All the devices from the same manufacturer have the same limitation preventing an easy modification Information can be accessed faster via SPI The IMUINT signal can be used to time the data acquisitions with the availability of new measurements 3 1 8 IO Protections 5 gt x a 5 Q D10C GND Figure 31 External 1 protection circuit 51 Al
150. s Preparing the FlexSEA Execute 0 1 board Hardware amp Preparing the FlexSEA Execute 0 1 board Software Testing FlexSEA Plan amp FlexSEA Manage Compile the Plan project Follow Using a pre configured BeagleBone Black Plan board to test some of your development tools and your Plan board To test Manage Compile the Manage project Connect Manage to Plan and Program debug Manage You are now ready to Read a simple sensor from Linux Pushbutton on Manage Adding FlexSEA Execute to the system 168 e Power Execute 15 28V e Program your Execute board with the latest firmware Programming FlexSEA Execute 0 1 please not that if you just followed Preparing the FlexSEA Execute 0 1 board Software you don t have to do this step again e You can now stream sensor values Read multiple sensors from Linux Execute e The next step is to Add and control an output device Execute from Linux e Atthis point controlling a motor is a simple task but it requires a new wiring harness Introduction to FlexSEA Abstract FlexSEA aims to enable fast prototyping of multi axis and multi joint active prostheses by developing a new modular electronics system This system provides the required hardware and software for precise motion control data acquisition and networking Scalability is obtained by the use of a fast industrial communication protocol between the modules and by a standardization of the peripherals interfaces it is
151. s it impossible to simultaneously optimize every aspect of the system All the constituents of the design were selected and or designed with modularity in mind to pave the way for future improvements More energy was invested in the hardware design than in the software design because typical users are more likely to improve the software than design new boards Over the life of the system it is expected that the software will be optimized thus making FlexSEA better over time 2 5 1 FlexSEA Plan Embedded computer The initial plan was to design a custom embedded computer with only the features required for our application To start experimenting before designing the BeagleBone Black was selected It is economical 555 widely available open source hardware with full documentation available and its processor the TI AM3358 has two Programmable Realtime Units PRU that can be used to efficiently communicate with peripherals making it a perfect reference for a custom design By removing multimedia features and optimizing connectors its size 89 x 55 x 15 4mm can be greatly reduced While the design efforts were focused on FlexSEA Manage and FlexSEA Execute the Internet of Things loT wave grew stronger Smaller embedded computers were released with price tags low enough to be embedded typical appliances One example is the Intel Edison At 35 x 25 x 4mm it has 500MHz processor 1GB of RAM 4GB of FLASH Bluetooth and WiFi It was d
152. s between the FLASH and the STM32 being electrically short termination should not be required R32 to R35 are included as placeholders Users can access the stored data via the USB port or via the FlexSEA network A radio module can also be connected to the Expansion connector 72 3 2 6 User Interface The same RGB LED Green LED and USB protection circuit as on Execute are used see 3 1 9 The differences are 1 the presence of a second Green LED and 2 one user button TPD4E004DRYR DSC KMT071 LHS GND GND GND Figure 59 User input Having a least one user push button in the system is convenient for demonstrations allowing one to start test code and or experiments without requiring the use of a remote computer 73 3 2 7 RS 485 GND GND 3V3 SN65HVD75 GND Figure 60 RS 485 1 3 transceivers Section 3 1 4 goes over all the details of the 3 RS 485 modes baud rate transceiver selection The differences are 1 the presence of 6 transceivers on Manage 2 the hardwired enable signals and 3 the smaller IC packages By routing all the enable DE RE signals to the PSoC Execute could use the three transceivers independently This is not the case for the Manage board the internal peripherals and pin assignments made it impossible to get the same flexibility USART1 and USART6 are used because they are clocked by APB2 84MHz while all the other UxARTs are clocked by
153. s by at least half More calculations and testing is required to find the optimal value List of modifications requiring circuit modifications The 400kHz 1 limit on the MPU 6500 is slowing down the bus If a new IMU has to be selected a 1MHz version should be considered RGB LED poor color balance The next design should use 243 249 4120 e Adda second green LED to unify the user interface with Manage e Add an external filtering capacitor for the Delta Sigma converter 0 1 to 1 0uF see component datasheet e Add SWD P1 3 to the PSoC 5 SWD connector J9 The Serial Viewer isn t supported yet but will be convenient in the future e The 5V supply should be measured e RS 485 transceivers 04 U10 011 should use the 8 SON package to save board space and unify the BOM with Manage e The position of the SWD connectors J5 J9 is not convenient They should be on the top side Swapping their position with the RS 485 transceivers would be convenient e Many expansion pins are on port 12 They are SIO and not GPIO no analog features Most of the expansion signals should support analog inputs 60 The only patch that needs to be applied to use the circuit is to lower the I C pull ups All the other changes are not problematic but will improve the quality of the design 3 2 FlexSEA Manage Figure 44 FlexSEA Manage 0 1 FlexSEA Manage is a polyvalent circuit that can have a wide range of usages depend
154. sign from DataLogger import dataLogger data Initializations master slave pty openpty cproc Popen planm stdin subprocess PIPE stdout slave stdin handle cproc stdin stdout handle os fdopen master Setup data output filename Data are saved on state machine exit trial num int raw_input Trial Number filename Test i 03132015 trial num 1 dataLogger filename txt print starting tO time time 0 0 while True Ery Data acquisition and manipulation i i 1 tl time time t0 stdin handle write execute 1 speciall 0 0 0 0 0 ONxn cout stdout handle readline Receiving values cout cout replace Remove brackets for parsing data cout cout replace vals cout split Parse values encoder int vals 0 current int vals 1 imu x int vals 2 imu y int vals 3 imu z int vals 4 101 strain int vals 5 angle int vals 6 Display os system clear print Encoder d encoder print Current d current print IMU Gyro x d imu x print IMU Gyro y d imu y print IMU Gyro z d imu z print Strain d strain print Angle d angle Delay time sleep 0 01 10ms except KeyboardInterrupt print State machine stopped by user break except Exception as e print Unexpected exception print traceback form
155. ssipation pads Increase copper area on the drain connection or select a MOSFET with a lower Drain to Source resistance The 400kHz 2 limit on the MPU 6500 is slowing down the bus If a new IMU has to be selected a 1MHz version should be considered RGB LED poor color balance The next design should use 243 249 4120 76 4 Software Design While the focus of this thesis was system and hardware design a large amount of embedded software had to be written to enable all the functionality of the FlexSEA system The communication stack shared by allthe boards required 5153 lines of C code 12030 lines of code are specific to the sub projects motor control terminal interface signal processing etc for a grand total of 17183 lines of C This section will take a high level approach to describe the software design of FlexSEA rather than diving down in the details Readers will get an overall understanding of the organization the modularity of the software and the abundance of comments combined with this document should provide anyone with enough information to use and modify the system 4 1 Communications and networking A communication protocol is a system of digital rules for data exchange within or between computers and embedded devices At the highest level intelligent information is exchanged such as set motor pwm duty cycle to 100 On the lowest level hardware level it s always exchange of electrons or
156. t the Red wire to CLUTCH_POW and the Black wire to GND Fr umm Em f l vr To simplify testing we use a big 12V LED We will connect it to the Clutch Output Use 15V to power o Ae NS i Execute 24V would be too much for that LED i 9 Nr j IQ m 1 B output 8 bit PWM output will give you maximum brightness will turn the LED off and intermediate values will dim it 173 Compile the Manage project 03 19 2015 If you are using the FlexSEA Virtual Machine you can simply e Launch Eclipse from the Desktop shortcut e The Manage project will be listed in your workspace Click on it once e You can compile the project by clicking on the Hammer icon Please note that 2 options are available o Debug use this for debugging your code the hardware with OpenOCD e o Release use this when you want to use the board in your application without requiring the programmer debugger to be connected Compile the Plan project 03 16 2015 If you are using the FlexSEA Virtual Machine you can simply e Launch Eclipse from the Desktop shortcut e The Plan project will be listed in your workspace Click on it once e You can compile the project by clicking on the Hammer icon Please note that 3 options are available e o Debug use this for debugging on your host computer This uses a native compiler n
157. tf Logfile created s Nn str Initial configuration Controller current numb tx cmd ctrl mode write FLEXSEA EXECUTE 1 CTRL CURRENT send cmd slave usleep 10000 Gains kp ki kd numb tx cmd ctrl i gains write FLEXSEA EXECUTE 1 10 10 0 send cmd slave usleep 10000 51 That code will run as long as you don t press key while kbhit Timed changes if gt PERIOD Time to change some parameters cnt 0 Change the current setpoint current CURRENT STEP if current gt MAX CURRENT current 0 Reactive changes if execl encoder gt MAX ENC execl encoder lt MAX ENC We are over the limit we specified gt overwrite to 0 enc rw CHANGE enc cnt 0 Prepare the command numb tx cmd ctrl special 1 FLEXSEA EXECUTE 1 CMD READ payload str PAYLOAD BUF LEN KEEP enc rw K 0 enc rw enc cnt current open spd FEP 99 Communicate with the slave send slave Can we decode what we received tmp decode spi rx lines good tmp Enable these 2 lines to print Stream mode system clear Clear terminal flexsea console print manage Log to file fprintf logfile 4 41 1 1 1 tm tm m
158. th a setpoint of 500 the expected current is 6 1A and the measured value is 5 94A The absolute error is only 2 6 and the transfer function is extremely linear The same controller with the same gains was tested on a Maxon EC 30 The mechanical noise made by the spinning rotor covered the controller s noise entirely 4 2 4 Impedance controller User command initial position final position maximum speed acceleration 20kHz 1kHz Figure 71 First implementation of an Impedance Controller 2014 94 With all the compiler optimizations turned off the motor_impedance_encoder function takes 6 4145 to execute It is called in the main while loop at a 1kHz frequency 4 2 5 Trapezoidal trajectory generation Computer code that can generate trapezoidal speed profile trajectories has been developed in Matlab and then translated in C The code is optimized for integer mathematic and efficient real time execution It now runs on the FlexSEA Execute board and allows the end user to command smooth position changes Acceleration 20 0L 20 0 5 10 15 Speed 100 50F 0 0 5 10 15 Position 1000 500 F 0 0 5 10 15 Figure 72 Calculated trajectory acceleration speed and position over time A proportional integral controller has been designed to control the position of the prosthetics in accordance with the calculated trajectory Figure 73 shows the commanded position of a prototype knee in one e
159. the first stage by 20 centered at half supply The offset adjustment span of 20 and the fixed gain of 105 were calculated based on experimental data 5 load cells were randomly selected and measured The worst offset was used to calculate the required compensation 10 http www ti com lit ds symlink ina331 pdf 46 usc 8 tn 9 cass 47pF pi MCP4661T 103 5V R40 m 14 2499 1 3 i PE VR2 10 mamama 5 R38 Sk USB PIA H e VREPRE MCP4661T 103 R4 C31 vam 1 100nF GND GND INA2331 Figure 27 Two stage amplification When possible internal PSoC analog components were used to simplify the circuit This is the case for the offset buffer operational amplifier the V 2 reference voltage and the VR2 DAC U5C allows the user to change the second stage gain from 5 to 105 Via software VR2 can be programmed it s on a DAC output to change the output reference Some applications use unipolar forces ex pushing only never pulling using a non half supply reference can increase the resolution of the measured force Strain Gauge ADC DelSig 1 Vdda 2 Vref J HalfV VDAC8 3 16 bit Opamp 3 i VR2 Opamp 2 VR1 PRE v mj VR1 Figure 28 PSoC Programmable Analog Blocks Strain Gauge Amplifier 47 3 1 6 Clutch RNI106MFV GND GND Figure 29 Clutch d
160. to 64 KB SPI UART PC SPI UART LIN PC SPI UART FC SPI UART LIN FS USB 2 0 FS USB 2 0 FS CAN FS USB 2 0 PS 1 Delta Sigma ADC 8 to 20 bit 1 Delta Sigma ADC 6 to 14 bit 1 Delta Sigma ADC 8 to 20 bit 1 SAR ADC 12 bit 192 ksps 12 bit 131 ksps 8 bit 192 ksps 12 bit 1 Msps 12 bit 2 SAR ADCs 12 bit Up to two DACs 6 to 8 bit Up to four DACs 8 bit Up to two DACs 7 to 8 bit 1 Msps 12 bit Up to four DACs 8 bit Up to 64 I O Up to 72 1 0 Up to 36 I O Up to 72 0 Operation 1 7 V to 5 25 V Operation 0 5 V to 5 5 V Operation 1 71 V to 5 5 V Operation 2 7 V to 5 5 V Active 2 mA Active 1 2 mA Active 1 6 mA Active 2 mA Sleep 3 pA Sleep 1 pA Sleep 1 3 pA Sleep 2 uA Hibernate Hibernate 200 nA Hibernate 150 nA Hibernate 300 nA On chip JTAG SWD SWV Requires ICE Cube and FlexPods On chip SWD Debug Debug Trace CY8CKIT 040 Pioneer Kit CY8CKIT 042 Pioneer Kit CY8CKIT 049 Prototype Kit CY8CKIT 001 Development Kit CY8CKIT 030 Development Kit CY8CKIT 001 Development Kit CY8CKIT 050 Development Kit CY8CKIT 001 Development Kit Figure 8 PSoC Families gt gt http en wikipedia org wiki PSoC 31 The PSoC 4 and 5 have modern ARM Cortex microcontroller cores The PSoC 5 family was chosen because of the higher computing power onboard USB and higher number of programmable digital and analog blocks The highest end PSoC 5 subfamily CY8C5888 was chos
161. train BYTES UINT16 buf CP DATA1 6 buf CP DATA1 7 exec ptr gt analog 0 BYTES TO UINT16 buf CP DATA1 8 buf CP DATA1 9 exec s ptr encoder int32 t BYTES TO UINT32 buf CP DATA1 10 buf CP DATA1 11 buf CP DATA1 12 buf CP DATA1413 exec s ptr current intl16 t BYTES TO UINT16 buf CP_DATA1 14 buf CP_DATA1 15 126 x Open x SVN x jfduv x jfduv x GNU nano 2 2 6 2014 4 23 21 21 39 txt FlexSEA Plan Datalogging 39 39192 32 0 0 0 1353 147 F 21 39 39192 32 0 0 0 1353 147 39 39192 32 0 0 0 1349 160 39 39192 32 0 0 0 1349 160 21 39 39192 32 0 0 0 1349 151 Press any key to exit 21 39 39192 32 0 0 0 1349 151 Loe 21 39 39192 32 0 0 0 1351 149 21 39 39192 32 0 0 0 1351 149 13844 lines logged 21 39 39192 32 0 0 0 1349 151 Log file closed 2014 4 23 21 21 57 Exiting 39 39192 32 0 0 0 1349 151 39 39192 32 0 0 0 1348 151 21 39 39192 32 0 0 0 1348 151 Sending 48 bytes 21 39 39192 32 0 0 0 1352 152 Read 21 39 39192 0 1352 152 AA AA AA AA AA 1 39 39192 1349 154 Logfile created log 2014 4 23 21 21 39 txt 2 AA AA AA AA AA 39 39192 1349 154 AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA root beaglebone home debian Desktop I 39 39192 1349 152 1349 152 1349 153 39 39192 1349 153 5 5 3 3 3 3 3 39 39192
162. used with a TXB0104 voltage level translator IC to interface an embedded computer with an IO voltage between 1 2 and 3 3V and the 3 3V Manage microcontroller 17 The 5V can come from any power supply it doesn t have to be from Plan 65 3V3 VP 3V3 53 54 100nF 100nF GND GND Figure 49 Level translation SPI R72 to R80 are series termination resistors for the fast SPI lines The output characteristics of the Plan computer being unknown and the cabling between FlexSEA Plan and FlexSEA Manage depending on applications it was not possible to calculate the proper terminations The 00 resistors are used as place holders The external reset line is connected to the base of Q5B another way of doing level shifting DSB TPD4E004DRYR GND GND Figure 50 Level shifting external reset signal 66 User code being executed on the Plan board can be stopped at any time Some situations will place the SPI bus in a bad state thus requiring either special management code on the FlexSEA Manage board or that it can be rebooted by FlexSEA Plan 3 2 3 Inputs and Outputs J2 is a 40 pins Molex Pico Clasp dual row right angle connector It is used by users to access the 9 digital 1 05 the 8 analog inputs two power outputs and some supplies It also hosts 6 twisted pairs for RS 485 PWROUTO PWROUTI DIOEO DIOE6 GND GND Figure 51 Expansion connector 3 2 3 1 Analog Inputs with Program
163. ute System Diagram Table 2 FlexSEA Execute 0 1 Specifications Microcontroller Special features CPU RAM IOs Package Software IDE Co processor s Supply voltage V 15 24V Electrical Motor current A 20A Continuous Intermediate supply 10V 500mA SMPS Logic supply 5V 500mA SMPS Type 3 phase brushless BLDC Sensor s Hall effect optical encoder Motor Commutation Block Sinusoidal FOC PWM 12 bits 20kHz 10 bits 78kHz or 9 65 bits 100kHz Reference PSoC 5LP CY8C5888AXI LP096 Programmable analog and digital blocks 80MHz ARM Cortex M3 256KB RAM 62 105 PSoC Creator 3 1 mix of C ARM GCC 4 7 3 and graphical programming PSoC 4 CY8C4245LQI 483 Serial interface Type Bandwidth 3x Half Duplex RS 485 can be full duplex synchronous 2 10Mbps Onboard USB Full Speed FS 12 Mbps 28 Current sensing Hardware Software control 0 0050 resistor 20kHz Proportional Integral controller Safety features Overvoltage Overcurrent Locked rotor Motor temperature Board temperature TVS will clamp at 36V Software protection Hardware lead shorting circuit Hardware measurement CPU bridge temperature reading Clutch Variable voltage 8 bits PWM 400mA Strain gauge amplifier Dual stage 500 lt G lt 10000 high CMRR IO connector Molex PicoClasp 40 positions SMD 1mm pitch IOs available 12 External Digital lOs Upto 12 p
164. veloped in time to be documented in this thesis All the other evaluation criteria specifications were met or surpassed 133 8 Conclusion Over the last 20 months the idea of developing a new embedded system tailored to the specific needs of researchers in the fields of wearable robots such as advanced prostheses and exoskeletons evolved from a napkin sketch to a fully functional kit of electronics boards and software Past design attempts were analyzed key actors were questioned and technology was surveyed with one goal unifying all the requirements in one simple to use yet powerful system To outlive this thesis the FlexSEA system needed to be adaptable to a wide variety of project and scalable both in terms of the number of modules sensors and actuators and in terms of modularity and ease of accommodation of future technologies and changing needs It is believed that the design was brought to a sufficient level of completion to be used as a tool as a product and not just as a prototype FlexSEA is integrated in two current research projects and will soon be integrated in two other devices Only the future will tell if this redesign of the wheel will fasten the development of revolutionary prosthetic limbs but the preliminary results show great promises 134 1 2 3 4 5 6 7 8 9 10 References F Sup H Atakan Varol J Mitchell T J Withrow M Goldfarb Preliminary Evaluations
165. xperiment a series of trapezoidal trajectories with short plateaus 95 Position versus time 500 1000 Position ticks 1500 2000 2500 3000 1 1 l 8 10 12 14 16 18 Time s 1 0 2 4 6 4 3 FlexSEA Manage Figure 73 Knee position over time As stated before FlexSEA Manage is a polyvalent circuit that can have a wide range of usages depending on the system architecture In the simplest system designs such as in Figure 3 it will act as a communication protocol translator SPI lt gt RS 485 between Plan and Execute While most embedded computers have a serial port that could be used for RS 485 with a driver most do not boast speeds above 230kBaud s Using Manage in that fashion is perfectly valid for simple experimentations but it is not the most efficient strategy because in that scenario all the timings are dependent on Plan embedded computer that are not running a Real Time OS might not have deterministic timings When multiple slaves are present Manage can be used to route packets in the network Manage can be programmed to Auto sample its slaves In that case it will communicate with all its slave at precise intervals and store their data in its memory The communication with Plan can be asynchronous Manage can also be used to add sensors to the system In systems that do not require the computing power of an embedded computer Manage can host the high level state machines
166. xsea_1_0 manage Release flexsea ubuntu cd Desktop FlexSEA biomech ee svn Code flexsea_1_0 manage Release flexsea ubuntu Desktop FlexSEA biomech ee svn Code flexsea_1_0 manage Release openocd s Desktop FlexS EA embedded arm openocd bin share openocd scripts interface stlink v2 cfg target stm32f4x_stlink cfg c init c reset halt c sleep 100 c wait_halt 2 c flash write_image erase manage elf c sleep 100 c verify_image manage elf c sleep 100 c reset run c shutdown Open On Chip Debugger 0 8 0 2015 03 09 14 36 Licensed under GNU GPL v2 For bug reports read http openocd sourceforge net doc doxygen bugs html This adapter doesn t support configurable speed STLINK v2 JTAG v17 API v2 SWIM v4 VID 0x0483 PID 0x3748 using stlink api v2 Target voltage 3 247431 stm32f4x cpu hardware has 6 breakpoints 4 watchpoints target state halted target halted due to debug request current mode Thread xPSR 0x01000000 pc 0x08000268 msp 0x20030000 auto erase enabled Info device id 0x10076419 Info flash size 2048kbytes wrote 32768 bytes from file manage elf in 1 869838s 17 114 KiB s target state halted target halted due to breakpoint current mode Thread xPSR 0x61000000 pc 0x2000002e msp 0x20030000 verified 24152 bytes in 0 500174s 47 155 KiB s shutdown command invoked flexsea ubuntu Desktop FlexSEA biomech ee svn Code flexsea_1_0 manage Release Your chip is programmed The
167. y IMU Power output 128Mbits 6 axis 3x accelerometer 3x gyroscope 2 24V 1 high side switches features LEDs 2x green 1x RGB Switches 1x user input switch IO connector Molex PicoClasp 40 positions SMD 1mm pitch IOs available 17 shared with functions below External Digital IOs Up to 9 protected peripherals Analog inputs 8x 12 bit SAR with special functions filters amplifiers dividers Serial 12 SPI USART 40 Dimensions mm Y mm 40 62 Z mm 11 5 Layers 4 Copper 10z PCB technology Trace space via 5 5 mils trace space 8 20 mils vias Technology Standard Assembly Double sided 3 2 1 Microcontroller In systems with an embedded computer Manage is used as communication translator between SPI and RS 485 as a router and as a sensor processing unit When an embedded computer isn t used Manage will host the high level state machines All these applications require fast communication peripherals a minimum of 1 SPI and 2 UARTs and fast processing To support all the sub circuits present on Manage we need a microcontroller with e Aminimum of 3 SPI ports 1 for Plan 1 for the FLASH 1 for the Expansion connector e Aminimum of 3 UARTs 2 for RS 485 1 for the Expansion connector e Aminimum of 2 2 ports 1 internal 1 for the Expansion connector e Aminimum of 8 12 bits analog inputs e Aminimum of 20 digital 1 5 e USB While using a microcontroller f

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