AnkleHardwareSpec2007Sep

State Machine (Master) Controller

• 25.32V max supply voltage

Off board interfaces

Switch Input

• external logic switch input for mode control

External Serial Communication and ISP

• Ability to support a variety of attached serial devices: wired RS-232, Bluetooth, 802.11, and ISP.
• 1Mbaud (max) RS-232 level ASYNC serial with power (Tx, Rx, RTS, CTS)
• Power for external devices: 5V and Vbat (with 0.25amp self resettable fuse)
• ISP signals (PGC, PGD, MCLR) - allows external programming
• signals: Vbat, Vcc5, GND, Tx, Rx, RTS, CTS, PGC, PGD, MCLR

power / data to Motor Controller

• logic level ASYNC 2-wire serial between master and motor controller CPUs
• logic level output to motor controller fault pin to disable PWM
• logic level input for motor controller alert status
• battery power from motor controller
• low current path to battery for voltage monitoring
•  ??? board to board stacking connector (more reliable that wires)

Ankle Angle ???

• quadrature encoder (5V single ended) [GND, 5V, ChA, ChB, NDX to dsPIC QEI inputs]
• or magnetic rotary encoder (such as AS5045 family) [GND, 3.3V, PWM to dsPIC IC timer]

Strain, SEA, Motor Temp, Supply current

• 4 analog inputs to CPU, DC to 500 Hz analog bandwidth
• 1 x 10k thermo resistor (requires opamp follower), AGND and signal
• 2 x strain gauge bridges (high gain INA326), AGND, SG+, SG-, bridge reference
• SG bridge reference voltage through 0.1% resistance from AVCC5
• 1 x analog input for SEA hall sensor board (no voltage or current amp required) : 3.3V, AGND, signal

On board sensors

Ambient Temperature

• Thermo resistor with opamp follower placed very close to XY axis IMU

Supply Voltage Monitor

• (better than) 1% accurate measurement of battery voltage (prevent over-voltage during regen)

IMU

• One SPI device, and (upto) 3 analog rate gyro signals

• 3axis (SPI) accelerometer LIS3LV02DQ
• Z axis rate gyro ADXRS300 (analog) or ADIS16100 (digital)
• XY axis (analog) rate gyro IDG300
• Note: XY is in circuit board plane, Z axis is normal to circuit board plane

software

• ability to reprogram SM Controller over ASYNC serial
• 2 DMA controllers run the two ADC units at 12 bits, 400 KHz total sample rate
• Input capture measures PWM period of magnetic rotary encoder / QEI captures encoder position
• DMA controller sends/receives SPI to digital accelerometer
• Main code loop runs at 500 Hz
  • decimation of analog inputs
  • reads ankle position
  • reads IMU, estimates orientation
  • reads motor controller status (motor current, motor position, status)
  • processes external communication interface

Motor Controller

• support for Maxon EC30-48V [305015] with 500 CNT MR ENCODER [225778]
  • EC30-48V specs : L=65.3uH, R=386mohm, SpeedConst=346 rpm/volt, TorqueConst=27.6mNm/A
  • Required maximum RPM : 7500

• 25.38V abs max supply voltage
• suggested design using 30V MOSFETs, 35V bulk caps, and 35V DC-DC converter
• 2 phase current sensors (ACS712-20amp, 1.2mohm)
• Ability to (permanently) short motor leads when primary power absent or if some sort of system failure

Off board interfaces

Motor position sensor

• 5V quadrature with index (single ended)
• hall effect sensor

power / data to master controller

• ASYNC serial to UART
• TTL input to dsPIC fault pin to disable PWM
• TTL output for status
• "direct" connection to Bat+

On board sensors

• 2 current sensors

software

• master will periodically send ASCII commands to command current and mode
• controller will respond with status (encoder position, supply voltage, actual current, temperatures)

io count

AD

• 2 for motor current
• 1 for 5V supply monitor

• 1 for battery current
• 1 for supply voltage
• 1 or 2 for temperature
• 1 for 5V supply monitor

digital (21 max)

• 6 PWM output
• 2 fault IOs
• 2 ASYNC serial
• 3 for ISP
• 3 for encoder
• 3 for motor hall position sensor
• 2 for LEDs

Mechanical

• dimensions