Motor

Motor Controller

• primary 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 (6 cell LiPoly)
• 50KHz to 100 KHz PWM
• suggest 30V MOSFETs, 35V bulk ceramic caps, and 35V input DC-DC converter
• Ability to (indefinably) short motor leads when primary power absent or if some sort of system failure
• suggest dsPIC33FJ64MC506 for production, dsPIC33FJ128MC706 used in prototype
• Single PCB for controller?
• IIC EEPROM for controller parameters
• Ultra short and wide high current paths.
• Design for peak motor currents of 25 amps (0.1mS, less than 10% duty)
• Continuous motor currents of 5 amps

Off board interfaces

POWER SUPPLY INPUT

• Wires (2x16 AWG, 1x22AWG) to enclose connector solder directly to holes adjacent to bulk bypass caps
• 3rd wire used to implement electronic delayed electronic (soft start) switch

MOTOR POWER OUTPUT

• Motor wires (3x18AWG) solder directly to holes adjacent to current sensor / MOSFET outputs

Motor position sensors

• 5V quadrature with index (single ended or differential ???)
  • MR encoders are differential and come with 10 pin ribbon cable and 2x5x0.1" header.
• 5V hall effect sensor (may require 10k pull up to 5V)

power / data to Motor Controller

• logic level ASYNC 2-wire serial between master and motor controller CPUs
• logic level in to /FLTB (to disable PWM)
• logic level output to indicate alert status
• battery power to motor controller
• sense path to battery for voltage monitoring
• board to board stacking connector (more reliable that wires)

On board sensors

• NOTE: Motor temp and battery voltage sensor moved to SM
• Battery current sensor kept local to facilitate electronic fuse.
• Is an electronic (battery) fuse necessary?

Motor Current

• Two motor current sensors (ACS712-20) (+-25amps peak)
•  ??? First order LP filter at >= 20 KHz

Battery current monitor

• either ACS712-30 or external loop (offboard)
• battery current monitor needed on this board if a hardware fuse circuit is to be implemented. However, this circuit could be implemented in software on either board.

AVCC5 monitor

• Measure AVCC5/2
• current sensors are ratiometric - offsets depend on AVCC5

Low Power Support

• Design for overall low power
• Target for sleep power of 5W (0.12WHr/day - from VBAT), (processor is sleeping @ 200uA)
• Control of supply to internal sensors : ACS712, battery monitor
• Control of supply to external sensors : motor encoder, motor hall sensors
• Control of supply to mosfet drivers.

software

• ability to reprogram controller over ASYNC serial
• low power mode (5mW) where controller responds to ASYNC serial
  • PWM off
  • hall sensors periodically powered and monitored
  • encoder power off,
• standby (<<5mW) by where processor sleeps, wakes on serial RX
  • all sensors and outputs are off
  • motor leads are shorted

• SM controller will periodically send ASCII commands to command current and mode
  • controller PID will implement commanded current
  • controller will respond with status (encoder position, actual current)
  • absence of valid communication with SM (after 5mS):
    • set desired current to zero (and after 100mS)
    • enable motor lead short sub-circuit