Motor
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Contents
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 (RJK0303DPB), 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
- ISP Connector
- Single PCB for controller?
- IIC EEPROM for controller parameters
- Ultra short and wide high current paths.
- Design for peak motor currents of 25 amps (100mS, 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
- chassis GND wire (1x22) solder directly hole adjacent to BAT- input
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 open collector input (use 10K pull ups to 3.3V or 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 (eg ACS712-20) (+-25amps peak)
- ??? First order LP filter at >= 20 KHz
Battery current monitor
- suggest either onboard (ACS712-30) or external current sensor loop
- 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 required if current sensors are ratio metric
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.