Difference between revisions of "Motor"

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Line 5: Line 5:
  
 
* 25.38V abs max supply voltage (6 cell LiPoly)
 
* 25.38V abs max supply voltage (6 cell LiPoly)
−
* support for 50KHz to 100 KHz PWM  
+
* 50KHz to 100 KHz PWM  
−
* suggested design using 30V MOSFETs, 35V bulk ceramic caps, and 35V input DC-DC converter
+
* 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
 
* 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
 
*suggest dsPIC33FJ64MC506 for production, dsPIC33FJ128MC706 used in prototype
−
* Might be possible to get controller on 1 PCB
+
* Single PCB for controller?
 
* IIC EEPROM for controller parameters
 
* IIC EEPROM for controller parameters
 
* Ultra short and wide high current paths.   
 
* 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==
 
==Off board interfaces==
−
===SUPPLY POWER===
+
===POWER SUPPLY INPUT===
 
* Wires (2x16 AWG, 1x22AWG) to enclose connector solder directly to holes adjacent to bulk bypass caps  
 
* 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
 
* 3rd wire used to implement electronic delayed electronic (soft start) switch
  
−
===MOTOR POWER===
+
===MOTOR POWER OUTPUT===
 
* Motor wires (3x18AWG) solder directly to holes adjacent to current sensor  / MOSFET outputs
 
* Motor wires (3x18AWG) solder directly to holes adjacent to current sensor  / MOSFET outputs
 
   
 
   
 
=== Motor position sensors===
 
=== Motor position sensors===
 
* 5V quadrature with index (single ended or differential ???)
 
* 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)
 
* 5V hall effect sensor (may require 10k pull up to 5V)
  
Line 36: Line 39:
 
* NOTE: Motor temp and battery voltage sensor moved to SM
 
* NOTE: Motor temp and battery voltage sensor moved to SM
 
* Battery current sensor kept local to facilitate electronic fuse.
 
* Battery current sensor kept local to facilitate electronic fuse.
 +
* Is an electronic (battery) fuse necessary?
  
 
===Motor Current===
 
===Motor Current===
Line 59: Line 63:
 
==software==
 
==software==
 
* ability to reprogram controller over ASYNC serial
 
* 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
 
* SM controller will periodically send ASCII commands to command current and mode
−
* controller will respond with status (encoder position, actual current)
+
** controller PID will implement commanded current
−
* absence of valid communication with SM:
+
** controller will respond with status (encoder position, actual current)
−
** set current to zero
+
** absence of valid communication with SM (after 5mS):
−
** implement virtual spring / damper
+
*** set desired current to zero (and after 100mS)
−
** enable motor lead short sub-circuit
+
*** enable motor lead short sub-circuit

Revision as of 12:13, 10 September 2007

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
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