EtherDrive Motor Controller

Written by Pascal Stang | Updated: Thursday July 28, 2005

Overview:

The EtherDrive Motor Controller is a multi-axis ethernet-based motor controller and driver system. It consists of controller and driver PCBs which connect together. A single controller may drive up to 6 motors (3 driver cards).

EtherDrive Controller

EtherDrive Driver (dual channel)

Hardware Features:

EtherDrive Controller V1.0
- 10/100Mb/s Ethernet and dual serial communication interface
- ATmega128 processor @ 18.432MHz
  - ISP, JTAG, or serial bootloader programming
  - JTAG debugging
  - Optional external 512KB RAM
- 6-axis motor control
  - 6 Quadrature encoder counters with optional index pulse detect
    (counters can operate in 4-edges or 2-edges per encoder count)
  - 6 Programmable motor control PWM outputs (sign-magnitude or locked-antiphase mode)
  - 6 Feedback A/D inputs (for motor current/voltage sensing, or external sensors)
- Emergency stop connector (4-pin molex connector, 2 pins control, power, gnd)
- 8-channel 12-bit A/D for motor feedback/sensing
- 8-channel 10-bit A/D general-purpose inputs (from ATmega128)
- CPLD JTAG connector for reprogramming
- Power input via DC jack or from driver boards.
- 4 Status LEDs
- Power LED.
- 3.0" x 5.0" size (0.70" total height, approx.)
EtherDrive Driver V1.0
- Dual-channel motor driver (drives 2 DC motors).
- Output specs:
- Input Specs:
  - 3 digital control signals per motor.
  - May be configured for sign-magnitude or locked-antiphase (four-quadrant) drive.
  - PWM frequencies up to 250KHz
  - Inputs are 3.3V and 5V compatible.
- Indicators:
  - Bi-color motor drive indicator LEDs.
  - Power indicator LED.
- Amplified analog current-sensing outputs.
- On-board 12V regulator for drive electronics.
- Optional auto-shutdown when controller is turned off.
- 3.0" x 5.0" size (0.75" total height, mosfets mounted w/o heatsink)

Software/Firmware Features and Operation:

The EtherDrive Motor Controller standard firmware supports two modes of operation:
- Local Control Loop operation
  - Control loops calculated and executed locally by the on-board microcontroller.
  - Typical closed-loop rates are 1-5KHz depending on complexity of control algorithm.
  - Standard operation consists of PID control of motor position, and optionally, motor current.
  - Motor commanding (control loop set points) are sent via ethernet UDP/IP or serial port.
  - Controller configuration and loop gains set via ethernet or serial port.
- Remote Control Loop operation
  - Control loops calculated remotely by off-board computer.
  - Closed-loop rates of up to 4KHz (3.25KHz typical, network limited)
  - Control loop procedure:
    - EtherDrive sends encoder and current feedback values to 'remote' control computer via ethernet UDP/IP packet
    - Remote computer computes desired control law
    - Remote computer sends motor PWM drive values to EtherDrive
    - Repeat.
  - Controller configuration set via ethernet or serial port.
Example client software is available to demonstrate operating the controller in each mode.
Custom operating modes can be designed to meet the needs of specific users or projects as needed.

Network Protocol Information:

Information as of 9/1/2005.

Network Addressing and Support Details		Notes
Supported protocols	UDP, ICMP (ping), IP, ARP	Unit will respond to pings to IP address. No TCP support at this time. ARP table currently limited to 8 entries.
IP Address (default)	192.168.1.12	User-changable via serial port interactive terminal. User set value is volatile (cleared at power-off). Will be upgraded to non-volatile.
Netmask (fixed)	255.255.255.0	Will be upgraded to user-changable, and non-volatile.
Gateway (fixed)	192.168.1.1	Will be upgraded to user-changable, and non-volatile.
Network Active Port Details		Notes
Echo	7/UDP	UDP Echo port. Packets sent to this port will be echoed to sender, payload unmodified.
Motor Control port	4900/UDP	Motor drive and feedback values passed via UDP packets on this port. See protocol info below.
EtherDrive Command port	4950/UDP	Configuration and instruction packets should be sent to this port. See protocol info below.

Motor Drive Command Format (send to Motor Control port)				Notes
Description	Byte Offset	Byte Length	Data Type	This packet is sent by the controlling host
Motor 1 Drive	0	4	signed int32	Drive command of zero indicates no net power to motor. Valid range of drive command depends upon PWM period and PWM mode: In Locked-Antiphase mode, range is +/-(PWM period/2) In Sign-Magnitude mode, range is +/-PWM period Drive levels in excess of the linear range will be clamped at the extreme.
Motor 2 Drive	4	4	signed int32
Motor 3 Drive	8	4	signed int32
Motor 4 Drive	12	4	signed int32
Motor 5 Drive	16	4	signed int32
Motor 6 Drive	20	4	signed int32
Motor Feedback Format (received from Motor Control port)				Notes
Description	Byte Offset	Byte Length	Data Type	This packet is sent back to the host in response to a Motor Drive Command
Encoder 1 Position	0	4	signed int32	Encoder position feedback is read and refreshed for each motor feedback packet sent. Value indicated number of tics counted since last reset. Value will overflow in standard 2's-complement form upon reaching +/-2^31.
Encoder 2 Position	4	4	signed int32
Encoder 3 Position	8	4	signed int32
Encoder 4 Position	12	4	signed int32
Encoder 5 Position	16	4	signed int32
Encoder 6 Position	20	4	signed int32
Motor 1 Current	24	4	signed int32	Motor current values represent the latest available values at time of packet transmission. Value range is +/-1024. Current readings may only be accurate in locked-antiphase mode. Value = ((ImotorRsense11)/1.25)*1024 where Imotor is in [AMPS] and Rsense is in [OHMS]
Motor 2 Current	28	4	signed int32
Motor 3 Current	32	4	signed int32
Motor 4 Current	36	4	signed int32
Motor 5 Current	40	4	signed int32
Motor 6 Current	44	4	signed int32

EtherDrive Command Format (send to ED Command port)				Notes
Description	Byte Offset	Byte Length	Data Type
Command	0	4	signed int32	An EtherDrive command can be issued to change the way the EtherDrive system is configured or operating. Processing of commands may interrupt closed-loop motor operation and should not be issued during critical motion control. It is recommended that motors be stopped before sending most commands.
Argument 0	4	4	signed int32
Argument 1	8	4	signed int32
Argument 2	12	4	signed int32
...	...
Argument N	4*N	4	signed int32

EtherDrive Commands (send to ED Command port)				Notes
Description	Cmd	Arg0	Arg1
Disable Motors	'e'			Disables motor drivers (motors drivers are open-circuit)
Enable Motors	'E'			Enables motor drivers
Locked-Antiphase PWM	'p'
Sign-Mangitude PWM	'P'
PWM period	't'	period [tics]		Period is specified in tics (1 tic = 40ns). Safe range is 220-511.
This command list subject to change (guaranteed that it will change)

Mechanical Drawings:

Coming soon...

Written by Pascal Stang | Updated: Thursday July 28, 2005