This driver was developed at the Underactuated Lab in Robotics Innovation Center at DFKI GmbH, Bremen.
It assumes the use of a CAN to USB adapter (such as PEAK System's PCAN-USB or ESD's CAN-USB/2) connected to a linux (tested on Ubuntu) computer. The SocketCAN interface is used, thus allowing the use of Python Socket library.
Initial tests show communication (send-reply) frequencies of ~800Hz using PCAN-USB and ~1500Hz using ESD CAN-USB/2 with a single motor connected.
- bitstring
Install via:
pip3 install bitstring
- Useful videos:
- Motor Datasheets
- Ben Katz Documentation
-
Setting up the CAN interface:
-
Run this command and make sure that
can0(or any other can interface depending on the system)shows up as an interface after connecting the USB cable to your laptop:ip link show -
Configure the
can0interface to have a 1 Mbaud communication frequency:sudo ip link set can0 type can bitrate 1000000 -
To bring up the
can0interface, run:sudo ip link set up can0
-
-
To change motor parameters such as CAN ID or to calibrate the encoder, a serial connection is used. The serial terminal used on linux for this purpose is
screen. Example usage:
sudo apt-get install screen
screen /dev/ttyUSB0 921600
Import: from motor_driver.canmotorlib import CanMotorController if installed via pip. Otherwise, adjust import statement based on system's PYTHONPATH (e.g. when cloned from GitHub).
Example Motor Initialization: motor = CanMotorController(can_socket='can0', motor_id=0x01, motor_type='AK80_6_V2', socket_timeout=0.5)
Available Functions:
enable_motor()disable_motor()set_zero_position()send_deg_command(position_in_degrees, velocity_in_degrees, Kp, Kd, tau_ff):send_rad_command(position_in_radians, velocity_in_radians, Kp, Kd, tau_ff):change_motor_constants(P_MIN_NEW, P_MAX_NEW, V_MIN_NEW, V_MAX_NEW, KP_MIN_NEW, KP_MAX_NEW, KD_MIN_NEW, KD_MAX_NEW, T_MIN_NEW, T_MAX_NEW)
All motor communication functions return current position, velocity, torque in SI units except for send_deg_command. change_motor_constants does not return anything.
- AK80-6 (From Cubemars, Firmware versions V1, V1.1, and V2):
motor_type='AK80_6_V1',motor_type='AK80_6_V1p1'andmotor_type='AK80_6_V2' - AK80-9 (From Cubemars, Firmware version V1.1 and V2):
motor_type='AK80_9_V1p1'andmotor_type='AK80_9_V2' - AK70-10 (From Cubemars, Firmware version V1.1):
motor_type='AK70_10_V1p1' - AK10-9 (From Cubemars, Firmware version V1.1):
motor_type='AK10_9_V1p1'. TODO: The temperature and error codes are received but not yet decoded for the new firmware for this motor.
# Working parameters for AK80-6 V1.0 firmware
AK80_6_V1_PARAMS = {
"P_MIN" : -95.5,
"P_MAX" : 95.5,
"V_MIN" : -45.0,
"V_MAX" : 45.0,
"KP_MIN" : 0.0,
"KP_MAX" : 500,
"KD_MIN" : 0.0,
"KD_MAX" : 5.0,
"T_MIN" : -18.0,
"T_MAX" : 18.0,
"AXIS_DIRECTION" : -1
}
# Working parameters for AK80-6 V1.1 firmware
AK80_6_V1p1_PARAMS = {
"P_MIN" : -12.5,
"P_MAX" : 12.5,
"V_MIN" : -22.5,
"V_MAX" : 22.5,
"KP_MIN" : 0.0,
"KP_MAX" : 500,
"KD_MIN" : 0.0,
"KD_MAX" : 5.0,
"T_MIN" : -12.0,
"T_MAX" : 12.0,
"AXIS_DIRECTION" : -1
}
# Working parameters for AK80-6 V2.0 firmware
AK80_6_V2_PARAMS = {
"P_MIN" : -12.5,
"P_MAX" : 12.5,
"V_MIN" : -38.2,
"V_MAX" : 38.2,
"KP_MIN" : 0.0,
"KP_MAX" : 500.0,
"KD_MIN" : 0.0,
"KD_MAX" : 5.0,
"T_MIN" : -12.0,
"T_MAX" : 12.0,
"AXIS_DIRECTION" : 1
}
# Working parameters for AK80-9 V1.1 firmware
AK80_9_V1p1_PARAMS = {
"P_MIN" : -12.5,
"P_MAX" : 12.5,
"V_MIN" : -22.5,
"V_MAX" : 22.5,
"KP_MIN" : 0.0,
"KP_MAX" : 500,
"KD_MIN" : 0.0,
"KD_MAX" : 5.0,
"T_MIN" : -18.0,
"T_MAX" : 18.0,
"AXIS_DIRECTION" : 1
}
# Working parameters for AK80-9 V2.0 firmware
AK80_9_V2_PARAMS = {
"P_MIN" : -12.5,
"P_MAX" : 12.5,
"V_MIN" : -25.64,
"V_MAX" : 25.64,
"KP_MIN" : 0.0,
"KP_MAX" : 500.0,
"KD_MIN" : 0.0,
"KD_MAX" : 5.0,
"T_MIN" : -18.0,
"T_MAX" : 18.0,
"AXIS_DIRECTION" : 1
}
// Working parameters for AK70-10 V1.1 firmware
AK70_10_V1p1_params = {
"P_MIN" : -12.5,
"P_MAX" : 12.5,
"V_MIN" : -50,
"V_MAX" : 50,
"KP_MIN" : 0,
"KP_MAX" : 500,
"KD_MIN" : 0,
"KD_MAX" : 5,
"T_MIN" : -24.0,
"T_MAX" : 24.0,
"AXIS_DIRECTION" : 1
}
# Working parameters for AK10-9 V1.1 firmware
AK10_9_V1p1_PARAMS = {
"P_MIN" : -12.5,
"P_MAX" : 12.5,
"V_MIN" : -50.0,
"V_MAX" : 50.0,
"KP_MIN" : 0.0,
"KP_MAX" : 500,
"KD_MIN" : 0.0,
"KD_MAX" : 5.0,
"T_MIN" : -65.0,
"T_MAX" : 65.0,
"AXIS_DIRECTION" : -1
}
To add a new constants configuration use the change_motor_constants function or create an issue with the constants and motor information on the GitHub page to be added to the driver.
Issue Fixed: When having 2 motors on the CAN bus with either PCAN CAN-USB or ESD CAN-USB/2, sometimes the motors experience an initial short kick/impulse at when they are enabled again after being disabled. This was fixed.
As this is experimental software, there might be other unknown issues.