Motor_error_unknown_torque

[sam99]

Hello,

I would like help figuring out why odrive is failing is a very specific scenario. I am using odrive (v3.6-56V) operating at 36V (i am using a battery).

MOTOR: Electric Skateboard Brushless Motor 6374 190KV | Longboard | Flipsky – FLIPSKY
ENCODER: 8192 CPR Encoder with ODrive Cable — ODrive

Limits:

• odrv0.axis0.motor.config.torque_lim = 1.5
• odrv0.axis0.motor.config.current_control_bandwidth = 2000
• odrv0.axis0.controller.config.vel_limit = 50
• odrv0.axis0.controller.config.input_mode = INPUT_MODE_PASSTHROUGH
• odrv0.axis0.controller.config.control_mode = CONTROL_MODE_POSITION_CONTROL

The error is happens only in a very specific scenario. When i command odrive the following commands in the following order in very short time span.

odrv0.axis0.controller.input_pos = -150
odrv0.axis0.controller.input_pos = 0
odrv0.axis0.controller.input_pos = -150
odrv0.axis0.controller.input_pos = 0

I would like to note that:

• This error never happens if I reduced the torque limit from 1.5 to 1.3N.m
• This error never happens if I waited for the motor to reach position -150 before commanding position 0, and waiting for the motor to reach position 0 before commanding it to go to position -150, etc …
• I did try to reduce the noise on the encoder index signal by shielding the encoder cable and adding a 47nF cap between the encoder index signal and GND.
• i did reduce the length of the encoder cable as much as possible and i am running it away from the motor phase cables.

I would love any suggestions of what i can try next Thank you

[zbiggs5]

I found the first response on this thread helpful for solving this issue:

Multiple errors when during trap moves with high accelerations

Hi, I have an Odrive 3.6 and a D6374 motor. I have these connected to a test rig with a 1m linear axis and a 2kg mass. I’m powering the odrive with a 48V, 50A power supply. When I try more aggressive accelerations (e.g. >400 rev/s^2) the axis will often accelerate then coast to a stop, and if I do a dump_errors() I see: system: no error axis0 axis: no error motor: Error(s): MOTOR_ERROR_UNKNOWN_TORQUE MOTOR_ERROR_UNKNOWN_VOLTAGE_COMMAND sensorless_estimator: no error encoder: …

Increasing motor.config.current_control_bandwidth to 2000 seems to have worked for me so far!

[sam99]

Thank you for your reply

The error happened when the current controller bandwidth is set to 2000!

Should I try increasing it to more than 2000? What is the recommended upper limit for the current controller bandwidth?

[zbiggs5]

Sorry! I didn’t see that you had already done that.

I don’t know about increasing it more, but you could also try changing axis.controller.config.input_mode = INPUT_MODE_TRAP_TRAJ and setting values for
<odrv>.<axis>.trap_traj.config.vel_limit = <Float> <odrv>.<axis>.trap_traj.config.accel_limit = <Float> <odrv>.<axis>.trap_traj.config.decel_limit = <Float>

So far, this mode has worked pretty well for me.

Here is a link to the documentation for trajectory control:

ODrive