Trouble with Sensorless: low speed, high current

Support
1

I just got my odrive and am having some trouble setting up sensorless control.

Here’s the code:

odrv0.axis0.controller.config.vel_gain = 0.01
odrv0.axis0.controller.config.vel_integrator_gain = 0.05
odrv0.axis0.controller.config.control_mode = CTRL_MODE_VELOCITY_CONTROL 
odrv0.axis0.controller.vel_setpoint = 400
odrv0.axis0.motor.config.direction = 1
odrv0.axis0.sensorless_estimator.config.pm_flux_linkage = 5.51328895422 / (7 *324)

odrv0.axis0.motor.config.current_lim=1
odrv0.axis0.controller.config.vel_limit=2000

odrv0.axis0.motor.config.calibration_current=1

odrv0.axis0.requested_state = AXIS_STATE_MOTOR_CALIBRATION

odrv0.axis0.controller.vel_setpoint = 1000
odrv0.axis0.requested_state = AXIS_STATE_SENSORLESS_CONTROL

The odrive beeps after the calibration. When I change the state in the last line, the motor turns very slowly (maybe 1 revolution in 5 seconds) and pulls 10 A (odrv0.axis0.motor.current_control.Iq_measured). This ignores the 1 A current limit and starts to heat the motor.

The same happens if I set vel_setpoint=0.

This is a 3536 size brushless motor. It came packaged with a hydraulic pump with no model number, so the Kv is measured 3.455 V peak-peak at 531.4 rev/min with 7 poles.

Any ideas what I’m doing wrong?

2

Just getting started. Any tips on your fix?

3

No. I ended up having to use an encoder.

4

Thanks. I’ll order a few now.

5

I see nobody responded the first time - sensorless control cannot work at low speeds, as it uses the measured back-EMF from the motor to do the control. You can use either an encoder or hall-effect sensors to do low-speed control (although the encoder is superior).

The sensorless mode is supposed to do a spin-up to a minimum rpm first, then work in velocity control from there.

6

Thank you for the info! I understand the minimum speed requirements; however, the board and motor just get really hot! I was able to get it working but while testing I think I may have burned up the board. All defaults amps were used and I normally use 40AMP ESC with these motors.