Motor spins uncontrollably

1

Hello,
I finished the calibration of the encoder and motor without any error messages at the moment. I try then velocity control with 3000 counts/s. The motor starts spinning but very fast and the encoder measures a velocity of ca. -220000 counts/s. I am using T-Motor U13 KV85 and an incremental encoder with 8192 cpr. My settings are below:

motor.is_calibrated = True
motor.current_control.p_gain=0.035
motor.current_control.i_gain=46.91
motor.config.pre_calibrated=True
motor.config.pole_pairs=12
motor.config.calibration_current=10.0
motor.config.resistance_calib_max_voltage=2.0
motor.config.direction=-1
motor.config.current_lim = 30
encoder.index_found=True
encoder.config.mode=0
encoder.config.use_index=True
encoder.config.pre_calibrated=True
encoder.config.cpr=8192
encoder.config.offset=-8362
encoder.config.offset_float=0.32
encoder.config.bandwith=1000
encoder.config.calib_range=0.1
controller.config.control_mode=2
controller.config.pos_gain=20
controller.config.vel_gain=0.005
controller.config.vel_integrator_gain=0

Does anyone have a solution or has experienced the same problem? I have the feeling, that my encoder offset is quite high.

2

Yeah that offset doesn’t look right. Offset issues can happen due to electronic noise. How are you connecting your encoder?

3

It is connected via ABI. I solved this problem as I redid the encoder offset calibration. My motor has a quite high cogging torque so I set the calibration current up to 20 A. After this the calibration of the encoder offset was running a lot smoother.

Now I have another problem with the encoder offset on my second motor on axis1.
How do I know whether a encoder offset is quite alright or quite high? For the second motor I use an encoder with 16384 cpr and get an offset of -4992.

If I try to go into closed loop control and start the velocity control the motor starts spinning with 3000 c/s and then stops as it has the error: current unstable. I tried to set the current_limit up to 13 A but still Iq_measured gets higher than 16 A. I do not want to rise it any further as the motor I am using is limited to 15 A. I want to use the set up in velocity control. I have the feeling that my gains are quite high. I do not have tuned them yet though as I am still not finished with calibration.

Current Control:
p_gain=0.106
i_gain=277.59
Velocity Control:
vel_gain=0.0005
vel_integrator_gain=0.001

4

There’s something wrong with the calibration or encoder. If your cogging torque is that high, I’m not actually entirely sure how to calibrate that reliably. Perhaps @Tobin_Hall can help? I know he was dealing with high cogging torque motors at one point.

5

The cogging torque of the motor on axis1 is not that high. I am not using the same motor on axis 1 and 0. On axis 1 I use this T-Motor. Is the encoder offset of -4992 indicating that the encoder slipped or is not placed correctly?

Edit: it seems as there is something wrong with the encoder as it also now finds multiple indexes as was mentioned in this post.