`Iq_setpoint` much higher than `Iq_measured` when above certain speeds (integral windup)

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1

Hello everyone –

I’m using ODrive to run a small scale dyno and evaluate motors for a robotics application. I’m running into an issue where Iq_setpoint ramps up to the current limit and Iq_measured does not follow. I’ve attached a plot showing what I mean.

current_ramp

This issue is occurring under velocity control mode with a setpoint of ~14.5Hz and above. The ramp is faster at higher setpoints and faster with higher values of vel_integrator_gain – looks like the integrator in the velocity controller is just winding up.

I have a feeling this is just a simple issue with some parameter or limit I’m not setting, but not sure what it is. Any ideas? Appreciate the help!

2

Sounds like you’re hitting the limit of your bus voltage to me.

3

Thanks for the reply. My supply was set to 15V. My motor is 100 KV, so 14.5 Hz = 870 RPM = 8.7V of back EMF. I understand I probably can’t use 100% of my bus but <60% seems low. Am I missing something in the math there?

4

I think the limit is 70 or 80%

5

Ok I see. Also I neglected to consider the Ohm’s law voltage drop due to the phase resistance, which is quite high for the motor I am using, so 60% all considered makes sense. One of my bearings was shot so running current was higher than normal as well.