Looking for some advice for some specific performance improvement.
I am working on a traction application with custom inverter hardware and ST FOC software. Also using custom motors with built in hall sensors. The application uses the motors for movement and steering (eg. controlling two back wheels separately). Motors are set to run only in speed control.
Generally, I have no issues starting, running and emag braking ABOVE a certain minimum speed. However when the vehicle is stopped, I keep the controllers running at zero RPM to try and keep the wheels from moving in case of slight terrain incline/decline - kind of like a park brake. This does not work very well. The speed controller seems to hunt or oscillate and the wheels will either jitter back and forth or roll at a really slow speed. This gets worse with tighter PI coefficients that are good for running performance.
Just wondering if any one has any suggestions for improving things. I've thought of implementing my own hybrid torque/speed control algorithm below a speed threshold to help the start, stationary and final stopping states be a little smoother. Maybe even inject a little d-axis current when stationary to passively hold the wheels still instead of using reaction torque as is the case with the generic speed control.
Is there anything in the software I can tweak to get it to behave at this almost stopped and stopped state?
What is usually done in these scenarios in EV FOC applications?
