Motor Profiler Error

[JandreFrey]

Hi everyone. Following my Previous post, I have acquired a F446 Nucleo supporting 3shunt topology with the IHM17M1, such that I can perform motor profiling. However, I have run into an issue with the profiler getting stuck at 28%. Details are given below. Any help would be appreciated.

[PN]: X-Nucleo IHM17M1, Faulhaber 0620-006B
[VERSION]: 6.4.1
[TOOL]: MC PROFILER
[DETAILS]: Motor Profiler is stuck at 28%. The motor spins up in open loop mode. I have tried multiple speeds and currents within the motor range, and they all seem to work relatively well. However, when using the motor profiler, the motor does successfully spin up (enough current, I assume), but then stops before it reaches the target speeds, and then keeps retrying at a lower and lower acceleration. I have also tried a wide range of speeds from 5000RPM to 50000RPM, and all currents from 0.1-0.3A. I suspect it is not a startup error, but rather a sensing error. Given the size of the motor, and the operating current, I have considered increasing the Shunt resistors to 0.5Ohm, as I suspect the current sense gain is too low. However, I want to confirm this before going forward. (0.2A with 0.1Ohm shunt standard).
[HOW TO REPRODUCE]: See attached STWB6.

[JandreFrey]

Update:
I've increased the shunt resistors to 1.2 Ohm, which is definitely on the large side, but the voltage should still be within limits. See attached the opamp output waveform. The sinusoidal waveform can surely now be observed, but unfortunately this did not solve the problem. I've also opted to opening the standard motor pilot window and playing around with the startup parameters and gain tuning, with no luck.

[GMA]

Hello @JandreFrey,

This motor manufacturer provides the complete mechanical and electrical characteristics of its motors.
Your stwb6 project file already includes a Faulhaber 0620 description. If this description matches the motor data sheet, you do not need to run the motor profiler.

[JandreFrey]

Hi GMA, 

I created the 0620 motor description manually based on the motor datasheet. I opted to perform motor profiling since I could not get the motor operating in closed-loop sensorless mode. The motor spins up successfully in open loop mode, but fails when transitioning to closed loop sensorless mode (no matter if the switching speed is low or high). Please see my previous post for details.

As an alternative, I have tried running the motor using the hall sensor for feedback, but experienced issues regarding startup behaviour. The solution was to perform hall sensor profiling, which requires one to complete the motor profiling step first (as far as I could tell). 

[JandreFrey]

I've recently been able to get the motor running in 6step closed loop mode, but unfortunately still not in FOC. 

I was able to get the motor profiler to enter closed loop mode (I think) by using an extremely small starting current (0.05A). But unfortunately, it still does not pass 28%, and the behaviour is not reproducible with the normal startup using motor pilot.

[JandreFrey]

After some further evaluation, I have noticed the L/R (thus the time constant) ratio for this motor is 28e-6/8.8 = 3.2e-6.

To my understanding, a time constant 3.2us results in a current loop update rate of at least 600-800kHz, which is not feasible.

If this is correct, please let me know, or alternatively, how I have it wrong.

Kind regards,

J

[GMA]

Hello @JandreFrey,

Assuming the time constant of the motor, you can try to increase the PWM frequency of the project and decrease the Cut-off frequency of the Current regulator in the Workbench Drive setting tab.