STM32F301: Speed feedback error at high temperature

[L. G.]

Posted on September 04, 2017 at 12:27

Dear Sirs,

I have same problems to drive one SM-PMSM at ambient temperature of 65°C.

At 25°C there is not any problem, all works as expected, but at 65°C a speed feedback error appear.

I checked the current sensing circuit, but all the electrical  signals on the OPAMP, power supply are ok.

The ambient temperature close to the micro-controller (rated T85) is around 70°C.No any improvement if I change the motor BEMF parameter to compensate the BEMF changes due to the increased temperature.

Here below my settings:

- STM32F301C8T6;- ST FOC library 4.2;- sensor-less (Observer+PLL);- one shunt and external OPAMP for the current sensing;- Torque control;- ambient temperature 65°C.

Do you have some hints to find the cause of the problem?

Thank you in advance for the help

[Tomas DRESLER]

Posted on September 04, 2017 at 18:56

Dear L.G.,

speed feedback typically is caused by ripple in the speed estimation, in turn caused by worse current readings/response or misalignment of the motor model or speed PLL.

The easy: Try reducing G2 by factor two until the problem disappears. The same way you're however reducing probability of detecting stall.

The more difficult: look at DACs and compare what signals start deteriorating across the temperature. Good digital oscilloscope would help. Then, see which of the regulators may help tweaking.

[L. G.]

Posted on September 08, 2017 at 19:22

Dear Edison,

the problem seems solved increasing the ADC clocks only.

But in this way the ripple of the estimated B-emf is increased a lot so I must increase the G2 in any case.

Thanks a lot, have a good day