AnsweredAssumed Answered

not stable at slow speeds PMSM FOC

Question asked by Machfax on Oct 30, 2014
Latest reply on Jan 7, 2015 by Gigi
Hi
I'm working with the motor from maxon:
http://www.maxonmotor.ch/maxon/view/product/motor/ecmotor/ecmax/ecmax30/272768
When I drive the motor at slow speed (50rpm), the Speed is not stable because the resolution of the speed feedback is just +-6rpm. I have an encoder with 2 lines and 500Counts per rotation. I work with the STM32 MC PMSM SDK v3.4.

Other strange thing is that I need to set in the ST Motor control workbench pole pairs 2 and Encoder pulses per mechanical revolution to 1000. I my opinion it should be pole pairs = 1 and pulses = 500. But with this setting the motor doesn't runs and make a lot of noise. With the "wrong" setting the motor is running but not stable and also the rpm readed back from the firmware with the command
ulMeasuredSpeed = UI_GetReg(oUI, MC_PROTOCOL_REG_SPEED_MEAS);
is not correct, its about 2 times too slow, why this?

Why it's not possible to set the speeds in a higher resolution than 6rpm? And how can I change this?

I need urgently help otherwise the project will be killed.

Best Regards

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