Low speed FOC control X nucleo-ihM07m1

[imtiaz]

Posted on April 21, 2016 at 01:25

Hi ,

Just a bit of background. We do motion control products and require smooth low speed to high speed motion. We also need high torque and all this lends itself to BLDC and PMSM motors. From the research Ive done it seems that FOC control may be the best bet. However after getting the dev board mentioned above with the nucleo -F302r8 and teh bull running 7 pole motor and the ST MC workbench - the low speed control is really  quite useless - the motor stalls below 1500 RPM - even with simple trapezoidal control I can easily go down to 500 RPM with most high speed motors. I have tried tuning the PID loop from default values - I get some improvement on low speed oscillations but it still stalls at quite  high speeds. I will try other motors in the meantime can anyone shed some light on how to get really smooth and really slow motor movement without using a stepper and their practical experience with St's FOC librarty and low speed control which is supposed to be the main advantage of FOC. Thanks a lot , Imtiaz #foc

[Gigi]

Posted on April 21, 2016 at 08:37

Ciao Imtiaz

Is better to clarify that the low speed control or the high speed range control that you mention are one of the advantage of the FOC, but you have to consider the speed sensor used. The main sensorless algorithm that you can find are based on BEMF estimation and the BEMF depends on the speed, so you can imagine that at low speed any sensorless algorithm fails. So I agree with you that FOC shall be able to run the motor with maximum efficiency from very low speed to very high speed, but to achieve this you have to use a physical speed sensor like incremental encoder (this is supported by the MC FOC lib.) The bull running sample motor that you find with the kit didn't have such kind of sensor. So I suggest you to focus on a sensored control. Ciao Gigi

[imtiaz]

Posted on April 21, 2016 at 20:58

Hi Gigi,

So can I fit a an external quadrature encoder on to the bull running motor and wire it to the correct pins on the nucleo and then configure the MC workbench to control FOC with the quadrature ? Or do I have to get a motor with built in hall effect sensors?ThanksImtiaz

[Gigi]

Posted on April 22, 2016 at 09:33 Ciao Imtiaz I suggest to not use the HALL sensors for very low speed application because this kind of sensor is not good for this purpose. Better to glue an encoder on the bull running. Ciao Gigi

[David Martins]

Posted on March 15, 2017 at 20:47

Did you get the motor running at low speeds?

I'm using an incremental encoder and I can not get low speeds with the motor.

How did you do it?

[llantalan .]

Posted on February 21, 2018 at 23:46

Thanks Gigi, is there an encoder you would recommend?

[Laurent Ca...]

The question has been moved from the "Motor Control Hardware" section to the "STM32 Motor Control" section (the question is about the STM32 MC SDK). 

Best regards