Loss of control whenever the motor starts at some specific points

[RBrec.1]

Hi, I am currently developing position control using MCSDK and have stumbled upon a problem I cannot fix. Whenever the motor is positioned at some specific points it is not possible to start it up without it spinning out of control. I'm using a

• BLDC with 10 pole pairs
• Encoder, 2048 with index
• I have 3 commutation signals (H120) available but not used
• Nucleo G431RB
• IHM08M1 3shunt motor driver

What I have found is that whenever Com U = low, Com V = high and Com W = low the motor starts to spin very fast in one direction, and do not stop. Meaning if I restart the program while the motor have these signals, it is inevitable. Often the motor stand still for a second (no movement at all) before going berserk.. At some of these points it can recover and move away before losing control if there is no load, but seems to fail if I give it even a little resistance.

Has anyone encountered a similar problem?

[cedric H]

@Quentin Ch​ @RBrec.1​ , Could you please attach in a zip file your stmcx project file.

If your motors are available for purchase, it would be also interesting if you can give us the reference. We will try to reproduce your issue to understand what could be the issue.

Thanks a lot.

Cedric

[Quentin Ch]

Thanks a lot for your insight.

I sent you a message with the .stmx file and additional info about the generation settings and the motor specs and reference (Gefeg Neckart MQ667 motor)

Please let me know if additional info are required and about your findings.

[Quentin Ch]

Hello, did you managed to solve your issue ?

I'm now focus on this point, but I think my issue is a little different (the first call to StartMotor() makes it spin at max speed in the wrong direction, because estimated Iq current seems to sometimes have the wrong sign).

Not exactly the same symptoms as you (I use 1024 PPR encoder, not Halls) but may be related.

[Quentin Ch]

@RBrec.1​ 

Hey, I finnaly understood the loss of control at specifi points in my case, it may help yours:

it occurs when the rotor's field is 180° from the A phase field along which the MCSK tries to align the rotor, leading to nearly no torque and so no motion during alignement, and a 180° position error/sign inversion.

(https://community.st.com/s/question/0D53W00001pvJaISAU/motor-sometimes-starts-in-wrong-direction-because-of-wrong-sign-of-iq-measured)