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BLDC FOC Hall offset

Other Parts Discussed in Thread: DRV8312

Hi to all,

i have a question:

I am working with the "Permanent Magnet Synchronous Motor Field-Oriented Control" example and there is one thing which i dont understand.

The Park Transformation and the Inverse needs the angle scaled from 0 to 1.
 So far so good.

The position calculation with halls is as followed.

Hall_offset (electrical offset) + offset ( depending on the hallvalue) + saturate[(countervalue/(2*speed)]

Looks quite confusing but i hope u know what i mean. The angle should be scaled from 0 to 1 for the Ti's Park and IPark.

The Hall_offset ist set to 0.57, which corresponds to 205,2°. The offset should be 0 -> 5/6 (0.83), which corresponds to 300°. The Last term is saturated to -1/6 to 1/6.

How should i get the full ranged angle? I have to say, it works. Not very well but it works. Ive got the DRV8312 Kit and the motor is spinning. But not higher than 1800RPM. I think it is because the position is not right calculated.
 Actually i have a position range from 0.57 -> 1.4.

Could someone explain to me where the offset from the Halls is coming from? I dont get it because it is a odd number. I thought it should can be divided by 30°(1/360).

Thanks for your help!!

Kevin

  • No one an idea?

    It makes no sense for me.

    Thanks!

  • Were you able to figure this out ?  

  • That the angle could only scaled from 0 to 1 was really silly. Based on the periodicity of the cos and sin functions of course it can go higher than 1. I was just confused by a description which says it has to be scaled from 0 to 1.

    The exact value of 0.57 for the offset is still a riddle. Of course i have to differentiate between electrical and mechanical point of view.
    In my opinion 0.58333 would make sense. (180°+30° => 0.58) So i would round it to 0.58 not to 0.57.

    But it was quite difficult to test this. Today i recieved the F26096, before i just had the F28096M which do no not support the iqmath library correct.

    So today i was able to test it and it looks really good. Only the sensorless control did not work. But i hope to solve this problem tomorrow.
  • Hey Kevin,

    Thanks for the information, but I believe this position offset is different for each motor ? it would be much harder to control the position of the motor is this position offset was incorrect. Usually they use Bemf and the hall effect sensor signal to figure out the values of the offset. Any ideas or comments on this ?