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Help on eQEP for motor spinning

Aishwarya Apte
Prodigy 50 points

Hi I am using TILaunchpad F28069M for spinning PMSM. I want to use eQEP pulses for speed and position feedback. How to find position offset for index pulse for 4 pole machine

  • 0
    Intellectual 995 points

    Hello Aishwarya,

    I understand that you are looking for a phasing method, is that right? Are you familiar with things like electrical angle and mechanical angle?

    Janos

  • 0 in reply to Janos Szeman
    Prodigy 50 points

    Hi Janos

    I am aware of concept of electrical zero and mechanical zero. I am having 4 pole machine means it is having 2 electrical zeros and one mechanical zero. My question was there is some time lapse between electrical zero of machine and index pulse arriving and when you are giving position feedback this difference is required to be offset. How to calculate this offset. 

  • 0 in reply to Aishwarya Apte
    Intellectual 995 points

    Hi,

    After reset, let's say that the position is zero, the mechanical angle is zero and the electrical angle is assumed zero. You need to manually rotate the motor by slowly rotating the electrical angle until you find the index pulse from the encoder. Detailed steps below.

    1. Gradually increase torque at zero electrical angle to the maximum allowed. (id=0, iq=torque, park angle = 0)
    2. Start rotating the park angle until you find the index pulse. At this point the difference between the calculated electrical angle and the park angle is your phase offset. Depending on your code you may need to calculate the offset in encoder increments.

    BR,

    Janos