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Adjusting for increasing offset with instaSPIN position move

Shiran Qu
Prodigy 110 points

Hi there,

I am using lab13b as a reference for a position controller for a sensored system. On this system we have two encoders, one for motor's angle and another on the output of the system to measure its absolute angle, after a series tendons. Because of the system, there is an variable offset between these two angles. I have a few questions about alternative the system to compensate for this.

1. is it possible to constantly update the position reference of the  SpinTAC position move function without a change in velocity? I tried to add more points or states as in lab13c, but there is always a stop in between states and we would require constant velocity.

2. Is it possible for the SpinTAC position move libraries to constantly adjust for this offset?

3. Can I use my second encoder, which does not reference the motor's angle, as the mechanical angle for SpinTAC position move and the motor's encoder for the electrical angle? This way the mechanical angle would reflect the angle of the system.

Thank in advance!

  • 0
    TI__Guru** 119680 points
    I sent this to Adam who answers MOTION questions. He's out of office this week but should respond next.
  • 0
    Guru 12800 points

    1. If you are not using SpinTAC Move to generate a profile you can update the Position Start field (cfg.PosStart_mrev) which will immediately be reflected onto the Position Reference.  Be sure to respect the position rollover of this signal.

    2. SpinTAC Position Move generates point-to-point relative movements, it isn't designed to deal with any absolute positioning system.  That should be handled in your software

    3. You should be able to do this, however it is important that you have correctly accounted for the gear ratio between your mechanical encoder and your electrical encoder, else the system won't spin as expected.  You should be able to make this fairly seamless by changing the pole pairs provided to SpinTAC components to reflect this.  I have never personally tested this, but I believe it is possible.