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  1. #1
    Registered
    Join Date
    Mar 2004
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    1508

    DC servo vibrates at rest

    I have a CNC mill with DC brushed servos controlled by an 1880 Galil card...

    It is an old machine that has worked well for a great many years. I recently moved it 2000 miles. Just powered it up today. The Y axis will vibrate at the stop position. Move it and it may be fine or it may vibrate again. Put your hand on the servo and its rotating back and forth rapidly just a half degree or so.

    What should i do to correct this?

    Karl

  2. #2
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Posts
    23797

    Re: DC servo vibrates at rest

    Usually with Galil that has torque mode drives, it is in the PID tuning parameters.
    i.e. too much gain.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  3. #3
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    Mar 2004
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    1508

    Re: DC servo vibrates at rest

    These ran fine for more than a decade. Just re tune???

    I was guessing the move shook something loose or broke?

  4. #4
    Community Moderator Jim Dawson's Avatar
    Join Date
    Dec 2013
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    5182

    Re: DC servo vibrates at rest

    Retuning is what I would do also. Try bumping up the KD parameter, makes it react just a bit slower without affecting the stiffness much. I guess the other possibility could be encoder noise, loose connection? Maybe look at the raw encoder data to see how stable it is..
    Jim Dawson
    Sandy, Oregon, USA

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