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Question output arm shake problem

Discussion in 'SimTools DIY Version' started by yangsqr, May 11, 2020.

  1. yangsqr

    yangsqr Member

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    My Motion Simulator:
    2DOF, DC motor, Arduino
    The output arm movement encounters shake problem. I use SMC3, arduino and hall potentiometer. I have tested the hall potentiometer, the output is smooth and continuous.

    During output testing the situation as follows:
    1. When the output value is zero, there is no shake.
    2. Adjusting the output to any angle, when the output arm is in place, it starts to shark and cannot stop. (the movement process is smooth)
    3. Adjust the output value back to 0, most of the time there is no shake, and about 20% chance of shake again.


    I tried increasing the smoothing value in the Axis Assignments setting, but it will not reduce the shake.
    IMG_1189.JPG
  2. Ads Master

    Ads Master

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  3. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
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    what does the pot signal look like in the SMC3 util program ?

    have you adjusted the PID settings inside the SMC3 ?
  4. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    Try adjusting your PID and add a little SMC3 dead zone.
  5. yangsqr

    yangsqr Member

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    My Motion Simulator:
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    This is a test when I adjusted the potentiometer by hand (no motor connected) , it looks good.
    test.jpg
  6. yangsqr

    yangsqr Member

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    Thanks guys
    Based on the experience of drones, I know that adjusting PID is a complicated task so there is no adjustment before. Now I will try to adjust in SMC3.
  7. yangsqr

    yangsqr Member

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    My Motion Simulator:
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    Without adjusting any parameters, The SMC3 "out mode - triangle" test is as follows, and it looks good.
    IMG_1200.JPG


    When I manually adjusted to a angle and stopped (SMC3 out mode - manual), output arm did not shake.
    Last edited: May 12, 2020
  8. Gadget999

    Gadget999 Active Member

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    please send us a video/image of the output on the sine wave

    setting Kp 300 Ki Zero and Kd zero is a good place to start

    (it looks like your Kp number in the triangle test is not big enough)
  9. yangsqr

    yangsqr Member

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    Thanks SeatTime I will try this.
  10. yangsqr

    yangsqr Member

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    My Motion Simulator:
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    Sadly, the left motor died yesterday.... and it ’s unclear whether it ’s a motor failure or a drive failure
    The sine test is as follows:
  11. BlazinH

    BlazinH Well-Known Member

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    If those are the PID settings you actually use its just a P controller though. For that output the math is simply (a Simtools axis, the setpoint - feedback) * single multiplier = motor speed. Other than that you just need to test for what direction they need to run. True its very easy to set P only but its quite a waste of a good PID controller. And theoretically a balanced system will never reach a setpoint using P only.
    Last edited: May 13, 2020
  12. yangsqr

    yangsqr Member

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    Thanks to Gadget999&SeatTime, I have tried: Kp 300 Ki 0 and Kd 0, there is no shake now.
  13. yangsqr

    yangsqr Member

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    What you said is very reasonable, now I shuould start to learn the principle of PID control
    Last edited: May 13, 2020
  14. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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  15. Gadget999

    Gadget999 Active Member

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    your output should track the sine curve exactly - increase the P number so so the motor is working harder and the slowly add D until it is stable
  16. yangsqr

    yangsqr Member

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    My Motion Simulator:
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    I tried to increase kp to 1000, so... it seems that my motor is too slow?
    IMG_1246.JPG

    Attached Files:

  17. MarkusB

    MarkusB Active Member Gold Contributor

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    Kp is not the only parameter. Please try increasing PWMax.

    Edit: And have a look here for an explanation of all SMC3 parameters.
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  18. yangsqr

    yangsqr Member

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    Thanks MarkusB, After the PWMmax increased to 150(adding more has no effect), the effect is very good, two curves almost coincide.
    IMG_1247.JPG
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    Last edited: May 13, 2020
  19. yangsqr

    yangsqr Member

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    I increased the PWMmin to 80 and the curve looks better:)
    IMG_1248.JPG
  20. MarkusB

    MarkusB Active Member Gold Contributor

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    Perfect. Note that the rig will probably behave different when you are sitting in it, so that you may need to re-adjust the settings again.

    When you are done with configuring the settings in SMC3 Utility, the next step will be to set up Game Engine.

    When I did this for the first time, I had very smooth motor movements in SMC3 Utility, but rather jittery movements with Game Engine's output testing.
    If you also see this happen, you may need to increase the Fpid value. In my case, I changed it to Fpid/4. After this, the motor movements were also nice and smooth in Game Engine. If this does not help, you also need to decrease Kp.
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  21. yangsqr

    yangsqr Member

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    I will try more adjustments, your tips are very helpful. Thanks MarkusB