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Question Convert 6dof Stewart platform to SimTools

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Chris_Beeves, Sep 30, 2020.

  1. Chris_Beeves

    Chris_Beeves Active Member

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    That was my guess too.
    It was probably calculated in Simulink.. I unfortunately don't have access to that code.
  2. Gadget999

    Gadget999 Well-Known Member

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    ok i suggest you mod the smc3 code to use encoders instead of pots

    it might be easier than you think

    alternatively - use a board that counts pulses and converts to a voltage - put this board between the smc3 and the encoder

    its not a clean solution but it will prevent you missing pulses and loosing position - may be a better solution in the long run


    how many pulses per revolution and how many turns on the actuators on full movement
    Last edited: Oct 2, 2020
  3. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    Something like this:

    https://www.tindie.com/products/tronicgr/encoder2position-module/
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  4. Gadget999

    Gadget999 Well-Known Member

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  5. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    My Motion Simulator:
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    Yes, read the page, has limit switches, and instructs the motor controller to move automatically to the limits to calibrate for the range.

    Each one is for one encoder only...

    2018-04-01T19_30_46.020Z-Encoder2Position schematic.jpeg
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  6. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    Hi @Gadget999 if@thanos does not have any more of these i have 6 which i bought fo rmy orginal DC driven 6DOF actuators only uesed for testing, before i switched toAC servo setup , PM me if Thanos does not have any , i could be tempted to sell mine if it helps :)
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  7. Chris_Beeves

    Chris_Beeves Active Member

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    I have a little update on this!
    I tried rewriting the code in smc3, but I couldn’t make it work and it was hard to isolate the problem. Instead I put 3 2-channel DACs on the Mega. After some wrestling with that, yesterday I got the rig moving with smc3utils!
    Finally!! :D
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  8. Gadget999

    Gadget999 Well-Known Member

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    good job !

    so the smc3 code is as normmal and you are using a encoder-to-voltage converter ?

    what parts did you use ?

    have you got a video of it working ?
  9. Chris_Beeves

    Chris_Beeves Active Member

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    Yeah, something like that. The mega counts all encoders and sends the position feedback to three completely standard smc3’s. It is not an excellent solution since it has no calibration feature. Nor do my actuators have end stop switches.
    Not sure how to walk around this, but as long as they start from zero and don’t lose count of steps, it works.
    Nice to have some room for improvement. ;)

    The DACs are mpu4812’s if I remember correctly.

    I have yet to try everything together. Only tested one pair of actuators. Might get some time to play with it tomorrow.
    Will shoot some video as soon as I can pry my hand off the emergency stop button. ;)
  10. Chris_Beeves

    Chris_Beeves Active Member

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    May I ask how you made the calibration function? Set the feedback voltage to a high value and zeroed when limit switch kicked in?
  11. Chris_Beeves

    Chris_Beeves Active Member

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    @Thanos , bumping this a little. Having issues making it work the way I want it to.
    I'd really appreciate any direction nudge! :D