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Question Floppy motor issues

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Rav3n87, Jan 11, 2023.

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  1. Rav3n87

    Rav3n87 Active Member

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    Hi all,

    Have been doing a bunch of investigating on an issue I'm having with floppy motors at the top and bottom of square wave :(

    Hardware:
    Arduino
    Cytron Md30c driver
    Motion dynamics 200w 25:1 worm drive

    Does anyone have any experience with the smc3 code?

    I think I may need to somehow alter the braking in the code smc3 utility pwmrev doesn't appear to be doing anything

    Video below of the issue for reference



    Cheers
    Rav3n87, Jan 11, 2023
    #1
  2. Gadget999

    Gadget999 Well-Known Member

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    its hard to see form the video - what youer your P, I, D numbers and what is your PWMmax, pwmrev and pwmmin
    Gadget999, Jan 11, 2023
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  3. Rav3n87

    Rav3n87 Active Member

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    Hi Gadget,

    Kp=500
    KI=o
    KD=0
    KS=1

    PWMmax=110
    PWMrev=110

    Have tried alot of different settings, Noorbeast recommended the above settings for the tests he was helping with in my build thread, I don't think the settings in SMC3 utils is going to be the fix unfortunately

    Cheers
    Rav3n87, Jan 12, 2023
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  4. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
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    Set pwm max and min to 255

    Now set p to 1

    Slowly increase p till the sim starts moving

    Get it to track the sine wave

    If it oscillates increase the d number
    Gadget999, Jan 12, 2023
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  5. Rav3n87

    Rav3n87 Active Member

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    Ok no worries, Will do when i get home and post a video of the results


    Cheers
    Rav3n87, Jan 12, 2023
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  6. Rav3n87

    Rav3n87 Active Member

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    Hey @Gadget999 heres the latest test



    Let me know your thoughts

    Cheers
    Rav3n87, Jan 12, 2023
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  7. Gadget999

    Gadget999 Well-Known Member

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    its overshooting - try a smaller P number

    its a lot better and only a problem in square wave which does not happen in real life

    (my guess is you are getting interference on the pot when the motor goes full load)

    what pots do you use ?

    is the pot wire sheilded ?

    what motors do you have ?

    you could try a small capacitor across the pot
    Gadget999, Jan 12, 2023
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  8. Rav3n87

    Rav3n87 Active Member

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    My Motion Simulator:
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    Have tried a bunch of different settings and tests,

    There's alot more on my build thread if your happy to take a look?

    Pots are good quality hall effect, using shielded cable and routed well away from motor wires

    Motors are motion dynamics 200w 25:1

    Motor drivers are cytron mdc30

    Cheers
    Rav3n87, Jan 12, 2023
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  9. Gadget999

    Gadget999 Well-Known Member

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    make the p number much smaller - show another video pls of sine and square
    Gadget999, Jan 12, 2023
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  10. Gadget999

    Gadget999 Well-Known Member

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    How many volts are the motors ? Can you run a smaller voltage ?
    Gadget999, Jan 13, 2023
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  11. Rav3n87

    Rav3n87 Active Member

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    Hi @Gadget999

    here's the latest



    Voltage is 12v battery sits stable around 12.5v

    Cheers
    Rav3n87, Jan 14, 2023
    #11
  12. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
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    Ok it looks prerty good

    I think what you are seeing is the backlash in the gearbox !

    When the motors are loaded with some weight this will not be there

    Good job !
    Gadget999, Jan 14, 2023
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  13. Rav3n87

    Rav3n87 Active Member

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    Unfortunately it is there when loaded, that's where I started with the testing on my build thread with Noorbeast,

    I'm pretty sure the code needs editing for my driver/motor combination or I need 50 or 60:1 gearboxes

    At the end of the video above when I grab the arm with my hand I can move it a fair bit,

    if I increase the kp higher the problem gets a little worse and I need to when I connect the rod back up,

    Even when I had it dialled in the best I could get it when driving down a straight the cockpit rocks side to side because the motors will not hold center correctly, back lash is fine I understand that's inherent with the design but there is about 4mm of backlash at the furthest center to center hole and this is rocking about 50mm
    Rav3n87, Jan 14, 2023
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  14. Rav3n87

    Rav3n87 Active Member

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    Is there a way in the arduino code to increase the braking around center? It has a "soft" zone where ever it stops like it is not providing enough power to the motors to hold the position

    I will post another video to show you what I mean
    Rav3n87, Jan 14, 2023
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  15. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    Braking around center (really target position) is normally associated with PID tuning, here is a gentle layman analogous introduction, originally with different hardware/software in mind, but really the principles are the same, with links to more accurate hardcore PID information: https://www.xsimulator.net/community/faq/a-laymans-analogy-guide-to-pids-pid-tuning.219/

    An overshoot should be easily handled by settings, but in your case, and tests, I get the sense there may possibly also be control board hardware issues, though I am not sure why.
    noorbeast, Jan 14, 2023
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  16. Rav3n87

    Rav3n87 Active Member

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    Here it is:

    Rav3n87, Jan 14, 2023
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  17. Rav3n87

    Rav3n87 Active Member

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    Thanks @noorbeast

    i will have a read through,

    The only reason i keep going back to the code possibility is because it was modified to work with the cytron drivers and i was hoping that perhaps the settings in the mods are the cause of the issue on 25:1's but just not noticeable on 50 or 60's
    Rav3n87, Jan 14, 2023
    #16
  18. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    This is a good example of the issue.

    The long lever seems to exacerbate the issue, but I don't think is the cause. Nor do I think the code is the cause.

    Rather than try for max SMC3 settings (PWMrev/max) I think it more helpful to identify and dial in the values where there is an effect, much as you did for kp: https://www.xsimulator.net/community/threads/floppy-motor-issues.17578/#post-235040

    See the explanation for each SMC3 setting here, for example Clip Input: https://www.xsimulator.net/communit...driver-and-windows-utilities.4957/#post-48121
    noorbeast, Jan 14, 2023
    #17
  19. Rav3n87

    Rav3n87 Active Member

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    OkI doki, tried playing with the setting again,

    Results are:

    Pwmmin does absolutely nothing

    Ki a value over makes it go crazy

    Kd doesn't do anything that I can tell

    Tried smaller settings of kp and mix in I and d

    Tried higher settings of above

    Tried lower pwm settings and high and low of kp I and d

    The only thing I can think of now is the motor gearboxes I have simply are not strong enough to do what I'm asking of them

    Will replace the front two for now and keep the tl one as is

    Going to purchase the 320w 60:1 units from motion dynamics I think, I really like the idea of those sfu units from Dof reality because no backlash but that might have to wait a bit I think haha
    Rav3n87, Jan 14, 2023
    #18
  20. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    The wormdrive ratio will have a significant effect, dependent on the design, mass of the upper frame, and inertia.

    I guess if I have a concern it is that you are seeing, and can't manage, overshoots when the rig arms are disconnected.
    noorbeast, Jan 14, 2023
    #19
  21. Gadget999

    Gadget999 Well-Known Member

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    It could be your cryton driver will only switch on at 20% pwm but you only need it to move at 5%

    Do you have another type of driver you can try ?
    Gadget999, Jan 14, 2023
    #20
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