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New problem on a Old Rig

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by DJJohnson, Oct 2, 2022.

  1. DJJohnson

    DJJohnson New Member Gold Contributor

    Aug 8, 2021
    Gladstone, Michigan
    - 51Coins
    +12 / 0 / -0
    My Motion Simulator:
    3DOF, Arduino

    About a year ago I built a motion rig using Sim Tools. Last month I broke the weld on my sway motor connecting arm and had to pull the rig apart to fix it. While I was at it, I replaced the clear air tubing connected to the pots with black rubber fuel line from NAPA, it has a tighter fit and does not slip as much.

    It's been over a year since I’ve dealt with the settings of SMC3 & SMC3Utils, in fact I only ever had to re-adjust the tubes on the pots. As soon as I got everything put back together, the rig will not run right. I have all the pots zeroed and leveled, but I get a nasty chattering and jerking as I increase the motor power up past 125. This still happens when I sit in it. I tried this with Sim Tools and Microsoft Flight Sim 2020, An awful ride!

    So, focusing on just Motors 1 & 2 I set Kp at 400 like the instructions recommend. I nothing else set, other than opening up the clip limits.

    Here’s my current settings for motor #1, same for motor #2

    Kp = 400

    Ki = 0

    Kd = 0

    Ks = 1

    Fpwm = 35kHz

    PWMmin = 50 ; enough to let the motor to let go

    PWMmax = 200 ; I weight about 250lbs, need power to hold my butt

    PWMrev = 200 ; Kind of thinking it needs to be the same as max

    MAXlimits = 0

    Clip Input = 0

    Dead Zone = 0

    So, Do I need some settings for the PID values?

    Here’s some video:
  2. Ads Master

    Ads Master

    +0 / 0 / -0
  3. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Jul 13, 2014
    Innovative tech specialist for NGOs
    St Helens, Tasmania, Australia
    +10,263 / 48 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    I find it helps to post a picture of all settings, rather than text or video.

    The SMC3 settings are explained in the second post of the thread: https://www.xsimulator.net/communit...driver-and-windows-utilities.4957/#post-48121

    You do need to configure Clip and Max settings:

    Clip Input Used to create a band at either limit of the target range beyond which any values sent to the SMC3 are clipped. In addition to this clipping, if the motor feedback does move beyond this range (typically through inertia), the SMC3 will attempt to brake the motors hard by driving them in reverse until they are back out of this limit zone. The value can be anything from 0-255 (however can’t be less than the current limit setting). Reverse braking is applied in the band between the Clip Input and the Max Limit settings. Reverse braking can be disabled - refer to PWMrev.

    Max Limits Used to create a band at either limit of the feedback range beyond which if the motors move (typically through inertia) the SMC3 will automatically shutdown the drivers and keep them disabled until reset. This is essentially a safety mechanism if something goes wrong. The value can be between 0-255 (however can’t be greater than the current clip setting).


    PID refinement depends on how your rig responds to input, it can be a complex topic. Wile written with another controller in mind the principles are the same, so here is a gentle layman guide to PID, which includes links to more technical aspects depending on how far down the PID rabbet hole you want to go: https://www.xsimulator.net/community/faq/a-laymans-analogy-guide-to-pids-pid-tuning.219/
  4. Gadget999

    Gadget999 Well-Known Member

    Dec 27, 2015
    +410 / 8 / -0
    My Motion Simulator:
    2DOF, DC motor, Arduino, 6DOF
    try a different usb port - i had a similar problem with a usb cable