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3DOF Jerky Jerky Motors

Discussion in 'New users start here - FAQ' started by DukeLeather, Dec 1, 2025.

  1. DukeLeather

    DukeLeather New Member Gold Contributor

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    Trying to calibrate my traction loss motor. This being the first of the 3 DOF. I've been fighting with this for over a week and can't seem to make any headway. Below I've listed all the specs of electronics I've used as well as all of the diagnostics I've attempted so far. I started with 3-IBT2 and then moved to a sabertooth 2x32 for the front motors. I've tested the traction loss motor with the sabertooth as well. I've also included photos and links to video of what is happening. Any suggestions would be greatly appreciated! Thank you!


    3DOF ELECTRONICS SPEC SHEET

    3 - MOTORS:
    (2) ElectroCraft Wheel Chair Motors
    o 22.5v
    o 275 watt (1000 watt peak)
    o Gear Ratio 32.79:1
    o Output Shaft 116 RPM

    (1) Pride Quantum Wheel Chair Motor
    o 24.0v
    o 200 watt (1000 watt peak)
    o Gear Ratio 29:1
    o Output Shaft 186 RPM

    3 - POWER SUPPLIES (one for each motor)
    - AC 170-250V to DC 24V 41.6A 1000W
    - Dialed in to exactly 22.5v
    - (12v 20A Computer Power Supply for low voltage testing)

    2 - ARDUINO
    2 - ELGATO UNO R3
    2 - ElectroCookie Uno Terminal Block

    3 – HALL SENSORS - 6127V1A180L.5FS

    3 - MOTOR DRIVER MODULES
    - IBT-2 BTS7960 43A H-bridge Double Motor Driver Module (Traction Loss Motor)
    - Sabertooth Dual 32A 6V-24V DC Motor Driver (2 Main Motors)

    SOFTWARE
    SABERTOOTH
    - SabertoothArduinoLibraries
    - SPS_8.2_softstart (Sketch) – Set to MODE 3

    IBT-2
    - SMC3 v1.0 (Sketch) – Set to MODE 2

    SMC UTILITIES
    - SMC3Utils v1.01


    DIAGNOSTIC TESTING – Jerkiness of Traction Loss Motor (all resulted in little to no change of issue)
    - Different computers
    - Different cables
    - Triple checked then checked again the connections to Uno
    - Shorter length of wire to Hall Sensors
    - Swapped Hall Sensors
    - Tested voltage at Sensors
    - Swap Uno R3 unit
    - Added power supply to Uno R3 for increased power instead of relying on the PC to provide power
    - Changed multiple IBT2 controllers
    - Changed to Sabertooth 2x32 controller
    - I tried different motors (same and different models)
    - Swapped 24v power supply for another
    - Changed out 24v power supply to 12v power supply
    - Tested voltages to controllers from power supply - constant
    - Tried 2:1 gearing and 1:1 gearing of Hall Sensor to motor shaft
    - Tried Fpwm Freq from 15kHz to 30kHz
    - High and low Kp testing varied the strength, but jerkiness would still happen to different degrees
    - Various PWMmin and PWMrev with little to no change
    - Tried all Fpid settings with no change other than motor hum


    VIDEO LINKS
    IBT2 with load:
    IBT2 no load:

    Sabertooth KP200:
    Sabertooth KP400:

    Attached Files:

    DukeLeather, Dec 1, 2025
    #1
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    Just a guess but try setting PWMmin=0, PWMmax=200 and PWMrev=120, rerun the Sine test and please post the result.
    noorbeast, Dec 1, 2025
    #2
  3. DukeLeather

    DukeLeather New Member Gold Contributor

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    Here we go. Still jerky but consistent left and right at least.

    DukeLeather, Dec 1, 2025
    #3
  4. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    You seem to have reduce Kp considerably. Can you please keep it at 400 for now, just to try and get a baseline with increased PWMmax and PWMrev.

    Similarly, it looks as though Max Limits and Clip Input have been dramatically reduced. Please just change one setting at a time and post the result, don't play with multiple settings at the same time.

    The aim is to get a ballpark initial setup, then refine from there.
    noorbeast, Dec 1, 2025
    #4
  5. DukeLeather

    DukeLeather New Member Gold Contributor

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    i can't put the Kp to 400 with the PWMmax at 200. It'll throw the thing off my bench.
    DukeLeather, Dec 1, 2025
    #5
  6. DukeLeather

    DukeLeather New Member Gold Contributor

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    I'll set it at 400 and slowly bring up the PWMmax and you'll see what I mean
    DukeLeather, Dec 1, 2025
    #6
  7. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    That may well be the case for your particular hardware, but initially it is all about trying to find some reasonable baseline, based on the provided SMC3 fundamentals: https://www.xsimulator.net/communit...3dof-motor-driver-and-windows-utilities.4957/

    So, the steps below are the foundation:

    Disconnect the motor power supply
    Make sure Simtools is not running – we’re not ready for that yet!
    Wire up the Arduino (with SMC3 installed) to your H-Bridges and connect to your computer via USB
    Run the Windows SMC3 Utility software and make sure it communicates with the Arduino (There is no need to set baud rates, they are not configurable)
    Set the Kp, Ki, Kd, PWMmin, PWMmax, PWMrev to 0 for ALL motors (This will make sure the motors don’t move)
    Set Clip to 255 (you need to do this first) and Limit to 255 (This will give you plenty of margin if something goes wrong while setting up)
    Turn on the power to your motors – nothing should move at this stage!
    Set Kp to about 400
    Now slowly, increase PWMmax… at some point the motor should start to move. When it does check the “Green” feedback line is moving toward the “Blue” target position.
    If it is then that motor and feedback is wired correctly - proceed to test other motors.
    If it is moving away turn off motor power immediately (or quickly reduce PWMmax again). In this case you need to either reverse the wires to the motor being tested –OR– reverse the +5V and GND wires to your feedback pot for the motor being tested (do not do both). Restart the test from the beginning.
    Do the above for each motor
    noorbeast, Dec 1, 2025
    #7
  8. DukeLeather

    DukeLeather New Member Gold Contributor

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    Here it is:
    DukeLeather, Dec 1, 2025
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  9. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    It does not look as though PWMmax was set to 200 as suggested.
    noorbeast, Dec 1, 2025
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  10. DukeLeather

    DukeLeather New Member Gold Contributor

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    I've done all this. Different controllers, sketches, power supplies, Arduino's, everything I listed above and still the same or a variant of the same motion. Could it be because I'm using a clone? The Elgato Uno R3. I have 2 of them and tried both.
    DukeLeather, Dec 1, 2025
    #10
  11. DukeLeather

    DukeLeather New Member Gold Contributor

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    it doesn't make it to 200. you see me bring it up slowly and the whole thing craps out at 90 or 100
    DukeLeather, Dec 1, 2025
    #11
  12. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Try lowering Kp to say 150.
    • Agree Agree x 1
    noorbeast, Dec 1, 2025
    #12
  13. DukeLeather

    DukeLeather New Member Gold Contributor

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    DukeLeather, Dec 2, 2025
    #13
  14. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    The 6127V1A180L.5FS Hall should be direct driven, it appears to be geared.

    You could try adding in some deadzone to see if that helps with the oscillations.
    noorbeast, Dec 2, 2025
    #14