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2 DOF Simulator with 4 motors

Discussion in 'DIY Motion Simulator Projects' started by Bassaisho, Jul 25, 2016.

  1. Bassaisho

    Bassaisho New Member

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    Hi to everyone my name is Bassaisho and i''m new on this amazing website and sorry for my english i'm Italian.

    I want to build a simulator with 4 electric motors using 2 Monster Shields.
    I made some movement tests with a 3D software and function seems all right
    The only thing that worries me is the Arduino software to control the motors. I looked at the RacingMat_2DOF_Arduino_code but I can't edit it to make it work with 4 engines.
    I want to use a universal joint in the middle to support the weight.
    Immagine 1.JPG Immagine 3.JPG Immagine 5.JPG Immagine 6.JPG Immagine 7.JPG

    With a very low buget i can realize this simulator because i already have the frame and mechanical parts i only need the electrical part.

    Would someone know how to help me?

    Thank you very much ;)

    To be continued...

    Update soon.

    Attached Files:

  2. Ads Master

    Ads Master

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  3. BlazinH

    BlazinH Well-Known Member

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    If your sketch ups are an accurate rendering and unless you plan on supporting weight at the u-joint with a telescoping member and a spring or some other support, this design is physically impossible and won’t work due to the non linear aspect of motors using levers.

    edit: unless you develop a custom motor controller that will automatically compensate that is.
    • Agree Agree x 1
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  4. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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  5. momoclic

    momoclic Active Member

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  6. BlazinH

    BlazinH Well-Known Member

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    Actually I don’t believe this design needs much modification from the sketch up renderings to work. Since it’s a 2dof, then it should work with a fixed u-joint in the middle as long as equality is considered everywhere in the design. Most importantly, the non-linearity of levers must be taken into account. This is easily done by assuring that when the platform is in its level or neutral state, that all the levers connecting rods are perpendicular to their respective levers. The non-linear movement is therefore equal when moving in either direction from that position. It appears the motors just need to be moved upwards from the floor somewhat so the levers can move downwards further to make this happen.

    As far as software, any 2dof arduino sketch should work with this design. But 2 arduinos will be needed to run four motors with any of the sketches you can download from here. Then proper Simtools axis assignments should take care of the motion without requiring any modifications to sketches.

    However, still with this type of design, if one or more of the motors ever have a problem keeping up with the others, it can bind and cause damage.
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  7. Bassaisho

    Bassaisho New Member

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    I don't use sketch but solid works and it provide me not only the rendering but a motion simulation and so it's physically possible.


    why to controll the motors i need 2 arduinos? Arduino UNO have 6 PWM pins and i need only 4 right?

    Thank you you helped me a lot looking these projects.


    UPDATE:

    I'ts time to build a motorbike simulator.
    I take a frame from an old scooter (400cc) and now i wand to cut all the uneccesary parts to meke it more lighter.
    20160726_180939[1].jpg 20160726_180931[1].jpg
    I order all the electronic parts and in 1/2 weeks they arrive.
    I think 4 wiper motors (i buy a 12V 30A 360W power supply) and an u-joint cansubstain the weght when i fold (i suppose a maximum of 30° of roll).

    If some one have good ideas don't hesitate to reply in this post ;)

    To be continued... :popcorn
  8. BlazinH

    BlazinH Well-Known Member

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    That’s why I edited the post to state its possible if you write a custom motor controller that will speed one motor up while slowing down the opposing motor to compensate for the unequal non linear design. But that’s easy to fix by moving the motors as I stated.

    What I said was you would need two arduinos if you were to use sketches you can download from this site. Generally, the most any sketch can do is 3 motors unless you modify one. However, upon checking on myself, I did find this.
    https://www.xsimulator.net/community/threads/arduino-code-to-drive-4-motors.6828/

    There’s really no reason to not use two Uno’s though with them being dirt-cheap.
  9. momoclic

    momoclic Active Member

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  10. RacingMat

    RacingMat Well-Known Member Gold Contributor

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  11. Gadget999

    Gadget999 Well-Known Member

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    This sim should work with one arduino and 2 motor drivers.

    Wire 2 motors together on one driver but swap the polarity so one turns the opposite way !

    Use potentiometers on one end only
  12. MarkusB

    MarkusB Active Member Gold Contributor

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    @Bassaisho, maybe I have overlooked your explanation for this, but I still don't understand why you want to use 4 motors for just 2DOF. Actually 2 motors would be enough for this.
    Maybe your reason is that 4 motors are stronger than 2, but then you could better invest in 2 stronger motors than in 4 weaker ones.
    Besides, if you will have any inaccuracies in your build, I see the problem that the motors could "fight" against each other due to the fix pivot point.
  13. matthew loomis

    matthew loomis Member

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    You code will be very diffrent. In the designs I see here each axis is able to move independantly. When designing it is suggested that motors should be able to "run away" with good reason, it happens. Loose pot, wire, keyway, etc. Happened to me. If you had a run away it would tear your rig apart. Simtools is also setup for axis control, not
    You could instead use 2 motors per axis point. Same movement, same power, runaway safe, easy to code. Cog, balance would be more important though.