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Question 6DOF with servomotors for flight sim in VR

Discussion in 'DIY Motion Simulator Projects' started by dureiken, Aug 4, 2017.

  1. dureiken

    dureiken Active Member

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    Hi there,

    (sorry for my bad english)

    I am starting a new project, as said in the title : 6DOF motion platform with servomotors for flight sim in VR.

    I will use this kind design : http://x-sim.de/forum/viewtopic.php?t=1599.

    The aim here is to make a blog for those like me who are beginners and what to start this kind of project. I will update first page as the project goes one.

    1-08/2017 : choice of motors and wormdrives

    [​IMG]

    I will buy 6 of : http://www.schneider-electric.com/e...ey---20-bit-encoder---w-o-brake-straight-con/

    with 6 servodrive : http://www.schneider-electric.com/e...-23---single-phase-200...255-v---750-w---can/

    I have really good price @work !

    And for wormdrive : NRMV040 with 80:1 ratio : http://www.zetek.ru/files/en/Gears/pdf/wormgeared_motor_nmrv.pdf
    [​IMG]

    And here are my final specs for around 20cm and 40cm of heave movement :

    [​IMG]

    Excel files is available if needed, just PM.

    I made a lot of attempts before choosing these ones, with different ratio, motors, levers ... to have good linear speed/acceleration and enough torque.

    My motors will work on 120° to have less radial movement.

    2-08/2017 : a little bit of design

    Sorry but I'm beginner with Fusion 360 software.

    Determination of global size, function of angle and lever :

    [​IMG]


    [​IMG]

    Static part :

    [​IMG]

    Mobile part :

    [​IMG]

    And beginning of 3D :

    [​IMG]

    And a draft :

    [​IMG]


    And now ? I really have no idea how to put mobile and static part, which angle, radius are the same ?


    I would need your help now to continue the project ! @Thanos @noorbeast


    Thanks a lot
  2. dureiken

    dureiken Active Member

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  3. dureiken

    dureiken Active Member

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  4. dureiken

    dureiken Active Member

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    Hi guys,

    to begin with design, I start this morning a simplier 3DOF platform


    Middle :



    [​IMG]



    Down :



    [​IMG]



    Up:

    [​IMG]



    Total heave : 350mm



    Max Pitch (30°)

    [​IMG]



    [​IMG]



    Thanks
    • Like Like x 5
  5. dureiken

    dureiken Active Member

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    Hi guys !

    little changes to the plan : due to a lot of conversation with @Hoddem and @SeatTime I will go to a 6 DOF with linear actuators, driven my my servomotors.

    I also just bought a Prusa MK2S 3D printer !

    Here is a project of Linear, HIGHLY inspired from @Hoddem thread ! all credits are for him :)

    [​IMG]

    I will go for a 1610 screwball, not a 1605. With 3000 rpm motor it should be 500mm/s.

    I need your help for the following.

    Design of the platform

    Linear actuator can move by 450mm, and rod ends are fixed to 35° max (will adjust once I get them). Radius of mobile is 40mm less than base platform.

    Here could be a design with 500mm of space between 2 rods on the base, 6 DOF :











    https://www.youtube.com/watch?v=MxrOtjXoJ88&feature=youtu.be


    I also tried with 1000mm between rods

    To sum up values :

    [​IMG]

    My questions are :

    1-I see a lot of people with radius of platform nearly the same, I put 40mm, is that good ? how to choose ?

    2-We can see that with 500mm, all movements are better than 1000mm, Is there a limit ? is that a stability problem to have a really little space between rods ? what is the limit ?

    3-A lot use U-joint for base rod end, is there a special reason ? M14 rod end couldn't do the job ?


    Thanks for your help guys !
    • Like Like x 2
  6. dureiken

    dureiken Active Member

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    Nobody to help me ? With my 3 questions
  7. Tim McGuire

    Tim McGuire "Forever a work in progress"

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    My Motion Simulator:
    3DOF, DC motor
    Not entirely sure about the first two, but U joints are used on the bottom mount because if you had a rod end it would allow the actuator to wobble/rotate along its axis. The U joint stops it from rotating at all.
  8. dureiken

    dureiken Active Member

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    Thanks. And would it be a problem of I put an end rod ?
  9. Tim McGuire

    Tim McGuire "Forever a work in progress"

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    My Motion Simulator:
    3DOF, DC motor
    It's not ideal, as you want the assembly to be rigid if possible, but it will work.
  10. dureiken

    dureiken Active Member

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    Ok thanks :) I will try and change if needed
  11. dureiken

    dureiken Active Member

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    I tried with u joint at the bottom and the top of linear actuators but I cant do anymore Yaw. I assume it's due to the lack of rotation in the u joint ?

    We need a rod end and a u joint right ? Thanks
  12. Tim McGuire

    Tim McGuire "Forever a work in progress"

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    My Motion Simulator:
    3DOF, DC motor
    Yes you're correct, you need a rod end at the top, and a U joint at the bottom.
  13. dureiken

    dureiken Active Member

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    Ok :) could I put rod end at bottom and u joint at top ?

    Or the start reaction of the motor should go in the bottom not in the mobile platform ?

    Thanks
  14. Tim McGuire

    Tim McGuire "Forever a work in progress"

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    My Motion Simulator:
    3DOF, DC motor
    Usually most people mount the U joint at the bottom and the rod end at the top. Not sure what you meant by the second sentence.
  15. dureiken

    dureiken Active Member

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    I would like to put u joint at the top to have a better angle for the platform.

    When the motor starts, there's a opposite start reaction of the actuator I assume, If the u-joint is at the top, this start reaction will move the mobile platform ?

    If the u-joint is on the base, nothing will happen ?

    Dunno, I'm trying to analyze why almost all people put the u-joint on the base
  16. Tim McGuire

    Tim McGuire "Forever a work in progress"

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    My Motion Simulator:
    3DOF, DC motor
    The reaction will push in equal and opposite directions on either end of the actuator, which joint is where doesn't make any difference for that. If you feel having the U joint at the top of the platform will be better for leverage then you can do that, I think most of the other 6DOF builders use the rose joints at the top because it's just easier to build the platform that way.
  17. dureiken

    dureiken Active Member

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    Hi guys,

    I made some little progress, here is my linear actuator, inspired from @Hoddem and @wannabeaflyer2

    [​IMG]

    [​IMG]

    [​IMG]

    using 2 12mm linear guide for 12mm bearings and one 30mm flange bearing on the top.

    Just CAD for the moment :)
  18. momoclic

    momoclic Active Member

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    My Motion Simulator:
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    As mentioned above, the advantage of putting a Cardan joint at the base of the cylinder is that it will prohibit the rotation of the cylinder on itself.
    Otherwise the angles taken by a ball joint can be compatible, possibly with the angle magnifiers.
    On the other hand with this last type of assembly, as you drew the cylinder, you will be forced to imagine a system that will prevent the cylinders from making a quarter turn (?) With each change of direction of rotation of the motors.
    It would seem more pertinent to place a joint of Cardan on the side of the structure of the jack, that which holds the motor ?
    • Agree Agree x 1
  19. Zed

    Zed VR Simming w/Reverb Gold Contributor

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    My Motion Simulator:
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    I would think it's weight and bulk for putting a U-joint on the bottom. It's always best to keep the moving part of the platform as light as possible and most rod ends are going to be lighter than a U-joint. And U-joints have at least some bulk to them. Better to deal with that on the stationary part and keep the interface to the moving part svelte and sexy. :thumbs (In my opinion...)
    • Agree Agree x 1
  20. dureiken

    dureiken Active Member

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    thanks for your feedfbacks. I put u-joint at the top because even with high end spacer for rod I have +/-27°, and I would like to go to 35° pitch and roll