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new 6DOF stewart platform

Discussion in 'DIY Motion Simulator Projects' started by Gadget999, Feb 15, 2019.

  1. Gadget999

    Gadget999 Active Member

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    I have been thinking about a 6dof for a while and have decided to get started soon

    my 2dof is not 100% completed it needs the new DD wheel wiring up and its ready

    this time i have thought long and hard about how to do the 6DOF

    the plan is to use a flat platform so i can switch different sized seats over - my son is much smaller than me !

    the dilemma was always what do you use for the acuators ?

    Ballscrews and motors - a popular and neat solution - however in reality not that cheap and from what i can see they are quite noisy

    Chain/ Belt Drive - this looks like a neater solution to the ballscrews and this style whilst not so popular has good performance without the noise

    Gearmotors - these are the simplest and cheapest way to build a diy sim. they are readily available and are not too expensive. Levers and pushrods do not look as neat as a ballscrew but if you spec them correctly they are very suitable

    the gearmotor lends itself to a very compact sim that can fit into a small room / area

    ------------------------------------------------------------

    Actuation Length ? lots of people go for long actuation lengths and end up with a tall and gangly looking sim. if you look at the videos of 6dof driving sims they do not have that much vertical movement when on the go - only when you hit a bump or crash. The longer length actuation seems more suited to flight sims with lower acceleration

    professional sims seem to have limited actuation movement with more emphasis on g-seats to fool the driver


    i have ordered up some gearmotors and hope to see them here in the next week or 2 - i may end up using 12 of them to really make a powerful sim

    -------------------------------------------------------------

    So the first thing to think about is the platform size

    what made you choose the size of the hexagon you used as a base and would you use a different size if you did it again ?

    what sort of angle should the actuators be at ? should it be 60 degrees vertical and horizontal for maximum efficiency ?
  2. Ads Master

    Ads Master

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  3. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
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  4. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
    2DOF, Arduino
    some motors and a hydraulic pump and actuator

    i have quite a few motors now all the same spec and more on thier way

    all the same gearbox 25:1
    24v
    17 amps

    watts = volts x amps = 24 * 17 = 408

    135 rpm

    more on thier way so i will have 12 soon enough

    6 is enough to start building


    (I also have 6 hydraulic rams, I am going to plumb it into the actustor and see how fast i can drive it with 24v - might be a whole new type of rig - might be a big flop too !)

    so i have to decide how to mount the motors to the base - do I mount them so the motors all face towards the centre or do I mount them so they sit in pairs on the sides of a triangle

    hopefully will find time to run the hydraulic test tomorrow

    Attached Files:

    • Like Like x 1
  5. SilentChill

    SilentChill Problem Maker

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    My Motion Simulator:
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    Be interesting to see how the rams work , if they are fast enough they would be great
  6. Gadget999

    Gadget999 Active Member

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    The hydraulic actuator test was not a great success

    The thing leaked everywhere and made a mess and the speed was very poor.

    The motor i have is for a much smaller bore.

    I will look at a more powerful pump but i guess it will work best with a high pressure 3 phase pump and solenoids to drive each actuator
  7. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
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    wanted to discuss the centre of rotation before i design my new sim

    the higher up the seat is from the base of a stewart platform the more effort is required to tilt the platform

    I understand the best experience will be where the chest and head of the occupant will be where the sim rotates around

    can the sim not know the lengths of the actuators and the height of the platform and simulate rotation around the sweet spot ?

    is this what the thanos software does, but not the smc3 software ?

    do i need to design the sim so the actuator ends are at chest height ?

    does the sim need to look like this


    [​IMG]
    [​IMG]


    or like this


    [​IMG]
    [​IMG]
  8. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    My Motion Simulator:
    AC motor, Motion platform, 4DOF, 6DOF
    In both cases you have to set the COG (center of gravity), to be little higher (for the recessed platform) or much higher for the second one.

    The hexpod adjusts the inverse kinematics math based on the center of gravity to always have parallel surge or sway, no matter if the COG is higher or even lower than the plane of the actuators.

    The COG usually is placed a little above the chest of the pilot for optimal use of the internal equilibrium of the ears to avoid getting nausea from motion sickness.
    • Informative Informative x 1
  9. Gadget999

    Gadget999 Active Member

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    platform and base sizes ?

    should the base be larger than the platform, or should they be the same size ?

    if the platform is smaller then it may add some stability due to the actuators being tipped inwards


    actuator arm angles ?

    should the actuators sit at a particular angle ? is 45 degrees optimal or should be be more like 60 ?
  10. Diving Delica

    Diving Delica New Member

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    My Motion Simulator:
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    Hi All,
    I too am wondering on the general platform sizes and actuator angles. My thought was that actuators would have to be 60 deg, eg 6*60 deg = 360 deg. Am i wrong?
    if I have actuators that have 300mm stroke and a closed length of 1000mm, i should get approx 150mm of lift? If top frame is the same as the bottom frame and actuators are @90deg to base my frames would be about 2040mm along each side????? Am i completely off track with this assumption??
  11. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
    2DOF, Arduino
    i have gone for a triangular base that is 1.3 M on each side spaced out with flat joiners on the edges
    the platform is a triangle that is 1 M on each edge

    constructed from 50mm box

    pics soon
    • Like Like x 1
  12. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
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    I ordered up a much smaller bore hydraulic ram - it looks promising, will hopefully find some time soon !
  13. Gadget999

    Gadget999 Active Member

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    image of the frame attached - welding the motor brackets next

    Attached Files:

    • Like Like x 1
    • Creative Creative x 1
  14. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
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    Some pics of the build

    I have one motor wired up with a 180 degree pot and an arduino nano

    It appears i only have 90 degrees of movement - is this because i have 180 pots not 360 pots ?

    Attached Files:

    • Like Like x 2
  15. pmvcda

    pmvcda aka FlyPT

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    My Motion Simulator:
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    Yes, you need 360º for more degrees unless you use a gearbox to reduce, but you loose precision.

    Is that a Speedster/Vx220? Yours?
  16. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
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    I am only using 180 degrees of movement - so 180 pots should be correct

    I will try and change the code so it uses the full range

    I might be able to use a resistor in parallel

    The vx220 is not mine :(
    • Like Like x 1
  17. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
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    i have a motors working with SMC3 and a EV-VNHD7012AY h bridge driver

    the spec of the driver says it will switch up to 28v

    my motors are 24v

    however the driver does not seem to work when powered from 24v :(

    they do work when powered from 12V

    the 12v supply is a 72 A server power supply

    the single motor is lifting the rig platform up and down
    I am measuring approx 22 amps (12v) the single motor is doing a lot of work because the other motors are getting pulled up and down whilst they are unpowered

    should i be running these motors at 12v or 24v ?

    ( i also tried a IBT-2 - it appears to shut down at 15 amps no where near the 43 amps it should be able to take)
  18. Gadget999

    Gadget999 Active Member

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    video of testing here

  19. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
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    ok some testing of the 100 A motor driver

    Man these things have some balls !

    i will be ordering a few more and running with them

    --------------------------------------------------------------------------

    they have enough power to trip out the power supply - i had one motor lifting my whole weight on its own !


    so i need to buffer the 24V power supply - i see a lot of you are using batteries as an accumulator

    would it not be better to use capacitors to buffer the load ?

    has anyone used capacitors before ?

    Attached Files:

  20. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
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    ok i am going to buy 2x12v car batteries and use them as a buffer(24V)

    so the next step is configuring simtools

    i plan to have 3 arduinos - 2 motors on each so 3 interfaces, each on a different com port

    i have the first pair working and i can move them in the software

    how do i set up the axes for a 6dof ?

    is it 2 axes per arduino and they can all do each of the 6dof ?

    i have attached images of how i think i should set up the first arduino / motors

    do i set up arduino 2 and 3 the same ?

    any suggestions greatly appreciated :)

    (does sim tools see each arduino as a 2DOF ?)

    Attached Files:

  21. Mortisedsnail36

    Mortisedsnail36 New Member

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    do you by chance know which motors you using and the specs.