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Showroom My compact 6DOF Project

Discussion in 'DIY Motion Simulator Projects' started by agroum, Jun 27, 2017.

  1. Spit40

    Spit40 VR Flyer

    Joined:
    Nov 3, 2016
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    United Kingdom
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    2,750Coins
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    My Motion Simulator:
    3DOF
    Cool. Thanks! I like his writeup about this. This guy is really into his flight sim. Are you using any of his stuff?
  2. SeatTime

    SeatTime Well-Known Member

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    My Motion Simulator:
    DC motor, Motion platform, 6DOF
    I have his 6DOF software and can easily use it if I want, but my system is beyond 6DOF which it does not support.
  3. agroum

    agroum My solo 11 years ago Gold Contributor

    Joined:
    Jun 24, 2017
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    Occupation:
    Mechatronics engineer / part time aero master
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    Canada
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    My Motion Simulator:
    Motion platform, 6DOF
    Hi

    With Xplane or FSX/Prepar 3D you receive the 3 angulars speed in rad/sec,and the 3 accelerations.

    -Angles
    So you will have to integrate the angular speed to obtain the angle. To push the platform to come back to his 0 deg position you will need to make a highpass filter of about may be 0.7hz. Each angle can have a different frequancy. All the filters will depend of the kind of plane you want to flight. Fighter jet and cessna will have very different values of frequencies.

    -linear motion
    You will need to intagrate twice to pass from the accelaration to the position. Then you gonna need highpass filters too to bring back the platform to the 0 postion. (You can cheat putting just a gain and a filter if it's to complicated, the result can be great too but only with linear move to keep a minimum of accuracy)

    -acceleration effect
    It will be calculated with the longitudinal accelation ( the one from the nose to the back ), it's not needed to integrat that one, just a gain and a low pass filter can achieve this. The ouput of that will be add to the pitch of your platform.

    -0 Position
    Bringning back the platform to his 0 degree and position is necessary with aircraft. By exemple if you are flying and turn to the left you will feel the angular accelerationand then you will be in a coodinate turn wich imply that you will stop to feel that you are turning and you will not fell the angle because the latteral acceleration are almost 0.

    So the platform needs to come back slowly at a 0 degre position while there is no more angular move.

    - The filters
    It can be hard to make numerics filters without a specific knowledge, but probably it's possible to find C++ highpass filter.
    The filters will depend of the type of filter (Ex tchebychev), the order of the filter, the band (highpass, lowpass, etc) , the value of your filter ( in rad/sec or hz) and the sampling frequency.

    -Precision of the platform
    If you want more precision you will need a mathematical model of your platform.

    You can take a look at this http://pages.videotron.com/iscience/FlightSim_Motion_Platform/washout_filters.html
    All what I describe is call the washout filters. I didn't made exactly that but it can help to understand.
    • Informative Informative x 1
    Last edited: Jul 7, 2017