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6 DOF Inverse Kinematics & Maths

Discussion in 'Off Topic - All other stuff here' started by telfel, Jul 16, 2015.

  1. telfel

    telfel Active Member

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    Hi All

    Been a long time member lurker, I had slowly been collecting hardware to build a 6gof platform.

    Due to personal circumstance I will not be able to build / use a 6dof platform

    On the hardware front I had the following kit as to me this looked like the simplest kit, given my lack of
    coding skills

    6 x 590 watt 24v dc gearhead motor 130 rpm
    3 x sabertooth 2x60 kangaroo Motor Drivers / Controllers
    6 x Magnetic Encoders
    12 x limit switches
    6 x server psu

    having got most of the hardware together there was allways a lack of the software to control the 6dof platform

    All the chat about AC or DC motors all comes down to the fact that more powerful motors are required, that also means that the platform needs to be made stronger with finer tolerances.

    No disrespect to anyone who has built a 6d0f but the lack of proper 6dof maths is catered for by slack in the system.

    Given the extra amount of interest in 6dof platforms, Is it possible to get members to contribute either time or financially to get the 6dof maths sorted

    ps If not Ian @ bff simulations has the 6dof math setup are we ok to discuss this software on the forum?

    regards Terry
    • Like Like x 1
    telfel, Jul 16, 2015
    #1
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Adding 6 DOF Inverse Kinematics & Maths to SimTools, and how that may be helped along or achieved, is really a question for @yobuddy in the first instance as the SimTools developer.
    • Agree Agree x 1
    noorbeast, Jul 16, 2015
    #2
  3. telfel

    telfel Active Member

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    Hi @noorbeast

    Yeah @yobuddy has mentioned 6dof maths before, I was trying to see how many members, were interested and getting some sort of community project going.

    As an example say you paid a developer to code 6 dof and sim tools onto a cheap dev board

    raspberry pi2 so as to take the load off the gaming pc

    just a thought

    regards Terry
    • Agree Agree x 1
    telfel, Jul 16, 2015
    #3
  4. SeatTime

    SeatTime Well-Known Member

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    My Motion Simulator:
    AC motor, Motion platform
    IMO. You are correct, with out the proper maths then some of the 6DOFs when using SimTools can be average at best Eg. Surge. Unfortunately just adding 6DOF maths is only part of the required solution, as from having a 5 axis sim I know that without the proper working movement filters 'washout' etc then high speed returns can detract from the wanted movement ( could never get the current Simtools washout filters to work properly o_O) . I originally though this was an issue, but as I like the Stewart Platform design and experience has shown me that there are other ways to skin a cat, I will not actually be using my new sim as a true 6DOF:eek:. Heresy I know:p, but by using the Rift and my old 5 axis sim for some time it has taught me allot of what is and what is not important movement wise with a motion sim, so the lack of the proper maths is not really an issue for me. In regard to Ian's BFF software - have no idea, but it seems to lack the range of plugs-ins for different games that I would like to use. Don't get me wrong, if it fell into my lap and all worked then I may use it, but it not being available at the moment is not an issue for me.

    As for the Community paying for someone to code the 6DOF for Simtools, well basically 'we' (the community) do not own/control it...Any decision on what goes in, or out of Simtools is the current developers decision.
    • Like Like x 1
    • Agree Agree x 1
    Last edited: Jul 16, 2015
    SeatTime, Jul 16, 2015
    #4
  5. value1

    value1 Nerd SimAxe Beta Tester SimTools Developer Gold Contributor

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    My Motion Simulator:
    2DOF, DC motor, JRK, Joyrider
    The 6DOF inverse kinematics math is very much an off-the-shelf, plug'n'play code.
    However and as already mentioned by @SeatTime, the tricky part is beyond the positioning of the lever.
    It's about washout, how do you minimise the rotational effects when simulating an acceleration, in this very moment of the car, how to best simulate surge or sway: by tilting the platform or by accelerating the platform – or maybe a combination of both, depending of the position of the platform.

    While the inverse kinematics is pure coding, the correct positioning is art!
    • Like Like x 1
    value1, Jul 16, 2015
    #5
  6. Mmcool

    Mmcool Member

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    My Motion Simulator:
    2DOF
    What about classic washout filters? I don't think that just the 6DOF inverse kinematic math will be enough, meaning the accurate positioning is important, but you will have to think of the human that will be on top of that platform as well!

    Mike
    • Agree Agree x 1
    Mmcool, Jul 16, 2015
    #6
  7. BlazinH

    BlazinH Well-Known Member

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    I have a question (to anyone)? Why is it that 6DOF inverse kinematic math must be part of Simtools in the first place? We already get the outputs from all the axis. Isn't that what is needed along with specifications of the platform for the calculations? Why not use a socket (NET) to simply send the information to a secondary program to calculate it and then forward it from there to your controller? Any individual with the ability could do that regardless of what simtools developers do. It would be great if it was part of simtools though! :)
    BlazinH, Jul 17, 2015
    #7
  8. yobuddy

    yobuddy Well-Known Member Staff Member Moderator SimAxe Beta Tester SimTools Developer Gold Contributor

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    Yes, you are correct @BlazinH about it not needed to be built in. (but I’d still like to see it one day)

    Whenever I can, I make a test app that catches the output from SimTools.
    I then make the app do the needed function.
    And once I’m happy with the results, I add the code into SimTools.
    The only catch here is doing it this way; you have to write your own interface output.

    For a test app thou, it would be really nice to just have it linked to a 6dof Google sketch up model.
    So we can work on testing out the 6dof math.
    We could also figure out what Settings are needed to configure peoples Stewart platforms.

    I would like the user to be able to use either linier actuators or ac gear head motors.
    Depending on what they have.
    Once integrated with SimTools, I believe the 3D output (stewart platform output) Should use <Axis7> thru <Axis 12>.
    This way you can run the simulator with 2d or 3d math depending on the game (it may not have yaw roll pitch available)

    For those of you that have played with the 6dof master program,
    you may have noticed that the center of gravity does not move with the machine as the DOF’s are applied.
    But it may be a great place to start for non linier output?

    In the end, I don’t think we need to hire anyone.
    I’m sure we could figure it out; it’s just a matter of time and us putting out heads together I think…

    Take care guys!
    yobuddy
    • Like Like x 3
    yobuddy, Jul 17, 2015
    #8
  9. BlazinH

    BlazinH Well-Known Member

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    @yobuddy, that sounds like a good way to start out!

    Maybe I shouldn't have made my post above using questions. But my point was really that you guys (simtools developers) are already busy doing other things and living life and that the community could do this on their own without having to put it all on you guys all the time. But it would be even better doing it with your help! ;)
    • Agree Agree x 1
    BlazinH, Jul 17, 2015
    #9