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3DOF with AC drives

Discussion in 'DIY Motion Simulator Projects' started by tanito90, Jun 1, 2018.

  1. tanito90

    tanito90 New Member

    Joined:
    Jun 1, 2018
    Messages:
    2
    Location:
    Argentina
    Balance:
    139Coins
    Ratings:
    +0 / 0 / -0
    My Motion Simulator:
    3DOF, AC motor, Arduino
    Hello everyone, i will be starting a project in 2 months and i am going through the design phase right now

    The hardware chosen would be: 3 1.1Kw Ac 3-phase drives, with gear reduction or chain driven with encoders, 3 VFDs, and 1 arduino board.

    Before someone says something about using AC drives: I have no choice, nearly no access to DC drives in my country, and a 200w nema 42 cost U$S900 vs a U$S500 combo (1500w ac drive + VFD). And i have plenty of experience with AC drives and VFD considering i am an automation technician and designer, so i am not afraid of them.

    So first of all, i want the sim to be as realistic as possible regarding the G forces, and for that i would need a long stroke and therefore a good acceleration. I was thinking of 0.7m/s (for what i've read it is a nice speed and it's not crazy to achieve with selected setup)
    Also, i was having the idea of replacing the gear reductions for Sprockets, what do you think of that? A fixed sprocket with motorcycle chain, they are inexpensive compared to the price of a reduction box (U$S300 vs U$S50). It also allows you to fine tune the ratios to find the most suitable for the application.

    DESIGN:
    I still can't decide myself on the design, here i left you a design i thinked of 5 years ago, which i rendered to simulate the motion in video, but i want to hear your thoughts about it about the central fork/spring, do you thin it will be needed to dampen the movements? or i should just make it aerieal? It will allow me to distribute the weight to a central point and allow the drives to move more freely without having to support all the weight.

    IF i want to make it aerial, according to my calculations it would weight more or less 120/130kg with driver. That distributed in 3 points would make 42kg, and a Force of 411N per pivot point. If i use a 30cm lever that would make a 123Nm Force needed just to hold it in place.
    if EFy= m.a ---- 40Kg x 0,7m/s2 = Fn(force needed) - Fw (weight Force).
    28N = Fn - 411Nm ------ Fn= 439Nm x 0,3cm = 131Nm

    My current engines have an 8 pole config, which means 800rpm at 60hz, and they have 18nm at that rpms, i would need them to run @20rpm with a lever of 30cm to move at 0,7m/s, which means that the ending torque would be: 720nm.

    What do you think? i could make it even faster but this are just my first calculations, i don't know if i am doing something wrong.
    Thank you very much
    tanito90, Jun 1, 2018
    #1
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
    Jul 13, 2014
    Messages:
    21,194
    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    148,844Coins
    Ratings:
    +10,920 / 54 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    Just so you know the video is unavailable, perhaps check the settings on Youtube.

    150-700mm/s is a good speed zone to aim for in producing good motion.

    However when it comes to actual G-Forces a motion sim aims to fool your brain rather than replicate actual G-Forces. A traditional motion sim will likely only produce momentary force of around 2Gs to fool your brain, not the actual sustained 5-10Gs of an F1 car or fighter jet.

    So if G-Force simulation is your priority do some research on G-Seats and G-Force simulation systems that the likes of @SeatTime and others have been experimenting with:

    https://www.xsimulator.net/community/threads/seattimes-sims.11757/#post-152436

    https://www.xsimulator.net/community/threads/harness-tensioner.11911/#post-156464

    https://www.xsimulator.net/community/threads/building-a-better-mouse-trap.11739/
    noorbeast, Jun 2, 2018
    #2
  3. tanito90

    tanito90 New Member

    Joined:
    Jun 1, 2018
    Messages:
    2
    Location:
    Argentina
    Balance:
    139Coins
    Ratings:
    +0 / 0 / -0
    My Motion Simulator:
    3DOF, AC motor, Arduino
    Well that's great, didn't know about that kind of simulation.
    I've also solved the youtube privacy settings, so now you should be able to see the video.

    Yeah i know it's not possible to simulate the actual G forces, i've wrongly expressed myself. I want it to be as realistic as possible with the options i have chosen (3dof, 720nm torque at shaft @20rpm).

    Thank you
    tanito90, Jun 4, 2018
    #3