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Cable-driven GSeat on 6DOF, V1 finished, V2 in progress

Discussion in 'DIY Motion Simulator Projects' started by Grigory, Aug 20, 2018.

  1. Grigory

    Grigory Active Member

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    Hi Everyone,

    While I'm waiting for some of the components for my new relatively compact 6DOF to arrive, I'd like to share some information on the progress in completing the g-seat, which I eventually plan to put on the moving platform.

    Weight of the seat is important in my situation, so I decided to use aluminum as much as possible and to use bowden cables while placing the motors away from the seat. I have Transtecno 350/500W DC motors left from my first 6DOF, so I will be using four of these to drive the flaps.

    Here is the general design without padding:

    1.png 2.png 3.png

    IMG_8043.JPG

    IMG_8074.JPG





    The flaps will be driven by four motors with 200mm leadscrews:

    4.png




    The motors will be controlled with two Sabertooth 2x60 + Kangaroo x2 -- again, these are left from my original 6DOF.

    The cables are the ones used for the bicycle brakes. I hope they will be strong enough.


    The problem that I have not yet solved is where to place the shakers. I am using SimVibe and my current static seat has two transducers mounted underneath it. With the lower flaps contacting the frame only at a single hinge point very close to the central line of the seat, I suspect that left/right side vibrations will not be sufficiently separated. Maybe I should try to fit the shakers to the heave flaps themselves?
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  2. Grigory

    Grigory Active Member

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    Things are moving, the motor assembly is almost ready. I just need to add sabertooths and connect encoder and limit switch wires.

    EA63C996-3FF1-42C9-83E3-8ECD367FD273.jpeg
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  3. SeatTime

    SeatTime Well-Known Member SimTools 2.0 Beta Tester

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    Looks great - four actuators in the one enclosure :thumbs.
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  4. Grigory

    Grigory Active Member

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    Okay, it's alive. Everything works, kangaroos autotune just fine, but why do I always end up with a spagetti monster?!

    IMG_8386.JPG IMG_8385.JPG

    The plan is to assemble the seat itself and try to actually control it with cables tonight.
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  5. Grigory

    Grigory Active Member

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    Seat assembly took quite a bit more than I expected. I only managed to install it on the rig yesterday. Here is how everything looks now:

    IMG_8401.JPG IMG_8402.JPG IMG_8404.JPG IMG_8403 (1).JPG

    Hopefully, I will be able to connect the remaining three cables tonight and proceed to testing.
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  6. Grigory

    Grigory Active Member

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    I finally fitted the cable between the actuator and one of the heave flaps and did the first test. The test revealed two issues:

    The first problem is that the plastic end caps for the cable sleeve are too soft and get destroyed almost immediately. I’ll need to manufacture a metal replacement.

    The second problem, which looks more difficult, is that the part of the cable that goes from the actuator to the rig and basically hangs in the air twists and warps when when the actuator pulls hard. This absorbs the pull and the flap does not move as it should. I’m not yet sure how to fix that. Maybe the bicycle brake cable which I use is not strong enough for the task.
  7. Grigory

    Grigory Active Member

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    Problem solved! I discovered that while the wires in my Bowden cables were for bicycle brakes, the housing happened to be for the gears. Brake housing is considerably thicker and stiffer.
    I replaced the housing — and everything worked! No more twisting or warping problem.

    Here’s the first test after connecting everything:

    I’m now passing heave, sway and surge values from simtools via network interface to my own VB.Net application which translates these values into commands sent to the Kangaroos. This way I can code any type of filter, process signals in a linear or non linear fashion - basically, tune everything in any way I may want. The same application manages wind simulation.
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  8. Grigory

    Grigory Active Member

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    Just as I expected, now I have a prolem with feeling SimVibe effects. My shakers are mounted to the cockpit structure and I can barely feel any vibration coming through the hinges of the lower gseat flaps.

    I probably need to somehow connect the shakers to the lower flaps themselves. I’m not yet sure how to do that without obstructing the movement.
  9. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    Have you considered a jetseat or similar vibration cushion? I have a KW908 which I took apart and embedded the small vibration motors in the cushions of my backrest and seat flaps. It gives good localized effects and the intensity varies depending on how hard that particular flap is pushing against me.

    Here you can see the backrest cushions completed and the motors for the base of the seat before they were fitted.

    E331B9D7-3BAD-4D5A-A198-B5C01B40384E.jpeg
    • Creative Creative x 2
    Last edited: Aug 30, 2018
  10. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    Could you share more pictures or video of the bowden cable connection to the actuators? I’m fascinated to see them in action. Does each cable only pull (I noticed the bungees on the backrest flaps)?
  11. Grigory

    Grigory Active Member

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    Thanks! I actually wanted to try that, but was not able to find any such vibration cushion available for sale.

    I really like how SimVibe/shakers work, so I think I’ll try to figure out how to make my shakers work as they did before changing the seat.
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  12. Grigory

    Grigory Active Member

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    Yes, the cables are just pulling. I’m using bungee cords for the back and my weight seems to be sufficient to quickly bring down the lower flaps.


    Here are some photos:
    9D47E28A-F8C2-4155-B845-2D7C2D1EDF08.jpeg A7AD5846-5906-4594-AE8D-22E12E1F02FA.jpeg F3C5B486-C70B-44A8-BE45-B62CA34BC45A.jpeg 488643FB-28BC-4B4A-9FF8-06667F7C59BD.jpeg 48EEDBE7-7962-4E70-8230-2C75D570053B.jpeg
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  13. Pierre Lalancette

    Pierre Lalancette Lalancelot Gold Contributor

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    I don't know how you guys succeed in doing your stuff so rapidly. I am so slow and sloppy.

    Very exciting stuff. Since SeatTime introduced the pulling cable, people finds all sort of ways to use it. Keep on the good work!
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  14. Grigory

    Grigory Active Member

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    Here's how my VB.Net app looks:

    SimInterface.png

    I initially used it to get the current speed from SimDash and to generage commands for the Sabertooth running the simulated wind fans. Now I'm also using it to control the G-Seat. The app gets Surge, Sway and Heave from SimTools and sends commands to Kangaroos based on the set of parameters, that can be tuned in real time.

    I can set the flaps' neutral position and separately control how much effect negative and positive input values have on the actual flap movement. The shown settings, for example, mean that when all the inputs are at zero the flaps should be at 20% of their full travel. When going over a bump, the flaps will push using not more than 70% of the remaining travel, or not more than 80% * 70% = 49% of full travel range. When going over a pothole, the flaps may decrease the pressure by not more than 20% * 50% = 10% of the full travel range. The similar adjustments can be applied to the turns, when the movement limits for the flaps on the outer and the inner side of the turn can be individually specified.
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  15. Grigory

    Grigory Active Member

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    While this seat works fine, I am thinking of making a second version, mostly to improve the looks and comfort:

    - V2 will be based on my previous fiberglass bucket seat
    - V2 will only do surge and sway. I do not even use the existing heave flaps now, 6DOF fully takes care of heave.
    - V2 will also be cable-driven.

    I also intend to experiment and replace the hinged flaps with linearly pushing plates. I did not see other people using this in their gseats, so this approach may certainly have drawbacks. However, this design is easier to integrate in my bucket seat and just requires drilling few small holes.

    This is the general idea:

    IMG_0100.jpg IMG_0097.jpg IMG_0095.jpg IMG_0101.jpg

    The seat will have three pushing plates: two for sway and a single back plate for surge.

    The plates will be actuated like this:


    upload_2018-11-13_10-29-24.png

    Attached Files:

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  16. Pierre Lalancette

    Pierre Lalancette Lalancelot Gold Contributor

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    I get the feeling that the plate would be more stable if the cable was comming out by the back instead of the side.

    Comment base on no calculation or experience. Just feeling.
  17. Grigory

    Grigory Active Member

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    After thinking more about the feeling that a single back plate will produce, I decided that it would not actually be realistic. During acceleration, the plate will push me closer to the driving wheel and make me counter that force with my hands, which should happen during braking, not acceleration.

    So I decided to stay with the two back flaps design, but using push rods and rollers:

  18. Grigory

    Grigory Active Member

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    New version of Gseat is ready.

    1BD2CD74-94A8-446E-B0F9-5E8C1DE79324.jpeg

    I finally decided to drive the flaps with the mechanism previously installed on the first seat. It’s now mounted to the temorary frame screwed together from aluminum tubes, but I will weld a new cleaner frame over the weekend.
    AF154C29-FFA9-421F-8572-7640931B370E.jpeg

    The cables are pulled with two NPC-T74 motors controlled with a sabertooth 2x60 and a kangaroo.

    09948585-E6E9-41D5-8627-199E3A05FD45.jpeg 0815646C-DCA0-43EC-A726-B0436F92C3A8.jpeg
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  19. Pierre Lalancette

    Pierre Lalancette Lalancelot Gold Contributor

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    Looks really nice. When will we see it in action?

    I really like the way you fix the Vive tracker. LOL
    Last edited: Dec 7, 2018
  20. Grigory

    Grigory Active Member

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    it’s actually not working, I just forgot it there :)

    I have not yet been able to solve the problem with high-frequency vibrations killing tracking.