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My 2dof project for $200 and NO welding (+$100 for Traction Loss + $200 for G-seat)

Discussion in 'DIY Motion Simulator Projects' started by Qlittles, Sep 27, 2017.

  1. Qlittles

    Qlittles Active Member

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    My Motion Simulator:
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    As you can see from the previous post, I have the G-seat flaps on the seat. I cut home holes in the seat and built a contraption on the backside of the seat where there are 2 60kg servos powering the flaps:

    20190926_130534.jpg
    (The seat-belts are moved to the center just for the photo)
  2. Qlittles

    Qlittles Active Member

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    The total cost of my hybrid G-seat build was a little shy of $200. Some trouble-shooting and difficulties:

    1) How to keep the pressure on my body when the seat-belt pulls from the back. The solution was to use a seat-belt for my chest (so, it looks like an "H"), with a contraption in-between the center of the "H" and the middle of my chest. Because it causes the center of the "H" to be farther forward than my chest, when the seat-belt pulls from the back, most of the force is felt right through that contraption and unto my chest.

    2) The 30kg motors for the bladder and the seat-belts worked without having the ground in the arduino board. Because of this, I probably spent about 3 hours trying to get the 60kg servos to work, not knowing that I had to plug the ground connected to the arduino board. (The solution is obvious now).

    3) I reasoned that a 60kg motor might not be strong enough to handle the flaps. Because of this, I put the hinge near the horizontal middle of each board so that most of my body weight will be pressed right on top of the two hinges (which are secured to the chair frame). It works well, but there are few moments when the flaps are not extended all the way. However, I only notice it when I'm looking for it. Because this is a budget build, this was the solution without having to purchase a stronger motor or multiple ones.
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  3. Qlittles

    Qlittles Active Member

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    4) Oh, another problem was and is that the 30kg motors are not fast enough. When I purchased the motors, they were very cheap, at $15 a piece. I didn't check the speed of these motors, but they only .20 sec for 60 degrees. It was an impulse buy... I should have researched the motors before the purchase.

    5) Finally, one of the concerns I had was making the servos work only for half of the motion. For example, I don't want the flaps to go backwards when I press the brakes. My concern was whether or not I could understand the code enough to fix this problem. Thankfully, this was already addressed here: https://www.xsimulator.net/community/threads/007-g-seat-ultra-compact-servo-based.10470/

    Related to this, one of the problems was that I had already secured all the servos. When I tried the mod to the code, it made the motors move only in specific ranges for all of them (I couldn't customize for each servo). Because of this, I had to re-position 4 of the servos. I believe it was mentioned elsewhere that there is also a solution within Simtools using custom max and min values for each Axis. However, I wanted a hardware (well, at the level of Arduino programming) solution instead of having to adjust it for every game in Simtools. I am afraid that I'll forget and that the flap will attempt to go backwards -- if that happens it'll probably break either the motor, the arm, or the flap attachment.

    Anyhow, the build is relatively satisfactory. However, I'm having trouble with the following, which leads me to a question I have difficulty solving.
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  4. Qlittles

    Qlittles Active Member

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    My Motion Simulator:
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    MY PROBLEM:

    In Simtools, I want the seat flaps to respond to both Surge and Sway motions. This is obviously easy to do. However, because my flaps have a limited amount of travel, I want the Surge and Sway to be more than 50% of the whole travel length. For example, I want to press on the gas, which will max the surge to maybe 70% of the travel. If I turn at the same time, I still want to feel the Sway, but for the Sway to use the remaining 30%. If I am not pressing the gas, and the car is just cruising, and if I make a turn, I want the Sway to now take 70% of the travel. In this state, if I press on the gas, than the gas will take the remaining 30% of the travel to make the 100%.

    I think the easiest solution is to initiate a limiter so that Surge is 70% and Sway is 70%, but the travel will never exceed 100%. I can also imagine a solution where the Surge and Sway overlap to share 40% of the travel.

    I have tried tweaking some things in Simtools, but am having difficulty figuring this out. Am I missing something obvious? I hope I am.

    Any help will be greatly appreciated :)
  5. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
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  6. Qlittles

    Qlittles Active Member

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  7. BlazinH

    BlazinH Well-Known Member

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    Maybe I'm not following you but I don't know why you can't just set both surge and sway to 70% in axis assignments settings. And anything that goes over 100% gets clipped.
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  8. Qlittles

    Qlittles Active Member

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    Yes, my problem I think might have an obvious solution that I am not aware of. When I put surge to 100% on the axis and test it out with output, the servo arm reaches point X when the slider is moved to 100%. However, when I move the sway slider (with the surge at 100%), the servo arm moves beyond point X. If I do 75% on the output slider with both surge and sway, again the servo arm surpasses point X. Maybe I just don't know how to make simtools clip at 100%? It seems like an obvious and basic function of simtools that it should have...
  9. Lgars39

    Lgars39 Member

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    Really excellent! Congratulations on your challenge, as what with work you do not need to have a big wallet to have fun
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  10. Qlittles

    Qlittles Active Member

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    Thank you! I wish I had an unlimited hobby budget -- there's some squeaks and margins of loose movement (because of the wood?), but the immersion payoff is great!
  11. BlazinH

    BlazinH Well-Known Member

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    Posting a screenshot of your axis assignments would be helpful to know for sure what you're doing. With surge axis set to 100% and when the output slider is at 100% point X as you call it should be at its maximum range. For example when using 10bit output with 100% on both the output should equal 1023, the largest possible using 10bits.
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  12. Qlittles

    Qlittles Active Member

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    Hey BlazinH! Yes, you were right -- I was misunderstanding how the Axis, Axis limiting, and output work. I lowered the Axis limiting, and I got the clipping at 100%. Also, because now I was not afraid of going over the limit, I re-positioned the servo arm junction so as to get more torque. Now the 60kg servos are plenty (I'm 155 lbs) and the hiccups have disappeared, and I'm getting more detail out of the flaps because of using more range. Thank you!!
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  13. Qlittles

    Qlittles Active Member

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    I've tuned the flaps, and they work great!

    However, the bladder bags on the right and left of my thigh have some drawbacks:

    1) Because I'm using slower motors, I can distinguish the lag especially with the flaps moving faster than the bladder (the 60kg servo is much faster).

    2) For some reason, I lose air in the bladders slowly over time. I think this is fine for short sprints in racing, but for races that are 30 minutes or longer, the bladders slowly lose their force. I'm not sure if this is happening because my hose is a little smaller than the connector (I couldn't push it in all the way).

    3) The bladders do add immersion, but not as nearly as much as the flaps. I think the better option would be to make flaps on the bottom as well (like most other G-seats). However, if I did that, I would need much stronger servos and I'm not sure if the payoff would be worth it (especially because the G-seat is already on a 2 dof). If you have both a 2dof and a G-seat with flaps on the bottom, it'll be great if you could share your thoughts.