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FlyPT Mover

Discussion in 'FlyPt Mover' started by pmvcda, May 30, 2019.

  1. alex928gt

    alex928gt Member Gold Contributor

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    The accelerometer's "seat" i.e. the strap or the rear part of whatever was holding it to the dashboard.

    You could btw simulate what you feel by putting your phone / accelerometer in a cupholder and record a movie of what goes on:
    - on throttling i.e. acceleration value going from 0 to X the phone will be projected against the rear part of the cupholder, or more precisely the cupholder will project itself forward against the phone -> forward kick into the phone
    - on disengaging the clutch without braking, i.e. acceleration value going from X to 0, the phone will just re-settle in the cupholder -> no backward kick, just a release of pressure
    - on braking the phone will be projected against the front part of the cupholder, which the phone would perceive as a backward kick

    The rear shock springs that get compressed under strong throttling and decompress when you release the throttle/disengage the clutch.
  2. alex928gt

    alex928gt Member Gold Contributor

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    Ideally yes but unfortunately not quite so, due to limitations of simulators that can't provide for long lasting accelerations. What you feel in the simulator can only be a combinations of cues that overall are expected to replicate what you would feel in a race car.

    For instance, the actuators from a simulator can provide the first kick forward corresponding to the start of the acceleration but can't provide a sustained acceleration feeling. Where the acceleration input remains at X the actuator will have to stop its move smoothly due to small stroke. That's where the g-seat and g-belt can help but these artificial sustained accelerations are not captured by the accelerometer, just felt on your back, legs and shoulders.

    I would therefore say that at least the transients/kicks in acceleration going from 0 to X or 0 to -X should match the kicks from actuators and we should avoid the false cues from acceleration going from X to 0 or -X to 0 generating wrong kicks. Hence my request.
    • Agree Agree x 1
  3. hexpod

    hexpod http://heXpod.xyz

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    4CCD3563-B469-4270-9E85-51D44AE94173.jpeg
  4. hexpod

    hexpod http://heXpod.xyz

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    “simulators (...) can't provide for long lasting accelerations.”

    Are you sure ?

    “The tilt coordination technique is used in driving simulation for reproducing a sustained linear horizontal acceleration by tilting the simulator cabin. If combined with the translation motion of the simulator, this technique increases the acceleration rendering capabilities of the whole system. To perform this technique correctly, the rotational motion must be slow to remain under the perception threshold and thus be unnoticed by the driver. However, the acceleration to render changes quickly. Between the slow rotational motion limited by the tilt threshold and the fast change of acceleration to render, the design of the coupling between motions of rotation and translation plays a critical role in the realism of a driving simulator.”

    source :

    https://www.researchgate.net/profil...ving-simulation.pdf?origin=publication_detail
  5. alex928gt

    alex928gt Member Gold Contributor

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    "Bus is slowing down".... you always make the same confusion between acceleration getting from positive to 0 (i.e. stop throttling or more precisely disengaging clutch and therefore stabilizing at constant speed) and "slowing down" (i.e. braking) which is acceleration value being negative.

    If the acceleration is strongly positive the ball would go backwards (for the guy in the bus) and would be "kicked forward" by the rear wall of the bus, when acceleration gets back to 0 (disengaging the clutch) the ball would just become steady and under braking it would go forward and be "kicked backward" by the front wall of the bus.
    Last edited: Jan 25, 2021
  6. alex928gt

    alex928gt Member Gold Contributor

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    Yes I'm sure. You can only increase the acceleration rendering capabilities using various tricks including tilting the platform, and probably also at the risk of making users sea sick by using too much tilting to try and replicate g-forces (see force dynamics simulators). And even in this way my feeling is that you can at best try and replicate 1g by being seated with you back being horizontal but what about more g-s?

    I'll let experts of 6-dof systems elaborate more on that anyway.

    In my case, given my simulator I can't anyway do better than kicks and g-seat and g-belt to try and replicate at best.
  7. hexpod

    hexpod http://heXpod.xyz

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    For me it remains same force vector regardless if you add or release the stress on your body. I don’t know why one, should be considered as right, and the other, as wrong cue. Interesting discussion.
    Last edited: Jan 26, 2021
  8. alex928gt

    alex928gt Member Gold Contributor

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    Very interesting discussion indeed.

    Let's take a very simple example to illustrate how what matters is what you apply and not what you release.

    You hit a ball, for instance with a pool cue, at t=0. That means that:
    - at t=0 you apply a strong force to the ball
    - at t=0+epsilon the force stops (it has to because the ball is now far away from the cue so the cue cannot apply a force anymore)

    What happens for the ball?
    - Starting at t=0 the ball starts moving in the direction of the force you applied with the cue (that's the kick).
    - At t=0+epsilon, the force stops. What does the ball do? Does it start going backwards or even stopping because the force disappeared? No, it just continues at constant speed (if we suppose there is no friction). No kick.

    So,
    - at t=0 we apply a force, the acceleration value of the ball jumps from 0 to a positive level, the ball starts moving after having received the kick
    - at t=0+epsilon the force stops, i.e. the acceleration value of the ball gets back to 0 (since F=m.a) and the only consequence is not a stop or a kick back, it's just that from this moment on it continues its way at constant speed.

    If you now do the same but not kicking the ball and rather pushing it with the cue for a while:
    - when you start pushing the ball you apply a force, the acceleration value of the balls increases from 0 to a positive level, the ball starts moving and "feels" a kick and a pressure in the back
    - when you stop pushing the ball with the cue the force on the ball stops, the acceleration value of the ball gets back to 0 (F=m.a) but there is no stopping or kick back, the ball just continues its way at constant speed, but does not "feel" anymore the pressure in the back

    It's exactly the same for the car and you on the seat of the car:
    - when you apply throttle (engine=the cue) the car accelerates, acceleration value goes from 0 to X, you get the kick, the same as the pool ball got the kick from the cue, plus a continuous pressure in the back.
    - when you disengage the clutch the acceleration value goes back from X to 0, and as the cue ball you do not get a kick backward or even stop, you just continue your way at constant speed, you just do not feel the pressure in the back anymore.
  9. hexpod

    hexpod http://heXpod.xyz

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    “the term "g force" is often used, the g is a measure of acceleration, not force.”

    Let’s take a closer example to your application.

    Let’s imagine in your game, you are starting accelerating at 1G during 5s.

    Because of a very tiny workspace of your platform, during this 5s at 1G, you was able to provide a longitudinal movement of your simulator but only for a fraction of a second.

    You applied a washout so your platform is centered for more than 3s doing nothing on this axis.

    Than, still in your game, you come from this accelerated state 1G during 5s. to a non-accelerated state of 0G for another 5s (let’s just take the friction out of the equation so we can imagine you are NOT slowing down)

    Normally, it will give you an opposite movement equivalent in magnitude during a fraction of a second.

    This opposite movement on your surge would be the same, as if you would start braking coming from 0G (constant speed) to -1G (heavy braking).

    Although in therms of motion of your simulator, those states are equivalent, in real life, in terms of perceived forces they are not. In one case you release the pressure (from your back), in the other one, you add the pressure on your arms or chest.

    I doubt that canceling the adverse cue would give you better realism but it would be interesting to test.
    Last edited: Jan 26, 2021
  10. hexpod

    hexpod http://heXpod.xyz

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    I wouldn’t underestimate the power of “tilt coordination”. Those “tricks” like you call them, when properly constructed, doesn’t make anybody sea sick. Don’t forget, the forces we are getting from games are local coordinated. Even if you tilt a bit your platform, you still get the movement in the right direction when you use a kinematic plugin. I don’t know if mover provide this for your geometry
  11. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    @alex928gt
    >when you disengage the clutch the acceleration value goes back from X to 0
    no, when you stop powering the wheels, the friction slows down the car (wind, road): hence acceleration goes from X to -Y instantaneously.
    Speed will go continuously down. Not acceleration. :)
  12. BlazinH

    BlazinH Well-Known Member

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    Agree this has been an interesting conversation. But like a few others I've taken a different approach to solve it by attempting to build a better simulator instead. The solution to many issues are solved with a torque based head motion system. Take this situation for example:

    "In an ideal simulator there should not be an additional kick, as the force vector doesn't change direction. The problem stems from the limitation a real world simulator has. How can the lessening of a continuous force be simulated if it wasn't continuous in the first place. Unfortunately the answer at least in the case of a gear change during acceleration is a kick in the "wrong" direction, otherwise our body can not be fooled into thinking the force was suddenly lost.
    But by changing the force vector we are suddenly ejected from the seat into the seat belt, when in reality the pressure into the seat would just be lessened."

    The above situation is resolved since torque is a variable but continuous force or lack thereof that is being applied. Other issues that are resolved are that when using a racing seat and a harness also your body is pulled into the sides of the seat during lat. acceleration, into the harness during braking, and into the seat during acceleration providing proper force vectoring. Since the idea is to stiffen your neck, shoulder and back muscles to counter torque, torque is therefore transferred down the torso with correct vectoring and pressure points on your sides, chest, and back :).
  13. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    yes, that :)
    or using a tactile transducer to transcribe the clutch effect (what i'm doing)
  14. alex928gt

    alex928gt Member Gold Contributor

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    You are right generally speaking but at low speed if the car is powerful we can very reasonably neglect wind and road friction effect vs change in engine force when disengaging the clutch. Conversely if instead of disengaging the clutch you just lift the throttle you'll get strong engine braking that would not be negligible. That's why I said "disengage the clutch" since in this case the change in acceleration can reasonably be considered as X to 0.

    In addition, what we are anyway discussing here is not the fact that friction would actually generate a minor braking - we all agree on that - but whether the acceleration value going back from X to 0 should generate a backward kick. And my answer to this is no for reasons expressed above.
    Last edited: Jan 27, 2021
  15. alex928gt

    alex928gt Member Gold Contributor

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    Again, sorry but no. Reverting to the analogy of the pool ball, if you stop pushing the ball with the cue i.e. get it from X G to 0 G the ball does not stop or revert back i.e. no backward kick. Conversely if you "brake" it - i.e. apply actual negative G then it will actually get a backward kick and stop.

    More generally with the pool ball:

    - Apply force F (0 G -> X G) it starts moving -> forward kick
    - Thereafter remove force F (X G -> 0 G) the ball DOES NOT stop moving but continues its way -> no kick

    There is therefore a clear asymmetry between applying F that makes the ball start to move/accelerate and removing F that just lets it go. We should get the same asymmetry in the move of the horizontal "surge" actuator i.e. 0 G -> X G -> actuator kick and X G -> 0 G -> no actuator kick, whereas currently both G changes are treated in a symmetric way by Mover.

    Yes indeed let's test it.
    Last edited: Jan 27, 2021
  16. hexpod

    hexpod http://heXpod.xyz

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    I mentioned it already, how about taking velocity instead of acceleration to feed your axis ?
    • Agree Agree x 2
  17. hexpod

    hexpod http://heXpod.xyz

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    No comment
    • Informative Informative x 1
  18. hexpod

    hexpod http://heXpod.xyz

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    How about the vid from above ? Do you see the head of the guy when he shifts (“let it go”). Still no back cue ? I see a huuuuge one ;-)

    Thanks for the discussion. Cheers - Ignacy.
  19. hexpod

    hexpod http://heXpod.xyz

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    Here a nice footage about group B cars from the 90s. Unfortunately in french but could still be instructive.

  20. hexpod

    hexpod http://heXpod.xyz

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    It could be the right moment to do so here as it might be related