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Discussion: Issues with 6DOF

Discussion in 'Ready, set, go - Start your engines' started by Trip Rodriguez, May 29, 2019.

  1. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Nah, just need the fake kinematics mode fixed.
  2. hexpod

    hexpod http://heXpod.xyz

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    You can’t fix something which was never broken man!

    I spend hours trying to explain how the things works.
    You may read again my emails
  3. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Alright guys, today I did my first tests with FlyPT and WOW. Really really great stuff, I can't wait for the new version! The filters look like they are definitely going to fix what is left of my smoothness issues.

    On a different topic I have an issue you guys might have opinions on.

    When the platform is near it's target position (small movements needed) each actuator kinda starts and stop repeatedly (and not all at the same time) until it reaches it. Each movement is like a little bump in the road, but I'm usually flying! They are kinda moving like zombie servos, all jerky and awkward. Very noticeable in straight and level flight in calm weather.

    I have two limitations possibly causing this, one of which I plan to solve as soon as possible.

    That is, my AMC1280 is set up for only 8 bit speed signal. I don't know if it will fix this, but all that is needed is to cut a few traces and solder on a few header pins and I can change it to 12bit speed output. I can't handle that tiny soldering, but my brother might and he is coming to visit very soon. My old AMC was running 12 bit, but I was focused on bigger problems so I can't say for sure whether or not it had fixed this.

    The other limit is I'm using the 10 bit analog sensors. Do you think that would contribute to this behavior? I don't want to replace them until they wear out unless they are causing a problem.


    Trip
    • Like Like x 1
    Last edited: Jun 20, 2019
  4. BlazinH

    BlazinH Well-Known Member

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    If you're still only using P start adding some I to your PID. That will help an actuator reach the setpoint before stopping.
    • Agree Agree x 1
  5. hexpod

    hexpod http://heXpod.xyz

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    By using “fake kinematics” feature, while one actuator lacks stroke to accomplish the demanded pose, instead of blocking the last possible pose, you permit the others to move.

    Doing so, you are forcing your platform to reach the poses which are impossible to accomplish.

    This is inducing false cueing.

    It’s important to understand that “fake kinematics” is based ACCORDINGLY to the definition of your geometry.

    Once you decide to limit the course of your actuator (due to mechanical or driving issues you’re facing) you’re modifying the definition of your geometry.

    By limiting the arms revolution you are limiting your actuator stroke and the variations of its length.

    Following the min and max angular values you gave me, basically your actuator overall stroke is about 110mm. That’s not much.

    I’ve hard coded a both directions angular limiter on your demand first as an “out of reach” limiter than, on the bit output level which is supposed to work in a similar way as “fake kinematics”.

    As mentioned above, considering that you’re changing the definition of your platform you may not expect that the 3D model motion correspond to your hardware motion.
  6. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    I am aware of the false cues problem, but Dirty agrees with me, as does FlyPT to a lesser extent.

    My platform as it sits right now moves beautifully with Ian's BFF 6DOF. I want to get the same results with SimTools but with your software it is impossible. FlyPT looks to be my solution.
  7. hexpod

    hexpod http://heXpod.xyz

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    I don’t believe you tried the last version with output limitation man.

    But I am happy for you, you agree with yourself
  8. SeatTime

    SeatTime Well-Known Member

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    If you have too much slack between your motor and gearbox which has the feedback pot attached to it - then that is going to cause instability in the feedback loop. You have masked some of this with the gas shock which keeps a load against the gearbox, but likely it is still there in some instances. Its a hardware issue - No amount of software filters will fix this. I have seen this exact issue on a larger AC power rig in the past which he fixed 'mostly', as the rig became much heavier through the build. It is yet another reason why I went to ball screws, but if you had a encoder attached to the back of the motor shaft any small slack in the gearbox would be irrelevant.
    • Agree Agree x 1
  9. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    @SeatTime I know what you mean and I've got a little of that but not enough to matter I think. I'm not 100% sure but I think what I'm asking about here is a different issue.

    It's not back and forth... it's that the actuator has just a very little way to go to reach the setpoint and instead of slowly but steadily moving the last little way it's like the second hand of a clock. Start, stop, start, stop.... but always the same direction and each time it moves it moves at the same speed following that pattern until it reaches the setpoint. This happens when the setpoint is just a couple degrees from the current arm angle.

    @BlazinH I tried adding I to PID and it seemed like it did nothing, but I didn't try it specifically looking at this particular issue so I will do so thanks for the tip.
    Last edited: Jun 22, 2019
  10. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Update time! I'm making excellent progress and things are looking very promising!

    Problem 1: [SOLVED] I think. Experimental .LUA not yet tested.

    Problem 2: [SOLVED] I think. Experimental LUA not yet tested.

    Problem 3: [SOLVED] by extensive filter options in FlyPT software

    Problem 4: [GOOD ENOUGH] by using SimTools tuning center, plus limiting pitch axis travel to the lower value (forward vs. back) so that it is symmetrical, plus having my sim neutral position pitched up a bit.

    Problem 5: [PENDING] It seems the latency was being caused mostly by all the filters I was using in BFF. I don't know yet what the latency cost of the FlyPT filters will be but I'm optimistic.

    Problem A1: [SOLVED] by hydraulic damper/gas springs on my servo arms plus FlyPT filters to get a nice ramp on direction changes.
    ----
    Other recent developments/current blockers to my getting back in the (virtual) air:

    "Notchy" feeling for small motion sim movements looks to be dramatically improved by switching the Thanos AMC1280USB to 12bit ADC from 8bit. This is a prime example of something you would almost certainly never notice in a racing sim but in flight it drove me nuts. =) I am also looking at possible ways to decrease the slowest speed my sim will move via AMC and VFD settings etc. but I think it's acceptable now.

    AMC1280USB sensor feedback (10 bit analog ADC partnered with 12 bit analog ADC speed output) is wonky at the low end of the sensor feedback range. Approaching zero it seems to go into an exponential curve. This prevented me from managing a temporary workaround for the motion sim software bug that cropped up tonight. I have messaged Thanos about it, though it shouldn't affect me any longer after FlyPT publishes a bug fix. =)

    FlyPT is squashing a bug that (when combined with the Thanos AMC1280USB sensor weirdness) is preventing me from flying just yet, but he has been very responsive to messages and quick with the fixes. Also his new 2.0 software (FlyPT Mover) should have a first Beta available hopefully tomorrow. =D Very exciting stuff.

    FlyPT .LUA for DCS needs major updating and a no-Euler-angles revamp as well as "on ground" detection or landing gear telemetry channels. For now I will use SimTools for DCS telemetry with a new experimental .LUA I'm excited to test as soon as possible, but it's always nice to eliminate a software layer when possible so I'm hoping one of our community geniuses will get a new .LUA made for FlyPT DCS World direct mode. =)
    ----

    Other news: @pmvcda @Dirty and @hexpod are still hard at work making incredible improvements to the software side of our hobby. The new version of SimTools was released today (Thanks @yobuddy and others involved!) and in addition to the work from Yobuddy and other SimTools devs it includes some of the fruit of their debates and discussions. Tons of work is being done with filters that are a real game changer, but also they are discussing other major improvements and ideas. FlyPT also has an experiment in the works relative to VR motion compensation as well. No certainty that it will lead to anything useful but only time will tell.
  11. pmvcda

    pmvcda aka FlyPT

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    That last one...
    Don't expect to much, but I have some ideas.
  12. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Fantastic ideas you had indeed FlyPT. Things are nearly perfect now!

    OK guys, so I've got pretty much all my problems solved now which I'm thrilled about (more on that later) but every time you solve a problem you notice the next smaller one bothering you. =P

    There is one thing still giving me unpleasant jolts during my simulated flights, and for this one the main person who might be able to help is @Thanos , god of motion simulator interface hardware!

    I'm fairly certain this problem can only be solved by the AMC1280USB, the VFD's, or hardware I can't afford to upgrade.

    When a substantial heave movement comes in, all of the actuators must quickly move at the same time in the same direction. If there aren't any other significant cues at the same time, small defects in this motion are extremely easy to feel in the form of false cues, or a "bump".

    So when a heave motion begins, my servo arms do not all begin to move simultaneously. There are a couple that lag behind for an instant, and it's enough that instead of smoothly moving straight up from the start the initial moment of the cue contains various false cues in other directions. Please note, this is not a big problem, it is just the biggest little detail standing between my sim and perfect virtual flight. =)

    The question then, is how can I attempt to tune up the sim so that all actuators are as perfectly synchronized as possible in that one critical moment?

    I have tried adjust the PID on the individual actuators. I believe the worst offender (laziest servo) is #3. If I increase the PID (P) on #3 it doesn't cause that actuator to respond more quickly in that first moment. What it does instead is cause #3 to arrive at the setpoint sooner. As near as I can tell it has no affect whatsoever on that brief moment that the actuator should have started moving, but didn't.

    So can anyone tell me what adjustments to the VFD's or the AMC I should try playing with? Any other ideas?
  13. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Anybody have ideas for me on the above? @Thanos maybe? I need to get those synced up.
  14. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Hey guys, any of you love me enough to take a look at this and maybe tell someone who can barely operate a computer how to make it work? =P joystick.gif

    I know it's been done so it is possible.

    All I want to do is use this to make a SteamVR Overlay that displays my (Leap Motion and/or Vive Trackers) hands in 3D while playing any game. Just that, nothing else. Need it to work with. The reason is to simply help find switches in real sim cockpit while playing in VR.

    https://github.com/MilasBaumgarten/OVRLay This fork was updated just days ago, so it's just a matter of I don't know how to use it at all. (Below is another for you to look at if you are willing, that one is exactly what I need but very out of date)

    From what I can understand it's supposed to be super easy but I don't have the knowledge. If you can tell me where to read so I can learn to do it with just a few hours I will be happy to do that.

    I already installed Unity but can't figure out what to do with the files from there and there's no mention at all specifically of Leap Motion.

    There is also this other project, 100% exactly what I need but two years or more out of date. I don't know if I did it right but I tried putting it in Unity and got an error message probably because it's never been updated.

    https://medium.com/kainos-applied-innovation/vive-tracker-overlay-project-3ebc6a5e995b

    I think if someone can make an overlay and get it to work properly (and probably add a scaling feature) that some sim cockpit owners would be willing to pay a little bit for it. I know I would if it worked and would be maintained for future patches.
    Last edited: Jul 10, 2019 at 09:22
  15. hexpod

    hexpod http://heXpod.xyz

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    Does your VFD's have an auto tune feature ? If yes I would look in this direction instedad of putting different proportionals in the controller.
  16. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    I've done the auto tune multiple times, but I can do it again.

    Only thing is last time I was able to let it do auto tune with full rotations (with load) because the servo arms were only 100mm. Now I will have to do auto tune without movement, but that still sounds like a fairly good idea. If it makes it worse though, I don't think there is any easy way to go back so it's a little scary now that my sim is finally working nicely!