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Dirtys 6DOF, AASD Servos

Discussion in 'DIY Motion Simulator Projects' started by Dirty, Apr 28, 2020.

  1. Dirty

    Dirty Well-Known Member Gold Contributor

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    That's a good place to put those controllers. The space under the rig is useless for pretty much anything else anyways and the shorter cables are convenient.

    I am absolutely clueless about EMI though. Maybe @Thanos can voice an opinion. I'd find it at least plausible for the shorter cables to emmit less EMI.
    Initially it took quite a while to even realize that the problems I had were EMI related. Then I packed all cables in aluminum foil with lots of grounding everywhere. That gave a significant improvement. Now, in hindsight I know that multiple grounding points can cause ground loops, but still it was better than unshielded/ungrounded.

    If nothing else had helped, I would probably have drilled a hole in the wall and put the servo controllers in the adjacent room :)
  2. cfischer

    cfischer Active Member Gold Contributor

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  3. vectorcharlie

    vectorcharlie New Member

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    Thanks @cfischer I already went through all that thread and I am considering all your recommendations. So that would mean that maybe the enclosure is not needed... other than aesthetics.

    Thanks!
  4. Dirty

    Dirty Well-Known Member Gold Contributor

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    Thanks. Yes, I have also done most of those already and it is pretty much gone. I haven't tested it with the G2 though. I hope that it works just as well as the Index.

    Could you explain, why these should bring an improvement:
    Link1

    As far as I understood, I thought it was the high frequency current in the motor power lines that causes the EMI, but why should I worry about the 50Hz/240V supply from the mains? I would like to understand. Maybe I have a misconception there.

    Cheers,.... Dirty
    Last edited: Dec 30, 2020
  5. cfischer

    cfischer Active Member Gold Contributor

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    My understanding is that it stops anything from feeding back into the building, and then into your setup.
    This guy does a fantastic job of showing the effects.
    • Informative Informative x 2
  6. cfischer

    cfischer Active Member Gold Contributor

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    Another reason you could want the enclosure is to reduce the noise of the 10khz whine. Although it may be a lost cause. You can read what others have done or tried to do about blocking the sound.

    https://www.racedepartment.com/threads/simfeedback-ac-diy-motion-simulator-10khz-research.175829/
    https://www.racedepartment.com/threads/sfx-100-silent-driver-case-build.177437/
    • Like Like x 1
  7. Dirty

    Dirty Well-Known Member Gold Contributor

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    OH, thanks!! That is definitely a must-watch video. I would totally recommend that.
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  8. Builder

    Builder New Member

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    Hi Dirty,

    The Fusion drawing states that the upper Carrier, bottom Carrier and center part of the frame are made of steel. Is this correct or is this aluminum.
    BottomRIg.png

    Thanks,
    Builder.
  9. Dirty

    Dirty Well-Known Member Gold Contributor

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    No, that's aluminum, of course! :)

    Steel is just the default material in Fusion360, so whenever I forgot to apply a physical material it will end up being steel.

    Also, eventually I bolted the feet directly to the ground, because that Y-frame was not rigid enough. No matter how heavy you plan on making the base, it will almost certainly drift through the room over time.
    I didn't want to drill into the ground, because of the underfloor heating, so I glued a piece of wood to the floor and screwed into that.
    That is much cheaper and also more durable :thumbs
  10. Dirty

    Dirty Well-Known Member Gold Contributor

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    Oh, now that there actually are some death defying daredevils willing to follow along this build, maybe this can be helpful:

    Remember the "lip" I talked about?
    sacrificial layer.png

    This can be tricky to print directly as it is technically a 90° overhang. It will work and be fuctional, but it is not going to be a nice/clean edge.

    If you add this sacrificial layer to the part, then it will print this layer as a bridge. Then the next layers will built cleany on thop of those bridges. During slicing you will have to check that it actually sliced that layer to get the bridges.

    I am not sure if this feature is already in the F360 project. If it's not, this will help for a cleaner print.
    • Informative Informative x 1
    Last edited: Jan 14, 2021
  11. Dirty

    Dirty Well-Known Member Gold Contributor

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    And of course, you have to remove those bridges with a sharp tool of some sort :)
  12. vectorcharlie

    vectorcharlie New Member

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    Oh! That is what was that for! I thought it was a problem with the conversion between the F360 and STEP file. I ended up removing it and going for it. My printer handled it fine(ish) but is a good idea to leave it to be cleaner.

    Here the result print:

    upload_2021-1-12_23-19-2.png

    A little bit hairy and weird, but I already finished all the 6 heads :)

    And here already cleaned:
    upload_2021-1-12_23-19-41.png

    Thanks for the heads up thought!!

    Charlie
  13. vectorcharlie

    vectorcharlie New Member

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    Dirty,

    About the lubricant... This might be a silly question, but did you lubricated the nut/bearings and reassemble them? or just added the lubricant on the screw? What is the best way to apply it.

    Found multiple ways, including having a feeder to the nut, which is a bit too complicated of course.

    Re-assembling each nut is not a big deal, just a good "Zen" time putting each bearing in the circuits... I am sure there is better ways to do proper lubrication...... or maybe not!

    Thanks!

    Charlie
  14. Dirty

    Dirty Well-Known Member Gold Contributor

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    argh,... I was too late then :)

    Yeah, like I said, it will be functional :) And no one is gonna see the inside of the U-Joint.
  15. Dirty

    Dirty Well-Known Member Gold Contributor

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    Eventually I appplied lubricant to the ballscrew and let the ball nut absorb it during operation, but the correct way would be to pump it directly into the nut through a grease nipple.

    I am not particularly knowledgable on lubricants, but I played around with different products. Initially I started out somewhat naively just trying to minimise friction, so I thoroughly cleaned the ball screws, then applied a very thin oil. I tried Balistol Universal and GunTec. Both felt good initially. I had the feeling that the ballscrews were running "lighter"- with less force. But I read online that those lubricants are more metal conservants than actual lubricants. They have such a low viscosity that I feard they would not provide enough protection against abbrasion. Also, the low viscosity meant that the "CHRRRRRRRR" sound of the ball screws were very loud, because there was nothing that would attenuate the balls from vibrating in their tracks.

    Then, when I put the rig together I noticed that it had quite some slow speed stuttering. It was only noticeable on very slow speeds and I attributed it to the interaction between the servo control loop, low internal friction and a little too much "buffing mass" :) (german: "Schwabbelmasse")

    Long story short: I started using higher and higher viscosity lubricants and ended up with Klübersynth RA44-702. The slow speed stutttering improved A LOT, the noise is down significantly, and the lubrication properties are also much improved over simple Ballistol.

    Whatever you do, do not use WD40! :) That's more of a solvent than a lubricant.

    Cheers :)
    • Like Like x 1
  16. hooshang

    hooshang Active Member

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    My Motion Simulator:
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    great job!
    so smooth and realy quiet but i think it needs some more tuning on axis setup, it doesnt look real while landing i donno maybe wrong setup for Heave or sawy and surge!
  17. Dirty

    Dirty Well-Known Member Gold Contributor

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    It's a motion rig! :) It's not supposed to LOOK real! It's suppposed to FEEL real! :)

    Tbh, I was surprised, when I saw the video, how little of what goes on in the motion can actually be seen. Also be aware that looking from the outside will show you every movement, but when actually flying on the rig, many of those movements are below the threshold of perception.

    In a general sense, I can say that every acceleration is cued in the "right way", but often times not in the right measure. And when I say in the right measure, I mean that sometimes I'd want to feel more of this and less of that.
    However, making this distinction is not trivial. Think about it: How would you tell the algorithm what "this" and "that" even is?

    So far, I am still at a stage where I want to tune a single filter setup to cover the entire flight (and ground-) envelope. And there is still a lot to discover. I plan on playing around with different air/ground setups and signal compression methods some time soon.

    Cheers,...:)
    • Like Like x 1
  18. vectorcharlie

    vectorcharlie New Member

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    Thanks for the link Dirty! The Klubersynth seems like we should get, even if it costs almost like an entire actuator motor hehehe.

    I will then move to assemble the actuators as they are and apply lube later... I was smart enough to remove the nut on the first one I got right away, having tens of bearings in the floor. Lesson learned, but was wondering if it's something that needs to be done for lubing.
  19. Dirty

    Dirty Well-Known Member Gold Contributor

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    I think the high price tag of that grease comes from its temperature range (-50C to 130C or -75F to 260F), plastic compatibility and longevity. I am sure that there are other/cheaper products that deliver similar dampening properties.
    At the end of the day, it's not too bad, because you only need half a teaspoon to treat one actuator. That's about 1€ per treatment. Still a bit silly having to buy a 250€ can for a lubricant of which you will only ever use 1% :)
  20. Builder

    Builder New Member

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    Hi Dirty,

    Now that I arrived at the construction of the upperframe, I see that the mounting of the seat and footplate is not included in Fusion,

    I myself want to work towards a footplate where a pedal set can be mounted and a tableau where a steering wheel or flightyoke can be mounted to . I have considered mounting the Playseat Air force without undercarriage on the rig, whereby I immediately have the option of mounting different combinations of flight controls. However, I think the weight is not beneficial for the rig (24Kg complete)

    The construction for the base plate also remains. Since I am not a mechinical engineer I don't really have an idea how to solve this yet.
    Are you already further in this or do you have ideas in this direction on how to mount all this?

    Builder.