Stability problems with M5 and Cinestar-8

Discussion in 'MōVI M5' started by Tuukka Ylonen, Aug 28, 2014.

  1. Tuukka Ylonen

    Tuukka Ylonen Member

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    Hi

    Despite very careful tuning and balancing I can't get rid of slight yaw/tilt oscillation on my Movi M5.

    My settings:

    - Cinestar-8 flat 8 with Kopterworx KW8 motors and Xoar 14x16 balanced props
    - 60A Maytech ESC´s and 2 x 5000mAh 5s lipos.
    - 3 red and 3 blue O-rings per dampener.
    - Toad in the hole
    - Canon EOS 5D III with Canon EF 40mm f/2.8 STM

    I have done the stiffness tuning numerous times with the copter suspended and I always get the same numbers. My stiffness values are pictured below along with my Wookong-M gain values.

    As you can see from the video, there is constant slight oscillation on the yaw and tilt axes (look at the edges of the image). It was completely calm when I did the video. On a windy day the result is much worse.

    I am clueless because my M10 with Red Epic works perfectly. No oscillation whatsoever.

    Has anybody any suggestions? Different O-rings, heavier lens, making the Cinestar into a X8?

    Opinions appreciated. Thanks!

     

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  2. Ozkan Erden

    Ozkan Erden Distributor

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    Tuuka,

    What happens if you lower the gains a bit more; lets says pan to 100, tilt to 15? Roll seems fine, but try that at 50 also.

    At low stiffness settings, you get rid off the oscillations but you have bad stabilization.

    When I first tried M5, I had terrible oscillation, what I did was to change the dampers with blue+black and lower tilt gain from 15 to 13. That solved all my problems.

    Another note, has it been always like this with you M5? Maybe you should check the cables, everything?

    And als, don't forget to send support ticket to Freefly.
     
  3. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    The Canon is a much lighter camera....you will definitely need to back off the stiffness settings.
    Assuming you have upgraded the firmware to 3.08, does the Autotune not help? Or are these the settings that Autotune gives you?

    Basic rules:
    1. If the camera is lighter, lower stiffness settings will probably be required.
    2. If the camera to MōVI mechanical coupling (or any mechanical coupling anywhere on the gimbal) is loose, then the likelihood is that it will oscillate/vibrate (the control mechanism starts to chase its own tail and that causes the oscillation).

    Andy.
     
  4. Tuukka Ylonen

    Tuukka Ylonen Member

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    I got these stiffness values by upping the stiffness values until oscillation occurred and then I went 10 units down from those values.
    So I got these values doing the tuning by the book.

    I have firmware 3.08 and I did try the auto tune, but the result was worse than this.The stabilisation was not good at all. See the linked video of results with auto tune. The stiffness values were somewhat lower with autotune.

    I also suspected that there is something mechanically loose on the gimbal and went through all the screws and tightened them so they should be tight. Also the coupling between camera and gimbal should be tight.

     
  5. Ozkan Erden

    Ozkan Erden Distributor

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    Tuuka, something is really wrong with the gimbal. I would recommend you to get support from Freefly directly.
     
  6. Tuukka Ylonen

    Tuukka Ylonen Member

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    Yep, sent them an email with links to videos and to this thread.
     
  7. Jason Smoker

    Jason Smoker Active Member

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    Just so you know Quadrocopter sent me my heavylift kit it has all blue o-rings. Dont know how much different it makes
     
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  8. Tuukka Ylonen

    Tuukka Ylonen Member

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    OK this is getting quite strange. Today I mounted my problematic M5 into my X8 which flies solid like a rock.

    The result: When flying forward, the yaw stability is rubbish. When flying backwards (!) it improves a lot.

    The only reason I can think of is the fact that I have mounted my Teradek Clip into the front right LG leg. Maybe this causes too much wind resistance and thus yaw instability. Will test tomorrow Clip mounted into the rear LG leg.

    Did try tampering with the Expert settings, but to no avail.

     

    Attached Files:

  9. Steve Maller

    Steve Maller UAV Grief Counselor

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    I really doubt at the speeds your going in the video above that wind resistance plays into this. If it was me, I'd check a few things:
    1. make sure all your cables on the MōVI have enough slack in all degrees of movement
    2. make sure all your vibration isolators are working properly and not "bottoming out"
    3. re-check pan balance
    4. are you using a lens hood? if so, remove it and see if that makes a difference. ask me how I know that. ;)
    5. lastly, it's often illuminating to hard-mount a GoPro onto one of the copter's booms with a clear view of the gimbal to see if there's anything going on that you can't see from the ground (like a cable binding or flapping around)
     
  10. MIke Magee

    MIke Magee Active Member

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    Steve, OK, how do you know that? At low speed, what issues did the lens hood introduce? I'm seeing a funny pan issue.


     
  11. Steve Maller

    Steve Maller UAV Grief Counselor

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    Easy...I ran a test with the hood on and off, and I definitely saw a difference in stability when moving forward at 10mph or more. The camera was more aerodynamic without the hood. Anyway, people kinda like lens flare these days. Go figure. ;-)
     
  12. Adam Paugh

    Adam Paugh Distributor

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    Hello Tuukka,

    Do you have adequate clamping pressure on the TITH quick release. I struggled with similar pan axis instability and found that giving the adjustment screw another quarter turn on the TITH provided the fix.

    Greetings,
    Adam
     
  13. Tuukka Ylonen

    Tuukka Ylonen Member

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    Well I think it was not the lens hood or TITH clamping pressure. Seems that the M5 just does not like light lenses at least in the case of EOS 5D Mark III.

    I changed the lens from very light EF 40mm f/2.8 and light EF 24mm f/2.8 into a heavyish EF 24-70mm f/2.8 II, ran auto tune and voilá!
    The stability got a lot better. Although the weather was calm, the video pretty much proofs my theory.

    Stiffness values with autotune in the video are:

    pan: 169
    roll: 74
    tilt: 48

     
  14. Steve Maller

    Steve Maller UAV Grief Counselor

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    I would guess you might need to adjust your vibe isolator rings if that's the case. The heavier lens probably set the rings at a good equilibrium, whereas they might be too stiff for the light lenses.
     
  15. Steve Maller

    Steve Maller UAV Grief Counselor

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    I noticed in your photo that you using quick release rails in addition to the toad in the hole. You might want to consider using one or the other, but not both.
     
  16. Tuukka Ylonen

    Tuukka Ylonen Member

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    Steve: I am using both because my Vulcan is an X8 and the video above was done with Vulcan. And it worked good.
    I get less props in the picture by using both.

    I find it very hard to believe that the issue would have something to do with vibration dampeners. Based on my tests O-rings only affect the probability to have jello. I tried a number of different O-ring combos with the lighter lenses, all with equally poor (unstable) results.

    Most of the O-ring tests were made with a stock Cinestar-8. With a stock X-plate and Toad in the hole system.

    I tried full red, full blue, 3red/3blue, 3blue/3black and 5 blue/one red per dampener. All were unstable. Full red had some jello in the picture, the other had none and I did not see really any difference in the stability of the footage with different jello-free O-ring combos.

    I am finalising my Cinestar conversion into a X8 and will be testing with full blue O-rings and a heavy lens shortly. The Cinestar has the stock X-plate/Toad in the hole solution. Will see what happens.
     
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  17. Zaid Al-Obaidi

    Zaid Al-Obaidi New Member

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    Tuukka not wishing to hijack your thread, I am having a similar problem to you with the Movi5 I have been in touch with the support team for some time trying to resolve the issue, went through the process of balancing etc.. all the values are great on the ground I even had to add around 440g to the rig and the best values I achieved in Pan, Roll and Tilt stiffness were 110/44/20. the motor values once the gimbal is mounted on the airframe are between -1 , 0 , -2.

    The Support team said it's vibration from the rig, but I am 100% certain its not, furthermore I have installed a secondary vibration plate to mount the gimbal too but still not having much luck with it.
    I have been waiting to hear back from the support team for a week as they had no member in from the flying team.
    I have been trying to sort this state of the art gimbal for over a month now I am beginning to loose complete faith in the investment that had lost half of its value in just over 4 weeks! !!

    Steve, if I may ask why the quick release system might be an issue ? That is what I have and I am beginning to wonder as I have tried everything, the only common denominator is the quick release plate !!
    here is a sample footage from todays's testing, apologies in advance I forgot to mute the sound !!

    Password:
    123456


    The airframe I am flying is a Vulcan X8
    2 x anti vibration plates
    GH4 with 12/35 lens

    What are the typical values you guys are flying your Movi 5 with ?
    Weight of gimbal and camera?


    Thanks
     
  18. Steve Maller

    Steve Maller UAV Grief Counselor

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    My comments about the quick release plate come from basic physics. The more hardware involved at a stress point (like the gimbal attachment), the more possibility for uncontrolled movements. The vibration isolators are designed to be the only thing that flexes in the Cinestar-MōVI union, and if there are other things (like mounts on another quick-release, or just flex in other components), it could cause oscillations, instability, or general weakness.
     
  19. Gary Haynes

    Gary Haynes Administrator
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    Zaid can you post some pictures of your rig and the way you have the gimbal attached?
     
  20. Zaid Al-Obaidi

    Zaid Al-Obaidi New Member

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    Thanks for your reply guys

    Gary, as requested the mounting of the Movi 5

    Kind Regards

    Zaid
     

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