Horizon drift issue

Discussion in 'MōVI MR' started by Ian Howe, Jan 21, 2014.

  1. Ian Howe

    Ian Howe New Member

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    Hi Guys, our movi is suffering from horizon drift issues and I believe that the movi GPS is supposed to eliminate this problem. Please see the following link to a video showing the issues
    As you can see we are still struggling to get the unit tuned properly, balance is good on all axis. We have noticed that when connecting the unit to the configurator on landing sometimes the GPS shows no satellites yet our wookong will be showing 8 or 9. Any help will be much appreciated.
     
  2. Gary Haynes

    Gary Haynes Administrator
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    Ian what camera setup and where your gains?
     
  3. Ian Howe

    Ian Howe New Member

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    Pan 110 tilt 23 roll 25 and D800 with 25mm ziess
     
  4. Gary Haynes

    Gary Haynes Administrator
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    Ian the roll seems low, should easily be able to get to about double that number. I have a D800 setup and that one is at 56 on my rig. When you the adjustments did you suspend the copter with the gimbal below?
     
  5. Ian Howe

    Ian Howe New Member

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    We have been setting the rough stiffness in handheld then fitting it to the skyjib and fine tuning with it hanging below.
     
  6. Joe Lawry

    Joe Lawry Member

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    Im having a similar roll issue, i've reported it to freefly via email. They are looking over footage i've sent them

    FS100 in the air. I can point in 1 direction and the horizon is perfect. Then pan 180 degrees and the horizon is out. My roll stiffness is definitely in the 50 area.

    How are most people tuning the stiffness when it comes to multi work? I usually get my pilot to hold the movi by the quick release with no Octo on top and up the stiffness's until we get vibration, backing off to lose it. We then give the gimbal a bit of a move around to see if we find any motor vibrations anywhere else.

    Usually I find our pan motor needs to come down a fair bit as when I tilt the entire gimbal on an angle and hold it there.. (like fast forward flight) I get vibrations. I sometimes get vibrations when we yaw the machine while setting stiffness..
     
  7. Tabb Firchau

    Tabb Firchau Administrator
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    Ian, can you post a picture of your setup? I have a hunch you are getting some vibrations through to the gimbal which can upset things. Joe, I will take a look at the video right now and see if I can help

    Tabb
     
  8. Ian Howe

    Ian Howe New Member

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    Hi Tabb, we have the movi mounted to our droidworx quick release plate. This mounts onto the anti vibration mount on the aircraft. We have tried removing the anti vibration dampners but this doesn't make any difference. This is the only photo I have at the moment but will try and get one of it mounted to the aircraft.
     

    Attached Files:

  9. Joe Lawry

    Joe Lawry Member

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    Ours is mounted identically to Ians
     
  10. Ian Howe

    Ian Howe New Member

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    Hi Joe, have you got anywhere with the problem yet?
     
  11. Tim Joy

    Tim Joy Active Member

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    Is that the video transmitter on the back? If so, that is right next to the GPS antenna. Maybe it's swamping the gps signal? Have you checked in the software how many satellites you have with the V-Tx on?
     
  12. Joe Lawry

    Joe Lawry Member

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    Ian, No im still waiting on a response from freefly..

    Tim, yes good point, don't have a TX on the rear.. I have mine on one of the front MR legs.

    Did a job last week with Movi handheld on the back of a tracking vehicle shooting a drift car on a race track.. the Movi would not hold horizon when we hit the corners at 40-50mph. I'd be interested to hear your thoughts on this Tabb as I know you said in another thread that horizon should hold even when there is that sort of force applied. I believe it was a thread about shooting out of the door of a chopper.
     
  13. Paul Watt

    Paul Watt Member

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    I've noticed the exact same problem on both cars and helicopters. Horizon drifts every time even though the tablet says GPS locked
     
  14. Chris Jordan

    Chris Jordan Member

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    Ditto we also have H drift to the Left.
     
  15. Joe Lawry

    Joe Lawry Member

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    Still not response from Freefly. Will be asking direct questions at NAB.
     
  16. Tabb Firchau

    Tabb Firchau Administrator
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    Hey Joe, sorry I have probably been the delay in the response....Things have been a bit crazy around here with M5 launch.

    I need to look at the videos / pics you sent into our support team to make any substantive suggestions.

    Thanks
     
  17. Adam Paugh

    Adam Paugh Distributor

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    We witness something very similar the other day with our MoVI on a Cinestar8 HL. We spent the afternoon debugging the gimbal and then discovered that the issue was from resonant vibration that was been generated by the kopter. After some PID tuning the issue was eliminated.
    Ian--are you seeing GPS fix/Sats. during flight on the FF GUI? Also, what is the vibration dampening system you have the DW quick release mounted to?

    Greetings,
    Adam
     
  18. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Adam: Just to clarify, so there's vibration from the copter that's getting through to the MōVI and somehow causing a shift the gravity vector that the MōVI is sensing -- which in turn causes the MōVI to get a false sense of "down?"

    Thanks
    Andy.
     
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  19. Adam Paugh

    Adam Paugh Distributor

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    HI Andy

    That's about right. Alternatively one could adjust the 'output filter' and 'gyro filter' +1, +2 in the FF GUI. However, there is no better substitute to a properly tuned aerial/carrier system.

    Greetings,
    Adam
     
  20. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Thanks, Adam. What I'm taking from your observations is that the vibration isolators and the choice of rings is still pretty important to the performance of the MōVI -- which is entirely reasonable.

    Did you notice these resonant vibrations occurring when the copter was hovering, translating horizontally slowly, or fast? Or in certain combinations -- I'm just trying to get my head around what would cause the frameset to induce vibrations in the gimbal? Motor/props resonance, or even slipstream in the form of relative wind blowing through the copter/gimbal?

    Andy.
     

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