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How to fix yaw drift?

Discussion in 'Phantom 2 Vision Discussion' started by SlackerATX, Mar 15, 2014.

  1. SlackerATX

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    I've had my pv2 for a couple of weeks. After upgrading the firmware switching to FCC mode and switching out the props there is a noticeable difference in the yaw drift. I've had a couple hard landings as well. The phantom still hovers nicely with little or no movement. When I yaw CW or CCW the phantom drifts 10 to 15 feet from its position. Then slowly moves back to it's starting position. (Assume that's the gps mode working) I didn't notice any drift before the transmitter calibration and firmware upgrade.

    I've tried adjusting the yaw gain via the assistant software up to 150 and down to 100 and all the 10% increments in between from the default 120. No setting in that range seems to make any difference. Is it possible the new firmware has different default config values that would have negatively yaw drift? Do the gain settings even affect this?

    I found a pic explaining what my phantom does that the problem. I assume this is yaw drift? Only difference is I don't see a significant altitude change and after it moves back to starting position.

    [​IMG]

    I'd really appreciate any help.
     
  2. SlackerATX

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    When I was testing this and making adjustments I was in my neighborhood doing 1 min up and down flights. After setting to defaults and going to an open park I had the same yaw drift. 10 to 15 min in the problem went away. I could yaw on a dime. I'm starting to think that maybe the motors need to warm up or something. No clue really.
     
  3. flight-of-eye

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    Possible gps interference causing miss flight. I know that if I am over my driveway I get more drift then I do over an open fields at lower levels. Think it has to do with the steel in the concrete. I also find that. When I fly over grape vineyards at low levels I get weird flight patterns. Vineyards are rows of steel t-bars. Once I get some altitude this seems to diminish.
     
  4. flyNfrank

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    Calibrate the compass.

    ANY time you get your compass around ANY thing metal, you will need to calibrate the compass. Doesn't matter what it is metal either. Like your vehicle keys, Watch, metal bracket from controller, screwdriver, ect ect. When you do calibrate it stay away from anything metal. Like re-barb in sidewalk or driveway, under ground drain, your vehicle.....

    The compass is extra sensitive. One other thing you do need to know is, You will need to calibrate the compass anytime you go to a new place and fly. I bought a lazy susan so that I don't have to do it on the ground. Some pilots calibrate theirs by holding it. I don't care for that method, but it's whatever works best for you.

    Btw, I had just come in from flying and I had to stop and calibrate cause it was doing the same thing you described with the circling. I hope this helps...
     
  5. SlackerATX

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    Thanks. I'll try that.

    Are you saying that anytime the compass come within a couple feet of any metal the calibration is broken? So anytime I put everything in its case the metal on the controller breaks the calibration? Why does the metal on the phantom not break the calibration?
     
  6. flyNfrank

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    Well I'm saying it could happen. If the controller metal bracket gets near the compass, there is a very good chance you can expect it will need calibrated.1
     
  7. SlackerATX

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    I'ts been a couple weeks and I'm still having this problem. This is what I've done since.

    1)Replace the shell, removed everything and put it in a new shell.
    2)Verified the compass is calibrated and mod values in assistant are sane. (about 1250)
    3)Took one motor apart that seems a littler grinder than the rest. Oiled it and it seems like the rest now.
    4)Verified good GPS with 14 satellites.
    5)Perfectly balanced all 4 props. (I mean perfect)
    6)Verified up close that all 4 props are level while running.

    I've thought about doing a few more things, but not sure how.

    1)Play with the yaw gain in assistant some more. I've tried this, but it doesn't seem to change anything. Should I trying increasing up or down?
    2)Test the motors for RPS?
    3)Test/replace ESC?

    I've bought 4 new motors and plan on replacing them tomorrow but I don't have much hope that will fix it. Has anyone had any success fixing this?
     
  8. SlackerATX

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    On a scale from 1-10 how normal is this?
    [youtube]http://www.youtube.com/watch?v=SLmdHNiOF3I[/youtube]
     
  9. tizzl10

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    Mine does the same thing.
     
  10. Pull_Up

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    What happens if you yaw in the hover slowly, i.e. in a way more likely to happen whilst filming? If it's fine then and only moves during very fast pirouettes I'd be tempted not to worry about it unless you had a specific reason for it needing to be solid on the spot during fast spins. FWIW mines does something similar with full yaw input, although the drift is a little less than yours.
     
  11. pault

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    I have not found the compass needs calibration every time it is put near metal. If i put my P2V on he roof of my car after a flight I sometimes get the 'compass needs calibration' message on the app but I just ignore it and power off. Next time I fly all seems normal.
     
  12. rnrnrn

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    I did notice this kind of excessive drift too - but I can't really put any time frame on this, I can't figure out when it started.

    One thing though - I haven't had a chance to fly in quite conditions recently - all recent flights were with significant wind (and I do presume you had quite a bit too from the video). Maybe that causes this excessive drift... I'm waiting for calm conditions to double check this.

    Cheers!
     
  13. Shrimpfarmer

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    Mine is the same. The slower you yaw the less it should do that. My take is that the phantom is slow to calculate the necessary inputs required to maintain position whenever the wind is constantly changing directions over the blades as it will in a yaw. I wonder if it would be as bad in totally calm conditions. If it is then that theory is blown out of the water.

    The only option open to you is to counteract that effect through flying skills.
     
  14. Shrimpfarmer

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    I also have not had any problems with the compass. Its only ever been calibrated once and I also plop it on my car whenever I need to make space in the boot.
     
  15. RCRookie

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    I would retest this in calm conditions as well. It appears to be adjusting for the winds effect as much as yaw.
     
  16. SlackerATX

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    I was able to help this immensely by adjusting the gains.

    Basic Gain:
    Pitch/Roll 165%, Yaw 185%, Vertical 125%
    Attitude Gain: (no change from default)
    Pitch/Roll 125%

    Before I was getting this with or without wind regardless of how fast the yaw was. In general the drift I experienced should not be seen in a quality quad copter, at least not to the extent I experienced it.

    Here is another good video showing he problem much more clearly.

    [youtube]http://www.youtube.com/watch?v=RFASeuJlcO0[/youtube]

    In general the phantom is much more stable and predictable after adjusting the gains.
     
  17. SlackerATX

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    Here is some video after adjusting my gains. I went from 15-20 ft yaw radius to about 1-3 ft.

    [youtube]http://www.youtube.com/watch?v=W2JUfxFinPQ[/youtube]
     
  18. RCRookie

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  19. SlackerATX

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    I specifically asked in that thread and the OP said it doesn't affect his ability to yaw in place. I am also able to fly straight, so I think the two things are somewhat unrelated.