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Yaw drift issue

Discussion in 'Phantom 2 Vision + Discussion' started by Jeff48920, Apr 12, 2015.

  1. Jeff48920

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    After an exhausting three days of reviewing threads here and elsewhere and reviewing videos at Youtube, I have not seen anything addressing this problem. Although I have flown phantom 2 vision for about a year, I recently upgraded to the Phantom 2 Vision Plus. After about 20 flights, I had a small botched landing resulting in a 5 foot fall upside down, props shut down within 3-5 seconds. I broke one prop, but I pitched the lot and installed a complete new set which were balanced prior to installation. Since the incident I noticed that when I YAW LEFT, the aircraft moves rearward 10 to 15 feet and loses some altitude (3-5 feet), once I stop inputting Yaw, it attempts to stabilize over the GPS Home. When I YAW RIGHT the aircraft moves forward 10-15 feet and slightly right (3-5) feet. I have not noted any altitude change.
    I suspect the IMU may have been dislocated slightly resulting in these problem.
    I have done an advanced IMU reset and tried the "paper under the opposite side" fix. However, if I am attempting to correct the Left Yaw problem, it has no effect on the Right Yaw issue and recalibrating for the Right Yaw problem recreates the Left Yaw Problem.
    Any suggestions would be deeply appreciated.
     
  2. msinger

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    Did you try placing a level on top of the Naza unit?

    [​IMG]
     
  3. Jeff48920

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    I have not done that yet. I am a little anxious about cracking the case. I will do it though and report back. On the way to the hardware store now. As always, Thank you
     
  4. edonovanl

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    Sounds to me like you have inadvertently changed modes?
     
  5. dirkclod

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  6. Jeff48920

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    Edonovani: Nope mode was consistent
    dirkclod: thanks for the assist


    OK I cracked the case open and leveled the NAZA with a circular level. Unfortunately the level may have been too large (about 1 5/8" diameter) and did not sit perfectly on the FC. Other wires interfered with the process. After about an hour of mucking about with this less that perfect setup, I got the instrument to sit as level as I could and recalibrated using Advance IMU Cal. On the test flight it seemed to be somewhat better when inputting left Yaw but about the same as pre calibration when inputting right yaw.
    I am going to see if I can find a mini bubble level and retry later this week.
    If anyone can think of other problems that can cause this kind of erratic behavior or has alternate fixes I would be very appreciative.


    My 2+ is one of the newest ones and so here are some other notable things when I cracked the case:

    1. The ESC's were 2.1.
    2. It was impossible to tell if the motor wires were solid or stranded since absolutely no part of the wires were visible at the ESC. It seemed as if the insulation went all the way to the ESC and the solder was applied on the underside of the PC board.
    3. The GPS wire was under the shielding as in the mod suggested by forum members here. This however leaves a VERY short cable to connect or disconnect (I guess DJI listens but I needed forceps to reinsert the GPS cable for a positive connection).
    4. Finally the GPS connection was rock solid and did not exhibit any of the looseness others have complained about.
    FYI my Serial # is 6460******
     
  7. dirkclod

    dirkclod Moderator
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    Did you by chance when you had the top off take your GPS unit off and check to see if maybe the antenna on top of it was cracked ?
    You did say it hit on the top and have seen this happen before in here .
     
  8. Jeff48920

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    Dirkclod. I did not. But when I pull the lid to relevel with the 6mm diameter level I will certainly check the GPS antenna. Thanks.
     
  9. dirkclod

    dirkclod Moderator
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    In the link I gave you I did try all 3 ways to level and did find in my test the glass over the motor shafts to be as good as using the Naza unit to level and a whole lot easer than popping the top off . Good luck to ya and will be watching for your results !
     
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  10. Jeff48920

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    Thanks again.
    In reviewing YouTube videos for removing the shell, Simon and a couple of others talk about and show TWO sets of wires going from the main unit to the top shell (GPS and compass) that need to be disconnected or just left attached. When I opened my unit the only wire set going from the lower to the top was the GPS connector. Is the second wire set (compass) not there in the later model 2 pluses or did I just miss the disconnected wire?
     
  11. dirkclod

    dirkclod Moderator
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    You must have the V3 and it will only have one cable .Look at the compass on the leg of this one ,V3 compass and it connects to the board not the GPS puck . The other is the V3 GPS and only has 1 cable .
    new shell.JPG GPS.JPG
     
  12. Jeff48920

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    Dirk. Thank you very much. Yes I do have the V3. You saved me from cracking it open again before the new small level shows up. BTW I tried the glass across the motor shaft trick and the level is dead on. I am now convinced that either the IMU is off level inside or there is a problem with the GPS antenna. I will keep you all advised.
     
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  13. Jeff48920

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    Just finished leveling the aircraft and re-calibrating all flight controls and the IMU (advanced). The new bubble levels confirmed perfect level. Also checked the GPS which is in perfect condition. Props remained perfectly balanced.

    Unfortunately on the test flight it still drifts when Yaw is applied. Drift begins while Yaw is applied, is minimized by speeding the yaw, slows once controller is returned to the central position, and regains original GPS position within a short time thereafter. Worst drift is between 5 and 10 feet from original hover point.

    Vertical, pitch and roll are unaffected and no drift occurs. GPS hold is dead on, speed in all directions is correct. The aircraft stops on a dime once the input is centered except in yaw mode where it continues to drift before stabilizing and searching start point. All motors are very warm but not hot following the flight. All motors turn with the same amount of finger pressure applied. No weird sounds.
     
  14. danillll

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    Check your motors and make sure all 4 spins with the same resistance (when turned by hand) and all stop at the same time when disarmed.
    Had similar issue, one motor had a bent shaft, opened it and yaw was 95% fixed
     
  15. RoyVa

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    I had a similar issue. Couldn't figure it for a few flights. Then I went on eBay a bought a laser RPM meter for checking the motors and props. Found that one of my motors was 900 RPM less than the others at high throttle. Replace the ESC and Vola drift fixed. Unit stable and no side to side or forward drift. Easy $19.00 repair.
     
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  16. Ross

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    I get a bit of deviation during yaw, but only 4 or 5 feet. I had assumed this was normal and to be expected. This is on a new p2v+v3 too.
     
  17. David Bower

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    I have the same problem out of the box. Its fine in ATTI mode so don't think its my
    motors or compass. Mine shipped with firmware V3.09 but I upgraded to V3.12
    before my first flight - is there any way of going back?? Have popped the lid &
    checked the NAZAM module - its perfectly level & very secure. I note from other
    posts that people have used copper tape between this module & the GPS antenna
    but mine has a copper lined cladding factory installed. Should I try peeling this cladding
    back & checking the antenna is OK & if so what should I be looking for?
     
  18. Ross

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    I dont find It too much of a problem. I'm not going to mess around with stuff if I don't have to!
     
  19. Jeff48920

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    Thanks Danillll
    All motors turn with the same amount of pressure and all stop exactly together when disarmed by pulling the left stick full lock down.
     
  20. Jeff48920

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    Royva. Now that is my next purchase along with a laser thermometer to check motor temps. Thanks to all