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DJI S1000 crash - exponential drift

Discussion in 'Other DJI Multi-Rotors' started by gaucho, Sep 11, 2015.

  1. gaucho

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    Dear All, today I had a big crash with my DJI S1000. Could you help me to understand what it was wrong?
    The crash was due to a instable situation where i was unable to let it land at home.
    The S1000 went up normally (vertically), then it was unable to hold a position. it started to drift from its position and, leaving it without commands on sticks, its speed increases esponentially. Each time, I had to correct this exponential drift to let it return close to me. The drift direction was never the same. 2 times it started to spin around me in a circle with increasing diameter, tring to correct itself (with gps i suppose). Yesterday, in this situation, i was able to put it in hovering over me by playing on the sticks, and i successful landed. Today I was not so lucky and i had the crash, but the problem was the same, even if today i changed some parameters.

    This is my setup:
    -DJI S1000
    -DJI Lightbridge (to receive telemetery and video and to send commands)
    -GOPRO camera without gimbal
    -A2 flight controller

    Configuration details:
    -I calibrated the compass one month ago
    -I never sow this copter flying stable
    -These are the first tests with the S1000, my experiences are with phantom2 and ardupilot self built octocopter.
    -yesterday the gains were setted to 100% but i read on the dji manual that the gains on A2 used on S1000 shall be setted as follow: roll 120% pitch 120% yaw 120%
    -today i moved the gains as recommended on the DJI manual (120%)
    -yesterday the IMU position, in A2 configuration, was in the center of gravity, but the truth is that the IMU real position in S1000 is 10cm more backward than the center of gravity
    -Today i configured, on the A2 configuration software, the position of the IMU backward, to correspond to the real position of the IMU (around 10 cm backward)
    -Yesterday the position of the GPS, in A2 configuration, was in the center of gravity, but the truth is that the F
    GPS real position in S1000 is around 10cm higher than the center of gravity.
    -Today i configured, on the A2 configuration software, the position of the GPS, to be 10 centimeters higher than the center of gravity (in order to let it correspond to the real position of the GPS).

    Details about the flight:
    -i was flying in GPS mode
    -on the telemetry I had 11 satellites even during the flight.
    -the vibrations seemed low, because the gopro camera fixed on the top of the copter recorded a good video, just a little bit a jellow effect but this is normal because there was no gimbal.

    Any help to understand will be appreciated.
     
  2. packgreen49

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    I don't have a DJI, but every time I fly and/or land I do the calibration dance!
     
  3. dbooty

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    So if I read this right, it sounds as though you've only tried flying a couple of times and it's been all over the place both times yeah?

    To me it sounds as though your motors are spinning in the incorrect direction, or the motor layout (motor 1 front right counter clockwise direction) is incorreect.

    In these instances if the layout is incorrect the flight controller would be attempting to stabalise using more or less power to the motors its expecting to be in one location and the bird starts to go grazy because the motors are in the incorrect location or incorrect rotation and the flight controller hasn't a hope of regaining control.

    Check your motor layout, motor 1 front right and spin direction which is motor 1 counter clockwise spin direction
     
  4. gaucho

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    Motor sequence was correct cause i checked it.
    The copter correctly answers to sticks commands
    The problem was the ability to automatically hover
    Unfortunately i didn't tried atti mode, otherwise i could give more info
     
  5. Jeff48920

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    To me it is one of two possibilities
    1. Momentary loss of GPS lock in the A2 config
    2. Compass failure
     
  6. gaucho

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    I read about solar storm but i have strong doubts about their real influence.
    I assume that GPS was not well fixed to its support. So the gps was rotated by 30° respect to drone's head.
    So the compass integrated in the GPS was suppliing data with a 30° error.
    I think that this justifies what happened. Correct?
    Note that when i told to the drone to go forward (pitch) it moved to the correct direction, toward the head of the drone, without the 30° error.

    Like a stupid i didn't considered this important detail before.
     
  7. MultiRotR

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    2 things come to mind.

    1. Is the GPS arrow pointing forward?
    2. Is the IMU direction correct in A2 assistant?

    You very briefly mention it crashed. How bad is the damage? Can you post video from the GoPro?

    Dan