Stick center/drift problem

2.0.19 quad X

The quad flies ok in stable mode when I trim the sticks, it hovers perfectly for a while. But after short time, the center of the sticks is not neutral anymore. After a while, max stick input is almost not enough to keep the quad straight. If I land and try again it sometimes fixes itself, but after a few turns the sticks neutral point is far off again. 

 

How can I fix this?

 

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Replies

  • Developer

    Some people don't seem to have this problem, but if you land and wait 30+ seconds and have full control again it's the DCM's drift compensation. Doug is working on a new concept so that we can compensate drift dynamically. We'll be able to slow the adjustments during flight maneuvers and speed it up when the sticks are in neutral. Hopefully this will solve the issue!

    Jason

  • Had Another go today.

    Disabled compass,reloaded the code and still the same.

    Starts off hovering in one spot,than after a bit of maneuvering ,

    hands off the controls and the quad still moves around.

    here are the accell and gyro offsets,How do they look?

     

    Gyro offsets  -35.00, -45.01, -68.91

    Accel Offset  14.37, -19.07, 18.61

     

    Tried changing the imax from 50 to 100 on both pitch and roll ,which seemed

    to help.

    Will try more testing tomorrow???

  • I enabled RAW logging, flew around a bit until I almost could not control the quad anymore. The logfiles are available here:  http://dl.dropbox.com/u/19126845/ArduCopter%202.0.20-logs1.zip

  • Hi Sebastian,

     

    I have tried to "level" the quad with the back raised by 2cm to offset a potential imbalance and to troubleshoot this. but it does not seem to make a difference on backwards drift.

     

    Here the IMU settings:

    test] IMU
    IMU
    ----------------------------------------
    Gyro offsets: 3.31, -10.05, 9.49
    Accel offsets: -3.11, 9.82, 31.58


    Init Gyro**********IMU
    ----------------------------------------
    Gyro offsets: 3.87, -10.07, 9.78
    Accel offsets: -3.11, 9.82, 31.58


  • Wouldn't it interact with other modes like SIMPLE mode for example, where the front is not always the quad heading ?
  • while at the topic. In STABILIZE mode I do see mine permanently drift backwards without stick input at a pretty fast rate if i don't give it forward stick to counteract. as RC trim is not an option I was wondering what affects this and how to troubleshoot ?

     

    I leveled it very carefully in setup as well and kept it super steady during startup calibration. what else could effect that behavior? It also persists between erases and factory resets and shows the same "backwards" drift consistently every time.

     

    Otherwise 2.0.20 works great now!

     

    Would be grateful for any hints.

     

     

  • This problem sounds like a gyro zero/temp problem to me. IMU chips out there in the sun and wind on most copters. I looked at the shematic and found a temperature analog channel. I thout it had temp comp, but wasn't sure. I then looked at the IMU code and I'm not sure but I think there might bee a problem with the <_sensor_compensation(uint8_t channel, int temperature)>,  and specificaly this

    <const float   AP_IMU_Oilpan::_gyro_temp_curve[3][3] = {
        {1658,0,0},            // Values to use if no temp compensation data available
        {1658,0,0},            // Based on average values for 20 sample boards
        {1658,0,0}
    };>

    Maybe I just don't get it ?  Shouldn't those zeros be some values?

  • Developer

    I've never seen the issue myself. I assume it's a hardware calibration issue. If the quad will fly normally after 30 seconds on the ground, it's a Gyro drift issue. How to solve the problem withe the DCM is not my thing. Pirates uses the same or similar DCM so it should be evident in both.

    Try calibrating with Pirates code, then write down the Gyro and Accel offset values. Then do the same with AC2 and compare them here on the blog.

    Also, please make sure your quad is really, really still at startup to get a good calibration.

  • Moderator

    Hi,

    Post a log with RAW logging enabled. Things have been hectic here, but I also need to get a good log of this, as it happens in my case, too. I'd say to add the log to my issue that was open, but it's closed now. Open a new issue at http://code.google.com/p/arducopter/issues/list or just post it here.

  • 3D Robotics
    Are you using a magnetometer and if so, is it enabled?

    Also, please update to the latest code via the Mission Planner. We're now at 2.0.20.
This reply was deleted.

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