I have a weird issue on only one of my APM2.5 boards where in alt hold, the copter will climb when I move forwards, and drop when I move backwards. This climb/drop happens as soon as input is given.
Is it possible that I have a bad board? I am having trouble interpreting the logs to tell what exactly is going on. I have a dataflash log with IMU logs enabled which shows the issue on a short flight today.
Running 3.1 RC5, but this has happened with the last few versions I have run.
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So this is caused by having the accelerometer calibration incorrect. So the parameters involved would be:
INS_ACCOFFS_X 0.135
INS_ACCOFFS_Y 0.26
INS_ACCOFFS_Z 0.53
INS_ACCSCAL_X 1.007
INS_ACCSCAL_Y 0.993
INS_ACCSCAL_Z 0.979
In particular it's probably the INS_ACCOFFS_Y value and it may be changing over time. I suspect if you re-do just the accelerometer calibration it'll be fine for a while. I have no idea why it would be changing over time though but doesn't sound good!
Ok, yeah I have tried giving this copter a complete erase/reset and setting up from scratch, and it starts off flying OK, but then eventually this problem returns intermittently after a few flights, and eventually happens all the time. If I swap this particular APM out with another I have, it works perfectly.
You appear to have the APM tilted slightly nose down during flight. I would have to spend an hour or so to go through the code ot fully understand the implications of the way we do our leveling so I can't give you a precise answer about how to fix this.
I would suggest redoing your accelerometer calibration and making sure your APM is mounted horizontal and your propellers are all horizontal.
It looks like there's a bad Y/Z accel reading in the logs at line 1998 which I needed to trim out before the graphs would display correctly, but I don't know how this is related. I also had to trim out the last IMU line which had very high values.