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Bad compass health - a neverending story?

apm

(.) #1

Hi everyone,

I have been flying my quad with APM2.5.2 (internal compass cut) and Arducopter 3.1.5 for many years without any problems all over the world

For some months, I often get a “bad compass health” message and cannot arm. Not always but almost always. So I bought a new compass and GPS combo (M8N+compass)

First thing I noticed that orientation with is incorrect. At roll 180°, all directions seem to be correct. So I did two flights. They worked but in LOITER it was flying in a cicle even at 13 sats and HDop of 2 . At the third flight I got “bad compass health” again and I could not arm.

So I flashed the newest firmware possible (v3.2.1) but still “bad compass health”. I attached some screenshots from the last flight with new GPS and compass without “bad compass health”.

What could be the problem? Compass is calibrated and orientation seem to be correct.

I know there are already some threads about this topic and APM hardware is no longer supported but maybe there is an easy way to fix it.

Edit: Today I tried another flight and there was no Bad Compass Health. Also Loiter worked fine! Is it possible that it is dependent on the temperature?
2018-11-08%20Auto-analysis



(.) #2

And it goes on…
Last week I did a perfect flight without any problems after I added mu-metal just below the compass/GPS-unit.

Today I tried another flight but Loiter was not working. The copter always started to drift away by accelerating its speed in Loiter mode. During decend, first time I got an OSD message “DCM Bad heading”.

I did compass calibration for a dozen of times and the distance compass-ardupilot is already 7cm (was just 2cm with old compass) and the compass is shilded by mu-metal.

The only thing I haven’t tried is Compassmot, I will try that next.
http://ardupilot.org/copter/docs/common-compass-setup-advanced.html#compassmot-compensation-for-interference-from-the-power-wires-escs-and-motors
It seems that I am not the only one.



(vosair ) #3

Compassmot helped a great deal for me. They are also introducing in-flight calibration where you fly in a non-gps hold mode for a minute and it calibrates in real time.