Starting to get this too, sometimes a reboot helps other times not. Did you ever solve this?
This week I'm working to solve the BAD AHRS problem. I had the same problen than you.
Finally, i solved the problem using the Ardupilot V3.1.1 version.
Have a nice day.
Has anyone tried 3.3.0 beta to see if the bug has been fixed?
We started getting this and a reboot usually sorted it out however a 6 way gyro/accel re-calibration seems to have fixed it properly.
I had the same problem with my Y6 copter AC3.2.1 and now with the AP3.3.0.
I tried 2 different GPS modules, redone the accel calibration, compass calibration. if I wait for 10+ minutes the message goes away, I also tried SKIP_GYRO_CAL, NUT NO LUCK!
Can anybody shed some light on why this is happening? and how to correct it? could an optical flow system correct it?
I would happily fall back to 3.1.1 nut as I understand the terrain following is not in that version.
Nothing to do with terrain - AHRS is Attitude and Heading Reference System. The only way I've solved the message so far is to keep the Pixhawk/airframe absolutely still while rebooting and/or re-do accel/imu calibration.
Every time I do the calibration my horizon ends up approximately 30deg tilted. If I reboot i get "bad AHRS".
Does "Preflight calibration" include gyro/IMU calibration?
I was asking if 3.1.1 has terrain following already in it as a separate question. I could have a forestry job around some hills, but without terrain follow capability I cannot do it.
Preflight calibration doesn't include IMU calibration. Are you doing the 6 sided IMU calibration?
Sorry misunderstood the terrain question. I can't remember if 3.1.1 is using terrain following, we're using 3.2.1 which is pretty solid and proven so far. I have an issue with APv3.3 so not using that ATM. Maybe a complete reset (flash other firmware) would fix that 30° roll error?
I found relation between power-up time and the "Bad AHRS" message.
Each time, on power up, the Alt readings on the Mission Planner Tuning window shows few centimeters variation.
After about 8 minutes, still on the ground, copter not armed, the Alt variation becomes about 5 meters. Same effect I have on both tested Pixhawk controllers.
The picture is enclosed.
Looks like 3.5.0 beta has all the fixes. Has anyone had any problems with the new firmware?
Nope, 3.5 doesn't fix the problem.
I've been through 4 pixhawks and 3 GPS units, they all show the same issue. Recalibration doesn't help permanently, either.
The problem only manifests once the GPS has a 3D fix. I've been going around in circles because of this - no I know how to test properly.
Along with the AHRS error, one can see the artificial horizon moving slightly, even if the plane is stationary.
Why are we the only seeing the problem? I'm quite stumped...