Bad AHRS - Pixhawk

Pixhawk, Arduplane 3.2.2.

Hello guys,

having a problem to make EKF to work. 
As soon as I put the EKF_ENABLE 1, the massage "BAD AHRS" appears on my Mission Planner screen. I couldn't find any similar topic on other forums so you're my last chance =)

I thought that it's might be a hardware problem, but both of my Pixhawks acts the same. The IMU pin legs connections on PCB are also look fine. All the initial calibration were made.

I also had an idea that it might be a wrong EKF_ or AHRS_ parameters problem, but I varied them without any successful result. 

Both IMU seems to work according to log file. But most of EKF'1-4' logs shows zeros. Since it was recorded indoor so I turned off the "AHRS_GPS_USE 0", but even with its on and outdoor the result is the same - "Bad AHRS"

I also noticed that INS_PRODUCT_ID turns to "0", saying that IMU is unknown, but not 5 as it should be for Pixhawk.

Please help, I spent the 2 days solving this problem without any results!

Here are the Parameters and Logs.

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ModeratorPermalink Reply by Graham Dyer on March 12, 2015 at 10:09pm

Starting to get this too, sometimes a reboot helps other times not. Did you ever solve this?

Permalink Reply by WEIWEI CHENG CHEN on March 13, 2015 at 5:31am

Hi, 

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.

Permalink Reply by Mike Mac on March 23, 2015 at 2:56pm
I have two Pixhawks with the same problem after upgrading to 3.2.3. It doesn’t happen all the time and clears when I cycle power. Has anyone done any investigation to see what’s doing on? Are the developers aware of the problem?


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Permalink Reply by Mike Mac on March 24, 2015 at 5:45am

Has anyone tried 3.3.0 beta to see if the bug has been fixed?

 


ModeratorPermalink Reply by Graham Dyer on March 24, 2015 at 6:02am

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.

Permalink Reply by Tamás L. Páll (Tom) on June 11, 2015 at 12:16pm

Hi Guys, 

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. 


ModeratorPermalink Reply by Graham Dyer on June 11, 2015 at 12:24pm

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.

Permalink Reply by Tamás L. Páll (Tom) on June 12, 2015 at 12:26am

Thanks Graham!

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. 


ModeratorPermalink Reply by Graham Dyer on June 12, 2015 at 12:52am

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?

Permalink Reply by Vesselin Goranov on January 12, 2016 at 6:41am

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.

Attachments:
Permalink Reply by Mike Mac on January 12, 2016 at 7:51am

Looks like 3.5.0 beta has all the fixes. Has anyone had any problems with the new firmware?

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100KMPermalink Reply by Hein du Plessis on February 3, 2016 at 4:49am

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...

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