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Bad AHRS - Pixhawk

Posted by Bartek Sad on February 17, 2015 at 5:58am
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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Tags: ahrs, bad, imu, pixhawk
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Replies

  • Vesselin Goranov January 12, 2016 at 5:41am

    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.

    8_minutes_AHRSerr.jpg

  • Tamás L. Páll (Tom) 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. 

    • Moderator
      Graham Dyer > Tamás L. Páll (Tom) 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.

      • Tamás L. Páll (Tom) > Graham Dyer 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. 

        • Moderator
          Graham Dyer > Tamás L. Páll (Tom) 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?

  • Mike Mac March 24, 2015 at 5:45am

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

     

    • Moderator
      Graham Dyer > Mike Mac 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.

  • Mike Mac 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?


    .
  • WEIWEI CHENG CHEN 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.

  • Moderator
    Graham Dyer March 12, 2015 at 10:09pm

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

This reply was deleted.

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