Pixhawk BAD ACCEL HEALTH APM 3.2 - collecting data - Discussions

A few users, myself included, appear to be having issues calibrating accels and/or arming when using APM 3.2 on a Pixhawk. I see posts here and there, but thought it may be best if those having the issue could all 'check in' to one post so that the developers can see how widespread the issue is and gather data.

My Pixhawk will arm occasionally, and will even fly successfully. Occasionally however it will not arm and I will receive the pre-arm error "Accels not healthy". A few days ago I was able to arm and fly thorugh one lipo, then after landing and swapping batteries I could not arm due to this reason. I have attached the logs from the successful flight, as well as the failed pre-arm logs, to this post.

As you can see from these images there is something amiss with IMU2. This is a snippit from the good flight, showing values for AccX on IMU1 and IMU2:

and here are the same values on the second attempt, pre-arm.

In the 3.2 release thread a few users had mentioned the issue and Randy advised to set the log_bitmask to "131070" so that it will log everything including the pre-arm checks. I encourage others having the issue to do the same and share the logs and experiences here so that we can find out what is going on here - is there a bad batch of Pixhawks in the wild that only now show the hardware errors due to something new in 3.2, or is there an issue in the APM software?

goodlog.bin

badlog.bin

Replies

- - - Developer
      
      Craig Elder > Mark Prince February 22, 2015 at 5:01pm
      
      the graphs are made using MAVGraph http://tridge.github.io/MAVProxy/mavtools.html
- Steven G > Kim Bitsch Lauridsen February 22, 2015 at 8:45am
  
  Did you try the method suggested above? That is, shorting the PM input to bleed off any charges which seem to affect IMU2. It has worked for a lot of people.
  - Kim Bitsch Lauridsen > Steven G February 22, 2015 at 10:29am
    
    Tried shorting the PM input. It seemed to work out. At least I got rid of the gyro warning 2 out of 5 times, but it is unfortunatily not consistent and safe for Flight.
    For information I use the attopilot 90A (using 6S LiPo) combined with a Castle BEC to feed the Pixhawk at it's normal powermodule input. At the servorailoutputs I allso have a BEC connected. maybe it has to be shortened breafly too before Powering up.
    - Artem > Kim Bitsch Lauridsen February 22, 2015 at 1:02pm
      
      This will work ONLY for IMU2 failure. Most likely you have IMU1 failure (read earlier comments) IMU1 is usually 3DR board, so easier to get a replacemwnt than trying to fix it.
  - Kim Bitsch Lauridsen > Steven G February 22, 2015 at 9:01am
    
    Thanks for the suggestion. I will see if it is posible to shorten the PM input a bit more.
    - John David Maharrey > Kim Bitsch Lauridsen February 22, 2015 at 10:06am
      
      Please do not "shorten" your PM input. Steven was telling you to SHORT your PM connector (touch the negative and positive together with something metal). Make sure that no batteries are connected to your system when you do this.
      - Kim Bitsch Lauridsen > John David Maharrey February 22, 2015 at 11:00am
        
        Thanks :-) Yes I got the meaning - but first after I wrote my ansver ;-)
        By the Way - I use attopilot 90 A combined with BEC
        image.jpg
- Steve Hayes > Kim Bitsch Lauridsen February 22, 2015 at 8:44am
  
  How long ago did you buy the Pixhawk and from who? If it was old stock from a dealer and manufactured between July 2014 and January 2015 it could be one with the known accel problem. My Pixhawk was manufactured in Oct 2014 and I got those same messages. 3DR replaced my Pixhawk under warranty and those messages are now gone. I know you can read the mfg date from the log files.
  - Kim Bitsch Lauridsen > Steve Hayes February 22, 2015 at 8:58am
    
    Thank you very much for the information :)
    I bought it at the 3DROBOTICS a month ago and it just came out of the box this weekend.
John David Maharrey February 19, 2015 at 2:51pm

Artem,

I just cycled my copter (3.2.1 having IMU2 failures at least every other boot) 10 times using your method and not one "bad accel health" warning! Thanks!!!

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