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APM 3.2 QUADCOPTER Err: EKF_CHECK-2 / Err: FAILSAFE_ EKF-1

Posted by Gonzalo Garat on December 15, 2014 at 4:26am

Hi all,

I'm attaching my log from our last flight as our little quad went completly bonkers before it crashed.

Short after takeoff it went completly out of control, no response at all from RC or Telemetry and then crashed near a pond (thank god).

But the mistery was about to begin when we started reviewing the log and found out that the trigger was the failsafe error  Err: EKF_CHECK-2 / Err: FAILSAFE_ EKF-1. 

In understand these two were recently added to APM, but this ain't the first time I see this sort of thing happening.

I'm attaching my log in hopes for some guidance.

Thank you all!

2014-12-14 11-10-14.log

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Tags: ekf, failsafe
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Replies

  • Andy Piper May 10, 2015 at 5:04am

    3702942797?profile=original3702942935?profile=originalOk interesting. You can see the rctimer mounting here. It has a few degrees of forward lean - would that make a difference? Also the pole is less stiff than the 3DR one so that it will vibrate if provoked - would that make a difference? The alignment looks ok to me (top-view photo) how would I get it any closer?

    Question about the code - this generally occurs when very severe yaw values are requested - i.e. sudden change in yaw. This seems worse in auto as in auto the mission will turn as quickly as possible (relative to my thumbs). But you can also see that the yaw error shoots up to one almost immediately in that log, but not elsewhere. Why would this be? Is the IMU struggling to keep up with severe yaw? Will the increase in sensitivity in 3.3 help? I have had similar experiences all along - yaw error will be fine and then suddenly go ballistic, there doesn't seem any consistency to it other than the severity of the yaw that is initiated.

  • Andy Piper May 10, 2015 at 2:14am

    Thanks Paul, this is really helpful!

    I had picked up (4) as a possible cause as I had experienced toilet bowling later on in the day and google indicated that auto dec could be an issue. Could (4) explain everything? Why is auto dec wrong, could it be something to do with my fairly northern latitude? I have manually entered it now and will see what the results are like.

    Because I've had such bad compass problems (faulty 3DR compass) I do the compass dance all the time inside and outside and compare the offsets. They are always pretty consistent. How close would you expect them to be to be right? e.g. (-102, 7, -28) vs (-121, 1 -21). Is it worth switching on in-flight compass learning?

    It was fairly windy that day and issues (TBE in particular) showed up hedaing into the wind. Does that have any bearing?

  • Andy Piper May 9, 2015 at 2:20am

    Thanks! This is really helpful but now I am really confused. I am trying to interpret the attached log. You can see that ErrYaw spikes to 1 and likewise EKF4->SMX/SMY but I am really struggling to understand why. On the face of it it is the compass. You can see that MagY jumps at the times the error jumps and similarly the yaw jumps, but there is no noticeable interference against the throttle and the compass is mounted 20cm above the PDB. I have also seen similar effects with a different compass. I'm guessing you would expect some yaw error when the yaw changes quickly (this is an auto mission), but the big spike occurs sometime after a big yaw change, pretty much coincident with the MAG values going negative.

    Are spikes in SMX/SMY expected as yaw changes quickly or should they not spike this much? I suppose you could argue that EKF is doing a lot better here than DCM. The EKF->SMY spike only goes above 0.5 briefly and only to 0.56. The DCM error takes a lot longer to settle down.

    Should I be worried?

  • Andy Piper May 8, 2015 at 12:02am

    Thanks Paul, for the insightful analysis! Is there a write-up anywhere of how to analyze EKF log data?

    BTW this illustrates what I have been thinking the past week - namely that ErrYaw is misnamed and misleading.

    I dunno what would be better - ErrNav? ErrVel?

  • Checkers May 7, 2015 at 1:39pm

    I have just checked my logs and up until the point of the error (at which point they skyrocket)  I have very little vibration all of which is well within the bands that the wiki says is acceptable. The peak in vibrations seems to coincide with the loss of gps and after the crash all levels revert to normal apart from acc z which has flipped from -10 to 10. Weird. 

    77.BIN

  • Checkers May 7, 2015 at 12:08am

    I have had a same / similar issue but unfortunately I am on my mobile so can't post logs but they are attached to a post I made a few days ago if they are needed. (Gps loss on loiter and then...) 

    Edit: I am also on a pixhawk 

    • This reply was deleted.
      • Andy Piper May 7, 2015 at 4:02am

        Don't think there is any vib test - you need to be in AltHold before putting it in autotune. I expect that is the problem.

        • This reply was deleted.
          • Richard Kennedy May 7, 2015 at 4:53am

            If you take off in stab mode and then hit alt hold does it shoot up or down a lot even at mid throttle? If so you might need to balance your props better. I use this it works great.

            http://www.amazon.com/Du-Bro-499-Tru-Spin-Prop-Balancer/dp/B0006N72Y8

            Only other thing that come to mind is part of the mandatory set up isn't done but then again it shouldn't arm in that case. Do you have pre-arm checks ON aka '1'? If not this might help you figure out what is going on. It's on by default so unless you turned it off it should be on.

             

            • This reply was deleted.
              • Mark Slater May 7, 2015 at 7:33am

                I think you need to do it the other

This reply was deleted.

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