Please could someone help analyse this Autotune/Pixhawk crash?

Posted by Ben on September 16, 2016 at 4:00am

Was flying perfectly well on stock PID settings but wanted to see if autotune could improve things.

About 3 minutes into the tuning whilst still on the first axis it suddenly flipped over and crashed without any warning. It looked like an overly aggressive roll command caused it rather than a motor cutting out or stalling. Conditions were calm at the time.

It had completed about 90% of a previous autotune without incident but didn't have enough battery to finish, was in the air for about 15 mins without incident in autotune mode but had to land.

Sent it up again with a fresh battery, this time without any payload to help ensure sufficient flight time to complete tuning on single lipo (New C of G was accounted for by shifting lipo position) and the crash happened.

RATE_RLL_FILT_HZ and RATE_PIT_FILT_HZ were set to 10hz as recommended for larger props and battery voltage scaling of PID gains was setup..

Spec:

Pixhawk on a 900mm Y6 frame with T-Motor 4008-18 380v motors, 10000mAh 6S lipo, 15" props.

If anyone fancies looking at the log, it would be most appreciated - I've checked a few things but still unsure on the exact cause - possibly the default AUTOTUNE_AGGR parameter which I left alone as per the instructions was simply too high?

210.BIN

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Replies

  • Mikko Korhonen September 23, 2016 at 2:00am
    You have same issue that i have with my board. AT just wont work. Dont do the same that i did..ctashed my rig multiple time with at. There is other ways to tune your rig.ch6 knob/ save tune etc. Is your rig unstable with stock pid's?
  • Ben September 23, 2016 at 1:31am

    So, against my better judgement, I tried Autotune again on the same craft. Geo Fence was turned off this time and the autotune aggressiveness lowered to half the default value.

    It did EXACTLY the same thing again, flipping upside down on the roll axis and promptly crashing.

    There are no errors in the log that I can see, so I think it's safe to say my issue is not geo fence related, as per the initial analysis.

    Log attached - would appreciate if anyone can spot the issue this time.

     

    226.BIN

    https://storage.ning.com/topology/rest/1.0/file/get/3702303106?profile=original
  • matt.koestner September 20, 2016 at 9:49am

    Well it's not really a coincidence.  Autotune demands large and fast attitude changes which demand rapid RPM changes from the power train.  Any ESC, motor, or battery problems usually show up during auto tune.  Look at it this way, if yout copter can make it through an auto tune, it will probably make it through just about anything the autopilot would need it to.


    Mikko Korhonen said:

    Looks like that. Thanks, easier to understand with baro graph same time on the screen :) So it looks like that it was just coincidence that it went down during autotune. I must check power cable, maybe my diy dual battery splitter wire connections are oxidised or bad solder in connectors.. Thank you :)
  • Mikko Korhonen September 19, 2016 at 4:38pm
    Looks like that. Thanks, easier to understand with baro graph same time on the screen :) So it looks like that it was just coincidence that it went down during autotune. I must check power cable, maybe my diy dual battery splitter wire connections are oxidised or bad solder in connectors.. Thank you :)
  • Cala September 19, 2016 at 4:25pm

    Mikko: looks that your batt drops and inmediately your copter crash

    3702302107?profile=originalYou can ask to devs here: http://discuss.ardupilot.org/c/arducopter

  • Mikko Korhonen September 19, 2016 at 4:10pm

    Thanks for taking a look. Batterys were full. I don´t understand this vcc or power value graph..i see a drop in the graph and i understand that voltage/current (?) went down at the end.. copter went mental before hitting the ground, it had plenty of power !, that didn't looked like a "brownout" etc. crash, i had one and i remember the power drop in that log..but like i said, i dont know how to interpret these power issue logs. Vibes and imu1&2 are next to look into. Thanks, im trying to find some info...gooogle! :)

  • Cala September 19, 2016 at 3:25pm

    Mikko,: your batt was full when you try AT?  It's look low when you crash, can be the problem?

  • Mikko Korhonen September 19, 2016 at 1:30pm

    here´s my autotune crash bin. file

    2.BIN

    https://storage.ning.com/topology/rest/1.0/file/get/3702301637?profile=original
  • Mikko Korhonen September 19, 2016 at 1:21pm



    Cala said:

    Yours and Ben log is the same?

    Yes...sorry,,mixed bin files, reason for my crash was not fence error. looking into logs now.

    Sorry again..too much going on at the same time :)

  • Cala September 19, 2016 at 7:47am

    Yours and Ben log is the same?

This reply was deleted.