Discussions

All motors stop suddenly with Pixhawk

Posted by Staq Koenig on August 22, 2014 at 12:50pm

I was maidening a mini H-quad with a Pixhawk running AC3.1. On my first hover in stabilize mode, it worked beautifully. It was hovering perfectly still without any trimming needed. About 4 minutes into the hover, with the quad at about 2 meters high, all the motors suddenly cut off, and the quad just fell to the ground. I have attached the Pixhawk log file and hope some knowledgeable kind soul can help me decipher what went wrong.

Thanks for any help rendered!

Staq

PS: The quad suffered no damage, only 2 broken props. Really wish to know what really happened up there. Dare not fly it at the moment.

2014-08-22 23-25-45.log

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Replies

- - Andre K. > Staq Koenig August 27, 2014 at 6:36am
    
    oh, and the voltage drop is about ~35mV, insignificant.
    
    you whole flight varied between 5.250 and 5.170 - well within limits. ending record of 5.173 is not a problem.
    
    Most of Pixhawk works at 3,3V anyway. and it would be out-of spec around ~4.8 or less.
    - Staq Koenig > Andre K. August 27, 2014 at 9:23am
      
      Ok thanks. I'll replace ESC 4 and try again.
  - Andre K. > Staq Koenig August 27, 2014 at 6:30am
    
    ok, I guess you still won't believe my conclusion, like before - but what you *actually* can see, it Chan3 drop proportionally to 4, because motor 3 is the opposite motor of 4.
    
    Like I told you, you lost lift on 4, so the opposite motor *must* reduce power not to flip.
    
    motor 1,2 ? - they rotate in same way, they only adjust yaw at the time, and are forced to reduction, unless Pixhawk planned to spin it wildly around...
    
    Servo outputs are behind a polyfuse, so pixhawk would not reboot . but ESC's usually have their own working voltage.
    
    Stop overthinking it, you had a ESC, sync, motor, propeller or propeller-mount problem. - thatt's it.
    
    Pixhawk only logged until crash made it lose power or reboot. - the final few lines may have not been written or not in an cluster that got updated in FAT.
- Staq Koenig > Tim August 27, 2014 at 1:37am
  
  Thanks Tim for the analysis. I thought the current graph showed that the voltage and current reading got cut off abruptly in mid flight while the other data is still being recorded. Just like what Andre was pondering (see below), if in fact a brownout did occur, why did other sensors continue to record the final moments while volt and current recording has already stopped. I do not have my logs with me now but I'll try to post pictures of the volt and current reading vs other data once I have the logs.
- Jesus A > Tim August 24, 2014 at 12:16am
  
  Hi.
  
  Just an idea.
  Could it be a Hard Cut off by the own ESC due to low battery?
  It sounds like ESC problem
- Michael Cook > Tim August 23, 2014 at 9:39pm
  
  I had the same problem and the only thing that I can suggest is to reload the Arudpilot to the autopilot.
Moderator

Graham Dyer August 22, 2014 at 1:00pm

I had exactly the same thing, except mine stopped at 11m high and the damage was fairly substantial, I still have no explanation but what I do have now is a lack of trust.

http://ardupilot.com/forum/viewtopic.php?f=25&t=8769
- Staq Koenig > Graham Dyer August 22, 2014 at 1:11pm
  
  This is scary, Graham. I am also using Tiger motors, and all original 3DR components. But I am not even doing any flying, just hovering on the spot, and yet this happens. Sad. My faith is shaken now.