Discussions

Power Failure, What Happens?

Posted by Erik on February 23, 2015 at 4:21pm

Q: What happens when the Pixhawk loses power during flight?

I recently suffered minor damage in a crash when I lost control over my hexa.  I was about 10ft away from the hexa at takeoff and lost control when it was probably 25ft away.  I know the receiver/transmitter is a possible culprit, but I did notice the power cable going to my Pixhawk was disconnected at the crash site.  Did it come loose during the crash or before, I don't know.  What I'd like to find out is what is the expected behavior when you are mid-flight and the Pixhawk goes dark.

Figuring out a root cause is going to be a process of elimination for me as well as measures to help beef the system up (redundant power sources, zip ties or whatever else I can find to keep connections secure, etc.

Thanks,
Erik

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Replies

  • Crispin February 26, 2015 at 2:54pm

    I am sure the current version has crash detection? If so and it did not log a crash then perhaps it lost power? 

    All depends on how much time between the crash and power loss - could it write? 

    • Erik > Crispin February 26, 2015 at 5:34pm

      Good point.  I'll look for this tonight.  I haven't - thus far - looked at the logs.

      -Erik

      • Erik > Erik February 28, 2015 at 1:43pm

        So I've gone through the logs, but I can't say I have a better understanding of what actually happened.  I ran the auto analysis on the log and this is the output I received from that:

        Log File C:/Program Files (x86)/Mission Planner/logs/HEXAROTOR/1/2015-02-21 17-06-08.log
        Size (kb) 1020.9130859375
        No of lines 14075
        Duration 0:04:35
        Vehicletype ArduCopter
        Firmware Version V3.2
        Firmware Hash c8e0f3e1
        Hardware Type
        Free Mem 0
        Skipped Lines 0

        Test: Autotune = UNKNOWN - No ATUN log data
        Test: Balance/Twist = GOOD -
        Test: Brownout = GOOD -
        Test: Compass = GOOD - mag_field interference within limits (11.22%)
        Test: Dupe Log Data = GOOD -
        Test: Empty = GOOD -
        Test: Event/Failsafe = GOOD -
        Test: GPS = GOOD -
        Test: IMU Mismatch = GOOD - (Mismatch: 0.39, WARN: 0.75, FAIL: 1.50)
        Test: Parameters = GOOD -
        Test: PM = GOOD -
        Test: Pitch/Roll = GOOD -
        Test: Thrust = GOOD -
        Test: VCC = GOOD -

        I don't know if crash detection would show up in the auto analysis or not?

  • SteveC February 26, 2015 at 2:40pm

    One of the beauties of the Pixhawk is having data logs available to determine cause of flight behavior.

    The log should reveal when the power cable was disconnected.

    If you have FAILSAFE setup for low battery the craft can RTL or LAND.

    Fore instance; I have both low BATT and low Mah set for FAILSAFE.

    If no failsafe or alarms are setup then it flys until if falls, but default.

    Best,SC

    • Erik > SteveC February 26, 2015 at 5:33pm

      Good suggestion.  I will review the Pixhawk logs and see if I can determine if it lost power in the air or not.  I'm pretty new to this, so wasn't even thinking that was an option initially.

      I think I'd like to configure FAILSAFE like you have.  Any tips on how to go about doing this?

      Thanks,
      Erik

      • SteveC > Erik February 26, 2015 at 6:19pm

        Here's Randy's YTV on battery calibration

        Here's a YTV on Battery Failsafe

        SC

        • Erik > SteveC February 28, 2015 at 1:52pm

          Thanks for the links!  I've already calibrated my power sensor, but I will enable the failsafe features for sure.

          I don't really understand the log output, but the last line I have (line 14,074) was from my BARO.  Does this mean the Pixhawk lost power abruptly mid-air?  When I got to the crash site, the power cable going from my power sensor to the Pixhawk was disconnected.  Just unsure if it came loose during flight, causing the crash... or if it came loose on impact.  If I can figure this out somehow, I'll feel a lot better.

          Thanks,
          Erik

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