Discussions

Hints for crash analysis needed

Posted by jaron on October 1, 2014 at 6:04am

I've got the problem described below and maybe you could give me some hints where to look for possible causes.

Frame: Quadcopter (many successful flights before modifying the camera gimbal)
Hardware: APM 2.5
Firmware: ArduCopter V3.1.5

Problems:
- Random, light twitches during flight
- Sudden altitude drop after a while in loiter mode
- Sudden roll to the left while hovering in stabilize mode, resulting in a crash

According to the information found here and the log, it could be a mechanical failure. I assume if I'd had a problem with a motor or an ESC, roll and pitch should show similar behavior in the log.

I'm also not sure if I can exclude a problem with the receiver or the PPM encoder.

3691154113?profile=original

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –
Follow

Replies

  • jaron February 20, 2015 at 12:04pm

    I've finally solved the problem and maybe this is helpful if you are experiencing sync issues with high-pole-count brushless motors.

    All my further testing lead to a sync issue of the motors (Turnigy Multistar 4220-650Kv + Afro 30A ESC) probably caused by higher weight and therefore higher current flow.
    I've tried different firmwares (SimonK, BLHeli) in various revisions with all kind of settings. Then I've tried different ESCs (Afro HV 20A, HobbyKing BlueSeries 30A) with no success. The sync issues remained and it looked like the motors were causing the problem. 

    In a last attempt I bought some Hobbywing Xrotor 20A Opto ESCs and without any further setup (except calibrating) the sync issue was gone.

  • T3
    Richard Boyhan October 2, 2014 at 3:44pm
    Try changing the frame rate on your transmitter from 22ms to 11ms. Don't forget to rebind after you change the rate.
    • jaron > Richard Boyhan October 3, 2014 at 1:47am

      Thank you, Richard!

      One of the first things I've done was switching from 22 to 11 ms and I might be wrong but it felt like the twitches where still there. Then I switched back to 22ms and did all the above. So far it seems to work.

      Are there any downsides with the 11 ms frame rate?

      • T3
        Richard Boyhan > jaron October 3, 2014 at 8:23pm
        Not that I'm aware of.
      • Andre K. > jaron October 3, 2014 at 11:35am

        log RCIN first -   you should then see bad input. - I doubt RC is to blame.

        post full log if you want people to be able to help, and actually be able to base assumptions on something.

  • jaron October 2, 2014 at 7:21am

    Thanks Andre!

    I've done the following and at least for the last two flights the problem was gone:
    - Disconnected and reconnected all the cables
    - Re-flashed the PPM encoder
    - Fixed the APM inside its case and re-mounted it with three layers of double sided tape
    - Re-routed some of the cables
    - Rebound the Spektrum receiver
    - Re-calibrated Radio, Accel and Compas in the Mission Planner

  • Andre K. October 1, 2014 at 11:48am
    Log and check vibrations as well
This reply was deleted.

Activity