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Help - quad zooms up in alt hold

Posted by Dave Jeffries on September 10, 2013 at 6:34am

Hi,

Got my quad flying fairly well in stabalise mode, so I thought I'd try alt hold in my garden.

As soon as alt hold was selected quad went straight up to about 30mtrs and so i shut throttle and switched back to stabalise mode.

I just about managed to get it back down into my garden although I panicked and ended up breaking a prop.

I have attached the log, can anyone see what went wrong?

Thanks,

Dave.

2013-09-10 13-36 13.log

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Replies

  • Dave Jeffries September 20, 2013 at 3:35pm

    Thanks all, the quad is now flying well in alt hold, loiter and RTL. Will try an auto mission on the weekend!

  • Dave Jeffries September 18, 2013 at 5:52am

    Have now put in some vibration damping and the improvement in the logs is pretty good I think. I have included the new log which I think now gives me +/- 0.15G in all three axis. I'm hoping that will be good enough. The big blip on the log is me flying into a tree :).  Any comments are welcome.

    2013-09-18 13-28 15.log

  • Dave Jeffries September 11, 2013 at 3:25am

    Changed the props from 0945's to 0845's and did another flight with IMU added. It seemed to more stable than before, but having looked at the logs I do have a vibration problem. I will try remounting the APM1 and see what happens. The throttle in for hovering looks like it's around 480, is that what I should set THR_MID or should I leave it at 460 which is rounghly throttle out?

    The log is attached, any comments are very welcome.

    Thanks, Dave.

    2013-09-11 10-55 14.log

    https://storage.ning.com/topology/rest/1.0/file/get/3692826471?profile=original
  • Max Patissier September 10, 2013 at 9:09am

    Hello, I have the same behavior and what I do not understand is :

    * on stabilize, the accZ seems to be perfect (X & Y also) and the quad fly well - But sometime, as soon as I turn on Alt Hold, the accZ is x by 10 and the quad start jumping up (THROLin=465 and THROout=900). Which is the relation between accZ and AltHold, I mean why using AltHold make the accZ crasy ?

  • RickP September 10, 2013 at 7:43am

    I concur with Chris - and had a look at the log, but there's no vibration information. You can clearly see that it climbs rapidly in ALT-Hold, and you did well not to panic and go into stabilise.

    I'd turn on IMU logs, and do another flight in stabilise and look at the vibrations - you'll have some work to do, I think. More details instructions here: http://copter.ardupilot.com/wiki/ac_measuringvibration/

  • Tero Koivunen September 10, 2013 at 7:39am

    WpAlt negative during Atl_hold, strange.

    Maybe not cause for this, but

    THR_MID quite high 600, should be 350-400

  • 3D Robotics
    Chris Anderson September 10, 2013 at 7:04am

    Have you mounted the APM on vibration-damping foam? If not, Alt-Hold won't work (it uses the accelerometers).

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