Discussions

Please help diagnose my APM 2.6 flyaway

Posted by zub on January 5, 2015 at 4:03pm

I have just registered for DIY Drones, so please bear with me as this is my first post.  However I have been flying for years and been flying my quad running originally APM2.5 and now 2.6 for the past year or so.  It is an original 3DR unit bought from Build Your Own Drone here in the UK.

I was flying yesterday and was in LOITER mode and the quad suddenly went full throttle skywards!  I got it under control by hitting RTH and STABILIZE but it was totally unexpected.  So I went through the data flash log, which I have attached, and it seems like (it appears) the APM thinks I went full throttle with my TX stick - which I didn't!  Until I had it in LOITER I was flying around fine.

Looking at the logs, I appear to have a good GPS signal, no obvious voltage or current issues or anything else that would point to a problem with the quad.  I have attached a screen shot of ThrIn and ThrOut charted alongside Altitude so you can see the thing go bananas!

I am at a loss as to what has happened here, thank goodness for the data flash logs as at least I can rule things out, but I'm struggling to work out what the problem is.  The flyaway appears just after the 3000 mark.  

If anyone can point me in the right direction I would be most grateful!

Screenshot 2015-01-04 21.32.59.png

2015-01-04 20-47-24 56.log

2015-01-04 20-47-24 56.log.gpx

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

Join diydrones

Email me when people reply –
Follow

Replies

  • zub January 18, 2015 at 9:23am

    Thanks everyone for your help and advice on this.

    I have now:

    - updated to arducopter 3.2 firmware

    - changed the anti-vibration mounts, with 2 foam mounts in each corner, and have one of those suspended platform on order

    - enabled IMU logging

    - clearly I needed to re-do the accelerometer and compass calibration, but have also spent a lot of time on the power monitor calibration, just in case the APM thought there was low battery voltage and caused an RTL command.

    I have just done an extended hover in very calm conditions and the IMU data seems good: the X and Y accelerations are between +2 and -2, which is within the +3 and -3 in the manual, and the important Z accelerations seem to be -7 to -11, which is within the -5 to -15 range referred to in the measuring vibration wiki

    http://copter.ardupilot.com/wiki/ac_measuringvibration/

    However I would note that in the  vibration damping wiki here:

    http://copter.ardupilot.com/wiki/vibration-damping/

    ... it says 

    "Vibration needs to be less than 0.3 G in the X and Y axes and less than 0.5 G in the Z axis."

    I don't know what units the ACC_X, Y and Z are, if they are in m/s/s, then -5 to -15 sounds like c. 0.5 - 1.4G (if G is 9.8 m/s/s), which is a bit confusing.

    Anyone shed any light on this?  Does my ACC_Z look ok?  I have attached the log if anyone is interested, but recognise lots of people have helped me already, so thank you.

    Anyway next on the list is to do the autotune.

    3701915437?profile=original

    2015-01-18 16-43-56.log

  • zub January 10, 2015 at 3:29pm

    Thanks so much for your input, it is really great having help like this.  How to diagnose a flyaway is painful, as I have lost a bit of confidence in the quad because of this!

    Running through the answers:

    Mike, pyrosamz:  I am not sure I had a GPS glitch, as no. of sats and Hdop look ok.  I have attached a screenshot of the graph of sats, hdop and altitude, where you can see that sats and hdop were steady (and good) whilst altitude was increasing.

    Also there were no errors.  I searched for ERR and ECode in the log and there was nothing to suggest the GPS signal was lost, which caused a switch to RTL.  On the contrary, looking at the logs I go into LOITER at about 2,500 on the x-axis, and then at 3,000 it starts the flyaway,  with me hitting the RTL at 3,150 to get it under control.

    AndreK - thanks for your advice.  I don't have IMU logging, I will now!  I will also update the firmware.  However I am not sure why v.3.01 that I was running would have caused this whereas the latest firmware is ok.  It is the cause of the problem I am struggling with.  However as well as updating the firmware I will change the anti-vibration mounts to help with z-axis vibration as you suggest. 

    I have also removed two of the props which I could feel a bit of slip, and will re-mount them.

    Thank you guys for your advice and help.  This has been instructive - if painful!  I have a Blade 350 QX2 quad (amongst others) which just flies out of the box, which I have confidence in.  My APM 2.6 has caused a wobble...  but I'll get over it, not least I have a tri-copter build coming up on an APM 2.5,  and fly my plane on an APM 2.6 too!

    Anyone else got any ideas?

    3701910147?profile=original

    • Zeke Zero > zub January 11, 2015 at 7:24am

      Zub,

      I have suffered from the same issue with APM and Pixhawk (which I thought would be immune because of fancy dual sensors and clever EK Filter..).

      I would strongly suggest checking your IMU Z vibrations as Andre says.   Check the Arducopter instructions for reviewing vibration.  Z axis should be between -5 and -15 in a hover:    http://copter.ardupilot.com/wiki/ac_measuringvibration/

      Also have alook at http://copter.ardupilot.com/wiki/vibration-damping/

      All the best,

      Zeke,

      Worcester,

      UK.

      • zub > Zeke Zero January 11, 2015 at 1:44pm

        Zeke

        Thanks for your advice.  I have now mounted the APM on two foam pads, plus a third "softer" pad.  Reading through the info on vibration damping, I'm not sure what to make of it!  It goes from one school of thought that says moongel is great, to another which says mount directly on the quad!  I have now enabled IMU logging, I will take it for a flight this week and have a look at the data.  

        I really appreciate everyone's help here, thank you.

        Zub

        • Zeke Zero > zub January 12, 2015 at 2:27am

          No worries Zub  (Zeke /  Zub lol..)

          I found these to be great: anit vibe mount
          <http://www.goodluckbuy.com/glass-fiber-flight-controller-anti-vibra...>

          cleardot.gif
          mounted with this between airframe and mount and between mount and
          controller.

          As with all things APM there are a hundred different ways to do the same
          thing!
          • zub > Zeke Zero January 12, 2015 at 2:46am

            From one "Z" to another...!

            Perfect, thank you.  Just bought a few of those anti-vibration mounts, and I have some foam pads already.

            Much appreciated.

            Zub

  • pyrosamz January 9, 2015 at 3:57pm
    In advanced parameters list what's your rtl hight set at? I think default is 80m.if you have a rc failsafe set up correctly the first thing that will happen is the copter will rise to that altitude in the event of failsafe be initialised.
  • Andre K. January 8, 2015 at 10:29am

    you have no IMU logging, but behavior like this can be trigged by too much Z vibrations.

    At least you can forget GPS problem.  You can clearly see the compensated GPS.RelAlt pretend to drop, even when CTUN.Baralt shows that you are climbing.

    Also, it seems you should upgrade, I think you may have very old ArduCopter.

  • Mike Kelly January 8, 2015 at 7:43am

    Since no one else has answered....

    If you had a gps glitch or something else that triggered an RTL failsafe it can appear as a fly-away. It shoots up to reach the safe altitude to start it's return.

This reply was deleted.

Activity