And my Iris+ just went away...

Posted by Pascal P. on October 30, 2014 at 10:25am

Sad day. After good trials with original battery, very easy loiter mode, stable, gentle landing... real pleasure.

Today I changed to spare battery (Turnigy Multistar 5200 mAh 3S 11.1V). Switch on, proper blanking green, but as soon as I give some throttle the Iris jumped approx 20m in the air and started to run straight like crazy. Impossible to follow. Lost.

Do you think only the battery change could have done that ?

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Replies

  • Developer
    Craig Elder November 3, 2014 at 6:16pm

    Hi Pascal

    Sorry to read about your flyaway.

    The compass and accelerometer calibrations and the vibrations look fine.

    It looks like the vehicle was being moved while the gyro was being calibrated at the start of the flight - the time when the LED is flashing Red and Blue.

    3701866269?profile=original

    You can see the DCM Yaw diverge from the EKF Yaw throughout the flight

    3701866137?profile=originalRoll and Pitch also diverge indicating something is wrong but the culprit is yaw because the copter is heading in the wrong direction away from home as the vehicle is attempting to RTL.

    We have recently made a change to the flight code in the beta of 3.2rc14 that detects if the vehicle is being moved while the gyro calibration is taking place and handles this fault better.  I suggest you download that code from the beta section of your planner.

    • Developer
      Craig Elder November 4, 2014 at 4:39pm

      Hi Alex,

      I'm glad you are learning to read the logs and it is great that you are helping other people.

      I have looked at a lot of Iris+ logs and with so many identical vehicles we have a lot of data on them. The compass offsets are all very similar and the accelerometer calibrations are all very similar plus all the vehicles are test flown before they leave the factory.  That is one advantage of an RTF vs a One-Off vehicle.

      If you graph the vibration levels they are very small and the magnetic offsets are reasonable.  If you look at the altitude during the RTL there is no indication that it is being affected by vibration.   Normally that looks like the calculated altitude drags the desired altitude with it.

      What we do see is the DCM Yaw diverges from the EKF yaw which is a classic indicator of a gyro calibration issue. That is what is showing in the first graph.

      In fact we recently put a patch in https://github.com/diydrones/ardupilot/commit/0ac3267d520aa3331c6c0...

      to deal with a gyro that has been calibrated while it is moving.

    • Pascal P. November 4, 2014 at 10:12pm

      Hi Craig and Alex,

      Thanks for your analysis and diagnostic. So we have an explanation on what happened. Gyro calibration make sense to me as I am working in the hydrographic survey business, and on a vessel almost everything rely on a good gyro calibration. Maybe the documentation should insist on not hurry before the first flight. I am not 100% sure now, but I really think the green light was blinking, and in my mind that did say that Iris is ready to take off.

      Considering parameters, I was effectively confident from start to the fact that all vehicles being identical and tested, there was little chance that factory set up was wrong. In fact after my new calibrations I found very close results on parameters than what I had before. But I have really no experience to quantify even a small amount of change there.

      Thanks Alex and all the others to participate and try to help. We are all learning and this new field is very interesting to discover. After the Iris reception, last week was full of enthusiasm , good surprises and also profound interrogations. To say the least, discovering and learning really kept my mind busy and focused. It is a very pleasant experience I would recommend to everybody.

  • Manuel Ribeiro November 3, 2014 at 3:12pm

    Sorry for the newbie question but, shouldnt we try to arm on loiter mode, so it can record home position ?

    • Manuel Ribeiro November 3, 2014 at 3:55pm

      Oh... I see. 

      Will it arm in loiter even if it has bad GPS signal ?

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    • Pascal P. November 3, 2014 at 6:11am

      Thank you very much Alex for all these recommendations.

      I did a compass calib, as well as a Acceleration calib, reprogram stabilize in place of alt hold on the switch.

      And continuously did a take off - hover - landing sequence until battery was weak. All seems ok.  I kept in mind your "with confidence and authority". So far so good. No more strange behaviour, confidence is greatly increasing in the system.

  • Pascal P. November 2, 2014 at 9:48am

    Note that when looking at configuration I saw that a "V" frame type was declared. I correct by choosing "X". Any influence or calibration to redo ?

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    • Pascal P. November 2, 2014 at 8:47am

      Hi Mark,

      No feedback from 3DR yet.

      I have some very nice automatic flights after manual take off. But definitely take off is always a moment of tension. Sometime motors seem to suddenly increase power even if I give a slow progressive throttle. Iris tends to start flying quickly to the side. So I immediately reduce power, in general resulting in a flip upside down. The thing is if I disconnect battery and restart a take off procedure, all is in order, stable and progressive.

  • armen t October 31, 2014 at 7:06pm

    wow awesome that you recovered your Iris+

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