Hello everyone! I've set up an Iris to do survey work with a NEX 7 mounted below it. When it flies its pattern it will climb to over 10 meters above its designated altitude of 50 meters. However this only occurs when the Iris is traveling to the west. The following screen shots of the flight KML and altitude graph really illustrates this problem:
I have tried both calibrating the compass and performing an autotune with the camera attached. This problem occurred both before and after these calibrations. I'm really at a loss for what is causing this so any help would be greatly appreciated! I think I've attached all of the relevant files, but if anything else would be of assistance, I would gladly provide it.
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I've just gone for another flight with different flight plan to see if that was the issue, however the problem persisted. I'm pretty sure it isn't due to insufficient GPS coverage as I ensured the HDOP was <2. Again the problem is only when the Iris heads to the west. Could it possibly be due to a faulty compass calibration?
Here is a screenshot of the most recent flight:
2014-07-14 11-53-23.kmz
2014-07-14 11-53-23.log
Could it possibly been wind? When changing directions and the because the quad will be flying a ground gps speed to maintain not an airspeed, it will rise when turning into the wind, and then it will take a bit before enough "I" gets involved to lower to the correct altitude. If your flying into a headwind maintaining a gps groundspeed it the quad will continue to increase pitch and power to try and get back up to that speed. That could result in the climb you see until the error builds enough, and the quick correction happens. Going downwind or with the wind the quad would not exhibit this symptom as it will not have much forward speed in relation to the air. The short horizontal run with the 180 turns would exacerbate the issue. Have you tried it on a different day, different wind direction, and for a longer horizontal length of straight run?
Well, I've solved the problem! It turns out that the autotune had reduced the PID values to a point where they could not compensate for the extra mass of the camera. To solve the problem I just loaded the default values for Iris with a GoPro and Gimbal. Now she flys like a champ! So you comment about the "I" value was spot on JG. Thanks!