In a recent flight I had flown about 10 minutes in a combination of loiter and guided. While the aircraft was in the middle of a guided leg, I switch to alt hold. The aircraft immediately started to oscillate and eventually crashed.
I'm confused by this behavior because I've done extensive PID tuning and the aircraft is very stable in all modes, including alt hold. It seems like the problem was due to the sudden switch from guided to alt hold while the aircraft was in motion. What could be the cause of this?
You can see in the logs and screenshot attached that the Des Roll/Pitch are way off as soon as it is switched to alt mode. Earlier parts of the flight show that the des roll/pitch and actual roll/pitch track really well, indicating a good tune. Also this flight was in 10-20mph winds and the aircraft was extremely stable up until the mode switch. The aircraft has been autotuned and flies great with the exception of this case.
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Another flight followed this one and a few more details about the problem observed. When strong on the stick into the wind and then the stick is released, the copter gets tilted back well beyond level (by the strong wind) and then cannot recover and goes into an oscillation and then a crash. I now suspect that our PID tuning needs adjustment but not sure how to adjust values given this problem, any guidance?
Note that the system hovers at about 45% throttle, so I don't feel like it is under powered. Also note the there is some clipping at the upper and lower limits of motor outputs during the oscillation. Is that normal? See that attached log.
45 5-5-2016 11-55-12 AM.bin