After re-building our H8 and re-tuning it with autotune. (previous post Autotune Crash) I had a few good flights. The rig was flying very nicely, autotue had done an excellent job at tuning the PIDs.
However, we went out on a job today and decided to to use this rig as it was best suited and is / was flying very well.
After a few flights I got lazy and desired to do a RTL. The gig flew back very nicely and started to land. At this point I jumped over to to Loiter as it missed the home point and was going to land in a pond.
As soon as I switched to Loiter the rig started to yaw clockwise and descend. I reacted by applying ccw yaw and waking the throttle full up.
I got no response, the hely just continued to yaw CW and decent into the pond, Unfortunately the camera was not recording at this point so no sound captured.
I have looked at the log several times and my understanding of it is:-
vibrations are low.
https://www.dropbox.com/s/uczdnodfzrdp7u9/Vibration.JPG?dl=0
I bereave the vibrations are low typically between 0.4 and -0.4.
VCC Voltage:-
Still fluctuating too much but there is also power from the rail and USB.
The point when all went wrong is exactly when I switched from RTL to Loiter.
Tracking, looking at DesRoll vs Roll it was racking very well up until the point there it switcher to Loiter around 19.5 mins into the log. The then starts drifting ever so slightly.
https://www.dropbox.com/s/qfvy0di1qi5va0b/RollvsDroll.JPG?dl=0
The point where is diverse off is when the Helli is lifter out of the water.
Yaw:-
You can see the Yaw at the switch over point. is basically starts spinning CW.
https://www.dropbox.com/s/3nbzr998sayaa7n/Yaw1.JPG?dl=0
Now something funny here. I’m not sure how accurate the timing stamp is but looking at the RCIN4 it does look as though I instruct a yaw at around 177478,1502 and the heli starts yawing at 177530,282.81 a little after. This is odd as as I remember it I commanded a CCW yaw to counter-act the CW yaw after it started yawing!!!
Also the DesYaw is matching the Yaw! this is also strange.
Altitude:-
At 178938,1548 you can see I hit the throttle (Altitude) up to stop the heli from descending into the water.
However you can see the altitude droops NOT fast but relatively slowly and is matching DAlt. So it os clear that the NAV is wanting the hely to decent. Question is why???
https://www.dropbox.com/s/071dvgg6o4ciez1/Alt.JPG?dl=0
As for the battery, i’m not sure which data in the log to look at. but they were at 73% when I checked after the crash…
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So two issues, is the system miss decoding the Yaw commands? Is my radio going nuts?
but mainly,
Why did the heli drop and land in the pond dispute me commanding a increase in altitude!!
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PLEASE could somebody have a look and cast some light into this.
Pixhawk Log:-
https://www.dropbox.com/s/vxbrtca58eh0036/31.BIN?dl=0
Tlog:-
https://www.dropbox.com/s/hc2gsa24mkku2w6/2015-12-16%2011-53-53.tlog?dl=0
Thanks
Anthony