@iUAS_AUS wrote:
I have been testing 3.4 recently and was checking some motor imbalance issues in ALTHOLD and POSHOLD. This is a newish machine and I have not begun to tune it so most of the settings are defaults. Even s,o it is very stable and flies quite well, with room for improvement but I am very happy with it so far.
On this particular flight I had two GPS units attached, even though I know I shouldn't just to see what the relative differences were. I was actually working on a motor imbalance where I am seeing motors 1&2 constantly higher than 3&4. Strangely it flies straight and throttle inputs do not result in any noticeable yaw. I think there is a twist somewhere but cannot find it.
In general both ALTHOLD and POSHOLD are working very well. Very little drift and no strange yaw or altitude oscillations. It is like it is on rails most of the time.
About 8 minutes into the flight the active GPS glitches and changed position radically by about 50m from my backyard all the way to the street. It took about 40 seconds for the GPS position to come back into line with the actual position of the quad.
When the glitch happened I was in POSHOLD mode, hovering, with no stick inputs. I saw the quad jump a bit and corrected. I had to correct a couple of times before I felt the need to switch to ALTHOLD.
Overall the whole thing was quite tame and at no time did I feel as if the quad was out of control. It did not suddenly fly off into a wall. I am not sure if the EKF recognised the glitch and I whether having two GPS units added to or helped with the problem. I know that two GPS's is not recommended but I was curious to see what would happen. I have gone back to the single M8N.
I can see in the logs that the desired position diverges greatly from the actual position but this did not seem to translate into a sudden uncontrollable change of attitude. It did move away but I could easily correct it and take control. This may be due to the max accelerations in auto being set quite low.
I am interested to find out how the EKF handled this and what it did to keep the craft stable in POSHOLD when the GPS location changed. I did manually correct but did not have to radically compensate.
I would appreciate any insight into how the firmware handled this.log file: https://www.dropbox.com/s/7q6p0j9fri494t7/2016-06-15%2014-32-54.bin?dl=0
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