I'm sorry it took so long to write my next blog entry, but we were quite busy debugging our UAVPs and fixing problems.
But let's start at the beginning. As you all know we had 2 big problems. First, we had to set the yaw integral to zero and second the whole UAVP had a tendency to flip.
After long investigations with sepcially hacked debug firmware (written by Wolfgang) we finally could isolate the flip problem. It turned out to be quite simple... Since the motors never should stop, we had a sort of lowest level of thrust we allow the motors. Now if the UAVP needs to stabilize it speeds up one motor and slows down a second. Should it happen, that the motor slowing down reaches the minimum allowed speed, we keep it at that and do not allow it to go lower.
BUT, the second motor speeding up we allowed to go faster! This resulted in a inbalance which in turn escalated to flipping the UAVP!
Fixing this was simple... if we have to limit the motor slowing down, we also limit the motor going faster. Wolfgang implemented this simple fix and the UAVP does not flip anymore.
I still ponder if this is the best solution. Imagine a "dynamic throttle adjustment" which will increase the throttle as soon as the motor slowing down crosses the limit. Increasing the throttle would increase the spinning of all motors allowing the motor slowing down to be able to do so!
The second problem concerning the compass could be fixed quite easily as well. Wolfgang had used a fixed constant value of 16 to correlate the compass's and the yaw-integral's influence. Reduncing this value to 8 or 6 corrected the problem. So it really was a sort of fight between yaw-integral and compass. Wolfgang made this value configurable.
But back to the last test flights. Using the newest firmware (a pre-3.13 version) my brother was able to fly for as long as 6 minutes, which is one of our longest flights.
But watch for youself:
Get the Flash Plugin to see this movie.
We hope to fix the last problems soon. Then nothing will hold us back from flying up to 20 minutes with our 5000mAh batteries. And there are as big as 8000mAh batteries available out there. I think the weight will be no problems on ou overpowered UAVPs...