This project is a big project and its important to have some success along the way. Its easy to get mired in a bunch of problems such that you experience no successes that you can celebrate.
So in a project this large its important to schedule small successes to keep the motivation up while you slog through the details of 10K things.
I went out and flew the helicopter again tonight. For the first time I turned on the integral term in the gps position hold. It made a huge difference. A helicopter flies with a slight tilt, the tilt is such that with purely proportional position gains it has to build up some error to stop moving. Then it also moves around as the wind changes and the proportional error grows to the point to counter the wind. I’d been doing: Start where you are, climb vertically, hover for awhile and land. I also like to be behind the helicopter when playing safety pilot as its easier to stay oriented and try a save if needed. Well it just so happens that in proportional mode every time you do one of these cycles the helicopter backs up and to the left about 2m. Do it 5 times and you have moved off the edge of the field and over the embankment. With the integral gains turned on I flew it 6 times and the final flight landed within 8 inches of the original take off point.
Its cool when everything works. I also fired up the helicopter flight data review system and it just reminds me how much detail work has gone into this project: (The position hold accuracy plot is uninteresting as the errors are so small the lines look straight, so here I show the auto takeoff.)
Click on the picture for a bigger view and you can figure out where I test ;-)