Stuff related to MAV's (and UAV's) from a hobbyist's point of view. Info

First flight with my autopilot

Two weeks ago, I crashed my micropilot plane. Repearable, but I thought it might be a better idea to use an “easy” plane for the first tests with my autopilot. Also, the limited space available in my delta plane was an issue. And so I bought an easystar. The space under the canopy is very generous, which makes it easy for testing. I installed ailerons on it to make sure it would respond swiftly to my input on its roll-axis.

The first two flights were quiet a disappointment. Flying level posed no problem at all, but making coordinated turns was not as good as expected. Suddenly, I realised I was flying the easystar in 20km/h winds, while the plane only flies at – like 30km/h? Obviously, the pitching behaviour of the eastar when flying upwind or downwind is completely different. I suppose it was just a bad idea to try it in such high winds… Also, the autostabilizing behaviour of the easystar makes it a bad choice as a roll-stabilized plane.

In the late afternoon, when the wind fell between 5 and 10km/h, I did another test. And it was a success! The easystar flew nicely, no weird pitch behaviour anymore, and coordinated turns (and coming out of) were a success! Yiha!

Right now, I just updated my PID code. Now it is much more general. However, this “clean” approach made the update rate drop from 50 updates per second to 41 updates per second. So I was wondering: If you had an autopilot system, would you mind sacrificing performance for clean, readable code? And what about using integer math instead of floating point math (and thus losing the correct “scientific” units)?

No need to worry just yet: my dsPic runs at 7.8MHz, and its capable of 80MHz :-)

9 January 2008, 20:37 | Link |