Senin, 12 Oktober 2009

Definition of Insanity....

Definition of insanity: Doing the same thing over and over and expecting different results.

Clearly we don't think we are doping the same thing, but the results are really similar....

Drive 4 hours, camp, setup test, fly abort, break the vehicle, driver home 4 hours, fix vehicle, lather rinse repeat.

We should have the vehicle back together tonight. We have fabricated a new version of the the part in the gimbal mount we broke, but we still need to fabricate a brace so it won't break again.

We failed to record data on the last flight, so almost no useful information from the test.
(The error was a tired operator error, not a fundamental problem)
I've spent the morning changing software so data will be recorded automagically without any operator intervention, in 3 places, on the ground station PC, on the telemetry box, on an SD card in the vehicle, just to be redundant.

Looking at what data I do have, several things are clear.... proportionally it looks like the gimbal system needs a lot more differential correction than the vanes did.

The system seems to be a lot more sensitive to every thing being level to start with, the vane system just plain ignores tilts of up to 15 degrees, does not even cause a noticeable start up transient. This gimbal vehicle seems to want to start out with a large transient.

On a spherical vehicle its actually really hard to be sure that everything is lined up level.
The IMU is level, the motor is dead level vertically, but I'm sure I have a center of mass offset for the partially full fuel tank. Again the vanes vehicle just ignored the center of mass offset when flying with the permanganate tank.

I'm not a big believer in software only simulations, I like to build real world analogs and test those, this may change my mind. For a long time my todo list has had a hardware in the loop simulator on the list, ie simulate IMU and GPS inputs to the computer, measure the actual valve and motor positions and use these to run the simulation. This will probably be my winter project.

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