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--- projects:mihab:glider [2007/04/15 10:41] – laurenceb
+++ projects:mihab:glider [2008/07/19 23:33] (current) – external edit 127.0.0.1
@@ Line 6: / Line 6: @@
+===== Mark #2 Glider ====
+With the glider used in flight 1 completely trashed, something new will be needed ;-) Having considered a 2 axis stabilised rigid glider (probably using thermopiles and an ARTF off ebay) and also a parafoil, I'll probably go for a semirigid rogallo. These are very stable and forgiving on control inputs, and also easy to make, and foldable for transport to the launch site. Parafoils also meet these criteria, but readily avaliable parafoil kites are harder to adjust and test unless you're good at sewing and have a nice high platform to test from.
+ Judging from the previous test flights, a "PIDR" loop with SIRF2 would almost certainly be adequate for a rogallo, but I'll try and be on the safe side (money and time allowing) and go for a rate gyro ( off spark fun) and kalman loop. This should be able to give an extremely accurate and responsive heading value for the PID loop. Temperature compensation of the gyro will be essential, but a peltier cooler system has been constructed for that purpose, and should be capable of -30 centigrade (-14 reached so far). One problem will be small steps in the Kalman filter output with each new GPS heading, which would mess up the D term in the PID controller unless it is turned off each time this happens. (i.e. turned off for one iteration of the Kalman filter)
+ A second, and more serious problem is the GPS lag, approx 1.1 seconds for a sirf2. Solving this may mean that the correct error treatment cannot be used in the kalman filter, but more work is required. Running the filter back and forwards to pick up each GPS heading is not an option as there will be insufficient recources (ie SRAM and clock cycles).
+ Here is an overview of the planned system, it would appear that there is a lot to do, but much of the work has already been done for flight #1, so it may not be as hard as it appears :-)
+{{projects:mihab:evil_plan_to_take_over_the_world.png|}}
 ===== Rogallo experiments =====