Thursday, 20 September 2012

Data from last test.

Flight Data:

We have been going through the log from the test last sunday and picked up on a problem, The PI values not updating as fast as they should be. The stabilisation loop runs at 31Hz (same speed as the solenoids pulse at) however the PI values were updating slower. Bart figured out that we (or more specifically I) was not using the Arduino pid library properly. The library has two ways of updating itself, Automatic and Manual. Auto mode works like it sounds, the library updates values itself. Quasi-conservatelly, in manual mode you call an update command yourself. I was looking at an example which used auto mode but also called updates manually so that how I did it but apparently the manual updates were not doing anything.

Here is Pitch, Pitch PI output and Z acceleration for the longest test.

Despite the PI values not updating at the speed they should be the PI looks like it has some sort of control. I think that the rocket must have run out of peroxide because the deceleration ocors partway into the test. Either this of the steady state thrust (after the initial spike) was not enough to counter gravity. Either way the program did a good job to stabilise the rocket after it landed on the string because dropping it by hand on an angle (you can see it was at 0.6 rads when it hit) makes it go everywhere. Possibly I am just seeing what I want to see..... It could just be that the the rocket just bounced on the test stand....

Sam and Bart excited for the test!

The Improved Quick Disconnect:

My laser range finder and interface board came today. I nearly got pulled over by the police on the way back from collecting it at the post office because I was measuring the distance to the car in-front as I was driving..... excuses I thought of post-scare included... "Officer, anyone could see I trying to keep a optimal distance from the car in-front"and "What am I doing?... Well clearly I am calibrating my speedometer". If I have some spare time before sunday I will mount it on the rocket so we can get some data.

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