Sunday, January 20, 2019

Rocket Control Surfaces: Grad School Procrastination

I built a ton of model rockets as a kid and always wanted to make a proper stabilization system. In high school I made one, but didn't have the mathematical foundation to understand the dynamics, linearization, etc required to make it work well. I suppose now I do. I whipped this hardware up in a matter of an hour or so, and with the magic of 3D printing, voila:

I had a bunch of micro servos laying around and decided to design it all around them. I am using the horns for fastening the fins to the servos. The horns are epoxied in place under the fins, while a screw is brought from above to attach to the servo shaft. There are better ways of doing this, but this was quick and easy.
Here is the fin that I designed. I didn't really do much math other than a back-of-envelope torque value. I will do some system ID later on down the line.
I also printed some Falcon 9 grid fins just for fun to see how they looked.

After testing all the servos with a Pololu Maestro (by far my favorite PWM testing platform), I found that the servos have decent 200ms-or-so tracking delay and low tracking bandwidth. I`ll simulate this in MATLAB later with vehicle dynamics to see how much of a problem this becomes when it comes to simple stabilization.

Ultimately I would like to put together a little flight computer PCB and implement some interesting control and guidance algorithms like proportional navigation.

Of course, for the sake of ITAR and other formidable parties, I will not be sharing any of the source code, CADs, designs, etc. I will simply discuss my experimentation.