Frankenpilot the Homemade Autopilot
- Created on Wednesday, 19 October 2011 00:04
- Last Updated on Tuesday, 29 April 2014 20:58
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I built my own tillerpilot for my sailboat.
I'm calling it the Frankenpilot because it's big-- as Victor Frankenstein says
"As the minuteness of the parts formed a great hindrance to my speed, I resolved, contrary to my first intention, to make the being of a gigantic stature..."
And because it is made from things lying around:
"The dissecting room and the slaughter-house furnished many of my materials; and often did my human nature turn with loathing from my occupation, whilst, still urged on by an eagerness which perpetually increased, I brought my work near to a conclusion."
I had, laying around in my garage:
- A broken analog tillerpilot (sensor was broken, but drive works)
- An aircraft grade inertial measurement system (Microstrain 3DM) for a compass/gyro/tilt sensor
- A GPS car autopilot board with an atmel microcontroller and LCD
- A 12V speed controller
- A LORAN navigator that came with my boat, which had a nice LCD and keyboard in a waterproof case.
My friend Bryan made a nice autopilot for his boat, and he told me his LQR control design scheme. He also gave me his dynamic model, so I could design my own feedback controller. His model was based on data from sailing his Ultimate 24 Max, a much lighter boat than Firebolt, but I figured it would be close enough to get started.
So with all this, how could I not build my own autopilot?
I used it in the 2011 Vallejo 1-2 race, singlehanded to Vallejo. It worked pretty well (I came in 3rd in my division on Saturday). It had worked better in my earlier tests when it had not been so windy, it proved a bit unstable in the bigger breeze of the race. I will be adjusting gains to fix this. I can choose from 10 different gain settings so I should be able to find something that works. The ram is also a bit slow, but I am not sure whether that is a showstopper or not at this point.
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