I have been developing an open source autopilot
program to use gps
, magnetometer and wind
sensors to steer the boat. Currently initial tests in wellington harbor using tilt-compensated magnetometer prove successful but extensive testing is needed. Total hardware
cost is ~$120 but it has about 2000lbs of pull which I'm afraid might break something (I overengineered it for my boat) It uses 1 amp without load and up to 10 when it is pulling hard (and can move hard over in just over 1 second) This is a brushless rc outrunner ($25 on hobbyking.com) driving a 120:1 planetary gearbox
from a truck winch
. The motor
that came with the winch
had too high of a starting current
. Hopefully I can reduce cost and make weaker ones.. I have two more weaker drive units I have not yet tested.. one can drive a wind vane
, the other is based on a broken autopilot
Currently it uses a simple filter which provides critical dampening.. so it counter steers before it hits the right course so it wont oversteer, and it automatically adjusts the two gains over time to achieve this.
I am pondering the viability of commercializing this. What do people want? What will they pay for? Actually any comments related to this type of work are appreciated.
My initial plan was to offer a waterproof box which has 2 wires going in and 2 wires going out and can handle up to around 30 amps. If you need more power you could just replace the motor
controller as they are made in all sizes and extremely cheap
. It may be required to have a separate box for the magnetic sensors as they are negatively affected by the high current wiring
(this is the current setup) An internal hall sensor can detect motor stall (in less than 1/20th of a second) and an internal buzzer can provide some feedback on various error conditions.
Then _you_ have to take either a broken autopilot, linear actuator, electric
winch, hydralic pump etc.. and connect it to the wires, and rig the mechanical parts
to make it move your rudder
. Brushless motors would be supported as this is what my prototype uses and it is no extra cost or difficulty. Also optionally usb can be connected to control with opencpn
to give gps steering
and waypoints etc, otherwise just compass
Then for those who can solder, a much cheaper kit version (thru hole soldering only) could be assembled in a few hours for a much reduced cost, however the user would have to perform a rather arcane calibration procedure themselves to make the magnetic sensors correct. They can calibrate automatically over time.. but I currently know of no way to get better than 2 degrees accuracy in all orientations automatically on a moving boat without prior careful calibration on land.. this trick only works to keep them in tune. It may be possible to get around this with redundant sensors but this is complicated (have not worked it out) and would require 3 $25 sensor boards instead of just 1.
An optional wind vane
sensor could be connected.. I built one already using an rc servo.
To take a look at the code and/or algorithms
Since all the design would be open, you would be free to modify and mix and match hardware
as required for whatever application, eventually support gyros for racing
applications, or for people who need to surf the swell with their spinnaker
at 12 knots. In fact I have a lot of future ideas not listed here because it would get too far off track.
I will post pics tomorrow.