Hi David
Am 21.01.2014 15:57, schrieb David Paine:
Hi Peter,
I built a homebrew below deck autopilot for my C&C33 a couple of years
ago using a linear actuator, a mechanical clutch, a H-bridge-like
serial power controller from Pololu, an arduino, a transreflective
serial LCD display, four buttons, and most important of all, a digital
compass with serial communication (NMEA 0183) operating at 10Hz which,
along with a sparkfun gyro (15 degrees/sec) provides heading
information. I bout everything from ebay and probably have $250 and
untold hours invested) The programming is fairly easy with arduino
since there is a PID controller library available (use two, one for
the positioning of the actuator, the other for correcting for the
course error (the difference between the intended course and the
present heading.
I've used my autopilot on many long solo trips including one 80 m
mile offshore run with 20 kn wind directly astern and a large swell
off the quarter (during which I was able to sleep for four hours as
the system was so stable.
Hints: Forget using GPS (or wind) alone to set the course you need
much faster response time and that is why you need a 10 Hz heading
signal. I thought about using a Kalman filter but soon learned that
Kalman filter math is serious juju and was very glad to have stuck
with PID control -- we only have two degrees of freedom its not like
it's a quadracopter! The worst part of my system as it stands now is
the mechanical clutch to engage and disengage the actuator -- one day
I will find a hydraulic actuator which will allow a solenoid to
disengage the actuator. Raymarine actuators have an electromechanical
clutch which is also nice but consumes more current than I like.
Also, try to use components with serial communications protocols --
these will have on board filtering and make the whole exercise much
easier.
Best,
David
On Tue, Jan 21, 2014 at 2:24 AM, Colomba <colo...@peter-gottwald.de
<mailto:colo...@peter-gottwald.de>> wrote:
Good day
I`m wondering if there is anybody who want to build a DIY
autopilot? If so, it would be interesting to discuss/combine ideas.
In the moment my idea ... and what I`ve done so far is following:
- Controll unit with a raspberry pi
- language Python (because I really do not know C to handle this
properly)
The idea in the moment is to use this year the old wheel pilot
(Navico) as steering unit. If the controll unit will work fine, I
will change the steering unit next winter and will mount a linear
drive under deck.
What I`ve done up to now ...
I took the code of FishPi autopilot as basic to change to the
things which I think are usefull.
For time being I integrated a compass/magnetrometer/accelerometer
module, called cmps10. It`s cheap and doing it`s job.
For GPS signal I`m using a simple USB GPS mouse to figure out
Lon/Lat/speed/course
... not done yet ... integrate a reader for wind direction. On
board I have the NASA clipper instruments and will read this datas
via Atmel microchip, connected to the controll system via I2Cbus.
Atmel Afinity 1327 Chip is programmed and working, but up to now
no test if it`s working with the NASA clipper instrument, due to
the fact, mast is down for winter... so I have to play arround
first to test it on board, but ... it`s cold outside, so I`m still
waiting.
Rudderangle, just working, with a potentiometer and signals
collected by GPIO pins of raspberry pi.
Route planing .... FishPi provide the idea of integrating routes
in gpx format. I think that idea is ok for an autonomus vehicle,
but I do not like that idea. I`ve tested to run opencpn and FishPi
parallel on the raspberry .... and it works, so I take the signal
from opencpn for heading to next waypoint via UDP and can use opencpn.
For output, Ive integrated a motor controll via SDA network, which
should work with a PA with the wheel unit. Not tested yet.
There are a lot of things to do to get everything working nicely.
- define sailing situation with no go areas (i.e. downwind or app
+-38° head wind)
- define a "learning tool" to define rudder gain vs heeling and
acceleration, my idea is to create a simple database and to store
real life datas.
- implement a kalman filter or a complementary filter (which I
prefere for time being)
- of cause ... to find a nice housing and screen to have the stuff
mounted at wheel also to sea seamap at wheel
One may say, hey, you can by this stuff, exactly what you want ...
correct. But first of all, the hardware will cost me as DIY
project about 100 EUR instead of min 1000 EUR ... the other thing
is, it makes fun to create the own platform.
So, if anybody is interesting to join this project, he/she is
wellcome ;-)
best regards
Peter
C&C34 Colomba
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