For projects like this, take a serious look at the Octopus hydraulic linear actuators:
http://octopusdrives.com/products/octaf1212lam12 This model has 12VDC reversing polarity input for the drive (30 amps) and a 12VDC clutch input with a fairly low current draw. And I’ll be curious to see how this project turns out. David — this would be a great drive for you to use as a below-deck replacement. Fred Street -- Minneapolis S/V Oceanis (1979 C&C Landfall 38) -- on the hard in Bayfield, WI :^( On Jan 21, 2014, at 8:57 AM, David Paine <paineda...@gmail.com> wrote: > 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> 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 € > instead of min 1000 € ... 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 > > _______________________________________________ > This List is provided by the C&C Photo Album > http://www.cncphotoalbum.com > CnC-List@cnc-list.com > > _______________________________________________ > This List is provided by the C&C Photo Album > http://www.cncphotoalbum.com > CnC-List@cnc-list.com
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