I have started to build an APM controlled sail boat.
The hull
The hull is based on a IOM boat called Goth (Free plans here). It is built with balsa strips and then glassed on both the inside and outside. Keel blade and rudder are made with balsa cores and a carbon fiber shell. The bulb is 3.5 kg lead. It is designed to weight 4.2 kg when finished.
The wind vane
The wind vane is built around the magnetic rotation sensor chip as5045. With a magnet placed just above the sensor it can detect the absolute angle of the magnet. The magnet can be seen below the ball bearing in the image below. The sensor chip measures just 5x5 mm and is embedded in epoxy. The wind vane and the sensor is placed in the tube and voila. A wind direction sensor with almost no friction and a total weight of less than 10 g. Total length is 10 cm.
I still need to figure out where to put the wind sensor. Since i have a rotating mast it is not a good idea to put it there unless i fit another rotation sensor on the mast.
The wind vane is quite sensitive. It works at walking pace so hopefully it will work on the boat.
Mast
The mast and boom is made of a fiber glass fishing pole. the sail is made drawing film. It is made as an IOM sail and the sail area is similar to an IOM size two sail (main plus jib).
I have not decided how to control the sail. I can use a traditional sail servo or rotate the mast with an arrangement under deck.
Control
The boat will be controlled using the APM hardware and sensor libraries.
The plan is to take it step by step:
- Manual RC-control
- Manual RC-steering with automatic sail control
- Heading and/or Wind angle hold.
- ...
All comments and ideas are welcome!
/Magnus
Comments
Can you send me the wiring diagram for the as5045.. Any information on how you interfaced it with the UNO would be helpful too. I am really new at this I am sorry I am asking such basic questions.
Thank you Dermot! I think a wingsail could be a good solution especially if you want a rugged solution for extended autonomous missions.
Nice hull, Magnus. For comparison, my Microtransat entry is here: http://blog.beogabeag.org/
I'm planning on using a wingsail rather than a traditional sail, just for reliability.
I used the serial interface. Add me as a friend and i will PM you some test code.
/Magnus
That is a cool sail configuration. My solution is really simple. If you look at the image of the mast you can see a carbon fiber rod with two ball bearings. The bearings fit in a glass fiber tube that is fixed in the hull. The tube is about 10 cm long. the mast is held in place by the tight fit between the bearings and the tube.
Sail control is traditional with a sail winch and a line connected to the boom. Not fancy but it works for now. Another solution would be to put a rotation sensor on the mast and connect a motor directly to the mast , but i could not think of a way to do that waterproof in a simple way.
/Magnus
Hi Timo,
I just did my first sea trials this weekend. The IOM is a really good sailboat! My sail worked ok, but there is definitely room for improvements. It would be really interesting to see your design.
Maybe crossing the Baltic would be a good long tern challenge for a robotic sailboat!
/Magnus
That will be the exiting part! I have started to design a preliminary model for control with the following parameters:
Control signals
- Target awa (apparent wind angle)
- Target heading
Sensor Inputs
- AWA +/- 0-180
- Heading 0-365
- COG 0-365
- heel angle or rate +/- 90
- turn rate, for quick compensation
- AWS (Apparent Wind Speed) (future)
- Rudder angle (future)
Output
- Rudder angle
- Sheet angle
Dependencies
- Sheet angle is dependent on AWA, heel and maybe turn rate
- Rudder angle is dependent of Target AWA- AWA, Target heading - Heading, heel, and maybe turn rate
that makes sense. now how we determine that set of rules to program the ardunio.
so you would have ended up with two inputs the vane could be the master while the anemometer or tilt sensor could act as slave . like the vane will do the first set of inputs to angle the sail then depending on the wind speed the anemometer will send a second command like IF or ELSE command to overwrite the sail angle from the vane. like +/- 5%-10% to my guess on how much the boat is heeling over.
was wondering which would be appropriate anemometer or tilt sensor/gyro
mostly is trial error base on manual controlling of the boat. you have to test different wind direction and sail angle each to determine the best angle for optimize speed. I don't know if this is appropriate but I its ideal to experimented on a sailing simulator first.
http://www.hangsim.com/vs/
once you got the data its time to replicate the program on the ardunio
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