Trans-Atlantic Robots

An anonymous reader writes "In the summer of 2008, teams from a host of countries will compete in The Microtransat Challenge with the hope of gaining the honor of having built the first autonomous sailboat to cross the Atlantic. The results of Microtransat 2007, a smaller scale preliminary race, were recently announced. The winner was the team from Austria; team RoBoat, for having completed 24 hours of autonomous sailing. I am strongly considering joining this competition before the year is out, and would appreciate any insight from the Slashdot community. The boats can be up to 4 meters in length, and therefore capable of carrying a full-sized onboard computer (operating system of your choice). Time is limited however, so I would like to avoid as many hardware issues as possible and get straight to the difficult problem of writing the AI. So how would you design a seamless interface between sensors and actuators to the high-level code?"

Re: Trans-Atlantic Robots

[CheekyBastard]

You may be better off asking people within the sailing industry or a well-heeled engineering team. On /. you'll likely see this devolve into a heated debate about which flavor of *nix is better and why.

Re:In one word?

[eggnoglatte]

For a realtime system? Surely you are kidding.

Re:let me guess...

[fractoid]

Alternatively, you carve a bunch of boat-shaped pieces out of the block of wood, and then assemble them. But that would be thinking laterally. ;)

"God Works in mysterious ways". "Shit Happens". Can anyone explain, obvectively, the difference?

Partitioning of responsibility. "Shit happens" is simple acceptance of the universe's imperfection. "God works in mysterious ways" lets you know that if anything good happens, God did it. Of course, if anything bad happens, you deserved it. If despite all the Church has done for you, you still don't think you deserved it, then it's a test of your faith.

Using Ethernet to control devices

[Animats]

There's something to be said for using 10baseT to talk to control devices. 10baseT has better noise immunity than RS-232 and 5V TTL encoder signals. We had trouble with big servomotor PWM noise leaking into encoder signals, and a low noise in analog signals, but the 10baseT worked perfectly, even when near the engine of our robot vehicle. Not only is it differential over twisted pair, there's checking and retransmission.

The trend is towards putting an Ethernet interface on the thing to be controlled, rather than bothering with translation to CANbus. We used Galil motor controllers, which talk TCP and UDP over Ethernet. They're OK, but you can get comparable functionality in a smaller and cheaper package now.

10baseT has a feature that's important here - the connectors have retention latches, and don't fall out. USB does not latch, which is a showstopper in an industrial or vehicle environment.

Something we found useful was encapsulating boards. Mask the connectors with masking tape, and spray with Fine-L-Kote, which seals the board against humidity and provides some mechanical protection. Inspect under ultraviolet light (the stuff is clear, but glows) to see if you missed anything.

AI might not be the difficult part

[Dr. Winston O'Boogie]

I am not convinced the AI is the difficult part of this. Developing a seamless hardware solution is very difficult, assuming it need to be very robust. The salty sea air only makes this harder on the hardware, especially the electronics. However good you think you can make the AI/software part, you might want to look around for someone that can do an even better job on the hardware side. I think (good-hardware + average-software) > (average-hardware + good-software) in the domain of this contest.

silly race, really.

[zippthorne]

Buy a commercial autohelm and feed its inputs with directions based on your gps waypoints and the local weather. You'll also need some kind of auto-main-sheet and auto-jib. Large yachts already have these. Heck, most cruise ships are already ocean-crossing robots. They don't even necessarily require the pilot's input for docking maneuvers anymore.

The trick, IMO, is creating a tacking plan based on your goals for the day, and knowing when to adjust it and when to just ignore local fluctuations.

Re:Using Ethernet to control devices

[Animats]

See Making Ethernet Work in Real Time [sensorsmag.com], from Sensors magazine. They show how to calculate the odds of delay exceeding a given value for a given network speed and loading. With a 10 Mb Ethernet, sending 1000 64-byte packets per second, you can be 99% sure there will not be a delay of more than 7 ms in 9 years. You can't load the network very much (5-10% is tops for a real time application). But the odds of an error are higher than the odds of a timing miss.

CANbus latency is only deterministic for the highest priority messages on the cable. Everything else is subject to nondeterministic delays due to preemption.

Re: Trans-Atlantic Robots

[pwolk]

The book "Robots op zee" (Robots at sea, P.W. Adriaans) deals with building a highly automated full-scale sailing boat to cross the Atlantic. Their first approach to control the boat was unsuccessful: it involved neural networks. The second approach was more successful, and involved expert systems in a cascading set-up, having a helmsman unit, a navigator unit, and a captain unit, a.o. The helmsman unit had windward and leeward defined in its internals, which proved by no means trivial. It is no project a pedestrian hacker would pull off in a few months. Another main hurdle for sailing oceans unmanned is the *robustness* of the ship's sensors: the ocean is a hostile place, and Adriaans is doubtful whether the sufficiently robust sensors are available at all. So (1)read the book, (2)have fun, and (3)good luck.