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?"

Comments

URBI

[bobby1234]

http://www.urbiforge.com/ "URBI is a Universal Real-time Behavior Interface and gives you a simple but powerful way to control any robot or complex system like a video game, using a convenient and easy to use scripting language that can be interfaced with several popular programming languages (C++, Java, Matlab,...) and OS (Windows, Mac OSX, Linux). URBI is based on a client/server architecture, which give a great deal of flexibility. URBI includes powerful features compared to existing scripting solutions: parallel execution of commands, event programming, command tagging, dynamic variables,... Currently, URBI is used as well by academic research labs, the industry and by hobbyists."

Well, DUH!

[Anonymous Coward]

The first thing I would do to get a leg up in the competition would be to post the question to a technology website that garners millions of hits a day - a website that, more than likely, most of the robot boat-building teams are familiar with. That way, no one but me would have access to collective thoughts of hundreds of brainstormers.

approach

[belmolis]

I couldn't help noticing that the rules forbid interference with other boats' electronic equipment and colliding with other boats, but say nothing about the use of, say, cannon. :)

Re:approach

[Rakishi]

Well they may consider the cannot round to be part of the boat thus it hitting another boat being a "collision." On the bright side even if you do get disqualified for such an act the DARPA grant you'll get soon afterwards will probably be worth more than the competition prize.

Re:approach

[Xeirxes]

Forty years later, the ocean is still overrun by four-meter long robotic attack ships, who refuse to allow any ship passage.

Re:Don't know what you'll choose

[deniable]

Until someone gets to the Blue Waters of Death. Even better, this gives someone a chance to pirate Windows for real.

AI link

[SPickett]

Evolving neural network for sailing project http://annevolve.sourceforge.net/

Possible Architecture

[mechsoph]

PC (maybe mini-itx) running *nix talking via Ethernet/IP to a Netburner Microcontroller talking via CAN to several PICs/AVRs with some extra circuitry (amplifiers, voltage dividers, etc) to interface with the sensors and actuators.

There are PICs and AVRs that have ethernet, but the NetBurner is damn easy to use. They also have some micros with GPIO, ADCs, and maybe PWM generation, so it might be easiest to skip the 8-bit micros altogether. I don't have any affiliation with NetBurner; I've just used their product and was sufficiently impressed that I might voluntarily choose to use it again.

What we use

[jfim]

Our team(SONIA) is working on autonomous underwater vehicles and we are using Linux with Java for the AI part. For communication with actuators, we use the CAN bus, which is fairly common in the industrial automation and automotive fields.

There are CAN bus adapters that plug into serial or USB ports and there is Linux support for these. We're using one from Vector.

As for hardware, we use the Kontron JREX SBC with JFlex I/O boards to add the I/O ports we need(firewire and serial, mostly). Of course, if you're not cramped for space, you might go with something a bit larger.

I hope this helps, feel free to ask more questions.

Re:An OS for your system?

[greenguy]

Oh, sure, Linux can handle a USB port. But can it handle a USB starboard?

If it requires a driver and a Linux driver is available

Didn't you RTFS? It has to be autonomous. That means no driver.

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.

Re:but what *hardware* ?

[spinlight]

The quickest way that I know of to get your computer to talk to your motors is through a USB Data AcQuisition device (DAQ, for short). When we built a prototype ROV, we bought an off-brand China special for about $80 that had drivers for LabView. You will also need a motor controller. Some DAQs have Pulse Width Modulation (PWM) motor controllers built into them, but these are not cheap, in my experience.

Hook your DAQ up to your control computer (we used windows), and then your motor controllers to your DAQ. The power supply that powers the motors (12 V DC or more) goes into the motor controllers, and the signal from the DAQ goes into the motor controllers (USB is 5ish V DC, I think). The power to the motors comes out of the motor controllers, according to however you program it in Labview.

We used an Open Source Motor Controller (OSMC) that we built from parts.
We used the system to vary the speed to 4 motors on the fly, using a computer interface that accepted input from a mouse and keyboard (just like Half-Life... sorta).

Automation in Linux

[PtrToNull]

Having worked on development on robotic telescopes, both hardware and software, let me tell you that using Linux was not an easy choice. We had to narrow our search to vendors who explicitly support Linux, and even there, their support was flaky at best and we spent hours in troubleshooting the drivers before we got them to work. However, this exercise resulted in better support for Linux from the vendor, so it's a win-win situation. We opted for National Instruments for their excellent DAQ boards & LabView which are all supported under Linux.

For the control system, we used INDI, it's a powerful server/client control protocol that you can use to jump start your project within minutes. While it is geared toward astronomy, it can be used for any purpose.

Thoughts from an amateur sailor/hacker

[An dochasac]

• You're going to have to make the gear strong, waterproof, salt proof. With this short of notice you might consider a commercial autopilot/GPS with a serial interface to a computer which should be well sealed. If I were going to "roll my own" autopilot, I might consider utilizing a printer driver and mechanism but scale up the motors somehow.
• Most commercial autopilots can't tack upwind. Since the trade-winds and gulf stream are against you, you're going to have to figure out how to tack.
• You'll need a way to cut down sail. The simplest would be for the main and jib to be roller furling, but it's more difficult to have roller furling mains. Another option would be to use a tiny or heavily reefed main and have the jib/genoa be your main sail power. This sacrifices upwind performance for simplicity wind speed flexibility.
• A mechanism to measure tidal drift and correlate it with predicted high/low tides would be useful. A dumb GPS based servo will waste lots of time and wind trying to correct course for tidal drift when it's possible that 6 hours later it will waste time and wind trying to correct course in the opposite direction!
• If you wanted to be really smart, you'd try to measure and predict wind direction. For example, if you know a high pressure system is passing to your north, heading west to east, you should expect the wind to gradually clock around to the from northwest to northeast.
• "Length must not exceed 4 meters" but North Atlantic waves regularly exceed 10 meters so your boat is going to be thrown around and shaken a lot and it will need to reorient itself.
• You won't have lots of power to spare, so an efficient CPU and efficient OS will be necessary, a stripped down linux or qnx might work. For power and reliability's sake you might even consider something ancient, a 386 or 68000 on a

Re:In one word?

[Anonymous Coward]

I've already done this in April, and it works.

http://67.15.245.144/portfolio/navcom_ai/

You're welcome to contact me for info, or just grab the source code and schematics since it's all open. If you do contact me however, I've changed some code in the past two months that's slightly more efficient (it's on the Parallax website in the object exchange under Math AFAIK, if you can't find it, get a hold of me)

Matteo Borri mkb@libero.it