O'Reilly Network: RoboGames 2005

This past weekend, our nascent robot masters descended on San Francisco State University to compete in the 2005 RoboGames. They came as 350-pound combat robots, dripping with skulls and jagged spinning wheels; as matchbox-sized autonomous sumo bots gently pushing each other out of rings; as improvised Lego Mindstorms mix-ins; as devoted line followers; daring ribbon climbers; beautiful dancing androids; and even light eaters. But mostly, they came with their human servants, who watched and chatted and compared notes, all hoping to take away more ideas for further developing their charges.

Robotics enthusiasts are in many ways the hardware hackers par excellence--they begin from scratch, or from scraps, and seek to replace and exceed human function. They harden, they iterate; but they have a much harder time sharing than other geek communities.

Upping the Bus Speed on Robotics

"There's no easy way to show someone how to rebuild a gear box online. It's just not as easy as sending an email or working on code together." says Simone Davalos, the event's co-coordinator. "It's slower because it's actually physical." In general, there have been few preexisting traditions of knowledge sharing between robotics communities. The autonomous robot designers haven't learned from the experiences of the combat robot contestants. The hobbyists and the academics may not realize when they are solving each other's problems.

That was Robotics Society of America president David Calkins' inspiration for founding the RoboGames, bringing together communities of disparate builders, and giving them a chance to learn from each other. "[Roboticists] tend to over-specialize. The AIBO soccer people are excellent with software, the combat people are excellent machinists, the sumo people are really good at sensors. The goal was to get them talking to each other."

In theory, the aim of the RoboGames is for teams to compete in a variety of challenges, for the usual gold, silver, and bronze awards. In practice, each event works as a showcase of the many scattered sub-disciplines, to the delight and surprise of their fellow experimenters, who may never have seen anything that close up outside of their field before.

And, of course, it's also a revelation to the general public, who get to see giant robots, made famous by TV shows like Robot Wars, gnash in the combat robot arena. And while those combat bots (complete with flying sparks and a monster-truck-pull-worthy announcer) grabbed a huge amount of attention from spectators, other subtle and complex non-combat events showed off parallel worlds of robotics.

Some events, like balancing on two wheels and following a line, are simple to understand and highly focused, if not as easy as they sound. The "line slalom," where a robot tracks a black squiggly line across a white floor, may seem like reinventing the wheel. But this sort of event is still nuanced enough to appeal to aspirational hobbyists. With a field as young as robotics, hobbyists can still hope to find small ways to invent a better wheel--and can always be counted on to find cheaper ways to invent the wheel.

David Calkins sees events like the line slalom as partly "about inspiring kids to become robotics engineers."

One of the youngest event participant, Reut, eight years old, became interested while building robots with her father. Her entry was her fourth robot, an edge detector that could be a reasonable precursor to the line slalom. Tirion, age ten, built his towel-carrying robot for the classic hacker's reason--to scratch his own itch. He didn't like getting cold between getting out of the pool and getting his towel, so he built a robot that could eventually bring him a towel. It's not quite ready for poolside, but it took silver in the Mindstorms Open.

Other events, like the Firefighting event, combine many different robotic skills in a highly formalized manner. They are often as hard as they sound.

Firefighters Made of Simple Parts

Firefighting is an event that is both aspirational and that ties a number of different functions into one robot. The Firefighting Challenge was originally set up by Trinity College in Connecticut, with the hope of creating a class of autonomous robots that could seek out and extinguish home fires. The task is a simple one for humans, and very troubling for robot: navigate though a model maze house without touching the walls, find a candle, and put it out.

Ted Larson is a veteran robot builder and active member of Silicon Valley's HomeBrew Robotics club (a loving tribute to the original Homebrew Computer Club, famously the birthplace of the Apple computer). He took the silver medal winner in the category, and explained what was required for a firefighter.

Most people start out with a kit and modify it for firefighting, but Ted Larson and his partner Bob Allen constructed their own generic robotic platform, which they've built into different robots over the years.

They use a set of three boards together: a motor control board that handles optical encoder feedback from the drives with a closed loop control to control it.

A sensor board coordinates data from two infrared controllers at 45° and 135° (angled to give some advanced data about the angle of the walls just in front of the robot). The sensor board also takes in data from a front-mounted sonar unit that tells the robot how far away the wall is (bumping a wall in the Trinity challenge is a penalty). Finally, there's a pair of line detectors pointing at the floor. These allow it to see the lines that mark the entrances to rooms, as well as the fire circle and the starting circle.

The last part of Larson's basic board kit is the CPU board, which pulls in data from the other boards, and spits out decisions to the motor.

Many of the decisions about what the sensors are seeing is farmed out to processors on the other boards, which come to an agreement using a subsumption architecture, the distributed decision-making architecture invented by Rodney Brooks in the 1980s. But at the top, the CPU board's Microchip PIC CPU (a 18F6621) uses a traditional maze-solving routine to map its way to the candle.

As maze-solving algorithms go, Larson chose the simplest. His firefighter uses right-hand wall following. The strategy works for the competition's standard maze--except for one room. That room thankfully didn't come up for Larson.

All of this is tied together over an I2C bus, the cheap two-wire serial bus used wherever good (but stingy) sensor systems are found. If you've ever read the temperature of your PC's CPU or fan speed, for instance, there's a good chance you've used SMBus, a variant of the I2C built into many modern motherboards.

The advantage for Larson of having a standard kit is that he can quickly improve his system for specific tasks. One extra board in his setup provides his robot with some specific firefighter skills. The board carries a 2kHz tone sensor, which launches the robot when a sound simulating a fire alarm goes off, and a Hamamatsu omnidirectional fire sensor (an off-the-shelf commercial unit that detects the specific wavelength of light a flame emits). Precise location is managed with an Eltec pyroelectric sensor, a point-sensitive device that can tell if the fire is right in front of it. The board sweeps the pyroelectric sensor around to locate the exact direction of the fire, then activates a simple relay for turning on and off a fan mounted to the front of the robot.

Larson's FlameOut is the very model of a modern competing robot. Simple, cheap, and straightforward at every layer, it builds up to become quite the complex beast. Altogether, it has ten CPUs working in coordination--a complete autonomous firefighter robot.

Clever, but not quite clever enough. The firefighter gold winner was 12-year-old Tony Pratkanis, also a HomeBrew Robotics club regular. His modified Grandar AS-M robot, lovingly known as "Solenopsis invicta" (named for a red fire ant), had both left- and right-wall following, giving it just the edge needed over Ted Larson's Flame-out.

Stairway to Heaven

Many software efforts have been accused being a solution looking for a problem, but some robotics engineers pride themselves on working on solutions to problems they hope exist soon. The ribbon climbing event, in which contestants try to built tiny robots that can climb a six-meter ribbon only 30mm wide, is a perfect example of the infectious optimism inherent in the RoboGames.

Ribbon climbing doesn't lead to the most sophisticated of autonomous robots--in fact, this year's gold medalist was largely a construction of piano wire and a drinking straw--but it seeks to solve one of the most novel of problems at the RoboGames, or indeed in robotics: the logistics of traveling up a carbon nanotube space elevator into orbit.

As simple as these little robots are, the challenges they face are uniquely tricky. Allow your robot to list to one side, and the ribbon can bunch, sending your robot back to earth in a hurry. Indeed, ribbon climbing is a ballet of balances, between weight and power, the friction to hold on against the friction blocking you from climbing, and a host of other artificial restraints that make the contest more complex and, hopefully, more applicable to the real world, including a remote transmission requirement and a five-second pause with automatic restart.

Nick, the builder of the first space elevator robot, has a safety lock built in. "In case [the robot] loses power, it has a ratcheting system that makes its own weight push down on the ribbon," effectively locking it into place. While not a contest requirement, Nick feels that this kind of a feature would be more practical in the real world. "Some people bend the cable, but I don't, because I don't think that's how it would work."

The contest winner, the drinking straw/piano wire affair, flapped a giant solar wing groundward, where its operators shined six high-power flashlights up at it. It raced up the ribbon in 25 seconds, including their five-second pause. It was so different from a super-heavyweight combat robot, it was hard to believe that these were, technologically speaking, the same species.

David Calkins was happy watching these disparate groups rub elbows. Some of the newer events began to bridge the cultural chasms that have plagued robotics in a more obvious way. The SRS Robo Magellan, a sort of mini DARPA Grand Challenge scoped to a university quad rather than a vast tract of southwestern desert, attracted university teams that rarely find themselves competing against or talking to the hobbyists.

Exhausted after three days of running the event, and many other intermingled conversations, Calkins still has enthusiasm to chat cheerfully about a combat veteran he had spotted who has returned home to build a human-like Robo One, and a delicate little sumo. Ideas have been shared; designs have interbred. Calkins has brought his robotic future a little bit closer.

Quinn Norton co-writes the ambiguous blog, runs a community co-op server, makes Yixing teapots, and writes about technology. For Quinn, every day is Take your Daughter to Work Day.

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RoboGames 2005 Robotics Community Descends on San Francisco

Upping the Bus Speed on Robotics

Firefighters Made of Simple Parts

Stairway to Heaven

RoboGames 2005
Robotics Community Descends on San Francisco