Attack of the killer freestyle SKI-BOT

Back to Contents of Issue: November 2001

Don't run for the hills just yet. Even though the Freestyle Ski Robot may be "killer," it isn't at all dangerous -- as long as you're not standing in the wrong place at jump time.

by Matt Cox

After 11 years in production and approximately JPY6 million, the obvious question is: Why would anyone want to build a freestyle skiing robot? The answer, according to the robot's creator, Keio University professor Kazuo Yoshida, is quite simple: dynamics.

Yoshida's focus is on creating robots that can move in the vacuum of outer space without using rockets or jets. Spacecraft normally use rockets or other sources of thrust to rotate, move, or spin themselves, because in space, there's nothing to push against (which is why no one can hear you scream). He realized that when flying through the air, a ski-jumping bot would experience a frictionless atmosphere similar to that in orbit -- a perfect situation for testing an intelligent device that could also move sans thrusters.

The result is a flying bot which, when airborne after a ski jump, can manipulate the momentum from lift-off to initialize a back flip while, at the same time, create enough momentum to perform a 360-degree lateral twist. But how does the little mechanical fella do it?

It's sort of similar to when a cat falls upside down from a rooftop. When kitty finally lands, its feet will be pointing towards the earth. What is difficult to figure out (apart from how to teach the little pest not to pee on the carpet) is how fur-ball hacking felines generate the momentum required to flip over. Kitty's trick relies on a law of physics known as the conservation of angular momentum; when a falling cat spins its tail in one direction, its body rotates in the opposite direction, which puts it in a feet-down orientation. Similarly, helicopters have tail rotors -- to keep the cab from spinning in the direction opposite that of the rotors.

While Yoshida has not robotically mimicked the movements of a falling cat, he has created a robot that, through a delicate series of movements, is able to provide itself the momentum required to complete a full spinning back flip in the span of one second. He explains that the ski ramp provides the momentum for the back flip, but the robot moves automatically to counteract the flip so as not to blow the landing and spread high-tech robotic shrapnel across the lab. Unlike the flip, however, the twist is induced entirely by the robot itself and has been the most difficult element of the project -- apart from convincing the university that season tickets to Akakura Onsen Ski Resort are a necessary research expense. The dynamics of this self-induced twisting motion, Yoshida believes, may help in the creation of robots that can move quickly, efficiently, and independently in outer space.

Shin Furukawa, strategic advisor for personal robot developer Tmsuk, agrees that Yoshida's experiments may indeed prove valuable in the development of automated spacecraft. "Although we haven't seen it yet, it is possible that the ski robot, by flipping backwards and twisting while flying through the air, could provide information that will lead to the creation of robots that can move freely in outer space."

The current ski-bot shares the lab with three predecessors and an odd assortment of relatives, including a nearly complete robotic space arm, a team of four Soccer-bots (who placed third in the Robotic World Cup), an unfinished robotic bike that will hopefully ride itself this autumn, a Tetris-playing bot that helps researchers understand hand-eye coordination, and two balancing bots that provide hints on the ups and downs of egoism and altruism. Unfortunately, you won't be able to buy any of these at your local robo store; they were created solely for research purposes, and there are no plans at this point to commercialize any of them.

As Yoshida presented demonstrations of his robotic conquests, he said today's robots would never be fully adopted by humans because, much like unintelligent slugs, "they lack any real means of expression" (see J@pan Inc's interview with AI guru Hideto Tomabechi, page 3, October 2001, for a dissenting view). Even if robotic expressions remain a challenge for the decades to come, fortunately for us, a snowboarding robot appears to be well within reach! @

Matt Cox is editor and writes the "Chairman of the [snow]Board" column at, an online guide to skiing in Japan. He has dabbled in investment banking in his spare time.

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