The image is startling: a three-ton unmanned machine moves slowly across a rugged landscape, scanning the terrain with infrared eyes. But instead of moving on tracks or wheels, the huge robot walks on six legs. For almost 20 years researchers around the world have been trying to develop such walking machines. Now a 65-member research team at Ohio State University in Columbus is close to translating that science-fiction image into reality. Indeed, next November the team’s adaptive suspension vehicle (asv)—a sixlegged, 17-foot-long computerized robot—will begin undergoing field trials at Ohio State’s Transportation Research Center. The first walking machine designed for outdoor use, the $5million project is funded by the U.S. defence department’s Defense Advanced Research Projects Agency (DARPA). The reason: vehicles such as tanks cannot be used in extremely rough terrain, but the ASV is designed for such conditions. Declared professor of mechanical engineering Kenneth Waldron, one of the team leaders: “This is the first fully self-contained outdoor machine.”
The ASV, developed under Waldron and team leader Robert McGhee, professor of electrical engineering, is powered by a 90-hp Kawasaki motorcycle engine. The eight-foot-high machine’s 17 computers—each capable of containing 128 kilobytes, or more than one million bits of information—are programmed to coordinate leg movements. As well, they receive information about the surrounding terrain from the ASV’s infrared “eyes”—sensors connected to a radar system—and pressure sensors in the machine’s feet. Researchers are also trying to develop a sonar system for the ASV’s legs, which would sense obstacles and transmit the information to the computers. Although the vehicle still needs a human driver to control direction and speed, researchers are now beginning to develop the hardware and software necessary for a fully autonomous ASV. In fact, McGhee says that in next year’s field trials the machine will operate with limited autonomy, and manual control will be necessary only in case of mechanical malfunction.
The sci-fi vehicle may be able to stride such fragile ecosystems as arctic tundra with little damage to vegetation
The ASV project dates back to the mid1960s, when Raj ko Tomavic, a professor of control engineering at Yugoslavia’s University of Belgrade, visited the University of Southern California and asked McGhee, then an assistant professor there, whether it would be possible to build a four-legged, computer-controlled walking machine. McGhee responded by constructing such a machine —the first of its kind. But because the 100-lb vehicle had only four legs, it lacked stability. As a result, McGhee began working with a six-legged design after moving to Ohio State in 1968. Indeed, funded by the Washington-based National Science Foundation, the second effort, the OSU Hexapod, walked under controlled conditions in 1977.
That 300-lb vehicle was the first to be equipped with electronic sensors that calculated its distance from the surrounding environment and helped direct it over obstacles. Said McGhee: “The machine demonstrated the feasibility of rough-terrain locomotion by a walking machine with the operator providing only speed and direction commands.” Still, those early devices were not selfcontained, and the driver steered the machine with an external joy stick. But the results so impressed DARPA that in 1979 the agency asked McGhee to design a larger machine that could move at eight miles an hour in rough terrain and carry payloads weighing at least 500 lb as well as an operator.
According to Waldron, the ASV will be capable of walking through forests, bogs, desert sand and up and down steep hills. As well, the machine will be able to cross ditches up to nine feet wide and obstacles up to seven feet high. Scientists say that the military applications of the ASV are obvious. Said Waldron: “The army estimates that about half the earth’s land surface is not accessible to wheeled or tracked vehicles. They are viewing this as a transportation system for the other half.”
The scientists say that they have not really studied the machine’s possible applications. But they say the ASV’S primary application will be in nonmilitary situations. For one thing, a legged vehicle can move over fragile ecosystems—such as arctic tundra—with a minimum of damage to vegetation because its feet make less contact with the ground than the tracks of a tank. Waldron also says that because the ASV will not damage the root systems of trees, it could be used in the forestry industry instead of tractors. And modified ASVs could be useful in high-risk situations —such as inside nuclear reactors.
One problem that the Ohio State team had to overcome was developing software to co-ordinate the ASV’s leg movements. To that end, they turned to natural models for clues. Indeed, Keir Pearson, professor of physiology at the University of Alberta in Edmonton, studied the movements of locusts because they are also hexapods. But although the four-month-long study yielded important information about how insects co-ordinate their six legs, the locusts were too clumsy to provide a proper model. Explained Pearson: “Insects will use their bodies for support —if they fall, it’s no big deal. That’s out of the question in a machine.”
Waldron emphasizes that the ASV will not be a fighting machine because it cannot be equipped with sufficient armor. As well, it would not move quickly enough to evade any incoming rockets. But the Ohio State researchers have already started designing a more agile, four-legged machine capable of moving at speeds of up to 20 miles an hour. Under a DARPA subcontract, researchers at the Environmental Research Institute of Michigan in Ann Arbor are now studying the walking abilities of goats —among the most agile quadrupeds —in order to gain useful information. McGhee says that in two years the Ohio State team will test the concept by removing the ASV’S middle pair of legs. In four years he says he expects to have finished a machine that will prove the viability of four-legged vehicles.
Meanwhile, the research team has not yet tested the ASV on a walk, although the scientists are now checking the vehicle’s leg movements. Later this month the ASV’S standing ability will be tested, and early next year walking trials are scheduled to begin. Although McGhee says that important pieces of equipment-such as some form of directionfinding device—still have to be developed before the machine is capable of operating without a human driver, DARPA has already committed another $3.5 million to the project. And McGhee adds that the future promise held by research into artificial intelligence—the so-called fifth generation computers that will be able to “think” for themselves—will have a tremendous effect on walking machines. Declared McGee: “Two decades ago I realized that a walking machine under autonomous electronic control would require a very high order of computing power. Today that goal is within reach.”
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