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Aside from the dissected caterpillar on the table, there is just one other completed model, but it is inert, having pulled a muscle, as well as bits of squirmy this and that. The research, which is financed by the W. M. Keck Foundation, “is very preliminary,” Dr. Trimmer admits.
The researchers have gotten a wave to propagate across a robot’s body; that wave picks up the feet in a way that already resembles the foot motion of a real caterpillar. By the end of the year, they hope to have robots capable of full locomotion that emulate the action of the caterpillars, he said. The puzzle of coming up with computer code to coordinate the movements, they suggest, will be greatly accelerated using the rapid trial-and-error approach that, in the world of computing, is called genetic algorithms.
They see a day when the cheaply built machines — less than a dollar apiece, Dr. Kaplan predicts — could be crammed into a canister and shot into a minefield. The hollow bodies would contain a simple power source and mine detectors; the caterpillars would wriggle across the terrain at random, stopping when they detect a likely mine. “There’s no need for high speed,” Dr. Kaplan said. “Slow and steady is fine.”
The team suggests the caterpillars could similarly be used in hazardous, hard-to-reach spots in nuclear reactors and spacecraft. They also see a role in internal medicine as crawling probes and sensors, a prospect that patients might find difficult to accept, but which might eventually help doctors navigate some of the body’s trickier passageways.
In trying to reproduce the caterpillar, the Tufts researchers are taking part in one of the biggest trends in robotics and locomotion studies, which are increasingly taking inspiration from the world of biology. Joseph Ayers of Northeastern University has created an artificial lobster. Ian Walker of Clemson University has a robotic arm that draws its inspiration from the elephant’s trunk and the octopus’s arm. There are robotic salamanders, snakes, cockroaches, fish and geckos.
“It’s a hot topic,” said Auke Jan Ijspeert, head of the Biologically Inspired Robotics Group at the Swiss Federal Institute of Technology. He created the “salamandra robotica” as a way to prove theories about how a salamander makes its twisting course. “I’m basically amazed by nature,” he said, “and how impressive animals are at solving the problem of locomotion control.”
Dr. Ijspeert called the Tufts project “very exciting, very new.” At the same time, he pointed out, animal models can only go so far. He tells his students, “You should not aim at blindly imitating nature.”
Evolution, the engine of development, is brilliant but not necessarily efficient, he said. “The biological solution is always a little bit messy — it’s based on previous systems,” he said. Working without precedent, he said with a touch of hubris, a researcher can shape a more elegant solution than nature has.
That blended approach helps to guide researchers at the Information Sciences Institute at the University of Southern California, where the “Superbot” can configure itself to squirm like a worm, crawl like a turtle, roll like a tire and more. Their work is financed in part by NASA, which wants robots for future missions that can get around in any number of ways. “Wheels are a marvelous invention, but they have their place,” said Peter Will, a U.S.C. researcher. Bicycling on sand is hard, he said, while walking on it is easy.
The U.S.C. institute has another layer of natural influence, said Wei-Min Shen, the director of the institute’s polymorphic robotics laboratory: communication among robots that is inspired by hormones. “Because there’s no fixed brain, we need a signal that will circulate within the system,” he said. Like Dr. Ijspeert, Dr. Shen says nature can be a bit limiting. When he has to get up to write on a whiteboard, he says, he thinks, “If I can reconfigure myself and take off my left arm and connect it to my right arm, I can do so without standing up or leaving my chair.”
Robotics researchers talk like that.
The road ahead could be far longer and more difficult than it seems today for the Tufts researchers, said Dr. Walker of Clemson. While expressing enthusiasm for the project, he cautioned that soft is hard. When he embarked on a project to create the flexible robotic arm more than five years ago, he had hoped to stick with soft materials. But “it’s very hard to engineer with all-soft components,” he said. “We had to make compromises along the way” to get the strength and force that the arm needed.
There were other challenges. Designing computer programs to operate the arm was something “we thought we would spend six months working out,” he recalled. “Two or three Ph.D. theses later, we finally understood the problem. Not that we had solved the problem. We understood the problem.”
“So,” he said, “I’ll be interested to see how closely, when all is said and done, the Tufts group are able to meet their goals.”
Dr. Trimmer said, “I’ve got a lot of confidence it will work.” And besides, he added, “If we don’t make the exact robot that you and I are discussing, what have we got? What we’ve got is an entirely new approach to motion control.”