Volume 8, Number 6     November/December 2000

"Snaking" Around in Exploration

NASA engineers are developing an intelligent robot snake that may help explore other planets and perform construction tasks in space.

The robot serpent, able to independently dig in loose extraterrestrial soil, smart enough to slither into cracks in a planetÕs surface and capable of planning routes over or around obstacles, could be ready for space travel in five years, NASA engineers predict.

"The snake will provide us with flexibility and robustness in space," said Gary Haith, lead "snakebot" engineer at NASA Ames Research Center at Moffett Field, California. "A snakebot could navigate over rough, steep terrain where a wheeled robotic rover would likely get stuck or topple over."

An intelligent robot snake is being developed that will be able to independently dig in loose extraterrestrial soil, is smart enough to slither into cracks in a planet's surface, and is capable of planning routes over or around obstacles. Photo provided by NASA Ames Research Center.

"One of our first steps was to make a simple mechanical test snake, and we constructed it in less than a day thanks to previous work at other labs," said Haith. "It is a direct model of a 'polybot' developed by Mark Yim of Xerox Palo Alto Research Center in Palo Alto, California, with whom we are cooperating. We have slightly different electronics in our version."

The test snake has a wire that carries communications and power to and from the computer brain. The several identical hinge-like modules are attached together in a chain, and off-the-shelf hobby motors in each of its hinged segments cause it to move. Each of the motors takes a signal from the snakeÕs main computer brain.

"Our first test robot does what we tell it to do, no matter what the results are. If it comes to an obstacle, the robot will continue to try to go over it, even if the task is impossible," he said. "We made the first, simple robot because we wanted a working snakebot in a day or two, a robot that would help us to think about how a snakebot could and should move."

"Robotic serpents can inch ahead, flip themselves backward over low obstacles, coil and side-wind," Haith said, "while future work could enable the snake to become a mast or a grasping arm. A rover would need to have a dedicated mast and arm that would cost extra weight, money and time," he said.

"A snakebot is not as good at some jobs as other robots, but you get a lot
more robot for the weight and the money," he said. "But it's hard to tell
the snakebot what to do. It is a complex robot that must operate independently, possibly far from Earth. Work on our second snakebot is aimed at making it capable of independent behavior."

"The key part of what we are striving for in the second snakebot version and beyond is sensor-based control in which the robot uses its sensors to decide what to do," Haith explained. "Each hinged section includes a microcontroller, a motor, electronics and gears to get the hinge to move to certain positions."

The snakebot will have a main computer that will tell the small computer in each segment what to do in a planning sense. The tiny computers in the segments could provide "reflexes" that take care of simple but important jobs.

"In the next couple of months, we hope to simulate the snakebot in a computer program so we can automatically develop computer routines that can control the robot," Haith said.

"We hope to write software that allows the snake to learn on its own by experience," he said. "Some lessons we hope it will learn are how to crawl from soft to hard surfaces, and how to go over rough surfaces that have rocks. We even hope to show that it can climb scaffolds and go into cracks. These abilities would help the robot look for fossils or water on another planet."

According to engineers, the snakebot can save spacecraft weight because the snake-like design enables the robot to do many tasks without much extra equipment. One advantage of the snake-based design is that the robot is field-repairable. "Other benefits could include: the snakebot can crawl off a spacecraft lander and doesn't need a ramp, its moving parts can be sealed inside artificial skin to avoid exposure to the outside environment and the robot can still function, even if one joint freezes," said Haith.

For more technical robotic snake information, please visit the NASA snakebot Internet site at: http://icwww.arc.nasa.gov/ic/snakebot/

For more information, contact Gary Haith at NASA Ames Research Center. E-mail: haith@ptolemy.arc.nasa.gov Please mention you read about it in Innovation.

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