Mobile robots that would resemble earthworms have been proposed for use in exploring remote, hostile, or inaccessible terrain surface and subsurface environments. This class of robots would be a special case of a more general class of proposed small, lightweight, relatively inexpensive exploratory robots. Biomorphic explorers would exploit the emerging technology of biomorphic controls and advanced actuators. They would achieve motion by use of simple electronically or photonically controlled, flexible advanced actuators instead of conventional motors with complex drive trains. The robots would carry advanced microsensors for measuring or detecting specific objects or substances. Animallike combinations of mobility, adaptability, fault tolerance and a limited capability for "learning" would be achieved by integrating the actuators with very-large-scale integrated (VLSI) circuits that would implement neural-network and/or genetic algorithms.

The proposed earthwormlike robots would be flexible in the sense that they would be foldable in segments. The first several segments at one or both end(s) of each robot would generate motion. These segments would be covered with hinged plates connected to interior actuators (see figure on page 12b). Upon command, the interior actuator in each segment would shorten or lengthen the segment, causing the plates to buckle outward or to move inward to straighten, respectively. A wave of shortening/buckling versus lengthening/straightening, resembling the peristaltic motion of an earthworm, could be generated by sending coordinated, sequential contraction and expansion commands to the actuators in the segments. By this action, the robot could move along the surface or burrow beneath the surface of terrain. The direction of travel could be reversed by reversing the sequence of buckling and straightening.

Shortening/Widening and Elongating/Narrowing motions of the segments would be timed to generate an overall peristaltic motion like that of an earthworm.

Special-purpose microsensors could be housed in one or more end or middle segment(s). The tips on the end segments could be sharpened to facilitate penetration of soil. Alternatively or in addition, the tips could contain sensors and/or mechanisms to collect samples.

The design of the robot, including the details of the mobility features and the choice of sensors, would be specific to the intended application. For example, an earthwormlike robot might be designed to probe earthquake rubble to find missing persons and animals. The sensors for this application could include a miniature active-pixel-sensor video camera, a temperature sensor, and microspectrometer for detecting carbonates, water, and other chemical signs of life.

This work was done by Sarita Thakoor, Kim Quillin, Alex Fukunaga, John Michael Morookian, and Adrian Stoica of Caltech for NASA's Jet Propulsion Laboratory. NPO-20266


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Motion Control Tech Briefs Magazine

This article first appeared in the June, 1998 issue of Motion Control Tech Briefs Magazine.

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