Limbless Locomotion: Learning to Crawl with a Snake Robot

Robots can locomote using body motions; not wheels or legs. Natural analogues, such as snakes, although capable of such locomotion, are understood only in a qualitative sense and the detailed mechanics, sensing and control of snake motions are not well understood. Historically, mobile vehicles for terrestrial use have either been wheeled, tracked or legged. Prior art reveals several serpentine locomotor efforts, but there is little in the way of practical mechanisms and flexible control for limbless locomoting devices. Those mechanisms that exist in the laboratory exhibit only the rough features of natural limbless locomotors such as snakes. The motivation for this work stems from environments where traditional machines are precluded due to size or shape and where appendages such as wheels or legs cause entrapment or failure. Example environments include tight spaces, long narrow interior traverses, and movement over loose materials and terrains. Several applications, including industrial inspection and exploration of hazardous environments, compel serpentine robots. This research develops a general framework for teaching a complex electromechanical robot to become mobile where sequences of body motions alone provide progression. The framework incorporates a learning technique, physical modeling, metrics for evaluation, and the transfer of results to a snake-like mobile robot. The mechanism and control of a 20 degree of freedom snake robot is described and multiple gaits are demonstrated including novel non-biological gaits. This research furthers the design and control of limbless robots. Ó 1997 by Kevin Dowling We shall not cease from exploration And the end of all our exploring Will be to arrive where we started And know the place for the first time Acknowledgments Research is hard but involves great joy as well. The greatest of joys has been working with the people here at CMU. An observer might have thought I was working alone-but the critical mass of people here in the Robotics Institute meant that I could always find the help and encouragement on all issues. Red-Friend, mentor, and force of nature. Thank you Red. Hans Moravec-Once upon a time, Hans hired yours truly, an eager but inexperienced undergrad, to help build his robots. Hans always has a fresh perspective, new insight, and a wonderful way of looking at things. I will dearly miss the discussions. Mike Blackwell-Friend and officemate of fifteen years, Mike understands the combination of hardware and software better than anyone I know and has been an invaluable help in answering a …