Survey and Review

Abstract

A lot can be learned by observing how the lowly cockroach is able to maneuver its way in complex, rough terrain when foraging or evading threat. In this issue, Philip Holmes, Robert Full, Dan Koditschek, and John Guckenheimer provide a comprehensive review of how one models legged locomotion. They begin by analyzing the dynamics of a spring-loaded inverted pendulum. This simple system, referred to as a “template,” becomes a building block for modeling the motion of a six-legged creature. The authors provide convincing arguments as to why this dimension reduction approach is appropriate. The work draws on three areas of research: biomechanics, neurobiology, and robotics. Vast experimental evidence, some of which is reproduced here, also guides their investigation. This easily accessible article is also peppered with clearly stated open problems, whose solutions will no doubt give further insight into understanding the complex phenomenon of animal locomotion. Indeed, the review provides a well-marked road map for research in this fascinating field. The impact of the study described in this article is already enormous. Inspired by the understanding obtained from this modeling effort, one of the authors, Dan Koditschek, and his colleagues created an amazing six-legged robot. Aptly named RHex, it moves like an insect and has the ability to run through rough, hilly terrain with great ease.