RHex: A biologically inspired hexapod runner

RHex is an untethered, compliant leg hexapod robot that travels at better t han one body length per second over terrain few other robots can negotiate at all. Inspired by biomechanics insights into arthropod locomotion, RHex u ses a clock excited alternating tripod gait to walk and run in a highly man euverable and robust manner. We present empirical data establishing that RH ex exhibits a dynamical ("bouncing") gait-its mass center moves in a manner well approximated by trajectories from a Spring Loaded Inverted Pendulum ( SLIP)-characteristic of a large and diverse group of running animals, when its central clock, body mass, and leg stiffnesses are appropriately tuned. The SLIP template can function as a useful control guide in developing more complex autonomous locomotion behaviors such as registration via visual se rvoing, local exploration via visual odometry, obstacle avoidance, and, eve ntually, global mapping and localization.