Compass Gait Revisited

It has been established that a suitably designed unpowered mechanical biped may \walk" down an inclined plane all by itself and eventually acquire a stable periodic gait. The characteristics of this periodic gait (e.g., velocity, time period) depend on the geometry of the biped and the slope of the plane. The energy to maintain the periodic motion comes from the conversion of the biped's gravitational potential energy as it descends. In this paper we present an active control scheme for biped robots which mimics the stable periodic motion of a passive biped on an inclined plane. Imagine a biped robot moving on a horizontal plane with a compass gait. If we apply the necessary joint torques in such a way that it induces the precise changes in the states of the robot, its resulting behavior will resemble that of the autonomous motion of a passive robot on a desired slope. We conjecture that the modiied behavior of this actively controlled robot will possess the periodicity and the stability of the passive motion.