Sequential Composition of Walking Motions for a 5-Link Planar Biped Walker

Work by the authors published elsewhere addressed the problem of designing controllers that induce exponentially stable, periodic walking motions at a given fixed speed for a 5-link, planar biped robot with one degree of underactuation in single support. The key technical tool was the hybrid zero dynamics, a 1-DOF invariant subdynamics of the full robot model. Further exploiting the features of the hybrid zero dynamics, this paper provides an additional control feature: the ability to compose such controllers in order to obtain walking at several discrete speeds with guaranteed stability during the transitions. This feature affords the construction of a feedback controller that takes the robot from one exponentially stable walking motion to another while providing local stabilization and disturbance rejection.