Abstract
This paper addresses reactive generation of step time and location of biped robots for balance recovery against a severe push. Key idea is to reformulate the balance recovery problem into a tracking problem for "hybrid" inverted pendulum model of the biped, where taking a new step implicitly yields a discrete jump of the tracking error. This interpretation offers a Lyapunov-based approach to reactive step generation, which is possibly more intuitive and easier to analyze than large-scaled or nonlinear optimization-based approaches. With the continuous error dynamics for the divergent component of motion (DCM), our strategy for step generation is to decrease the "post-step" Lyapunov level for DCM error at each walking cycle, until it eventually becomes smaller than a threshold so that no more footstep needs to be adjusted. We show that implementation of this idea while obeying physical constraints can be done by employing a hybrid tracking controller (together with a reference model) as our reactive step generator, consisting of a simple DCM-based continuous controller and a small-sized quadratic programming-based discrete controller. The validity of the proposed scheme is verified by simulation results.
Reference details
Pages: 3504--3509