A hybrid walk controller for resource-constrained humanoid robots

Zero moment point (ZMP) preview controller is a widely adopted method for bipedal locomotion. However, for robots which are resource constrained or working in dynamic environments, simple reactive walk controllers are still favored as ZMP preview controllers have more control latency and are computationally more demanding. In this work, we present a hybrid walk controller that dynamically switches between a reactive walk controller based on the analytic solution of the linear inverted pendulum model and a ZMP preview controller that uses future foothold positions for more demanding tasks. The boundary conditions of center of mass (COM) state are considered in the optimization process of the ZMP preview controller to ensure a seamless transition between two controllers. We demonstrate the controller in a physically realistic simulations, as well as experimentally on a small humanoid robot platform.