A computational technique for designing a physically realizable robust dynamic gait for a planar biped robot is developed. Firstly, a feasible set of gaits was constructed to satisfy the periodicity of the biped locomotion. Then the concept of dynamic, stability margin is introduced based on the robustness of a gait with respect to the external disturbances. Using that margin, we can assess the robustness of each dynamic gait in the feasible set. It is found that the parameter, called foot strike time margin, representing the readiness of the foot strike has a close positive correlation with the dynamic stability margin. We obtain a robust gait with respect to the external disturbance by maximizing the foot strike time margin. The robustness of the optimal gait is confirmed by the behavior of the gait after application of linear impulse as well as by the examination of the largest eigenvalue at the perturbed state.
