Postural stability of two biped models via Lyapunov second method

In biped locomotion, postural stability about vertical stance is of practical significance. Three problems related to postural stability are discussed here. Estimates of the region in the vicinity of vertical stance, where the biped model with linear feedback is stable, are derived. A method of designing nonlinear feedback is developed in which the combination of linear and nonlinear feedback provides a larger region of stability. Nonlinear feedback is utilized to simulate human-like motions of bowing and bending from the hip. Computer simulations for the double inverted pendulum and bipeds with stiff knees are presented.