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A three-link planar model of a biped is studied in the frontal plane. When this model is subjected to certain on-off constraints, the forces of constraint are derived as functions of the system state and the input, and can be shown in a simple block diagram. Linear state-variable feedback is designed to stabilize and decouple the system for small motions about an equilibrium state. The motion of this biped is implemented as a sequence of state transitions between stable equilibrium states. Ramp state and input references are used to guide the biped system from one equilibrium state to the next. Single-support postural stabilization and side step and return motions were investigated by computer simulation in order to evaluate the effectiveness of this control strategy.
Goddard et al. (Tue,) studied this question.