Compliance in gait synthesis: Effects on energy and gait

The role of compliance in walking controller synthesis is explored in this paper. Gait is designed for a simple biped with compliant legs using the concept of hybrid zero dynamics. Simultaneous optimization of gait and leg spring stiffness and optimization of gait at a fixed leg spring stiffnesses is carried out. Different cost functions based on energy are considered. The influence of compliance on gait and the influence of the measure of energy on optimal compliance are investigated. It is shown that minimum actuator energy consumption is obtained if leg stiffness is subject to optimization along with gait parameters. Sum of actuator work and spring work is higher than in optimized stiff-legged gait. Depending on the choice of cost function, fundamental different gait characteristics and optimal stiffnesses are obtained.