The improved passive dynamic model with high stability

The self-adjusted limit cycle gait, integrating continuous swings with intermittent heelstrike collision, can make a completely uncontrolled and unactuated passive walker walk stably down a gentle slope, only powered by the gravity. However, this natural and high energy-efficient gait is also highly susceptible to its specific variable parameters and any slight perturbations. Thus, reasonable parameter configurations and proper feet shape are significant for the robot to attain better stability and disturbance rejection, which determine whether the robot can walk stably and how fast the walker recovers from external disturbances. Because of the continuity of disturbances and the periodicity of the gait, the robustness is determined not only how much the disturbance is, but also, how fast the robot can recover from a disturbance to be capable of next disturbance rejection in order to continue to walk. Thus, the local stability is focused on in the paper. Moreover, the effects of parameter variation on the local stability and characteristic of gait of passive walking models are discussed. Mechanical parameters of model are carefully tuned. The simulation results show that the model could endure larger continuous disturbances and recover faster than ever discovered.