ON IMPROVING BIPEDAL WALKING ENERGETICS THROUGH ADJUSTING THE STIFFNESS OF ELASTIC ELEMENTS AT THE ANKLE JOINT

Abstract

Impact at each leg transition is one of the main causes of energy dissipation in most of the current bipedal walking robots. Minimizing impact can reduce the energy loss. Instead of controlling the joint angle profiles to reduce the impact, which requires a significant amount of energy, installing elastic mechanisms (with adjustable stiffness) on the robots structure is proposed in this paper, enabling the robot to reduce the impact, and to store part of the energy in the elastic form and return it to the robot. The conceptual design of an adjustable stiffness artificial tendon is proposed which is added to the ankle joint of a bipedal walking robot model. Simulation results on the stance phase demonstrate significant improvements in the energetics of the bipedal walking robot by proper stiffness adjustment of the tendon as compared to using a single linear spring. A controller based on energy feedback is designed to automatically adjust the stiffness of the tendon. Computer simulations illustrate improvements in performance of the energetics of the bipedal walking robot in consecutive walking steps while the stiffness of the tendon is adjusted properly.