Optimization of Mass and Stiffness Distribution for Efficient Bipedal Walking

Abstract

Abstract — Energy-efficient control of bipedal walking robots requires both minimization of mechanical energy losses (often mainly due to impacts) and the use of natural oscillations in a mechanism to minimize actuator torques (as shown by research on passive dynamic walking). In this paper, we discuss how these aspects can be analyzed and changed using mathematical models of the dynamics, as opposed to using only engineering intuition and experimental results. First, we describe how the loss of energy due to impact can be influenced by the mass distribution and posture of a robot. Second, we discuss a numerical optimization method to find how the natural oscillations in the mechanism can be influenced by using optimal springs that minimize energy requirements from the actuators. We use a simple planar three-link robot as an example to illustrate the ideas. Index Terms — legged locomotion, minimum energy control, mechanical energy storage I.