Locomotion of Closed Loop Robot Using Stiffness Distribution Control

Abstract

This paper proposes a new method of locomotion control named “Stiffness Distribution Control (SDC) ” to realize various locomotion of a closed loop robot with mechanical softness on the ground. SDC directly defines a reference stiffness coefficient at each hinge by a SDC string, which represents distribution of stiffness coefficient. This simple method does not need costly calculation at all and thus is suitable for controlling closed loop robots. We build a closed loop robot “BIYOn” with newly designed variable stiffness hinges. SDC is experimented on the robot and effectiveness of SDC is verified in practice. A two-stage systematic optimization approach for SDC strings, which is composed of “hinge-wise optimization method” and “collective descent optimization method, ” is also developed to obtain efficient locomotions. The former is the method focused on functions of each hinge in desired locomotion, and the latter is to optimize the solutions based on local solutions ontained in the first stage. This approach does not require a large amount of computation to get global optimal SDC strings. By this approach, we succeed in obtaining a fast and smooth rolling motion and a sudden stopping motion.