Active Cord Mechanism with Oblique Swivel Joints and Its Control

Abstract

Active Cord Mechanism (abbreviated as ACM) in this paper is the newly proposed bio-mechanical element with long and slender body and executes flexible winding motion such as a snake being in the natural world. The authors have been interested in ACM and have been making successive investigations on its mechanisms and control problems as a locomotor and a manipulator. In this paper some fundamental considerations as to the problems to realize the industrial applications of ACM are performed and shown that the designing of effective actuator system is crucial. As a results of these considerations, a mechanism named “Oblique Swivel Joints” is proposed to be suitable especially for ACM as a locomotor. The control problems of oblique swivel joints are then analyzed by tensor calculus, and basic control principles are derived. To verify these considerations an ACM mechanical model with oblique swivel joints is constructed. The mechanical model is 1.6m in length, 61mm in diameter and consists of 16 segments. It is controlled by micro-computer. By this ACM model, 3 dimensional posture formation and its successive transformation is demonstrated. The ACM model also demonstrates smooth locomotion like a centipede or milliped on a rugged surface or over a ditch by installing powered wheels along the ACM trunk and supplied cooperative control of the rotation of the wheel and the bending motion of the ACM trunk. Thus the authors believe that this study showed one of the ways for ACM to be utilized in various industrial applications.