Study on 3D Active Cord Mechanism with Helical Rotational Motion

Abstract

Active Cord Mechanism is a mechanism in which the joints are coupled in many numbers in series, just like a snake. Typical studies of the propulsion of the Active Cord Mechanism focus on the 2D winding movement, like a snake. But Active Cord Mechanism may generate very efficient locomotion by introducing 3D motion. This paper proposes a new kind of propulsion principle for the underwater Active Cord Mechanism, in which each articulated body segment creates distortion motion, while keeping the whole body in a helical shape. The helical body will revolve around the center axis of the helices due to the forces generated by the distortion motion, and progress along the center axis of the helices. This paper also discusses about the design and control of a new mechanical prototype to realize a hermetic underwater 3D Active Cord Mechanism. Finally the effectiveness of the proposed principle for the underwater Active Cord Mechanism is evaluated by experiments using the developed robot.