Design of a Humanoid Shoulder Complex Emulating Human Shoulder Girdle Motion Using the Minimum Number of Actuators

Abstract

This paper describes a design for a humanoid shoulder complex that replicates human shoulder girdle motion. The goal here is to use the minimum number of actuators to keep the mechanism as light as possible to help ensure that a humanoid is not too top heavy. The human shoulder girdle has two degrees-of-freedom (DOF), which means the minimum number of actuators is also two. The proposed mechanism is a novel parallel platform with two DOF that acts as a pointing mechanism. As the mechanism is articulated the end-effector moves, which results in contraction or elongation, mimicking the natural motion of the human shoulder girdle. A parallel platform was chosen because of the inherent rigidity and a large workspace is not necessary. The mechanism presented here was chosen because of its simplicity and ability to track human shoulder girdle motion. Motion studies were conducted to collect data representing human shoulder girdle motion, which was used to optimize the mechanism for tracking human shoulder girdle motion as closely as possible. A second optimization was performed to ensure that the mechanism avoids singularities throughout its entire range of motion. The results show that this design closely replicates human shoulder girdle motion and is well-suited for use as a humanoid shoulder girdle to increase the range of motion for a humanoid arm.