Development of a Low Inertia Parallel Actuated Shoulder Exoskeleton Robot for the Characterization of Neuromuscular Property during Static Posture and Dynamic Movement

The purpose of this work is to introduce a newly developed exoskeleton robot designed to characterize the neuromuscular properties of the shoulder, including intrinsic and reflexive mechanisms, during static posture and dynamic movement in a 3-dimensional space. Quantitative characterization of these properties requires fast perturbation (>100°/s) to separate their contribution from that of voluntary mechanism. Understanding these properties of the shoulder control could assist in the rehabilitation or enhancement of upper limb performance during physical human-robot interaction. The device can be described as a new type of spherical parallel manipulator (SPM) that utilizes three 4-bar (4B) substructures to decouple and control roll, pitch and yaw of the shoulder. By utilizing a parallel architecture, the 4BSPM exoskeleton has the advantage of high acceleration, fast enough to satisfy the speed requirement for the characterization of distinct neuromuscular properties of the shoulder. In this work, the prototype is presented, along with an evaluation of its position accuracy and step response. The development and preliminary testing of the 4B-SPM exoskeleton presented in this work demonstrates its potential to be a useful tool for studying the neuromuscular mechanisms of the shoulder joint.