Optimized Design for Cable-Driven Shoulder-Elbow Exoskeleton Robot

Abstract

The cable-driven exoskeletons have the advantages of low inertia and simple structure, and they are widely applied for human augmentation and rehabilitation. However, they have limited workspace and tension efficiency because of the unidirectional nature of the cables. The limited performance affects the human-robot interaction and leads to potential danger. The workspace and tension efficiency can be optimized by conventional methods, which are adjusting the cable attachment points and increasing the actuators. But the workspace still cannot cover the human joint space of activities of daily living, and the efficiency is also not high. This paper analyzed the specific application for shoulder and elbow joints rehabilitation and proposed a dynamic adaptive structure. This design can increase the workspace and improve tension efficiency greatly. The dynamic compensation control strategy is designed for the optimized system. Besides, in order to reduce the effects of compliant elements (e.g., cables or Bowden cables) between the actuators and output, and to improve the force bandwidth, we designed the distributed active semi-active system composed of the geared DC motor and magnetorheological clutches, which has low output inertia. The related experiments are carried out based on several healthy subjects. The results verified that the exoskeleton with the dynamic adaptive structure has a large workspace covering the activities of daily living joint space, high tension efficiency, and high force bandwidth, which is beneficial for the safety and comfort of human-robot interaction during rehabilitation training.