Design of a Novel Loosely Coupled Parallel Structural Upper Body Exoskeleton

Abstract

Exoskeletons, as wearable human–robot collaborative devices, can effectively reduce muscle fatigue caused by prolonged material handling and overhead tasks. However, most existing active exoskeletons adopt tightly coupled serial structures, which generally suffer from insufficient wearing comfort, limited muscle coverage, and restricted workspace. To address these issues, this paper presents a novel loosely coupled, parallel upper-body exoskeleton (6.9kg). The proposed exoskeleton is connected only at the waist and elbow, providing assistance not only to the small muscle groups of the arms and shoulders but also to the larger muscle groups of the waist, back, and chest. Moreover, heavy components of the exoskeleton (approximately 78% of the total mass), such as actuators are located near the wearer’s waist, which places the center of mass close to the human center of mass, improving comfort and control reliability. To validate the feasibility of the design, kinematic models of both the exoskeleton and the human upper body were established. Analysis showed that the end-effector workspace of the exoskeleton exceeds that of the human elbow. Prototype experiments were conducted, allowing the wearer to perform arbitrary postures without constraining spinal motion. This indicates that the exoskeleton holds potential in work assistance scenarios such as long-term heavy lifting and overhead work.