Design of a Novel Loosely Coupled Parallel Structural Upper Body Exoskeleton
Xinhui Tian, Xin Zhou, Bin Xie
AI summary
Problem
Existing active upper-body exoskeletons rely on tightly coupled serial structures that cause poor wearing comfort, limited muscle coverage, and restricted workspace, hindering long-term industrial use.
Approach
The authors developed a 6.9 kg parallel exoskeleton connected only at the waist and elbow, using a circular waist rail and five-bar linkage to concentrate heavy actuators near the body's center of mass while preserving natural spinal and shoulder mobility.
Key results
- 6.9 kg prototype with 78% of mass concentrated near the waist
- Kinematic analysis confirms exoskeleton workspace exceeds human elbow range
- Sub-millimeter trajectory tracking accuracy (<10⁻³ m) validated
- Wearers perform extreme postures without spinal constraint or motion restriction
Why it matters
Provides a comfortable, high-workspace assistive device for workers in manufacturing, logistics, and construction facing long-duration heavy lifting and overhead tasks.
Abstract
Exoskeletons, as wearable human–robot collab- orative 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 (6.9 kg). 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.