Analysis and Preliminary Design of a Passive Upper Limb Exoskeleton

This article reports the analysis and preliminary design of a passive, wearable, upper limb exoskeleton to support workers in industrial environments in a vast range of repetitive tasks, offering an effective strategy to reduce the risk of injuries in production lines. The system primary purpose is to compensate for gravity loads acting on the human upper limb. The proposed exoskeleton is based on 6 Degrees-of-Freedom (DoFs) kinematics with 5-DoFs for the shoulder joint (two displacements plus three rotations) and 1-DoF for the elbow. Gravity compensation is implemented with passive elastic elements to minimize weight and reduce cost. A detailed analytical tool is developed to support the designer in the preliminary design stage, investigating the exoskeleton kinetic-static behaviour and deriving optimal design parameters for the springs over the human arm workspace. By defining specific functional requirements (i.e., the user's features and simulated movements), computationally efficient optimization studies may be carried out to determine the optimal coefficients and positions of the springs, thus, maximizing the accuracy of the gravity balancing. Two different solutions for the arrangement of the elastic elements are investigated, and obtained results are validated with a commercial multi-body tool for some relevant movements of the user's arm.

Automated summary

This article presents an analysis and preliminary design of a passive, wearable upper limb exoskeleton that aims to support workers in various repetitive tasks in industrial environments, thus effectively reducing the risk of injuries on production lines. The exoskeleton's main objective is to compensate for the gravity loads on the human upper limb, achieved through passive elastic elements to minimize weight and cost. The authors developed a detailed analytical tool to aid the designer in the preliminary design stage, investigating the exoskeleton's kinetic-static behavior and deriving optimal design parameters for the springs over the human arm workspace. Computational optimization studies can then be carried out to determine the optimal coefficients and positions of the springs, maximizing gravity balancing accuracy. Two different arrangements of the elastic elements were investigated and validated using a commercial multi-body tool for relevant arm movements of the user.