Development and Characteristics of a Highly Biomimetic Robotic Shoulder Inspired by Musculoskeletal Mechanical Intelligence

This article provides a comprehensive analysis of the existing landscape of conventional and highly biomimetic robotic arms, highlighting a prevalent tradeoff between size, range of motion, and load capacity in current highly biomimetic designs. To overcome the limitations, this article undertakes an in-depth exploration of the human shoulder, focusing on the identification of mechanical intelligence within the biological glenohumeral joint, such as the incomplete ball-and-socket structure, coupling stability of humeroradial and glenohumeral joints, and the self-locking mechanism of the glenohumeral joint. These intelligent features can potentially enhance both the stability and mobility of robotic joints, all the while preserving their compactness. To validate these potential benefits, this article introduces a novel, highly biomimetic robotic glenohumeral joint that meticulously replicates human musculoskeletal structures, from bones and ligaments to cartilage, muscles, and tendons. This novel design incorporates the mechanical intelligence found in the biological joint. Through rigorous simulations and empirical studies, this article demonstrates that the aforementioned mechanical intelligences significantly enhance the flexibility and load capacity of the robot's glenohumeral joint. Furthermore, extensive manipulation experiments confirm the robustness and viability of the proposed highly biomimetic robotic arm. Remarkably, the presented robotic arm executed 46.25% glenohumeral flexion/extension, 105.43% adduction/abduction, and 99.23% rotation, and can sustain a payload of 4 kg, and open the door which requires a torque of over 1.5 Nm to twist the handle. Hence, this article not only validates the intrinsic mechanical intelligence identified in the deconstruction of the human shoulder joint, but also contributes a pioneering design of a new, highly biomimetic robotic arm, significantly pushing boundaries of current robotic technology.