A Bioinspired Lightweight Wrist for High-DoF Robotic Prosthetic Arms

The prosthetic arms generally face several challenges: most critically, they are not lightweight to the users and do not provide full degrees of freedom (DoF) for the arms. In order to address this problem, we propose a novel bioinspired lightweight and high-DoF wrist for prosthetic arms. The proposed robotic wrist is lightweight, albeit more dexterous by simplifying the human wrist structure into a two-row ellipsoid joint and implementing novel ligament routing. The two-row ellipsoid structure effectively reduces the weight of the full-DoF wrist within sufficient ranges of motion required for its mobility. A novel routing-by-ligament tunnel allows for the employment of stiffer ligaments in a compact structure, thereby securing the full DoF of the wrist without compromising its load capacity. We conducted a musculoskeletal simulation to show that the bioinspired wrist helps to increase the energy efficiency of the entire upper limb. Our experimental results demonstrated that the proposed wrist greatly reduces the weight of the entire prosthetic arm while improving its range of motion, tensile stiffness, and the control performance.