Robotic Exoskeleton With Mechanically Implemented Kinematic Synergy for Quadrupedal Gait of Rats

This study introduces a novel kinematic synergy-based exoskeleton designed for gait rehabilitation studies in rats. The exoskeleton assists all three hindlimb joints of the rat (hip, knee and ankle) while ensuring proper interjoint coordination and the natural quadrupedal posture. This assistance is realized through a 2-DOF bar mechanism that emulates the biomechanics of rats. Engineered to be compact, lightweight, backdrivable, and sufficiently powerful, the proposed system minimizes physical stress on the animal while allowing a wide range of assistive forces to be applied. These features are achieved through a combination of a cable power transmission system and direct-drive motors positioned outside the exoskeletal structure. The desktop experiments demonstrated that the exoskeleton could precisely replicate the rat's kinematic gait patterns and remain backdrivable whether powered or unpowered. The feasibility of gait assistance was further confirmed in an anesthetized rat, where synergistic gait patterns were observed between the joints. Hence, the system holds the potential to enable controlled comparative neurorehabilitation studies in rats. These studies can help unveil neural recovery mechanisms and design optimal exoskeleton control strategies for rehabilitation in humans.