Joint Synergy-Based Rehabilitative Exoskeleton for Rodents

Abstract

During robot-assisted neurorehabilitation, the therapy protocol and the tuning of the robot assist parameters depend on the operator’s or the therapist’s experience, and the ideal intervention methods remain unknown. A major obstacle to investigating the feasibility of rehabilitation protocols and optimal assist parameters is the difficulty of conducting human research, therefore, to find the optimal intervention methods, investigative research based on animal tests is required. In this paper, we propose a rehabilitative exoskeleton robot for locomotor training in rats as a research tool in neuroscience and robot-assisted neurorehabilitation. The main design feature of the presented exoskeleton robot is the ability to produce synergistic movements between the limb joints similar to intact rats. The assist mechanism in this work with two degrees of freedom uses a combined four-and-five-bar mechanism to simulate the gait patterns of quadrupedal locomotion. We present the design and development of the assist mechanism, and preliminary experiments to verify its function by generating gait movements and evaluating their covariation planes. The results showed that the mechanism can produce three joint angles with inter-joint synergies similar to those of rodents, implying that the mechanism is valid for implementation in a rodent-size exoskeleton robot. The future outlook of this project is to implement a sensing modality for the animal’s voluntary will and perform demonstration experiments in vivo.