Design, modeling and optimal control of a novel compliant actuator

To avoid human–robot confrontation, it is necessary to create a safe, accurate and stable rehabilitation environment for stroke patients when using upper limb exoskeleton robots for rehabilitation training. Considering these requirements, this work presents a novel compliant actuator based on torsion spring devices and linear spring devices. The establishment of dynamics model and control algorithm are challenging tasks for the novel mechanical structure. Firstly, the mechanical structure of the compliant actuator is simplified, and the interaction forces between gear trains are considered to establish the dynamics model. Secondly, the optimal control scheme is designed based on the dynamics model, and the stability of the actuator system is proved theoretically. Thirdly, it has been demonstrated that the optimal control scheme ensures precise and stable trajectory tracking for the compliant actuator through comparative simulations. The experimental results verify that the proposed optimal control scheme can enable the compliant actuator to complete trajectory tracking under different working conditions, as well as the buffering and self-protection performance of the torsion spring devices. In addition, the tracking accuracy of the optimal control scheme is further verified by conducting trajectory tracking experiments on the compliant actuator-based upper limb exoskeleton robot.