Modeling and development of an exoskeleton robot for rehabilitation of wrist movements

As a stage toward a complete upper-arm motion assisted exoskeleton robot (i.e., 7DOF) this paper focused on the development of a 2DOF exoskeleton robot to rehabilitate and to ease wrist joint movements. To perform essential daily activities the movement of shoulder, elbow, and wrist play a vital role and proper functioning of the upper-limb is essential. We therefore have been developing an exoskeleton robot (ExoRob) to rehabilitate and to ease upper limb motion. The proposed 2DOF ExoRob is designed to be worn on the lateral side of the forearm in order to provide naturalistic movements (i.e., flexion/extension and radial/ulnar deviation) of the wrist joint. This paper also focuses on the modeling and control of the proposed ExoRob. A kinematic model of ExoRob has been developed based on modified Denavit-Hartenberg notations. In dynamic simulations of the proposed ExoRob, a nonlinear sliding mode control technique is employed, where trajectory tracking that corresponds to typical rehab (passive) exercises has been carried out to evaluate the performances of the developed model and controller. Moreover experiments were carried out with PID controller to further evaluate the developed model regard to trajectory tracking. Simulated and experimental results show that the controller is able to maneuver the ExoRob efficiently to track the desired trajectories, which in this case consisted in passive arm movements. Such movements are typically used in rehabilitation and could be performed very efficiently with the developed ExoRob and the controller.