Modeling and control of a 7DOF exoskeleton robot for arm movements

Abstract

To assist a large number of physically disabled people who no longer are in full possession of their body motion, we have been developing an exoskeleton robot (ExoRob) to rehabilitate and to ease upper limb motion since movement of shoulder, elbow, and wrist play a vital role in the performance of essential daily activities. The proposed ExoRob will be comprised of seven degrees of freedom to enable naturalistic movements of the human upper-limb. This paper focuses on the modeling and control of the proposed ExoRob. A kinematical model of ExoRob has been developed based on modified Denavit-Hartenberg notations. To achieve the dynamic simulation of the developed model, a nonlinear computed torque control technique is employed. In the simulation, the trajectory tracking performance of the controller is evaluated with the developed dynamic model. Simulation results show that the controller is able to drive the ExoRob efficiently to track the desired trajectories, which in this case consisted in passive arm movements. Such movements are used in therapy and could be performed efficiently with the developed model and the controller. This paper also focused on the development of a 7DOF upper-limb prototype (lower scaled) master exoskeleton arm (mExoArm) which corresponds to the proposed ExoRob. The developed mExoArm will be used to maneuver the proposed ExoRob (in manual control mode) especially to provide `passive mode of rehabilitation'.