Force control of an upper limb exoskeleton for virtual reality using impedance control

This paper presents the development of an upper limb exoskeleton for displaying force generated by virtual environment. The device allows the user to sense the profile of virtual object through joints at wrist, elbow and shoulder. The Impedance controller with model feed forward is used to compensate the weight of the device and adjust the closed loop system to perform as the desired dynamic. Torque exerted by human is estimated by the observer, which is proportional to the stiffness observer gain and the estimated position error. Simulation result shows the estimated force and corresponding motion in both free motion and contact the virtual wall.