Hybrid impedance control of a 3-DOF robotic arm used for rehabilitation treatment

A 3-DOF planar robotic arm is designed and used as a rehabilitation treatment tool for the survivor after suffering a stroke, aiming to assist them to recover upper-limb function. In order to strengthen the patient´s arm, some forces are desired to be followed while the position trajectories should be tracked simultaneously, therefore hybrid impedance control (HIC) is proposed. Due to the redundancy for the planar motion, besides the main task, the secondary task is combined into the control scheme and the constraints of joint limits avoidance(JLA) are considered. Some typical trajectories are simulated for rehabilitation motion and a couple of simulations are made to study both the impedance control and hybrid impedance control strategies. The simulation results are compared and discussed and the tracking effectiveness of the proposed method is confirmed.