Experimental Test on Rehabilitation Robot Manipulator Upper Limb with Impedance Control for Flexion-Extension Path Following Motion

Abstract

This research presents position and torque control with impedance scheme for a rehabilitation robot for post-stroke 
patients. A three-degree of freedom robot manipulator is developed in this research. The developed rehabilitation robot for patients after stroke period focuses on upper limb body to perform flexion-extension movements on a shoulder. Impedance scheme is derived from two inputs, external force and impedance values. External force is obtained by load cells placed at the end of the robot’s end-effector. The external forces are measured in X and Y axis. The result is implemented for robot control system by applying PI controllers. Each parameter is utilized to control rotation movements and torque error in each X-axis and Y-axis motor. According to the test result, one-degree error is obtained. Robot movement is generated by planning the path movement before the rehabilitation. From the design and experiment, when a subject is unable to follow the path rehabilitation planning, it generates some force which is detected by force censor at the endeffector. This force gives the feedback signal to the motor. It allows motor to move in suitable directions and forces according to the signal at the end-effector. If external force does not exist, robot responses to assist the subject/patients by correcting the path planning. In the control system performance test, system error value of ± 1° was successfully obtained.