Control of Hand Rehabilitation Robot by Using Tendon-Linkage Mechanism for Individual Joint Movement

Abstract

Paralysis of the hands are caused by sequelae of neurological diseases such as stroke, spinal cord injury or other causes. Because hand performs various grasping movements for Activities of Daily Living(ADL), such paralysis of hands causes a discomfort to daily life and disabling independent activities of the patient. In this study, we propose the grasp control algorithm of a hand rehabilitation robot with individual movements of joints.

The hand rehabilitation robot ReH2 is composed of thumb and index finger parts. It has two actuators per finger so a total of four actuators and complex structure of tendon and linkage mechanism. In order to derive the actuator’s power requirement of the robot, we simulate the robot and finger structure first. The finger was modeled using the passive moment generated by the musculoskeletal system of the human finger. The tendon inverse kinematics was used to simulate the relationship between the changes in the tendon length of the robot with respect to changes in the finger joints. In order to simplify the robot, we aimed that the hand rehabilitation robot interacts with various objects by using the impedance control without additional force sensor. At this time, synergy theory was used to establish the proper grasping sequence of segmented robots.

This controller applied to a ReH2. We measured the force of the robot grasp operation using the load cell. And the motion capture program was used to verify movement within the Range of Motion of the real finger during robot operation. Finally, we confirmed it is possible to grasp objects of various sizes freely, and the operation of radial palmar grasp and radial digital grasp is verified.