Modal force and torque control with wire-tension control using series elastic actuator for body weight support system

In this paper, novel mechanical mechanism and control method using SEA are suggested for natural gait pattern and effective gait rehabilitation. Conventional body weight support system (BWS) focuses on static position lifting and has limitation for a subject to constrain natural gait pattern especially in the vertical and medial-lateral movement. To overcome such abnormal gait pattern during BWS rehabilitation, modal force and torque control using wire is applied in this paper. The control makes it possible for a subject to generate natural gait motion which is natural in the vertical and medial-lateral movement during gait rehabilitation. To implement modal force and torque control, reference transformation for control of the tension of two wire is suggested. To control the tension of each wire, SEA which is controlled by the model base is utilized. And experiments are performed to assess the control performance.

I. Introduction

Body Weight Support (BWS) is an emerging gait rehabilitation system, which can assist the weakness of lower extremity muscles, and help early recovery through the simulation and feedback of walking patterns. Several quantitative studies have investigated the effectiveness of the BWS [1]–[3]. For lighter weight of the system and mobility, this study targets the BWS mechanism on the ground.