Development of a standing-up motion assist robot considering physiotherapist skills that bring out abilities from the patient

Abstract

This paper proposes a method for assisting standing-up by a robot that utilizes patients' own power to their extent while allowing them to stand up easily. Analyzing the skills of physiotherapists, we extracted two skills that assist patients in standing up by themselves, (1) promoting a forward-bending posture by making their upper body close to a single rigid body, through stretching their back and anteverting their pelvis, and (2) providing minimal balance so the patient does not fall down. In order to implement these skills, we propose (1) a body holder to hold the patient's upper body which reinforces a natural forward-bending posture, and (2) a horizontal position and vertical force assist control system which guides position control in the horizontal direction and assists with exerting force through force control in the vertical direction. We also propose a velocity-switching method as a simplified implementation of the physiotherapist skill. We built a prototype assist robot, which is compact and movable, aiming at the commercialization of standing-up motion assist robots. We implemented the skills of physiotherapists to this prototype robot and confirmed the validity of these skills. We detail the relationship among robot's speed, forces acting on the robot's user and muscular activation. From the results of this analysis we derive indications on the speed appropriate for assisting the sit-to-stand movement.