抄録
We have been aiming at developing a robotic aid for disabled persons who need assistance in moving from a bed or a chair. An MH actuator shows spring like behavior with adjustable stiffness realized by varying pressure in a bellows. The antagonistic MH actuator system using two MH actuators arranged in opposition to each other was developed to realize compliant joint motion of a robotic aid. The joint stiffness of the antagonistic MH actuator was varied in proportion to the sum of internal pressures of the two MH actuators. A robot arm having two degrees of freedom driven by antagonistic MH actuators was designed to test its behavior in contact with a human body. When the robot arm was inserted between a bed mat and a unilateral lower extremity of a human lying in a supine posture, the reaction force from the bed and the lower extremity were measured. From the experimental results, in the case of high joint compliance, the reaction forces from the body were lower than in the case of low joint compliance (nearly 0 rad N^<-1>m^<-1>). It was concluded that a robot arm that is to be used for handling a human body must have variable compliance joints, and that the antagonistic MH actuator was appropriate for use in robotic aids that handle the human body.
