Angle of elbow joint control to exert maximum Torque in an upper limb operation-assisting robot

There are estimated to be approximately 3.5 million disabled people in Japan, and about half have a handicapped lower or upper limb. Recently, exoskeletons have been receiving attention as potential aids for such individuals. They can make up for lost body muscle, and support walking and standing-up motions. Robots can assist disabled people by using the power of an actuator to provide the force needed to support motion. When a robot is used for activities of daily living, the operator must wear the robot mechanism in order to transfer its weight from the operator to the robot or peripheral device (e.g., control device, battery, compressor) for operation. Thus, the robot's usage environment is limited. We believe that it is important that an assistance device that supports necessary motions of daily living does not affect other motions of daily living. In the case of the disabled and the elderly, often the end motor functions (such as limb functions) decline, but the function of the large muscles in the medial region remains. In this study, we focused on these groups of muscles. We developed a mechanism that translates remaining force to operational force in the hand, and designed an exoskeleton robot for the developed mechanism. In addition, we developed a control system that does not affect the operator's motion, but changes the mechanism via the original actuator when the operator is not using the robot. We determined the elbow angle that can achieve maximum torque by considering the length of the arm, the trunk, and the muscle force of the bending elbow joint.