Development of a manipulator with straight-fiber-type artificial muscle and differential gear mechanism

In recent years, the demand for a robot that plays an active part in medical treatment and nursing has been increasing. The robot that interacts with humans should not only have a high output but should also be safe and flexible. We adopted a pneumatic artificial muscle as an actuator of the robot manipulator to satisfy these requirements. Pneumatic artificial muscles are lightweight and have a high power output. However, a McKibben-type artificial muscle commonly used for this purpose is problematic; therefore, we developed a straight-fiber-type artificial muscle that surpasses the McKibben-type in regard to its output. We also developed a two degrees of freedom artificial muscle manipulator with a differential gear mechanism, which can double the stiffness output of the conventional manipulator. Moreover, we propose a control system for this manipulator about joint angle and stiffness. We controlled the joint angle using the PI control method, and controlled joint stiffness by the torque feedback control method. Finally, we performed experiments to verify control system.