Control of robot arm using pneumatic artificial muscle with spherical joint

This paper describes the robot arm with a high affinity to a human arm, an increased demand for which is anticipated in welfare-related and elderly nursing fields. We used the spherical bearing and the pneumatic artificial muscle actuator for the arm that we developed. Moreover, to achieve the affinity, safety, and the controllability by a good balance, it examined the control law in consideration of the characteristic of the mechanism and the actuator. The pneumatic artificial muscle is lightweight and high power. In addition, it is possible for it to emit exhaust into the atmosphere because the transmission medium of its energy is air, and it needs neither a tank nor maintenance like hydraulic equipment. In addition, safety to a person and the environment is high because the base of the actuator is a soft polymeric material even if the damage to the artificial muscle is caused. On the other hand, because the device is composed of a thin film cylinder, and easily receives the influence of the outside power for the conversion of the volume change in rubber into physical contraction axially, and its passive character is strong, precise positional control is difficult. Therefore, we apply the H_∞ control that is the method of frequency shaped, and construct a stubborn system to the unstructured uncertainty.