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A pneumatic actuator outputs large power in proportion to weight and can be installed in an inexpensive, light and compact configuration. From the standpoint of controllability, however, it is weak due to nonlinearity by compression and delayed transfer of air, it has a problem of poor accuracy in position control. To solve such problem, we propose a hydraulic/pneumatic hybrid actuator that has a pneumatic cylinder and hydraulic cylinder in parallel and uses the hydraulic cylinder as damper. We demonstrate that it can be used in practice and structurally applying it to a manipulator with 2-DOF. It also demonstrates that high-speed and stable control can be achieved by applying optimal control method.

Robots utilized in the fields of welfare or agriculture should be light in weight and flexible in structure. A pneumatic actuator is considered as a candidate of actuators realizing such robots, because it is more powerful compared with a motor of the same weight. It is also flexible, clean and unexplosive. In this paper, a new structure of the pneumatic actuator with two-degree-of-freedom is proposed. By combining these proposed pneumatic actuators, multi-degree-of-freedom pneumatic manipulator can be easily constructed, and a fourteen-degree-of-freedom pneumatic dual manipulators was constructed. The performance of the proposed dual manipulators is confirmed through experiments for ball-handling with impedance control. The results show that the flexibility of the pneumatic actuator is appropriate to accomplish the coordinate motion of the right and left arms of the robot.