An Analysis of a Pneumatic Servo System and Its Application to a Computer-Controlled Robot

Pneumatic actuators are capable of providing high power output levels at a relatively low cost. In addition, they are clean, lightweight, and can be easily serviced. The difficulty of achieving a high-bandwidth, stable, pneumatic control system has limited its use in robotic position control applications. For open-loop control applications, such as many robot grippers, pneumatic actuators are often used. In this paper, direct-drive pneumatic servo-actuators are examined for their potential use in robotic applications. A complete mathematical model of the actuator is derived, and several control algorithms are tested numerically and experimentally. Our analysis shows that pneumatic systems are practical for use in servo-control applications. The main limitation is that of the system response time, which is determined by the valve flow characteristics and supply pressure. Large output forces can be obtained and accurately controlled with the servo-valve and differential pressure transducer used in the experiments.