The objective of this investigation is to develope a pneumatic on-off servo system, which can control a rotary actuator to any desired angular position.
The servo system consists of an electronic relay, a solenoid valve, stabilizing tank and a speed control valve which can be adjusted manually. Since the stability is of prime importance for this control system, it is analyzed analytically and experimentally by varing parameters of the servo system. The critical parameters include dead zone of the relay, flow rate through the stabilizing tank, and flow rate across an orifice of the actuat cylinder.
Since on-off servo system is essentially nonlinear system due to the relay action, the system stability is predicted using describing function method. According to the stability analysis orifices of the stabilizing tank and cylinder are effective for improving system damping. Some experiments were carried out to see the effect of such orifices on the control system performance such as stability and steady state and transient response.
It is shown that if a stabilizing tank or cylinder orifice is applied to the system, the on-off servo approach using pneumatic power can be used for the position control systems which permit a small tolerance between the input and load position.