Active control of a pneumatic isolation table using model following control and a pressure differentiator

摘要

Pneumatic vibration isolation systems are widely used in semiconductor production processes. Most of them are controlled with nozzle-flapper type pneumatic servo valves. However, these servo valves require large exhaust air flow rates in order to control pressure precisely. In this paper, the model following control method was applied using a pressure differentiator and a spool type servo valve to actively control a pneumatic isolation table. Experiments were carried out on an air-spring system supporting a heavy granite bed, the displacement of which was modeled with a single degree of freedom. The experimental results gained in this research demonstrate the possibility of realizing a more efficient vibration isolation system than the conventional system using nozzle-flapper type servo valves. More specifically, this investigation showed about a 90% decrease in the steady-state exhaust air flow rate.