Electro-pneumatic time-delay control of high amplitude vibrations at asymptotic stability of pneumatic table due to mechanical valve operations

摘要

A typical pneumatic table for vibration isolation is equipped with mechanical valves to level the table as well as to compensate large pressure change in the chamber. Once the mechanical valves are adjusted at the initial stage of installations of the table with equipments on it, it is expected that the table be stable. Sometimes, however, there may occur high amplitude vibrations at the asymptotic stability of the pneumatic system due to unexpected large disturbances in the equipments or other external excitations. Recently active control of pneumatic tables using electro-pneumatic valves has been realized very successfully for suppression of vibrations even in the very low frequency range due to excitations from either ground or equipments. Although the main purpose of this active technique is to control vibrations at low amplitudes smaller than tens of μm, it can also be applied to control vibrations at high amplitudes larger than a few mm because the electro-pneumatic valves can easily provide large dynamic pressure into the air chamber. In this paper, high amplitude vibrations at the asymptotic stability of a pneumatic table with mechanical valves will be illustrated. Then, suppressions of those by 3 degree of freedom active time delay control using the electro-pneumatic valves will be presented. Successful results of the method will be discussed together with feasible applications in practice.