Vibration Suppression Control for a Pneumatic Isolation Table with Three Degrees-of-Freedom Using On-Off Valves

Abstract

Pneumatic isolation tables are generally used in the fields of manufacturing and measuring precision components, and several methods by which to achieve active control of pneumatic isolation tables have been proposed. In these studies, the internal pressure of the air springs is actively controlled by using servo valves in order to suppress micro-level vibration. On the other hand, so as to suppress millimeter-level vibration and obtain low cost equipment, several methods by which to achieve active control using on-off valves instead of servo valves have been proposed. In these investigations, a switching control method based on the Lyapunov function exhibits performances that are superior to the other methods. However, the switching control method suppresses vibrations in only the vertical direction. Therefore, improvement of the vibration suppression performance is required in not only the vertical direction but also the rolling and pitching directions. Thus, the purpose of this study is to obtain high vibration suppression performance for a pneumatic isolation table with three degrees-of-freedom using on-off valves. The switching control method is extended to multi-input system, and it is shown that the extended method is suitable for control of a pneumatic isolation table with three degrees-of-freedom. The effects of the extended method are verified by numerical simulations and experiments.