Development of a Quick Performance Assessment Method for Active Vibration Isolation Systems

Abstract

The performance of high precision applications highly depend on the ability to reject mechanical disturbances. Extreme accuracies can only be achieved if the object can be isolated from its environment. Vibration isolation is the process of isolating an object from the source of vibration. In active vibration isolation, an entire instrument of sensors, controllers and actuators are used to achieve a better performance. Future systems like Extreme Ultra-Violet (EUV) Lithography are expected to rely more and more on active isolation systems, which puts new requirements on analysis and simulation methods. In high precision applications of complex systems high degree of vibration isolation is needed. In these cases it is required to have a more detailed model of the system, which is usually done with state of the art Finite Element Modelling (FEM) techniques. However, FEM is not appropriate when for example the details of the geometry, location of the isolators or components of the system are not yet known. This typical challenge is to be faced in the concept design phase of the complex systems like EUV-lithography. In this thesis, we discuss how to develop a methodology with low fidelity models, where we can better understand the system and perform quick system assessment techniques to easily compare various design options. As particular case we derive the 3-Dimensional lumped elements model of the Active Vibration Isolation System (AVIS), defining the disturbance inputs in terms of their spectra and quantitatively measuring the performance of the system by using Cumulative Power Spectrum (CPS) and H2 norm. Simulation experiments are done to evaluate the performance for different configurations of the system.