Identification and control of precision XY stages with active vibration suppression system

Abstract

In this paper, a design method of the reaction force control system for ultra-precision stage which equips vibration control system, is proposed. Taking the application to semiconductor manufacturing into consideration, the designed system deals with both the reaction force due to the stage movement and the vibration from the external environment. The experimental setup for a 6-degree of freedom (DOF) motion control system is firstly designed. The system is controlled by two counter weights that are placed eccentric from the center of gravity, i.e. two weights are not co-axial. Next, the system identification experiments based on a subspace method are performed to build the multi-input multi-output state-space model. The reaction force and vibration control systems are designed using the identified model based on bilateral control strategies. The main advantages of the proposed identification and control approach are that the experimental time for accurate identification is quite short and the control system can be systematically designed. Finally, the effectiveness of the proposed control system is verified through the vibration control experiments.

A magnetorheological fluid embedded pneumatic vibration isolator allowing independently adjustable stiffness and damping

“…Note that equations (8) and (10) are used to describe the nonlinear spring force and nonlinear damping force with some adjustable design parameters. To assess the influence of design parameters upon isolation performance of the MrEPI, the non-dimensional dynamics under harmonic excitations is established in terms of some deliberately defined non-dimensional variables.…”

“…are the spring and damping forces given by equations (8) and 10, respectively. The dimensions of the variables above can be reduced to three basic dimensions (mass (M), length (L), time (T )).…”

“…Various active or semi-active devices have been used in the design of vibration isolators, for example, pneumatic or hydraulic cylinders [7], voice coil motors [8], electromagnetic actuators [9], magnetorheological or electrorheological dampers [10], piezoelectric actuators [11] and intelligent materials such as THUNDER [12] and shape memory alloys [13]. Pneumatic isolators have the advantages of providing high payload, reliable and inexpensive maintenance and low natural frequency, and thus find wide applications 1 Author to whom any correspondence should be addressed.…”