An active microvibration isolation system for hi-tech manufacturing facilities

This paper presents an active microvibration isolation system using voice-c oil linear motors, and pneumatic and piezoelectric actuators. This system i s designed to reduce microvibration of the sir degrees-of-freedom associate d with the rigid body modes of the vibration isolation table by feeding bac k the pseudo absolute displacement and velocity of the table. To improve vi bration isolation performance. a feed-foward control link is added to the s way components in each dimension. This system can also control bending mode s of the table in the frequency range up to 200 Hz by employing a proposed Virtual Tuned-Mass Damper control strategy, which is a type of the pole ass ignment method. In this approach, the pole locations are chosen by a generi c algorithm. For ambient microvibration of the flour around 0.5 cm/s(2) and for small earthquakes of around 8 cm/s(2) a reduction by a factor of 100 w as achieved in the acceleration of the vibration isolation table. Moreover, the vibration of the isolation table was decreased over the entire frequen cy range. This system also showed good vibration control performance when a n impact excitation was applied directly to the table; vibration was damped our within about 0.1 sec. Additionally: the resonance amplitudes around th e bending modes of the table were reduced from 1/5 to 1/15 by the Virtual T uned-Mass Damper method.