A HYBRID STRUCTURE OF DUAL STATORS AND A PNEUMATIC SPRING FOR RESONANCE CONTROL IN AN AIR MOUNT

摘要

An active device using electro-magnetic forces was constructed and experimented for the purpose of minimizing resonance in air mounts of clean rooms. The air mounts are vulnerable to low frequency resonance due to heavy weight and low stiffness. We developed and tested a hybrid structure of the active device which is composed of pneumatic and electro-magnetic parts. The pneumatic parts in the device support heavy weights under air mounts and the electro-magnetic parts reduce the resonance. The electro-magnetic parts are composed of dual stators and an armature which surround the pneumatic parts. The resonance can decrease when the electro-magnetic forces are generated in gaps between the stators and the armature. Four active devices were installed under a 3-ton surface plate for vibration test apparatus. The vibration was detected by eddy-current sensors. Discrete P Control logic was based on displacement and embedded in a C6713 DSP. The results from impact tests show that the peak magnitude in the resonance frequency can be reduced to -10dB.