Research On Active Vibration Isolation System With Air Bearing Structure

With the development of high-technologies such as precision manufacturing andprocessing industry, high-precision optical equipment and aerospace technology, peoplebegin to propose more stringent requirements on the stability of structure and theaccuracy of system. Vibration interference is the key factor that directly affects thestructural stability and accuracy. The impact of these tiny vibrations has become abottleneck of many cutting-edge technologies. To solve this problem, this studyproposes an active vibration damper system based on air bearing structure. This systemcan be widely applied in the field of precision machining lathes, high-precisionmeasurement systems and microelectronics processing equipment, which are sensitiveto vibrations (especially low-frequency vibration).This active vibration damper system is a mixed system of active and passivedamping system. Wherein the passive air flotation unit is mainly composed of the airspring structure and static pressure flotation configuration. The system can realize thenon-contact support by the function of the passive air flotation unit. This unit structureitself is a passive vibration isolation structure with small stiffness, which can efficientlysuppress the interference from the environment. But such passive system has manydefects: the damping effect of the system is significantly constrained by the structuralcharacters, and its inhibitory effect for the vibration from the load itself is weak. Tosolve these problems, this active damper system utilizes the active damping unit basedon voice coil motors assisting the passive air flotation unit, in order to reduce the loadspeed and the natural frequency of the system more significantly.Specifically, this study first introduced the composition and function of the activevibration damper system in detail. By the means of theoretical derivation, this studyanalyzed the structure characteristics in both vertical and horizontal directions and thenintegrated the characteristics into a theoretical model with multiple degrees of freedom.Secondly, taking the structural characteristics and functional requirements intoconsideration, this study designed the control algorithms for passive positioning unitand active damping unit respectively. To be more detailed, the passive localizationprocess could be divided into two parts, the preliminary positioning by flotationstructure and the pinpoint positioning by voice-coil motor system. While the activedamping unit used the integrated method of active damping control and negativestiffness. Thirdly, based on the application of the active damper system in lithographysystems, this paper analyzed how to apply the active vibration dampers in a joint wayand designed the decoupling control algorithm in six degrees of freedom in order toachieve the multi-degree of freedom vibration control purpose. Finally, this study analyzed and verified the effects and characters of the activevibration damper system by experiments. These experiments can be divided into twoparts: the comparative Experiment between active and passive control systems and thedamping performance test of the system in multiple degrees of freedom. Theexperimental results showed that: The damping performance of the system has beenimproved after the function of active control method, with the amplitude of vibrationand the natural frequency have been reduced by about42%and16%respectively.Meantime, the whole system has shown an effective and efficient vibration dampingperformance in multiple degrees of freedoms，suppressing more the80%of vibrationdisturbance with frequency above10Hz.