Study On Active Vibration Isolative Techniques For Precise Instruments

This dissertation reports a theoretical and experimental study on the active vibration control of a precision vibration-isolation platform. It is supported by a project funded by the Natural Science Foundation of Zhejiang Province, China, titled "Research on Supporting Technology of Active Vibration Isolation for Precision Equipment Systems" (Grant No. 599085). Based on the state-of-the-art research both in China and abroad, the dissertation adopts the approach of applying theoretical analysis, computer simulation and actual experiments; With such an appoach, an active vibration-isolation strategy for precision instruments was proposed, a giant magnetostrictive actuator for the vibration-isolation system was developed, the transmission characteristics of the power flow in the system was analyzed, and finally, the active vibration-isolation comtrol system for precision instruments was established by adopting an immune control method, A test rig of the vibration-isolation system was developed, which was used to carry out some relevant experimental studies.In Chapter One, the background and significance of the research are introduced, and the state-of-the-art research of active vibration isolation both in China and abroad is expounded, including the vibration-isolation strategy, actuators and sensors, transmission characteristics of power flow, control strategy, etc. The aspects of research covered by this dissertation are also elaborated.Chapter Two takes the electronic microscopes (a kind of optical instruments) as the study cases. The dynamic model of the multi-DOF vibration-isolation system in the form of platform vibration isolation is created. The vibration displacement transmissibility of typical one-stage active vibration isolation system and passive vibration isolation system are analyzed. Then the vibration acceleration transmissibility of the vibration isolation system in one direction is discussed for the commonly used two-stage active vibration isolation model, by assigning different parameters to the feedback control variables.Chapter Three first analyzes the characteristics of giant magnetostrictive material. After that, a giant magnetostritive actuator used in the active vibration control for precision instruments is developed. The static state and dynamic output characteristics of force and displacement of the giant magnetostrictive actuator are measured and analyzed, and the nonlinear hysteresis model of the giant magnetostrictive actuator is also established.In Chapter Four, a vibration-isolation model of active and passive vibration-isolation system for the precision instruments are established. For the active vibration-isolation system that adopts magnetostrictive actuators, the power flow transmission function is derived using a four-port parameter method. Numerical simulation and analysis is carried out based on the transmission function, and the influences of different controller feedback parameters on power flow transmission characteristics of the system are discussed in details.Chapter Five combines the two-stage vibration-isolation model and the idea of artificial immune system to develop an immune feedback controller for the active vibration isolation of precision instruments. Extensive simulation study is done in the MATLAB environment, and the anti-disturbing capabilities and time-domain performances of the developed controller are studied.In Chapter Six, a test rig of vibration-isolation experimental system for precision instruments, based on an industrial personal computer, is developed, including both its hardware and software system. By utilizing this test rig, some experiments on passive isolation, and those on the combined active and passive isolation are carried out.Chapter Seven concludes the dissertation by summarizing the main findings of the research as well as the further research prospects.