Research On Power Flow Characteristics Of Bidirectional Composite Excitation And Control Strategy Of The Active Vibration Isolation System

Active vibration isolation system is one of the necessary technologies for meeting the vibration requirements of ultraprecision equipments such as the lithography machine.In recent years,lithography machine continues to high precision,high speed and high acceleration.Active vibration isolation system must have higher performance and attenuate bidirectional composite excitation of direct disturbance and foundation vibration at the same time.The research of active vibration isolation system is mainly divided into two parts:passive vibration isolation mechanism and active control.These two parts are relatively independent and there is no systematic analysis.Consequently,considering passive isolator parameters and active control parameters,research on power flow characteristics of bidirectional composite excitation and control strategy of the active vibration isolation system is carried out.The results have an important theoretical significance and engineering application.This dissertation focuses on the power flow characteristics of bidirectional composite excitation of active vibration isolation system,accurate model of key parameters of passive isolator and active control strategy.(1)In order to build the relationship between passive isolator and active control system,an analytical method for power flow characteristics of bidirectional composite excitation of the active vibration isolation system is proposed.First,the shortcomings of time averaged power flow in one period are pointed out.Then,the expression of time averaged power flow in one-fourth period is derived.In the end,the expressions of the power flow transmission from bidirectional composite excitation of direct disturbance and foundation vibration to the rigidity load instead of flexible load are obtained.System model has been established and can be used for providing a tool for comprehensive factor analysis of active vibration isolation system.(2)In order to obtain the more accurate stiffness and damping parameters for the power flow analysis of active vibration isolation system and optimal designing of passive isolator,the key parameter models of typical passive isolator are obtained.Considering the influence of vertical stiffness of rubber diaphragm and horizontal restoring force of air spring,the stiffness model of the air spring vibration isolator in series with the inverted pendulum is deduced.Considering the influence of pressure flow,shear flow and eccentric piston,the damping model of the viscous damper of clearance hydrocylinder is deduced.The correctness of these models is validated by experiments.(3)In order to fulfill the comprehensive challenge of active vibration isolation system,such as high performance,energy efficiency and multiple objects,a new control strategy for active vibration isolation system according to multi-objective optimization is proposed.This method selects the minimum value of the power flow transmission from the direct disturbance and the foundation disturbance to the load,the minimum value of the energy consumption of the active control system and the minimum value of the power flow transmission from the excitations as the optimization targets,respectively.Active control system can be optimized and different optimal control forces are derived.Parameter configuration is completed by establishing the relationship between the force of actuator and core parameters of control system.(4)Active isolator is designed based on the above analysis.The experimental studies of the different optimal control forces,the vibration power flow transmission characteristics and the vibration isolation transmissibility are carried out.The results indicate that the most effective performance is achieved when the optimal control force acts with the minimum value of the power flow transmission from the direct disturbance and the foundation disturbance to the load.Transmissibility of active isolator at frequencies upon 2 Hz is less than-10dB and transmissibility of active isolator at frequencies upon 5 Hz is less than-20dB.Meanwhile,transmissibility of active isolator at frequencies upon 20 Hz is less than-40dB.The innovative research results can provide forward design method for active isolator based on the comprehensive factor analysis.It lays an important theoretical foundation for catching up with foreign high-level active vibration isolation technology.