Study On Disturbance Suppression And Compensation In Precision Vibration Isolation System

With the development of precision measuring instruments and processing equipment, the precision of measurement and processing is become higher and higher. Environmental vibration has become the critical factor that affecting the performance of these apparatus, and precision vibration isolation system (VIS) is the necessary guarantee for the generation of precision in precision manufacturing and metrology equipment. Suppress and compensate the disturbance from the base and direct disturbance is the key step to realize the performance of VIS, so disturbance suppression and compensation of different disturbance sources in VIS is become the research hotspot.Based on the national major scientific research project and facing the actual demand of the major engineering projects, this dissertation analyzes and researches into the suppression and compensation of disturbances come from the base and direct forces to further improve the performance of the precision VIS by using control strategy and compensation method and meet the increasingly stringent performance requirements and application requirements in different conditions. The main research contents and achievements are listed as follows.Considering the suppression of the base vibration, the linearized theoretical model of single degree of freedom precision vibration isolator is derived. The additional affection of the seal membrane can be regarded as dynamic model of the parallel stiffness and damping elements, the model is validated by experimental analysis and parameters identification, and laid the foundation for the theoretical analysis of passive vibration isolation. On this basis, a precision vibration isolator using an air spring and a pendulum connected in series is designed. The six degree of freedoms (six-DOFs) precision VIS is built using the designed vibration isolator. The dynamic model of the six-DOFs precision VIS is derived and the model parameters are identified. An active vibration controller is designed based on decentralized position control and strategy of mode-decoupling. The effectiveness of the six-DOFs precision VIS is validated by the performance test results: vertical location accuracy is±10um, and that transmissibility of base vibration occurring at frequencies upon2Hz is less than1/10. Meanwhile, transmissibility of vibration occurring at frequencies upon10Hz is less than1/100. In order to further improve the performance of suppressing the disturbance form the base in precision VIS, a feedforward compensation control strategy that uses the base vibration velocity as the feedforward signal and utilizes the filtered-x least-mean-square (fx-LMS) algorithm with improved gradient estimate is proposed. An experimental setup is built, and the effectiveness of the method is verified by these experimental results:the payload velocity attenuation rate is improved17%when the feedforward and feedback control is act on. A new approach that enhances the performance of isolating the vibration form the base is found.Aim at the center of gravity (COG) compensation of VIS due to the large disturbance, using the pneumatic as the actuator in COG compensation is proposed. The simulation results show that the frequency response width of the pneumatic spring using the sliding model control can eliminate negative effects of the compressibility of pressed air and the volume of the pneumatic spring, and can track5Hz sinusoidal signal, and meet the bandwidth requirements of COG compensation. The performance of precision VIS will be deteriorated by the mall amplitude direct disturbance, and a compensation strategy based on repetitive control is proposed. The stability of repetitive controller is studies. The results prove that the compensation strategy can suppress the base disturbance and direct disturbance simultaneously.Suppress and compensate the different disturbance resource is the critical technology to realize the performance of VIS. The research contents, methods and experimental conclusions are instructive and meaningful to improve the performance of precision VIS and can meet the requirement of different applications.