Development Of Active Negative-stiffness Vibration Isolator For Low Frequency Optical Vibration Isolation Platform

The traditional passive vibration isolator is conditioned by the material properties and structure of the elastic component,structure stiffness is very difficult to further reduce.The natural frequency of vibration isolation is about 2Hz.At the same time,the working distance of vibration isolator and the inherent conflict between the rigidity of components elastic.Therefore,the urgent need for high-end vibration isolation technology research and development,meet the demand for precision micro vibration isolation technology is more and more high.This topic in view of the existing problems of vibration isolation technology,design a kind of active vibration isolator negative stiffness.Produce negative stiffness characteristics in active way,reduce the passive way of stiffness and natural frequency of vibration isolation.And structures the positive and negative stiffness parallel vibration isolation system,the experiment verified the effectiveness of active vibration isolator negative stiffness.This topic mainly includes the following parts:Firstly,to test and verify the feasibility of the positive and negative stiffness parallel vibration isolation method,the positive and negative stiffness parallel vibration isolation system dynamics model is established.Was calculated under different ways of feedback vibration transmissibility of vibration isolation system with MATLAB simulation of the vibration isolation system under different negative feedback stiffness coefficient of vibration transmissibility curves.Analyzed the different way of feedback,feedback coefficient after vibration isolation performance of the system.After comprehensive comparison,chose the load and the ground relative displacement feedback control mode.Secondly,analyses the active vibration isolation principle of negative stiffness,and discussed the factors affecting the external magnetic field uniformity of permanent magnet.In view of the existing ampere force actuator uneven air gap flux density,the output power instability problems,such as actuators air-gap magnetic field model is established.Analysis of different structure,different air gap thickness and other conditions on the actuator air-gap magnetic field intensity and the influence of magnetic field uniformity.Design a symmetrical excitation structure based on both ends of the active negative stiffness of actuators and optimize its structure parameters.After optimization of actuators in the air gap magnetic field intensity,the uniformity and stability of output force are increased significantly,the air-gap magnetic field non-linear is better than 0.37%.Thirdly,designed the data sample and current drive module.According to the requirements of the displacement measurement of the vibration isolation system designed in this paper,aiming at the characteristics of the free vibration of the existing optical vibration isolation platform,and a four-channel relative displacement sensor module with simple principle and easy integration is designed.The module measurement principle is simple,easy to calculate the displacement,using a four-channel signal subtraction two ways,effectively improve the accuracy of the displacement sensor.The resolution is better than 10 nm.Then,analyzed the influence factors of system control precision and vibration isolation performance.In view of large noise,large drift and nonlinearity in existing linear power amplifiers.The module make improvements in the traditional which based on the MOS tube voltage control current source circuit,a high precision linear bidirectional current drive module is designed.In the case of ensuring that the system bandwidth is applicable to the experimental platform of this subject,reduced system noise,improved the module linearity and dynamic bandwidth,effectively improved the accuracy of the drive.The optimized driver module resolution is better than that of 0.03 mA,linearity is better than 0.1‰,the bandwidth can be up to 5kHz.Finally,on the basis of the above research,set the active negative stiffness vibration isolator experiment platform.Design experiment plan,test based on the active negative stiffness of high-performance small floating micro vibration isolation platform features and performance of vibration isolation.Experiments show that the vibration isolation platform after active negative stiffness control,inherent frequency of 2.000 Hz to 1.375Hz;The resonance peak mu m drop from 1.0μm to 0.4μm;Vibration displacement amplitude by±3.0μm to±1.8μm;Vibration velocity amplitude from±28μm/s to ±19μm/s;The equivalent stiffness of system from 126.3kN/m drop of 59.7kN/m,.The performance of vibration isolation is improved a lot.