Theoretical analysis and experimental evaluation of vibration isolation system with broadband characteristic for laser tracker

Abstract

High-energy synchrotron radiation source, as a large scientific device, is under construction in Beijing, China. Besides, this device is one of the fourth generation synchrotron radiation sources with the highest brightness in the whole world. After the device is completed, it will provide an important support platform for basic science and engineering science. As a kind of high-precision large-scale measurement equipment, laser tracker is mainly used in high-energy particle accelerator equipment installation, precision poses dynamic measurement and antenna feed dynamic motion precision engineering measurement field. Laser tracker is often used to calibrate, collimation and tunnel measurement of high energy source magnet equipment at the construction site of high energy synchrotron radiation source. However, the laser tracker is easily affected by the vibration of the surrounding environment, and the adverse vibration seriously affects its measurement accuracy and even causes equipment damage. In order to effectively control the influence of environmental vibration and ensure good static bearing capacity, a broadband vibration isolator for laser tracker is proposed. It is installed in the leg position of the triangular bracket of the laser tracker, which ensures the vibration isolation performance and good bearing capacity. For the above system, the equivalent single freedom nonlinear dynamic differential equation is established, and the steady-state response solution of the broadband isolator is obtained by using the complex variable-average method. The numerical finite element method is used to verify the correctness of the theoretical model and corresponding calculation results. On this basis, the stability of a nonlinear system is analyzed by harmonic balance method, and the influence of key designing parameter <i>K</i><sub>3</sub> on vibration isolation performance is considered. Combined with the complexity of the actual working environment of laser tracker, a variety of typical working conditions are set up for test, including long time static pressure test, vertical impact excitation and lateral displacement excitation tests, to evaluate the static stability and vibration control effect of broadband isolator. The experimental results show that the maximum static displacement of the laser tracker is about 2×10<sup>−5</sup>m under static pressure in a long time, and the maximum static load is within the allowable error range. When the occasional impacting excitation, the installation of broadband isolator can make the combination quickly restore stability in about 2.95 s, and exhibit better vibration isolation performance. Under different dynamic loads, by comparing the acceleration frequency response curves of the laser tracker with and without the isolator, in the frequency band below the fundamental frequency of the laser tracker, the attenuation rate of the combined system can be up to about 97% with and without the vibration isolator. In the frequency band above the fundamental frequency, the attenuation rate of the combined system with and without the vibration isolation system can reach up to about 88%, and the effective vibration isolation frequency band is extended. The broadband vibration isolator meets all technical requirements.