Design Of Quartz Cycloidal Micro-strain Actuation

With the continuous improvement of the instrument precision,the external vibration noise has an increasing impacts on the accuracy of the instrument,and the micro-vibration isolation technology has become a bottleneck to further improve it.Therefore,as one of the core technology of ultra-precision measurement / test equipment and ultra-precision machining equipment,it's quite crucial to study advanced ultra-low frequency micro-vibration isolation technology and develop related devices.There're some requirements for a good low vibration environment in several systems of the Large Scientific Engineering Project,including gravitational wave detection,dark matter detection,strong magnetic field and pulsar formation research.Among them,the main difficulty of gravitational wave detection is that the measured signal is particularly weak compared with the ambient vibration noise,so it is very necessary to isolate the environmental vibration,especially the influence of ground vibration.As the simplest horizontal vibration isolation system,pendulum is an indispensable part of the laser interferometric gravitational wave detector(LIGO).In this paper,a kind of cycloidal micro-strain suspension system based on the combination of giant magnetostrictive material and quartz material is studied since the gravitational wave detector has an urgent need for environmental vibration weakening or isolation.The basic ideas and main work in this paper are as follows:The working principle of each part and the whole wo rking mechanism of the cycloid micro-strain actuation system is firstly introduced.The actuation system mainly includes the fiber Bragg gratings used as the single pendulum main body,the giant magnetostrictive film and the magnetic field actuator GMA.How stress and temperature influences the pitch and the effective refractive index of fiber Bragg gratings separately,the principle of magnetic-machine conversion of the giant magnetostrictive materials and the principle of strain of the cycloid in magnetic field are all discussed in detail.The internal magnetic field of GMA is deduced,and the 1-D and 3D distributions of the magnetic field are simulated by MATLAB and COMSOL respectively.Secondly,how to amplify the cycloid strain and to ensure good mechanical properties as much as possible is studied.Four kinds of microstructures on the surface of fiber have been designed.The theoretical values of the sensitivity amplification coefficients of the four structures were calculated and simulated respectively.And the mechanical properties of the four structures were simulated by ANSYS.The amplification characteristics and mechanical properties of the different structures were analyzed synthetically and the most appropriate microstructure was chosen.Then,the microstructure of the fiber surface was processed by femtosecond laser.The experimental results show that micro-processing does not damage the gate region in the core of fiber,that is,the strain sensitivity of the fiber Bragg gratings is remained.The coupling of the giant magnetostrictive materials and fiber is realized by magnetron sputtering method and th e suitable coating conditions have been found,and the magnetostriction coefficient was measured by cantilever method.Finally,the cycloid micro-strain actuation system is built and a series of experiments have been conducted.The sensitivity of the fibers with microstructures on the surface to the magnetic field is improved by 27.58% according to the experimental results.The relationship between the strain and the magnetic field is measured and fitted,showing that the ratio of strain to magnetic field is(35)e(35)B(28)0.18nm/mT.The hysteresis characteristic of the cycloid in magnetic field is experimentally verified.Through the step test,the resolution of the cycloid strain in magnetic field can be obtained,the value is 9.729 m T,and the corresponding strain is 1.18 nm.The phase lag and frequency characteristics of the cycloid strain are studied by inputting different time-varying magnetic fields.Finally,experiments show that the stability of the system is 18.3nm.