Atomic Interferometer Small Vibration Isolation Platform Study

Accurate measurement of the g value of gravitational acceleration has more and more significance for inertial navigation,geological survey,geophysics,basic physics research and other fields.At present,the wider demand for gravimetric measurement makes movable gravimeters an inevitable trend in the development of gravimeters,which puts forward higher requirements for the environmental adaptability of gravimeters,but absolute gravimetry has extremely high environmental requirements.In a noisy measurement environment,Due to the vibration interference of the mirror,clear gravity fringes cannot be obtained.In order to suppress the vibration of the mirror,a new type of small vibration isolation platform is designed in this paper.The main research work is summarized as follows:1.Analyze the main sources of vibration and noise,introduce the cold atom interference gravity measurement process,analyze the influence principle of Raman optical mirror vibration noise on gravity measurement results,and conclude that lowfrequency noise has the most serious impact on gravity measurement,and determine the design of vibration isolation platform The main vibration isolation target is 0.1-100 Hz vibration noise.2.Compare the shortcomings of passive and active vibration isolation alone,and establish a vibration isolation model combining active and passive vibration according to the requirements of the gravimeter for the vibration environment.Active vibration isolation suppresses vibration of 0.1-10 Hz,and passive vibration isolation suppresses vibration above 10 Hz.3.Taking the mirror as the vibration isolation target,a small vibration isolation platform combining active and passive is proposed and designed;the mechanical mechanism of the system is designed,and ANSYS is used to conduct modal analysis on it,and it is concluded that the natural frequency of the system in the vertical direction is about 5Hz;Design circuits such as VCCS to convert voltage signals into current signals;through frequency response experiments,it is proved that each hardware and circuit can work normally in the 0.1-100 Hz frequency band.4.Design the feedback controller of the vibration isolation system and simulate its effect.Carry out the free vibration and forced vibration experiments of the vibration isolation system,the natural frequency of the calibration system is about 6Hz,and the damping constant is 0.04;using the method of system frequency analysis,a lead-lag feedback controller is designed to improve the open-loop gain of the system while ensuring sufficient phase margin.5.Build a vibration isolation effect simulation model and an experimental test platform.Through Simulink simulation,it is concluded that the isolation degree of the system to vibration and noise in each frequency band is greater than 90%.The vibration isolation effect is verified by testing the residual vibration and noise power spectral density,and the gravity value variance is calculated.Reduce the contribution of ambient vibration to measurement sensitivity to 26.1mGal/shot.