The Suppression Arithmetic Of The Vibration For Absolute Gravimeter

Gravitational field is one of Geophysical fields which reflected the properties of the Earth, the information which contain are meaningful to the research of fundamental subjects such as solid Geophysics, space Geophysics, Geodynamics and seismology. Now there are two kinds of absolute gravimeters, one is based on laser interferometer and the other based on atomic interferometer, all of them are important to detect the information of Gravitational field.Laser absolute gravimeters are influenced by measuring systems, measuring environments, the interference of vibration of referenced stereo prisms, and so on. Among these aspects the interference of vibration of referenced stereo prism is most important. In order to reduce the influence, anti-shock isolation technology, which is based on hardware, is taken all over the world. With the development of the vibration of the high accuracy measuring technique and digital processing, it becomes possible to reduce influence of vibration of referenced stereo prisms. In this thesis we discuss the methods to restrain the influence of vibration of referenced stereo prisms according to digital processing.First, based upon the operating principles of the laser absolute gravimeters, the theoretical models of interference fringes are built. In this model, along with the falling of the falling body, some frequency-changed sinusoidal waves are generated. Meanwhile, based upon what we record a series of sinusoids are superposed to model the interfering signals, which, in fact, generates the nonlinear parts of real interfering signals.Second, in view of the kinematic equation of freely-falling body and the fact that the second differential of a straight line is zero, a new method we call marking out and selecting points method is proposed to extract the gravity value. Comparing the theoretical modeling and the real data, we find the deviations between the results and the original gravity values are-20～20μGal at different measuring points when the amplitudes of the interfering signals are less than10-7m. In this thesis we process16groups signals, we find that the residuals are less than10μGal and the precision of our arithmetic is two orders higher than the traditional method. When the amplitudes are changed, the difference of results and the original gravity value is no more than 20μGal. When frequencies changed and the amplitudes of the interfering signals are less than10-8m, the result also fit the original gravity values well. The only slight defects turn up when the frequencies between192Hz and260Hz.Third, based on the relative motion of the frame of the reference and the interfering signals of vibration, we develop a method to restrain the interfering signals. Comparing the theoretical signals and real data, we find that the difference between the results and original values are between-1μGal and1μGal at different measuring points when the amplitudes of the interfering signals are less than10-7m. According to16groups signals we process, we find that the residuals are less than1μGal, which means the precision of our arithmetic is three orders higher than the traditional method. When the amplitudes are changed, the difference of results and the original gravity value is no more than2μGal. When frequencies changed and the amplitudes of the interfering signals are less than10-8m, the precision of our method is one order higher than the traditional method.Fourth, based on the relative motion of the frame of the reference and the interfering signals of vibration, we develop a method to restrain the interfering signals. Comparing the theoretical signals and real data, we find that the difference between the results and original values are between10μGal and15μGal at different measuring points when the amplitudes of the interfering signals are less than10-6ms-1. The accuracy of the16groups signals we process is less than1μGal, which means the precision of the results taken by us is two orders higher than the traditional method. We also find that when the amplitudes are larger than10-7ms-1, the residuals become larger with the amplitudes increasing, however the accuracies are still higher than the traditional method. The deviations between our results and traditional method are less than2μGal when the amplitudes are less than10-7ms-1, which indicates our method is able to restrain the interfering signals. When frequencies changed and the amplitudes of the interfering signals are less than10-7ms-1, he precision of our method is one order higher than the traditional method.