Research On Key Technology Of Automatic Geomagnetic Deviation And Inclination Absolute Measuring Instrument

Geomagnetism is an observation science.The research and application of geomagnetism depend on the observation data of geomagnetic field with sufficient accuracy.Geomagnetic observations are divided into absolute observations and relative records.Geomagnetic absolute observation is to measure the absolute value of geomagnetic field elements,and geomagnetic relative recording is to continuously record the relative changes of geomagnetic field elements.At present,the absolute observation of geomagnetism local and abroad basically adopts the "FDI" combined measurement method,that is,a proton magnetometer is used to measure the absolute value of the total geomagnetic intensity F,and a fluxgate theodolite is used to measure the magnetic declination angle and the magnetic inclination I.At present,the fluxgate theodolite for measuring the declination and inclination of the geomagnetic field is still in the manual observation stage(in China's geomagnetic stations,it is manually observed twice a week),which not only makes it difficult to effectively improve the time resolution of the absolute observation of the geomagnetic field,but also directly restricts the development of unattended automated stations and affects the optimal layout of geomagnetic observation networks.Therefore,the automatic geomagnetic absolute observation instrument has become a hot spot in the international geomagnetic observation technology research.At present,only Germany and Belgium have researched and obtained the principle prototype of an automatic geomagnetic declination and inclination measuring instrument.The Institute of Geophysics of China Earthquake Administration in our country is also carrying out research on automatic geomagnetic absolute observation technology and instrument development.This article focuses on the key technologies of the automatic geomagnetic declination and inclination measuring instrument,and carries out the following research:(1)Mechanical structure design of automatic geomagnetic declination absolute angle measuring instrumentDetermine the mechanical structure of the automatic geomagnetic declination absolute angle measuring instrument,and design the structure of each discrete module;based on the prototype,perform a force check on the horizontal axis system and the vertical axis system to calculate the bearing stress;determine the non-magnetic selection mechanism material category;use the finite element method to analyze the rotation accuracy of the shaft system and the modal analysis of the whole machine.(2)Electrical system design of automatic geomagnetic declination absolute angle measuring instrumentDetermine and select the type of drive device through the analysis of the inertial load,gravity load and friction load of the rotating shaft system;determine and select the position feedback device through multi-parameter error analysis;determine the compensation of the vertical axis through the analysis of the effect of the vertical axis inclination on the measurement error and type selection.(3)Error simulation and error compensation of automatic geomagnetic declination absolute angle measuring instrumentEstablish the output model of the fluxgate sensor,and analyze the influence of the vertical axis sway error,horizontal axis sway error and magnetic axis non-orthogonal error on the measurement results;based on the sensor model and "four-position measurement method" to derive the magnetic declination angle and magnetic tilt angle.The error compensation algorithm uses the measured data of geomagnetic stations to verify the compensation algorithm and determine the application range and compensation effect of the compensation algorithm.(4)Design of geographical north markersStudy the scheme design,device selection and optical path design of geographical north markers.By analyzing the optical path characteristics of the forward alignment and reverse alignment,the problem of the laser beams in the alignment is not in the same horizontal plane is solved.The main innovations achieved in this paper include:(1)Based on the multi-body system theory,the sensor output model of the automatic geomagnetic declination absolute angle measuring instrument was established,and the computer simulation was used to intuitively show the influence of various errors on the measurement error during the assembly and operation of the instrument.(2)Based on the sensor output model and the "four-position measurement method",a multi-parameter error compensation algorithm for magnetic declination and magnetic inclination is proposed.This algorithm can eliminate the non-orthogonal error of the horizontal axis and the magnetic axis and the sensor zero offset error.For the motor stop error and vertical axis tilt error existing in the measurement process,the compensation algorithm can be corrected.(3)The structure and optical path of the geographical north marker are designed.The total reflection prism and beam splitter are used to solve the problem that the laser beams are not on the same horizontal plane during the alignment of the forward alignment and reverse alignment.