Development Of A Three-component Instrument Based On Fluxgate And The Research Of Calibration Algorithm

During the work of the geological exploration well logging, transmitting theattitude information such as well deviation and orientation of the current well to theground system accurately and real-time will play a crucial role in geological prospectingand mineral exploration. Magnetic exploration is an effective method of achieving welllogging and geophysical prospecting. The three-component instrument based onfluxgate is considered to be the expansion and extension of ground inertial navigationsystem based on magnetic measurements, and as a powerful tool of magneticexploration, it is not only used for attitude measurement of tilt and azimuth angle duringthe work of logging, but also used to detect borehole magnetic anomaly, therefore it iswidely used in the fields of detecting the origin of magnetic field, environmentalmagnetic detection, well exploration, directional measurement and so on.In this paper, a tri-axis accelerometer sensor(ADIS16210) and a three-componentfluxgate sensor are composed of an inertial system, based on the relative stability of thegravity and magnetic field and combined with spatial coordinates matrix transformationand algebraic equations, the paper deduced the calculation of tilt angle and azimuthangle and brought the implementation of the whole system, including system blockdiagrams, hardware design and software development, then the three-componentmagnetic survey instrument is ultimately successful developed. To the sensors andsystem installation errors, this paper detailed analysis of the sources of the errors,analysis the existing methods of sensor error calibration, purposes a method ofestablishing a mathematical model of combined errors and uses the least squaresmethod to achieve the purposes of optimizing calibration and improving accuracy. Thispaper presents the results of the least square method after calibration, and verifies thefeasibility and effectiveness of this method by comparing with the common calibrationmethods. In addition, for the anomaly detection of three-component magnetic, thispaper preliminary studies the methods of magnetic anomaly detection and themathematical formulas including horizontal component of magnetic anomaly detection,and then gives the verified through experiment. Meanwhile, in order to process the dataof the equipment and calculating parameters easily, this paper also designs some MatlabGUI interactive interfaces for auxiliary analysis. This design uses the MCU of Freescale MC9S12XEP100as the coremicroprocessor and the data are read from the tri-axis accelerometer andthree-component fluxgate through the communication interface of SPI and SCI, thenprocesses the data, and uses the C language programming to achieve system functions,and calculates and outputs the current key information of measurement device such astilt angle, azimuth and horizontal component of the total magnetic. After hardwaretesting, software testing and system installation, a three-component instrument based onfluxgate is developed. Using the calibration parameters calculated by the least squaresto calibrate the error of the device, which is verified by standard test platform. Theresult shows that this scheme and the calibration algorithm can obtain a stable and highprecision azimuth angle and tilt angle of drilling tools, with the deviation of the formerless than±2°and the deviation of the latter less than±0.2°. In addition, the system cancalculate the magnetic three-component results of current position to determine whethermagnetic anomaly exists.This paper studies and designs a three-component instrument based on fluxgatewith high accuracy, simple structure, small size and low power consumption, which hasimportant significance in theory research and practical engineering application.