Fluxgate Compass System Design And Application

In a variety of magnetic measurements and angle-measuring methods, fluxgate technology is most appropriate for electronic systems and computer support. It has adaptability under a variety of adverse circumstances and the complexity work conditions, and the capability after set with other electronic equipment and computer has been greatly improved to facilitate the realization of intelligent.Overseas, the fluxgate compass nearly eliminates the permanent magnet compass. The good vector response of fluxgate probe can make the fluxgate compass have high angle precision. The fluxgate probe is simple, reliable and easy-to-small.Taking into account the shortcomings of fluxgate compass and technical characteristics of fluxgate compass, I think we can develop a new compass system using of magnetic force with fluxgate technology. It can satisfy the following:1 The system should have all the advantages of the old-fashioned magnetic compass. For example, using only magnetic force may be able to work independently, simple structure, reliable operation, and so on.2 The fluxgate compass system should maintain compatibility with the original system, i.e. new compass system should be able to make full use of the original directing course on board, to reduce technical reconstruction costs. The specific achieve performance should be: The new system retains all the interfaces of original magnetic system, and keeps the same interface standard.3 The system has been added the microcomputer control part to increase the deviation eliminating accuracy. Computer control part finishes the main the following functions:1 ) Calculate the course angle. The microcomputer solves the course information of fluxgate probe after managed by fluxgate circuit part into digital code. In order to meet the precision requirements, digital bit of course angle is 16-bit code, i.e. the system dynamic range is about 0.0055°. 2) The autodyne compensation. This paper takes the reference of normal autodyne compensation calculating method-"Airy method" and gets the actual course angle by programming with single-chip microcomputer to achieve correction.3 ) Send and display the course information. The single-chipmicrocomputer sends angle the corrected information in digital.The basic principle of fluxgate technology is that the fluxgate probe modulates the environmental magnetic field into even harmonic induced electromotive force. The strength of this even harmonic induced electromotive force changes with the strength changes of magnetic field.To achieve accurate measurement, people general use dual-core fluxgate in practice, design to differential output probe to eliminate the induced electromotive force of fluxgate probe transformer effects. According to the fluxgate probe output signal characteristics, this project uses second harmonic select method to detect the environment field. The second harmonic select method to calculate the strength and direction of environment field by detecting the strength and polarity of second harmonic components in even harmonic induced electromotive force of signal output by fluxgate probe.The earth itself is a big ball with N, S poles and its DC magnetic field at surface is comparatively uniform. We can analyze the magnetic field strength at any point of the earth surface into two components of horizontal and vertical. As the magnetic signal has good vector response characteristics, we can analyze the geomagnetic field horizontal component on the two axes at water level by putting two fluxgate probes vertically at water level as the two axes of horizontal coordinates so as to get the two cosine and sine modulation signals related to earth's magnetic field North Pole direction. The amplitudes are separately direct proportional to the cosine and sine angles between measuring winding and earth's magnetic North Pole direction and their plus-minus are related to the phase of measuring winding. If calculate the sine or cosine angle, we can get the angle between the carrier and earth's magnetic North Pole so that get the carrier's navigation direction. So, putting two fluxgate probes vertically at water level can form a orientation sensor of compass system.The orientation sensor formed by fluxgate probe, fluxgate circuit display and sent parts of the course form the fluxgate compass system. The orientation sensor can be formed by two fluxgate probes vertically put at the water level. The main function of fluxgate circuit is correctly detect the useful signals from the fluxgate probe signals and so as to correctly express the course information output by orientation sensor. Correct detecting useful signals needs to design appropriate filter according to signal characteristics. The meaning of expressing course information is to change the physical signal of carrier's course information into digital signal fit for our management and use. In this system, we adopted javascript:void(0) tracking course-digital conversion program according to the system apply requirements and subject purpose. The system used AVR single chip microcomputer to receive the course information digital code and analyze and compensate the digital code to improve the system precision.The fluxgate compass system shows the course with magnetic vector as the benchmark. However, due to a number of reasons, environmental magnetic field interferes sensors magnetic signals result to some error of the output of fluxgate compass system orientation sensor, which is auto heterodyne. The auto heterodyne appears as ship magnetic field makes a deflection angle between compass north and magnetic north so as to form auto heterodyne. In the iron and steel ships, compass auto heterodyne can generally reach to as many as tens of degrees. So if do not compensate the auto heterodyne, the system will lose the practical application significance. The auto heterodyne compensation is achieved by operating compensation algorithm program in single chip microcomputer. Experiments show that, the system prototype test result basically achieved the indicators.