Geomagnetic principles and electronic compass

Electronic compass has its own unique advantages: the electronic compass itself is small in size, light in weight, the acquisition and solution of azimuth information is real-time, and the output digital signal can make it more direct and convenient in the subsequent use. At present, the development of digital compass sensor technology has been relatively mature, so that it has certain advantages in measurement accuracy and manufacturing cost. Because digital compass is widely used in practice, a large number of high-precision, low-cost electronic compass products suitable for large-scale industrialization need to be put into production.

In today's society, the design and research of navigation and orientation instruments have important value and significance. With the expansion of human exploration in the space field, the stability maintenance, tracking guidance and other functions of artificial satellites, space shuttles, missile weapon systems and various platforms all need the support of navigation orientation technology and corresponding attitude adjustment devices. To sum up, obtaining orientation information and realizing the corresponding attitude control play a fundamental role in various scientific research and engineering realization.

According to the characteristic that the geomagnetic field changes little in a certain time range, it can be considered that the geomagnetic information at the same place is fixed in a short time, and the azimuth information such as heading Angle and attitude Angle can be calculated by the electronic compass according to the geomagnetic intensity information measured.

1.The principle characteristics of the geomagnetic field

As the basic physical quantity of the earth, the geomagnetic field has a direct effect on the physical characteristics of electric and magnetic substances in the earth environment. The characteristics of the Earth magnetic vector field provide a basic coordinate system for azimuth information, and the use of geomagnetic information navigation is stable and reliable, without receiving external information, with good concealment. The geomagnetic field is generated from the structure of the earth itself. There are many magnetic elements and substances in the earth's interior, which produce free flowing electrons under the influence of the extreme environment inside the Earth. These free electrons lead to the improvement of the conductivity between the earth's inner core and outer core, resulting in the flow and movement of free electrons between different strata. This makes the earth as a whole have a stable magnetic field on a macro level, which is equivalent to a magnetic dipole with a constant magnetic field existing in the center of the Earth, resulting in the production of north and south magnetic poles. Figure 1 shows the schematic diagram of the distribution of the Earth's magnetic field.

The unit of magnetic induction intensity is Tesla (T), which is Gaussian (Gs) in Gaussian units, and the corresponding relationship between the two is 1T=10-4Gs, the unit system of magnetic field intensity is A/m, and the unit system of magnetic field intensity is Oster (Oe) in Gaussian units, and the corresponding relationship between the two is 1A/m=4π*10-3Oe

The Earth's magnetic field can be classified into basic geomagnetic field, variable geomagnetic field and abnormal geomagnetic field according to the degree of stability. The basic magnetic field covers most of the magnetic field, accounting for more than 90% of the Earth's total magnetic field. The basic type of geomagnetic field can also be divided into dipole-induced magnetic field and non-dipole-induced magnetic field, in which the dipole-induced effect accounts for the main part, the magnetic field comes from the circulation movement of iron and nickel under high temperature and high pressure environment, and the non-dipole is mainly generated by the self-excited motor effect. The basic geomagnetic field itself also changes, but the period of change is very long, so the Earth's magnetic field as a whole can be considered stable. The changing electromagnetic field is generated in the ionosphere and magnetosphere of the earth, and the magnetic field disturbance is mainly related to the solar change, and the changing electromagnetic field can be divided into stable change and interference change. Quiet changes occur on the solar or lunar calendar and are mainly caused by solar electromagnetic radiation or particle radiation. The phenomenon of magnetic storm is the phenomenon of geomagnetic interference in large space, the main effect of which is the strong change of the ground vector component of geomagnetic field. The abnormal geomagnetic field comes from the ferromagnetic properties of ferromagnetic materials and can be regarded as the constant vector addition on the stable geomagnetic field.

2.Error analysis of electronic compass

Deviation of electronic compass, also known as compass deviation, is the error of measurement results caused by ferromagnetic interference in the nearby environment when the compass is working. The deviation between the measurement results and the real value is even tens of degrees without corresponding compensation link, which is because the magnetic field strength of the earth magnetic field is weak, and the magnetic field strength is only 0.5-0.6 gauss. Therefore, the measurement results of digital compass are very easy to introduce the interference caused by environmental ferromagnetic factors, and the compass has become the main source of error of electronic compass.

Compass can also be divided into hard iron interference and soft iron interference, hard iron interference is caused by permanent magnetic objects or magnetized objects, with a permanent magnetic material under the influence of the external magnetic field, the overall magnetic moment of the object is no longer zero, thus showing magnetism. The magnetic field strength generated by it can be regarded as constant and unchanged in a certain time range, and this permanent magnetic material still maintains a relatively stable residual magnetic field strength after the magnetization effect, even after the external magnetic field action is removed. To sum up, the position and intensity of the interference effect on the compass can be considered as a fixed and constant stabilizing effect, and the compensation means for it is relatively easy to realize.

Summary

Ericco company for aerospace, mining drilling and other engineering projects to provide tools and technical support, the current electronic compass series, ER-EC-360A,ER-EC-365A and other products, with soft magnetic, hard magnetic compensation function, it plays an important role in improving the north finding accuracy. If you want to understand the information of digital compass, you can always communicate with our professionals.