Design And Research On High Precision Electronic Compass Based On Anisotropic Magnetoresistance

Electronic compass,also known as digital compass,is mainly used for instument geomagnetic navigation,aircraft,ship attitude adjustment and so on.In navigation,the electronic compass avoids the influence of electromagnetic wave propagation and the loss of satellite signal.The stability and convenience of the use of electronic compass is a major feature of the rapid integration of electronic compass into human life.In addition,because the navigation is based on the perception of the geomagnetic field,the study of geomagnetic field has gone through many generations,and the related information and laws of geomagnetic field have been thoroughly understood and mastered.Therefore,in the research,the electronic compass can achieve the goal of high precision.This research is based on anisotropic magnetoresistance effect to realize electronic compass.Anisotropic magnetoresistance sensor has the advantages of small size,light weight and simple structure,and its detection output linearity and sensitivity are higher than other types of magnetoresistance sensors in the weak magnetic field area.It is especially suitable for the detection of geomagnetic field.Aiming at the inclination of the electronic compass's angle and posture during its actual use,a three-axis accelerometer is added to the design to describe the inclination of the electronic compass.Based on the principle of calculating the azimuth angle of geomagnetic field in three-dimensional state,the data acquisition module LSM303DLH integrated with magnetoresistive sensor and three-axis accelerometer is used as the signal acquisition module to realize the sensitive acquisition of geomagnetic field and acceleration variables.The position reset circuit is added to prevent the polarization reversal of the magnetic field under the disturbing magnetic field.STM32F767IGT6 is used as the micro-control unit to control the frequency of data acquisition and the component of magnetic field intensity and acceleration.The rotation matrix description of the tilt posture of the electronic compass is obtained.The azimuth angle is calculated by the algorithm.Keil uVision 5 software development environment is used in software design and development.RDY signal is confirmed before data transmission,and magnetic field and acceleration are collected independently.Synchronization primitives are used to implement thread or process exclusive memory,and memory update sequence is executed.The SLEEPDEEP bit of SCR register is used to switch the sleep mode and reduce the power consumption of the system without running the program.For the hard magnetic interference and soft magnetic interference existing in the use of electronic compass,the optimal elliptical compensation method is adopted in the research.The ellipse is first approximated to a circular one,then the deviation value is solved.Finally,the stable azimuth angle detection and output of electronic compass under the interference field of 10 times geomagnetic field are realized,and the error angle is less than 1 degree.