Design And Research Of Three-dimensional Electronic Compass Based On Magnetoresistive Sensors

Three-dimensional electronic compass is an important device for navigation using theearth’s magnetic field and the acceleration of gravity to achieve directional function. it canprovide carrier pitch angle, roll angle and heading angle of real-time, So it is widely used inaviation, navigation, vehicle location, geological exploration, deep-sea exploration and otherfields. Electronic compass has many significant advantages, such as miniaturization,integration, output electrical signals and thus it can be easily cascade with other electronicequipment. Widely used in microcontroller today, the effective method to improve theperformance of electronic compass is to realize the integration and intellectualization useingmagnetoresistive sensor and MCU. This paper is designed for three-axis magnetic resistancetype electronic compass, which has the function of slope angle compensation.Based on the generation of the magnetic field and the theory of geomagnetic navigation,with three dimensional electronic compass as the research object, this paper mainly introducesthe following research: Firstly, on the basis of principle of overview of geomagneticnavigation, we analyze the working principle of the three-dimensional electronic compass, thethree-dimensional structure of electronic compass is determined which is consisted by attitudemeasurement, heading angle measurement and data processing of the three modules. Secondly,the article analyzes the measuring principle and the work of magnetic resistance sensor andacceleration sensor. The design thought and implementation method of each module of thethree-dimensional electronic compass system are mainly introduced. The headingmeasurement front-end module select Honeywell’s three-axis magnetoresistive sensorHMC58883L. The attitude measurement front of the module choose Analog Devicesthree-axis gravity accelerometer sensor ADXL345. With the change of the compass direction,posture, magnetic resistance sensor sensitive axis of the geomagnetic field measured valueschanges. Through the compensation of attitude angle measurement module, we can get statecorresponding to the direction of the compass level instructions. With the digital signalcontroller dsPIC30F2010as the core, the design of each function module of software andhardware are made. Thirdly, the writing of the program, compiled, and the hardware andsoftware of alignment are realized in MPLABIDE development environment; Finally, for avariety of possible errors are analyzed, and the corresponding compensation and suppressionmethod are made, and the debugging is completed to accomplish the design andimplementation of three axis magnetoresistive electronic compass at last. The system through integrated test, the results show that, the electronic compass candynamic measuring angle, pitch angle and roll angle of the implementation course, themeasurement accuracy of±2°, within the range of0°to360°, the resolution can reach0.1°.The design of three-axis magnetoresistive electronic compass has the advantages of small size,light weight, low power consumption and low cost, further improve can be used in the broaderfield.