Development Of Three-axis Electronic Compass Based-on Magnetoresistive Sensor & Accelerometer

Electric compass is a device for attitude measurement based on geomagnetic field and gravity. It has the advantages of very small size, simple architecture, low cost and low power consumption, etc. And it has expansive future in the field of navigation, orienteering, deep exploration and weather monitoring, etc. A tilt-compensated three-axis electronic compass has been developed based on anisotropic magneto-resistive sensor and accelerometer. In order to improve the accuracy of electronic compass,some researches on both design and method have been done in this thesis.This thesis has introduced the measurement principle of electronic compass, and established the mathematical model of three-axis electronic compass. By comparing with various of weak magnetic measurement,magneto-resistive sensor HMC1021/1022 and accelerometer ADXL202E are used to obtain signal for electric compass. With the analysis of sensor performances, a variety of measures to enhance the accuracy of electronic compass have been taken, including the optimization and improvements of the hardware design on power supply, signal processing, set/reset of magneto-resistive sensor, bias cancelling, and other aspects. Meanwhile, the research and design of the software in electronic compass have been presented in this thesis as well, including data acquisition, digital filtering, attitude calculating, and communication protocol compatible with NMEA0183 standard,etc.The errors of electronic compass have also been analysed. Both the twelve-attitude calibration method and the ellipse hypothesis have been used for the error compensation. To ensure the reliability and anti-jamming capability of the compass, many methods based on hardware,software and handicraft have been adopted.After the electronic compass prototype has been developed successfully, a testing scheme is designed, in order to examine the feasibility of compass design and the effect of error compensation. Finally, a comparison test has been implemented between the prototype and HMR3000, which is made by Honeywell in America. The experiment result shows that the tilt accuracy of the prototype is±0.3°in the tilt range of±60°, and the azimuth difference between the prototype and HMR3000 in horizontal attitude is no more than±0.7°. The achievements of this thesis can be as reference and helpful for further research of electronic compass.