Three-axis electronic compass based on GMR sensor

LIN Qian-hao1， QIAN Zheng-hong1， GONG Tian-ping2， BAI Ru1， ZHAN Hong-liang2，
MENG Qing-feng1， SUN Yu-cheng1，3， YANG Chang-mao2
（1. Center for Integrated Spintronic Devices， Hangzhou Dianzi University， Hangzhou 310018， China；
 2. SPINIC Inc.， Yichang 443003， China；
3. School of Material Science and Engineering， Sichuan University， Chengdu 610064， China）

Abstract： Aiming at low accuracy of most of the existing electronic compass，a 3-axis electronic compass measuring system was designed by using giant magneto-resistive（GMR）sensors. In this system，geomagnetic field vector was measured by 3-axis GMR sensors，the pitch and roll angle were measured by accelerometer，the MSP430 microcontroller was used for attitude conversion and heading calculating，and the heading angle data were transmitted from the MCU to the computer through the RS232 interface. Sources causing errors that affecting measurement accuracy of magnetic compass were analyzed，and then related automatic calibration and magnetic field compensation methods were proposed. Three-dimensional rotation calibration was used to get high accuracy under external field interference. The results indicate that，there is an external field or not，the accuracy of a compass can reach 1.5° through calibrated compensation，which demonstrates that the magnetic interference can be effectively compensated．
Key words： electronic compass accuracy； giant magneto-resistance（GMR）； 3-axis electronic compass； compensation algorithm; measuring system