Aiming at the need of attitude and heading measurement

a design scheme of attitude and heading reference system（ AHRS） based on quaternion extended Kalman filtering（ EKF） is proposed. This AHRS is consist of low-cost micro-electro-mechanical system（ MEMS） 3-axis gyro

accelerometer and magnetometer

and it uses extended Kalman filtering based on quaternion to fuse sensor data so as to get 3-axis attitude angles. In order to determine magnetometer measurement equation only from magnetic declination and avoid the influence of magnetic inclination

a method using accelerometer to orthogonalize magnetometer data is proposed. In order to reduce measurement error of accelerometer and magnetometer

an ellipsoid fitting method based on least square method is used for correcting of measurement data is adopted. Physical tests show that calibration effect of sensor is good

and this AHRS has relatively high measurement precision and good dynamic characteristics.