A calibration method for magnetic sensors and accelerometer in tilt-compensated digital compass

A calibration method for the outputs of magneto-resistive sensor and MEMS accelerometer in a tilt-compensated digital compass is introduced in this paper. Besides the magnetic deviation, the system errors of digital compass are generally affected by offsets, scale factors and misalignment errors of the sensors. The proposed method uses Poisson's equations of magnetic deviation to describe the errors of the magneto-resistive sensor and MEMS accelerometer in a tilt-compensated compass, while using the Earth's magnetic field and the acceleration of gravity to accomplish the calibration within 12 attitudes. The proposed method is applied to a digital compass module that consists of HMC1021/1022, ADXL202E, TLC2543 and STC12C5408. The maximum heading error is reduced from more than 23 degrees to 3 degrees after the calibration.