A real-time self calibration approach for tri-axis magnetometers is proposed.The parameterized model of magnetometer readings is established by analyzing the nature of sensor errors,which lays a basis for the derivation of a nonlinear state-space model of calibration parameter using the invariability of local geomagnetic field.The real-time estimation of calibration parameter is derived based on extended Kalman filter(EKF) solution,the U-D decomposition filter is given for ease of implementation.Compared with the batch approaches,the proposed method not only can achieve real-time estimation of calibration parameters,but also is convenient for embedded implementation.Simulation results demonstrate the correctness of the derivation of the proposed approach.The effectiveness is validated by experimental test using RM3000 tri-aixs magnetometer.The results of simulations and experiments are analyzed and concluded in comparisons with TWO-STEP method.
[1] Beravs T,Begu S,Podobnik J.Magnetometer calibration using Kalman filter covariance matrix for online estimation of magnetic field orientation[J].IEEE Transactions on Instrumentation and Measurement,2014,63(8):2013-2020.
[2] 彭孝东,张铁民,李继宇,陈瑜.基于传感器校正与融合的农用小型无人机姿态估计算法[J].自动化学报,2015,41(4):854-860. Peng X,Zhang T,Li J,Chen Y.Attitude estimation algorithm of agricultural small-UAV based on sensors fusion and calibration[J].Acta Automatica Sinica,2015,41(4):854-860.(in Chinese)
[3] Gebre-Egziabher D,Elkaim G H,Powell J D,et al.A non-linear,two-step estimation algorithm for calibrating solid-state strapdown magnetometers[A].International St Petersburg Conference on Navigation Systems[C].IEEE,2001.28-30.
[4] Foster C,Elkaim G.Extension of a two-step calibration methodology to include nonorthogonal sensor axes[J].IEEE Transactions on Aerospace and Electronic Systems,2008,44(3):1070-1078.
[5] Zhitian Wu,Xiaoping Hu,Meiping Wu.Attitude-independent magnetometer calibration for marine magnetic surveys:regularization issue[J].Journal of Geophysics and Engineering,2013,10(9):1-9.
[6] Valerie R,Muhammad A,Gerard L.Complete tri-axis magnetometer calibration in the magnetic domain[J].Journal of Sensors,2010,56(6):1-11.
[7] Vasconcelos J,Elkaim G,Silverstre C,et al.Geometric approach to strapdown magnetometer calibration in sensor frame[J].IEEE Transactions on Aerospace and Electronic Systems,2012,47(2):1293-1306.
[8] Bertrand G,Ali Z,Mohamed B,et al.Real-time attitude-independent three-axis magnetometer calibration for spinning projectiles:a sliding window approach[J].IEEE Transactions on Control Systems Technology,2014,22(1):255-264.
[9] Crassidis L,Lai L,Harman R.Real-time attitude-independent three-axis magnetometer calibration[J].Journal of Guidance Control Dynamics,2005,28(1):115-120.
[10] Wahlstrom N,Gustafsson F.Magnetometer modeling and validation for tracking metallic targets[J].IEEE Transactions on Signal Processing,2014,62(3):545-556.
[11] Bierman J.Factorization Methods for Discrete Sequential Estimation[M].New York:Academic Press,1977.
[12] Bruce G.Advanced Kalman Filtering,Least-squares,and Modeling[M].New Jersey:John Wiley&Sons,2011.
[13] Ren F,Zhang C,Liu L,et al.A square-root-free matrix decomposition method for energy-efficient least square computation on embedded systems[J].IEEE Embedded Systems Letter,2014,6(4):73-76.
2017, Vol. 45 
