Analysis And Improvement Of Aeromagnetic Compensation Algorithm Based On T-L Model

Aeromagnetic exploration is an important method of geophysical exploration,which is widely used in geological research,mineral exploitation,submarine detection,and unexploded detection.However,in the process of aeromagnetic exploration,the magnetic interference generated by the flight platform will affect the measurement value of the magnetometer,so the technology of aeromagnetic compensation must be used to remove the effect.The traditional aeromagnetic compensation methods are mainly based on the Tolles-Lawson(T-L)model.The T-L model divides the magnetic interference of the aircraft platform into the permanent field,the induced field,and the eddy current field.The overdetermined linear equations are established by the data collected from the optical pump magnetometer and the three-component magnetometer,and magnetic interference coefficients are calculated.The magnetic interference is estimated by the coefficient,to complete the compensation of the aeromagnetic detection data.In the process of solving the T-L model,the model has some problems such as ill-conditioned,non-uniformity of the geomagnetic field,and time-varying characteristics of the model,which will reduce the accuracy of the solution.As for above problems,the main research work of this paper is as follows:Firstly,aiming at the ill-conditioned problem of the model,a Tikhonov regularized aeromagnetic compensation method is proposed,and the optimal regularization parameter is obtained by the L-curve criterion.An in-depth analysis of the ill-conditioned T-L model illustrates that the use of Tikhonov regularization can ensure the stability of the solution.The experimental results show that the compensation algorithm based on Tikhonov regularization can effectively reduce the influence of the ill-conditioned,so that we can obtain stable and high-precision compensation coefficients.Secondly,since the uniform distribution of geomagnetic field is inconsistent with the non-uniformity of actual geomagnetic field in the T-L model,the geomagnetic field component existing in the aircraft maneuver coupling in the filtered magnetic interference is analyzed,which reduces the accuracy of the coefficient.In the paper,the geomagnetic field is modeled using a two-dimensional Taylor model.Finally the established geomagnetic gradient model is combined with the T-L model,and an aeromagnetic compensation method that the extend T-L model is proposed.Finally,the small-signal method is deduced based on the T-L model.The small-signal decouples the 16 equations in the T-L model into two groups of 8equations,which reduces the influence of the ill-conditioned T-L model.Considering that the magnetic field model coefficient of the actual aircraft will vary with time and the influence of environmental noise,the paper proposes an aeromagnetic compensation method combining the variable forgetting factor recursive least squares and the small signal model,which provides a new compensation idea for aircraft attitude changes in small angles.