A Research Of Modification And New Algorithm Of Aeromagnetic Compensation Model

Magnetic anomaly signal detection technology is widely used in our life.Ferromagnetic objects generate induced magnetic fields under the influence of the earth’s magnetic field,which affect the distribution of the surrounding magnetic fields,this is the magnetic anomaly.Magnetic anomaly signal detection has the advantage of not being affected by the hydrological environment,therefore,it has attracted much attention in ocean exploration,aerial geophysical exploration,etc.Since the detection platform contains ferromagnetic materials and is very close to the detection instruments,the interference magnetic field generated by the aircraft is much larger than the magnetic field of the target signal,which is not good for the detection of the target signal.Therefore,it is important to compensate for the interference magnetic field.First,the thesis introduces the influence of the ambient magnetic fields in the aeromagnetic compensation,which mainly includes the geological magnetic field and the diurnal magnetic field.The thesis uses the Enhanced Magnetic Model to calculate the geological magnetic field.The type of diurnal magnetic field is color noise,and it can be converted into white noise by whitening filtering,which is beneficial to solve the compensation coefficients.Then the thesis analyzes the shortcomings of the Tolles-Lawson model,which was established under the assumption that the aircraft is a rigid body structure.However,the aircraft is not an ideal rigid body structure when performing maneuvering actions and turning.When the aircraft is deformed,the state of the aircraft also changes.Furthermore,the metal material on the aircraft will generate the electric current,which will generate interference magnetic field.It is also necessary to correct the data measured by the fluxgate magnetometer because of nonorthogonality and zero drift of its three components.Finally,an improved model is obtained.Using the data measured on the ground,it is found that the residual interference after compensation is reduced to half of that of the Tolles-Lawson model,and the improvement ratio is about doubled.Using the real flight data to simulate,the residual magnetic field after the compensation of the improved model is reduced by about 10 Pitts compared with the compensation of the Tolles-Lawson model,this shows that the improved model is useful.The thesis also introduces the research on the aeromagnetic compensation algorithm.By comparing some algorithms for solving magnetic compensation coefficients,it is found that the compensation effects of these algorithms are similar;then the thesis proposes a method of segmented compensation,which separates the compensation coefficients in the straight flight stage and the turning stage.It can be seen from the results that the coefficients calculated by data in the straight flight stage is more accurate than the overall coefficients,and the compensation result is slightly better for straight flight stage;however,the compensation coefficients obtained by data in the turning stage is not ideal.Therefore,the interference and geomagnetic gradient field are modeled,and the compensation coefficients are used for the turning stage compensation.From the experimental results,the residual magnetic field after compensation is basically near zero,it can be seen that the compensation result of the method is good.Finally,for the future research of aeromagnetic compensation technology,the thesis put forward some problems and the next research plan.