## Magnetic tensor compensation method for the carrier of the magnetic tensor detection system

**ZHANG Guang;ZHANG Ying-Tang;YIN Gang;REN Guo-Quan;LI Zhi-Ning;FAN Hong-Bo;Department 7th,Mechanics Engineering College;Unit 65185 PLA;**

To solve the problem that the measurement accuracy of the magnetic tensor detection system is influenced by the magnetic tensor generated by the carrier,and existence of nonlinearity,separated patterns and too many coefficients in the existing compensation model,this work proposes an integrated linear compensation method for the magnetic tensor carrier.First,the magnetic tensor system is built,and the whole magnetic tensor is replaced by the expression of 5elements.The magnetization characteristic of the hard magnetic material that comprises the carrier is analyzed,and the connatural magnetic field from carrier hard magnetic material does not vary with the change of carrier attitude and position.The mathematic model of the connatural magnetic field is constrcuted.The mechanism of the induced magnetic field from carrier soft magnetic material is analyzed,and the induced magnetic field is equivalent to the magnetic field superposition of several magnetic dipoles.The mathematic expression of the induced magnetic field is derived.The carrier magnetic tensor compensation model is established combined with the influence of the connatural magnetic field and the induced magnetic field,andthe magnetic tensor compensation model with 20 coefficients is established by variable substitution and combined reduction.If we rotate the magnetic tensor system and carrier more than 4attitudes under the equal magnetic field environment,and put the measured value of the magnetic tensor and magnetic field components into the carrier magnetic tensor compensation model,we can get the 20 magnetic tensor compensation coefficients.When the magnetic tensor system is applied to search the target,we can calculate the magnetic tensor value of the carrier with the 20 magnetic tensor compensation coefficients and the three components of the magnetic field.The magnetic tensor value of the target can be determined with the total magnetic tensor value subtracting the magnetic tensor value of carrier,and the carrier magnetic tensor compensation is realized.On the wide lawn,the magnetic tensor system is fixed on the three-axis non-magnetic turntable,apiece of iron of 0.003 m3 as the simulation carrier is put on the this turntable also with a certain distance from the magnetic tensor system.The three-axis non-magnetic turntable is rotated at different attitudes(to get more calculation accuracy,10 attitudes are carried out),the measurement data of the magnetic tensor system are recorded.Using the magnetic tensor compensation method of this paper,the 20 magnetic tensor compensation coefficients of the simulation carrier are obtained with the measurement data.To test the validity of this compensation method,the three-axis non-magnetic turntable is rotated at another 4attitudes,and the magnetic tensor value from the simulation carrier can be got with the 20 magnetic tensor compensation coefficients and the three components of magnetic field measured by the magnetic tensor system.The influence of the magnetic tensor of the simulation carrier is up to 653nT/m before compensation,and the general targets can be submerged by it.After compensation,the influence is reduced to 32nT/m,and to a certain extent,the magnetic tensor of the simulation carrier is compensated.In this paper,the carrier magnetic tensor compensation model considering the connatural magnetic field and induced magnetic field is established.The model includes 20 magnetic tensor compensation coefficients,which can be solved by the model and the measurement data.The magnetic tensor generated by the carrier can be calculated using the 20 compensation coefficients and the three components of the magnetic field,and the carrier magnetic tensor compensation is realized.It is proved that the calculated magnetic tensor is very close to the real ones of the carrier by real measuring experiment,and the compensation method in this paper can effectively accomplish carrier magnetic tensor compensation.

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