| The ground-airborne frequency-domain electromagnetic method combines the advantages of high detection efficiency of airborne electromagnetic method and large transmitting power of the ground electromagnetic method,which has developed rapidly in recent years.But,this method acquires underground resistivity information by receiving vertical magnetic field signal in the air.The vertical magnetic field in the air is relatively weak and attenuates rapidly with the increase of transceiver distance.Secondly,since the sensor moves in the air to receive signals,the sensor will produce attitude changes and couple other component signals to introduce attitude noise.At the same time,the load capacity of the rotor aircraft is low,so the weight of the sensor is required.This paper has done the following work for the above problems:1)To determine the design requirements of the sensor,this paper introduced the principle of ground-airborne frequency-domain electromagnetic method and analyze the characteristics of its response signal.We analyzed the basic principle of measuring magnetic field signal by air-core coil sensor,and the sensitivity calculation formula air-core coil sensor was given.Then we determined the damping state suitable for ground-airborne frequency-domain electromagnetic method.2)We developed the optimal design method of optimal design air-core coil sensor.And we established the mathematical model of the inner resistance,distributed capacitance,inductance,matching resistance and weight of the air-core coil.A differential preamplifier circuit was designed based on the source impedance characteristics of the hollow coil.Then,the equivalent noise model of the air-core coil sensor was established.On this basis,we analyzed the relationship between sensor equivalent voltage noise and coil turns and diameters.Finally,for practical application needs,an optimization design model of sensor noise based on weight constraints was established and we got the optimal solution.3)We designed a three-component air-core coil sensor.Aiming at the crosstalk problem between each component sensor,the corresponding simulation analysis was carried out,and then the vertically concentric three-component coil structure was determined.Then,we quantitatively analyzed the non-orthogonal angle's influence of the three-component coils on the attitude correction of the acquired vertical magnetic field signals.The simulation results show that the motion noise can be reduced to less than 1% by the attitude correction and the influence of non-orthogonal angle on system measurement could be ignored.4)The sensor developed in this paper has been tested and applied in the field.The sensor sensitivity calibration and noise test experiments were carried out in the shielding room,and the experimental results were consistent with the theoretical analysis.In addition,a field comparison experiment was conducted in Leshan town of Changchun city using the sensor mentioned in this paper and amtc-30,and the experimental results verified the accuracy of the measured signal of the air-core coil sensor in this paper.Finally,we completed the flight experiment and field engineering application,and achieved good measurement results. |
PDF Full Text Request