Design Of Control System For Dual Sources Array Emission Method

Artificial field source electromagnetic detection method plays an important role in exploration of the mineral resources,oil and gas resources,geothermal resources and engineering geological survey.The efficient,convenient and rapid survey method has become an important research field in geophysical exploration methods.Frequency domain semi-airborne electromagnetic method layouts high power emission system on the ground and employs aircraft equipped with a magnetic receiver to collect the magnetic field.In this way the instruments can enter the sea land belt,the mountain area,and other complex measurement areas,which greatly improves the work efficiency compared with the way acquisition mode on the ground.Because of the distinctive operation mode with the magnetic receiver equipped by the aircraft,the motion noise and electromagnetic noise lead to the cut down of the signal to noise ratio of the received signal,which limits the transceiver distance and the instrument can't be measured in the far zone where the incident wave can be approximated to the plane wave and vertical incidence.This paper mainly aims at the problem of low signal noise and limited transceiver distance which leads to the low SNR in the present frequency domain semi-airborne electromagnetic method.From the point of the view of the emission source,the electromagnetic field signals in the air are superimposed by using dual-source which will enhance of electromagnetic field response in the pending area to expand the detection range.The main work of this paper is as follows:1.Introduces and analyzes the operational principle of the frequency domain semi-airborne electromagnetic method and discusses the forward calculation method.Using the Maxwell equation to derive the expression of the H_z component and the numerical integration method is used to calculate electromagnetic field response,which lays the foundation for the next step of research.2.Using the COMSOL software to calculate the electromagnetic field of the target area which aims at the excited electromagnetic field by single and dual-source.Through comparative analyses:multi-source can increase in multiples intensity of the electromagnetic field in the target region.At the same time,under the weak signal detection level of the instrument,the enhancement of the electromagnetic response signal can increase the transceiver distance and expand the detection range of the frequency domain semi-airborne electromagnetic method.3.A circuit model of dual-source emission is built.The simulation of the Circulation problem caused by the phase difference of the emission current in the multi-source emission process is completed.The calculation results shows:the existence of the Circulation causes the magnetic field can't be able to form effective vector superposition,there will be a large deviation of the amplitude and phase between the collected magnetic signal.The method of using GPS to eliminate Circulation,to meet the practical application demand,the phase error of the emission current is no more than 1 degree,and the drive circuit of the emission system has been design.4.The control system of transmitter has been designed,the control waveform of and the hardware system are completed.The GPS synchronization has been used to complete the synchronization between the driving signals.The experimental test shows:the synchronization error of the multisource emission current is not more than520ns,which satisfies the design requirement,effectively inhibits the Circulation,enhance the electromagnetic field response in the pending area and expand the detection range.At the same time,the time-frequency fusion current waveform can effectively excite the transient and steady response,which meets the requirements of the simultaneous measurement of the two electromagnetic methods.