Design And Optimization For The Transmitter And Receiver Structures Of Transient Electromagnetic Method

Mine water-burst disasters always seriously affect the safe of workers and the security of production coal mine. Therefore, it is very important for us to improve the detection methods to enhance the capability of preventing and controlling the mine water disaster. At present, the main methods for detection the mine water-burst include hydrological borehole, mine direct current electric method, transient electromagnetic method and geological radar.Because the transient electromagnetic method (TEM) has the advantages of rapid and convenient operation, highly Directivity, long detection distance and sensitive to the low resistivity region, it has been widely used in the forecast of water disaster in coal mine. However, there are currently still many technical problems difficult to be solved, such as the short effective detection distance and the weak reception capability for the weak electromagnetic fields reflected. In order to solve the problems, this paper mainly carried out the works for design and optimization the transmitter and receiver structures of transient electromagnetic method. The main works are as follows: (1) The8-shaped transmitter coils is design in this paper, and the Finite Element Analysis software (MAXWELL) is used to simulate the transmitter coils of8-shaped and square. By comparing the magnetic flux density of two transmitter coils under the condition of different currents, we can find that the8-shaped coils has a strong ability to focus on target in long distance, and it can also generates stronger magnetic field intensity in short distance.(2) The Field-Programmable Gate Array (FPGA) was used to design the transmit circuit of transient electromagnetic. The module of EXB841was introduced to drive the MOSFETs, which located on the up-down side of H-bridge. The turn-off time for MOSFET can be greatly shortened using the innovative H-bridge and control strategy. At the same time, the RCD protect circuit was utilized to decrease the interference of surge voltage, which can improve the output wave of circuit. The measured results show that the output signal of electromagnetic transmitter is rectangular wave.(3) To improve the ability of receiver structure, the high sensitivity magnetic probe is used for the receiver in TEM system. At the same time, the multi-array receiver structure is proposed for improvement the receiver system, which can precious detect the positioning of target by comprehensive analysis of multiplex signals. At the same time, in order to improve the resolution of equipment, the24bits A/D converter is used for the circuit of packing-up signal.The measured results show that the magnetic probe has better resolution for detection the positioning of target in the vertical direction, comparing with the receive coil. Moreover, the magnetic probe displays apparent resistivity in the experiment of advance detection, and it also shows higher sensitive for the high resistance region.