On Research On Location System Of Outer Armored Cable Based On Transient Electromagnetic Method

Oil is an important strategic material and an important component of China’s economy.In the process of mining,it is necessary to perforate the oil.In order to prevent shooting through the armored optical cable outside the casing,it is necessary to detect the orientation of the optical cable,which is now a hot research issue in oil mining.At home and abroad,in-depth research has been carried out in this field,this paper has a high theoretical and application value.In order to detect the bearing,the external optical cable is detected in the tube,and the commonly used methods are studied.By comparison,the electromagnetic induction measurement method is used for positioning design.Three different positioning methods are designed according to the position of the induction source and the material of the excitation source,namely,the external current method,the permanent magnet method and the transient electromagnetic method(TEM).Using ANSYS Maxwell,mechanism models of the three methods were established respectively.Through simulation and comparison,it was known that the excitation current required by the external electrification method was too large,which was difficult to operate in the laboratory.The permanent magnet method has low response and is easy to introduce noise.Transient electromagnetic method requires simple excitation and obvious response law,so it is finally decided to use it.In terms of theoretical analysis,the expressions of induced primary and secondary fields under the excitation of transient electromagnetic signals are derived from the law of electromagnetic induction and Maxwell’s equations.Meanwhile,in order to facilitate quantitative analysis,the expressions of response conversion in time domain and frequency domain are derived by Fourier transform,and the effectiveness of the method is verified by simulation experiments.On the basis of theoretical analysis,the hardware circuit of optical cable positioning system is built with STM32F429 as the main control chip.The transmitting circuit and receiving circuit are designed in the form of coil and mandrel.The mandrel has been verified by simulation and is designed as a long U-shaped DT2 material mandrel.The driving circuit of the transmitting circuit is built in the form of H bridge,which can generate bipolar pulse excitation square wave through the control of single chip microcomputer.The signal conditioning circuit includes a pre-filtering circuit,a pre-amplifying circuit,a sampling integral amplifying circuit and a two-stage filtering circuit.Considering that the positioning is the sheathed cable outside the casing,the high frequency signal is difficult to penetrate,so the filter circuit is designed as a low-pass filter circuit,because of the low signal-to-noise ratio of the received signal,using ADG509A and ADG201A to build a multi-point sampling integral circuit,as far as possible to extract the signal from the noise.Finally,an experimental environment is built in the laboratory,and a set of values are collected every certain Angle.The position of the external optical cable can be judged according to the amplitude of the late signal from different angles.The data collected from each Angle is uploaded to the upper computer program for processing,and the required azimuth information is calculated,which has reached the expected accuracy requirements.