Research And Prototype Implementation Of Transient Electromagnetic Detection For Distribution Tower Base

Transient electromagnetic method(TEM),also known as time domain electromagnetic method,uses ungrounded return line or grounded power supply to send an electromagnetic pulse to the object to be detected,and receives the secondary magnetic field generated by the object to be detected,so as to achieve the purpose of metal detection.Transient electromagnetic method,as a kind of technology which uses the fast transient space electromagnetic field to detect the target object,is widely used in many fields,such as security,engineering exploration and so on.It has a good effect of improving the detection efficiency and saving human and material resources.Based on the principle of TEM,according to the common character of TEM detection device,starting with the coil system of such device,this paper analyzes the influence of coil geometry,and establishes the magnetic field coupling model of coil and the object to be detected as well as the corresponding circuit model;secondly,in view of the problem of induced voltage oscillation of the receiving coil,the coil turns are taken into account Based on this model,the measurement method of parasitic capacitance and the selection standard of damping resistance for suppressing oscillation are proposed.Thirdly,for the detection object with complex coupling relationship,the traditional transient electromagnetic method has poor detection effect.The original coil system is improved by introducing decoupling coil to improve the resolution of the system Then the equivalent model of the decoupling coil system is established and its advantages are pointed out.In the aspect of finite element simulation,the base bottom,pull and chuck of distribution tower are selected as the detection objects,and the traditional TEM detection device and the improved detection device coil system are simulated respectively.In the simulation process of the traditional detection device,the factors such as the position of the coil system,the coupling relationship,the coil size,the buried depth of the detection object,and the change rate of emission current are mainly considered In the simulation process of the detection system,in addition to the above factors,the influence of decoupling effect on the detection accuracy is also considered.The simulation results well show the necessity of introducing decoupling coil,and confirm the results of the previous model analysis.In the aspect of prototype implementation,FPGA is used as the control unit to provide the control and trigger signal,ARM processor is used as the signal processing operation core to refresh the human-computer interface control and the post-processing part of the induced voltage signal of the coil system.The human-computer interface of the prototype is realized by using the em Win framework of SEGGER corporation in cooperation with the μC/OS-III system.The signal acquisition,interface refresh,waveform adjustment,data saving and processing and other links are completed in the form of system tasks.The test results of the prototype show that the TEM detection device with decoupling coil can complete the resolution of the detection objects such as the distribution network tower base,and achieve the established detection objects.