The Eddy Current Testing And Signal Processing Technology Of The Inner Diameter Of Pipe

Accurate evaluation of oil casing losses can effectively avoid the economic loss caused by oil spill.It is of vital practical significance and economic value to calculate the casing inner diameter and permeability of casing which are the important parameters of pipe's defects location and quantification.Based on the theory of multi frequency eddy current signal detection and considering the influence of underground complex environment,in this thesis,the hardware circuit and software are designed,and the results of the experimental data are analyzed and processed.In this thesis,the eddy current impedance model and pipe's physical parameters which based on the characteristics of the eddy current signal are analyzed.The simulation database is obtained through the simulation on the multi frequency eddy current signal by using the large-scale finite element analysis software(ANSYS).The FPGA + DSP architecture is adopted in hardware circuits to implement the function that generating the superposed signal of exciting coil,the conditioning of detected signal,sampling and processing of the analog signal after conditioning and etc.The self-calibration method is applied in the hardware circuit to mitigate the parametric variation and phase measurement deviation caused by the environment change.FFT algorithm is used in sampling and signal processing method to obtain the pipeline's physical parameters of phase difference and LS-SVR(Least squares support vector regression)algorithm is adopted to measured data to get the information of pipe inner diameter and permeability.By taking the experiment in ferromagnetic pipeline with different diameters,it is validated that the function and technical specification has achieved the requirements.According to the experiment results,the effectiveness of the signal processing method has been verified.