基于实Laplace小波的脉冲涡流检测系统特性分析

Characteristic analysis of pulsed eddy current testing system based on real Laplace wavelet

研究脉冲涡流检测等效模型及其系统特性对提高仪器检测性能具有重要作用,首先针对现有模型中存在的不足,将脉冲涡流传感器和被测试件简化为RLC电路等效模型,指出因试件壁厚和传感器提离的波动而引起的模型中电感和涡流损耗的变化,均会在固有频率和阻尼比等系统特性上得到体现。然后基于Laplace小波特性的理论分析,选取实小波对脉冲涡流检测信号进行分析,给出了根据检测信号选取支集起点及结合参数向量确定支集长度的方法。最后搭建脉冲涡流试验台获取实际检测信号,用实Laplace小波对试验信号进行分析,得到了系统特性随试件壁厚和传感器提离变化的规律,为研究脉冲涡流检测系统的特性提供了新的途径。

The research on the equivalent model of pulsed eddy current testing and its system characteristics plays an important role in improving the detection performance of the instrument. In this study, firstly, aiming at the deficien- cies of the existing equivalent model, the pulsed eddy current sensor and test specimen are simplified to a RLC equiv- alent circuit model. Hence, the inductance and eddy-current loss variations in the equivalent circuit model caused by the variations of specimen thickness and sensor lift-off can be reflected in the system characteristics, such as the natu- ral frequency and the damping ratio. Secondly, based on theoretical analysis of the Laplace wavelet characteristics, the real Laplace wavelet is employed to analyze the pulsed eddy current testing signals. The methods of selecting the starting point of support and determining the length of the support are given according to the testing signal and the pa- rameter vector. A pulsed eddy current experimental platform was built to obtain the testing signals, the real Laplace wavelet was used to analyze the testing signals, and the laws of the system characteristic variation with specimen thickness and sensor lift-off were obtained. This work provides a new way to study the pulsed eddy current testing sys- tem characteristics.