混凝土检测中基于数字滤波的传感器补偿方法

在超声探测中,为了获得信号最大响应幅度,通常都选用传感器的谐振频率作为探测频率.然而,这样会给探测信号带来较严重的振铃效应,影响反射信号的识别与提取,从而降低探测分辨力.本文提出了一种基于数字滤波方法,有效地对不理想的超声传感器频响特征进行了补偿.首先基于系统辨识算法建立了发射和接收传感器的离散传递函数模型,然后通过一个数字补偿滤波器建立补偿模型,用于抑制传感器的振铃效应.对这种方法的实际效果进行了实验验证,通过水浸测试获得传感器的标定数据,并基于这些数据建立补偿模型.实验结果表明混凝土底面反射信号能够从原混叠信号中被清晰地识别.

Compensating Method for Transducers Based on Digital Filtering in Concrete Test

In ultrasonic pulse-echo NDT of structures, the transducers usually operate in their harmonic frequencies to maximize the amplitude response. However, there exist some ringing effects in such mode. A digital filtering method is used to compensate the unwanted frequency response characteristics of ultrasonic transducers. Firstly a discrete transfer function model is established for transmitting and receiving transducer system based on system identification algorithms. Then the established model can be realized by a digital compensation filter and used to reduce unwanted effects of the measured signals. The experiment is verified by the proposed method. The experimental data are obtained in a calibration process by water-immersion test of the transducers and a compensation model is established. Finally the established model is used to the thickness measurement of a concrete specimen by low-frequency ultrasonic method. With the digital compensation approach, results show that the reflection from bottom of the concrete beam can be well separated from the original overlapped complicated signals.