Research On Noise Suppression Method In Pipeline Leak Detection Signals

The loss of water resource caused by pipeline leakage not only exacerbated the situation of water shortage in our country, but also buried the hidden dangers for people's living environment, so detecting pipeline leakage in time and positioning the leakage point accurately is particularly important. Because of simple operation and highly efficient detection, correlation detection method based on acoustic signal processing has been widely used in water supply pipeline leak detection and location, in which estimating time delay between the detection signals on both sides of the leakage point is the key of this method. However, when detecting and locating the leakage pipeline, the noise in detection signals will exert an influence on the performance of time delay estimation methods, thus affecting the accuracy of leak localization.Affected by the burst interference noise in detection environment, the leakage detection signal is often local non-stationary. Time-frequency analysis method has good time-frequency locality and can effectively analyze non-stationary signals, so demonstrating unique advantages in noise suppression. In this paper, aiming at the practical engineering in pipeline leak detection, the noise suppression methods are studied. Specific contents are as follows:(1) The characteristics of leak signals and the principle of correlation detection method are studied. The characteristics of noise are analyzed, and its effects on the correlation detection method are studied.(2) The principle and shortage of existing noise suppression methods in pipeline leak detection are studied, noting that time-frequency analysis method has good time-frequency locality and can effectively analyze non-stationary signals, so time-frequency analysis method is proposed to suppress the noise in pipeline leak detection signals and is more suitable for practical engineering of leak detection.(3) The principle and shortcoming of existing signal decomposition methods are studies. The theory of LMD and EMD are analyzed, and the advantages and disadvantages of the two methods are compared from undershoots, overshoots phenomenon and the end effect, which is verified by simulation analysis combined with the corresponding evaluation index. A noise suppression method using LMD and cross-correlation is proposed for leak detection signals.(4) The quantitative analysis of noise suppression effect using LMD and cross-correlation method is carried on. Contrast with the method using EMD and cross-correlation and the method using EMD and correlation coefficient, finding that the method using LMD and cross-correlation can effectively suppress noise even in low signal noise ratio(SNR), and its ability of noise suppression is stronger compared with the other two methods. Amount of actual pipeline leak data under various conditions are collected using the water pipeline network leak monitoring system of our laboratory, and then the above-mentioned three methods are applied to noise suppressing. Experimental results show that the noise suppression method using LMD and cross-correlation can realize pipeline leak location under various engineering environment, and the accuracy is higher, processing by which the relative positioning error is controlled within 1.35%.