The underground mining environment of coal mine is complex. Once the water supply or gas supply pipes leak, the location and time of leakage are unpredictable. If the leakage can not be found in time, it will seriously threaten the life safety of underground workers. Therefore, it is very necessary to automatically detect the pipeline leakage. In order to solve the problem of automatic detection of coal mine pipeline leakage, this paper proposes an image processing method based on gray level co-occurrence matrix to extract the features of time-frequency image of vibration signal. Firstly, the data in a relatively short time is divided into one frame to reduce the amount of calculation. Secondly, each frame of signal is processed by SPWVD to get the time-frequency image. Then, the time-frequency image after time-frequency analysis is transformed into gray-scale image, and the gray-scale co-occurrence matrix (GLCM) of the image is extracted. Finally, the energy, contrast and correlation of the co-occurrence matrix are extracted and input to SVM for learning and training. Through the design and build of the experimental pipeline to test the algorithm proposed in this paper, the detection result of SVM is 96.67%, which shows that this method can effectively detect the pipeline leakage.
In order to achieve accurate control of the audible sound of the acoustic parametric array in the air, fine phase control of the ultrasonic signal as a carrier is required. By establishing the parametric matrix mathematical model and the directivity function formula, the effects of delay accuracy on the ultrasonic carrier and the audible sound deflection angle are simulated and analyzed. The control of 16-channel phase-controlled parametric array excitation signal is realized by using the fast parallel processing speed of FPGA. The signal processing circuit is designed to D/A conversion and amplification of the parametric array excitation signal to drive the piezoelectric transducer array efficiently. The experimental results show that the system can achieve fine control of the parameter array carrier transmission delay. The control accuracy of the parametric array carrier for the 40KHz carrier is 1 ns, and the error delay is less than 1 ns.
To test the effectiveness of the detection and positioning technology of the pipe leakage, the propagation law of pipeline leakage signal is studied in this paper, and a pipeline leakage signal simulation and generation system is proposed. It can simulate the leakage pressure wave signals at different positions of the pipeline. Changing pipe’s parameters though the computer, the simulation and output of the leakage signal under various working conditions can be realized. It can test the reliability and accuracy of the detection and location technology of the pipe leakage, and verify the applicability of the pipe leakage detection and location technology to different pipe structures. The results show that the output signal of system can replace the real signal, and located the pre-set leakage point by cross-correlation method. The purpose of studying the effectiveness and accuracy of the existing leak location algorithm base on largescale complex pipe network system in laboratory conditions was realized.
Speech transmission index (STI for short) is an important index to evaluate the quality of speech transmission of the room, it can better reflect the degree of voice signal affected by room reverberation and noise in the transmission process.This paper presents an algorithm for directly measuring STI index, white noise is filtered by Paul Kellet filter to generate pink noise, the signal envelope is extracted by wavelet transform, which improves the extraction accuracy of signal envelope and makes the measurement of STI index more accurate.
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