Design Of A Multichannel Acoustic Emission Monitoring System

Since the coal mining,the occurrence of mine accidents is more frequent,resulting in economic losses,threatening the safety of personnel.Acoustic emission technology is a new dynamic nondestructive testing technology,which can be used for long-term monitoring to achieve early warning effect and reduce the occurrence of security problems.The multi-channel acoustic emission monitoring system in this paper is based on the principle of acoustic emission,through acquisition,conversion,transmission,positioning and other processing,to achieve the display of acoustic emission source waveform complete the positioning of acoustic emission source.The main work is as follows:(1)Signal acquisition and processing.After each channel current output sensor is encapsulated,the acoustic emission source signal is collected.After the current to voltage,filtering and other processing,the time-domain signal is transformed into the frequency-domain signal storage by FFT transformation to reduce the data transmission volume and ensure the reliability of the signal.When receiving the data transmission instruction from the upper computer,the lower computer of each channel transmits the data of a data acquisition and processing cycle to the upper computer by polling through 485 bus according to a certain format.(2)Display of processed signals.The upper computer processes the data transmitted by the lower computer of each channel,displays the data in the form of waveform in dynamic real-time,and displays the accumulated number of large events,the number of large and small events in a data acquisition and processing cycle,the arrival time of the first large and small events after the system starts to run.In case of abnormal events,the system will give an animation and prompt tone warning prompt.(3)Analyze the data and complete the positioning.In the experimental area of 3m*3m*3m,the target source location algorithm based on time delay estimation is used to analyze the acquired multi-channel signal data through time delay estimation and location technology.The second correlation method is used to reduce the influence of noise on the signal and improve the accuracy of time delay estimation.The distance between each acoustic emission probe and the acoustic emission source is calculated by using the data processed by the upper computer and the position coordinates of each acoustic emission probe of each channel,and the estimated position of the acoustic emission source is obtained.Through the comparative analysis of the estimated values of multiple acoustic emission sources and the actual position of the acoustic emission source,the average errors in the x-axis,Y-axis and z-axis directions are all within 0.1 m.