Research On Acoustic Level Detection Method Based On Pulse Compression Technology

With Material level detection technology is widely used in modern industrial process control.Common material level detection methods include heavy hammer,ultrasonic,radar,laser,etc.,but the detection results are not ideal in high dust environments such as large raw coal bunkers and cement silos,and most of them are unsatisfactory.Only single-point detection can be achieved.At present,foreign products have realized the three-dimensional distribution detection of material level based on the sound wave detection method.The penetration of high-concentration dust is realized by using the characteristics of the large wavelength of the sound wave signal,and the mechanical vibration caused by the sound wave excitation The detection head has the self-cleaning ability,but the detection accuracy and accuracy of the three-dimensional distribution of the material level still needs to be improved.This paper focuses on the signal processing method of acoustic material level detection in large silos with high dust environment.The main research contents include:(1)An echo position detection method based on chirp compression is proposed.Aiming at the need of echo signal position detection and the problem that the environmental noise has a great influence,the influence of various processing methods such as median filter,wavelet transform,Wiener filter,cross-correlation algorithm,linear frequency modulation and other processing methods on the position detection accuracy is analyzed and compared.The results show that the signal processing method based on chirp has better signal-to-noise ratio and lateral resolution.(2)In order to make full use of the frequency characteristics of the detection element itself,an improved chirp compression method is proposed.According to the frequency characteristics of the loudspeaker and the characteristics of the acoustic wave detection signal,the parameters of the chirp pulse compression are optimized,the chirp window function is improved,and the signal-to-noise ratio and lateral resolution are further improved.(3)In order to overcome the influence of the side lobes on the detection accuracy after pulse compression,the minimum mean method is introduced to suppress the side lobes.And the least-average method is improved to achieve better sidelobe suppression effect.(4)An experimental system for sonic material level detection was constructed to verify the actual detection effect of the improved chirp compression method.A feature detection method for material level distribution is proposed.The regional position and height of the raised platform in the large plane can be calculated by the position detection difference between multiple acoustic wave detection units.Field tests show that the method can distinguish the regional position of the raised platform,and has good application value for the detection of the distribution characteristics of the material level surface.