Research On DOA Estimation Method Of Ultrasonic Array For Dynamic Liquid Level Measurement

Sufficient solution in battery is very important for its power supply,service life and safety performance.As a short-distance measurement,liquid level fluctuation will produce a large measurement error.In order to prevent the use of battery from being affected by the low liquid level,this thesis aims at the problem of liquid level fluctuation of Marine lead-acid battery,and uses the method of DOA estimation and time of flight estimation of ultrasonic array to conduct an in-depth study on the problem of liquid level fluctuation.Firstly,based on the principle of multi-aperture and the approximate principle of phase center,the ultrasonic array is optimized by uniform arrangement,and the structure of multi-input and multi-output planar array is formed.Aiming at the nonuniform noise generated inside lead-acid battery and the interference of reflection correlation wave in signal echo,the improved matrix reconstruction algorithm and oblique projection operator are used to disassociate the correlation source group,and the DOA estimation of correlation signal and non-correlation signal under nonstationary noise is realized.Secondly,aiming at the problem of flight time of signal in the process of transmission,according to modified Gauss Newton method,the transmission time of single signal and multiple overlapping signals can be estimated by using the envelope of echo signal.At the same time,the wavelet denoising technique and Hilbert transform are applied to it,which can eliminate the noise interference and improve the estimation accuracy.Finally,the proposed method is verified by simulating the curve model of the fluctuating liquid surface,and the liquid level information obtained by DOA and TOF estimation algorithms is analyzed jointly.The results show that,compared with ultrasonic phased array technique,the experimental measurement error of the proposed method is controlled within 1.5mm and the accuracy of the liquid level estimation is up to 0.4%,which is a great improvement in the measurement accuracy and can still maintain a higher measurement accuracy under complex environmental conditions.