Study Of Open Channel Flow Measurement Method Based On Underwater Acoustic Signal Processing

The topic of the paper is study of open channel flow measurement method based on underwater acoustic signal, its background was the prototype. Theory and technology issues of signal processing method and its implementation in embedded systems were researched. The paper’s content includes the following sections:1. Analysis of the flow measurements and the inaccuracy reasons of the former selected method.At first, a brief analysis of some of the flow measurement and introduced the chosen method and how to get the water flow by velocity and depth. Then from the theory to analyze main causes of inaccuracy. For example, speed formula, ultrasonic beam, water flow, temperature, frequency estimation, echo phase and so on.2、The researches of Doppler frequency estimation method.The water velocity is obtained through the Doppler shift, in order to get more accurate water speed, it is necessary to improve the accuracy of Doppler frequency estimation.First of all, to diminish the noise and interference (circuit thermal noise, crosstalk signal circuit noise, noise of water, etc.) that would cause Doppler estimation error. Processing on hardware to reduce interference, and then introduced the "improved spectral subtraction" method to reduce interference.Secondly, for the spectrum leakage caused by FFT and the peak migration by sampling , The discrete spectrum correction methods and analysis of all phase spectrum were introduced.3、The research of robust method of measuring the depth.The corresponding solution for the second echo; shallow water treatment; because of under-sampling, the phase of echo is uncertainty, the paper analyses the matched filter to find an adaptive matching; through the introduction of multiple correlation to improve the matching accuracy.4、The implementation of embedded system. The introduction of system’s hardware composition and the software realization. Details of the entire system, including signal transmission and reception, data acquisition, data processing and storage, communication with PC and program a simple interface to display the measurement data.5、Experimental verification and calibration of flow.The simulation studies of the above described theories to demonstrate the feasibility of the improved methods. The compare between the ultrasonic flowmeter and easy calibration system to achieve the "pre-calibration" purposes.