Design And Implementation Of Ultrasonic Doppler Flow Meter

Ultrasonic Doppler flow meter is a popular device for measuring the velocity of flow.Based on the Doppler Effect of ultrasonic wave in flowing water,it can obtain the velocity information of water through a series of signal processing.It has the advantages of fast flow measurement response,no interference to the flow field,and convenient installation.It is widely used in marine exploration and ship navigation nowadays.This thesis aimed at small application scenarios such as inland rivers,ditches and pipelines,and designed and implemented an ultrasonic Doppler flow measurement system based on FPGA.It has broad application prospects in urban pipeline construction,river transportation,agricultural irrigation,and flood and drought resistance.The main research work of this thesis is on the design and implementation of the flow measurement system.(1)This thesis introduces the basic principles of ultrasonic Doppler flow measurement firstly.And then the thesis designs the system structure according to the principles and application scenarios,and defines system workflow,and designs key system parameters.After that the thesis also analyzes the impact of different parameters on the measurement performance.At last,the system signal processing flow is simulated to verify the feasibility of the system solution.(2)Focusing on the flow measurement system,this thesis discusses key technologies and signal processing algorithm of this system,which includes software radio technology and signal frequency estimation algorithm.The performance of the autocorrelation method and fast Fourier transform method in the low SNR environment are compared through simulation.Aiming at the limitation of the fast Fourier transform in the flow measurement system,the idea of short-time Fourier transform method is used in the flow measurement system.(3)According to the design ideas,system structure and technical solutions of the flow measurement system,this thesis selects the appropriate hardware module,and builds the complete hardware platform based on FPGA.And then the thesis uses Verilog language to design and implement the signal processing algorithm of the flow measurement system and the interface control program of each hardware module.After that the thesis proposes a flow measurement scheme,and completes system test.At last,this thesis analyzes the reasons of the error caused by external factors such as deflection Angle of transducer installation,ultrasonic propagation speed and ultrasonic beam width.