Research On Multi-beam Acoustic Doppler Measurement Method

Acoustic Doppler Velocimetry Profiler(ADCP)uses the Doppler effect to measure the flow velocity of water.This technology is very mature,but there is still much room for improvement.The traditional ADCP equipment has a fixed beam direction and cannot change the transmitted beam direction according to the specific measurement requirements.In addition,carriers need to be used when the equipment is used.The equipment needs to complete the measurement in motion and the measurement is time consuming.Based on the research results of existing acoustic Doppler current measurement technology,this paper adopts multi-beam technology to improve the existing Doppler current measurement technology and proposes a multi-beam acoustic Doppler current measurement system design scheme.The system can measure the flow rate of the water body and realize the function of measuring the flow.At the same time,the shape of the wake of the ship can also be observed by calculating the echo scattering intensity.This article also simulates the key content of the design scheme,and verifies the key technologies in the system,laying the foundation for the subsequent research work.This article first summarizes the existing research of Doppler current measurement technology,multi-beam technology and wake characteristics,and the research status.The basic principles of Doppler current measurement technology and multi-beam technology are introduced.The shape and acoustic scattering characteristics of ship wakes are based on in-depth investigations.According to the actual application requirements,a method for measuring the fluid velocity using the multi-beam technique and the Doppler effect is proposed,and multi-beam measurement is given.This paper focuses on the design method of transmitting and receiving array based on multi-beam technology,the method of dividing the measured water space and the method of stratification of multi-beam measuring system.The entire water space is divided into a number of small areas,and the corresponding beam pointing direction of each small area is calculated.Using the method of changing the signal pulse width in different beam directions,the layering method of the traditional Doppler current measurement technology was improved.The radial flow velocity calculation method of multi-beam flow measurement system is given,and the calculation method of stratified scattering intensity of water body and the use of radial flow velocity to obtain the actual flow velocity and direction.In order to improve the design of the system,this paper also simulates the pointing characteristics of the system phased-fired array and the shape of the ship's Kelvin wake,and simulates and analyzes the error size and spatial distribution of multi-beam measurement.The hardware of the multi-beam current measurement system is composed of a multi-beam phased emission circuit,a multi-channel receiver circuit,and a DSP circuit.This paper focuses on the design of a multi-beam phased-control transmission circuit and produces a set of multi-beams.Phased emission circuit module,multi-beam phased emission control circuit consists of phased signal source,power amplifier driver stage circuit,power amplifier circuit and impedance matching transformer.Finally,the performance test of the multi-beam phased emission array in the system is described in this paper.The experimental results are analyzed and the key technology of multi-beam flow measurement system is verified.