Research On ADCP Bottom Tracking Technology And Implementation Of DSP

Acoustic Doppler current profiler(ADCP)is an instrument for measuring the velocity and volume of water using acoustic Doppler effect.The key point for ADCP to obtain flow information is the measurement of bottom tracking and velocity.This paper focuses on the bottom tracking technology in ADCP,and on the basis of analyzing a variety of ADCP bottom tracking techniques,the method of bottom depth measurement is improved and the bottom tracking method under the condition of high undulating bottom is studied.The main work is summarized as follows:1.Based on the bottom echo model under the element scattering theory,the influence of the bottom echo transition zone on the bottom velocity measurement is analyzed.The simulation experiment shows that the length of the bottom tracking detection signal must be longer than the length of the echo transition zone to obtain a better bottom velocity measurement result.2.In this paper,aiming at the problem of large error in the sounding of binary phase coded signal under the condition of element scattering,a combination of LFM signal and binary coded signal is proposed,which uses the advantages of the autocorrelation of the LFM signal to solve the problem that the position of the binary coded signal is difficult to distinguish after the pulse compression.A method of bottom depth determination based on energy center method and pulse compression method is proposed.First,the echo position is roughly judged by energy information,then the echo time delay is measured accurately by the correlation method.3.Aiming at the poor precision of the traditional ADCP bottom tracking technology in the high fluctuating bottom environment,the idea of multi beam bottom measurement is proposed in this paper,which transforms the problem of multi beam bottom tracking to the joint estimation of echo arrival angle and arrival time,the DFT beamforming and bearing direction indication method are used to distinguish the DOA and TOA of the bottom echo,which improve the resolution of bottom depth measurement.At the same time,the high resolution characteristic of multibeam bathymetry is used to plot the bottom of the water.4.On the basis of summarizing the process of ADCP bottom tracking signal processing,a bottom tracking software framework which separates the control and processing is put forward in this paper and the program running mode based on the software pipelining idea is realized and implemented in the ADCP hardware platform with the core of TMS320C6678.The actual alignment results with the ADCP calibration system show that the bottom tracking effect can accurately reflect the bottom water depth.