Research On The Velocity Measurement Technology And Software Design Of Vessel-mounted Acoustic Doppler Current Profiler

An Acoustic Doppler Current Profiler (ADCP) is a type of sonar that measures and records water current velocities over a range of depths, according to Doppler principle to realize large profile and multiple layer current measurement, which is now considered an essential tool for oceanography, estuary, river, and stream flow current measurement worldwide. Based on the ADCP equipment research and development background, this paper mainly studied the technology of Doppler velocity measurement and system software implementation.The thesis studied the coherent processing for echo signal, the pulse-pair algorithm was described in detail, on this base, for narrow-band signal using the digital tracking algorithm improved the conventional algorithm; for broadband coded signal, thesis studied a method which can solve velocity ambiguity, that is the correlated time delay estimation. Moreover,using cosine curve fitting to correct time delay estimation error under the condition of band-pass sampling. In addition, studied the development of secondary frequency measurement algorithm. In terms of calculating velocity, on the basis of standard Janus equations, derived the least-squares solution to remove the effect of system noise.On the other hand, determined the system's parameter design and software structure according to the actual work demands of ADCP system and the characteristics of the hardware platform. On three pieces of DSP hardware platform, completed the system's software development with the use of C language programming. Based on modular design thought, three pieces of DSP use a design mode of one master-two slaves. Among them, the master DSP mainly realize system state control management, the slave DSP is responsible for frequency measurement. In order to improve the executive efficiency of algorithm, the fast convolution filtering technology and fast calculation autocorrelation with FFT technology are adopted, which reduced the amount of calculation to a large extent.Finally, the ADCP system was tested, it is verified that the system can be stable ,accurate and high-precision to complete the task of multi-layer velocity profile, velocity measurement precision and layers both achieve index requirements, and at the last, paper presents the subsequent improvement methods.