The Research On Velocity Measurment Using Acoustic Correlation

For surface vessels or autonomous underwater vehicles (AUV), navigation system is necessary. Acoustic correlation log (ACL) is a navigation instrument, which is suitable to be equipped on ships, AUVs and submarines, and so on. It can make measurements of velocity relative to the seabed, supply the carrier's moving information and get accurate cumulative sail. Make further efforts on Acoustic Correlation Log research are valuable.In this thesis, the basic principle of ACL --waveform invariance principle and its applying area, is presented in detail. The correlation properties of seafloor reverberation signals between different hydrophones on receiving arrays are discussed which is determined by the oceanic depth and launching angle. Some problems, such as the choice of frequency and distance between transducers, are discussed according to sonar equation, which should be considered in the design of Acoustic Correlation Log.With sufficient advisement based on sonar equation, the seabed echo simulation model for acoustic correlation log is founded by gridding method, in which the result is basically consistent with the simulation. The model is basis to further discuss for the velocity measurement of ACL.Then, the theoretical analysis and emulation study is taken on the spatial correlation according to the model, discussing the taper surface fitting, Lagrange interpolation, cubic spline interpolation fit to the spatial correlation function or interpolation effect, the statistical velocity measurement result of beeline array and plane array have come out, the precision of velocity measurement is preferable.The theoretical analysis and emulation study is taken on the temporal and the spatial correlation according to the model, the theory of the temporal-spatial correlation is deduced in details, and data the correlation matrix is set up. Using the maximum likelihood estimation method to estimate the unknown velocity parameters. Nelder-Mead Method is introduced in the paper to find the likelihood function minimization. Due to the possibility to get into local optimum with Nelder-Mead Method, the improved method is put forward with the bonded...