The Design Of Data Acquisition And Processing System For Wave Spectrum Buoy

Wave is a complex marine hydrological phenomenon,which has a direct impact on the safety of maritime transportation and coastal engineering.The observation of wave has practical significance.Among lots of wave observation instruments,the buoy can automatically measure for a long time,and has the advantages of free placement,low cost,and high accuracy.It is currently the most important wave measuring instrument.There are relatively mature domestic buoys,but they only output statistical eigenvalues,without the function of wave spectrum feature estimation.The wave directional spectrum can intuitively reflect the distribution of wave energy in the frequency domain and direction.It also can give the internal structure of the wave,in which the composition of wind wave and swells can be shown.At the same time,the wave spectral characteristics from nondirectional spectrum also have important significance.In this paper,a data acquisition and processing system for wave spectrum buoy is designed.The algorithm in the system can estimate the statistical characteristic,spectral characteristic,and Fourier coefficient of waves,which makes up for the blank of wave spectrum estimation for domestic buoys.At first,according to the requirements,the design scheme of data acquisition and processing system is proposed: the system uses the three-axis acceleration sensor,and the tilt and electronic compass sensor TCM2.5 to obtain the buoy acceleration and tilt information;the STM32F407 is used as the processor to collect and process data;to realize timing start,the PCF8583 is used.Then,it is concluded that the Fourier coefficients method is the best method to estimate wave spectrum on buoy by comparing the fast Fourier method,Fourier coefficients method,maximum likelihood method and Bayesian method.Finally,low-frequency filtering,direction correction,and vertical acceleration correction are discussed.An additional tilt angles are introduced in the vertical acceleration correction process to offset the influences of wind,current,tide and other factors on the vertical acceleration of the buoy platform.Finally,the wave spectrum buoy and DWR-Mk III wave buoy were compared in Wenzhou sea area.It is determined that the wave spectrum buoy's error may be caused by the low-frequency noise pollution of buoy and sensor through analysis.Besides,the noise pollution of the buoy's attitude to the vertical acceleration also introduce error.After that,by means of low-frequency noise spectrum estimation and buoy attitude correction technology,using the original data of the buoy for data correction,the spectral characteristic with small bias and the wave energy spectrum with high similarity are obtained.The algorithm used on wave spectrum buoy is determined.