逐次型Bayes法による方向波スペクトルのオンライン推定

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The ship motions in waves are regarded as a nonstationary random process because of the ship maneuvers, such as changes of the course and the speed, even on the assumption that the seaway can be considered as stationary stochastic process. In this paper, the recursive type of Bayesian modeling procedure is proposed and applied to online estimation of directional wave spectra based on ship motion data, which are pitch angle, roll angle and vertical acceleration. In the proposed method, the convergence of the estimates is not achieved every time step, but gradually achieved with time steps by using the ship motion cross spectra. To cope with the nonstationarity included in the time history data, instantaneous cross spectrum analysis based on T-VVAR (Time Varying Coefficient Vector Auto Regressive) modeling procedure is adopted. The T-VVAR model is transformed into the state space model and the time varying coefficients can be evaluated by using the Kalman Filter algorithm. Using the estimated time varying coefficients, the instantaneous ship motion cross spectra can be calculated every moment. Moreover, in order to estimate the directional wave spectra stably, a new constraint condition, which is based on the observed significant wave height data, is introduced into the Bayesian modeling procedure. To examine the reliability of the proposed procedure, onboard tests were carried out on nonstationary conditions. It is shown that the statistical values derived by integration of the estimated directional wave spectra agree well with the observed one.
社団法人日本航海学会の論文
2003-03-25

逐次型Bayes法による方向波スペクトルのオンライン推定

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