Research On Dynamic Positioning Switch Control Based On Estimation Of Wave Spectra

With the development of mineral resources,land increasingly exhausted,people set their sights on the area accounted for 70 percent of the Earth's vast oceans,and thus,the development and utilization of marine resources around the world are keen to become contemporary research.Because of offshore petroleum resources development of deep-sea mining,but the traditional way is not only restricted anchor position working depth and location of the job,and its costs are more expensive,thus contributing to the emergence and development of dynamic positioning technology.Dynamic positioning controller is assigned by the ship's own propeller thrust leaving the ship reached automatically maintain position or heading,overcoming the shortcomings of traditional mooring location.And ships at sea,by the sea,the wind and ocean current external environment,where the waves are most important and influential factors,and thus obtain real-time information is essential for dynamic positioning wave control system.Because dynamic positioning vessels operating around the clock needs to adapt to the continuous changes in the marine environment,which requires dynamic positioning control system has a strong adaptive ability,and traditional control systems compared to a single controller switching controller is a controller group control system form,in the case of environmental changes,according to the switching instruction provided by estimator,the type of controller by switching control to meet the needs of their adaptable.In this paper,basing on the linear relationship between waves and the ship motion response of,calculated wave directional spectrum according to the ship motion response data,obtaining real-time information waves.The estimated real-time wave information as a estimator was introduced into the dynamic positioning of switch control system.The concrete research content is as follows:First,the mathematical model of ship motion in six degrees of freedom is established,including kinematic mathematical model and dynamic mathematical model.And use MATAB to simulate the ship motion so that the ship mathematical model is verified.And the simulation of a certain type of ship motion of roll,pitch and heave 3-dof response operator functions were carried out,and analysis the simulation result from a different part.Second,the response to three degrees of freedom of ship motion data of cross spectrum analysis is done again according to the modern spectral estimation method: multivariate autoregressive model method,getting the cross spectrum of roll,pitch and heave.Comparingwith the traditional spectrum estimation method,obvious advantages of multivariate autoregressive model method includes: first,it can avoid the phenomenon of spectral leakage of traditional spectrum analysis method,and estimation of power spectrum can be done over the continuous frequency,the second is the estimate of the power spectrum with less variance.Third,basing on the response operator function of ship motion and the calculated cross spectrum,according to the linear relationship between ship motion response and wave and considering the problems of three value function,the Bayesian theory is introduced into the direction of wave spectrum estimation.First,the related knowledge of Bayesian statistics theory is introduced,the Bayesian model of wave spectrum estimation was established.In the model,three kinds of data distribution were introduced respectively:(1)the data distribution:cross spectrum distribution of data.(2)The prior distribution: the introduction of the first prior distribution is because the direction of wave spectrum function should be a smooth,continuous function.In order to avoid the estimation problem at the edge of frequency,the second prior distribution was introduced.According to the AKaike Bayesian information criteria and QR decomposition method,the optimal value of each discrete point direction of wave spectrum was obtained.Finally,used the proposed method to estimate four kinds sea state respectively,and analyzed the result of the estimation,the effectiveness and accuracy of the proposed method were verified.Finally,the estimated real-time information sea conditions as estimator was introduced into the switch control system,on the premise of sea state of continuous change,the position control of ship dynamic positioning were simulated.And with the traditional single controller results were compared,thus practical significance for the wave directional spectrum estimation has been exemplary instructions.