Ship Motion Modeling And Filtering Technology Research On Trailing Suction Hopper Dredger

Ship Dynamic Positioning refers to the ship without the aid of anchoring system, couldcontinue to detect the ship’s deviation between actual position and target location, calculatethrust force and thrust moment by the controller to overcome outside interference orrestore to the target position, then make each propeller response correspondingly throughthe thrust distribution system, so that keep the ship in the target position or trajectory. Forthe trailing suction hopper dredger under construction in the ocean, the main aim ofdynamic positioning system is to achieve the control of the ship in surge, sway and yawfreedoms.The motion of the trailing suction hopper dredger in the ocean includes two aspects:low frequency motion and high frequency motion. The low frequency motion is the driftaroused by the wind, current, second-order wave force, drag force and propellers’interaction. The high frequency motion is the oscillation aroused by first-order wave force.The main factors affecting the accuracy of ship dynamic positioning origins from the highfrequency motion and the error of measurement system. In order to achieve accuracydynamic positioning, it’s necessary to filter these disturbances by the filtering, estimate theship’s real-time position including surge, sway and the angle of yaw.This paper derived from China Communications Construction Company Limited’s keyproject in2009, sets trailing suction hopper dredger as the object of study, establishes themathematical model of ship motion under dynamical positioning though mechanismmodeling method, including ship motion of low frequency and high frequency,measurement model, anti-thrust model of bow spray, propeller model, environmentdisturbance model and so on, gives the empirical formula to calculate the parameters in themodel such as fluid dynamic. Meanwhile, gray box modeling method which combinesmechanism modeling method and identification modeling method together is adopted,recursive least squares method is applied to identify the parameters in the mode, whichimproves modeling accuracy. The establishment model of ship motion provides support tothe design of controller and filtering in dynamic positioning system.In the filtering design, the ship motion characters of trailing suction hopper dredger isanalyzed, the ship under dynamic positioning is divided into two states: free navigationstatus and changing draught working status. In the free navigation status, Sage-Husa adaptive filtering algorithm is brought in; in the changing draught working status, improvedadaptive filtering algorithm which combined Sage-Husa adaptive filtering and strongtracking Kalman filter algorithm together is adopted, which solve the filtering problemsuccessfully.Some of the research production in this paper have been trialed in the ship andsucceed to a certain extent.