Research On Prediction Method Of Ship Pitch, Roll And Heave Motion

In complex sea conditions, Surface ships will be produced a variety of rock and sway motion, in which the impact and harm of the pitch, roll and heave is greatest. Intense pitch, roll and heave will not only seriously affect the comfort and safety of the crew, but also make the speed of ship down, let the power of host engine lower and damage the ship's stability, , and may even lead to capsize, resulting in serious consequences. Therefore, effective and accurate prediction of ship motion attitude has become an important issue, it is of great significance to enhance the ship's sea keeping qualities and seaworthiness, to make compensate control for rock and sway motion in advance. In this paper, based on the above issue, bring forward the study of prediction method on ship pitch, roll and heave motion.First of all, based on strip theory, established a large surface ship's six-degrees equations of motion, which could provide a precise mathematical model for the simulation study of ship rock and sway motion. Random wave is the main reason of rock and sway motion, so establish the ideal model of random waves is the basic conditions for research on the motion of ship. Based the theory of ChangFeng random waves, we simulated and calculated the wave disturbance force and disturbance torque.In this paper, two prediction methods of the ship pitch, roll and heave movement were adopted. One based on Kalman filtering method, which included system modeling, shaping filter design, system expansion and so on. The other was time series forecast. Through statistical analysis of ship motion attitude, carry out prediction using the AR (Auto Regressive Model) time series model. RLS algorithm was adopted to estimate the parameters of AR model. Classical AIC criterion was applied for model-order determination. Using the above two methods, gave out the simulation results of the large surface vessels short-term forecast of the pitch, roll and heave motion. By analyzing the results, validate the method is accurate, effective and of highly practical value.All these research work were achieved in the VC + +. net and Matlab6.1 simulation platform. Theoretical analysis and a large number of simulation results proved that regarding the ship motion prediction of pitch, roll and heave motion, Kalman estimation and time series analysis could both obtain satisfactory results. Time series analysis method is simple and quick, while the Kalman estimation method aiming at specific system gained the better prediction effects. Although the conditions of use are more, the forecast accuracy is high, and with wide application prospects. In this paper, research results and conclusions have important guiding significance on short-term real-time prediction of ship pitch, roll and heave motion.