Predict pitch and heave motion of ship via Inverse Triangle Transform MGM(1,n) model

The prediction of the ship motion has a significant practical meaning to the safety of the ship controlling. The pitch and heave motions are the main two features in the vertical movement system of the ship. Considering the coupling relationship between the influence factors in the ship motion system including the wave, the Inverse Triangle Transform MGM(1,n) model is proposed to predict the pitch and heave motion. The Range Transform is applied to normalize the different quantities of the model inputs. The modified Inverse Triangle Transform is introduced to solve the problem that the data are periodic oscillating. After these two transforms, the data fit the grey model well. The MGM(1,n) model is used to predict. In the analysis of the predicted result, within the relative error of 20%, the predicted data can get 70 groups, which is about 4-5 seconds. The right oscillating shape of the pitch and the heave motions last more than one period. The result shows that the model can predict the ship motion in required precision, and the model is effective and practicable.