The Topology Prediction Model Of Ship Motion

The ship, especially aircraft carrier, called "the overlord of the sea" in naval warfare. Aircraft carrier is a large-scale surface ship , which adopts carrier-based aircrafts as major combat weapons, and it can not only protect the security of country , but also exert military pressure and operations instead of depending on the power of the local airport.Therefore, there is important practical significance in the research of prediction of ship motion.Influenced by sea waves and some other factors , the data of ship motion are characterized by being random and nonlinear time-varying , and Grey system theory has its unique feature in the study of nonlinear systems. In this paper, Topology prediction model of Grey system prediction is introduced into the ship motion prediction for the first time, and predicts the pitching angles of ship motion .This paper includes:1. Topology prediction is the data waveform prediction of system behavior characteristics during a period of time. Grey topology prediction model is not just a GM (1,1) model, but a GM (1,1) model group. In the group, a model has a threshold value, by which predicts the next one or more moments corresponding to each threshold value and predicts the overall trend. Consequently, it can simulate prediction with the original given data.2. Among the pitching angles of ship motion, there are two characteristics: there are more differences and frequent changes in the pitching angle data; the GM (1,1) model is limited to forecast the increase of monotonous series . Based on the above two ones, construct Grey topology prediction model for simulating prediction of the pitching angles, and the results show that Grey topology prediction model is obviously superior to GM (1,1) model.3. According to the numerical experiment analysis of several groups of different data, the results of the analysis show that the main element which may produce the larger error in prediction . The main factor is the unsuitable selection of threshold values or individual pitching angle being tiny. In addition, Topology prediction model for more data to forecast, the results are not necessarily good.Generally speaking, in error of 0.2 degree, the model can predict 3-11 seconds for the ship .For the various time intervals, average relative error is within 16%, the time of forecasting the trend of the ship motion will be a bit longer, which shows that Grey topology prediction in the motion of ship is reasonable and feasible.