Research on simulation of course control for large ship with wave disturbances in different sea conditions

When a large ship sails on the sea, it must meet the random wave disturbances and produce complicated movement form. It is very important to consider the random wave disturbance force and moment in the ship manoeuvring simulation and ship control system design. So it is really important to research on wave signal and figure out the disturbance force and moment of ocean wave acting on ship. The wave is a very complex random process, and the shape of ship is also very complicated, therefore it is a more complicated problem to compute the wave disturbance force and moment acting on ship. It mainly solves the difficult problem of numerical simulation of wave disturbances in ship motion control and simulation area. The wave disturbance force and moment acting on the ship sailing on the sea are simulated. The influence of ocean wave to the four freedom degree movement of large ship is also researched and analyzed under different sea conditions. Based on statistical superposition theory, Pierson-Moskowitz (P-M) single-parameter standard wave spectrum is used to simulate a random long-crested sea wave. A kind of wave disturbance mathematical model is established and then the random wave disturbance force and moment effecting on the large ship is calculated and simulated real time under different sea conditions. A ship autopilot is used to control the ship course and the ship motion trajectory under different wave encounter angles at different sea conditions are attained by simulation. The calculated wave disturbances are quite significant in four freedom degrees of the large ship. Thus, the ship course must be controlled. A ship autopilot is used to control the large ship to keep or change the ship course. Finally, the ship control simulation with different wave disturbances is successfully realized. The simulation experiment results show that the random wave disturbances have big influences on the large ship at sea and the wave influences are different in different sea con- ditions or different wave encounter angles, which result in different ship control effects. The established wave disturbance model and the wave disturbance simulation results have a good importance on the ship control system research.