Inquiring of Methods to Establish Control Model of Warship

摘要

When a ship sails on sea, it is necessarily disturbed by wave, sea wind and ocean current, which result in vibration inevitably, which is called, by shipbuilding industry, roll, pitch, yaw, sway, march and heave. Fierce vibration may do a series of harm to ships, even have serious consequences. Therefore, we must reduce vibration in order to guarantee safe sailing of ships and advance working ability of the crew. For general ship, we mainly reduce longitudinal movement. In this paper, hydrodynamic model of longitudinal movement under different wave directions and ship speed is established according to section theory and the Second Law of Newton on the basis that the main dimension and profile map of ship are given. Because the coefficients of hydrodynamic model are not just relevant to ship speed, they mainly depend on encountering frequency, the model is linear differential set of equations iwth frequency relevant coefficients, which brings great trouble to the design of controller. Therefore, by making use of levy method, improved levy method and least squares fit of differential equations, hydrodynamic model is converted into a control model which changes only with speed and heading and have no relation with frequency. Also, this paper emphatically introduce the concrete algorithm to establish the ship control model by making use of least squares fit of differential equations, this model can be represented by constant coefficient differential set of equations. If or not shipcontrol model can well reflect char voyage work and perform military tasks on the randoms established by the above methods is reasonable. This paper discusses several methods to control hydrodynamic model into a control model which only change with heading and speed and have no relation with frequency. By making use of least-square fit of differential equation, the shipping control model is acquired, and the gain phase characteristic, the controllability and observability and the stability are proven. Simulation results indicate that this control model is reasonable.