Study On Ship Simulation Platform With Two Degrees Of Freedom

Ship occurs swaying motion during at sea, due to the influences of wind, current and wave. Swaying motion effects the ship’s propulsion power plant performance, increases the risk of ship navigation, weakens the accuracy of weapons on warship, etc. Therefore, swaying motion of the vessel becomes the focus of research on ship motion control, especially the roll and pitch, which has a profound significance in the military and civilian aspects. If sea trials are carried out with real ship to do research on swaying motion, it will have a high cost and a long cycle. The thesis designs ship simulation platform with two degrees of freedom on the background of school project "Integrated hydraulic propulsion of ship system", which lays foundation of the research on power plant propulsion and marine equipment performance impact and ship motion control in the storm.The platform is designed to simulate ship roll and pitch motion under certain sea states and sine wave motion with different amplitudes and periods. Firstly, the basic theory of waves, wave spectrum and Longuest-Higgins wave amplitude model is introduced. Then Conolly ship roll and pitch motion model is established through the analysis of force during ship swaying.Ship simulation platform is designed and analyzed summarily, including platform mechanical structure, principle of hydraulic system and selection of the main components of hydraulic system, etc. The platform’s control system is based on PID controller of PLC, therefore, it is necessary to analyze the design of control system electric circuit, selection of PLC and hardware design, and design of system PID controlling.To achieve roll and pitch motion of the platform, it is very important to design PLC control system programs. First of all, hardware configuration of platform PLC is made, then modular programming is adopted according to the platform’s function. And the design and content of the main control logic blocks are analyzed in detail.Finally, test research on ship simulation platform with two degrees of freedom is done, which is mainly from two aspects with simple sinusoidal motion and motion under actual sea states, and the actual and given movement curve of the platform are comparatively analyzed. The results show that the design and development of ship motion platform with two degrees of freedom is able to achieve the original design requirements, which has a certain practical significance.