Research On State Feedback H? Switched Control Of Dynamic Positioning Vessel

With the rapid development of industrialization, the land mineral resources increasingly exhausted, people begin to set sights on the area accounted for 70 percent of the Earth's vast oceans, and thus, the marine operations from offshore extend to the deep, and marine vessels are required to ocean environment variationally (from calm to extreme seas), so it is important to study the control problems of ship for the external environment exchanged. Uncertainty disturbances widely exists in ship motion, as the H? switch control has advantages to solve the uncertainty and nonlinear problems, this paper proposes a state feedback switching adaptive control strategy for dynamic positioning vessels which conduct all-year marine operation. In case with the exchanged marine environment, according to the switching instructions provided by the switching rules, select a controller from the subsystems to meet the needs, improve the capability of DP controller to accept the varying marine environment greatly.In this paper, basing on the dynamic positioning vessels, a robust H? switched controller is designed for the dynamic positioning control system, using Lyapunov function to prove the asymptotic stability of the controller, according to the H? stability theory, by solving the correspond linear matrix inequality(LMI), deduced to matrix gain of the switched controller, researched the setpoint control of dynamic positioning vessels in varying sea conditions. The concrete research content is as follows:First, A 6 degree-of-freedom(DOF) ship model composed by kinematic and dynamic aspects is established. The environmental disturbances model induced by waves, wind and current is also established. Simulation about ship motion under a sea conditions is carried on to verify the correctness of the mathematical models in MATLAB.Second, a robust controller of dynamic positioning system is designed. The robust controller has advantages of resisting the disturbance and uncertainty, and therefore, the dynamic positioning vessel robust controller under a certain sea conditions is designed. It is proved that the designed robust controller have superior performance compared to the troditional controller in terms of resistance to disturbance .Third, state feedback switched control method is designed for dynamic positioning system in different sea conditions. The changing wave height can be dealt as a class of subsystems. Corresponded controller under each sea condition is designed for each subsystem,corresponded subsystem is selected to meet the overall control performance based on the relevant switched rules in varing sea conditions. Uncertainty is added to the established model as it widely exists in actual ships. Then a state feedback controller and the corresponding switched rules are designed based on the switching subsystems with uncertainty. Simulation results illustrates the designed switched control system can ensure the dynamic positioning system switched stable under the varying sea conditions.The research and result indicates that the H? swithing control method proposed in this paper effectively ensures stability of swithing of the positioning ship under multi-sea condition. This conclusion has a certain practical value for the safety of ships in maritime operation.