Research On Auto Area Control Of Dynamic Positioning Vessel

With the increasing demand for marine resources development,dynamic positioning systems have received more and more attention.The control technology is most important part of the dynamic positioning system,and its performance directly affects the accuracy,the stability,the maneuverability as well as the energy consumption of the ship or the platform.With the development of the times,people have increased awareness of energy-saving and environmental protection,and green control has also been paid more and more attention.This paper mainly focuses on the energy consumption problem of the dynamic positioning system,and an auto area controller based on the optimal consumption is designed,combining two green control concepts weather optimal heading control and auto area control.The entire auto area control process involves two steps: The vessel firstly moves from a farther initial point to the center point of the security zone and then uses auto area control in the working zone to achieve the goals of energy saving and environmental protection.Along with these two steps,a complete auto area controller is designed and the main work of this thesis includes:(1)For the step that ships move from a farther initial point to the center point of the security zone,the traditional Proportion-Integral-Derivative(PID)control has the problem that the control output will quickly be saturated and the control parameters are difficult to adjust.Three different reference trajectories PID controllers are designed in this thesis,and simulations and experiments are conducted to verify their effectiveness by comparing their effects with each other.(2)For the auto area control need to predict the future state of the vessel,augmented state-space model is established for the design of the model predictive control(MPC).A nonlinear passive observer is designed to observe and estimate current environment forces,and the constraints of the maximum forces and the change-rate of the forces are taken into account to ensure the success of the thrusts allocation.Besides,the quadratic programming method is introduced to solve the optimal control output.The advantages of the MPC over the PID controller are validated by simulation;the observation capability and the ability to estimate environmental forces of the passive observer as well as the feasibility of the model predictive controller in slowly-varying environment forces are all tested through simulations.(3)For the energy consumption problem,based on the concept of Green DP,an auto area controller is designed to obtain environmental optimal combining weather optimal heading control and auto area control concepts.The whole area is divided into three parts: security zone,environmental optimal compensation zone and model predictive control zone.The station keeping and auto area control simulations are conducted in conditions that the environment forces change gradually or suddenly.Four groups of simulations prove that the auto area controller can ensure the safety of ships' working conditions under different environment forces.Meanwhile,the auto area controller also has the advantages of energy-saving and emission-reduction.