| To solve the control problems on the characteristics of underactuation, systemic uncertainty of internal dynamic and external disturbances, control input saturation, motion constraint conditions, lateral drifting caused by the wind and current for conventional surface ships, the research of ship tracking control for underactuated surface is conducted based on Active Disturbance Rejection Control (ADRC) theory in this dissertation. The following main work and the achievement include:1. The study of nonlinear kinetic model of underactuated ship:A high precision maneuvering mathematic modeling of underactuated ship is designed by use of MMG(Manoeuvring Mathematical Model Group) model and experimental data from the literature; the ship motion characteristics was analyzed according to the above model; the simulation platform of ship motion with three degrees of freedom was built in the circumstance of Matlab Simulink.2. The study of slide mode ADRC algorithm:Tracking control problem was transformed into stabilization problem by use of differential ability of extended state observer (ESO), which simplified the structure of ADRC algorithm; The sliding mode ADRC approach is put forward, which means that error feedback in ADRC law was designed using the sliding mode iteration approach. The problem of constrained condition characteristic about control object is solved by using respectively linear slide mode and nonlinear slide mode with constrained conditions to design feedback control law, so the ADRC of improved structure made the parameters evident physical interpretation, easier and more intuitive to be tuned. The method of dealing with the problem of ADRC input saturation is proposed by use of monotone bounded hyperbolic tangent function.3. The study of ADRC design for ship path following:Firstly, taking advantage of the rejecting actively disturbance mode of ADRC, a sliding mode ADRC controller was designed according to the cross error of ship path ignoring reference course angle method which realized the ship tracking straight and curve path, and this method was applicable to the condition that is no more than90degrees of deviation between initial ship heading and planned course; Secondly, to design a nonlinear stabilization function combined path deviation with course deviation, the controller of path following is proposed based on the reference course, which applicable to the condition that is more than90degrees of deviation between initial ship heading and planned course; Thirdly, to solve the ship lateral drifting problem caused by the disturbances of wind and current, the following three separate ship tracking control methods is put forward:(1) Ship path following control based on Backstepping method;(2) Ship path following control based on CG (course made good) tracking;(3) Ship path following control by constructing desired reference ship heading angle. The above ADRC path following controllers were designed to realize tracking control of underactuated surface ship for straight line and/or curve path under the disturbance of wind and current.4. The study of ADRC design for ship trajectory tracking:Applying decentralized control theory combining with ADRC method to ship trajectory tracking control, the ADRC decentralized controller was designed for the multiple input and multiple output system of ship trajectory tracking, which idea was that the command rudder angle and rotating speed of propeller was regarded as control input, and path is controlled by rudder angle and speed is controlled by revolving speed of propeller, the coupling part was put into the total disturbance of system. The total disturbance was estimated at real time by ESO as per input and output of the system, and was compensated in control law.5. Extensive simulation experiments on the emulational platform constructed in chapter2were performed based on the training ship "Yulong" of Dalian Maritime University verified the effectiveness of the control methods proposed in this dissertation. |
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