Track Keeping Control Of Ship Based Variable Structure Active Disturbance Rejection Control

Ship, as a means of delivery, have become of larger scale, higher automation, higher speed and higher efficiency, thus higher maneuverability is required for ships to be built hereafter. Common surface ships are under actuated while navigating in the sea. Due to speed, loading conditions, mechanical structure and disturbances from internal and external environment, ship control system would suffer from uncertainty, control input saturation, lateral drifting and instability. In order to solve above-mentioned problems on ship maneuverability, this paper studies ship track control based on variable structure active-disturbance rejection, detailed content includes:1. The study on the design for ship track keeping control:the thinking on design of the indirect track keeping control is adopted, through building dimension reduction equation(desired heading course function), desired heading course could be obtained which can make the error of ship track converging to zero, then ship track control can be realized by designing steering controller, which uses the desired heading course as an input to control heading course. Regardless of heading course control, according to the method of direct track keeping control, the error of ship track is directly controlled by the controller which is designed on the basis of ship’s position coordinate on geodetic coordinates, tracking problem would transform into stabilization problem by changes of state variables and control objective, so that tracking differential block of input signals can be leaved out, therefore the controller structure is simplified.2. The study on the algorithm of variable structure active-disturbance rejection control:new variable structure active-disturbance rejection controller is variable-structure designed through ESO(Extended State Observer) and state error feedback control rate within non-linear active-disturbance rejection controller. To simplify the controller further, only state error feedback control rate accepts variable structure design, ESO only accepts simple linear transformation processing, then LESO have only one adjustable parameter. the controller after variable structure design can control systems with uncertain controlled model, observe and compensate disturbances in real time, while the system enters into the sliding mode, it is no longer influenced by internal and external disturbances, meanwhile this design reduces the number of adjustable parameters of the system, improves the control performance. But with the introduction of sliding surface, the system would suffer chattering, so this paper introduces smooth relay function and improved exponential reaching law to cut chattering.3. Simulation experiments of ship track keeping control which relies on a nonlinear ship motion model built under Matlab Simulink environment based on training ship "Yu Long" of Dalian Maritime University to verify the effectiveness of designed control methods.