Simulation Research On Ship Course Nonlinear System Based On Auto Disturbance Rejection Controller

The design of ship course controller is one of the most important research topics of ship motion control, which is closely related to ship's economic, security and comfort. Because of the high inertia, strong time lag, non-linearity characteristics, the model parameter perturbations, as well as the effects of wind, wave and current disturbances, designing a high performance ship course controller is always a very complex issue.The auto disturbance rejection controller(ADRC) is a novel nonlinear control frame proposed by Prof.Han and his research group. Within this frame, both the internal dynamics and the external disturbances of controlled plant are treated as unknown disturbances that can be estimated by the unique extended state observer(ESO). This control method is proved to be very effective because it does not overly depend on mathematical model of the plant and it can compensate for the internal and external disturbances dynamically. Now, ADRC has been successfully applied in various areas such as electric machine control, robot control, flight control. This paper adopts ADRC to the ship course control and simulation studies are done .Firstly, the defects of traditional PID control methods are discussed, tracking differential(TD), extended state observer(ESO), nonlinear state error feedback (NLSEF) and the basic principle of ADRC are introduced, and then the standard structure of ADRC is given.The basic theories of ship steering and ship course motion are studied. The responding nonlinear ship motion mathematical model with rudder restrictions is established. The circumstance disturbance is analyzed and disturbances mathematical models of wind, wave and current are established.The study of ship course control based on ADRC is the focus: ship course motion system is considered as a series system consisted of rudder model and ship motion model, and the structure of this system is given; two design proposals are analyzed and two-order ADRC is used to control the ship course motion system; s functions are edited to achieve ADRC algorithm; the ship course motion simulation platform based on ADRC is created; some methods of controller's parameter setting are generalized.The simulation studies of ship course control based on ADRC are done. Simulation results show that, compared with the PID controller of which parameters are optimized, the ship course control system based on ADRC has a better performance in wide-angle course switch, course keeping, outside disturbances, parameter perturbations and so on, it has powerful robustness and anti-disturbances capability.Finally, the ADRC controller is improved for its slow response to the small-angle course; conclusions are given with recommendation for future work.We hope through the study of the ADRC controller in ship course control to expand the applications of the ADRC and to provide a new thinking to ship course control strategy.