Research And Realization Of Ship Course Autopilot Based On Auto Disturbance Rejection Controller

Ship autopilot is an important equipment for ship steering. It plays a vital role for the ship to navigate safely and economically. The dynamics model of ship has the characteristics such as large inertia, large time-lag and non-linearity. And the model perturbation should be considered because of the variety of the parameters, as well as the impact of wind, waves, oceanic flow and so on. It is very difficult to operate perfectly by the traditional method for control. In order to overcome difficulties in the automatic steering of ships, this study introduces a new nonlinear control method, auto-disturbance-rejection control technology (ADRC). This method does not rely on accurate mathematical model of the ship, both the internal dynamics and the external disturbances of controlled plant are treated as unknown disturbances that can be real-time estimated by the unique extended state observer (ESO). And nonlinear characteristics are reasonably quoted in the feedback to improve the robustness capacity of the system. Test results show that the ship course autopilot with auto-disturbance-rejection control has good steering ability, this study also proved that the autopilot is a stable and reliable product with perfect steering performance.In first, this paper introduces the principle of ship steering, equipments of the steering system and the three methods for ship steering in familiar. The responding nonlinear ship motion mathematical model is established based on the characteristics of ship course motion. The circumstance disturbance is analyzed. Based on the defects of traditional PID control methods, ADRC are introduced. Based on the basic principles and standard structure of ADRC, ship course autopilot is designed. In order to achieve in computer, the article gives the methods for discretization.Lots of shortage exist in the ship navigation instruments in using. It's necessary to develop a number of modern navigation instruments such as digital rudder angle transmitter, digital rudder angle displayer, repeater compass, which can be used in the system of ship autopilot. Functions and design principles are described briefly in this paper. The structure of the autopilot is given according to the functions it realizes. In response to the noise analysis from the environment, anti-jamming measures are takenin the design of hardware platform of the autopilot.In order to shorten the software design cycle and improve the stability and reliability of software system, real-time operating system (RTOS),μC/OS-Ⅱ, is embedded to the autopilot. The article describes the embedded system kernel structure, process of transplantation and the tasks of the system in detail. Finally, the design methods of software reliability and software anti-jamming measures are carried out in the paper.According to the methods in the paper, ship autopilot is developed successfully. Performance tests of the autopilot are carried out under laboratory conditions, parameters regulating experience is summed up and test results are analysed. The analysis showed that performance and the ability of anti-disturbance of the autopilot based on ADRC is very well. But improvement is also needed in future in order to get a better performance.