Study Of Ship Heading Control Based On Fuzzy Sliding Mode Variable Structure Control

The design of ship course controller is one of the most important research topics of ship motion control, which is not only related to ship's security and economic, but also is a basic foundation of some problem, such as trajectory tracking, dynamic positioning and automatic avoidance collision, etc. Because of the high inertia, strong time lag, non-linearity characteristics, model parameter perturbations which is caused by ship speed and load changes; wind, wave and current disturbances also can make uncertainty of ship dynamic in Navigation, therefore, the study of strong robustness ship course controller is very significan- ce.Both fuzzy control and sliding mode variable structure control have strong robustness, they combining with each other can achieve advantages complementary. Based on this, fuzzy sliding mode variable structure control is used in ship course control in this thesis, and simulation studies are done.The main works include:1. Summarize theory of ship maneuvering and course control characteristics, the analysis is focused on third-order Abkowitz non-linear maneuvering mathematical model of ship, and its simulation module is build under simulink. Taking into account wind, waves and currents and other interference factors and gives the interference model, which lay a good foundation for the controller design and simulation of course.2. Studying the basic principle of sliding mode variable structure control, Combination of ship course control model, course sliding mode variable structure controller based on the equivalent control is designed, and simulation studies are done. In view of the chattering problem of sliding mode control, first, the causes of sliding mode control is analyzed in detail, second, saturation function for chattering reduction of sliding mode control is gave, and simulation comparison is also conducted.3. According to conventional sliding mode control for chattering and robustness issues, introducing fuzzy control technology, real-time adjustment sliding mode switching control sign function value to weaken the amplitude of chattering, combined with the characteristics of course control, a new type of combined course controller is designed, that is sliding mode controller for course changing and fuzzy sliding mode controller for course keeping, respectively to meet the speed and steady-state accuracy requirements of course control. Look-up table of fuzzy control and improving of the steady-state error problem has been done. Simulation results proved, the controller designed in this paper gives not merely a better solution to the problems of conventional sliding mode control, and also shows better performance than PID controller of which parameters are optimized in dynamic properties, anti-interference and robustness.4. Analyzing wave interference theory and its adverse effects on the course control, the basic principles and design methods of Extended State Observer are expounded. Also, wave interference filter based on extended state observer is designed. Through different sea simulation conditions, the results show that, in this paper, high frequency noise waves can be filtered preferably by filter, the phenomenon of frequently steering can be avoid successfully, the quality of a ship course control also be enhanced further.