Design Of Ship Course Controller

At the beginning of 1990's, backstepping was developed by Kokotovic and his copartners, it is a kind of circulative nonlinear design method that uses systematic way to construct feedback method and simultaneous correlative control Lyapunov function and so more and more scholars pay attention to it. Because it has very good flexibility, people can use "good" nonlinear item through introducing nonlinear damping to control "bad" nonlinear item. Now backstepping design method is one of the most effective methods to settle control problems in nonlinear system with uncertainty. The knowledge about Lyapunov stability and the theorem of backstepping design method are presented in this paper.In fact, the ship course control is a nonlinear problem with uncertainty, because the ship movement has the great inertia hysteretic characteristics, in addition it is disturbed by environment, so it is more important to apply some more effective control algorithm to the ship motion control field. In this article, the nonlinear ship movement mathematical model with uncertainty, the basic knowledge and the control principle of ship course control are introduced.Integral control has the use of canceling bias and improving the performance of the controller, it paves the way for what later is known as the PID controller. More recently, nonlinear control designs with integral action included have been used for ship control.A ship course controller is designed for Norrbin nonlinear ship mathematical model with matching uncertainty. Combining the backstepping algorithm with the nonlinear damping algorithm to design controller, the nonlinear damping is used to cancel the uncertainty. The integral item is introduced in the design to improve the performance of the controller. Now, general ships can only use the electric gyrocompass to measure the course angle, but they have no equipments to measure the angular velocity, so in this article another ship course controller of output feedback is designed for Norrbin nonlinear ship, firstly the angular velocity is estimated by the observer and then the ship course controller is designed.The results of simulation demonstrate the feasibility and effectiveness of the two designed controllers.