Adaptive Fuzzy Design For Ship Autopilot

In the last decades, it is a hot research topic to develop a robust adaptive autopilot with significant nonlinear factors and uncertainties existing in ship course control system model due to the changing of the ship speed, loading state and external environment interference.There are three kinds of uncertain nonlinear ship course control systems. The systems contain unknown parameters, unknown nonlinear functions or unknown control gains coefficients. Aiming at these three cases, three nonlinear ship course autopilot algorithms are respectively presented.Firstly, based on the backstepping method, an adaptive ship course controller is put up with for ship heading system with uncertain parameters but without considering steering servo system; Secondly, an advanced algorithm is put forward for the ship course control system considering the steering servo system and unknown external interference. The nonlinear smooth uncertain functions can be approximated by fuzzy logic system. The "explosion of complexity" problem is avoided by the introduction of dynamic surface control technology (DSC technology) and the controller design for this three-order system is significantly simplified. The input saturation is also taken into consideration. Finally, for the ship course control system with unknown control gain coefficients, the proposed adaptive heading control algorithm, which introduces Nussbaum gain technology into the backstepping method, does not require a priori knowledge for the signs of the unknown virtual control coefficients. This algorithm can achieve good tracking performance.The proposed course control algorithms can guarantee that all the signals of the closed-loop system are uniformly and ultimately bounded (UUB), and the heading tracking error is small enough. Finally, the MATLAB computer simulation results validate the effectiveness of controllers.