Control Of Ship Fin Stabilizer In The Presence Of Input Saturation

Large amplitude rolling affects the safety, seaworthiness, comfort of ship and the ferocity of warship seriously. How to reduce rolling quickly and more accurately is a significant object in the ship motion control literature.At present, most of the fin stabilizer systems still adopt the PID controller. However, the conventional PID control effect could not meet the demand of users because of the rolling motion’s nonlinearity, complexity and nonlinear disturbance. Therefore, the effective measure to solve the problem is to adopt advanced control strategies.The uncertainties may lead to the instability of system and may decrease the control performance of system, but one of the effective ways to tackle this problem is to improve the robustness of controller. In this paper, three robust control schemes are discussed for the uncertain nonlinear fin stabilizer system. First, a parameter adaptive backstepping control algorithm is discussed for the fin stabilizer system with unknown parameters. This algorithm improves the robustness of the conventional backstepping method. Second, the adaptive backstepping and neural network technique are employed for the uncertain fin stabilizer system with input saturation in this paper, thus this essay proposes a direct adaptive neural network scheme. This algorithm improves the robustness of the controller without depending on the model. Last, an adaptive. DOB control scheme is proposed for the system with unknown parameters, unmodeled dynamics, unknown random disturbance and input saturation. This kind of algorithm solves the problem that system containing unknown parameters could not build disturbance observer directly. It reduces the reliance on model of the system, and further improves the robustness of the system.The robustness of the three algorithms is increasing in turn in this paper. Stability of the closed-loop system is guaranteed in all of the three algorithms and is further improved by considering the input saturation in latter two programs. Finally, MATLAB for simulation shows the effectiveness of the investigated algorithms.