Adaptive fuzzy controller design for dynamic positioning ship integrating prescribed performance

Abstract

This paper investigates the trajectory tracking control problem of dynamic positioning ship subject to modeling uncertainties, environment disturbances, and unmeasurable velocity. A novel adaptive fuzzy controller is designed to address this challenging problem, by incorporating the prescribed performance control technique and adaptive fuzzy backstepping control method. Specifically, a high-gain observer is constructed to estimate the unmeasurable velocity vector. Then, a special finite-time performance function is introduced to impose performance specifications in advance on the output tracking errors according to the mission requirements (in terms of mission completion time, maximum permitted overshoot, tracking accuracy). Subsequently, through introducing error transformation functions, the tracking control problem with guaranteed transient performance is transformed to the output constrained control problem. In view of this, an asymmetric barrier Lyapunov function is designed to ensure that the transformed errors remain within specified ranges. By virtue of Lyapunov theory, it is shown that all the closed-loop signals are uniformly ultimately bounded and the tracking errors strictly comply with the prescribed performance envelops, despite the presence of modeling uncertainties, environmental disturbances and unmeasurable velocity. Finally, numerical simulations are presented to illustrate the effectiveness of the proposed method.