State observer-based adaptive fuzzy backstepping point stabilisation control of underactuated unmanned surface vehicles with input constraints

Abstract

In this study, the point stabilisation control of an underactuated unmanned surface vehicle (USV) is addressed considering input constraints, missing velocity measurement and external disturbance. Different from other methods, in this proposed control framework, the point stabilisation is transformed into a straight line path-following problem. Then a state observer-based adaptive fuzzy backstepping controller is designed. The missing velocity variables are estimated by an extended state observer (ESO). An adaptive fuzzy algorithm is used to approximate the unknown nonlinear items in the dynamics model of the vehicle, and auxiliary items are introduced to deal with the actuator saturations. The system stability is proved by using Lyapunov theory, and the effectiveness of the proposed approach is demonstrated by the simulation results.