Finite-time velocity-observed based adaptive output-feedback trajectory tracking formation control for underactuated unmanned underwater vehicles with prescribed transient performance

Abstract

This paper presents a finite-time velocity-observed based adaptive output-feedback trajectory tracking formation control for underactuated unmanned underwater vehicles (UUVs) with prescribed transient performance. For realistic dynamical UUV model, we assume that the mass and damping matrices are off-diagonal and only partial information about hydrodynamics is known, and we simultaneously consider the problems of input saturation, unmeasured velocity, external disturbance, and prescribed performance to design formation controller. For this purpose, a leader-follower pattern is employed, where each follower tracks its reference trajectory defined by the leader position and predetermined formation without requirement of leader velocity. Moreover, a finite-time velocity observer is constructed by utilizing only position and attitude information in a short time for increasing the robustness, where the estimates are substituted for unmeasured velocities in output feedback. Then, to guarantee that all output-states do not violate prescribed transient performances, a proper error system is established by non-logarithmic error transformation function. Based on these designs, an output-feedback adaptive formation scheme is proposed, where neural networks are utilized for identifying lumped nonlinear terms composed of uncertain hydrodynamics and external disturbances, and auxiliary variables and their additional control terms are presented to handle input saturation and underactuated problems simultaneously. Using Lyapunov stability theorem, it is proved that all closed-loop signals are uniformly ultimately bounded (UUB), and tracking errors can be guaranteed within prescribed performance bounds. Simulation results demonstrate effectiveness of the proposed formation control scheme.