Extreme Learning-Based Monocular Visual Servo of an Unmanned Surface Vessel

Abstract

In this article, suffering from unmatched visual-servo uncertainties and unknown dynamics/disturbances, an extreme learning-based monocular visual-servo (ELMVS) scheme is developed for maneuvering an unmanned surface vessel (USV) to reach the desired pose. By virtue of the backstepping philosophy, complex visual-servo unknowns are elaborately encapsulated into lumped nonlinearities, which are further accurately accommodated by devising a single-hidden layer feedforward network based adaptive compensating identifier (SACI). Within the SACI architecture, hidden nodes are completely model free and are randomly generated without tedious learning, and thereby dramatically expediting fast-dynamics identification. Moreover, by exploiting approximation residuals, direct hyperbolic-tangent links between input and output layers are deployed to enhance identification accuracy. Eventually, the Lyapunov synthesis guarantees that the proposed ELMVS scheme can asymptotically render visual-servo errors arbitrarily small while target features can be kept within the field of view. Remarkable performance and superiority is finally demonstrated on a prototype USV.