Enhanced Fractional-Order Nonsingular Terminal Sliding Mode Control for Fully Submerged Hydrofoil Craft with Actuator Saturation

Abstract

This study introduces an enhanced adaptive fractional-order nonsingular terminal sliding mode controller (AFONTSMC) tailored for stabilizing a fully submerged hydrofoil craft (FSHC) under external disturbances, model uncertainties, and actuator saturation. A novel nonlinear disturbance observer modified by fractional-order calculus is proposed for flexible and less conservative estimation of lumped disturbances. An enhanced adaptive fractional-order nonsingular sliding mode scheme augmented by disturbance estimation is also introduced to improve disturbance rejection. This controller design only necessitates surpassing the estimation error rather than adhering strictly to the disturbance upper bound. Additionally, an adaptive fast-reaching law with a hyperbolic tangent function is incorporated to enhance the responsiveness and convergence rates of the controller, thereby reducing chattering. Furthermore, an auxiliary actuator compensator is developed to address saturation effects. The resultant closed system of the FSHC with the designed controller is globally asymptotically stable.

RIGHTS & PERMISSIONS

Harbin Engineering University and Springer-Verlag GmbH Germany, part of Springer Nature