Robust GDI with Extended Differentiator and Observer-Based Fast Terminal Integral Sliding Mode Control for UAV System

This study presents advanced robust control strategies for trajectory tracking of a Multiple Input–Multiple Output (MIMO) Unmanned Aerial Vehicle (UAV) system under disturbances and uncertainties. Motivated by the limitations of existing simulation-based studies, this work designs and experimentally validates nonlinear Lyapunov-based control strategies, including Integral Sliding Mode Control (ISMC), Fast Terminal ISMC (FTISMC), and a novel Robust Generalized Dynamic Inversion-based FTISMC (RGDIFTISMC). The proposed methods ensure fast, finite-time convergence and robustness under wind disturbances, incorporating a Uniform Robust Exact Differentiator (URED) and a nonlinear state feedback disturbance observer to accurately recover rotor speed and missing derivatives, while the observer enhances system observability. Experimental validation on a twin rotor system confirms superior performance, with RGDIFTISMC achieving up to 46.7% faster stabilization. The results highlight its efficiency in improving transient response, steady-state accuracy, and robustness against disturbances.