Robust sliding mode tracking control of quadrotor integrated with observer and tracking differentiator

Abstract This paper presents a high‐frequency sliding mode control (HFSMC) approach that utilizes a nonlinear disturbance observer (NDO) and an improved tracking differentiator (TD) for achieving robust trajectory tracking control of a quadrotor unmanned aerial vehicle (UAV) in the presence of lumped disturbances and parameter uncertainties. Firstly, the quadrotor control system is decoupled into an inner‐loop subsystem focused on attitude adjustment and an outer‐loop subsystem dedicated to position control. The hierarchical control mechanism of the inner–outer loop solves the under‐actuation problem. Secondly, NDO is utilized to estimate and counteract lumped disturbances in real time, enhancing the system disturbance rejection capability. Additionally, a high‐frequency switching function is introduced into the reaching law to improve the reaching speed and handle parameter uncertainties, while the improved TD is used to smooth the desired attitude signals and their derivatives, reducing the chattering inherent in sliding mode control. This scheme effectively alleviates control input chattering while enhancing controller robustness, offering a simpler design and stronger disturbance rejection compared to nonsingular fast terminal sliding mode control (NFTSMC). Finally, the stability of the system is proven using globally uniformly ultimately bounded (GUUB) and Lyapunov theory. The effectiveness of the control strategy was validated through simulation experiments.