Fixed-Time Adaptive Sliding Mode Control Based on Super-Twisting Disturbance Observer for Uncertain Nonlinear Systems

This paper introduces a fixed-time control strategy for uncertain nonlinear systems. It proposes a fixed-time supertwisting disturbance observer (FSTDO) that can accurately estimate the disturbance affecting the system, ensuring fixed-time stability regardless of the initial conditions. The paper relaxes the assumptions about disturbance by treating their upper bounds for first-order derivatives as unknown. Utilizing the estimates from the FSTDO and incorporating auxiliary variables, we develop a fixed-time adaptive sliding mode control (FASMC) approach. The proposed control strategy is both continuous and nonsingular, guaranteeing that the error converges to zero within a fixed time. Finally, the effectiveness of the proposed method is validated through computational simulations.