Novel Fixed-Time Nonsingular Fast Terminal Sliding Mode Control for Second-Order Uncertain Systems Based on Adaptive Disturbance Observer

In this paper, a novel fixed-time nonsingular fast terminal sliding mode control incorporating with an adaptive disturbance observer is proposed for second-order uncertain nonlinear systems to achieve fast stabilization and robust control. Based on the theory of fixed-time convergence, a novel fixed-time stable system is first investigated. Using this system, a novel fixed-time nonsingular fast terminal sliding mode controller is developed, which can achieve system stabilization within bounded convergence time regardless of initial states and provide nonsingularity and fast convergence. Moreover, an adaptive disturbance observer is designed to improve the control performance and compensate for uncertain disturbances. The fixed-time stability of the sliding surface and the system states under the proposed composite control scheme are demonstrated by the Lyapunov stability theory. Both theoretical analysis and simulation results are presented to verify the feasibility and superiority of the proposed method.