Adaptive Quasi-Fixed-Time Integral Terminal Sliding Mode Control for Nonlinear Systems

This brief proposes an adaptive quasi-fixed-time integral terminal sliding mode control, in order to solve the stabilization problem for a class of invertible nonlinear systems with unknown varying perturbations. The proposed method can drive the sliding manifold into a predefined vicinity of equilibrium and estimate the bound of the state-dependent perturbation in quasi-fixed-time despite the large initial state errors. Besides, the state variable also converges in quasi-fixed-time due to the geometric homogeneous property of the designed sliding manifold. Furthermore, a novel nonsingular adaptive layer function is proposed and the respective control is completely chattering-free, Lipschitz continuous and no gain overestimation exists, which is critical to practical applications under measurement noises. Finally, the superiority of the method is validated through simulation and a permanent magnet synchronous motor control experiment.