Continuous Robust Control Based on Fixed-Time Super-Twisting Disturbance Observer

This article investigates fixed-time control methods for a class of uncertain nonlinear systems. A novel fixed-time super-twisting (FXST) disturbance observer has been designed to accurately estimate the imposed perturbations on the system in the sense of fixed-time stability without being affected by initial conditions. Then, based on the achieved estimation from the proposed FXST disturbance observer, a continuous fixed-time control (CFXC) scheme for a class of uncertain nonlinear systems has been designed. The control protocols and estimation rules are continuous without the discontinuity and chattering issue so that the errors can be converged to the origin within a predefined fixed time. Furthermore, by means of an improved estimation algorithm and proposed integral structure, some limitations on the controller and observer have been relaxed. Finally, the efficiency of the designed methods has been demonstrated via some simulation results.