IEEE Transactions on Automatic Control, Vol.65, No.7, 2814-2825, 2020
Continuous Twisting Algorithm for Third-Order Systems
In this paper, two control schemes producing a continuous control signal are presented for a perturbed triple integrator: The continuous twisting algorithm (3-CTA) and the output feedback continuous twisting algorithm (3-OFCTA). The first one is a state feedback controller that ensures global finite-time stability of the origin, despite of Lipschitz, nonvanishing, and matched disturbances. It provides steady-state precision of fourth order of the output w.r.t. sampling step. The second one is an output feedback controller, which uses a third-order robust and exact differentiator as an observer. By requiring only information of the measurable output, the 3-OFCTA preserves all features of robustness, convergence, and precision of the state feedback 3-CTA. Moreover, it is proven that a separation principle applies, so that the gains of the controller and of the observer can be selected independently to assure stability.
Keywords:State feedback;Convergence;Output feedback;Stability analysis;Observers;Lyapunov methods;Uncertainty;Finite-time convergence;higher-order sliding mode (HOSM) control;homogeneity;Lyapunov function (LF);robust control