A Lyapunov based Saturated Super-Twisting Algorithm

Two different structures of saturated super-twisting algorithms are presented. Both structures switch from a relay controller to super-twisting algorithm through a switching law that is based on Lyapunov-level curves allowing the algorithms to generate bounded control signals. The relay controller provides a saturated control signal enforcing the system trajectories to reach a predefined neighborhood of the origin in which the super-twisting algorithm dynamics does not saturate, ensuring finite-time convergence to the origin. In order to increase the maximal admissible bound of the perturbations, the second algorithm also includes a perturbation estimator setting super-twisting’s integrator to the theoretically exact perturbation estimation. Experimental results are presented to validate the proposed algorithms.