Robust Global Output Feedback Stabilization With Sliding Mode Control: A Separation Principle Approach

The main purpose of this letter is to design an output feedback sliding mode controller for globally stabilizing the origin of the closed-loop plant via the separation principle. Here, the output feedback control law consists of a robust sliding mode observer whose states are used in the state-feedback law when the actual states are not measurable; this is inspired by the certainty equivalence principle. It is revealed in the literature that in the existing output feedback sliding mode controller, the controller gain is dependent on the (sliding mode) observer gain, violating the separation of controller and observer structures. This leads to many issues in the system, such as high amplitude chattering and large control signals because of the higher control switching gain. Our proposed design overcomes these problems by establishing the separation principle, by which the controller and observer can be designed separately. As a result of this, the global stabilization of the closed-loop system is established under the proposed control law. Finally, we present the simulation results illustrating the design methodology for the stabilizing output feedback controller.