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Sliding Mode Control

Sliding-control techniques in VSS improves considerably the dynamic behavior of these systems compared to the conventional control methods. The dynamic performances of VSS in sliding regime are basically a fast transient response without overshoot and a low sensitivity to external perturbations. Switching converters constitute an important case of VSS. Depending on the task they are supposed to do, and the control algorithm, they are nonlinear time-varying dynamical systems. They can be modeled as VSS because of the abrupt topological changes that the circuit, commanded by a discontinuous control action, undergoes. They constitute a natural field of application of Sliding Mode Control techniques, which is based on the following two main concepts: 1) to define a surface, i.e. a relationship between state variables, in such a way that, if trajectories slide on this surface, a previously stated behavior (for instance reaching an equilibrium point) is achieved, and 2) to design an appropriate control law forcing this surface to be an attractor and a dynamically invariant set.