General presentation
Sliding speed control

The main purpose of sliding-state control (or, more precisely, variable-structure control generating a sliding state) is to achieve a closed-loop dynamic that is largely independent of the process dynamic and, above all, of any variations in it. In this sense, it can be considered as belonging to the robust control class.

Theoretically, it relies essentially on the use of a discontinuous control whose aim is to maintain the system's evolution on a carefully chosen switching surface, which effectively fixes the resulting dynamics (somewhat analogously to what the return transmittance does in a high-gain system). In other words, the control only serves to bring about and then maintain the evolution of the system on the surface. This surface then determines the performance obtained.

From a practical point of view, the use of discontinuous control...