Design of Composite Sliding Mode Controller for Large-scale Processes

This article proposes composite sliding mode control scheme for large scale processes. In systems with slow and fast modes, several works have addressed the study of multi time-scale systems. Majority of the literature in singular perturbations deal with two time-scale systems. Usually higher order systems are decomposed into two comparatively lower order subsystems, namely, `slow' and `fast' subsystems. Then the composite control is developed for reduced subsystems. Sliding Mode control, a powerful tool dealing with uncertainty and disturbances, has been utilized for decades. However, it is not straightforward to synthesize a sliding mode control law for singularly perturbed systems due to complication of different time-scale behavior and the discontinuous nature of switching action.In this paper, design of a composite controller in terms of the individual subsystem controllers is derived. Then the proposed composite sliding mode controller design for singularly perturbed system in the presence of matched bounded external disturbance is investigated on some large-scale processes.