Asian Research Thesis Index

Abstract

Sliding Mode Control(SMC) theory, being a robust control technique, has a variety of applications in industry. It showed fruitful results since its introduc- tion. However, the control law suffers from the well known chattering phenomena which may cause problems in applications. Despite the robust nature of SMC, it becomes sensitive to uncertainties in reaching phase in certain applications. This sensitivity may result in marginal stability or even in the instability of the system. Thus the reaching phase elimination may enhance the robustness. In addition, in some real applications, it is needed to have the settling time as small as possible. Therefore, efforts were devoted to solve these main issues. The existing litera- ture of sliding mode control is rich in methods used for chattering attenuation robustness enhancement and performance improvement. They solved some of the discussed issues at the cost of the other and vice versa. For example, the chat- tering reduction resulted in robustness loss as well as performance loss and vice versa. In this thesis, it is tried to have robust performance with reduced chat- tering. For this purpose, a novel output feedback based sliding mode strategy is proposed for uncertain nonlinear systems which is based on the existing the- ory of dynamic sliding mode and basic theory of integral sliding mode control. The proposed cont enhances the performance of the system while rejecting the uncertainties. The proposed control law is designed for both SISO and MIMO uncertain nonlinear systems. The claims of the proposed technique are verified via some ex- amples. Furthermore, this control algorithm is extended to both SISO and MIMO nonlinear systems operating under matched and unmatched state dependent un- certainties.

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