DESIGN OF SLIDING MODE CONTROLLER FOR CUK CONVERTER

Abstract

Classical control theory has a very developed set of analysis and design tools for Linear Time Invariant (LTI) systems, however most of the real systems are non-linear and time variant. Real plants operate in presence of uncertainties and disturbances. Designer needs to take careful consideration of effect of these uncertainties on the dynamic behaviour of system during designing the controller as these uncertainties can degrade the performance of the system or can make the system unstable. Conventional classical control design techniques need accurate mathematical model, which may not always be available. Conventional controllers are effective in stabilizing a plant but they do not provide robustness against disturbances and parameter uncertainties. Therefore many robust control techniques like model predictive control, non-linear adaptive control, back-stepping, sliding model control and others have been developed to design a control system where classical control theory may not give satisfactory performance. Out of these techniques Sliding Mode Control is characterized by simplicity in analysis, design, high efficiency and robustness with respect to matched uncertainty and parameter variations. In this report introduction to Sliding Mode Control theory and design has been presented and its prominent characteristics like robustness, order reduction and control chattering has been discussed. Sliding mode controller design has been illustrated for linear and non-linear systems with examples of fourth order systems. Boundary layer solution method of chattering suppression has been illustrated. Non-linear converters are widely used in industry to regulate DC power supply. Cuk converter is a fourth order non-linear converter capable of stepping down or stepping up DC voltage. Practical application of Sliding Mode Control technique has been done to control a Cuk converter prototype model using Matlab/SlMULlNK and dSPACE control desk. Simulation and hardware results verify the robustness and simplicity of Sliding mode control technique. Therefore Sliding Mode Control technique proves to be a promising robust control technique not only in theory but in practice also