Design of Robust Controller for an Uncertain System described by Unstructured Uncertainty Model using Small Gain Theorem

A simple and easy technique is used to design a robust Proportional Integral Derivative (PID)/ Proportional Integral (PI) controller for an uncertain system described by unstructured uncertainty model. The controller design is based on Small Gain theorem and it guarantees closed loop stability for input variations across its full working range. The uncertain plant under different working ranges is described by a family of corresponding transfer functions. In this paper design of a robust controller has been demonstrated for a warm air-drying chamber. Closed loop step response and frequency response plots are shown to prove that the proposed controller provides robust operation of the chosen uncertain plant. Comparison of the results with those obtained from other design methods shows that the proposed controller design methodology proves to be a better option.