The main objective of this paper is to use a robust controller based on quantitative feedback theory on vehicle to control engine at idle speed. There are different parameters affecting vehicle fuel consumption, fuel efficiency, exhaust emission reduction and better power delivery from which Changes in engine works condition. In this paper, the various steps of controller design are undertaken and an optimal robust controller is designed. This controlling approach, proposes a transparent and practical controller design methodology for uncertain single-input single-output and multivariable plants. In engine, Throttle Valve dynamic has multivariable nonlinear transfer functions. For this reason in this paper QFT technique is used for designing the proposed controller. After linearization a robust controller is designed for tracking problem. Next, simulation for tracking problem has been carried out which indicates successful design of controller. The simulation results show very good engine behaviour under controlled actions in situations where the uncontrolled throttle has undesired behaviour. It is also shown that with the presence of different uncertainties, the controller is able to produce accurate desired responses.

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