Modeling and control of an engine fuel injection system

Abstract

Control of automotive exhaust emission has become an important research area to meet the more stringent automotive emission regulations. Beside the modification on internal combustion engine, control engineering is seen as another approach to improve and meet these requirements. This project focuses on the design and development of a control system to reduce the harmful waste of automotive exhaust emission. The control system aims to regulate the amount of fuel injected into the combustion chamber such that the air to fuel ratio (AFR) is maintained within the allowable range. The control process in this project is demonstrated based on an analytical engine model that clearly describe engine’s air and fuel dynamic with no loss of engine system performance. Since the dynamics of the internal combustion engine and fuel injection systems are highly nonlinear, a linear model is obtained in this project, based on a system identification approach to allow methodical application of linear control theories. Two types of control strategy are employed – the linear quadratic Gaussian (LQG) controller and the fuzzy logic controller (FLC). The LQG controller, designed based on the linear model of the engine system, results in good controlled output response but with large controller signal variation. The FLC, however, provides better controlled output response by reducing overshoot gain and transient effect occurred in LQG controller design.