Model-based control of a diesel engine variable geometry turbine and exhaust gas recirculation system using a linear parameter varying methodology

Abstract

Diesel engines are widely used for passenger cars these days because of their high fuel efficiency. Although diesel engines have emission problems (oxides of nitrogen, particulate matter) originated from the compression ignition combustion characteristics, both of these types of emissions have been reduced by after-treatment systems such as selective catalytic reduction, diesel particulate filter and so on. In addition, due to the stringent carbon dioxide regulations, the fuel-efficient diesel engine as a powerplant for passenger cars occupies a major position in the passenger car market in Asia and Europe. In order to make diesel engines clean and efficient, appropriate control systems for air-path, combustion, and after-treatment are required. Particularly, an air-path control system is the most important part of the control system of diesel engines because the air-path system determines the dynamic behaviour of the engines. Control strategies for combustion and after-treatment systems are generated based on the air-path behaviour. In this paper, modelling and control of an air-path system for a turbocharged common-rail direct injection diesel engine are proposed. A linear parameter varying methodology is adopted for deriving an air-path system model. The linear parameter varying technique has the advantage of converting a complex nonlinear system in modelling into a simplified linear system. The air-path system model is derived with a linear three-state model, and the model accuracy is verified by driving cycle tests. The framework of a robust H controller design is applied to the simplified linear parameter varying air-path model, and this synthesized H controller is validated with engine experiments. The experimental results show that linear parameter varying model-based diesel engine air-path control allows better performance than a production engine management system, which requires massive calibration work.