흡배기 시스템 모델을 이용한 터보 과급 디젤엔진의 과급압력 및 흡기유량 앞먹임 제어

Abstract

Manifold absolute pressure (MAP) and mass air flow (MAF) are important control variables in a diesel engine equipped with VGT (Variable Geometry Turbocharger) and EGR (Exhaust Gas Recirculation) systems. The transient control performances of MAP and MAF critically affect the drivability and emission of a diesel engine. In order to improve the transient control performances of these control variables, a feedforward controller is necessary. However, it is hard to control these variables accurately because MAP and MAF are highly nonlinear and coupled each other. This paper presents a model based feedforward control algorithm of MAP and MAF that can consider the nonlinear MIMO characteristics. The physical inverse models of the VGT vane and EGR valve are developed to determine feedforward set positions of each actuator. An air system model was also developed to estimate un-measurable states that are used for the model based feedforward control algorithm. Dynamic correction is applied to temperature models because temperature states of the air system have relatively slow dynamics compared to other physical states. As a result, the proposed feedforward control algorithm improves control performance under transient operating condition compared to a look-up table based feedforward controller. State estimation and model based feedforward control algorithms were developed using only the sensors of a mass production engine. The performance of the developed control algorithm was validated by real-time engine experiments.