Event-Based Mean-Value Modeling of DI Diesel Engines for Controller Design

Models often use time rather than strokes (crank-angle) as the independent variable to describe engine dynamics despite the fact that the dynamics of an internal combustion engine are intrinsically linked to the combustion events. In this paper, two models are developed in parallel in which not only the independent variable is changed but the notion of mass flows as well: flows are in [g/s] for the time-based model and in [g/st] for the event-based model. Both models are of the same computational complexity and show the same accuracy in validation. The investigation of the model properties shows that variations in the flow-related parameters are reduced by a factor of two to five for the event-based model. However, those of the crankshaft dynamics are increased. It is concluded that the model should be chosen in context of the control system to be designed. For engine speed controllers, the time-based model should be used while for applications involving flow, e.g., EGR and VGT controllers, or if the controller is to be implemented with a constant sampling angle rather than sampling time, the event-based model is preferred.