Effects of customer use on emissions for optimised operation HEV

This paper describes a method to determine and optimise the real-world fuel consumption as well as CO2, NOx and soot emissions of an HEV in simulated customer operation, which significantly differs from driving cycle operation in terms of dynamics and effective speed. A method is developed to model the transient emission behaviour of a combustion engine using a semi-empiric approach. The transient emission models for the customer simulation are based on a variant transfer function (first or second order). It can calculate the transient torque as well as emissions (i.e. CO2, NOx, soot). In contrast to by now usual static emission maps, the dynamic model enables a more exact calculation of real emissions of engines. As the real emissions are achieved in customer use, the customer behaviour is considered in the optimisation process of the optimal operation strategy (OS). The multicriteria problem of minimising the emissions of CO2, NOx and soot simultaneously is transformed into a one-criterion problem via a target function. For the practical realisation of the operation strategy in a cycle, such as NEDC or WLTP, and customer use, an optimum is identified with a stable behaviour regarding the influences of parameter changes. In order to predict customer actions and behaviour via simulations, vehicle measurements were carried out and analysed, which leads to a well-sorted database of different driving styles, vehicle loads and driving environments. Based on this database, a statistical driving environment model as well as a statistical driver model was built up in MATLAB/Simulink. This allows simulating driving operations under real customer conditions for vehicles, i.e. hybrid electric vehicles (HEV), and thus gaining representative results for fuel consumption and emissions. In addition, research is done on the effects of an optimised operation strategy for different driving cycles in comparison to the customer operation. It is shown that emissions in customer use differ significantly from those in driving cycles. The paper concludes with an analysis of the optimisation of emissions of an HEV during launch, using operation mode changes as an example.