Model-based (ECMS) or heuristic energy management strategies may include a fuel cost mixed with emissions cost. This was mostly introduced using steady-state maps but these strategies generally do not consider the transient NOX emissions. Instead of combining steady state and transient objectives into the ECMS, this paper proposes an approch where the two objectives are separated. The proposed stategy is cascaded with the EMS in order to correct the electric and motor torque split ratio computed by the ECMS during the transient phases. The electric motor torque assistance focuses on transient NOx emissions and the split ratio is modified only during transient operations where NOx peaks are produced. The strategy tends to smooth the engine torque using the motor torque as torque compensator. Mean value models of the intake manifold burned gas ratio coupled with a NOx production model are introduced into the EMS. Using such models into a vehicle supervision level is the novelty of the approach. The Simulation results have shown that the transient part of the NO* emissions can be reduced. It is clear that increasing the motor torque for short-term engine transient has a potential to reduce the NOX emissions. The strategy allows to limit the transient part of the emissions without modifying the steady state part. Also, the use of the electric motor during transients has a price and the transient NO reduction slightly increases fuel consumption. This trade-off can be tuned with the reduction factor. The proposed strategy can be valuable to deal with driving cycles presenting more transient phases. This will be the case for Euro 7 vehicles with the new worldwide harmonized light-duty transient cycle. The further work will consist in the experimental validation of this transient torque control strategy. Some model assumptions will be verified and the temperature model depedency with the BGR is currently investigated. The main focus for the strategy improvement is to define a feasible NOX trajectory that leads to the engine torque trajectory including the system saturation.
Transient torque control of a diesel hybrid powertrain for NOx limitation
2012
10 Seiten, 16 Bilder, 3 Tabellen, 17 Quellen
Aufsatz (Konferenz)
Englisch
Hybridantrieb , Energiemanagement , heuristisches Verfahren , modellgestützte Regelung , Drehmomentregelung , Emissionsminderung , Stickstoffoxidemission , transienter Zustand , Ansaugrohrkrümmer , mathematische Modellierung , Motorbetriebsverhalten , Übergangszustand , Motordrehmoment , Kompensation