Marco Günther

Variable step-size discrete dynamic programming for vehicle speed trajectory optimization

Predictive energy management has become a new focus of the automobile industry for its high potential of further reducing energy consumption. Based on previous works on predictive speed optimization using discrete dynamic programming (DDP), this paper introduces a novel approach of applying DDP with variable step size in stage variable discretization, which can realize a better tradeoff between precision and computational cost. In this approach, a “meshing” algorithm searches the points of interest (POI), such as speed limit change, traffic lights, and road curvatures, where changes in vehicle speed are expected. The algorithm increases the step-size resolution close to these points and reduces the resolutions in positions further away from POI, where the optimized vehicle speed is insensitive to the step size. With this approach, the position of POI can be precisely located to solve the DDP problem. In a test case with a relatively high density of POI, the computational cost is reduced by more than 53% by only sacrificing less than 1% of precision compared to a fixed step-size discretization with high resolutions. It can be expected that, with a lower density of POI, the computational cost will be reduced even further.

Zuordnung und Bewertung von Motorgeräuschkomponenten

Die wahrgenommene Geräuschqualität von Verbrennungsmotoren wird maßgeblich durch das Auftreten und die Ausprägung einzelner Störgeräuschkomponenten beeinflusst. Am Lehrstuhl für Verbrennungskraftmaschinen der RWTH Aachen University wurde im Rahmen eines FVV-Forschungsvorhabens eine Methodik entwickelt, die es erlaubt, aus einem Motorgesamtgeräusch einzeln anhörbare Motorkomponentengeräusche zu extrahieren und die Geräuschbelästigung durch diese Komponenten automatisiert zu quantifizieren. Darüber hinaus bietet die Methodik die Möglichkeit, aus den getrennten Geräuschkomponenten zur Zielwertdefinition ein neugewichtetes Motorgesamtgeräusch zu synthetisieren. AUTOREN

Alignment of simulation methodology and measurement techniques to predict the HC distribution at catalyst inlet

Injection of fuel into the exhaust system is increasingly being used to support the operation of exhaust gas aftertreatment systems. When injecting a fluid into the exhaust system, one major challenge is to define an optimum position of the injector and its spray hole configuration along with an appropriate injection pressure. Simulation techniques are a suitable means to support the corresponding development process. Hence, the project “Exhaust Fuel Injection” was initiated. Project target is the alignment of simulation methods and measurement techniques to predict the HC distribution in radial and axial direction at the inlet of a catalyst. This includes the development of suitable measurement techniques to determine the hydrocarbon concentrations upstream and downstream of a catalyst.

Development of a Model for Predicting the Knock Boundary in Consideration of Cooled Exhaust Gas Recirculation at Full Load

Engine knock limits the efficiency of turbocharged SI engines at high loads. The occurrence of this phenomenon can be inhibited by deploying recirculation of cooled exhaust gas (EGR) at full load. However, the development of full load EGR combustion systems cannot be per-formed in the 0D/1D engine simulation, as no meaningful models for the reliable prediction of the knock limit under the influence of EGR exist.

Development of optimized exhaust gas heating strategies for passenger car Diesel engines by means of variable valve train applications

The cold start and heating phase of passenger car Diesel engines is essential to comply with the actual emission legislation targets. The HC and CO emissions that are produced immediately after a cold start contribute to more than 70 % of the total cycle results. The initially low temperature level of the exhaust gas aftertreatment system components results in a very low conversion efficiency. With a further strengthening of the emission legislation, the first phases of the emission test cycles will become even more important. It is aspired to achieve the required, even fast heat-up of the exhaust aftertreatment without fuel consumption penalties to reduce engine-out emissions efficiently. Application of a variable valve train system (VVT) can be an additional technology to address this challenge.