Less Emissions With Lower Fuel Consumption

The Real Driving Emissions (RDE) directive has for the first time defined a test process for complying with emission limits in everyday traffic on the roads. The challenge is that consideration has to be given to far more factors impacting on the vehicle’s emission behavior, such as driving style and weather, than in the previous test processes. The influences are so varied that it is scarcely possible for development engineers to predict their effects when calibrating diesel engines and exhaust gas aftertreatment systems. IAV offers a remedy with a new overriding software architecture, which constantly optimizes the interaction between engine and exhaust gas system functions under all driving conditions.

This is where IAV’s new approach differs from previous concepts, in which different software domains were responsible for controlling the engine and the exhaust system. The task facing the calibration engineers consisted in matching the two domains in the best possible way. The huge testing workload and the varied operating conditions make it impossible for this procedure to optimize all system states occurring in the vehicle in real-world driving. IAV’s new closed-loop control strategy comes in at this point. It validates compliance with the emission limits for all driving conditions including those that cannot be predicted during the development phase, while ensuring the lowest possible fuel consumption at the same time.

“To put it simply, we program the control unit with the engineer’s know-how”, explains Enrico Neumann, Team Manager Control Innovations at IAV. While the engine is running, IAV’s new software architecture constantly matches the engine and exhaust gas aftertreatment parameters. To this end, the management system permanently compares the actual nitrogen oxide emissions at the exhaust tailpipe with the target value. The overriding control system then ensures that all technical possibilities are exploited to minimize the nitrogen oxide emissions. In this way, the engine and exhaust gas aftertreatment system are operated with maximum technical efficiency at all times and under all conditions. Neumann: “Our benchmark here is the statutory emission limit. And if the engine and exhaust system still offer reserves for further optimizing the interaction of consumption and emissions, we use the remaining degrees of freedom for additional improvements.” The management system controls and minimizes emissions under all conditions, regardless whether the vehicle is being tested or is already run under real operating conditions by the customer.

The new emission management concept needs no expensive additional hardware. The only input the system needs consists of the signals from the nitrogen oxide sensors already present in modern Euro-6 vehicles. Nor is any great additional calibration workload necessary, because special operating strategies such as those currently needed to heat the catalyst up and keep it hot can be dispensed with. On the other hand, a profound understanding of the system is required for correct implementation of the individual engine and exhaust functions with their technical possibilities and limitations in the overriding coordinator.

IAV’s simulation tests have clearly narrowed the variance in nitrogen oxide emissions under real driving conditions. In other words, real emissions can be adjusted and monitored with far greater accuracy during operation. “We can thus make better use of the potential offered by the installed hardware components so that components are not oversized with negative impacts in terms of costs and weight”, says Neumann. The simulation also showed a possible reduction in total nitrogen oxide emissions of up to 30 percent under real driving conditions. The next development step consists in engine dynamometer tests with a trial engine, which should take place before the end of 2018.