Growing Complexity in the Powertrain

From discrete system development for engines and transmissions to the integrated, all-encompassing approach to the powertrain

The conventional internal combustion engine is facing increasing pressure. Driving bans are being discussed for more and more inner cities and 2017 may see the introduction of the blue (nitrogen oxide) badge. A further challenge to developers are Real Driving Emissions (RDE) and the new Worldwide Harmonized Light-Duty Vehicles Test Procedure (WLTP). In future, vehicles will be required to meet even tighter CO2 and emission limits – also in real-world driving situations.

IAV is moving the boundaries of existing development processes with innovative methods, technologies and test facilities. In the automotion interview Gerhard Buschmann, Executive Vice President for Diesel Mechatronics, and Matthias Kratzsch, Executive Vice President for Powertrain Development, report about the challenges from RDE and WLTP, and IAV’s approach to them.

What exactly is awaiting the automotive industry in the years to come?

Kratzsch: The driving challenge lies in constantly reducing a vehicle fleet’s CO2 limits, and doing so for all markets worldwide. In Europe, the average target of 95 grams of CO2 per kilometer has been defined from 2020. This varies only slightly from one vehicle manufacturer to another on account of their different vehicle weights. Exceeding the fleet limit value comes with a penalty of € 95 per gram of CO2 and vehicle, paid to the EU. A further reduction to 68 to 78 grams of CO2 per kilometer is being discussed for 2025. In the USA, there’s not only a CO2 target but also a separate miles-per-gallon target. Both are also tightened every year, with N2O and CH4 emissions in part being converted into CO2 emissions and making it even harder to reach the target. In China there is both an individual-vehicle as well as a fleet consumption target. To reach these targets, the CO2 emissions must fall by an average of three to five percent every year, depending on market – an enormous challenge.

Buschmann: In Europe, RDE adds to the challenge: The legislator has provided that manufacturers meet the first stage of this new regulation from 2017 onwards. In technical terms, this is above all highly challenging for nitrogen oxide emissions and will only be possible if exhaust gas aftertreatment works perfectly across the engine’s operating range.

What did you have to do to overcome the tough challenges from RDE and WLTP?

Buschmann: We have advanced many areas of the engineering process. For RDE and WLTP, we are making even greater use of dynamic DoE (Design of Experiments) on our dynamic engine dynamometers to examine the engine under all types of boundary conditions. On top of this, we can use our VeLoDyn tool to simulate the whole vehicle in a model, vary all parameters in the model and, based on this, ensure that all legal requirements will be met on the road later on. We have our own models for the engine, the vehicle, the catalytic converter, the driver and other components. And with VeLoDyn’s open architecture we can combine our models with those of our customers or component suppliers. Model-based calibration with systematically varied parameters as well as Monte Carlo methods help us validate calibration for RDE under all boundary conditions – it would be far too much work and virtually impossible to test everything on the road.

You just mentioned dynamic engine dynamometers. Which other test equipment is crucial for RDE and WLTP?

Buschmann: Our new high-altitude roller dynamometer in Berlin, for example, which is among the most modern and most versatile of its kind anywhere in the world. It allows us to simulate drives up to an altitude of 5,300 meters and at temperatures of between minus 30 and plus 40 degrees Celsius – that, of course, is a great help to us for RDE. The high-altitude roller dynamometer gives us a test facility you normally only find at OEMs and just a few component suppliers. Besides the high-altitude roller dynamometer we also make extensive use of our component test benches as well as our syngas laboratory where we can measure catalytic converters with extreme accuracy. This, for example, shows us exactly how well denoxing works under various boundary conditions, how much AdBlue we need to add and whether ammonia is unintentionally released. Using the test bench, we also simulate all components in physical-chemical models so that we can control all processes later on with the engine management system. Because, as I said: For RDE we need systems that operate perfectly under all circumstances.

Matthias Kratzsch, Executive Vice President for Powertrain Development at IAV

Matthias Kratzsch, Executive Vice President for Powertrain Development at IAV

What implications will WLTP and RDE have for the base engine?

Kratzsch:Toanswerthat,letusdistinguishbetween the demands from CO2 emission, classic pollutants, such as HC, CO and NOx as well as particulate matter emissions. To bring down CO2 emission, we must further reduce frictional losses throughout the powertrain. On the one hand, this can be done with new layouts of the piston-liner pairing by using improved materials, coatings and production technologies, optimized bearing layouts, by using low-viscosity oils and also by ways of reducing frictional loss in the transmission. On the other, we will also do away with measures to protect components in the gasoline engine. In turn, this will call for new solutions in engine thermal management – from new concepts for cooling components exposed to high temperatures, such as cylinder head and exhaust gas turbocharger turbine, to new designs of charge air and EGR cooler or even the entire cooling circuit. The tighter demands on particulate matter emissions are not only a challenge to calibration. The injection system must also be improved to meet the new demands from the combustion process. But engine oil can also contribute to particulate matter emissions. IAV is now able to separate particle matter from engine oil from the engine’s overall particulate matter emissions. To reduce this particulate matter component, we have developed and verified a new method for designing piston rings over recent months.

Is it enough to optimize the key components of the powertrain?

Kratzsch: No. The complexity of the targets, demands and boundary conditions is so high today that conventional development methods are no longer sufficient – it is no longer enough to optimize the engine, the transmission or the e-motor on their own. Instead, we need a new, integrated development approach. For this reason, IAV has developed a unique methodology: powertrain synthesis. This involves an all-encompassing, systematic and semi-automated process that takes account of all relevant facets and variants at requirement and technology level.

What’s so special about IAV’s powertrain synthesis?

Kratzsch: It compares and contrasts the requirements of the legislator and OEMs with the technical options at component level. This information lets us find the best possible solution for our customers because powertrain synthesis delivers the best system compromise between consumption, performance as well as production costs and technical input for the particular requirements concerned. It takes account of all variants and layouts of combustion engine, transmission, e-motor, power electronics, battery, operating strategy, vehicle and hybrid topology. For example, it can determine which topology can optimize the utility value in terms of energy efficiency, performance and costs under given boundary conditions, such as mobility concept or degree of automation. In a short time, we can search through a solution space of millions of options – that would have been utterly impossible just a few years ago. This provides the decisionmakers at our customers with objective criteria for charting the course for future product generations. This is so important because fundamental decisions have far-reaching consequences and, once made, can hardly be corrected. Powertrain synthesis is used about four to five years before the start of production.

Will RDE and WLTP cause costs to explode?

Kratzsch: Not necessarily. In our development activities it will be crucial for us to keep an eye on costs from the very start. To do this, IAV has been a firm believer in strict cost engineering and target costing for many years. We ascertain the costs of manufacturing all components at the early phase of a project. Cost management is involved right at the start of a development project. Our experts in cost engineering work closely with the component specialists because we want to evaluate both costs and functions for the whole unit. For example, instead of increasing injection pressure, it would also be possible to fit a vehicle with a more powerful e-machine to achieve emission targets at minimum cost.

Gerhard Buschmann, Executive Vice President for Diesel Mechatronics at IAV

Gerhard Buschmann, Executive Vice President for Diesel Mechatronics at IAV

How might environmental protection be tightened up in future?

Buschmann: At the moment, we only look at the environmental burden while a vehicle is being used. At some point or other, the legislator may well include the production of raw materials, manufacturing and recycling. In that case we will need to carry out a life cycle assessment (LCA). IAV is already looking at this subject even today with a view to assessing the impacts new vehicles will have on the environment in this respect.

There is a lot of talk about digitization today. Will this trend also be of help to you with regard to RDE and WLTP?

Buschmann: Of course it will. Today, we can record, save and evaluate far more data than we used to be able to do. Machine learning and artificial intelligence have made it possible to find links between events automatically and in this way identify the cause of problems. We have our own group of experts who are advancing these tools and methods for use in engine calibration. Thinking even further ahead, it will open up entirely new options: It would be possible to monitor vehicles while they are in customer operation and determine whether they still meet all the requirements. And if necessary, software updates could be provided that target any problems occurring in order to rectify them. Servicing could also be done whenever it became necessary. But that is still a few years down the line because there are many boundary conditions that need to be clarified. But even today, IAV is working flat out on the potential applications.

Thank you for talking to us.