A Challenging Future for the IC Engine: New Technologies and the Control Role

New regulations on pollutants and, specially, on CO2 emissions could restrict the use of the internal combustion engine in automotive applications. This paper presents a review of different technologies under development for meeting such regulations, ranging from new combustion concepts to advanced boosting methods and after-treatment systems. Many of them need an accurate control of the operating conditions and, in many cases, they impose demanding requirements at a system integration level. In this framework, engine control disciplines will be key for the implementation and development of the next generation engines, taking profit of recent advancements in models, methods and sensors. According to authors’ opinion, the internal combustion engine will still be the dominant technology in automotive applications for the next decades.

The transportation industry and, in particular, the automotive industry, is facing major challenges. The strong increase in the global demand for motorized mobility in the coming decades, the inevitable diversification of energy sources given the limited nature of fossil hydrocarbon reserves, the energy saving needs for a sustainable development and the environmental requirements both in terms of local pollution and of CO 2 emissions cannot be met in the medium to long term with the solutions offered by private and commercial vehicles equipped with classic gasoline or diesel engines.
Although these energy converters have significantly progressed, both in terms of engine architecture (supercharging, direct gasoline injection) and of exhaust gas aftertreatment (three-way catalyst, particulate filter, SCR (Selective Catalytic Reduction), etc.), tougher standards and economic imperatives require the rapid development of new solutions.
Vehicle electrification and in particular hybridization combining an internal combustion engine with an electric motor, provide a response to societal expectations. However, as the number of possible solutions and the number of variables to deal with literally exploded, manufacturers have had to develop new tools for the development, control and supervision based largely on electronics, computer simulation and real-time computing.
Electronics, initially applied to ignition and injection, is now combined to computing via microprocessors. This association has led to substantial progress in the control and supervision of engines in actual operation.
Computer technology has opened the field of component and system modeling. Modeling has made it possible to shorten the tedious experimental calibration phases and has also helped, through real-time simulations, to control engines more efficiently.
Thus, engine control has become over time a discipline in itself, integrated from the beginning in automotive design. It is no longer limited to the internal combustion engine, but looks at the whole powertrain, for example by providing solutions for transmission control and for energy management on board hybrid vehicles.
The E-COSM conferences, from the first edition in 2006, have followed the advances in engine control together with those in modeling and simulation. This special issue of OGST, dedicated to the 2012 edition of E-COSM, illustrates well the wide scope of engine control today. Beyond on-board energy management, engine control has also become a tool for emissions management. It is also successfully applied in efforts to recover wasted energies or in the management of increasingly complex transmission systems. And it will soon unleash the full potential of information and communications technology, in particular through communicating vehicles. Oil & Gas Science and Technology -Rev. IFP Energies nouvelles, Vol. 70 (2015) E-COSM'12 has examined the most recent developments in the fields of engine and powertrain control and modeling, emphasizing the interplay between control design and validation on the one hand, and physical modeling and simulation on the other. As in the previous editions, the aim was to offer academic and industrial researchers and practitioners working in the automotive control sector an opportunity to meet one another and exchange views and ideas at a relatively small-scale event.
Indeed, among the 166 participants from 18 countriesmostly from France, Sweden, USA, Germany, Italy, Spain, UK, Austria, Netherlands and Switzerlanda significant share came from industry (more than 25%). Young authors and student participation was very strong with more than 50 PhD students registered. A well-balanced mix of contributions from universities, research institutes and industry, can also be found in the papers presented at the conference. Papers came mostly from France, Sweden, Germany, USA, Spain, Italy and Austria.
The conference covered not only the "traditional" engine and powertrain control, simulation and modeling topics which have been the focus of the previous editions of E-COSM, but also new ones as diagnostics, thermal management and vehicle dynamics control. Roughly one third of the papers were related to hybrid vehicles and electrification. The significant weight of these topics can be clearly seen in the tag cloud representing the relative frequency of the main keywords indicated in the submissions (Fig. 1).
The 63 regular papers (out of 73 submitted) were presented in 13 regular sessions plus a poster session. A special session was devoted to the presentation of the results of the PHEV Control Benchmark, a competition among research teams in industry and academia to find the best energy management strategy for a plug-in hybrid electric vehicle. Nine teams from eight institutions submitted a solution. The 2 000 1 award, made available by the IFP School -Fondation Tuck Chair on Hybrid Vehicle and Energy Management, was won by the University of Linköping team, led by Martin Sivertsson, under the supervision of Prof. Lars Eriksson.

THE SELECTION FOR OGST
Due to the fairly high quality of the contributions, E-COSM'12 has provided abundant material for journal publication. The most representative and best-reviewed regular papers have been selected and proposed for consideration in two journals: Control Engineering Practice and OGST. Out of this selection, peer-reviewed full versions of the original conference papers have eventually been published: 12 papers appeared in a special section of Volume 29 of Control Engineering Practice in August 2014 and seven others in this special issue of OGST. This E-COSM'12 issue also contains the full version of the paper submitted for the PHEV Control Benchmark by the contest winner, and four keynote papers, for a total of 12 articles. Let us start with the keynote paper from the lecture of F. Payri, J.M. Luján, C. Guardiola and B. Pla, "A Challenging Future for the IC Engine: New Technologies and the Control Role", which perfectly sets the tone for this issue. The authors feel that the internal combustion engine will still be the dominant technology in automotive applications for the next decades and forecast that current technological over-diversification will persist over the mid-term. In this context, they consider engine control as an enabling tool not only at a subsystem level but also, and especially, at a system integration level. U. Christen and R. Busch's second keynote paper, "The Art of Control Engineering: Science Meets Industrial Reality", brilliantly illustrates the gap between what is considered the state of the art in control in academia and the way control is practiced in the automotive industry. By no means a dismissal of scientific advances, this article appeals for a fruitful dialog between academia and industry: industry should learn about the latest theoretical developments; academia should be aware of industrial practice and of tools that are missing for industrial applications. One of the examples discussed is energy management for hybrid electric vehicles, and the next paper, "Energy Management of Hybrid Electric Vehicles: 15 Years of Development at the Ohio State University", from G. Rizzoni and S. Onori's plenary lecture, is an excellent illustration of how such an important topic has been addressed in a top-level academic research center, providing solutions that, over time, are closer and closer to industrial application. The last of the keynote papers, "Automotive Catalyst State Diagnosis Using Microwaves" of R. Moos and G. Fischerauer, presents a novel approach to determine the catalyst state directly by a microwave-based technique. This is an illustrative example of a new technology studied in academia, which has the potential to supersede in the future some of the technologies currently used by manufacturers for exhaust gas aftertreatment diagnosis and control.
The following two papers highlight the fundamental role of modeling for control. In "Control-Oriented Models for Real-Time Simulation of Automotive Transmission Systems", the authors N. Cavina, E. Corti, F. Marcigliano, D. Olivi and L. Poggio present a Dual Clutch Transmission model, based on a detailed physical description of hydraulic circuit, clutches, synchronizers and gears, and simplified vehicle and internal combustion engine submodels. The model is able to reproduce the fast dynamics of the actuation system while maintaining a simulation step size large enough for real-time applications, and can thus be used to support the development of a Editorial model-based controller and to assess its performance on a Hardware-in-the-Loop test bench. In "Combustion Noise and Pollutants Prediction for Injection Pattern and Exhaust Gas Recirculation Tuning in an Automotive Common-Rail Diesel Engine", by I. Arsie, R. Di Leo, C. Pianese and M. De Cesare, a multi-zone model is developed to simulate engine combustion and predict noise and pollutant emissions depending on injection pattern and EGR rate. Models like this one, predictive, yet validated against a limited amount of experimental data, allow performing detailed analysis of the influence of engine control variables and can be used for EMS tuning. Modeling is also the focus of "Investigation of Cycle-to-Cycle Variability of NO in Homogeneous Combustion", where the authors, A. Karvountzis-Kontakiotis and L. Ntziachristos, investigate cycleto-cycle variability in spark ignition engines and present a detailed chemistry model for the prediction of NO formation in homogeneous engine conditions. Indeed, combustion variability, which may occur due to fluctuations in both early flame kernel development and in turbulent flame propagation has a significant impact on fuel consumption and emissions.
Pollutant emissions are not a major concern solely for conventional powertrains. When dealing with diesel hybrid electric vehicles, it is advisable to design energy management strategies which do not focus on fuel consumption reduction only, but also take into account pollutant emissions. In the paper "Energy Management Strategies for Diesel Hybrid Electric Vehicle", O. Grondin, L. Thibault and C. Quérel propose an energy management strategy which succeeds in limiting the NO x emission both in steady-state and transient operating conditions, with a small impact on fuel consumption. In "Integrated Energy and Emission Management for Diesel Engines with Waste Heat Recovery Using Dynamic Models" by F. Willems, F. Kupper, G. Rascanu and E. Feru, another non conventional powertrain is described where a trade-off between fuel consumption and pollutant emission must be sought: a heavy-duty Euro-VI diesel engine coupled with a Rankine-cycle waste heat recovery system. An integrated energy and emission management strategy is presented which optimizes the CO 2 -NO x trade-off by minimizing online the operational costs associated with fuel and AdBlue consumption.
Optimization is also at the core of the following two papers. T. Nilsson, A. Fröberg and J. Åslund, in "Development of Look-Ahead Controller Concepts for a Wheel Loader Application", address the control of a multi-mode continuously variable transmission wheel loader, in order to minimize, or at least to reduce, fuel consumption without having a negative impact on drivability or performance of the machine. Two dynamic-programming-based strategies are developed and compared in simulation. In "Design Methodology of Camshaft Driven Charge Valves for Pneumatic Engine Starts", by M.M. Moser, C. Voser, C.H. Onder and L. Guzzella, pneumatic engine starts using camshaft driven charge valves are discussed, as a lower-cost alternative to the electric start function commonly found in HEV. A general design methodology is presented, based on the minimization of the amount of air used for the start while limiting the time needed to reach the target engine speed at a prescribed value. The methodology is applied to a two-cylinder engine and the results are verified experimentally.
The paper "Design and Evaluation of Energy Management using Map-Based ECMS for the PHEV Benchmark", by M. Sivertsson and L. Eriksson, which describes the winning contribution in the PHEV Benchmark, concludes this E-COSM'12 issue of OGST. The control is an adaptive strategy based on a map-based Equivalent Consumption Minimization Strategy (ECMS) approach, developed and implemented in the simulator provided for the PHEV Benchmark. Very interestingly, the fuel consumption results obtained by this strategy in the benchmark are really close to the optimal ones, calculated offline with a foreknowledge of the driving cycles.

THE FUTURE OF E-COSM
Since the first E-COSM in 2006, the idea that the development of emerging automotive technologies must be accompanied (from the beginning) by the design of appropriate advanced control strategies has gained ground. The two following editions in 2009 and 2012 have confirmed that automatic control is a key success factor for demanding engine, powertrain and vehicle technologies, provided that a solid support from physical modeling and simulation is available. However, if model-based control can now be considered mature as a whole, several promising approaches, largely successful in other industrial domains, still lack industrial strength. This is typically the case with the implementation of control strategies based on real-time optimization under constraints, which have an enormous potential for automotive applications. Moreover, the possibilities offered by multivariable control are still seldom exploited, despite the ever-increasing number of actuators and sensors. Advances in automatic control are encouraging, but it might prove necessary to rethink engine and powertrain torque control structures to fully benefit from them.
More generally, as not every innovation in the automotive industry has delivered on its promises, expectations in terms of improved reliability, reduced fuel consumption and pollutant emissions, at affordable costs, remain very high. And they must now be met throughout the life of a vehicle and in all cases of usage. On-board diagnostics, which plays an increasingly important role in modern vehicles, provides several new opportunities for research. In all domains, the focus is shifting from the component level to the system and inter-system levels, with important contributions from the new technologies of information and communication. These new trends, already present in the 2012 edition, are expected to be at the core of E-COSM'15, which will hopefully provide, once again, an interesting arena to discuss the latest academic research developments, as well as industrial experience in deploying "real-world" applications. L'électronique, appliquée initialement à l'allumage puis à l'injection, est maintenant combinée à l'informatique par microprocesseurs ce qui a permis des progrès substantiels pour le contrôle-commande des moteurs en fonctionnement réel.

Éditorial
L'informatique a de son côté ouvert le champ de la modélisation des équipements et des systèmes. Cette modélisation a permis de raccourcir les fastidieuses phases de mise au point expérimentales et a également, au travers des simulations temps réel, permis de commander plus efficacement les moteurs.