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  • 101.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    An overview of various control benchmarks with a focus on automotive control2019In: Control Theory and Technology, ISSN 2095-6983, Vol. 17, no 2, p. 121-130Article in journal (Refereed)
    Abstract [en]

    There exists a gap between control theory and control practice, i.e., all control methods suggested by researchers are not implemented in real systems and, on the other hand, many important industrial problems are not studied in the academic research. Benchmark problems can help close this gap and provide many opportunities for members in both the controls theory and application communities. The goal is to survey and give pointers to different general controls and modeling related benchmark problems that can serve as inspiration for future benchmarks and then specifically focus the benchmark coverage on automotive control engineering application. In the paper reflections are given on how different categories of benchmark designers, benchmark solvers and third part users can benefit from providing, solving, and studying benchmark problems. The paper also collects information about several benchmark problems and gives pointers to papers than give more detailed information about different problems that have been presented.

  • 102.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    CHEPP – A Chemical Equilibrium Program Package for Matlab2005In: SAE technical paper series, ISSN 0148-7191, Vol. 4, no 113, p. 730-741Article in journal (Refereed)
    Abstract [en]

    A program package, that calculates chemical equilibrium and thermodynamic properties of reactants and products of a combustion reaction between fuel and air, has been developed and validated. The package consists of the following four parts: 1) A program for calculating chemical equilibrium. 2) A database that contains thermochemical information about the molecules, which comes from the GRI-Mech tables. 3) A GUI that allows the user to easily select fuels, fuel/air ratio for the reaction, and combustion products. 4) A set of functions designed to access the thermochemical database and the chemical equilibrium programs. Results are validated against both the NASA equilibrium program (Gordon and McBride, 1994) and the program developed by Olikara and Borman (1975). It is shown that the new method gives results identical to those well recognized Fortran programs.

  • 103.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Development of a Hardware and Software Platform that Constitutes a Step Towards Adaptive Engine Control1998Conference paper (Refereed)
  • 104.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Documentation for the Chemical Equilibrium Program Package CHEPP2000Report (Other academic)
    Abstract [en]

    A program package has been developed that calculates chemical equilibrium and thermodynamic properties of reactants and products of a combustion reaction between fuel and air. The package consists of the following four parts: 1) A program for calculating chemical equilibrium. 2) A database that contains thermochemical information about the molecules, which comes from the GRI-Mech tables. 3) A GUI that allows the user to easily select fuels, fuel/air ratio for the reaction, and combustion products. 4) A set of functions designed to access the thermochemical database and the chemical equilibrium programs. The program package is validated with respect to how well it can reproduce results shown in the standard literature. The thermodynamic properties for the individual molecules and the results from the equilibrium calculation all agree with the results shown in the literature. There is almost perfect agreement, between the results produced by the program package and those shown in the book by Heywood, when comparing the thermodynamic properties of the mixture of equilibrium products.

    Download full text (pdf)
    Documentation for the Chemical Equilibrium Program Package CHEPP
  • 105.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Increasing the Efficiency of SI-Engines by Spark Advance Control and Water Injection1997Report (Other academic)
    Abstract [en]

    By directly measuring in-cylinder parameters and adjusting the spark advance, the engine efficiency can be maximized. A feedback scheme for spark-advance control using the ionization current as sensed variable has earlier been presented. One issue is to verify that the algorithm works when the environmental conditions changes the burn rate. Humidity significantly affects the burn rate and active water injection is used to slow down the combustion giving a peak pressure position (PPP) that occurs too late. The ionization current based feedback-scheme adjusts the spark advance, and moves the PPP back to optimum. An additional result is that the engine efficiency can be increased by combining active supply of water to the combustion and the spark-advance control scheme.

    Download full text (pdf)
    Increasing the Efficiency of SI-Engines by Spark Advance Control and Water Injection
  • 106.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Les rencontres scientifiques d’IFP energies nouvelles RHEVE 2011: International Scientific Conference on Hybrid and Electric Vehicles2013In: Oil & Gas Science and Technology: Revue de l'Institut Français du Pétrole, ISSN 1294-4475, Vol. 68, no 1, p. 9-12Article in journal (Other academic)
    Download full text (pdf)
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  • 107.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Mean Value Models for Exhaust System Temperatures2003In: SAE technical paper series, ISSN 0148-7191, Vol. 111, no 3Article in journal (Refereed)
    Abstract [en]

    Exhaust temperatures are important for turbine and catalyst performance. A set of exhaust temperature models suitable for turbo matching as well as design and analysis of engine control systems are developed and investigated. The models are lumped parameter heat transfer models, that fall within the category of mean value engine models. The model is developed for describing exit temperatures from the exhaust manifold and temperature drops in pipe sections in the exhaust system. The components used to model the exhaust temperature are: engine out temperature, temperature drop in a straight pipe, and a set of heat transfer modes. The model is validated using data from three different engines. It is shown that, for a spark ignited engine operating at MBT and stoichiometric conditions, it is sufficient to model the engine out temperature as a linear function of mass flow. Recommendations for tuning the model are also given. A thorough survey of exhaust heat transfer literature is also made together with a comparative summary of the different heat transfer modes that are present in the exhaust.

  • 108.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Methods for Ionization Current Interpretation to be Used in Ignition Control1995Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It is desirable to measure engine performance for several reasons, e.g. when computing the spark advance setting in spark-ignited (SI) engines. There exists two methods, among others, of measuring the performance, such as measuring the pressure and the ionization current. Since the ionization current reflects the pressure, it is interesting to study if it is possible to extract information from the ionization current about the combustion and pressure.

    Three different algorithms for extracting information from the ionization current are studied. The first algorithm, ion peak, searches the \second peak" in the ionization signal. The second algorithm computes the centroid. In the third algorithm a model of the ionization signal structure is fitted to the ionization signal.

    The algorithms are tested in four operating conditions. The first algorithm uses the local information around the second peak and is sensitive to noise. The second algorithm uses a larger portion of the ionization signal, which is more stable. It provides promising results for engines with a clear post flame phase. The third algorithm, ion structure analysis, fits an ideal model to the ionization signal. The algorithm provides promising results, but the present implementation requires much computational effort.

    Download full text (pdf)
    Methods for Ionization Current Interpretation to be Used in Ignition Control
  • 109.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Modeling and Control of Supercharged SI and CI Engines2006In: Proceedings of New Trends in Engine Control, Simulation and Modelling, 2006Conference paper (Refereed)
    Abstract [en]

    A component based modeling methodology for turbocharged engines is described and applied. Several component models are compiled and reviewed. In addition new models are developed for the compressor efficiency, compressor flow, and turbine flow. Two application examples are finally given where the modeling methodology and the component models have been used. The applications are: Observer design and air/fuel ratio control of SI engines. Control design of DI engines with VGT and EGR.

    CONFERENCE INFORMATION: Les Rencontres Scientifiques de l’IFP : "New Trends in Engine Control, Simulation and Modelling" 2-4 October 2006, IFP, Rueil-Malmaison, France

  • 110.
    Eriksson, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Modeling and Control of Turbocharged SI and DI Engines2007In: Oil & gas science and technology, ISSN 1294-4475, E-ISSN 1953-8189, Vol. 62, no 4, p. 523-538Article in journal (Refereed)
  • 111.
    Eriksson, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Modeling and Control of Turbocharged SI and DI Engines2006Conference paper (Refereed)
  • 112.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Requirements for and a Systematic Method for Identifying Heat-Release Model Parameters1998In: SAE technical paper series, ISSN 0148-7191, Vol. 107, p. 898-908Article in journal (Refereed)
    Abstract [en]

    Heat release analysis by using a pressure sensor signal is a well recognized technique for evaluation of the combustion event, and also for combustion diagnostics. The analysis includes tuning of several parameters in order to accurately explain measured data. This work presents and investigates a systematic method for estimating parameters in heat release models and minimizing the arbitrary choices. In order for the procedure to be systematic there are also the requirements on the model, that it includes no inherent ambiguities, like over-parameterization with respect to the parameters and to the information contained in the measurements. The fundamental question is which parameters, in the heat release model, that can be identified by using only cylinder pressure data. The parameter estimation is based on established techniques, that constructs a predictor for the model and then minimizes a least-squares objective function of the prediction error. The study is performed on data measured on a SAAB 2.3 liter, four stroke four cylinder, normally aspirated, gasoline engine.

  • 113.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Simulation of a vehicle in longitudinal motion with clutch engagement and release2001Conference paper (Refereed)
    Abstract [en]

    A simple model for driver and vehicle in longitudinal motion is developed and simulated. The focus is on describing and handling simulation of clutch lock and clutch release which changes the model structure, both during start and gear shifts, in Simulink. Special attention is given the problem of simulating start and stop of a vehicle with rolling resistance at zero speed. Only principles for simulating the system with variable structure is of interest and therefore the models are maintained at lowest possible complexity. The system is successfully simulated and the validation is performed using three scenarios: one with only clutch lock and clutch release, one with start and stop of vehicle, and one full European drive-cycle.

  • 114.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Spark Advance for Optimal Efficiency1999In: SAE technical paper series, ISSN 0148-7191, Vol. 108, p. 789-798Article in journal (Refereed)
    Abstract [en]

    Most of todays spark-advance controllers operate in open loop but there are several benefits of using feed-back or adaptive schemes based on variables deduced from the cylinder pressure. A systematic study of how different engine conditions change the deduced variables, at optimal ignition timing, is performed. The analysis is performed using a one-zone heat-release model and varying the model parameters. The deduced variables that are studied are: position of the pressure peak, mass fraction burned levels of 30%, 45%, 50%, and 90%, and the pressure ratio. For MBT timing the position for 45% mass fraction burned changed least under a large variety of changes in burn rate. Cycle-to-cycle variations do not have a significant effect and it suffices to evaluate the mean values for the burn rate parameters. The pressure ratio produces values similar to the mass fraction burned and requires no separate treatment.

  • 115.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    VehProLib - Vehicle Propulsion Library, Library development issues2003In: Proceedings of the 3rd International Modelica Conference, Linköping, November 3-4, 2003Conference paper (Refereed)
    Abstract [en]

    A Modelica library called Vehicle Propulsion Library is under development. Its structure and important design issues are described and the current status is shown. The vehicle propulsion library aims at providing functionality for studying and analyzing the performance of different powertrain configurations. The included components cover the range from zero dimensional in-cylinder models to longitudinal models for complete vehicles.

  • 116.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Andersson, Ingemar
    Chalmers.
    An Analytic Model for Cylinder Pressure in a Four Stroke SI Engine2003In: SAE technical paper series, ISSN 0148-7191, Vol. 111, no 3Article in journal (Refereed)
    Abstract [en]

    An analytic model for cylinder pressures in spark ignited engines is developed and validated. The main result is a model expressed in closed form that describe the in-cylinder pressure development of an SI engine. The method is based on a parameterization of the ideal Otto cycle and takes variations in spark advance and air-to-fuel ratio into account. The model consists of a set of tuning parameters that all have a physical meaning. Experimental validation on two engines show that it is possible to describe the in-cylinder pressure of a spark ignited combustion engine operating close to stoichiometric conditions, as a function of crank angle, manifold pressure, manifold temperature and spark timing.

  • 117.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Frei, Simon
    Onder, Christopher
    Guzzella, Lino
    Control and Optimization of Turbo Charged Spark Ignited Engines2002Conference paper (Refereed)
    Abstract [en]

    The subject of this study is the trade-off between fuel economy and transient performance in turbocharged engines. It quantifies the losses and gains of different engine control strategies. Two extreme strategies are analyzed, one for optimal fuel economy and the other for fast transient response. Models for the components that influence the fuel economy are developed and described. An optimization problem for best fuel economy is solved analytically and a fuel-optimal controller is implemented based on that result. This controller is compared to one which is optimized for fast transient response with respect to the gains in fuel economy and losses in transient response. Simulations of a highly boosted engine show that a fuel-optimal controller can improve the fuel economy of a vehicle operated at cruising speed by 1-3% and at highway speed by 4%, and that the highest achievable improvement is above 10%. The losses in transient response are around 0.4 s for cruising conditions. Furthermore, measurements on a low-boosted engine on a test bench are used to show that the fuel-optimal controller reduces fuel consumption by 1.9% at highway conditions.

  • 118.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Anders
    Scania CV AB, Sweden.
    Thomasson, Andreas
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    The AAC2016 Benchmark - Look-Ahead Control of Heavy Duty Trucks on Open Roads2016In: IFAC PAPERSONLINE, ELSEVIER SCIENCE BV , 2016, Vol. 49, no 11, p. 121-127Conference paper (Refereed)
    Abstract [en]

    A benchmark problem for fuel efficient control of a truck with engine, driveline, and chassi models on a given mission with a road topography profile is formulated. The Vehicle model is provided with open access to the vehicle model equations and parameters. It is compiled from model components validated in previous research projects and the result is a non-linear model that contains mixed continuous and discrete control variables. The driving; scenario is provided as road slope profile and a desired trip time. The problem to solve is a combination of engine-, driveline- and Vehicle-control while fulfilling demands on emissions, driving time, legislative speed, and engine protections. (C) 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

  • 119.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Lindell, Tobias
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Leufvén, Oskar
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Thomasson, Andreas
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Scalable Component-Based Modeling for Optimizing Engines with Supercharging, E-Boost and Turbocompound Concepts2012In: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 5, no 2, p. 579-595Article in journal (Refereed)
    Abstract [en]

    Downsizing and turbocharging is a proven technology for fuel consumption reduction in vehicles. To further improve the performance, electrified components in the turbocharger arrangements have been proposed, and investigations have shown acceleration improvements, emission reductions, and further fuel conversion efficiency benefits. Simulation tools play an important role in the design process as the interplay between component selection, control strategy, system properties and constraints is very complex. Evaluations are performed with respect to BSFC map, fuel consumption in a drive cycle, acceleration performance, as well as many other aspects. A component-based engine and vehicle model is developed and evaluated to facilitate the process of assessing and optimizing the performance of e.g. engine, charging system, and electrical machine components. Considerations of the execution time and model fidelity have resulted in a choice of models in the mean value engine model family. The turbocharging and electrical system models have all been evaluated using experimental data from engine dynamometer tests and turbocharger gas stand measurements and other dedicated component measurements.

  • 120.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Llamas, Xavier
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Ekberg, Kristoffer
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Leek, Viktor
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Dynamic Modeling, Simulation and Control of Turbochargers2017In: Dynamic Modeling, Simulation and Control of Turbochargers: Advancements, Applications and Research / [ed] Evangelos G. Giakoumis, Nova Science Publishers, Inc. , 2017, p. 176-206Chapter in book (Other academic)
    Abstract [en]

    Turbochargers stand for the dominating dynamics in engines and in the design, analysis, and optimization of new engines, it becomes more and more important to analyze system interactions and dynamics. In the development process, modeling, simulation, and optimization have evolved from being used in research to being stan- dard tools for engineers and play an important role in the engine development. To be successful in the process, one needs to both have component models, and methods and tools where system models can be built, analyzed, and optimized. The component models should also have capabilities to extrapolate behavior outside the nominal re- gion since design explorations can go to extreme points while searching for optimal solutions.

    The first part of the chapter summarizes the compressor and turbine maps and how they can be used in simulation models. A generic model structure for compressors and turbines that fit into an engine modeling and simulation framework is described. Then the Ellipse compressor flow model and the Enthalpy based efficiency model will be described, they have been developed so that they can be integrated in a simulation environment and also used in optimization. Their main features are that they are ca- pable of extrapolating compressor behavior outside the normal range of the map in a physically sane way. In addition to this, a tuning method has been developed that takes a normal manufacturer map and returns all model parameters for compressor flow and efficiency models. Thereafter, compact turbine flow and efficiency models will be described.

    Then the attention is turned to simulation and optimization applications where compressor models are used. First an engine experiment where compressor surge oc- curs is modelled and used to illustrate the extrapolation capabilities using the models presented. Then the scope is turned to control and optimization of turbocharger opera- tion on an engine, where the focus will be on a VGT controlled diesel engine equipped with EGR. First the steady state mapping of the engine is demonstrated, then optimal control of the turbo operation is investigated using modern computer tools for dynamic optimization. 

  • 121.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nezhadali, Vaheed
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Andersson, Conny
    Linköping University.
    Compressor Flow Extrapolation and Library Design for the Modelica Vehicle Propulsion Library - VehProLib2016In: SAE 2016 World Congress and Exhibition, SAE International , 2016, article id 2016-01-1037Conference paper (Refereed)
    Abstract [en]

    Modelbased systems engineering is becoming an important tool when meeting the challenges of developing the complex future vehicles that fulfill the customers and legislators ever increasing demands for reduced pollutants and fuel consumption. To be able to work systematically and efficiently it is desirable to have a library of components that can be adjusted and adapted to each new situation. Turbocharged engines are complex and the compressor model serves as an in-depth example of how a library can be designed, incorporating the basic physics and allowing fine tuning as more information becomes available. A major part of the paper is the summary and compilation of a set of rules of thumb for compressor map extrapolation. The considerations discussed are extrapolation to surge, extrapolation to restriction region, and extrapolation out to choking. Furthermore the compressor diameter is coupled to the maximum performance of the compressor such as maximum speed, mass flow, and pressure ratio. All this is a result of an analysis of a database of more than 300 compressors. The paper uses the compressor modeling to discuss how wishes for extendability and reuse of component performance influences the library design. A Modelica library named Vehicle Propulsion Library VehProLib has been developed to meet these goals by including basic components that give a starting point for modeling and at the same time allows reuse and extendablility.

  • 122.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Increasing the Efficiency of SI-Engines by Spark-Advance Control and Water Injection1998Conference paper (Refereed)
    Abstract [en]

    Engine efficiency can be maximized by directly measuring in-cylinder parameters and adjusting the spark advance, using a feedback scheme based on the ionization current as sensed variable. Water injection is shown to increase the engine efficiency, if at the same time the spark advance is also changed when water is injected to obtain maximum efficiency. A spark-advance control scheme, that takes the water injection into account, is thus necessary to increase the efficiency.

  • 123.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Ionization Current Interpretation for Ignition Control in Internal Combustion Engines1997In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 5, no 8, p. 1107-1113Article in journal (Refereed)
    Abstract [en]

    Spark advance setting in spark-ignited engines is used to place the in-cylinder pressure curve relative to the top dead center. A feedback scheme, not a calibration scheme, based on ionization current is proposed here. It is thus related to pressure sensor feedback schemes, that have reported good results, but have not yet been proved cost effective, due to the cost of the pressure sensor. The method proposed here is very cost-effective, since it uses exactly the same hardware and instrumentation (already used in production cars) that is used to utilize the spark plug as a sensor to detect misfire and as a sensor for knock control. A key idea in the method is to use parameterized functions to describe the ionization current. These parameterized functions are used to separate out the different phases of the ionization current. Special emphasis is laid on getting a correct description of the pressure development. The results are validated on a SAAB 2.3 l production engine by direct comparison with an in-cylinder pressure sensor (used only for validation, not for control), but also by using a physical model relating the ionization current to the pressure.

  • 124.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Modeling and control of engines and drivelines2014Book (Refereed)
  • 125.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Non-linear Model-Based Throttle Control2000Conference paper (Refereed)
    Abstract [en]

    Spark ignited engines require accurate control of both air and fuel, and one important component in this system is the throttle servo. A non-linear throttle model is built and used for control design. It is shown that the non-linear model-based controller improves the performance compared to a conventional gain scheduled PI controller. Furthermore a method for estimating the load torque that the air flow produces on the throttle shaft is presented.

  • 126.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Towards On-Board Engine Calibration with Feedback Control Incorporating Combustion Models and Ion-sense2003In: Automatisierungstechnik, ISSN 0178-2312, Vol. 51, no 5, p. 204-212Article in journal (Refereed)
    Abstract [en]

    Die Technik der Ionenstrommessung dient der Untersuchung des Verbrennungsvorganges im Zylinder. Bei der Ionenstrommessung wird nach der Zündung eine Spannung zwischen der Mittel- und der Massenelektrode der Zündkerze angelegt. Anschliessend wird der Stromfluss zwischen diesen beiden Elektroden gemessen. Das Signal des Ionenstroms ist eine komplexe Funktion, die Informationüber den Zylinderdruck, die Zylindertemperatur und den Verbrennungsvorgang enth ält. Um diese Information zu erhalten, bedient man sich eines einfachen analytischen Ionenstrommodells. Das Modell besteht aus detaillierten Untermodellen zur Analyse des Drucks, der Temperatur, der thermischen Ionisierung und des Ionisierungsstroms innerhalb des Zylinders. Die Kalibrierung der Modellparameter erfolgt on-board durch eine Signalinterpretation. Experimentelle Untersuchungen zeigen eine gute Übereinstimmung mit dem Modell und ebnen damit den Weg hin zu einer Echtzeit-Kalibrierung des Motors. Ion-sense is a technique to probe the in-cylinder combustion by applying, after ignition, a sense voltage across the spark plug gap and measure the current through the gap. This current measurement is a complicated function that contains a lot of information about the in-cylinder pressure, temperature and combustion. To extract this information, a major contribution here is a simple analytical ionization current model that consists of explicit analytical submodels for in-cylinder pressure, temperature, thermal ionization, and ionization current. Since the model is analytical, the on-board signal interpretation is a simple adaptation of some model parameters. Experimental validation shows good agreement, and thus paves the way towards real-time on-board engine calibration.

  • 127.
    Eriksson, Lars
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Nielsen, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering.
    Brugard, J.
    Bergstrom, J.
    Pettersson, F.
    Andersson, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Modeling of a turbocharged SI engine2002In: Annual Reviews in Control, ISSN 1367-5788, E-ISSN 1872-9088, Vol. 26 I, p. 129-137Article in journal (Refereed)
    Abstract [en]

    Turbocharged SI engines are a major possibility in the current trend of down-sized engines with preserved drivability performance. Considering control and supervision it is favorable to have a mean value model to be used e.g. in observer design. Such models of turbo engines are similar to those of naturally aspirated engines, but there are some special characteristics, e.g. the interconnected gas flows, the intercooler, the difference in relative sizes between the gas volumes (compared to naturally aspirated engines), the turbo, and the waste gate. Here, a model is developed with a strategy to find a model for each engine component (air filter, compressor, after cooler (or intercooler), throttle, engine, turbine, waste gate, and a lumped model for the catalyst and exhaust) as they behave in an engine setting. When investigating agreement with measured data and sensitivity of possible model structures, a number of interesting issues are raised. The experiments and the model validation have been performed on a Saab 2.3 1 production engine.

  • 128.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Glavenius, Mikael
    Mecel AB.
    Closed Loop Ignition Control by Ionization Current Interpretation1998In: SAE technical paper series, ISSN 0148-7191, Vol. 106, no SAE Technical Paper 970854, p. 1216-1223Article in journal (Refereed)
    Abstract [en]

    The main result of this paper is a real-time closed loop demonstration of spark advance control by interpretation of ionization current signals. The advantages of such a system is quantified. The ionization current, obtained by using the spark plug as a sensor, is rich on information, but the signal is also complex. A key step in our method is to use parameterized functions to describe the ionization current. The results are validated on a SAAB 2.3 l, normally aspirated, production engine, showing that the placement of the pressure trace relative to TDC is controlled using only the ionization current for feedback.

  • 129.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nytomt, Jan
    Mecel AB.
    Ignition Control by Ionization Current Interpretation1997In: SAE technical paper series, ISSN 0148-7191, Vol. 105, no SAE Technical Paper 960045, p. 165-171Article in journal (Refereed)
    Abstract [en]

    Spark advance setting in spark-ignited engines is used to place the in-cylinder pressure curve relative to the top dead center. It is demonstrated that ionization current interpretation is feasible to use for spark advance control to optimize engine performance. A feedback scheme, not a calibration scheme, based on ionization current is proposed. It is thus related to pressure sensor feedback schemes, that have reported good results, but have not yet proven cost effective due to the cost of the pressure sensor. The method proposed here is very cost effective since it uses exactly the same hardware and instrumentation (already used in production cars) that is used to utilize the spark plug as a sensor to detect misfire and as a sensor for knock control. The only addition for ignition control is further signal interpretation in the electronic engine control unit.</P> A key idea in our method is to use parameterized functions to describe the ionization current. These parameterized functions are used to separate out the different phases of the ionization current. Special emphasis is made to get a correct description of the pressure development. The results are validated on a SAAB 2.3 l production engine by direct comparison with an in-cylinder pressure sensor (used only for validation, not for control), but also by using a physical model relating the ionization current to the pressure.

  • 130.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Norrlöf, Mikael
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering. ABB AB - Robotics, Västerås, Sweden.
    Improved Drive Cycle Following with an ILC Supported Driver Model2015In: 4th IFAC Workshop on Engine and Powertrain Control, Simulation and Modeling ECOSM’15, The International Federation of Automatic Control (IFAC) , 2015, Vol. 48, p. 347-353Conference paper (Refereed)
    Abstract [en]

    Drive cycle following is important for concept comparisons when evaluating vehicle concepts, but it can be time consuming to develop good driver models that can achieve accurate following of a specific velocity profile. Here, a new approach is proposed where a simple driver model based on a PID controller is extended with an Iterative Learning Control (ILC) algorithm. Simulation results using a nonlinear vehicle and control system model show that it is possible to achieve very good cycle following in a few iterations with little tuning effort. It is also possible to utilize the repetitive behavior in the drive cycle to accelerate the convergence of the ILC algorithm even further.

  • 131.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Rizzo, Gianfranco
    University of Salerno, Italy.
    Chamaillard, Yann
    University of Orleans, France.
    Editorial Material: Editorial: Special Issue Section on Automotive Control in CONTROL ENGINEERING PRACTICE, vol 61, issue , pp 183-1852017In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 61, p. 183-185Article in journal (Other academic)
    Abstract [en]

    n/a

  • 132.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Sivertsson, Martin
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Calculation of Optimal Heat Release Rates under Constrained Conditions2016In: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 9, no 2, p. 1143-1162Article in journal (Refereed)
    Abstract [en]

    The work extends a methodology, for searching for optimal heat release profiles, by adding complex constraints on states. To find the optimum heat release profile a methodology, that uses available theory and methods, was developed that enables the use of state of the art optimal control software to find the optimum combustion trace for a model. The methodology is here extended to include constraints and the method is then applied to study how sensitive the solution is to different effects such as heat transfer, crevice flow, maximum rate of pressure rise, maximum pressure, knock and NO generation. The Gatowski single zone model is extended to a pseudo two zone model, to get an unburned zone that is used to describe the knocking and a burned zone for NO generation. A modification of the extended Zeldovich mechanism that makes it continuously differentiable, is used for NO generation. Previous results showed that the crevice effect had a significant influence on the shape for the unconstrained case where a two mode combustion was seen, one initial pressure rise and one constant pressure phase. Here it is shown that it still has a significant influence on the appearance until the maximum pressure limit is reached and becomes the dominating constraint. In the unconstrained case no conditions had combustion before TDC all started after, but when limitations are considered and come into play the combustion can now start before TDC to avoid excessive losses during the expansion. When introducing constraints on the NO formation through the extended Zeldovich mechanism the combustion takes the shape of a three mode combustion, one initial rapid burning, one later rapid burning and a constant pressure phase. In summary it is shown that the methodology is able to cope with the introduced constraints.

  • 133.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Sivertsson, Martin
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Computing Optimal Heat Release Rates in Combustion Engines2015In: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 8, no 2Article in journal (Refereed)
    Abstract [en]

    The combustion process has a high impact on the engine efficiency, and in the search for efficient engines it is of interest to study the combustion. Optimization and optimal control theory is used to compute the most efficient combustion profiles for single zone model with heat transfer and crevice effects. A model is first developed and tuned to experimental data, the model is a modification of the well known Gatowski-model (Gatowski et.al 1984). This model is selected since it gives a very good description of the in-cylinder pressure, and thus the produced work, and achieves this with a low computational complexity. This enables an efficient search method that can maximize the work to be developed. First, smooth combustion profiles are studied where the combustion is modeled using the Vibe function, and parametric optimization is used to search for the optimal profile. Then, the most efficient combustion process with a completely free combustion is studied with theory and software for optimal control. A parameter study is performed to analyze the impact of crevice volume and air/fuel ratio λ. The results show that the losses have a high impact on the behavior, which is natural, and that the crevice effect has a very distinct effect on the optimal combustion giving a two mode appearance similar to the Seiliger cycle.

  • 134.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Thomasson, Andreas
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Cylinder state estimation from measured cylinder pressure traces - A Survey2017In: 20th IFAC World Congress / [ed] Denis Dochain, Didier Henrion, Dimitri Peaucelle, 2017, Vol. 50, p. 11029-11039, article id 1Conference paper (Refereed)
    Abstract [en]

    In the search for improved performance and control of combustion engines there is a search for the sensors that gives information about the combustion profile and the state of the gases in the combustion chamber. A particular interest has been given to the potential use of the cylinder pressure sensor and there is quite a lot of work that has been made in this area. This paper provides a comprehensive list of references and summarizes applications and methods for extracting information from the cylinder pressure sensor about the combustion and the gas state. The summary highlights the following topics related to cylinder pressure: measurement chain, cylinder torque, extraction of the burn profile, combustion placement, knocking, cylinder air mass, air to fuel ratio, residual gas estimation, and cylinder gas temperature estimation. The focus in the summary is on the latter topics about the gas state but thermodynamic analysis of the combustion process also gets a longer treatment since many methods for information extraction rely on the thermodynamic properties.

  • 135.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Thomasson, Andreas
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Ekberg, Kristoffer
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Reig, Alberto
    Univ Politecn Valencia, Spain.
    Eifert, Mark
    Ford Res and Innovat Ctr, Germany.
    Donatantonio, Fabrizio
    Univ Salerno, Italy.
    DAmato, Antonio
    Univ Salerno, Italy.
    Arsie, Ivan
    Univ Salerno, Italy.
    Pianese, Cesare
    Univ Salerno, Italy.
    Otta, Pavel
    Czech Tech Univ, Czech Republic.
    Held, Manne
    KTH Royal Inst Technol, Sweden.
    Voegele, Ulrich
    TH Ingolstadt, Germany.
    Endisch, Christian
    TH Ingolstadt, Germany.
    Look-ahead controls of heavy duty trucks on open roads - six benchmark solutions2019In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 83, p. 45-66Article in journal (Refereed)
    Abstract [en]

    A benchmark problem for fuel efficient control of a truck on a given road profile has been formulated and solved. Six different solution strategies utilizing varying degrees of off-line and on-line computations are described and compared. A vehicle model is used to benchmark the solutions on different driving missions. The vehicle model was presented at the IFAC AAC2016 symposium and is compiled from model components validated in previous research projects. The driving scenario is provided as a road slope profile and a desired trip time. The problem to solve is a combination of engine-, driveline- and vehicle-control while fulfilling demands on emissions, driving time, legislative speed, and engine protections. The strength of this publication is the collection of all six different solutions in one paper. This paper is intended to provide a starting point for practicing engineers or researchers who work with optimal and/or model based vehicle control.

    The full text will be freely available from 2020-11-07 15:14
  • 136.
    Eriksson, Lars
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Wahlström, Johan
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Klein, Marcus
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Physical Modeling of Turbocharged Engines and Parameter Identification2009In: Automotive Model Predictive Control: Models, Methods and Applications, Springer Verlag , 2009, 1, p. 53-71Chapter in book (Refereed)
    Abstract [en]

    The common theme in this chapter is physical modeling of engines and the subjects touch three topics in nonlinear engine models and parameter identification. First, a modeling methodology is described. It focuses on the gas and energy flows in engines and covers turbocharged engines. Examples are given where the methodology has been successfully applied, covering naturally aspirated engines and both single and dual stage turbocharged engines. Second, the modeling with the emphasis on models for EGR/VGT equipped diesel engine. The aim is to describe models that capture the essential dynamics and nonlinear behaviors and that are relatively small so that they can be utilized in model predictive control algorithms. Special emphasis is on the selection of the states. The third and last topic is related to parameter identification in gray-box models. A common issue is that parameters with physical interpretation often receive values that lie outside their admissible range during the identification. Regularization is discussed as a solution and methods for choosing the regularization parameter are described and highlighted.

  • 137.
    Eriksson, Magnus
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Modelling and Control of the AC-system in Heavy Duty Vehicles2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this thesis is to investigate the Air Conditioning system in a heavy duty truck and to develop a control strategy for the case when low cooling capacity is needed from the AC-system.

    A model of the AC-system was developed in order for an efficient controller to be designed. The model was designed to comprise of all the basic behaviours that the AC- system has, rather than to be an exact model of the system. As the AC-system showed to be very complex, a number of limitations in the model had to be made.

    The AC-system has two temperature sensors and is actuated by turning the AC- compressor on or off. Two different control strategies were tested for the control of the AC-compressor. The first was to use a controller to directly control the compressor clutch and the second one utilised a pulswidth modulated control structure were the controller stated the pulswidth to be used. Both control structures were implemented in the computer model, the AC-rig and in a truck in a climate chamber.

    Both control strategies showed to fulfil the demands on the system in the somewhat idealistic circumstances during which they were tested.

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    Modelling and Control of the AC-system in Heavy Duty Vehicles
  • 138.
    Eriksson, Mikael
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Graffman, Oskar
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Modelling and Simulation of Heat Pump Systems for Hybrid and Electrical Vehicles2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Hybridization and electrification of modern vehicles is today a reality. This effects the construction of the heating and cooling systems in vehicles where earlier the waste heat from the combustion engine was a great heat source. Heat pump systems are commonly used in heating systems in buildings and can therefore also be used for heating the cabin and different components in a vehicle. Modelling a heat pump system and performing simulations gives the advantage of investigating the heating performance of the heat pump during certain conditions. In this master thesis, which is performed in a pre-study project that is performed under the Swedish Electromobility Centre, a heat pump is modelled and the heating performance when changing the vapour quality is investigated during cold environments. Also how the heating capacity for different refrigerants and changing size and speed of compressor is simulated. With the methods and assumptions used, especially isentropic compression, the results shows that decreasing the vapour quality increase the mass flow in the heat pump circuit but the decrease in specific heating is larger which results in an overall decrease in heating capacity. The goal of 10 kW heating capacity can be achieved by increasing the compressor size or make use of waste heat from other vehicle components.

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  • 139.
    Eriksson, Nils
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Estimation of Distance to empty for heavy vehicles2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The distance to empty (DTE) for a heavy vehicle is valuable information both forthe driver and the hauler company. The DTE is estimated as the ratio between the current fuel level and a representative mean fuel consumption. This means the fuel consumption is a prediction of the most likely future mean fuel consumption based on earlier data. It is calculated by applying a forgetting filter on the signal of the momentary fuel consumption in the engine. The filter parameter control how many values that contributes to the output. This is a balance between desired robustness and adaptability of the estimate.

    Initially, a pre-stored value is used as an estimate of the mean fuel consumption. By this, the driver gets a first hint of the DTE value and the estimation of the DTE gets a good starting point. Stored values will adapt continuously with an online algorithm using vehicle data from previous runs. An alternative to showing the DTE is to present the time to empty when the vehicle speed is close to zero.

    The accuracy of the proposed algorithm depends on the quality of the input signals. With the current input signals, it is possible to get a DTE estimate that, over a longer time period, decrease in the same pace as the distance meter increase. This is considered as a good validation measurement. If altitude data for the current route would be used, a more accurate DTE estimate could be obtained. The sample distance for this altitude data could however be set to a 1000 meter without affecting the estimate significantly.

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  • 140.
    Eriksson, Tommie
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Parallel Hybridization of a Heavy-Duty Long Hauler2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Long haulage of heavy-duty trucks weighing over 15-ton stands for nearly 50% of the fuelconsumption among trucks, making them the most fuel consuming category. This indicatesthe potential benefits in improving the fuel efficiency for said category. Hybridization is onepossible solution.Hybrid vehicles are vehicles with two or more power sources in the powertrain. Differentpowertrain configurations, hybridization levels and hybrid concepts are best suitedfor different applications. With prices for fossil fuels constantly rising hybridization is animportant technology to improve fuel efficiency.Different variations of configurations and concepts enables many choices when decidingon a hybrid driveline. A simulation tool for efficiently comparing various hybrid drivelineswould be a great asset when deciding on a configuration for a certain vehicle application. Forthis thesis the application in focus is the previously mentioned category, a heavy duty longhauler weighing 36-ton.The modeling approach used for the simulation tool is called quasistatic modeling or"backward modeling". This name comes from, based on a chosen drive cycle, the resistingforces which act on the vehicle can statically be calculated at each step from the velocityprofile. The required power to drive along the drive cycle can then be calculated backwardswithin the powertrain resulting in a fuel consumption for the combustion engine. For thisthe free QSS-toolbox for Matlab Simulink has been used as a base and modified when needed.The configuration chosen to be implemented is a parallel electric hybrid and was chosenfor its good characteristics for the type of driving highways provide. For this configurationtwo types of controllers are used, one being an Equivalent Consumption Minimization Strategycontroller and the other a simple, rule based heuristic controller.The results for both controllers show small benefits with hybridization of the longhauler compared with the conventional which in the long run would make bigger differencebecause of the large consumption in whole. A sensitivity analysis was also done showingthat improving conventional vehicle parameters can be as beneficial as hybridization.

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  • 141.
    Florell, Christoffer
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Utilizing Look-Ahead Information to Minimize Fuel Consumption and NOx Emissions in Heavy Duty Vehicles2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Producing more fuel efficient vehicles as well as lowering emissions are of high importance among heavy duty vehicle manufactures. One functionality of lowering fuel consumption is to use a so called \emph{look-ahead control strategy}, which uses the GPS and topography data to determine the optimal velocity profile in the future. When driving downhill in slopes, no fuel is supplied to the engine which lowers the temperature in the aftertreatment system. This results in a reduced emission reduction capability of the aftertreatment system.

    This master thesis investigates the possibilities of using preheating look-ahead control actions to heat the aftertreatment system before entering a downhill slope, with the purpose of lowering fuel consumption and $NO_x$ emissions. A temperature model of a heavy duty aftertreatment system is produced, which is used to analyse the fuel consumption and $NO_x$ reduction performance of a Scania truck. A Dynamic Programming algorithm is also developed with the purpose of defining an optimal control trajectory for minimizing the fuel consumption and released $NO_x$ emissions.

    It is concluded that the Dynamic Programming optimization initiates preheating control actions with results of fuel consumption reduction as well as $NO_x$ emissions reductions. The best case for reducing the maximum amount of fuel consumption results in 0.14\% lower fuel consumption and 5.2\% lower $NO_x$ emissions.

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  • 142. Order onlineBuy this publication >>
    Fors, Victor
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Optimal Braking Patterns and Forces in Autonomous Safety-Critical Maneuvers2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The trend of more advanced driver-assistance features and the development toward autonomous vehicles enable new possibilities in the area of active safety. With more information available in the vehicle about the surrounding traffic and the road ahead, there is the possibility of improved active-safety systems that make use of this information for stability control in safety-critical maneuvers. Such a system could adaptively make a trade-off between controlling the longitudinal, lateral, and rotational dynamics of the vehicle in such a way that the risk of collision is minimized. To support this development, the main aim of this licentiate thesis is to provide new insights into the optimal behavior for autonomous vehicles in safety-critical situations. The knowledge gained have the potential to be used in future vehicle control systems, which can perform maneuvers at-the-limit of vehicle capabilities.

    Stability control of a vehicle in autonomous safety-critical at-the-limit maneuvers is analyzed by the use of optimal control. Since analytical solutions of the studied optimal control problems are intractable, they are discretized and solved numerically. A formulation of an optimization criterion depending on a single interpolation parameter is introduced, which results in a continuous family of optimal coordinated steering and braking patterns. This formulation provides several new insights into the relation between different braking patterns for vehicles in at-the-limit maneuvers. The braking patterns bridge the gap between optimal lane-keeping control and optimal yaw control, and have the potential to be used for future active-safety systems that can adapt the level of braking to the situation at hand. A new illustration named attainable force volumes is introduced, which effectively shows how the trajectory of a vehicle maneuver relates to the attainable forces over the duration of the maneuver. It is shown that the optimal behavior develops on the boundary surface of the attainable force volume. Applied to lane-keeping control, this indicates a set of control principles similar to those analytically obtained for friction-limited particle models in earlier research, but is shown to result in vehicle behavior close to the globally optimal solution also for more complex models and scenarios.

    List of papers
    1. Formulation and interpretation of optimal braking and steering patterns towards autonomous safety-critical manoeuvres
    Open this publication in new window or tab >>Formulation and interpretation of optimal braking and steering patterns towards autonomous safety-critical manoeuvres
    2019 (English)In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 57, no 8, p. 1206-1223Article in journal (Refereed) Published
    Abstract [en]

    Stability control of a vehicle in autonomous safety-critical at-the-limit manoeuvres is analysed from the perspective of lane keeping or lane changing, rather than that of yaw control as in traditional ESC systems. An optimal control formulation is developed, where the optimisation criterion is a linear combination of the initial and final velocity of the manoeuvre. Varying the interpolation parameter in this formulation turns out to result in an interesting family of optimal braking and steering patterns in stabilising manoeuvres. The two different strategies of optimal lane-keeping control and optimal yaw control are shown to be embedded in the formulation and result from the boundary values of the parameter. The results provide new insights and have the potential to be used for future safety systems that adapt the level of braking to the situation at hand, which is demonstrated through examples of how to exploit theresults.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2019
    Keywords
    Vehicle stability, yaw control, lane keeping, lane change, avoidance manoeuvre, at-the-limit
    National Category
    Vehicle Engineering
    Identifiers
    urn:nbn:se:liu:diva-152896 (URN)10.1080/00423114.2018.1549331 (DOI)000470891200008 ()
    Funder
    Knut and Alice Wallenberg Foundation
    Note

    Funding agencies: Swedish Government (Sveriges Regering); Wallenberg AI, Autonomous Systems and Software Program (WASP) (Knut och Alice Wallenbergs Stiftelse) - Knut and Alice Wallenberg Foundation

    Available from: 2018-11-27 Created: 2018-11-27 Last updated: 2019-10-30Bibliographically approved
    2. Attainable force volumes of optimal autonomous at-the-limit vehicle manoeuvres
    Open this publication in new window or tab >>Attainable force volumes of optimal autonomous at-the-limit vehicle manoeuvres
    2019 (English)In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, p. 1-22Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    With new developments in sensor technology, a new generation of vehicle dynamics controllers is developing, where the braking and steering strategies use more information, e.g. knowledge of road borders. The basis for vehicle-safety systems is how the forces from tyre–road interaction is vectored to achieve optimal total force and moment on the vehicle. To study this, the concept of attainable forces previously proposed in literature is adopted, and here a new visualisation technique is devised. It combines the novel concept of attainable force volumes with an interpretation of how the optimal solution develops within this volume. A specific finding is that for lane-keeping it is important to maximise the force in a certain direction, rather than to control the direction of the force vector, even though these two strategies are equivalent for the friction-limited particle model previously used in some literature for lane-keeping control design. More specifically, it is shown that the optimal behaviour develops on the boundary surface of the attainable force volume. Applied to lane-keeping control, this observation indicates a set of control principles similar to those analytically obtained for friction-limited particle models in earlier research, but result in vehicle behaviour close to the globally optimal solution also for more complex models and scenarios.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2019
    Keywords
    Active safety, force vectoring, vehicle dynamics control, tyre–road interaction, vehicle manoeuvre strategy
    National Category
    Vehicle Engineering
    Identifiers
    urn:nbn:se:liu:diva-156638 (URN)10.1080/00423114.2019.1608363 (DOI)000470461700001 ()2-s2.0-85064738528 (Scopus ID)
    Note

    Funding agencies: Swedish Government; Wallenberg AI, Autonomous Systems and Software Program (WASP) - Knut and Alice Wallenberg Foundation

    Available from: 2019-05-02 Created: 2019-05-02 Last updated: 2019-07-03Bibliographically approved
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    Optimal Braking Patterns and Forces in Autonomous Safety-Critical Maneuvers
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  • 143.
    Fors, Victor
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Gao, Yangyan
    University of Lincoln.
    Olofsson, Björn
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Gordon, Timothy
    University of Lincoln.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Real-Time Minimum-Time Lane Change Using the Modified Hamiltonian Algorithm2020In: Advances in Dynamics of Vehicles on Roads and Tracks / [ed] Matthijs Klomp, Fredrik Bruzelius, Jens Nielsen, Angela Hillemyr, 2020, p. 1457-1465Conference paper (Refereed)
    Abstract [en]

    A minimum-time lane change maneuver is executed under friction-limited conditions using (1) the Modified Hamiltonian Algorithm (MHA) suitable for real-time control and (2) numerical optimization for comparison. A key variable is the switching time of the acceleration reference in MHA. Considering that MHA is based on an approximate vehicle model to target real-time control, it cannot exactly match the ideal reference as obtained from offline optimization; this paper shows that incorporation of a limited-jerk condition successfully predicts the switching time and that the desired lane position is reached in near minimum time.

  • 144.
    Fors, Victor
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Olofsson, Björn
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Attainable force volumes of optimal autonomous at-the-limit vehicle manoeuvres2019In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, p. 1-22Article in journal (Refereed)
    Abstract [en]

    With new developments in sensor technology, a new generation of vehicle dynamics controllers is developing, where the braking and steering strategies use more information, e.g. knowledge of road borders. The basis for vehicle-safety systems is how the forces from tyre–road interaction is vectored to achieve optimal total force and moment on the vehicle. To study this, the concept of attainable forces previously proposed in literature is adopted, and here a new visualisation technique is devised. It combines the novel concept of attainable force volumes with an interpretation of how the optimal solution develops within this volume. A specific finding is that for lane-keeping it is important to maximise the force in a certain direction, rather than to control the direction of the force vector, even though these two strategies are equivalent for the friction-limited particle model previously used in some literature for lane-keeping control design. More specifically, it is shown that the optimal behaviour develops on the boundary surface of the attainable force volume. Applied to lane-keeping control, this observation indicates a set of control principles similar to those analytically obtained for friction-limited particle models in earlier research, but result in vehicle behaviour close to the globally optimal solution also for more complex models and scenarios.

    Download full text (pdf)
    Attainable force volumes of optimal autonomous at-the-limit vehicle manoeuvres
  • 145.
    Fors, Victor
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Olofsson, Björn
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Formulation and interpretation of optimal braking and steering patterns towards autonomous safety-critical manoeuvres2019In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 57, no 8, p. 1206-1223Article in journal (Refereed)
    Abstract [en]

    Stability control of a vehicle in autonomous safety-critical at-the-limit manoeuvres is analysed from the perspective of lane keeping or lane changing, rather than that of yaw control as in traditional ESC systems. An optimal control formulation is developed, where the optimisation criterion is a linear combination of the initial and final velocity of the manoeuvre. Varying the interpolation parameter in this formulation turns out to result in an interesting family of optimal braking and steering patterns in stabilising manoeuvres. The two different strategies of optimal lane-keeping control and optimal yaw control are shown to be embedded in the formulation and result from the boundary values of the parameter. The results provide new insights and have the potential to be used for future safety systems that adapt the level of braking to the situation at hand, which is demonstrated through examples of how to exploit theresults.

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    Formulation and interpretation of optimal braking and steering patterns towards autonomous safety-critical manoeuvres
  • 146.
    Fors, Victor
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Olofsson, Björn
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Formulation and Interpretation of Optimal Braking Patterns in Autonomous Lane-Keeping Maneuvers2017Conference paper (Refereed)
    Abstract [en]

    The two perspectives of autonomous driving and new active safety in vehicles are complementary, and both hold promise to reduce the number of accidents and associated severe or fatal injuries. They both coincide in the recent interest in finding alternatives to traditional yaw-control systems that can utilize the full potential of the vehicle. By considering the control problem as that of lane-keeping, also at high speed and at-the-limit of tire friction, rather than that of yaw control, leads to the possibility of optimization-based active-braking systems with better performance than those existing today. Here, we investigate the optimal braking patterns in completely autonomous lane-keeping maneuvers resulting from a formulation where the optimization criterion used is an interpolation between the initial and final velocities of the maneuver. Varying the interpolation parameter, i.e., the relative weight between the initial and final velocity, results in different vehicle behavior. The analysis of these behaviors provides several new insights into stabilizing braking patterns for vehicles in at-the-limit maneuvers. Specifically, it is to be noted that the benefits of a lane-keeping strategy are immediate, both in terms of the maximum possible initial velocity and the velocity reduction. The formulation embeds the traditional yaw control and optimal lane-keeping as the end-point values of the interpolation parameter, and adds a continuous family of behaviors in between. This gives a new perspective for investigating the relation between traditional yaw control and optimal lane-keeping for autonomous vehicles.

  • 147.
    Fors, Victor
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Olofsson, Björn
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Slip-Angle Feedback Control for Autonomous Safety-Critical Maneuvers At-the-Limit of Friction2018In: Proceedings of the 14th International Symposium on Advanced Vehicle Control (AVEC’ 18), 2018Conference paper (Refereed)
    Abstract [en]

    From the basis of optimal control, a closed-loop controller for autonomous vehicle maneuvers at-the-limit of friction is developed.The controller exploits that the optimal solution tends to be close to the friction limit of the tires.This observation allows for simplifications that enable the use of a proportional feedback control in the control loop,which provides a smooth trajectory promising for realization in an actual control system.The controller is in comparison with an open-loop numerical optimal control solution shown to exhibit promising performance at low computational cost in a challenging turn scenario.

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    Slip-Angle Feedback Control for Autonomous Safety-Critical Maneuvers At-the-Limit of Friction
  • 148.
    Fors, Victor
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Olofsson, Björn
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Nielsen, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Yaw-Moment Control At-the-Limit of Friction Using Individual Front-Wheel Steering and Four-Wheel Braking2019Conference paper (Refereed)
    Abstract [en]

    A simplified combined-slip model that only considers the extreme case at the friction limit is suggested and used in a closed-loop controller for autonomous vehicle handling in at-the-limit maneuvers. In the development of the controller it is assumed that the front wheels are individually steered, but it is demonstrated in a left-hand turn scenario that with a simple adaptation, the method is still applicable for a vehicle with equal front-wheel angles.

  • 149.
    Frisk, Erik
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Efficient Elimination Orders for the Elimination Problem in Diagnosis2003Report (Other academic)
    Abstract [en]

    A consistency relation is a constraint on the time evolution of known variables (and their time derivatives) that is fulfilled if the known variables are consistent with a model. Such relations are useful in diagnosis and can be derived using elimination theory. Unfortunately, even apparently small elimination problems proves impossible to compute on standard computers. An approach to lessen the computational burden is to divide the complete elimination problem into a set of smaller elimination problems. This is done by analysing the structure of the model equations using graph theoretical algorithms from the field of sparse factorization of symmetric matrices. The algorithms are implemented in Mathematica and exemplified on a fluid-flow system where the original elimination problem does not terminate. Applying the proposed algorithms give an elimination strategy that terminates with a solution in just a few seconds.

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    Efficient Elimination Orders for the Elimination Problem in Diagnosis
  • 150.
    Frisk, Erik
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Model-based fault diagnosis applied to an SI-Engine1996Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A diagnosis procedure is an algorithm to detect and locate (isolate) faulty components in a dynamic process. In 1994 the California Air Resource Board released a regulation, called OBD II, demanding a thorough diagnosis system on board automotive vehicles. These legislative demands indicate that diagnosis will become increasingly important for automotive engines in the next few years.

    To achieve diagnosis, redundancy has to be included in the system. This redundancy can be either hardware redundancy or analytical redundancy. Hardware redundancy, e.g. an extra sensor or extra actuator, can be space consuming or expensive. Methods based on analytical redundancy need no extra hardware, the redundancy here is generated from a process model instead. In this thesis, approaches utilizing analytical redundancy is examined.

    A literature study is made, surveying a number of approaches to the diagnosis problem. Three approaches, based on both linear and non-linear models, are selected and further analyzed and complete design examples are performed. A mathematical model of an SI-engine is derived to enable simulations of the designed methods.

    Download full text (pdf)
    Model-based fault diagnosis applied to an SI-Engine
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