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  • 1.
    Andersson, Per
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik.
    Modeling and Architecture Examples of Model Based Engine Control1999Konferensbidrag (Refereegranskat)
  • 2.
    Anistratov, Pavel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Efficient Motion Planning for Autonomous Vehicle Maneuvers Using Duality-Based Decomposition2019Ingår i: Proceedings of the 9th IFAC International Symposium on Advances in Automotive Control, Orleans, June 23-27, 2019, 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    A method to decompose a motion-planning problem into several segments is presented. It is based on a modification of the original problem, such that certain variables at the splitting points are considered to be precomputed and thus fixedand the remaining variables are obtained by performing Lagrange relaxation. The resulting dual problem is split into several subproblems, allowing parallel computation. The method is formalized as a computational algorithm and evaluated in a safety critical double lane-change situation. The resulting maneuver has close-to-optimal behavior and, for certain initialization strategies, it is obtained in shorter computational time compared to computing the full maneuver in one step.

  • 3.
    Anistratov, Pavel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Lane-Deviation Penalty for Autonomous Avoidance Maneuvers2018Ingår i: Proceedings of the 14th International Symposium on Advanced Vehicle Control, Beijing, July 16-20, 2018, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    A formulation of an offline motion-planning method for avoidance maneuvers based on a lane-deviation penalty function is proposed,which aims to decrease the risk of a collision by minimizing the time when a vehicle is outside of its own driving lane in the case ofavoidance maneuvers. The penalty function is based on a logistic function. The method is illustrated by computing optimal maneuversfor a double lane-change scenario. The results are compared with minimum-time maneuvers and squared-error norm maneuvers. Thecomparison shows that the use of the considered penalty function requires fewer constraints and that the vehicle stays less time in theopposing lane. The similarity between the obtained trajectories for different problem configurations was noticed. This property couldbe used in the future for predicting an intermediate trajectory online from a sparse data set of maneuvers.

  • 4.
    Anistratov, Pavel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Segmentation and Merging of Autonomous At-the-Limit Maneuversfor Ground Vehicles2018Ingår i: Proceedings of the 14th International Symposium on Advanced Vehicle Control, Beijing, July 16-20, 2018, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    To decrease the complexity of motion-planning optimizations, a segmentation and merging strategy for maneuvers is proposed. Maneuvers that are at-the-limit of friction are of special interest since they appear in many critical situations. The segmentation pointsare used to set constraints for several smaller optimizations for parts of the full maneuver, which later are merged and compared withoptimizations of the full maneuver. The technique is illustrated for a double lane-change maneuver.

  • 5.
    Berntorp, Karl
    et al.
    Lund University, Sweden.
    Olofsson, Bjorn
    Lund University, Sweden.
    Lundahl, Kristoffer
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Models and methodology for optimal trajectory generation in safety-critical road-vehicle manoeuvres2014Ingår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 52, nr 10, s. 1304-1332Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is currently a strongly growing interest in obtaining optimal control solutions for vehicle manoeuvres, both in order to understand optimal vehicle behaviour and, perhaps more importantly, to devise improved safety systems, either by direct deployment of the solutions or by including mimicked driving techniques of professional drivers. However, it is non-trivial to find the right combination of models, optimisation criteria, and optimisation tools to get useful results for the above purposes. Here, a platform for investigation of these aspects is developed based on a state-of-the-art optimisation tool together with adoption of existing vehicle chassis and tyre models. A minimum-time optimisation criterion is chosen for the purpose of gaining an insight into at-the-limit manoeuvres, with the overall aim of finding improved fundamental principles for future active safety systems. The proposed method to trajectory generation is evaluated in time-manoeuvres using vehicle models established in the literature. We determine the optimal control solutions for three manoeuvres using tyre and chassis models of different complexities. The results are extensively analysed and discussed. Our main conclusion is that the tyre model has a fundamental influence on the resulting control inputs. Also, for some combinations of chassis and tyre models, inherently different behaviour is obtained. However, certain variables important in vehicle safety-systems, such as the yaw moment and the body-slip angle, are similar for several of the considered model configurations in aggressive manoeuvring situations.

  • 6.
    Berntorp, Karl
    et al.
    Department of Automatic Control, Lund University, Lund, Sweden.
    Olofsson, Björn
    Department of Automatic Control, Lund University, Lund, Sweden.
    Lundahl, Kristoffer
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Bernhardsson, Bo
    Department of Automatic Control, Lund University, Lund, Sweden.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Models and Methodology for Optimal Vehicle Maneuvers Applied to a Hairpin Turn2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    There is currently a strongly growing interest in obtaining optimal control solutions for vehicle maneuvers, both in order to understand optimal vehicle behavior and to devise improved safety systems, either by direct deployment of the solutions or by including mimicked driving techniques of professional drivers. However, it is nontrivial to find the right mix of models, formulations, and optimization tools to get useful results for the above purposes. Here, a platform is developed based on a stateof-the-art optimization tool together with adoption of existing vehicle models, where especially the tire models are in focus. A minimum-time formulation is chosen to the purpose of gaining insight in at-the-limit maneuvers, with the overall aim of possibly finding improved principles for future active safety systems. We present optimal maneuvers for different tire models with a common vehicle motion model, and the results are analyzed and discussed. Our main result is that a few-state singletrack model combined with different tire models is able to replicate the behavior of experienced drivers. Further, we show that the different tire models give quantitatively different behavior in the optimal control of the vehicle in the maneuver.

  • 7.
    Biteus, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Cedersund, Gunnar
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Krysander, Mattias
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Improving Airplane Safety by Incorporating Diagnosis into Existing Safety Practice2004Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Safety has always been at premium in airfare. There is a long history of systematic work in the field, and current practice has established a high degree of safety that has resulted in so low failure numbers that the public finds confidence in the process of air worthiness certification. However, the design and development process of airplanes to achieve this is costly and may be even more so since modern airplanes become more and more complex. Furthermore, recent trends towards Unmanned Aerial Vehicles (UAV) are likely to require even more efforts and costs, to fulfill the increased safety requirements. Therefore it is interesting to investigate modern techniques that promises to improve safety at reduced costs. One such technique is diagnosis. Diagnosis in general is a term that includes several research and application fields. Examples of such fields, that are technology drivers, are the fields of supervision both on-line (on-board) and off-line (on ground), operator support that evolved from the Harrisburg accident, and law based emission diagnostics regulation e.g. as stipulated by California Air Resource Board (CARB).

    The current work is an investigation in the cross field between safety assessment and diagnosis techniques. The first step was to root the work in existing safety practice. This means that the Swedish defense procedure has been adopted as described in H SystSäk E. It is a safety framework that uses fault tree analysis and failure mode effect analysis as important tools. Thereafter some flight applications were investigated together with Saab specialists to capture and formulate some aspects that are non-trivial to cast in the existing safety framework. Examples of such aspects found are for instance related to performance requirements in different operational model. A principle case study was then formulated using laboratory equipment, with the aim to capture some of the identified aspects in the problem formulation. A complete process for safety analysis was then completed along the lines of H SystSäk E including all meetings and documents required therein. Several observations were done during this work, but the overall conclusion so far is that the effect of introducing diagnosis algorithms can be handled in the safety analysis, and, yes, that there is a promise that diagnosis algorithms can improve safety in a structured quantitative way by lowering the contribution to the total failure risk from the subsystem being diagnosed.

  • 8.
    Edlund, Simon
    et al.
    Nokia Svenska AB, Linköping, SWEDEN.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Pettersson, Magnus
    SCANIA AB, Södertälje. SWEDEN.
    A Real-Time Platform for Collaboration Projects in Power Train Modeling and Control1999Konferensbidrag (Refereegranskat)
    Abstract [en]

    The requirements on research and development in automotive control are growing fast, and therefore convenient and efficient ways to make prototype experiments and demonstrations are sought for. Collaboration projects put some additional constraints on the experimental system used due to issues of safety and secrecy. These requirements are outlined, a real-time platform is developed, and experiences from some collaboration projects between industry and academia are discussed.

  • 9.
    Eriksson, Lars
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Ionization Current Interpretation for Ignition Control in Internal Combustion Engines1997Ingår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 5, nr 8, s. 1107-1113Artikel i tidskrift (Refereegranskat)
    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.

  • 10.
    Eriksson, Lars
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Modeling and control of engines and drivelines2014Bok (Refereegranskat)
  • 11.
    Eriksson, Lars
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Towards On-Board Engine Calibration with Feedback Control Incorporating Combustion Models and Ion-sense2003Ingår i: Automatisierungstechnik, ISSN 0178-2312, Vol. 51, nr 5, s. 204-212Artikel i tidskrift (Refereegranskat)
    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.

  • 12.
    Eriksson, Lars
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik.
    Brugard, J.
    Bergstrom, J.
    Pettersson, F.
    Andersson, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Modeling of a turbocharged SI engine2002Ingår i: Annual Reviews in Control, ISSN 1367-5788, E-ISSN 1872-9088, Vol. 26 I, s. 129-137Artikel i tidskrift (Refereegranskat)
    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.

  • 13.
    Eriksson, Lars
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik.
    Brugård, Jan
    Bergström, Johan
    Pettersson, Fredrik
    Andersson, Per
    Linköpings universitet, Institutionen för systemteknik.
    Modeling and Simulation of a Turbo Charged SI Engine2001Konferensbidrag (Refereegranskat)
  • 14.
    Eriksson, Lars
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik.
    Brugård, Jan
    Bergström, Johan
    Pettersson, Fredrik
    Andersson, Per
    Linköpings universitet, Institutionen för systemteknik.
    Modeling and Simulation of a Turbo Charged SI Engine2002Ingår i: Annual Reviews in Control, ISSN 1367-5788, E-ISSN 1872-9088, Vol. 26, s. 129-137Artikel i tidskrift (Refereegranskat)
  • 15.
    Eriksson, Lars
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Glavenius, Mikael
    Mecel AB.
    Closed Loop Ignition Control by Ionization Current Interpretation1998Ingår i: SAE technical paper series, ISSN 0148-7191, Vol. 106, nr SAE Technical Paper 970854, s. 1216-1223Artikel i tidskrift (Refereegranskat)
    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.

  • 16.
    Eriksson, Lars
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nytomt, Jan
    Mecel AB.
    Ignition Control by Ionization Current Interpretation1997Ingår i: SAE technical paper series, ISSN 0148-7191, Vol. 105, nr SAE Technical Paper 960045, s. 165-171Artikel i tidskrift (Refereegranskat)
    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.

  • 17.
    Fors, Victor
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Attainable force volumes of optimal autonomous at-the-limit vehicle manoeuvres2019Ingår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, s. 1-22Artikel i tidskrift (Refereegranskat)
    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.

  • 18.
    Fors, Victor
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Formulation and interpretation of optimal braking and steering patterns towards autonomous safety-critical manoeuvres2018Ingår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 57, nr 8, s. 1206-1223Artikel i tidskrift (Refereegranskat)
    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.

  • 19.
    Fors, Victor
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Formulation and Interpretation of Optimal Braking Patterns in Autonomous Lane-Keeping Maneuvers2017Konferensbidrag (Refereegranskat)
    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.

  • 20.
    Fors, Victor
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Slip-Angle Feedback Control for Autonomous Safety-Critical Maneuvers At-the-Limit of Friction2018Ingår i: Proceedings of the 14th International Symposium on Advanced Vehicle Control (AVEC’ 18), 2018Konferensbidrag (Refereegranskat)
    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.

  • 21.
    Fors, Victor
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Yaw-Moment Control At-the-Limit of Friction Using Individual Front-Wheel Steering and Four-Wheel Braking2019Konferensbidrag (Refereegranskat)
    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.

  • 22.
    Frisk, Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Robust Residual Generation for Diagnosis Including a Reference Model for Residual Behavior1999Ingår i: IFAC World Congress,1999, 1999Konferensbidrag (Refereegranskat)
  • 23.
    Frisk, Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Robust Residual Generation for Diagnosis Including a Reference Model for Residual Behavior2006Ingår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 42, nr 3, s. 437-445Artikel i tidskrift (Refereegranskat)
  • 24.
    Frisk, Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nyberg, Mattias
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    FDI with adaptive residual generation applied to a DC-servo1997Ingår i: IFAC Safeprocess,1997, Hull: IFAC , 1997Konferensbidrag (Refereegranskat)
  • 25.
    Fröberg, Anders
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Hellström, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Explicit Fuel Optimal Speed Profiles for Heavy Trucks on a Set of Topograhic Road Profiles2006Ingår i: Electronic Engine Controls, SAE World Congress 2006, 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    The problem addressed is how to drive a heavy truck over various road topographies such that the fuel consumption is minimized. Using a realistic model of a truck powertrain, an optimization problem for minimization of fuel consumption is formulated. Through the solutions of this problem optimal speed profiles are found. An advantage here is that explicit analytical solutions can be found, and this is done for a few constructed test roads. The test roads are constructed to be easy enough to enable analytical solutions but still capture the important properties of real roads. In this way the obtained solutions provide explanations to some behavior obtained by ourselves and others using more elaborate modelling and numeric optimization like dynamic programming.

    The results show that for level road and in small gradients the optimal solution is to drive with constant speed. For large gradients in downhill slopes it is optimal to utilize the kinetic energy of the vehicle to accelerate in order to gain speed. This speed increase is used to lower the speed on other road sections such that the total average speed is kept. Taking account for limitations of top speed the optimal speed profile changes to a strategy that minimizes brake usage. This is done by, e.g., slowing down before steep down gradients where the truck will accelerate even though the engine does not produce any torque.

  • 26.
    Fröberg, Anders
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Hellström, Erik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Explicit Fuel Optimal Speed Profiles for Heavy Trucks on a Set of Topographic Road Profiles2006Ingår i: SAE World Congress 2006,2006, SAE , 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

     The problem addressed is how to drive a heavy truck over various road topographies such that the fuel consumption is minimized. Using a realistic model of a truck powertrain, an optimization problem for minimization of fuel consumption is formulated. Through the solutions of this problem optimal speed profiles are found. An advantage here is that explicit analytical solutions can be found, and this is done for a few constructed test roads. The test roads are constructed to be easy enough to enable analytical solutions but still capture the important properties of real roads. In this way the obtained solutions provide explanations to some behaviour obtained by ourselves and others using more elaborate modeling and numeric optimization like dynamic programming. The results show that for level road and in small gradients the optimal solution is to drive with constant speed. For large gradients in downhill slopes it is optimal to utilize the kinetic energy of the vehicle to accelerate in order to gain speed. This speed increase is used to lower the speed on other road sections such that the total average speed is kept. Taking account for limitations of top speed the optimal speed profile changes to a strategy that minimizes brake usage. This is done by e.g. slowing down before steep down gradients were the truck will accelerate even though the engine does not produce any torque.

  • 27.
    Fröberg, Anders
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik.
    A Method to Extend Inverse Dynamic Simulation of Powertrains with Additional Dynamics2004Ingår i: 1st IFAC symposium on Advances in Automotive Control,2004, IFAC , 2004Konferensbidrag (Refereegranskat)
  • 28.
    Fröberg, Anders
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik.
    Dynamic Vehicle Simulation -Forward, Inverse and New Mixed Possibilites for Optimized Design and Control2004Ingår i: SAE World Congress,2004, SAE , 2004Konferensbidrag (Refereegranskat)
  • 29.
    Fröberg, Anders
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Efficient Drive Cycle Simulation2008Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 57, nr 3, s. 1442-1453Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Drive cycle simulations of longitudinal vehicle models are important aids for the design and analysis of power trains, and tools currently on the market mainly use two different methods for such simulations: the forward dynamic and quasi-static inverse simulations. Here, a known theory for the stable inversion of nonlinear systems is used to combine the fast simulation times of the quasi-static inverse simulation with the ability of the forward dynamic simulation to include transient dynamics. The stable inversion technique and a new implicit driver model together form a new concept: inverse dynamic simulation. This technique is demonstrated to be feasible for vehicle propulsion simulation and specifically for three power train applications that include important dynamics that cannot be handled using quasi-static inverse simulation. The extensions are engine dynamics, driveline dynamics, and gas flow dynamics for diesel engines, which are also selected to represent important properties, such as zero dynamics, resonances, and nonminimum-phase systems. It is shown that inverse dynamic simulation is easy to set up, gives short simulation times, and gives consistent results for design space exploration. This makes inverse dynamic simulation a suitable method to use for drive cycle simulation, particularly in situations requiring many simulations, such as optimization over design space, power train configuration optimization, or the development of power train control strategies.

  • 30.
    Fröberg, Anders
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Optimal fuel and gear ratio control for heavy trucks with piece wise affine engine characteristics2007Ingår i: Fifth IFAC symposium on advances in automotive control,2007, IFAC: IFAC , 2007, s. 335-Konferensbidrag (Refereegranskat)
  • 31.
    Fröberg, Anders
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Hedström, Lars-Gunnar
    Scania, Södertälje, Sweden.
    Pettersson, Magnus
    Scania, Södertälje, Sweden.
    Controlling Gear Engagement and disengagement on heavy trucks for minimization of fuel consumption2005Ingår i: Proceedings of the 16th IFAC World Congress, 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    There is a potential to save fuel for heavy trucks by storing kineticenergy in the vehicle when driving downhill, because the speed adds kinetic energyto the vehicle which can be used after the downhill slope to propell the vehicle.This behavior can be even more utilized by disengaging the gear to reduce thefriction in the driveline and thus increase the speed even more. Two differentcontrol strategies to choose when to disengage the gear is presented: One schemethat uses instantaneous inclination and one predictive control scheme that useslook ahead information of the road topology. Simulation results show that geardisengagement in downhills can reduce the fuel consumption about 3%.

  • 32.
    Gustafsson, Fredrik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Frisk, Erik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Krysander, Mattias
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    On Threshold Optimization in Fault Tolerant Systems2008Ingår i: Proceedings of the 17th IFAC World Congress, 2008, s. 7883-7888Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fault tolerant systems are considered, where a nominal system is monitored by a fault detection algorithm, and the nominal system is switched to a backup system in case of a detected fault. Conventional fault detection is in the classical setting a trade-off between detection probability and false alarm probability. For the considered fault tolerant system, a system failure occurs either when the nominal system gets a fault that is not detected, or when the fault detector signals an alarm and the backup system breaks down. This means that the trade-off for threshold setting is different and depends on the overall conditions, and the characterization and understanding of this trade-off is important. It is shown that the probability of system failure can be expressed in a general form based on the probability of false alarm and detection power, and based on this form the influence ratio is introduced. This ratio includes all information about the supervised system and the backup system that is needed for the threshold optimization problem. It is shown that the influence ratio has a geometrical interpretation as the gradient of the receiver operating characteristics (ROC) curve at the optimal point, and furthermore, it is the threshold for the optimal test quantity in important cases.

  • 33.
    Hellström, Erik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Fröberg, Anders
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    A Real-Time Fuel-Optimal Cruise Controller for Heavy Trucks using Road Topography Information2006Ingår i: SAE World Congress, 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    New and exciting possibilities in vehicle control are revealed by the consideration of topography, for example through the combination of GPS and three-dimensional road maps. How information about future road slopes can be utilized in a heavy truck is explored. The aim is set at reducing the fuel consumption over a route without increasing the total travel time.

    A model predictive control (MPC) scheme is used to control the longitudinal behavior of the vehicle, which entails determining accelerator and brake levels and also which gear to engage. The optimization is accomplished through discrete dynamic programming. A cost function that weighs fuel use, negative deviations from the reference velocity, velocity changes, gear shifts and brake use is used to define the optimization criterion.

    Computer simulations back and forth on 127 km of a typical highway route in Sweden show that the fuel consumption in a heavy truck can be reduced 2.5% with a negligible change in travel time.

  • 34.
    Hellström, Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Ivarsson, Maria
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Åslund, Jan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Look-ahead Control for Heavy Trucks to minimize Trip Time and Fuel Consumption2007Ingår i: Fifth IFAC Symposium on Advances in Automotive Control,2007, 2007Konferensbidrag (Refereegranskat)
  • 35.
    Hellström, Erik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Ivarsson, Maria
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Look-ahead control for heavy trucks to minimize trip time and fuel consumption2009Ingår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 17, nr 2, s. 245-254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The scenario studied is a drive mission for a heavy diesel truck. With aid of an on board road slope database in combination with a GPS unit, information about the road geometry ahead is extracted. This look-ahead information is used in an optimization of the velocity trajectory with respect to a criterion formulation that weighs trip time and fuel consumption. A dynamic programming algorithm is devised and used in a predictive control scheme by constantly feeding the conventional cruise controller with new set points. The algorithm is evaluated with a real truck on a highway, and the experimental results show that the fuel consumption is significantly reduced.

  • 36.
    Hellström, Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Åslund, Jan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik.
    Design of a Well-behaved Algorithm for On-board Look-ahead Control2008Ingår i: IFAC World Congress,2008, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    A look-ahead controller is developed for a heavy diesel truck that utilizes information about the road topography ahead of the vehicle when the route is known. A dedicated prediction model is formulated where special attention is given to properly include gear shifting. The nature of the problem is analyzed for the purpose of optimization, and a well performing dynamic programming algorithm is tailored. A key step for satisfactory solutions with a sufficiently low computational effort is to avoid numerical problems. The focus here is the choice of discretization method, and it turns out that a basic analysis give decisive insight into the interplay between the criterion and the discretization errors. The resulting algorithm is demonstrated to perform well in real on-line tests on a highway.

  • 37.
    Hellström, Erik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Design of an efficient algorithm for fuel-optimal look-ahead control2010Ingår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 18, nr 11, s. 1318-1327Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fuel-optimal control algorithm is developed for a heavy diesel truck that utilizes information about the road topography ahead of the vehicle when the route is known. A prediction model is formulated where special attention is given to properly include gear shifting. The aim is an algorithm with sufficiently low computational complexity. To this end, a dynamic programming algorithm is tailored, and complexity and numerical errors are analyzed. It is shown that it is beneficial to formulate the problem in terms of kinetic energy in order to avoid oscillating solutions and to reduce linear interpolation errors. A residual cost is derived from engine and driveline characteristics. The result is an on-board controller for an optimal velocity profile and gear selection.

  • 38.
    Hellström, Erik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Horizon length and fuel equivalents for fuel-optimal look-ahead control2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recent studies from several authors show that it is possible to lower the fuel consumption for heavy trucks by utilizing information about the road topography ahead of the vehicle. The approach in these studies is receding horizon control where horizon length and residual cost are main topics. To approach these topics, fuel equivalents previously introduced based on physical intuition are given a mathematical interpretation in terms of Lagrange multipliers. Measures for the suboptimality, caused by the truncated horizon and the residual cost approximation, are defined and evaluated for different routes and parameters.

  • 39.
    Hellström, Erik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Management of kinetic and electric energy in heavy trucks2010Ingår i: Transmission and Driveline, 2010, SAE International , 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Hybridization and velocity management are two important techniques for energy efficiency that mainly have been treated separately. Here they are put in a common framework that from the hybridization perspective can be seen as an extension of the equivalence factor idea in the well known strategy ECMS. From the perspective of look-ahead control, the extension is that energy can be stored not only in kinetic energy, but also electrically. The key idea is to introduce more equivalence factors in a way that enables efficient computations, but also so that the equivalence factors have a physical interpretation. The latter fact makes it easy to formulate a good residual cost to be used at the end of the look-ahead horizon. The formulation has different possible uses, but it is here applied on an evaluation of the size of the electrical system. Previous such studies, for e.g. ECMS, have typically used a driving cycle, i.e. a fixed velocity profile, but here the extra freedom to choose an optimal driving pattern is added.

  • 40.
    Ivarsson, Maria
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Impacts of AMT Gear-Shifting on Fuel Optimal Look Ahead Control2009Rapport (Övrigt vetenskapligt)
    Abstract [en]

    A fuel optimal gear shift control has been studied, when look ahead information is available, and the impact of the automated manual transmission (AMT) gear-shifting process is analayzed. For a standard discrete heavy truck transmission, answers are found on when to shift gears, prior to or when in an uphill slope. The gear-shifting process of a standard AMT is modeled, not considering the comfort details, in order to capture the fuel and time aspects of the gear shift. A numerical optimization is performed by dynamic programming, minimizing fuel consumption and time by controlling fuel injection and gear. Since a standard AMT does not have look ahead information, it sometimes gears down unnecessarily and thus gives a significantly higher fuel consumption compared to the optimal control. However, if gearing down is inevitable, the AMT gear-shifting strategy, based on engine thresholds, is a well-functioning gear control so that the optimal control only gives marginal additional savings. To attain the possible fuel reductions it is shown that the reduced propulsion of an AMT gear-shifting process, and the resulting vehicle retardation, must be considered. The point of shifting gears must be chosen to ensure an adequate engine speed in order to get a sufficient engine power after the gear shift, even as the truck is decelerated during gear shift.

  • 41.
    Ivarsson, Maria
    et al.
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Look Ahead Control - Consequences of a Non-Linear Fuel Map on Truck Fuel Consumption2008Ingår i: The 17th IFAC World Congress, 2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Consequences of non-linearities in specific fuel consumption, sfc, of a heavy truck combustion engine are studied with focus on so small road gradients that constant speed is optimal if the engine torque has an affine relation to fueling. A quasi-static analysis gives valuable insights into the intrinsic properties of minimization of fuel consumption. Two objective functions are shown to give different optimal velocity trajectories on a constant road gradient, when the non-linearity in sfc is significant, a notation which is quantified. For a significant non-linearity, when a constraint is set to keep a final time, switching between two characteristic speeds is optimal. Alternatively, if consumed time, in addition to fuel consumption, is part of the objective function, then keeping to one constant speed is optimal also for significant non-linearities. However, the different optimal solutions still show similarities, since for a certain significant non-linearity a specific speed range determined by the characteristic velocities is shown to be unobtainable for both optimality criteria. Similar results are obtained for a full dynamic model including a realistic fuel map and other realistic constraints.

  • 42.
    Ivarsson, Maria
    et al.
    Scania CV AB.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Look-ahead control – consequences of a non-linear fuel map on truck fuel consumption2009Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 223, nr 10, s. 1223-1238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Consequences of non-linearities in specific fuel consumption (SFC) of a heavy truck combustion engine are studied with focus on such small road gradients that a constant speed is optimal if the engine torque has an affine relation to fuelling. A quasi-static analysis gives valuable insights into the intrinsic properties of minimization of fuel consumption. Two objective functions are shown to give different optimal velocity trajectories on a constant road gradient, when the non-linearity in SFC is significant, a notation which is quantified. For a significant non-linearity, when a constraint is set to keep a final time, switching between twocharacteristic speeds is optimal. Alternatively, if consumed time, in addition to fuel consumption, is part of the objective function, then keeping to one constant speed is optimal also for significant non-linearities. However, the different optimal solutions still show similarities, since for a certain significant non-linearity a specific speed range determined by the characteristic velocities is shown to be unobtainable for both optimality criteria. Similarresults are obtained for a full dynamic model including a realistic fuel map and other realistic constraints.

  • 43.
    Kiencke, U.
    et al.
    University of Karlsruhe, Germany.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik.
    Sutton, R.
    University of Plymouth, United Kingdom.
    Schilling, K.
    University of Würzburg, Germany.
    Papageorgiou, M.
    Technical University of Crete, Greece.
    Asama, H.
    University of Tokyo, Japan.
    The impact of automatic control on recent developments in transportation and vehicle systems2006Ingår i: Annual Reviews in Control, ISSN 1367-5788, E-ISSN 1872-9088, Vol. 30, nr 1, s. 81-89Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Throughout the field of transportation and vehicle systems control is gaining importance. This paper focuses on the current key problems engineers in this field are facing and highlights some major recent accomplishments. The driving forces behind the increasing use of control are the rising need for transportation services and the demand for a higher safety level. While each domain takes specific approach to deal with these demands, a general trend towards automatic co-pilots or even autopilots is visible. In the automotive domain, this is aided by the design of drive by wire systems. In other fields like marine or aerospace systems, the focus of research is on the swarming behavior of multiple vessels. New sensors and networking will also enable more efficient traffic flow control which will allow for a better use of the resource network capacity. Another trend in the vehicle systems sector is the modeling of nonlinear system behavior which is starting to replace look-up tables in real time systems. A forecast on future trends is given at the end of the paper. © 2006 Elsevier Ltd. All rights reserved.

  • 44.
    Klein, Inger
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Svante
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Framstående utbildningsmiljö - Hur blir man det?2008Ingår i: Nätverket Ingenjörsutbildningarnas Utvecklingskonferens 2008, 2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [sv]

    Studierektorsområdet Reglersystem vid LiTH (Tekniska Högskolan vid Linköpings universitet) tilldelades 2007 utmärkelsen Framstående Utbildningsmiljö av Högskoleverket. Utmärkelsen gavs till sammanlagt fem utbildningsmiljöer, varav två är verksamma inom ingenjörsutbildning. I detta bidrag avser vi att redogöra för denna process och de faktorer som främst bidrog till att området Reglersystem fick denna utmärkelse. De faktorer som lyfts fram som centrala för att åstadkomma en god utbildningskvalité är framför allt att ha tydliga mål för utbildningen, en gedigen ämnesmässig grund, en väl fungerande organisation och positiv attityd bland alla medverkande samt former för lärande och examination som är anpassade till utbildningens mål.

  • 45.
    Koschorrek, Philipp
    et al.
    Linköpings universitet, Institutionen för systemteknik, Datorseende. Linköpings universitet, Tekniska högskolan.
    Piccini, Tommaso
    Linköpings universitet, Institutionen för systemteknik, Datorseende. Linköpings universitet, Tekniska högskolan.
    Öberg, Per
    Linköpings universitet, Institutionen för systemteknik, Datorseende. Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Felsberg, Michael
    Linköpings universitet, Institutionen för systemteknik, Datorseende. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Mester, Rudolf
    Linköpings universitet, Institutionen för systemteknik, Datorseende. Linköpings universitet, Tekniska högskolan. University of Frankfurt, Germany.
    A multi-sensor traffic scene dataset with omnidirectional video2013Ingår i: 2013 IEEE CONFERENCE ON COMPUTER VISION AND PATTERN RECOGNITION WORKSHOPS (CVPRW), IEEE conference proceedings, 2013, s. 727-734Konferensbidrag (Refereegranskat)
    Abstract [en]

    The development of vehicles that perceive their environment, in particular those using computer vision, indispensably requires large databases of sensor recordings obtained from real cars driven in realistic traffic situations. These datasets should be time shaped for enabling synchronization of sensor data from different sources. Furthermore, full surround environment perception requires high frame rates of synchronized omnidirectional video data to prevent information loss at any speeds.

    This paper describes an experimental setup and software environment for recording such synchronized multi-sensor data streams and storing them in a new open source format. The dataset consists of sequences recorded in various environments from a car equipped with an omnidirectional multi-camera, height sensors, an IMU, a velocity sensor, and a GPS. The software environment for reading these data sets will be provided to the public, together with a collection of long multi-sensor and multi-camera data streams stored in the developed format.

  • 46.
    Lundahl, Kristoffer
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Berntorp, Karl
    Department of Automatic Control, Lund University, Lund, Sweden.
    Olofsson, Björn
    Department of Automatic Control, Lund University, Lund, Sweden.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Studying the Influence of Roll and Pitch Dynamics in Optimal Road-Vehicle Maneuvers2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A comparative analysis shows how vehicle motion models of different complexity, capturing various characteristics, influence the solution when used in time-critical optimal maneuvering problems. Vehicle models with combinations of roll and pitch dynamics as well as load transfer are considered, ranging from a single-track model to a double-track model with roll and pitch dynamics and load transfer. The optimal maneuvers in a 90◦-turn and a double lane-change scenario are formulated as minimum-time optimization problems, and are solved using numerical optimization software. The results obtained with the different models show that variables potentially important for safety systems, such as the yaw rate, slip angle, and geometric path, are qualitatively the same. Moreover, the numeric differences are mostly within a few percent. The results also indicate that although input torques differ about 50–100 % for certain parts of the maneuver between the most and least complex model considered, the resulting vehicle motions obtained are similar, irrespective of the model. Our main conclusion isthat this enables the use of low-order models when designing the onboard optimization-based safety systems of the future.

  • 47.
    Lundahl, Kristoffer
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Implications of Path Tolerance and Path Characteristics on Critical Vehicle ManeuversManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Path planning and path following are core components in safe autonomous driving. Typically a path planner provides a path with sometolerance on how tightly the path should be followed. Based on that, and other path characteristics, for example sharpness of curves, a speed profile needs to be assigned so that the vehicle can stay within the given tolerance without going unnecessarily slow. Here, such trajectory planning is based on optimal control formulations where critical cases arises as on-the-limit solutions. Several results are obtained on required model complexity depending on path characteristics, for example quantification of required path tolerance for a simple model to be sufficient, quantification of when yaw inertia needs to be considered in more detail, and how the curvature rate of change of curvature interplays with available friction. Overall, in situations where the path planner, due to the type of vehicle operation ranging from good transport roads to more tricky maneuvering, give paths with a wide range of tolerances and characteristics, then the results provided give the basis for real-time path following with reasonably high speed.

  • 48.
    Lundahl, Kristoffer
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Lee, Chih Feng
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Analyzing Rollover Indices for Critical Truck Maneuvers2015Ingår i: SAE International Journal of Commercial Vehicles, ISSN 1946-391X, E-ISSN 1946-3928, Vol. 8, nr 1, s. 189-196Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rollover has for long been a major safety concern for trucks, and will be even more so as automated driving is envisaged to becoming a key element of future mobility. A natural way to address rollover is to extend the capabilities of current active-safety systems with a system that intervenes by steering or braking actuation when there is a risk of rollover. Assessing and predicting the rollover is usually performed using rollover indices calculated either from lateral acceleration or lateral load transfer. Since these indices are evaluated based on different physical observations it is not obvious how they can be compared or how well they reflect rollover events in different situations.

    In this paper we investigate the implication of the above mentioned rollover indices in different critical maneuvers for a heavy 8×4 twin-steer truck. The analysis is based on optimal control applied to a five degrees of freedom chassis model with individual wheel dynamics and high-fidelity tire-force modeling. Driving scenarios prone to rollover accidents are considered, with a circular-shaped turn and a slalom maneuver being studied in-depth. The optimization objective for the considered maneuvers are formulated as minimum-time and maximum entry-speed problems, both triggering critical maneuvers and forcing the vehicle to operate on the limit of its physical capabilities. The implication of the rollover indices on the optimal trajectories is investigated by constraining the optimal maneuvers with different rollover indices, thus limiting the vehicle's maneuvering envelope with respect to each rollover index. The resulting optimal trajectories constrained by different rollover indices are compared and analyzed in detail. Additionally, the conservativeness of the indices for assessing the risk of rollovers are discussed.

  • 49.
    Lundahl, Kristoffer
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Department of Automatic Control, Lund University.
    Berntorp, Karl
    Department of Automatic Control, Lund University.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Towards Lane-Keeping Electronic Stability Control for Road-Vehicles2014Ingår i: Proceedings of the 19th IFAC World Congress, 2014 / [ed] Boje, Edward, Xia, Xiaohua, International Federation of Automatic Control , 2014, Vol. 19, s. 6319-6325Konferensbidrag (Refereegranskat)
    Abstract [en]

    The emerging new idea of lane-keeping electronic stability control is investigated. In a critical situation, such as entering a road curve at excessive speed, the optimal behavior may differ from the behavior of traditional ESC, for example, by prioritizing braking over steering response. The important question that naturally arises is if this has a significant effect on safety. The main contribution here is to give a method for some first quantitative measures of this. It is based on optimal control, applied to a double-track chassis model with wheel dynamics and high-fidelity tire-force modeling. The severity of accidents grows with the square of the kinetic energy for high velocities, so using kinetic energy as a measure will at least not overestimate the usefulness of the new safety system principle. The main result is that the safety gain is significant compared to traditional approaches based on yaw rotation, for several situations and different road-condition parameters.

  • 50.
    Lundahl, Kristoffer
    et al.
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Investigating Vehicle Model Detail for Close to Limit Maneuvers Aiming at Optimal Control2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In advanced road vehicle safety systems it is imperative to have a model describing the vehicle motions and behaviors with sufficient precision. Often a model incorporating a higher level of complexity generates more accurate data, with the disadvantage of demanding additional calculation power. This study will therefore focus on investigating how models of different detail level represents the vehicle behavior, for maneuvers going from moderate to more aggressive. The characteristics in particular investigated are tire saturation, tire force lag and the effect of load transfers. A vehicle testbed has also been developed, making model validations towards experimental data available.

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