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  • 1.
    Kharrazi, Sogol
    et al.
    Linköpings universitet, Institutionen för systemteknik, Informationskodning. Linköpings universitet, Tekniska fakulteten. Swedish National Road and Transport Research Institute (VTI), Linköping, Sweden.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Generation of Mission-Based Driving Cycles Using Behavioral Models Parameterized for Different Driver Categories2023Ingår i: SAE technical paper series, ISSN 0148-7191, , s. 11Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A methodology for the generation of representative driving cycles is proposed and evaluated. The proposed method combines traffic simulation and driving behavior modeling to generate mission-based driving cycles. Extensions to the existing behavioral model in a traffic simulation tool are suggested and parameterized for different driver categories to capture the effects of road geometry and variances between drivers. The evaluation results illustrate that the developed extensions significantly improve the match between driving data and the driving cycles generated by traffic simulation. Using model extensions parameterized for different driver categories, instead of only one average driver, provides the possibility to represent different driving behaviors and further improve the realism of the resulting driving cycles.

  • 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. Lund Univ, Sweden.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Analysis and design of recovery behaviour of autonomous-vehicle avoidance manoeuvres2022Ingår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 60, nr 7, s. 2231-2254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Autonomous vehicles allow utilisation of new optimal driving approaches that increase vehicle safety by combining optimal all-wheel braking and steering even at the limit of tyre-road friction. One important case is an avoidance manoeuvre that, in previous research, for example, has been approached by different optimisation formulations. An avoidance manoeuvre is typically composed of an evasive phase avoiding an obstacle followed by a recovery phase where the vehicle returns to normal driving. Here, an analysis of the different aspects of the recovery phase is presented, and a subsequent formulation is developed in several steps based on theory and simulation of a double lane-change scenario. Each step leads to an extension of the optimisation criterion. Two key results are a theoretical redundancy analysis of wheel-torque distribution and the subsequent handling of it. The overall contribution is a general treatment of the recovery phase in an optimisation framework, and the method is successfully demonstrated for three different formulations: lane-deviation penalty, minimum time, and squared lateral-error norm.

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  • 3.
    Anistratov, Pavel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten. Chalmers Univ Technol, Sweden.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten. Lund Univ, Sweden.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Dynamics-Based Optimal Motion Planning of Multiple Lane Changes using Segmentation2022Ingår i: IFAC PAPERSONLINE, ELSEVIER , 2022, Vol. 55, nr 24, s. 233-240Konferensbidrag (Refereegranskat)
    Abstract [en]

    Avoidance maneuvers at normal driving speed or higher are demanding driving situations that force the vehicle to the limit of tire-road friction in critical situations. To study and develop control for these situations, dynamic optimization has been in growing use in research. One idea to handle such optimization computations effectively is to divide the total maneuver into a sequence of sub-maneuvers and to associate a segmented optimization problem to each sub-maneuver. Here, the alternating augmented Lagrangian method is adopted, which like many other optimization methods benefits strongly from a good initialization, and to that purpose a method with motion candidates is proposed to get an initially feasible motion. The two main contributions are, firstly, the method for computing an initially feasible motion that is found to use obstacle positions and progress of vehicle variables to its advantage, and secondly, the integration with a subsequent step with segmented optimization showing clear improvements in paths and trajectories. Overall, the combined method is able to handle driving scenarios at demanding speeds.

  • 4.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Force-Centric Perspectives on Autonomous Safety Maneuvers2022Ingår i: IFAC PAPERSONLINE, ELSEVIER , 2022, Vol. 55, nr 24Konferensbidrag (Refereegranskat)
    Abstract [en]

    Real-time avoidance maneuvers have been developed using a force-centric perspective, where the founding principles are obtained from studies of optimal maneuvers. The developed optimization framework, the different criteria used, and the obtained solutions give insight into how to control the forces on the vehicle. A highlight in this presentation is the first algorithm not needing a tire-road friction estimate.

  • 5.
    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. Department of Automatic Control, Lund University, Lund, Sweden.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Autonomous Wary Collision Avoidance2021Ingår i: IEEE Transactions on Intelligent Vehicles, ISSN 2379-8858, E-ISSN 2379-8904, Vol. 6, nr 2, s. 353-365Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Handling of critical situations is an important part in the architecture of an autonomous vehicle. A controller for autonomous collision avoidance is developed based on a wary strategy that assumes the least tireroad friction for which the maneuver is still feasible. Should the friction be greater, the controller makes use of this and performs better. The controller uses an acceleration-vector reference obtained from optimal control of a friction-limited particle, whose applicability is verified by using numerical optimization on a full vehicle model. By employing an analytical tire model of the tireroad friction limit, to determine slip references for steering and body-slip control, the result is a controller where the computation of its output is explicit and independent of the actual tire-road friction. When evaluated in real-time on a high-fidelity simulation model, the developed controller performs close to that achieved by offline numerical optimization.

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  • 6.
    Mohseni, Fatemeh
    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.
    Distributed Cooperative MPC for Autonomous Driving in Different Traffic Scenarios2021Ingår i: IEEE Transactions on Intelligent Vehicles, ISSN 2379-8858, E-ISSN 2379-8904, Vol. 6, nr 2, s. 299-309Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A cooperative control approach for autonomous vehicles is developed in order to perform different complex traffic maneuvers, e.g., double lane-switching or intersection situations. The problem is formulated as a distributed optimal control problem for a system of multiple autonomous vehicles and then solved using a nonlinear Model Predictive Control (MPC) technique, where the distributed approach is used to make the problem computationally feasible in real-time. To provide safety, a collision avoidance constraint is introduced, also in a distributed way. In the proposed method, each vehicle computes its own control inputs using estimated states of neighboring vehicles. In addition, a compatibility constraint is defined that takes collision avoidance into account but also ensures that each vehicle does not deviate significantly from what is expected by neighboring vehicles. The method allows us to construct a cost function for several different traffic scenarios. The asymptotic convergence of the system to the desired destination is proven, in the absence of uncertainty and disturbances, for a sufficiently small MPC control horizon. Simulation results show that the distributed algorithm scales well with increasing number of vehicles.

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  • 7.
    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. Lund Univ, Sweden.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Lane-deviation penalty formulation and analysis for autonomous vehicle avoidance maneuvers2021Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 235, nr 12, s. 3036-3050, artikel-id 09544070211007979Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Autonomous vehicles hold promise for increased vehicle and traffic safety, and there are several developments in the field where one example is an avoidance maneuver. There it is dangerous for the vehicle to be in the opposing lane, but it is safe to drive in the original lane again after the obstacle. To capture this basic observation, a lane-deviation penalty (LDP) objective function is devised. Based on this objective function, a formulation is developed utilizing optimal all-wheel braking and steering at the limit of road-tire friction. This method is evaluated for a double lane-change scenario by computing the resulting behavior for several interesting cases, where parameters of the emergency situation such as the initial speed of the vehicle and the size and placement of the obstacle are varied, and it performs well. A comparison with maneuvers obtained by minimum-time and other lateral-penalty objective functions shows that the use of the considered penalty function decreases the time that the vehicle spends in the opposing lane.

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  • 8.
    Fors, Victor
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Anistratov, Pavel
    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.
    Predictive Force-Centric Emergency Collision Avoidance2021Ingår i: Journal of Dynamic Systems Measurement, and Control, ISSN 0022-0434, E-ISSN 1528-9028, Vol. 143, nr 8, artikel-id 081005Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A controller for critical vehicle maneuvering is proposed that avoids obstacles and keeps the vehicle on the road while achieving heavy braking. It operates at the limit of friction and is structured in two main steps: a motion-planning step based on receding-horizon planning to obtain acceleration-vector references, and a low-level controller for following these acceleration references and transforming them into actuator commands. The controller is evaluated in a number of challenging scenarios and results in a well behaved vehicle with respect to, e.g., the steering angle, the body slip, and the path. It is also demonstrated that the controller successfully balances braking and avoidance such that it really takes advantage of the braking possibilities. Specifically, for a moving obstacle, it makes use of a widening gap to perform more braking, which is a clear advantage of the online replanning capability if the obstacle should be a moving human or animal. Finally, real-time capabilities are demonstrated. In conclusion, the controller performs well, both from a functional perspective and from a real-time perspective.

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  • 9.
    Olofsson, Björn
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Using Crash Databases to Predict Effectiveness of New Autonomous Vehicle Maneuvers for Lane-Departure Injury Reduction2021Ingår i: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 22, nr 6, s. 3479-3490Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Autonomous vehicle functions in safety-critical situations show promise in reducing the risk and saving lives in accidents compared to existing safety systems. Consequently, it is from many perspectives advantageous to be able to quantify the potential benefits of new autonomous systems for vehicle maneuvers at-the-limit of tire friction. Here, to estimate the potential in terms of saved lives and reduced degree of injuries in accidents for new, not yet existing systems, a framework has been developed by combining available historic data, in the form of crash databases, and statistical methods with comparative calculations of vehicle behavior using numerical optimization rather than simulation. The framework performs effectively, it gives interesting insights into the relation between more traditional active yaw control and optimal autonomous lane-keeping control, and it clearly demonstrates the potential of saved lives by using autonomous vehicle maneuvers.

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  • 10.
    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 manoeuvres2020Ingår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 58, nr 7, s. 1101-1122Artikel 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.

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    Attainable force volumes of optimal autonomous at-the-limit vehicle manoeuvres
  • 11.
    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.
    Burdakov, Oleg
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Autonomous-Vehicle Maneuver Planning Using Segmentation and the Alternating Augmented Lagrangian Method2020Ingår i: 21th IFAC World Congress Proceedings / [ed] Rolf Findeisen, Sandra Hirche, Klaus Janschek, Martin Mönnigmann, Elsevier, 2020, Vol. 53, s. 15558-15565Konferensbidrag (Refereegranskat)
    Abstract [en]

    Segmenting a motion-planning problem into smaller subproblems could be beneficial in terms of computational complexity. This observation is used as a basis for a new sub-maneuver decomposition approach investigated in this paper in the context of optimal evasive maneuvers for autonomous ground vehicles. The recently published alternating augmented Lagrangianmethod is adopted and leveraged on, which turns out to fit the problem formulation with several attractive properties of the solution procedure. The decomposition is based on moving the coupling constraints between the sub-maneuvers into a separate coordination problem, which is possible to solve analytically. The remaining constraints and the objective function are decomposed into subproblems, one for each segment, which means that parallel computation is possible and benecial. The method is implemented and evaluated in a safety-critical double lane-change scenario. By using the solution of a low-complexity initialization problem and applying warm-start techniques in the optimization, a solution is possible to obtain after just a few alternating iterations using the developed approach. The resulting computational time is lower than solving one optimization problem for the full maneuver.

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  • 12.
    Fors, Victor
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Gao, Yangyan
    Univ Lincoln, Lincoln LN6 7TS, England.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Gordon, Timothy
    Univ Lincoln, Lincoln LN6 7TS, England.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Real-Time Minimum-Time Lane Change Using the Modified Hamiltonian Algorithm2020Ingår i: Advances in Dynamics of Vehicles on Roads and Tracks / [ed] Matthijs Klomp, Fredrik Bruzelius, Jens Nielsen, Angela Hillemyr, SPRINGER INTERNATIONAL PUBLISHING AG , 2020, s. 1457-1465Konferensbidrag (Refereegranskat)
    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.

  • 13.
    Kharrazi, Sogol
    et al.
    Linköpings universitet, Institutionen för systemteknik, Informationskodning. Linköpings universitet, Tekniska fakulteten. Swedish Natl Rd and Transport Res Inst, S-58195 Linkoping, Sweden.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Driving Behavior Categorization and Models for Generation of Mission-based Driving Cycles2019Ingår i: 2019 IEEE INTELLIGENT TRANSPORTATION SYSTEMS CONFERENCE (ITSC), IEEE , 2019, s. 1349-1354Konferensbidrag (Refereegranskat)
    Abstract [en]

    The concept of mission-based driving cycles has been introduced as an efficient way of generating driving cycles with desired characteristics for data-driven development of vehicle powertrains. Mission-based driving cycles can be generated using traffic simulation tools with improved behavioral models that match simulation outputs and naturalistic driving data. Here, driving behavior categorization and how it can be used to create a set of differently parameterized behavioral models corresponding to various types of drivers, are studied. The focus is on curvy road driving, and two different categorization features are used, speed through the curves and the braking behavior.

  • 14.
    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. Lund Univ, Sweden.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Efficient Motion Planning for Autonomous Vehicle Maneuvers Using Duality-Based Decomposition2019Ingår i: IFAC PAPERSONLINE, ELSEVIER , 2019, Vol. 52, nr 5, s. 78-84Konferensbidrag (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 fixed and 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. (C) 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

  • 15.
    Kharrazi, Sogol
    et al.
    Linköpings universitet, Institutionen för systemteknik, Informationskodning. Linköpings universitet, Tekniska fakulteten. Swedish Natl Rd and Transport Res Inst, Sweden.
    Almen, Marcus
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska fakulteten. Saab Def and Space, S-58015 Linkoping, Sweden.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Extending Behavioral Models to Generate Mission-Based Driving Cycles for Data-Driven Vehicle Development2019Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 68, nr 2, s. 1222-1230Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Driving cycles are nowadays, to an increasing extent, used as input to model-based vehicle design and as training data for development of vehicle models and functions with machine learning algorithms. Recorded real driving data may underrepresent or even lack important characteristics, and therefore there is a need to complement driving cycles obtained from real driving data with synthetic data that exhibit various desired characteristics. In this paper, an efficient method for generation of mission-based driving cycles is developed for this purpose. It is based on available effective methods for traffic simulation and available maps to define driving missions. By comparing the traffic simulation results with real driving data, insufficiencies in the existing behavioral model in the utilized traffic simulation tool are identified. Based on these findings, four extensions to the behavioral model are suggested, staying within the same class of computational complexity so that it can still be used in a large scale. The evaluation results show significant improvements in the match between the data measured on the road and the outputs of the traffic simulation with the suggested extensions of the behavioral model. The achieved improvements can be observed with both visual inspection and objective measures. For instance, the 40% difference in the relative positive acceleration of the originally simulated driving cycle compared to real driving data was eliminated using the suggested model.

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  • 16.
    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 manoeuvres2019Ingår 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.

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    Formulation and interpretation of optimal braking and steering patterns towards autonomous safety-critical manoeuvres
  • 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. Department of Automatic Control, Lund University, Lund, Sweden.
    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.

  • 18.
    Mohseni, Fatemeh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Decoupled Sampling-Based Velocity Tuning and Motion Planning Method for Multiple Autonomous Vehicles2018Ingår i: 2018 IEEE Intelligent Vehicles Symposium (IV), 2018, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes a decoupled sampling-based motion-planning method, based on the rapidly-exploring random tree (RRT) approach, that is applicable to autonomous vehicles, in order to perform different traffic maneuvers. This is a two-step motion-planning method including path-planning and motion timing steps, where both steps are sampling-based. In the path-planning part, an improved RRT method is defined that increases the smoothness of the path and decreases the computational time of the RRT method; it is called smooth RRT, SRRT. While some other RRT-based methods such as RRT can perform better in winding roads, in the problem of interest in this paper (which is performing some regular traffic maneuvers in usual urban roads and highways where the passage is not too winding), SRRT is more efficient since the computational time is less than for the other considered methods. In the motion timing or velocity-tuning step (VTS), a sampling-based method is introduced that guarantees collision avoidance between different vehicles. The proposed motion-timing algorithm can be very useful for collision avoidance and can be used with any other path-planning method. Simulation results show that because of the probabilistic property of the SRRT and VTS algorithms, together with the decoupling feature of the method, the algorithm works well for different traffic maneuvers.

  • 19.
    Kharrazi, Sogol
    et al.
    Linköpings universitet, Institutionen för systemteknik, Informationskodning. Linköpings universitet, Tekniska fakulteten. Swedish Natl Rd and Transport Res Inst VTI, Linkoping, Sweden.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Design cycles for a given driving mission2018Ingår i: DYNAMICS OF VEHICLES ON ROADS AND TRACKS, VOL 1, CRC PRESS-TAYLOR & FRANCIS GROUP , 2018, s. 323-328Konferensbidrag (Refereegranskat)
    Abstract [en]

    Representative driving cycles are of key importance for design and dimensioning of powertrains. One approach for generation of representatives driving cycles is to define relevant driving missions which include different street types, obstacles and traffic conditions, and simulate them in a traffic simulation tool. Such a simulation approach will also require representative driver models to generate the speed profiles for the defined driving missions. Feasibility of this approach is investigated in this paper.

  • 20.
    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.

  • 21.
    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 Maneuvers for Ground Vehicles2018Ingår i: Proceedings of the 14th International Symposium on Advanced Vehicle Control, Beijing, July 16-20, 2018, 2018, s. 1-6Konferensbidrag (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.

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    Segmentation and Merging of Autonomous At-the-Limit Maneuvers for Ground Vehicles
  • 22.
    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.

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    Slip-Angle Feedback Control for Autonomous Safety-Critical Maneuvers At-the-Limit of Friction
  • 23.
    Mohseni, Fatemeh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Distributed Model Predictive Control for Highway Maneuvers2017Ingår i: IFAC PAPERSONLINE, ELSEVIER SCIENCE BV , 2017, Vol. 50, nr 1, s. 8531-8536Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes a cooperative control method for autonomous vehicles, in order to perform different traffic maneuvers. The problem is formulated as a distributed optimal control problem for a system of multiple autonomous vehicles with an identified model and then solved using nonlinear Model Predictive Control (MPC). The distributed approach has been used in order to make the problem computationally feasible to be solved in real-time. In the proposed method, each vehicle computes its own control inputs using estimated states of neighboring vehicles. The constraints on the control inputs ensure the comfort of passengers. The method allows us to construct a cost function for several different scenarios in which safety and performing the maneuver constitute two terms of the integrated cost of the finite horizon optimization problem. To provide safety, a potential function is introduced for collision avoidance. Simulation results show that the distributed algorithm scales well with increasing number of vehicles. (C) 2017, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

  • 24.
    Nyberg, Peter
    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.
    Driving Cycle Equivalence and Transformation2017Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 66, nr 3, s. 1963-1974Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is a current strong trend where driving cycles are used extensively in vehicle design, especially for calibration and tuning of all powertrain systems for control and diagnosis. In such situations it is essential to capture real driving, and therefore using only a few driving cycles would lead to the risk that a test or a design would be tailored to details in a specific driving cycle. Consequently there are now widespread activities using techniques from statistics, big data and mission modeling to address these issues. For all such methods there is an important final step to calibrate a representative cycle to adhere to fair propulsion requirements on the driven wheels over a cycle. For this a general methodology has been developed, applicable to a wide range of problems involving driving cycle transformations. It is based on a definition of equivalence for driving cycles that loosely speaking defines being similar without being the same. Based on this, a set of algorithms are developed to transform a given driving cycle into an equivalent one, or into a cycle with given equivalence measure. The transformations are effectively handled as a nonlinear program that is solved using general purpose optimization techniques. The proposed method is general and a wide range of constraints can be used.

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    fulltext
  • 25.
    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.

  • 26.
    Mohseni, Fatemeh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Åslund, Jan
    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.
    Fuel and Comfort Efficient Cooperative Control for Autonomous Vehicles2017Ingår i: 2017 28TH IEEE INTELLIGENT VEHICLES SYMPOSIUM (IV 2017), IEEE , 2017, s. 1631-1636Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a cooperative fuel and comfort efficient control for autonomous vehicles is presented in order to perform different traffic maneuvers. The problem is formulated as an optimal control problem in which the cost function takes into account the fuel consumption and passengers comfort, subject to safety and speed constraints. The optimal solution takes into account the comfort and fuel consumption, which is obtained by minimizing a jerk, an acceleration, and a fuel criterion. It is shown that the method can be applied to control different groups of vehicles in different traffic scenarios. Simulation results are used to illustrate the generality property and performance of the proposed approach.

  • 27.
    Lundahl, Kristoffer
    et al.
    Linköpings universitet, Institutionen för systemteknik. 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 manoeuvres2017Ingår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 55, nr 12, s. 1909-1945Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Path planning and path following are core components in safe autonomous driving. Typically, a path planner provides a path with some tolerance 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 arise as on-the-limit solutions. The study focuses on heavy commercial vehicles, causing rollover to be of a major concern, due to the relatively high centre of gravity. 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 interplays with available friction. Overall, in situations where the vehicle is subject to a wide range of driving conditions, from good transport roads to more tricky avoidance manoeuvres, the requirements on the path following will vary. For this, the provided results form a basis for real-time path following.

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    fulltext
  • 28.
    Olofsson, Bjorn
    et al.
    Lund University, Sweden.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Path-tracking velocity control for robot manipulators with actuator constraints2017Ingår i: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 45, s. 82-99Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An algorithm for high-performance path tracking for robot manipulators in the presence of model uncertainties and actuator constraints is presented. The path to be tracked is assumed given, and the nominal trajectories are computed using, for example, well-known algorithms for time-optimal path tracking. For online path tracking, the nominal, feedforward trajectories are combined with feedback in a control architecture with a secondary controller, such that robustness to uncertainties in model or environment is achieved. The control law is based on existing path-velocity control (PVC), or so called online time scaling, but in addition to speed adaptation along the tangent of the path, the algorithm also comprises an explicit formulation and approach, with several attractive properties, for handling the deviations along the transversal directions of the path. For achieving fast convergence along the normal and binormal directions of the path in 3D motion, the strategy proposed has inherent exponential convergence properties. The result is a complete architecture for path-tracking velocity control (PTVC). The method is evaluated in extensive simulations with manipulators of different complexity, and PTVC exhibits superior performance compared to PVC. (C) 2017 Elsevier Ltd. All rights reserved.

  • 29.
    Sundström, Christofer
    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.
    Diagnostic Method Combining the Lookup Tables and Fault Models Applied on a Hybrid Electric Vehicle2016Ingår i: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 24, nr 3, s. 1109-1117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A common situation in industry is to store measurements for different operating points in the lookup tables, often called maps. They are used in many tasks, e.g., in control and estimation, and therefore considerable investments in engineering time are spent in measuring them which usually make them accurate descriptions of the fault-free system. They are thus well suited for fault detection, but, however, such a model cannot give fault isolation since only the fault free behavior is modeled. One way to handle this situation would be also to map all fault cases but that would require measurements for all faulty cases, which would be costly if at all possible. Instead, the main contribution here is a method to combine the lookup model with analytical fault models. This makes good use of all modeling efforts of the lookup model for the fault-free case, and combines it with fault models with reasonable modeling and calibration efforts, thus decreasing the engineering effort in the diagnosis design. The approach is exemplified by designing a diagnosis system monitoring the power electronics and the electric machine in a hybrid electric vehicle. An extensive simulation study clearly shows that the approach achieves both good fault detectability and isolability performance. A main point is that this is achieved without the need for neither measurements of a faulty system nor detailed physical modeling, thus saving considerable amounts of development time.

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    fulltext
  • 30.
    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.
    Path-dependent rollover prevention for critical truck maneuvers2016Ingår i: The Dynamics of Vehicles on Roads and Tracks: Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics (IAVSD 2015), Graz, Austria, 17-21 August 2015 / [ed] Martin Rosenberger, Manfred Plöchl, Klaus Six, Johannes Edelmann, CRC Press, 2016, s. 317-326Konferensbidrag (Refereegranskat)
    Abstract [en]

    Predicting rollover is usually performed using rollover indices, where rollover is anticipated when the indices reach certain threshold values. If knowledge about the vehicle driving path is available, rollover can be detected and prevented earlier. In this work, the rollover-prediction and rollover-prevention abilities for simple vehicle models are evaluated and compared against a high-fidelity vehicle model. The analysis is performed by using the models in critical and rolloverprone maneuvers, generated with optimal control methods. The main conclusion is that a simple point-mass model would be sufficient in a velocity based rollover-prevention controller.

  • 31.
    Nyberg, Peter
    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.
    Using Real-World Driving Databases to Generate Driving Cycles with Equivalence Properties2016Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 65, nr 6, s. 4095-4105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to the increasing complexity of vehicle design, understanding driver behavior and driving patterns is becoming increasingly more important. Therefore, a large amount of test driving is performed, which together with recordings of normal driving, results in large databases of recorded drives. A fundamental question is how to make best use of these data to devise driving cycles suitable in the development process of vehicles. One way is to generate driving cycles that are representative for the data or for a suitable subset of the data, e.g., regarding geographical location, driving distance, speed range, or many other possible selection variables. Further, to make a fair comparison on two such driving cycles possible, another fundamental requirement is that they should have similar excitation of the vehicle. A key contribution here is an algorithm that combines the two given objectives. A formulation with Markov processes is used to obtain a condensed and effective characterization of the database and to generate candidate driving cycles (CDCs). In addition to that is a method transforming a candidate to an equivalent driving cycle (EqDC) with desired excitation. The method is a general approach but is here based on the components of the mean tractive force (MTF), and this is motivated by a hardware-in-the-loop experiment showing the strong relevance of these MTF components regarding fuel consumption. The result is a new method that combines the generation of driving cycles using real-world driving cycles with the concept of EqDCs.

  • 32.
    Sundström, Christofer
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    A New Electric Machine Model and its Relevance for Vehicle Level Diagnosis2015Ingår i: International Journal of Modelling, Identification and Control, ISSN 1746-6172, Vol. 24, nr 1, s. 1-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the electrification of society, especially transportation, the control and supervision of electrical machines become more and more important due to its bearing on energy, environment, and safety. To optimise performance in control and supervision, appropriate modelling is crucial, and this regards both the ability to capture reality and the computational complexity to be useful in real-time. Here, a new low complexity model of the electric machine is proposed and developed. The new model treats the machine constants in a different way compared to a previous standard model, which results in a different expression for power losses. It is shown that this increases model expressiveness so when adapted to real data the result is significantly better. The significance of this modelling improvement is demonstrated using a task in vehicle diagnosis where it is shown that the separation between the non-faulty and faulty cases is better and the resulting performance is improved.

  • 33.
    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.

  • 34.
    Nyberg, Peter
    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.
    Generation of Equivalent Driving Cycles Using Markov Chains and Mean Tractive Force Components2014Ingår i: Proceedings of the 19th World Congress, The International Federation of Automatic Control, Elsevier, 2014, Vol. 47, nr 3, s. 8787-8792Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the automotive industry driving cycles have been used to evaluate vehicles in different perspectives. If a vehicle manufacturer focuses only on a fixed driving cycle there is a risk that controllers of the vehicle are optimized for a certain driving cycle and hence are sub-optimal solutions to real-world driving. To deal with this issue, it is beneficial to have a method for generating more driving cycles that in some sense are equivalent but not identical. The idea here is that these generated driving cycles have the same vehicle excitation in the mean tractive force, MTF. Using the individual force components of the MTF in the generation of driving cycles with Markov chains makes it possible to generate equivalent driving cycles that have the same vehicle excitation from real-world driving data. This is motivated since the fuel consumption estimation is more accurate when the MTF components are considered. The result is a new method that combines the generation of driving cycles using real-world driving cycles with the concept of equivalent driving cycles, and the results are promising.

  • 35.
    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)
  • 36.
    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.

  • 37.
    Sundström, Christofer
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Selecting and Utilizing Sequential Residual Generators in FDI Applied to Hybrid Vehicles2014Ingår i: IEEE TRANSACTIONS ON SYSTEMS MAN CYBERNETICS-SYSTEMS, ISSN 2168-2216, Vol. 44, nr 2, s. 172-185Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to obtain a realistic model of a complex system, thousands of possible residual generators need to be used for diagnosis. Based on engineering insights of the system to be monitored, certain algebraic and dynamic properties of the residual generators may be preferred, and therefore, a method for finding sequential residual generators is developed that accounts for these properties of the residual generator candidates. It is shown that only a small fraction of all residual generator candidates fulfill fundamental requirements, and thereby, proves the value of systematic methods. Furthermore, methods are devised for utilization of the residual generators, such as initialization of dynamic residual generators. A proposed method, considering the fault excitation in the residuals using the internal form of the residuals, significantly increases the diagnosis performance. A hybrid electric vehicle is used in a simulation study for demonstration, but the methods used are general in character and provides a basis when designing diagnosis systems for other complex systems.

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  • 38.
    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.

  • 39.
    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.

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  • 40.
    Öberg, Per
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nyberg, Peter
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Tekniska högskolan.
    A New Chassis Dynamometer Laboratory for Vehicle Research2013Ingår i: SAE International Journal of Passenger Cars - Electronic and Electrical Systems, ISSN 1946-4614, E-ISSN 1946-4622, Vol. 6, nr 1, s. 152-161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In recent years the need for testing, calibration and certification of automotive components and powertrains have increased, partly due to the development of new hybrid concepts. At the same time, the development within electrical drives enables more versatile chassis dynamometer setups with better accuracy at a reduced cost. We are developing a new chassis dynamometer laboratory for vehicle research, aiming at extending a recently commercially available dynamometer, building a new laboratory around it, and applying the resulting facility to some new challenging vehicle research problems. The projects are enabled on one hand by collaboration with the dynamometer manufacturer, and on the other hand on collaboration with automotive industry allowing access to relevant internal information and equipment. The test modes of the chassis dynamometer are under development in a joint collaboration with the manufacturer. The laboratory has been operational since September 2011 and has already been used for NVH-analysis for a tire pressure indication application, chassis dynamometer road force co-simulation with a moving base simulator, co-surge modeling and control for a 6-cylinder bi-turbo engine, and traditional engine mapping. We are also looking at projects with focus on look-ahead control, as well as clutch and transmission modeling and control, and driving cycle related research.

  • 41.
    Olofsson, Björn
    et al.
    Department of Automatic Control, Lund University, Lund, Sweden.
    Lundahl, Kristoffer
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Berntorp, Karl
    Department of Automatic Control, Lund University, Lund, Sweden.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    An Investigation of Optimal Vehicle Maneuvers for Different Road Conditions2013Ingår i: IFAC Proceedings Volumes, Volume 46, Issue 21, International Federation of Automatic Control , 2013, Vol. 46, s. 66-71Konferensbidrag (Refereegranskat)
    Abstract [en]

    We investigate optimal maneuvers for road-vehicles on different surfaces such as asphalt, snow, and ice. The study is motivated by the desire to find control strategies for improved future vehicle safety and driver assistance technologies. Based on earlier presented measurements for tire-force characteristics, we develop tire models corresponding to different road conditions, and determine the time-optimal maneuver in a hairpin turn for each of these. The obtained results are discussed and compared for the different road characteristics. Our main findings are that there are fundamental differences in the control strategies on the considered surfaces, and that these differences can be captured with the adopted modeling approach. Moreover, the path of the vehicle center-of-mass was found to be similar for the different cases. We believe that these findings imply that there are observed vehicle behaviors in the results, which can be utilized for developing the vehicle safety systems of tomorrow.

  • 42.
    Nyberg, Peter
    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.
    Driving Cycle Adaption and Design Based on Mean Tractive Force2013Ingår i: Proceedings of the 7th IFAC Symposium on Advances in Automotive Control, The International Federation of Automatic Contro, Elsevier, 2013, Vol. 46, nr 21, s. 689-694Konferensbidrag (Refereegranskat)
    Abstract [en]

    Driving cycles are used for certification, for comparison of vehicles, and to an increasing extent as an engineering tool in vehicle design. A situation with only a few fixed driving cycles to use would then lead to the risk that a test or design would be tailored to details in the driving cycle instead of being representative. Due to this, and due to the increased use in the development process, there is now a strong need for methods to achieve representative driving cycles that in a wide sense are similar but not the same. To approach this problem area, we define equivalence between driving cycles based on mean tractive force, and develop algorithms and methods for equivalence-modification and equivalence-transformation of driving cycles. There are a number of applications for these methods but one example that is demonstrated is to transform the well-known FTP75 into an equivalent NEDC, and the other way around, to transform the NEDC into an equivalent FTP75.

  • 43.
    Sundström, Christofer
    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.
    Fault Monitoring of the Electric Machine in a Hybrid Vehicle2013Ingår i: Proceedings of the 7th IFAC Symposium on Advances in Automotive Control, The International Federation of Automatic Control, Elsevier, 2013, Vol. 46, nr 21, s. 548-553Konferensbidrag (Refereegranskat)
    Abstract [en]

    A diagnosis system for the electric machine and the power electronics in a hybrid electric vehicle is designed, where the diagnosis system uses a map based model of the system to be monitored. Such a model gives an accurate description of the fault free system, and is therefore suited for fault detectability. However, one drawback using such a model for diagnosis is that fault isolation often requires that the model, in addition to the fault free case, also describes the faulty system, and thereby measurements of the faulty system are needed, which is costly. Another approach is to use a model including physical parameters of interest in the system to be monitored, to also describe the faults’ impact on the system. To achieve good diagnostic performance such a model needs to be accurate, which also is costly. Therefore, in the new approach taken here, two models for the system are used in combination to achieve good fault detectability and isolability; one is a map based model, and one is describing the faults of the system. It is shown that the approach works well and is a promising path to achieve both good fault detectability and isolability performance, without the need for neither measurements of a faulty system nor detailed physical modeling. In a simulation study evaluating the designed diagnosis system all faults are isolated and also accurately estimated.

  • 44.
    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.

  • 45.
    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.

  • 46.
    Lundahl, Kristoffer
    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.
    Vehicle dynamics platform, experiments, and modeling aiming at critical maneuver handling2013Rapport (Övrigt vetenskapligt)
    Abstract [en]

    For future advanced active safety systems, in road-vehicle applications, there will arise possibilities for enhanced vehicle control systems, due to refinements in, e.g., situation awareness systems. To fully utilize this, more extensive knowledge is required regarding the characteristics and dynamics of vehicle models employed in these systems. Motivated by this, an evaluative study for the lateral dynamics is performed, considering vehicle models of more simple structure. For this purpose, a platform for vehicle dynamics studies has been developed. Experimental data, gathered with this testbed, is then used for model parametrization, succeeded by evaluation for an evasive maneuver. The considered model configurations are based on the single-track model, with different additional attributes, such as tire-force saturation, tire-force lag, and roll dynamics. The results indicate that even a basic model, such as the single-track with tire-force saturation, can describe the lateral dynamics surprisingly well for this critical maneuver.

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  • 47.
    Nickmehr, Neda
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Lundahl, Kristoffer
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    On experimental-analytical evaluation of passenger car ride quality subject to engine and road disturbances2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    A straightforward approach is presented to investigate the ride dynamic system for a typical rear-drive passenger car. The procedure is based on introducing two main ride excitation sources, i.e., engine/driveline and road inputs, which reduce passengers’ comfort. The measured engine fluctuating torques are applied on the coupled model of the driveline and the suspension, to obtain the vehicle body longitudinal vibration. Further, the body vertical response to an average road roughness, is found by employing the quarter-car model. Through the frequency analysis done in this paper, it is shown that we can fastly determine the transfer functions of the systems and also their forced responses at the desired positions, without guessing any initial conditions for the states. The results illustrate that the high frequency inputs, from the engine, are appropriately damped by the current suspension. Hence, the associated vehicle body longitudinal acceleration meets the \acISO criteria. This is not the case for the low frequency disturbances, from the road surface irregularities, where the vehicle body vertical acceleration is above the \acISO criteria.

  • 48.
    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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  • 49.
    Sundström, Christofer
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Residual Generator Selection for Fault Diagnosis of Hybrid Vehicle Powertrains2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    The performance of a model based diagnosis system is affected by the selection of consistency relation in a set of equations with analytical redundancy in a non-linear system. To investigate aspects due to this, two diagnosis systems of a parallel hybrid truck are designed, and both static and dynamic issues are considered. A simplified vehicle model is used to exemplify how a unique expression for the residual generator can be found for one selection of consistency relation, but not for others, using the same set of equations. A simulation study using the entire vehicle model is made to investigate how the performance in the diagnosis system is affected when dynamic equations are either differentiated or integrated. The diagnosis systems are designed using structural analysis in combination with the algebraic expressions. One key result is that it is not trivial to find a computational order by hand that fulfills the predefined conditions on the computational sequence, and therefore systematic methods are valuable.

  • 50.
    Sundström, Christofer
    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.
    A Platform for Overall Monitoring and Diagnosis for Hybrid Vehicles2010Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Compared with conventional vehicles, designing hybrid electric vehicles includes new features, such as energy management and monitoring of the electrical components. To be able to investigate such issues a simulation platform of a hybrid vehicle, driver, and diagnosis system is developed based on the CAPSim model library. The simulation platform is component based, and is able to handle different powertrain configurations. In this investigation a parallel hybrid is modeled and parameterized to represent a long haulage truck. To be able to easily change a model of a component in the vehicle model, every model of a specific component use the same sets of input and output signals. The vehicle model is based on dynamic equations and in general simple models of the components, since the interplay of the components is of major interest in this investigation. Three model based diagnosis systems are developed and implemented in the platform with a twofolded purpose. The first purpose is to demonstrate the feasibility of the platform. The second purpose is to investigate issues when designing diagnosis systems on vehicle level of a hybrid vehicle powertrain. New features, for example mode switches in the system and a freedom in choosing operating points of the components via the energy management, affect the diagnosis system. The influence of these issues on the performance of the diagnosis system is investigated by design and implementation of three diagnosis systems on a vehicle level. The diagnosis systems are based on three sensor configurations. Two of these consist of several sensors and one system uses few sensors. In one of the systems using information from several sensors, the sensors are placed close to the components that are to be monitored, while the sensors in the other system is based on a different sensor configuration. All three diagnosis systems detect specific faults, here specifically faults in the electrical components in a hybrid vehicle powertrain, but the methodology is generic. It is shown that there is a connection between the design of the energy management and the three diagnosis systems, and that this interplay is of special relevance when models of components are valid only in some operating modes. The diagnosis system based on few sensors is more complex and includes a larger part of the vehicle model than the system based on several sensors placed close to the components to be monitored.

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    A Platform for Overall Monitoring and Diagnosis for Hybrid Vehicles
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