@inproceedings {INPROC-2006-70,
   author = {Pascal Montag and Steffen G{\"o}rzig and Paul Levi},
   title = {{Challenges of Timing Verification Tools in the Automotive Domain}},
   booktitle = {2nd IEEE International Symposium on Leveraging Applications of Formal Methods, Verification and Validation, Paphos (Cyprus), November 15-19, 2006},
   publisher = {IEEE CS Press},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {1--6},
   type = {Conference Paper},
   month = {November},
   year = {2006},
   keywords = {embedded real-time systems; automotive safety},
   language = {English},
   cr-category = {I.2.9 Robotics,
                   I.2.10 Vision and Scene Understanding,
                   I.2.11 Distributed Artificial Intelligence},
   contact = {Paul.Levi@ipvs.uni-stuttgart.de},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {Every embedded real-time system is inevitably time restricted. Therefore,
      worst-case execution times (WCETs) have to be known. The static timing analysis
      of embedded software promises the calculation of safe upper time bounds. We
      present the results of a case study which reveal the special challenges of this
      methodology in the automotive domain. For most of the encountered problems we
      describe our solutions or propose possible methods for a solution.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2006-70&engl=1}
}

@inproceedings {INPROC-2006-69,
   author = {Pascal Montag and Dirk Nowotka and Paul Levi},
   title = {{Verification in the Design Process of Large Real-Time Systems: A Case Study}},
   booktitle = {Automotive Safety and Security 2006, Stuttgart (Germany), October 12-13, 2006},
   publisher = {Shaker Verlag},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {1--13},
   type = {Conference Paper},
   month = {October},
   year = {2006},
   keywords = {complex real-time systems; automotive safety},
   language = {English},
   cr-category = {I.2.9 Robotics,
                   I.2.10 Vision and Scene Understanding,
                   I.2.11 Distributed Artificial Intelligence},
   contact = {Paul.Levi@ipvs.uni-stuttgart.de},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {A verification case study of a complex real-time system from the automotive
      area, an emergency brake assistant, is conducted. In particular the application
      and usefulness of formal methods in the refinement process during the design of
      a large system is investigated, where we mean by ``large system'' a system which
      cannot be formally verified as a whole due to its complexity. We establish that
      the application of formal methods in the early phase of a system design is
      beneficial despite the limits of current tools. Useful directions of further
      work to improve the verified design of safety-critical systems are also shown.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2006-69&engl=1}
}

@inproceedings {INPROC-2006-68,
   author = {Pascal Montag and Steffen G{\"o}rzig and Paul Levi},
   title = {{Applying Static Timing Analysis to Component Architectures}},
   booktitle = {Proceedings of the 28th International Conference on Software Engineering, Shanghai (China), May 20-28, 2006},
   address = {Shanghai},
   publisher = {ICSE},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {1--7},
   type = {Conference Paper},
   month = {May},
   year = {2006},
   keywords = {automotive applications},
   language = {English},
   cr-category = {I.2.9 Robotics,
                   I.2.10 Vision and Scene Understanding,
                   I.2.11 Distributed Artificial Intelligence},
   contact = {Paul.Levi@ipvs.uni-stuttgart.de},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {The increase in software functions and software complexity of automotive
      applications requires appropriate software architectures. A promising approach
      is the component architecture which also stands in the centre of the automotive
      standardisation project AUTOSAR. As every embedded real-time system inevitably
      has upper time bounds, we present an integrated method of timing estimation for
      highly flexible and variant applications based on a prototype component
      architecture. Therefore, we especially develop methods for parameterised timing
      estimation which depend on the grade of complexity, variability and necessary
      exactness. The feasibility of the introduced concept is shown in the prototype
      architecture and a prototype application.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2006-68&engl=1}
}

@inproceedings {INPROC-2006-59,
   author = {Oliver Zweigle and Uwe-Philipp K{\"a}ppeler and Reinhard Lafrenz and Paul Levi},
   title = {{Situation recognition for reactive agent behavior}},
   booktitle = {Artificial Intelligence and Soft Computing},
   address = {Palma de Mallorca},
   publisher = {IASTED},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {1--8},
   type = {Conference Paper},
   month = {August},
   year = {2006},
   keywords = {situation recognition; cooperative robotics},
   language = {English},
   cr-category = {I.2.9 Robotics},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {Situation recognition in RoboCup gets more and more important to enhance team
      behavior strategies. In this paper we present an approach for a cooperative
      situation recognition architecture which directly influences the game strategy
      of the own team. The presented situation recognition architecture is derived
      from the human archetype to recognize situations by a combination of learned
      knowledge and observation of the environment. Humans only consider a limited
      number of situation interpretations for certain environmental scenes. We
      transfer that concept and introduce Situation Libraries as an analogous
      approach for computer systems. Consequently for every recognized situation a
      cooperative team behavior is defined. This will effectively enhance the team
      play and the ability of a team to adapt its behavior to the strategies of an
      opponent and to the current game state.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2006-59&engl=1}
}

@inproceedings {INPROC-2006-58,
   author = {Ralf Regele and Paul Levi},
   title = {{Cooperative Multi-Robot Path Planning by Heuristic Priority Adjustment}},
   booktitle = {Proceedings of the 2006 IEEE/RSJ International Conference on Intelligent Robots and Systems},
   address = {Peking},
   publisher = {IEEE},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {5954--5959},
   type = {Conference Paper},
   month = {October},
   year = {2006},
   isbn = {1-4244-0259-X},
   keywords = {cooperative path planning; multi-robot systems; conflict resolution},
   language = {English},
   cr-category = {I.2.9 Robotics},
   contact = {Ralf.Regele@informatik.uni-stuttgart.de},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {In this paper, a new algorithm for cooperative path planning in a multi-robot
      system is introduced. The algorithm is specially designed for a distributed
      system with a large number of robots, all of which should be able to reach
      their respective goal positions without blocking each other, even if the
      environment is heavily constricted by obstacles. The basic idea of the approach
      is based on fully distributed path planning without any central instance, but
      with the ability of communication and cooperation between the robots. Path
      planning is done on local sections of the time-space configuration space.
      Dynamic conflicts between the robots are solved by the heuristic adjustment of
      priority values. By a continuous enhancement of all plans the algorithm is very
      robust against dynamic changes and erroneous robot behavior.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2006-58&engl=1}
}

@inproceedings {INPROC-2006-53,
   author = {R. Lafrenz and O. Zweigle and U.-P. K{\"a}ppeler and H. Rajaie and A. Tamke and T. R{\"u}hr and M. Oubbati and M. Schanz and F. Schreiber and P. Levi},
   title = {{Major Scientific Achievements 2006 - CoPS Stuttgart registering for world championships in Bremen}},
   booktitle = {RoboCup International Symposium 2006},
   address = {Bremen},
   publisher = {Universit{\`a} degli Studi di Milano},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {1--9},
   type = {Conference Paper},
   month = {June},
   year = {2006},
   keywords = {Robocup; robotics; autonomous; agent},
   language = {English},
   cr-category = {I.2.9 Robotics,
                   I.2.10 Vision and Scene Understanding,
                   I.2.11 Distributed Artificial Intelligence,
                   I.2 Artificial Intelligence},
   ee = {http://robocup.informatik.uni-stuttgart.de/,
      http://www.robocup.org},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {The CoPS robot soccer team is used as a testbed for multiagent software
      architecture principles in dynamic real time domains. Based on a highly modular
      and e cient software infrastructure design for world modeling the current and
      future research activities focus on methods for a reliable and team consistent
      world modeling, as well as a coordinated distributed team behavior modeling. In
      this work, we present the current state of the software architecture of our
      team and the world modeling approach. Furthermore we describe our team behavior
      design approach which was developed during the last year.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2006-53&engl=1}
}

@inproceedings {INPROC-2006-37,
   author = {Oliver Zweigle and Reinhard Lafrenz and Thorsten Buchheim and Uwe-Philipp K{\"a}ppeler and Hamid Rajaie and Frank Schreiber and Paul Levi},
   title = {{Cooperative Agent Behavior Based on Special Interaction Nets}},
   booktitle = {Proceedings of the 9th International Conference on Intelligent Autonomous Systems 2006, IAS-9, Tokio},
   address = {Tokio},
   publisher = {IOS Press},
   institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany},
   pages = {651--659},
   type = {Conference Paper},
   month = {March},
   year = {2006},
   isbn = {1-58603-595-9},
   keywords = {robotic; Robotik; cooperation; autonomous; autonom; Kooperation},
   language = {German},
   cr-category = {I.2.9 Robotics},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {An important aim of the current research e ort in artificial intelligence and
      robotics is to achieve cooperative agent behavior for teams of robots in
      real-world scenarios. Especially in the RoboCup scenario, but also in other
      projects like Nexus, agents have to cooperate eficiently to reach certain
      goals. In the RoboCup project, cooperative team-play and team strategies
      similar to real world soccer are intended. This article describes an approach
      that combines cooperative aspects, role assignment algorithms and the
      implementation of robot behavior with Interaction Nets. Based on these single
      methods, a complete framework for team strategies was developed that is used in
      the RoboCup environment for the middle-size team CoPs Stuttgart and in the
      Nexus project, where a team of robots guides persons through a building.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2006-37&engl=1}
}

@article {ART-2006-09,
   author = {Viktor Avrutin and Michael Schanz and Soumitro Banerjee},
   title = {{Multi-parametric Bifurcations in a piecewise-linear discontinuous Map}},
   journal = {Nonlinearity},
   publisher = {IoP The Institute of Physics Publishing},
   volume = {19},
   pages = {1875--1906},
   type = {Article in Journal},
   month = {March},
   year = {2006},
   doi = {10.1088/0951-7715/19/8/007},
   keywords = {codimension-3; non-smooth dynamical systems; period adding; period increment},
   language = {English},
   cr-category = {G.1.0 Numerical Analysis General,
                   J.2 Physical Sciences and Engineering},
   contact = {Michael.Schanz@informatik.uni-stuttgart.de Viktor.Avrutin@informatik.uni-stuttgart.de},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {In this paper a one-dimensional piecewise linear map with discontinuous system
      function is investigated. This map actually represents the normal form of the
      discrete-time representation of many practical systems in the neighbourhood of
      the point of discontinuity. In the 3D parameter space of this system we detect
      an infinite number of co-dimension one bifurcation planes, which meet along an
      infinite number of co-dimension two bifurcation curves. Furthermore, these
      curves meet at a few co-dimension three bifurcation points. Therefore, the
      investigation of the complete structure of the 3D parameter space can be
      reduced to the investigation of these co-dimension three bifurcations, which
      turn out to be of a generic type. Tracking the influence of these bifurcations,
      we explain a broad spectrum of bifurcation scenarios (like period increment and
      period adding) which are observed under variation of one control parameter.
      Additionally, the bifurcation structures which are induced by so-called big
      bang bifurcations and can be observed by variation of two control parameters
      can be explained.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2006-09&engl=1}
}

@article {ART-2006-03,
   author = {V. Avrutin and P. Levi and M. Schanz and D. Fundinger and G. Osipenko},
   title = {{Investigation of Dynamical Systems Using Symbolic Images: Efficient Implementation and Applications}},
   journal = {International Journal of Bifurcation and Chaos},
   address = {New Jersey, London, Singapore, Hong Kong},
   publisher = {World Scientific Publishing Company},
   volume = {16},
   number = {12},
   pages = {3451--3496},
   type = {Article in Journal},
   month = {December},
   year = {2006},
   doi = {10.1142/S0218127406016938},
   keywords = {symbolic image, invariant set, basin of attraction, stable manifold, unstable manifold},
   language = {English},
   cr-category = {G.1.0 Numerical Analysis General,
                   G.1.5 Roots of Nonlinear Equations},
   contact = {Michael.Schanz@informatik.uni-stuttgart.de Viktor.Avrutin@informatik.uni-stuttgart.de},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {Symbolic images represent a unified framework to apply several methods for the
      investigation of dynamical systems both discrete and continuous in time. By
      transforming the system flow into a graph, they allow it to formulate
      investigation methods as graph algorithms. Several kinds of stable and unstable
      return trajectories can be localized on this graph as well as attractors, their
      basins and connecting orbits. Extensions of the framework allow, e.g. the
      calculation of the Morse spectrum and verification of hyperbolicity. In this
      work, efficient algorithms and adequate data structures will be presented for
      the construction of symbolic images and some basic operations on them, like the
      localization of the chain recurrent set and periodic orbits. The performance of
      these algorithms will be analyzed and we show their application in practice.
      The focus is not only put on several standard systems, like Lorenz and Ikeda,
      but also on some less well-known ones. Additionally, some tuning techniques are
      presented for an efficient usage of the method.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2006-03&engl=1}
}

@article {ART-2006-02,
   author = {Viktor Avrutin and Michael Schanz},
   title = {{On multi-parametric Bifurcations in a scalar piecewise-linear Map}},
   journal = {Nonlinearity},
   publisher = {IoP The Institute of Physics Publishing},
   volume = {19},
   pages = {531--552},
   type = {Article in Journal},
   month = {March},
   year = {2006},
   doi = {10.1088/0951-7715/19/3/001},
   keywords = {codimension-3; non-smooth dynamical systems; period adding; period increment},
   language = {English},
   cr-category = {G.1.0 Numerical Analysis General,
                   J.2 Physical Sciences and Engineering},
   contact = {Viktor.Avrutin@informatik.uni-stuttgart.de, Michael.Schanz@informatik.uni-stuttgart.de},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {In this work a one-dimensional piecewise-linear map is considered. The areas in
      the parameter space corresponding to specific periodic orbits are determined.
      Based on these results it is shown that the structure of the 2D and 3D
      parameter spaces can be simply described using the concept of multi-parametric
      bifurcations. It is demonstrated that an infinite number of two-parametric
      bifurcation lines starts at the origin of the 3D parameter space. Along each of
      these lines an infinite number of bifurcation planes starts, whereas the origin
      represents a three-parametric bifurcation.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2006-02&engl=1}
}

@inbook {INBOOK-2006-09,
   author = {V. Avrutin and M. Schanz},
   title = {{Co-dimension 2,3 and 4 Discontinuity induced Bifurcations and their Interaction}},
   series = {Book of Abstracts},
   address = {University of Crete},
   publisher = {n. a.},
   series = {XXVI Int. Conf. Dynamics Days Europe},
   pages = {1--45},
   type = {Article in Book},
   month = {October},
   year = {2006},
   language = {English},
   cr-category = {G.1.10 Numerical Analysis Applications},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {Piecewise-smooth dynamical systems with discontinuous system function were
      intensively investigated in the last years, motivated among other reasons by
      many practical applications as well as by Poincar{\'e} return maps of dynamical
      systems showing chaotic dynamics. However, bifurcations with co-dimension n$>$1
      occurring in piecewise-smooth systems are still far away from being understood
      completely.
      
      In this work we investigate the properties of a special type of co-dimension
      three bifurcation, which we have detected in several maps with discontinuous
      system function. In the systems we consider, bifurcations with co-dimension one
      are caused by simple border collisions. Looking at the 2D parameter spaces, we
      detect some co-dimension two bifurcations points, where an infinite number of
      co-dimension one bifurcation curves intersect. As a next step, we consider 3D
      parameter spaces, and identify here the points, where an infinite number of
      co-dimension two bifurcation curves intersect. These co-dimension three
      bifurcations, reported by first time in, serve as organizing centers for
      periodic and quasi-periodic dynamics. Unfolding these bifurcations, we are able
      to explain several strange looking bifurcation structures, which are often
      observed in 1D and 2D parameter subspaces and which are really difficult to
      understand otherwise.
      
      Further we investigate the boundaries of the influence areas of the detected
      co-dimension three bifurcations. Such an influence area is defined as the union
      of the stability areas of all periodic and quasi-periodic dynamics emerging at
      the co-dimension three bifurcation point. Based on the structure of this
      boundary we are able to explain and to classify transitions to chaos, which
      occur at this boundary. Until now these transitions were reported in many
      publications, but not explained systematically. \% Finally, tracking the paths
      of the co-dimension three bifurcations in the 4D parameter space for one of the
      investigated models, we demonstrate, that the overall structure of this 4D
      parameter space is dominated by a single discontinuity induced co-dimension
      four bifurcation.
      
      The theoretical part of the work is illustrated by several applications
      examples from the field of electronic circuits. Especially, some models of
      DC/DC converters and \$$\backslash$Sigma/$\backslash$Delta\$ modulators are investigated in detail.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INBOOK-2006-09&engl=1}
}

@inbook {INBOOK-2006-08,
   author = {V. Avrutin and B. Eckstein and P. Levi and M. Schanz},
   title = {{Detection of Multi-Band chaotic Attractors}},
   series = {Book of Abstracts of XXVI Int. Conf. Dynamics Days Europe},
   address = {University of Crete},
   publisher = {n. a.},
   series = {XXVI Int. Conf. Dynamics Days Europe},
   pages = {1--45},
   type = {Article in Book},
   month = {October},
   year = {2006},
   language = {English},
   cr-category = {G.1.10 Numerical Analysis Applications},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Image Understanding},
   abstract = {The occurrence of multi-band chaotic attractors (MBCA) represents a well-known
      phenomenon on the field of nonlinear dynamics. For instance, the period
      doubling cascade occurring in several dynamical systems is typically followed
      by an inverse band merging cascade. Whereas the first one is formed by a
      sequence of periodic attractors with periods \$p\_0 $\backslash$cdot 2^n\$ with increasing n,
      the second one represents a sequence of MBCAs with \$p\_0 $\backslash$cdot 2^n\$ bands,
      whereby n decreases from infinity to one. This bifurcation scenario is
      well-known and investigated in detail. However, the question, which other types
      of bifurcation scenarios can be caused by multi-band chaotic attractors and
      their interactions with each other and with unstable orbits, is still
      insufficiently investigated. When dealing with this question, it turns out,
      that efficient algorithms for investigation of MBCAs are missing. The seemingly
      simple question, how to determine the number of bands of a MBCA represents in
      fact a hard task from the numerical point of view.
      
      In this work two methods for the detection of the number of bands of a MBCA are
      presented. The first one is developed for dynamical systems with a continuous
      system function. It can be shown, that in this case the bands of a MBCA are
      visited by an orbit in the same order for all times. This fact combined with
      the mixing property of chaotic attractors allows us to solve the given task
      efficiently, with low requirements with respect to computation time and memory
      consumption. The second method does not use any assumptions concerning the
      properties of the system function and hence can be applied to dynamical systems
      with discontinuous system function as well. The price for this is the lower
      convergence rate and the higher memory consumption.
      
      For both methods we present the results of the performance tests, as well as
      some techniques for ajustment of the parameters. Both methods are validated by
      the investigation of scenarios in several well-known dynamical systems.
      
      Using our second method we investigate some models of electronic cirquits of
      practical interest (DC/DC converters and \$$\backslash$Sigma/$\backslash$Delta\$ modulators). These
      models are intensively investigated in the last few years, especially due to
      the increasing interest on dynamical systems with a discontinuous system
      function. Hereby we present and explain a number of complex bifurcation
      scenarios formed by MBCAs, not reported yet.
      
      The developed methods are implemented within the AnT 4.669 package for
      simulation and investigation of dynamical systems, which is free software and
      can be downloaded from the website: www.AnT4669.de.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INBOOK-2006-08&engl=1}
}