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Publication Type: search.filters.UBSTyp.KonferenzbeitragAuthor: search.filters.author.Schiehlen, Werner

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    Prospects of the German multibody system research project on vehicle dynamics simulation
    (1992) Schiehlen, Werner
    The German Research Council (DFG) decided 1987 to establish a nationwide research project devoted to dynamics of multibody systems. In this project 14 universities and research centers are cooperating with the goal to develop a general purpose multibody system software package. This concept provides the opportunity to use a modular structure of the software, i.e. different multibody formalisms may be combined with different simulation programmes via standardized interfaces. For the DFG project the database RSYST was chosen using standard FORTRAN 77 and an object oriented multibody system datamodel was defined. According to the modular concept the requirements of vehicle system dynamics as tire models or railway wheel-rail models, respectively, are easily met. The Iltis benchmark problem is used to demonstrate some features of the object oriented datamodel.
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    Werkzeuge zur Simulation von Mehrkörpersystemen
    (1992) Leister, Günter; Schiehlen, Werner
    Das dynamische Verhalten von komplexen mechanischen Systemen beeinflußt maßgeblich die Bauteildimensionierung und die Funktionalität von Konstruktionen. Bei der Konzeption von Fahrzeugen, Maschinen und Robotern muß daher dem dynamjschen Verhalten große Beachtung geschenkt werden. Für den Konstrukteur ist es dabei wünschenswert, in einem möglichst frühen Stadium der Konstruktion zuverlässige Aussagen über das dynamische Verhalten zu haben. Ein bewährtes Vorgehen hierfür ist die Simulation des dynamischen Verhaltens mit Rechenmodellen. Die Aufstellung der Bewegungsgleichungen und die Einbindung der Gleichungen in eine geeignete Simulationsumgebung ist vor allem bei großen Ersatzmodellen aufwendig und fehlerträchtig. In diesem Beitrag werden die speziell für die Mehrkörperdynamik konzipierten Werkzeuge NEWEUL und NEWSIM vorgestellt. Ausgehend von der Mehrkörpersystembeschreibung generiert das Programmpaket NEWEUL symbolische Differentialgleichungen und stellt alle für eine automatische Simulation erforderlichen Informationen bereit. Das Programmsystem NEWSIM verwendet anschließend die symbolischen Bewegungsgleichungen in kompilierter Form für die Simulation. Durch die Verwendung eines obiektorientierten Datenmodells stellen die Programme NEWEUL und NEWSIM Werkzeuge eines modulares Programmpaket für die Mehrkörperdynamik dar. Dieses Vorgeben wird am Beispiel eines Mehrfachpendels und eines Ackerschleppers erläutert.
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    Application of parallel computing to robot dynamics
    (1993) Schäfer, Peter; Schiehlen, Werner
    In this paper an approach for the application of parallel processing to the dynamic analysis of robots based on the multibody system method is presented. The inherent structure of the symbolic equations of motion is used for partitioning those into independent modules for concurrent evaluation. The applied strategies for parallelization include the parallel evaluation of subsystem equations and the parallel computation of the inertia matrix along with its factorization, and of the force vectors and control inputs. The implementation of the parallel structures is discussed with respect to optimal utilization of transputer resources. The presented approach yields a strong reduction of computing time and supports real-time simulations of controlled robots, which is also shown in an example.
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    Ein Baukastenkonzept für Modellerstellung, Simulation und Optimierung von Fahrzeugen
    (1992) Leister, Günter; Schiehlen, Werner
    Die Methode der Mehrkörpersysteme wird bei der Simulation von Fahrzeugen seit Jahren mit Erfolg eingesetzt. Dabei sind die zu untersuchenden Ersatzmodelle immer umfangreicher geworden. In der Fahrzeugdynamik werden deshalb Mehrkörpersysteme häufig in Komponenten zerlegt, die sowohl als Einzelmodell aber auch in Verbindung mit anderen Modellen verwendet werden und die einzeln verifiziert sind. Mit Hilfe eines objektorientierten Datenmodells für Mehrkörpersysteme ist die Wiederverwendung derartiger Komponenten, wie beispielsweise kompletten Radaufhängungen, leicht möglich. Eine zentrale Rolle im Gesamtablauf einer Dynamikanalyse spielen Formalismen zur Aufstellung, sowie Integrationsverfahren zur Lösung der Bewegungsgleichungen. Sollen Formalismen und Integrationsverfahren innerhalb einer modularen Software-Umgebung verwendet werden, so müssen die zugrunde liegenden Berechnungsmethoden automatisiert ablaufen. Es werden Methoden zur automatischen Aufstellung und Simulation symbolischer Bewegungsgleichungen von Mehrkörpersystemen vorgestellt. Ausgehend von einem standardisierten Datenmodell für Mehrkörpersysteme werden mit dem Programmsystem NEWEUL symbolische Bewegungsgleichungen in Minimalform aufgestellt und problemspezifische Simulationsprogramme automatisch generiert. Diese werden in compilierter Form innerhalb des Programmsystems NEWSIM für die Simulation verwendet. Dies wird an einem Beispiel aus der Fahrzeugdynamik verdeutlicht.
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    Multibody systems and robot dynamics
    (1990) Schiehlen, Werner
    The method of multibody system has been developed during the last two decades with application to various engineering topics, including robotics and walking machines. On the other hand, special algorithms for robot dynamics are available featuring the high computational efficiency required for control purposes. This paper shows the close relation between both approaches. Essential criteria for the effeciency of dynamics software are the numbers of coordinates used, which should be minimal. For illustration a two-body system is considered, including open and cIosed loop configurations.
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    Bifurcation analysis of dynamic systems with continuously piecewise linearity
    (1994) Hu, Haiyan; Schiehlen, Werner
    The periodic response and associated bifurcations of a harmonically driven oscillator with continuously piecewise linearity has received great attention during the past decade. The oscillator serves as a widely used model to describe various mechanical systems with clearances, elastic constraints etc. Even if the 'corners' of the piecewise-linear restoring force in the oscillator make the system non-smooth on the interface between two linear regions, the bifurcation analysis published up to now is still based on the theory of smooth dynamic systems. The validity of such an extention is an open problem.
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    Stability numbers for nonlinear systems
    (1994) Schiehlen, Werner
    The definition of Lyapunov stability is used for the introduction of stability numbers for nonlinear systems. A norm of the initial conditions || X 0 || and a norm of the system response || X (t)|| are related to each other, resulting in stability numbers depending on the initial conditions. This concept presents some information on the global behaviour of the system including all types of solutions from limit cycles to strange attractors. The stability numbers characterize that part of the state space in which the motion occurs.
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    Dynamics and control of nonholonomic mobile robot systems
    (1994) Schiehlen, Werner
    The positional degrees of freedom of a mobile robot are reduced by nonholonomic constraints further to a smaller number of motional degrees of freedom. It is shown how the equations of motion can be reduced to a minimal number using generalized coordinates and generalized velocities. The theoretical results are applied to an actively controlled robot with stiff tires. One scalar control variable provides full controllability of the position of the robot moving on a plane surface. A control strategy is found for stationary and instationary motions.
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    Dynamical measurements in vehicles by transputer technology
    (1994) Eismann, Wolfgang; Schiehlen, Werner
    The experimental validation of mechanical models in vehicle dynamics requires dynamical measurements while driving. Parallel processing using transputer technology allows long time measurements at high sampling rate without any loss of data as well as online computatlon resulting in a very efficient tool for vibration monitoring and parameter identification of vehicle systems. The paper presents the realization of a mobile data acquisition sytem based on transputer technology and some applications of the system to vibration monitoring and identification of a rolling unbalanced vehicle wheel. The measurements are performed with a standard passenger car of a German trademark.
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    Uncertainties in road vehicle suspensions
    (2015) Schiehlen, Werner; Iroz, Igor
    Road vehicles are subject to random excitation by the unevenness of the road. For a dynamical analysis, vehicle models of the vertical vibrations as well as guideway models of the road unevenness are required. The fundamental dynamics of vehicle suspensions can be already modeled by a quarter car featuring the decoupling of the car body motion and the wheel motion. This suspension model is characterized by five design parameters where two of them, the shock absorber and the tire spring, are highly uncertain due to wear and poor maintenance. For the assessment of the vehicles performance three criteria have to be used: ride comfort, driving safety and suspension travel. These criteria depend on all the five design parameters resulting in a conflict or a pareto-optimal problem, respectively. In this paper, the uncertainties of the parameters are projected into a criteria space in order to support the decision to be made on the basis of a pareto-optimal problem. Simulations with uncertainties support the robust suspension design. It is shown that controlled suspension parameters remain uncertain due to the unpredictable decisions made by the driver.