Browsing by Author "Schiehlen, Werner"

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Open Access
Active versus passive control of vehicle suspensions - hardware in the loop experiments
(1994) Rieger, Karl-Josef; Schiehlen, Werner
Hardware-in-the-loop simulation is shown to be a valuable tool for designing and testing controllers for active vehicle suspensions. The vehicle is modeled as a multibody system, whereas the electronic and hydraulic parts of the suspension are actuated on a test bed. A comparison between an active and a passive suspension shows higher performance of the active suspension with respect to low frequency excitation.
Open Access
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.
Open Access
An approach to the problem of closure in non-linear stochastic mechanics
(1994) Nguyen Dong Anh; Schiehlen, Werner
An approach combining the method of moment equations and the statistical linearization technique is proposed for analysis of the response of non-linear mechanical systems to random excitation. The adaptive statistical linearization procedure is developed for obtaining a more accurate mean square of responses. For these, a Duffing oscillator and an oscillator with cubic non-linear damping subject to white noise excitation are considered. It is shown that the adaptive statistical linearization proposed yields good accurate results for both weak and strong non-linear stochastic systems.
Open Access
Balancing on the road
(1992) Eismann, Wolfgang; Schiehlen, Werner
Modern passenger cars are equipped with measurement technology to control the function of engine and different safety systems. In addition, the requirement for improved ride comfort is growing which means that the vibrations of the vehicle has to be minimized. One source of vibrations are unbalanced rotating parts of the vehicle due to wheels and drive shafts. To compensate such unbalances the present technology is based on measurements off the road and the dynamic behaviour of the vehicle system is not taken into account. This paper presents a method based on the parameter identification of a multibody system model of the vehicle to determine the value and angular location of compensation weights for the wheels to achieve an overalJ compensation of harmonically excited vibrations on the road. Thus, the complete dynamic vehicle system driving on its rolling wheels is taken into account.
Open Access
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.
Open Access
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.
Open Access
CAD modeling, multibody system formalisms and visualization : an integrated approach
(1993) Daberkow, Andreas; Kreuzer, Edwin; Leister, Günter; Schiehlen, Werner
In this paper an integrated approach of CAD (Computer Aided Design) modeling, generation of equations of motion, simulation and visualization of multibody systems is described. An object-oriented data model for different multibody formalisms is integrated in a commercially available CAD-3D-system. With respect to existing CAD-interfaces, different solid model design methods and various visualization demands the datamodel allow, multi body modeling with a direct interface to a data base. Different software tools like an integrated Newton-Euler formalism are able to use immediately the parametrized multi body system data base. For multibody systems with closed kinematic loops a set of ordinary differential equations and decoupled algebraic equations is formulated automatically which can be solved with explicit multistep integration algorithms. This is achieved by a minimal set of generalized coordinates being specified during the numerical integration. A additional interface provides data for visualization from the simulation tool.
Open Access
Closing conditions and reaction forces of multibody systems
(1992) Schiehlen, Werner; Blajer, Wojciech
Over the years a considerable effort has been focused on the development of methods and computational algorithms for mathematical modelling and simulation of multibody systems. The methods are mainly concerned with effective formulation and numerical treatment of the dynamical equations of a general multibody system.
Open Access
A concept for motion control of biped impactless walk
(1992) Blajer, Wojciech; Schiehlen, Werner
An approach for modelling a biped impactless walk and for determining the control ensuring the realization of the reference motion is proposed. In order to avoid impacts, botb the motion of the biped and some ground reactions on it are specified appropriately, yielding a combined motion and force control ploblem. A concept is given for synthesizing a nominal (feedforward) control and and for designing a feedback controller. Finally, a short discussion on effective formulation of motion specifications and on an on-line control concept is provided. The impactless planar walking of a seven-link biped serves as an illustration.
Open Access
Concept, development and implementation of DAMOS-C: the object orientied approach to multibody systems
(1994) Daberkow, Andreas; Schiehlen, Werner
The increasing use of computer aided design (CAD)and multibody dynamics software in engineering design and analysis requires an efficient communication management between different codes. As product cycle times are shrinking and companies are under competitive pressure, an automation of the model data exchange between CAD and multibody dynamics is urgently demanded. In this paper the concept. development and implementation of the independent, object-oriented multibody modeling kernel DAMOS-C is presented. According to the different multibody formalisms, computer codes and applications in vehicle, machine and robot dynamics a general description and organization of multibody system data is introduced. A general data model is developed to fulfill the needs of a modular simulation system based upon numerical and symbolical formalisms. With respect to existing CAD interfaces, different solid model construction methods and visualization procedures, multibody system classes and methods are implemented in the multibody modeling kernel. The extreme versatility of this modeling kernel is shown by an integration in a commercially available CAD-system and by application to a conversion tool which processes input data for different multibody software codes.
Open Access
DAMOS-C ein neutrales Datenformat zur standardisierten Anbindung von MKS an Simulationssysteme mit offener Systemarchitektur
(1994) Thomson, Bernd; Neerpasch, Uwe; Schiehlen, Werner
Der Arbeitskreis "Simulation der Systemdynamik des Fahrzeuges in der deutschen Automobilindustrie" der Firmen AUDI, BMW, MB/DB, Porsche und VW hat ein Simulationskonzept mit weitgehend offener Systemarchitektur zur Behandlung dynamischer Vorgänge im Fahrzeug erarbeitet. Grundgedanke dabei war, ein flexibles und sehr allgemein für alle Fragestellungen im Bereich mechatronischer Systeme einsetzbares Simulationswerkzeug auf Basis voneinander unabhängiger, kommerziell verfügbarer Software-Bausteine zur rechnergestützten Modellbildung mechanischer, hydraulischer und elektronischer Teilsysteme standardmäßig verfügbar zu machen. Im vorliegenden Beitrag wird am Beispiel einer prototypischen Integration der MKS-Modellerstellungssoftware, auf Basis einer im OFG-5chwerpunktprogramm "Dynamik von Mehrkörpersystemen (MKS)" entwickelten Datenkapsel DAMOS-C, die grundlegende Funktionalität dieser Vorgehensweise vorgestellt.
Open Access
Dynamic analysis of constrained multibody systems using inverse kinematics
(1993) Blajer, Wojciech; Schiehlen, Werner; Schirm, Walter
This paper draws attention to the advantages that may arise in the dynamic analysis or constrained multibody systems by applying special algorithms of inverse kinematics developed in the field or robotics. The algorithms result in explicit (recursive) relations for the arbitrary chosen dependent coordinates as functions or the remaining (independent) ones. Then analogous velocity and acceleration relations are available. Using these explicit closing condition forms, minimal-dimension governing equations of a constrained system can be formulated conveniently. The avoidance or singularities in the analysis is discussed. An illustrative example is included.
Open Access
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.
Open Access
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.
Open Access
Fahrzeugdynamik : eine Einführung in die Dynamik des Systems Fahrzeug - Fahrweg
(1993) Popp, Karl; Schiehlen, Werner
Die Fahrzeugdynamik befaßt sich mit der mechanischen Modellierung sowie der mathematischen Beschreibung und Analyse von Fahrzeugsystemen. Ziel dieses Buches ist es, eine methodenorientierte Einführung in die Dynamik landgestützter Fahrzeugsysteme zu geben. Dabei werden nicht die einzelnen Fahrzeugarten wie Kraftfahrzeuge, Schienenfahrzeuge oder Magnetschwebebahnen nebeneinander betrachtet, sondern die allen Fahrzeugsystemen gemeinsamen dynamischen Probleme unter einheitlichen Gesichtspunkten behandelt. Dies ist durch eine systemtheoretische Betrachtungsweise möglich. Die Bereitstellung aussagekräftiger mathematischer Modelle erlaubt Bewegungssimulationen und Parameterstudien lange bevor der erste Prototyp gebaut wird. Der Trend zu kürzeren Entwicklungszeiten und eine große Variantenvielfalt verlangen heute vom Ingenieur umfassende Berechnungen, für die dieses Buch die Grundlagen vermitteln soll.
Open Access
Fuzzy control of speed limiter
(1993) Thurn, V. M.; Schäfer, Peter; Schiehlen, Werner
Future regulations of the European Community (EC) require a speed control for the limitation of truck speeds on the European roads. Today's speed limiters consist of an adaptive PID-controller. However, the resulting truck behaviour is not satisfactory compared to an experienced driver. Therefore, the human experience has to be used to improve the design. Some fundamental aspects for the development of a Fuzzy-Logic-Controller (FLC) for limiting the truckspeed are presented in the paper. Simulations of a controller with one and two input variables are shown. It turns out that a FLC can be interpreted as a highly nonlinear control. The resulting control law will be discussed.
Open Access
High-dynamic test bed for mechatronic vehicle suspensions
(1993) Schäfer, Peter; Schiehlen, Werner
Advanced vehicles are mechatronic systems consisting of mechanical parts like rigid bodies, flexible tires, bearings, joints, springs and dampers as well as electronic components including actuators, control devices and sensors. In particular the electronic parts have to be tested rigorously by realistic loads. For this purpose a high-dynamic hydraulic test bed for actively controlled vehicle suspensions has been developed. The timevarying loads are obtained from a real-time simulation of multibody systems equations representing the mechanical parts of the vehicle. The test bed is operating up to frequencies of 35 Hz without dynamic errors in amplitude and phase.
Open Access
Lage- und Kraftregelung strukturvariabler mechanischer Systeme
(1982) Schiehlen, Werner
Strukturvariable mechanische Systeme sind in der Fertigungstechnik und bei Transportvorgängen häufig zu finden. Eine wichtige Aufgabe besteht darin, geeignete Regelgesetze für einen sanften Bewegungsablauf ohne Kraftsprünge und Kraftimpulse (Stöße) zu finden. Es werden zunächst die Bewegungs- und Reaktionsgleichungen von Mehrkörpersystemen mit Minimalkoordinaten aufgestellt. Dann werden geeignete Regelgesetze entworfen, welche die Sollbewegung sicherstellen und kleine Störungen in den Sensorsignalen ausregeln. Die Methode wird am Beispiel einer ebenen, aus sieben starren Körpern aufgebauten Gehmaschine verdeutlicht. Der Bodenkontakt des abhebenden Fußes erweist sich als vollständig steuerbar, so daß Kraftsprünge beim Übergang von der Stützphase in die Schwingphase vermieden werden können. Der auftretende Fuß erreicht den Boden ohne Stoß.
Open Access
Local and global stability of a piecewise linear oscillator
(1992) Kleczka, Michael; Kreuzer, Edwin; Schiehlen, Werner
Machines and mechanisms with moving parts, subjected to periodic excitation, often show unexpected dynamic behaviour, and impacts due to their connection clearances may occur. The most simple mathematical model is a one degree-of-freedom nonlinear oscillator governed by a piecewise linear symmetric function to describe the restoring force. The systems response, which can be quite rich and complicated, is described in detail. Modern methods for a combined analytical and numerical analysis are used to study local and global bifurcation conditions, coexisting solutions and their associated domains of attraction.
Open Access
Modelling of mechatronic systems by an object-oriented data model
(1994) Neerpasch, Uwe; Schiehlen, Werner
An object oriented data model is defined to describe multibody systems. Extensions for modelIing mechatronic elements like sensors and actuators within the multibody system as well as interfaces to other dynamic systems have been developed. An implementation in a neutral modelIing kernel and a format to store the description of a multibody system on a data exchange file are directly derived from this data model. Data converters transfer these data to several multibody formalism.