Werner Schiehlen

Multibody systems handbook

Contents: Introduction.- Overview.- Test Examples.- Descriptions of Codes: NUBEMM.- SYM.- CAMS.- AUTOLEV.- UCIN-DYNOCOMBS.- SPACAR.- NBOD & DISCOS.- DADS.- NEWEUL.- MEDYNA.- AUTODYN & ROBOTRAN.- SIMPACK.- COMPAMM.- DYMAC & DYSPAM.- MESA VERDE.- ADAMS.- PLEXUS.- Contributors and Distributors.- Index.

Multibody System Dynamics: Roots and Perspectives

The paper reviews the roots, the state-of-the-art and perspectives of multibody system dynamics. Some historical remarks show that multibody system dynamics is based on classical mechanics and its engineering applications ranging from mechanisms, gyroscopes, satellites and robots to biomechanics. The state-of-the-art in rigid multibody systems is presented with reference to textbooks and proceedings. Multibody system dynamics is characterized by algorithms or formalisms, respectively, ready for computer implementation. As a result simulation and animation are most important. The state-of-the-art in flexible multibody systems is considered in a companion review by Shabana.Future research fields in multibody dynamics are identified as standardization of data, coupling with CAD systems, parameter identification, real-time animation, contact and impact problems, extension to control and mechatronic systems, optimal system design, strength analysis and interaction with fluids. Further, there is a strong interest on multibody systems in analytical and numerical mathematics resulting in reduction methods for rigorous treatment of simple models and special integration codes for ODE and DAE representations supporting the numerical efficiency. New software engineering tools with modular approaches promise improved efficiency still required for the more demanding needs in biomechanics, robotics and vehicle dynamics.

Ground vehicle dynamics

System Definition and Modeling.- Vehicle Models.- Models for Support and Guidance Systems.- Guideway Models.- Models for Vehicle-Guideway-Systems.- Assessment Criteria.- Computational Methods.- Longitudinal Motions.- Lateral Motions.- Vertical Motions.

Two Methods of Simulator Coupling

Modelling and simulation of complex engineering systems are often relieved by a modular approach in which the global system is decomposed into subsystems. Advantages arise from independent and parallel modelling of subsystems over easy exchange of the resulting modules to the use of different software for each module. However, the modular simulation of the global system by coupling of simulators may result in an unstable integration, if an algebraic loop exists between the subsystems. This numerical phenomenon is analyzed and two methods of simulator coupling which guarantee stability for general systems including algebraic loops are introduced. Numerical results of the modular simulation of a multibody system are presented.

Computational Dynamics of Multibody Systems: History, Formalisms, and Applications

Multibody dynamics is based on analytical mechanics and is applied to engineering systems such as a wide variety of machines and all kind of vehicles. Multibody dynamics depends on computational dynamics and is closely related to control design and vibration theory. Recent developments in multibody dynamics focus on elastic or flexible systems, respectively, contact and impact problems, and actively controlled systems. Some fundamentals in multibody dynamics, recursive algorithms and methods for dynamical analysis are presented. In particular, methods from linear system analysis and nonlinear dynamics approaches are discussed. Also, applications from vehicles, manufacturing science and molecular dynamics are shown.

Modular Simulation in Multibody System Dynamics

The dynamic analysis of complex engineering systems likeautomobiles is often relieved by a modular approach to make it treatableby a team of engineers. The modular decomposition is based onengineering intuition of corresponding engineering disciplines. In thispaper, a modular formulation of multibody systems is proposed which isbased on the block representation of a multibody system withcorresponding input and output quantities. Advantages of this modularapproach range from independent and parallel modeling of subsystems overthe easy exchange of the resulting modules to the use of differentsoftware for each module. However, the modular simulation of the globalsystem by coupling of simulators may result in an unstable integrationif an algebraic loop exists between the subsystems. This numericalphenomenon is analyzed and a method of simulator coupling whichguarantees stability for general systems including algebraic loops isintroduced. Numerical results of the modular simulation of aslider-crank mechanism are presented.

Nonlinear Dynamics in Engineering Systems

Bifurcations and chaos in a model of a rolling railway wheel-set, C. Knudsen et al mechanics of ship capsize under direct and parametric wave excitation, J.M.T. Thompson et al modern design of belt conveyors in the context of stability boundaries and chaos, A. Harrison stick-slip motion of turbine blade dampers, E. Pfeiffer and M. Hajek chaos-enhanced transport in cellular flows, S.C. Jana and J.M. Ottino local and global stability of a piecewise linear oscillator, M. Kleezka et al dynamical complexities of forced impacting systems, S. Foale and S.R. Bishop Birkhoff signature change - a criterion for the instability of chaotic resonance, F.A. McRobie.

GENERAL PURPOSE VEHICLE SYSTEM DYNAMICS SOFTWARE BASED ON MULTIBODY FORMALISMS

SUMMARY This paper pursues two objectives: Firstly, to review the state-of-the-art of general purpose vehicle system dynamics software and secondly, to describe two representatives, the program MEDYNA and the program NEWEUL. The general modeling requirements for vehicle dynamics software, the multibody system approach and a comparative discussion of multibody software are given. The two programs NEWEUL and MEDYNA are described with respect to modeling options, computational methods, software engineering as well as their interfaces to other software. The applicability of these programs is demonstrated on two selected examples, one from road vehicle problems and the other from wheel/rail dynamics. It is concluded that general purpose software based on multibody formalisms will play the same role for mechanical systems, especially vehicle systems, as finite element methods play for elastic structures.

RECURSIVE KINEMATICS AND DYNAMICS FOR PARALLEL STRUCTURED CLOSED-LOOP MULTIBODY SYSTEMS*

A kinematic formulation for the parallel structured closed-loop multibody mechanical systems, such as Stewart Platform and Hexapod machine tools, is presented in this paper, which is recursive in nature. This also leads to the minimum order representation of the dynamic equations of motion. The recursive algorithms are known for their efficiency when a system is large. They also provide many physical interpretations. On the other hand, the minimum order dynamic equations of motion are desired in control and simulation. For the latter a minimum set of dynamic equations of motion leads to a numerically stable integration algorithm that does not violate the kinematic constraints. Two recursive algorithms, one for the inverse and another for the forward dynamics, are proposed. The overall complexity of either problem is O(n) + n O(m), where n and m are the number of legs and the total number of rigid bodies in each leg, respectively. Hence the proposed formulation exploits the advantages of both minimum order representation and recursive algorithms, which earlier were available only for the open-loop systems such as serial manipulators. The method is illustrated with three examples: a one-degree-of-freedom (DOF) slider-crank mechanism, four-bar linkage, and a two-DOF five-bar planar parallel manipulator. *Communicated by J. McPhee.

Walking without impacts as a motion/force control problem

The paper deals with the synthesis of control for impactless bipedal walking. In order of avoid impulses, both the specified motion of the biped and its ground reactions are controlled, yielding a combined motion and force control problem. A method for modeling and solving such problems is proposed. and then illustrated by the example of an impactless planar walk of a seven-link bipedal robot. Some numerical results of the motion simulation are reported.