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A comparison of DAE integrators in the context of benchmark problems for flexible multibody dynamics
Peter Betsch,Christian Becker,Marlon Franke,Yinping Yang,Alexander Janz 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.7
In the present work a uniform framework for general flexible multibody dynamics is used to compare state-of-the-art DAE integratorsin the context of benchmark problems. The multibody systems considered herein are comprised of rigid bodies, nonlinear beams andshells. The constitutive laws applied in the benchmark problems belong to the class of hyperelastic materials. To numerically integratethe uniform set of DAEs three alternative time-stepping schemes are applied: (i) an energy-momentum consistent method, (ii) a specificvariational integrator and (iii) a generalized-α scheme.
Numerical integration of discrete mechanical systems with mixed holonomic and control constraints
Peter Betsch,Mahmud Quasem,Stefan Uhlar 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.4
The present work aims to incorporate control (or servo) constraints into finite-dimensional mechanical systems subject to holonomic constraints. In particular, we focus on underactuated systems, defined as systems in which the number of degrees of freedom exceeds the number of inputs. The corresponding equations of motion can be written in the form of differential-algebraic equations (DAEs) with a mixed set of holonomic and control constraints. Apart from closed-loop multibody systems, the present formulation accommodates the so-called rotationless formulation of multibody dynamics. The rotationless formulation has proven to be especially well-suited for the design of energy and momentum conserving schemes, which typically exhibit superior numerical stability properties (see [4, 7, 10]). Subsequent to the incorporation of the servo constraints, we deal with a reformulation of the underlying DAEs, which is amenable to a direct numerical discretization. To this end, we apply a specific projection method to the DAEs in terms of redundant coordinates. A similar projection approach has been previously developed in the framework of generalized coordinates by Blajer & Kolodziejczyk [12]. A numerical example is presented, which deals with a 3D rotary crane.
Energy-consistent integration of multibody systems with friction
Stefan Uhlar,Peter Betsch 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.4
The main goal of the present contribution is to establish an energy consistent time integration procedure for multibody systems with friction. Based upon a rotationless formulation for multibody systems, we use the coordinate augmentation technique in order to implement frictional phenomena such as joint friction. Within this contribution we use the viscous friction assumption as a classical friction model incorporated in the joints. We start with a classical ad hoc model for damping and extend the formulation to multibody systems, dealing finally with an underactuated control problem of a three bar linkage with applied joint friction.