Selection of component modes for flexible multibody simulation

Spanos, John T.; Tsuha, Walter S.

doi:10.2514/3.20638

Cited by 61 publications

(37 citation statements)

References 21 publications

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“…The EIM measure was developed by considering (10), from which the timedomain response of the ith fixed-interface mode to the a-set inputs can be computed as:…”

Section: Normal Modes Selectionmentioning

confidence: 99%

“…Several component mode synthesis methods have been proposed in the past [6][7][8][9], the Craig-Bampton approach being the most popular amongst the multibody dynamics community. The coordinate transformation matrix is built up in this case starting from the computation of constraint modes and fixedinterface normal modes; proper selection of the latter is a nontrivial task, and several papers exist on the subject, see, for example, [10]. In this work, the selection procedure is carried out in accordance with a modal ordering scheme based on the effective interface mass measure of dynamic importance [11,12], which ranks modes based upon their contribution to loads at component interface.…”

Section: Introductionmentioning

confidence: 99%

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Model Reduction of the Flexible Rotating Crankshaft of a Motorcycle Engine Cranktrain

Ricci

Troncossi

Rivola

2011

International Journal of Rotating Machinery

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This paper addresses the development of an elastodynamic model of a motorcycle engine cranktrain aimed at accurately evaluating the interactions between the crankshaft and the engine block, thus allowing an improved structural design. A rigid multibody model is first implemented and simulated; only kinematic joints are involved at this stage, leading to a statically determinate assembly of the mechanism. Such a modelling approach prevents the loads at certain interface locations to be evaluated; furthermore, high-frequency dynamic effects cannot be predicted. These drawbacks can be removed by introducing bushinglike elements and/or modelling component flexibility. In this paper, this latter aspect is the objective of the investigation; in particular, a finite element model of the crankshaft is implemented as a replacement for the corresponding rigid member. The well-established Craig-Bampton model reduction technique is used to represent the elastodynamic behaviour of the component with a limited number of coordinates. The mode selection procedure is emphasized here: a measure of modal dynamic importance, namely the effective interface mass fraction, is used to rank fixed-interface normal modes based upon their contribution to loads at the substructure interface; choosing the modal base according to such ranking leads to a minimal yet accurate representation.

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“…The EIM measure was developed by considering (10), from which the timedomain response of the ith fixed-interface mode to the a-set inputs can be computed as:…”

Section: Normal Modes Selectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Model Reduction of the Flexible Rotating Crankshaft of a Motorcycle Engine Cranktrain

Ricci

Troncossi

Rivola

2011

International Journal of Rotating Machinery

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“…For a more comprehensive treatment on adding constraint modes to normal modes, the textbook [15] is recommended. Indeed, the selection of a subset of component modes or assumed shape functions is an important element in substructure synthesis and the work in [17,13] is recommended for a more detail discussion.…”

Section: Substructure Modelmentioning

confidence: 99%

“…The advantages in this synergism include: (1) nominal model and uncertainties at the substructure level can be incorporated directly for control analysis and design, and (2) a class of problems involving variable stiness coupling between various structural systems can be treated conveniently. This approach allows substructure (or component mode synthesis) dynamic models (see for example [14], [15], [16], [17]) to be used directly in the analysis and design of control systems. Perhaps the major advantage in the above approach is the reduction in the dependence on on-orbit system identication testing of the assembled structure by an easier and less costly testing of substructures on the ground.…”

Section: Relation To Previous Workmentioning

confidence: 99%

Robust control design framework for substructure models

Lim

1996

Journal of Guidance, Control, and Dynamics

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SUMMARYA framework for designing control systems directly from substructure models and uncertainties is proposed. The technique is based on combining a set of substructure robust control problems by an interface stiness matrix which appears as a constant gain feedback. Variations of uncertainties in the interface stiness are treated as a parametric uncertainty. It is shown that multivariable robust control can be applied to generate centralized or decentralized controllers that guarantee performance with respect to uncertainties in the interface stiness, reduced component modes and external disturbances. The technique is particularly suited for large, complex, and weakly coupled exible structures.

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“…The idea behind Song and Haug's approach is further developed and generalized by Shabana and Wehage [2,3] that use substructuring and the mode component synthesis to reduce the number of generalized co-ordinates required to represent the exible components. According to Spanos and Tsuha [4], the selection of modes required for the component mode synthesis vaguely implies the solution of an eigenvalue problem. The methodologies proposed use a limited number of modes to represent the exible components.…”

Section: Introductionmentioning

confidence: 99%

Efficient kinematic joint descriptions for flexible multibody systems experiencing linear and non‐linear deformations

Ambrósio¹

2003

Numerical Meth Engineering

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SUMMARYDi erent ÿnite-element-based strategies used to represent the components' exibility in multibody systems lead to various sets of co-ordinates. For systems in which the bodies only experience small elastic deformations it is common to use mode component synthesis to reduce the number of generalized elastic co-ordinates and, consequently, the equations of motion are written in terms of modal co-ordinates. However, when the system components experience non-linear deformations the use of reduction methods is not possible, in general, and the ÿnite element nodal co-ordinates are the generalized co-ordinates used. Furthermore, depending on the type of ÿnite elements used to represent each exible body, the nodal co-ordinates may include all node rotations and translations or only some of each. Regardless of the type of generalized co-ordinates adopted it is required that kinematic joints are deÿned. The complete set of joints available in a general-purpose multibody code must include, for each particular type of joint, restrictions involving only rigid bodies, or only exible bodies, or exible and rigid bodies. Therefore, the e ort put into the development and implementation of any joint is at least three times as much as the initial work done in the implementation of joints with rigid bodies only. The concept of virtual bodies provides a general framework to develop general kinematic joints for exible multibody systems with minimal e ort, regardless of the exible co-ordinates used. Initially, only a rigid constraint between the exible and a massless rigid body is developed. Then, any kinematic joint that involves a exible body is set with the massless rigid body instead, using the regular joint library of the multibody code. The major drawback is that for each kinematic joint involving a exible body it is required to use six more co-ordinates per virtual body and six more kinematic constraints. It is shown in this work that for small elastic deformations, for which the mode component synthesis is applied, the use of sparse matrix solvers can compensate for the computational overhead of involving more co-ordinates and kinematic constraints in the system, due to the use of virtual bodies. For non-linear deformations, where the generalized co-ordinates are the global positions of the ÿnite-element nodes, the use of the virtual body concept does not require an increase in the number of system co-ordinates or kinematic constraints. By introducing the rigid joint between the exible body nodal co-ordinates and the virtual body, with the use of Lagrange multipliers, and then solving the equations explicitly for * Correspondence to: Jorge AmbrÃ osio, Instituto de Engenharia Mecânica (IDMEC), Instituto Superior TÃ ecnico, Av.Rovisco Pais, 1049-001 Lisboa, Portugal. † E-mail: jorge@lemac.ist.utl.pt these multipliers the resulting equations of motion for the subsystem have the same degrees of freedom as the original exible body alone. The di erence is that degrees of freedom associated to the virtual body are used as co-ordi...

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Selection of component modes for flexible multibody simulation

Cited by 61 publications

References 21 publications

Model Reduction of the Flexible Rotating Crankshaft of a Motorcycle Engine Cranktrain

Model Reduction of the Flexible Rotating Crankshaft of a Motorcycle Engine Cranktrain

Robust control design framework for substructure models

Efficient kinematic joint descriptions for flexible multibody systems experiencing linear and non‐linear deformations

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