References of "Bruls, Olivier"
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See detailComputer-aided integrated design for mechatronic systems with configuration-dependent dynamics
da Silva, Maira M; Bruls, Olivier ULg; Desmet, Wim et al

Conference (2008, May)

Mechatronics deals with the integrated design of a mechanical system and its control system. Moreover, a large number of mechatronic systems may have their natural frequencies and mode shapes dependent on ... [more ▼]

Mechatronics deals with the integrated design of a mechanical system and its control system. Moreover, a large number of mechatronic systems may have their natural frequencies and mode shapes dependent on their spatial configuration, which inevitably affects the performance and the stability of the control system. In particular, mechatronic systems, such as machine tools and pick-and-place robots, can be classified as systems with configuration-dependent dynamics, since the relative motion between their flexible components can lead to time-varying boundary conditions. A parametric model able to capture this behavior is proposed using finite element based flexible multibody method. A global modal parameterization is applied for model-order reduction. A linear parameter varying model is derived from these reduced models and can be used in a control design scheme. This methodology is applied to a pick-and-place assembly robot with a gripper carried by a flexible beam (Fig. 1a). Vibrations, which depend on the beam length, decrease the throughput of the machine (Fig. 1b). Linear time invariant and linear parameter varying control strategies are evaluated using the derived linear parameter varying model. [less ▲]

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See detailModelling, simulation and control of flexible multibody systems
Bruls, Olivier ULg; Cardona, Alberto; Géradin, Michel ULg

in Arnold, Martin; Schiehlen, Werner (Eds.) Simulation Techniques in Applied Dynamics (2008)

This chapter concerns the dynamic analysis of flexible multibody systems. After a brief review of the inertial frame, the corotational frame and the floating frame approaches, a general simulation ... [more ▼]

This chapter concerns the dynamic analysis of flexible multibody systems. After a brief review of the inertial frame, the corotational frame and the floating frame approaches, a general simulation framework is presented in detail. Based on the finite element concept, the proposed approach allows the coupled analysis of dynamic systems composed of rigid and flexible bodies, kinematic joints and control elements. The text is illustrated with some didactic examples and industrial applications. [less ▲]

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See detailStress constrained topology and shape optimization : Specific character and large scale optimization algorithms
Duysinx, Pierre ULg; Fleury, Claude; Van Miegroet, Laurent ULg et al

in Proceedings of the 8th World Congress on Computational Mechanics (WCCM) (2008)

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See detailReduced-order modeling of electrostatically-actuated micro-beams
Durieu, Francois; Bruls, Olivier ULg; Rochus, Véronique ULg et al

in Proceedings of the 6th EUROMECH Nonlinear Dynamics Conference (ENOC) (2008)

This paper addresses the compact modeling of MEMS devices with nonlinear electromechanical forces. Ideally, the reduced-order model should only involve one or two generalized coordinates. We show that a ... [more ▼]

This paper addresses the compact modeling of MEMS devices with nonlinear electromechanical forces. Ideally, the reduced-order model should only involve one or two generalized coordinates. We show that a projection method based on the first eigenmode of the linearized unactuated structure is a good choice in terms of simplicity and accuracy. To take into account the influence of distributed electrostatic forces, it is necessary to approximate the nonlinear force in terms of the reduced coordinate. It is shown that a Pad´e approximation of order 2 is very attractive in terms of accuracy and numerical efficiency. [less ▲]

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See detailOn the numerical damping of time integrators for coupled mechatronic systems
Bruls, Olivier ULg; Golinval, Jean-Claude ULg

in Computer Methods in Applied Mechanics & Engineering (2008), 197(6-8), 577-588

The generalized-alpha time integrator is considered for the simulation of mechatronic systems. In this context, the fundamental concept of numerical damping is analysed for coupled sets of first and ... [more ▼]

The generalized-alpha time integrator is considered for the simulation of mechatronic systems. In this context, the fundamental concept of numerical damping is analysed for coupled sets of first and second-order differential-algebraic equations. First, it appears that the algebraic variables do not influence the spectral properties of the dynamic variables. Second, we demonstrate that the coupling between the dynamic variables does not influence the high-frequency spectral response, so that the numerical damping can be determined as usual from elementary characteristic polynomials. Those results are exploited to assess the stability properties of the scheme and to select an algorithm with optimal damping properties. [less ▲]

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See detailSensitivity analysis for dynamic mechanical systems with finite rotations
Bruls, Olivier ULg; Eberhard, Peter

in International Journal for Numerical Methods in Engineering (2008), 74(13), 1897-1927

This paper presents a sensitivity analysis for dynamic systems with large rotations using a semi-analytical direct differentiation technique. The choice of a suitable time integration strategy for the ... [more ▼]

This paper presents a sensitivity analysis for dynamic systems with large rotations using a semi-analytical direct differentiation technique. The choice of a suitable time integration strategy for the rotation group appears to be critical for the development of an efficient sensitivity analysis. Three versions of the generalized-alpha time integration scheme are considered: a residual form, a linear form, and a geometric form. Their consistency is discussed, and we show that the residual form, which is the most direct extension of the generalized-alpha algorithm defined in structural dynamics, should not be used for problems with large rotations. The sensitivity analysis is performed and close connections are highlighted between the structure of the sensitivity equations and of the linearized dynamic equations. Hence, algorithms developed for the original problem can be directly reused for the sensitivities. Finally, a numerical example is analysed in detail. [less ▲]

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See detailThe generalized-alpha scheme as a linear multistep integrator: Toward a general mechatronic simulator
Bruls, Olivier ULg; Arnold, Martin

in Journal Of Computational And Nonlinear Dynamics (2008), 3(4), 041007

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller ... [more ▼]

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller dynamics; and kinematic constraints. The theoretical background relies on the analogy with linear multistep formulas, which leads to elegant results related to consistency, order conditions for constant and variable step-size methods, as well as global convergence. Those results are illustrated for a controlled spring-mass system, and the method is also applied for the simulation of a vehicle semi-active suspension. [less ▲]

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See detailMultiphysics modeling and optimization of mechatronic multibody systems
Samin, Jean-Claude; Bruls, Olivier ULg; Collard, Jean-François et al

in Multibody System Dynamics (2007), 18(3), 345-373

Modeling mechatronic multibody systems requires the same type of methodology as for designing and prototyping mechatronic devices: a unified and integrated engineering approach. Various formulations are ... [more ▼]

Modeling mechatronic multibody systems requires the same type of methodology as for designing and prototyping mechatronic devices: a unified and integrated engineering approach. Various formulations are currently proposed to deal with multiphysics modeling, e.g., graph theories, equational approaches, co-simulation techniques. Recent works have pointed out their relative advantages and drawbacks, depending on the application to deal with: model size, model complexity, degree of coupling, frequency range, etc. This paper is the result of a close collaboration between three laboratories, and aims at showing that for "non-academic" mechatronic applications (i.e., issuing from real industrial issues), multibody dynamics formulations can be generalized to mechatronic systems, for the model generation as well as for the numerical analysis phases. Model portability being also an important aspect of the work, they must be easily interfaced with control design and optimization programs. A global "demonstrator", based on an industrial case, is discussed: multiphysics modeling and mathematical optimization are carried out to illustrate the consistency and the efficiency of the proposed approaches. [less ▲]

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See detailConvergence of the generalized-alpha scheme for constrained mechanical systems
Arnold, Martin; Bruls, Olivier ULg

in Multibody System Dynamics (2007), 18(2), 185-202

A variant of the generalized-alpha scheme is proposed for constrained mechanical systems represented by index-3 DAEs. Based on the analogy with linear multistep methods, an elegant convergence analysis is ... [more ▼]

A variant of the generalized-alpha scheme is proposed for constrained mechanical systems represented by index-3 DAEs. Based on the analogy with linear multistep methods, an elegant convergence analysis is developed for this algorithm. Second-order convergence is demonstrated both for the generalized coordinates and the Lagrange multipliers, and those theoretical results are illustrated by numerical tests. [less ▲]

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See detailTopology Optimization of Structural Components Included in Flexible Multibody Systems
Bruls, Olivier ULg; Lemaire, Etienne ULg; Eberhard, Peter et al

in Proceedings of the 7th World Congress on Structural and Multidisciplinary Optimization (2007, May)

This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. Generally, topology optimization techniques consider that the structural ... [more ▼]

This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. Generally, topology optimization techniques consider that the structural component is isolated from the rest of the mechanism and use simplified quasi-sta tic load cases to mimic the complex loadings in service. In contrast, this paper proposes an optimization procedure based on the dynamic simulation of the full multibody system with large amplitude motions and elastic deflections. We show that the simulation model, which involves a nonlinear finite element formulation, a time integration scheme and a sensitivity analysis, can be efficiently exploited in an optimization loop. The method is applied to truss structural components. Each truss is represented by a structural universe of beams with a topology design variable attached to each one. A SIMP model (or a variant of the power law) is used to penalize intermediate densities. The optimization formulation is stated as the minimization of the mean compliance over a time period or as the minimization of the mean tip deflection during a given trajectory, subject to a volume constraint. In order to illustrate the benefits of the integrated design approach, the case of a two degrees-of-freedom robot arm is developed. [less ▲]

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See detailFrom flexible multibody dynamics to mechatronics: Modelling, simulation and optimization
Bruls, Olivier ULg

Scientific conference (2007, April 25)

In this talk, three research topics, which are related with multibody dynamics, are presented: - simulation of mechatronic systems, with an application to a semi-active suspension, - model reduction ... [more ▼]

In this talk, three research topics, which are related with multibody dynamics, are presented: - simulation of mechatronic systems, with an application to a semi-active suspension, - model reduction techniques for the design of motion and vibration controllers, with an application to a lightweight manipulator, - topology optimization of structural components of mechanisms. Let us mention that those developments have been implemented in the Oofelie finite element software. [less ▲]

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See detailSensitivity analysis for dynamic systems with finite rotations
Bruls, Olivier ULg

Scientific conference (2007, February 22)

Optimisation methods usually require efficient algorithms to compute the sensitivities of the simulation results with respect to design parameters. Compared to finite difference schemes, the direct ... [more ▼]

Optimisation methods usually require efficient algorithms to compute the sensitivities of the simulation results with respect to design parameters. Compared to finite difference schemes, the direct differentiation technique that is considered in this talk leads to a significant reduction in the computational cost of the sensitivities. Our personal contribution is related with the treatment of large rotations, which arise for instance in multibody systems. Several time integrators are developed in order to compute the sensitivities together with the original solution in a single but extended simulation. In particular, three formulations of the generalized-alpha method are discussed and compared for a simple benchmark : a residual form, a linear form, and a geometric form. [less ▲]

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See detailComputer-aided analysis of rigid and flexible multibody systems
Verlinden, Olivier; Bruls, Olivier ULg; Conti, Calogero et al

Learning material (2007)

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See detailTransfer matrix modeling of hydraulically actuated flexible robots
Krauss, Ryan; Book, Wayne J; Bruls, Olivier ULg

in International Journal of Fluid Power (2007), 8(1), 51-57

Accurate models of hydraulic motors and their interaction with flexible structures are needed to design motion control and vibration suppression schemes for hydraulically actuated flexible robots. The ... [more ▼]

Accurate models of hydraulic motors and their interaction with flexible structures are needed to design motion control and vibration suppression schemes for hydraulically actuated flexible robots. The modeller of such a system faces significant challenges including capturing the dynamics of the actuator, integrating the actuator model into the system model, incorporating distributed parameter elements into the system model, determining any unknown model parameters, and creating a model that is useful for control design. This paper presents a model that overcomes all of these challenges. A transfer matrix model of a hydraulic actuator interacting with a flexible robot is developed. This model is integrated into a system model for a flexible robot. The model captures the interaction between the actuator and the structure and has been experimentally validated. [less ▲]

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See detailConvergence of the generalized-alpha scheme for constrained mechanical systems
Arnold, Martin; Bruls, Olivier ULg

Report (2007)

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See detailThe global modal parameterization for non-linear model-order reduction in flexible multibody dynamics
Bruls, Olivier ULg; Duysinx, Pierre ULg; Golinval, Jean-Claude ULg

in International Journal for Numerical Methods in Engineering (2007), 69(5), 948-977

In flexible multibody dynamics, advanced modelling methods lead to high-order non-linear differential-algebraic equations (DAEs). The development of model reduction techniques is motivated by control ... [more ▼]

In flexible multibody dynamics, advanced modelling methods lead to high-order non-linear differential-algebraic equations (DAEs). The development of model reduction techniques is motivated by control design problems, for which compact ordinary differential equations (ODEs) in closed-form are desirable. In a linear framework, reduction techniques classically rely on a projection of the dynamics onto a linear subspace. In flexible multibody dynamics, we propose to project the dynamics onto a submanifold of the configuration space, which allows to eliminate the non-linear holonomic constraints and to preserve the Lagrangian structure. The construction of this submanifold follows from the definition of a global modal parameterization (GMP): the motion of the assembled mechanism is described in terms of rigid and flexible modes, which are configuration-dependent. The numerical reduction procedure is presented, and an approximation strategy is also implemented in order to build a closed-form expression of the reduced model in the configuration space. Numerical and experimental results illustrate the relevance of this approach. Copyright (c) 2006 John Wiley [less ▲]

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See detailDirect differentiation of time integrators for multibody systems with absolute rotations
Bruls, Olivier ULg; Eberhard, Peter

in Proceedings of the ECCOMAS Thematic Conference - Multibody Dynamics 2007 (2007)

Gradient-based optimization methods require efficient algorithms to compute the sensitivities of the simulation results with respect to design parameters. Compared to finite difference schemes, the direct ... [more ▼]

Gradient-based optimization methods require efficient algorithms to compute the sensitivities of the simulation results with respect to design parameters. Compared to finite difference schemes, the direct differentiation technique leads to a significant reduction in the computational cost of the sensitivities while keeping a good accuracy. In particular, this paper focuses on the optimization of multibody systems with large rotations. In this framework, two versions of the generalized-alpha time integration scheme are considered: the first one is based on a parameterized treatment of the rotations, whereas the second one is formulated in a geometric setting. We show that the sensitivity analysis is much simpler and computationally more efficient in the second case than in the first case. The performance of both algorithms is compared for a numerical example. [less ▲]

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See detailThe generalized-alpha scheme as a linear multistep integrator: Towards a general mechatronic simulator
Bruls, Olivier ULg; Arnold, Martin

in Proceedings of the ASME 2007 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (2007)

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller ... [more ▼]

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller dynamics, and kinematic constraints. The theoretical background relies on the analogy with linear multistep formulae, which leads to elegant results related with consistency, order conditions for constant and variable stepsize methods, as well as global convergence. The algorithm is applied for the simulation of a vehicle semi-active suspension. [less ▲]

Detailed reference viewed: 48 (1 ULg)