References of "Bruls, Olivier"
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See detailThe generalized-alpha method in mechatronic applications
Bruls, Olivier ULg; Golinval, Jean-Claude ULg

in ZAMM-Zeitschrift fur Angewandte Mathematik und Mechanik (2006), 86(10 Sp. Iss. SI), 748-758

This paper presents an extension of the generalized-a time-integrator to mechatronic systems represented by coupled first and second-order DAEs. A simple reformulation of those equations as full second ... [more ▼]

This paper presents an extension of the generalized-a time-integrator to mechatronic systems represented by coupled first and second-order DAEs. A simple reformulation of those equations as full second-order DAEs allows the implementation of a monolithic integration scheme, so that the numerical dissipation properties are preserved, and second-order accuracy is obtained at least in the unconstrained case. The algorithmic parameters can be optimized either for the mechanical or the control subsystem. Two illustrative applications are treated in the fields of vehicle dynamics and robotics. [less ▲]

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See detailConcurrent simulation of mechatronic systems with variable mechanical configuration
da Silva, Maira M; Bruls, Olivier ULg; Paijmans, Bart et al

in Proceedings of ISMA 2006 (2006, September)

The dynamic behavior of a mechatronic system may be largely dependent on the mechanical configuration. This inevitably affects the performance and the stability of any controller designed using the ... [more ▼]

The dynamic behavior of a mechatronic system may be largely dependent on the mechanical configuration. This inevitably affects the performance and the stability of any controller designed using the classical linear control theory. Major improvements are expected if the controller is designed using the theory of linear parameter varying systems, but one difficulty is then to provide a low-order model which captures the configuration-dependent dynamics. This paper presents a methodology to build such a model in two steps: for several representative configurations, a local linear model is derived, the parameter- dependent model is constructed by interpolation in the configuration space. Moreover, a co-simulation methodology is proposed for mechatronic systems by combining LMS Virtual.Lab Motion and Matlab/Simulink. The methodology is applied to an industrial pick-and-place machine. [less ▲]

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See detailAn extended flexible multibody dynamics software for mechatronic applications
Bruls, Olivier ULg; Duysinx, Pierre ULg; Golinval, Jean-Claude ULg

in Proceedings of ISMA 2006 (2006, September)

This paper presents some extensions of flexible multibody formalisms for mechatronic applications. The software implementation is realized in a general purpose finite element code, and three specific ... [more ▼]

This paper presents some extensions of flexible multibody formalisms for mechatronic applications. The software implementation is realized in a general purpose finite element code, and three specific subjects are discussed: (i) nonlinear model reduction techniques for flexible multibody systems, (ii) integrated modelling of mechatronic systems, (iii) time-integration algorithms for coupled problems. The relevance of those developments are demonstrated for the dynamic analysis and the control design of an experimental lightweight manipulator. [less ▲]

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See detailMultiphysics modeling of mechatronic multibody systems
Fisette, Paul; Bruls, Olivier ULg; Swevers, Jan

in Proceedings of ISMA 2006 (2006, September)

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 Belgian 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 applications, 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, control design and mathematical optimization are carried out to illustrate the consistency and the efficiency of the proposed approaches. [less ▲]

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See detailFlexible mechatronic systems: Time integration and sensitivity analysis
Bruls, Olivier ULg

Scientific conference (2006, July)

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See detailOn the implementation of a sensitivity analysis in a flexible multibody dynamics environment
Bruls, Olivier ULg; Duysinx, Pierre ULg; Eberhard, Peter

Conference (2006, June)

The dynamic performance of complex mechanisms, such as machine tools, manipulators, vehicles, engines or foldable structures, can be strongly affected by flexible phenomena. Therefore, the deformation ... [more ▼]

The dynamic performance of complex mechanisms, such as machine tools, manipulators, vehicles, engines or foldable structures, can be strongly affected by flexible phenomena. Therefore, the deformation effects should be considered as soon as possible in the design procedure, which motivates the development of automatic optimization techniques for flexible multibody systems. Advanced software tools are able to simulate the dynamic behaviour of such systems, but they typically involve extensive numerical treatments. Hence, gradient-based optimization methods are of special interest since they require a quite low number of simulations, but an important problem is to obtain the sensitivities of the objective function with respect to the design parameters. Since finite difference approaches lack robustness and computational efficiency, we propose to investigate analytical or semi-analytical sensitivity analysis. Several difficulties are inherent to the simulation of flexible mechanisms. A consistent geometric formulation is necessary to describe large amplitude motion as well as possible large deformations. Here, according to the nonlinear finite element formulation, the motion is parameterized using absolute nodal coordinates, and an updated Lagrangian point of view is adopted for the rotation parameters. The joints and the rigid-body conditions are represented by algebraic constraints between the nodal coordinates, leading to differential algebraic equations of motion (DAEs). Finally, the computation of the trajectories requires a reliable simulation algorithm for nonlinear DAEs. A strong advantage of the finite element method comes from its very systematic implementation, which facilitates the development of a semi-analytical sensitivity analysis. In this work, sensitivity analysis is performed for beam elements, rigid bodies and ideal joints. The global sensitivity is then obtained by numerical assembly of the elementary contributions and by integration in the time domain. Thus, a single but extended simulation is sufficient to compute the sensitivities with respect to all parameters. In order to illustrate the method and to demonstrate its efficiency, we consider the optimal design of a car engine, where the flexibility of the connecting rods between the crankshaft and the pistons is taken into account. The objective is to find a feasible mechanical design which minimizes the level of vibrations. [less ▲]

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See detailThe generalized-alpha time-integration scheme for mechatronic systems with elastic components
Bruls, Olivier ULg

Conference (2006, May)

This talk concerns the numerical simulation of mechatronic systems, such as robots, machine-tools or modern vehicles. In general, a mechatronic system is composed of various technological components: a ... [more ▼]

This talk concerns the numerical simulation of mechatronic systems, such as robots, machine-tools or modern vehicles. In general, a mechatronic system is composed of various technological components: a mechanism, actuators, sensors, and control units. For critical applications, it is also necessary to account for elastic deformations in the mechanism. The generalized-alpha method has been initially developed for the dynamic simulation of flexible mechanical structures, which are represented by lightly damped second-order ODEs. Usually, those equations are obtained after a finite element spatial discretization, with the consequence that they are affected by a large number of high-frequency modes with a purely numerical origin. The generalized-alpha method has very interesting properties in this context, such as an adjustable amount of high-frequency numerical dissipation, A-stability, second-order accuracy, and a high level of computational efficiency. A mechanism with elastic components can be described using the nonlinear finite element formalism. Due to the presence of kinematic constraints, the equations of motion are second-order DAEs, and we shall consider the generalized-alpha method for the direct simulation of the index-3 problem. In particular, some results about the convergence and the stability of the algorithm will be discussed. Finally, a mechatronic system involves mechanical and non-mechanical components, and it is thus modelled as a mixed set of second- and first-order DAEs. We will show that those coupled equations of motion can also be solved in the time domain according to the generalized-alpha scheme. An important problem is then associated with the selection of the parameters of the method. The presentation will be illustrated by academic and non-academic applications, for example in vehicle dynamics and in robotics. [less ▲]

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See detailA model reduction method for the control of rigid mechanisms
Bruls, Olivier ULg; Duysinx, Pierre ULg; Golinval, Jean-Claude ULg

in Multibody System Dynamics (2006), 15(3), 213-227

This paper presents a reduction method to build closed-form dynamic equations for rigid multibody systems with a minimal kinematic description. Relying on an initial parameterization with absolute ... [more ▼]

This paper presents a reduction method to build closed-form dynamic equations for rigid multibody systems with a minimal kinematic description. Relying on an initial parameterization with absolute displacements and rotations, the method is able to tackle complex topologies with closed-loops in a systematic way and its extension to flexible multibody systems will be investigated in the future. Thus, it would be of great use in the framework of model-based control of mechanisms. The method is based on an interpolation strategy. The initial model is built and reduced for a number of selected points in the configuration space. Then, a piecewise polynomial model is adjusted to match the collected data. After the presentation of the reduction procedure and of the interpolation strategy, two applications of the reduction method are considered: a four-bar mechanism and a parallel kinematic machine-tool called "Orthoglide". [less ▲]

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See detailReduced-order modeling of flexible mechanisms
Bruls, Olivier ULg

Conference (2005, September)

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See detailReduced-order modeling of flexible mechanisms with configuration-dependent dynamics: a modal approach
Bruls, Olivier ULg

Conference (2005, September)

Modern formalisms in multibody dynamics allow a detailed and reliable representation of complex mechanical systems. However, high levels of accuracy and generality can only be reached at the price of more ... [more ▼]

Modern formalisms in multibody dynamics allow a detailed and reliable representation of complex mechanical systems. However, high levels of accuracy and generality can only be reached at the price of more sophisticated models, which require increased computational resources. Reduction techniques have thus been developed in order to build simplified models able to capture the essential dynamics of a flexible mechanism. In this talk, a methodology is proposed to transform an initial high-order Finite Element model into a low-order and explicit model. The reduction method is an extension of the component-mode technique established in linear structural dynamics, which accounts for the nonlinear kinematics of the mechanism. It relies on the original concept of “Global Modal Parameterization”: the motion of the assembled mechanism is described in terms of rigid and flexible modes, which depend on the mechanical configuration. We will show that the reduction procedure leads to a consistent model, with configuration-dependent parameters. The nonlinear variations of those parameters are approximated using a piecewise polynomial interpolation. This strategy is based on an adaptive configuration space inspection algorithm, which minimizes the computational resources to satisfy a specification on the approximation error. Several examples will be considered in the presentation: a four-bar mechanism, a parallel kinematic machine-tool, and a lightweight manipulator. [less ▲]

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See detailA unified finite element framework for the dynamic analysis of controlled flexible mechanisms
Bruls, Olivier ULg; Duysinx, Pierre ULg; Golinval, Jean-Claude ULg

in Proceedings of the ECCOMAS Conference on Advances in Computational Multibody Dynamics (2005, June)

This paper proposes a unified formalism for the simulation of mechatronic systems with complex flexible mechanisms. The equations of motion are formulated using a nonlinear Finite Element approach for the ... [more ▼]

This paper proposes a unified formalism for the simulation of mechatronic systems with complex flexible mechanisms. The equations of motion are formulated using a nonlinear Finite Element approach for the mechanism, and the block diagram language for the control system. The set of strongly coupled equations of motion is constructed numerically, and integrated in the time domain using the generalized-alpha method. Convergence and stability properties are thus guaranteed for the simulation algorithm. Two illustrative examples are treated in the fields of vehicle dynamics and robotics respectively. [less ▲]

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See detailOptimization of mechatronic systems: application to a modern car equipped with a semi-active suspension
Duysinx, Pierre ULg; Bruls, Olivier ULg; collard, Jean-François et al

in Herskowitz, José (Ed.) Proceedings of the 6th World Congress of Structural and Multidisciplinary Optimization (WCSMO6) (2005, May)

The research aims at developing a global mechatronic approach to model, simulate and optimize complex industrial applications. The approach is illustrated with the simulation and the optimization of a ... [more ▼]

The research aims at developing a global mechatronic approach to model, simulate and optimize complex industrial applications. The approach is illustrated with the simulation and the optimization of a modern car (an Audi A6) equipped with a controlled semi-active suspension. An optimization procedure is used to find the best sub-system parameters in order to improve the comfort of the passengers while preserving the car ride and handling performances. Two different modeling and optimization approaches are used and compared. The first one is realized in the MATLAB-SIMULINK environment and is based on a symbolic multibody model of the chassis while the hydraulic actuators, and the controller are integrated using S-functions. Optimization is also carried out in MATLAB using algorithms available in MATLAB libraries, especially a genetic algorithm (GA). On the other hand, the second approach relies on a multibody model based on the Finite Element method whereas the optimization can be realized with an industrial open optimization tool. [less ▲]

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See detailIntegrated Simulation and Reduced-Order Modeling of Controlled Flexible Multibody Systems
Bruls, Olivier ULg

Doctoral thesis (2005)

A mechatronic system is an assembly of technological components, such as a mechanism, sensors, actuators, and a control unit. Recently, a number of researchers and industrial manufacturers have ... [more ▼]

A mechatronic system is an assembly of technological components, such as a mechanism, sensors, actuators, and a control unit. Recently, a number of researchers and industrial manufacturers have highlighted the potential advantages of lightweight parallel mechanisms with respect to the accuracy, dynamic performances, construction cost, and transportability issues. The design of a mechatronic system with such a mechanism, requires a multidisciplinary approach, where the mechanical deformations have to be considered. This thesis proposes two original contributions in this framework. First, a modular and systematic method is developed for the integrated simulation of mechatronic systems, which accounts for the strongly coupled dynamics of the mechanical and non-mechanical components. The equations of motion are formulated using the nonlinear Finite Element approach for the mechanism, and the block diagram language for the control system. The time integration algorithm relies on the generalized-alpha method, known in structural dynamics. Hence, well-defined concepts from mechanics and from system dynamics are combined in a unified formulation, with guaranteed convergence and stability properties. Several applications are treated in the fields of robotics and vehicle dynamics. Usual methods in flexible multibody dynamics lead to complex nonlinear models, not really suitable for control design. Therefore, a systematic nonlinear model reduction technique is presented, which transforms an initial high-order Finite Element model into a low-order and explicit model. The order reduction is obtained using the original concept of Global Modal Parameterization: the motion of the assembled mechanism is described in terms of rigid and flexible modes, which have a global physical interpretation in the configuration space. The reduction procedure involves the component-mode technique and an approximation strategy in the configuration space. Two examples are presented: a four-bar mechanism, and a parallel kinematic machine-tool. Finally, both simulation and modeling tools are exploited for the dynamic analysis and the control design of an experimental lightweight manipulator with hydraulic actuators. A Finite Element model is first constructed and validated with experimental data. A reduced model is derived, and an active vibration controller is designed on this basis. The simulation of the closed-loop mechatronic system predicts remarkable performances. The model-based controller is also implemented on the test-bed, and the experimental results agree with the simulation results. The performances and the other advantages of the control strategy demonstrate the relevance of our developments in mechatronics. [less ▲]

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See detailTwo competing linear models for flexible robots: Comparison, experimental validation, and refinement
Krauss, Ryan; Bruls, Olivier ULg; Book, Wayne J

in Proceedings of the American Control Conference (2005)

The modeling of a rigid robot attached to a flexible base is addressed in this work. Two approaches are compared: the Finite Element Method (FEM) and the Transfer Matrix Method (TMM). Initially, idealized ... [more ▼]

The modeling of a rigid robot attached to a flexible base is addressed in this work. Two approaches are compared: the Finite Element Method (FEM) and the Transfer Matrix Method (TMM). Initially, idealized models of the hydraulic actuators are used that do not include flexible effects in the joints. Those models greatly overestimate the second natural frequency of the system, therefore the identification of local flexibilities in the joints is pursued to improve the results. The very good agreement between both approaches, and their ability to represent the physical system (once joint flexibility is included), confirms their efficiency and relevance in this context. [less ▲]

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See detailReduced-order modeling and control of lightweight parallel manipulators: Theory and experiments
Bruls, Olivier ULg

Scientific conference (2004, December 16)

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See detailGeneration of closed-form models for the control of flexible mechanisms: a numerical approach
Bruls, Olivier ULg; Duysinx, Pierre ULg; Golinval, Jean-Claude ULg

in Proc. of the 7th Int. Conf. on Motion and Vibration Control (MOVIC) (2004, August)

In robotics, most high performances control strategies require a closed-form representation of the mechanical dynamic behaviour. This is even more critical when significant flexible effects are to be ... [more ▼]

In robotics, most high performances control strategies require a closed-form representation of the mechanical dynamic behaviour. This is even more critical when significant flexible effects are to be considered in the control algorithm. This paper presents a method to build closed-form dynamic equations for flexible multibody systems in terms of minimal coordinates. Relying on the Finite Element (FE) formulation, the method is able to tackle complex topologies with closed-loops in a systematic way. The method is based on an interpolation strategy. For a number of selected points in the configuration space, a full Finite Element model is built and reduced according to a component mode synthesis. Then, a piecewise polynomial model is adjusted to match the collected data. In order to guarantee the continuity of the model, a mode tracking strategy is implemented. After the presentation of the reduction procedure and of the interpolation strategy, a four-bar mechanism is analyzed as an illustrative example. [less ▲]

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