The global modal parameterization for non-linear model-order reduction in flexible multibody dynamics

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 ▲]

The generalized-alpha scheme as a linear multistep integrator: Towards a general mechatronic simulator

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 ▲]

PARTICIPATION OF ULG STUDENTS TO THE SSETI MICROSATELLITE PROGRAMME USING SAMCEF

Conference (2007)

The objective of this presentation is to discuss the participation of students at the University of Liège to the educational spacecraft project SSETI-ESEO proposed by the European Space Agency. SSETI ... [more ▼]

The objective of this presentation is to discuss the participation of students at the University of Liège to the educational spacecraft project SSETI-ESEO proposed by the European Space Agency. SSETI students are now mainly involved in the ESEO satellite for which the University of Liège is in charge of the MECH work package. The students have to propose a design for the structure of the solar panels (including the geometry and materials) and their deployment and pointing mechanisms (including electrical circuits, motors, hinges and actuators). Through detailed finite element computations in the SAMCEF software, they have to verify the structural integrity of the panels during the launch phase and to guarantee a safe deployment once on-orbit. Another task is to ensure an appropriate orientation of the solar panels to collect the maximum power from the sun. An industrial partner specialized in the development of computer-aided engineering solutions, SAMTECH, and a research center, Liège Space Center (CSL), also bring their expertise to the project. [less ▲]

Simulation and optimization of controlled multibody systems: Application to vehicle dynamics

Conference (2006, November)

The generalized-alpha method in mechatronic applications

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 ▲]

An extended flexible multibody dynamics software for mechatronic applications

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 ▲]

Flexible mechatronic systems: Time integration and sensitivity analysis

Scientific conference (2006, July)

The generalized-alpha time-integration scheme for mechatronic systems with elastic components

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 ▲]

A model reduction method for the control of rigid mechanisms

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 ▲]

Reduced-order modeling of flexible mechanisms

Conference (2005, September)