Juan C. Garcia Orden

• PhD
• Associate Professor at Universidad Politécnica de Madrid

In recent years, back-support exoskeletons have been postulated as a competitive solution to reduce mechanical loading during lifting tasks, contributing to the prevention of low back pain. However, little research involving lower body exoskeletons has been done on this matter. The present study evaluates the impact of the H2 robotic exoskeleton on...

Many engineering fields such as aerospace, robotics, and computer graphics, have applications that contain elements amenable to be modeled as slender beams with negligible shear and torsion effects. The literature contains several energy-momentum (EM) formulations for beams based on a nonlinear finite element approach but, to the best of the author...

Practical multibody models are typically composed by a set of bodies (rigid or deformable) linked by joints, represented by constraint equations, and in many cases are subject to potential forces. Thus, a proper formulation of these constraints and forces is an essential aspect in the numerical analysis of their dynamics. On the other hand, geometr...

We present a conservative formulation for the frictional contact forces developed in the framework of an energy-consistent method. Bilateral constrains, that is, joints and rigid links, are imposed using the augmented Lagrange technique, provided that the constraints are exactly satisfied. We propose a formulation based on a penalty method to deal...

This paper describes a very simple beam model, amenable to be used in multibody applications, for cases where the effects of torsion and shear are negligible. This is the case of slender rods connecting different parts of many space mechanisms, models useful in polymer physics, computer animation, etc. The proposed new model follows a lumped parame...

We present the theory of novel time-stepping algorithms for general non-linear, non-smooth, coupled, thermomechanical problems. The proposed methods are thermodynamically consistent in the sense that their solutions rigorously comply with the two laws of thermodynamics: for isolated systems they preserve the total energy and the entropy never decre...

Structure-preserving integrators are in the focus of ongoing research because of their distinguished features of robustness and long time stability. In particular, their formulation for coupled problems that include dissipative mechanisms is still an active topic. Conservative formulations, such as the thermo-elastic case without heat conduction, f...

Structure-preserving integrators are in the focus of ongoing research because of their distinguished features of robustness and long time stability. In particular, their formulation for coupled problems that include dissipative mechanisms is still an active topic. Conservative formulations, such as the thermo-elastic case without heat conduction, f...

This work is concerned with the numerical solution of the equations of the dynamics of flexible multibody systems with dissipative physical mechanisms. Specifically, we consider systems composed of rigid and deformable bodies made of a viscoelastic continuum, that may experience large displacements and strains, connected by joints. Within this fram...

This work is concerned with the numerical solution of the evolution equations of thermo-mechanical systems, in such a way that the scheme itself satisfies the laws of thermodynamics. Within this framework, we present a novel integration scheme for the dynamics of viscoelastic continuum bodies in isothermal conditions. The proposed scheme intrinsica...

This work is concerned with the numerical solution of the evolution equations of thermo-mechanical systems, in such a way that the scheme itself satisfies the laws of thermody-namics. Preserving structure integrators are widely developed for conservative (Hamilto-nian) systems, being the most representative method the well-known energy-momentum due...

EDFA, as part of the Power Plant Physics and Technology programme, has been working on the pre-conceptual design of a Demonstration Power Plant (DEMO). As part of this programme, several options for the remote maintenance (RM) of the in-vessel components were assessed during the 2012 activities [1]. In 2013, these remote maintenance activi- ties we...

This work analyses a conserving time integration scheme applied to impact dynam- ics of one or more points against a rigid surface. This rigid surface may represents the boundary of a rigid body or it could represent a rigid cavity inside a body, and it should be represented by an implicit function. The points may be material particles, vertex of a...

This paper is concerned with the numerical solution of the evolution equations of thermomechanical systems, in such a way that the scheme itself satisfies the laws of thermodynamics. Within this framework, we present a novel integration scheme for the dynamics of viscoelastic continuum bodies in isothermal conditions. This method intrinsically sati...

Beam facing elements of the International Fusion Materials Irradiation Facility (IFMIF) Linear Particle Accelerator prototype (LIPAc) must stop 5-40 MeV D+ ions with a peak current of 125 mA. The duty cycle of the beam loading varies from 0.1% to 100% (CW), depending on the device, with the ions being stopped in the first hundreds microns of the be...

A novel time integration scheme is presented for the numerical solution of the dynamics of discrete systems consisting of point masses and thermo-visco-elastic springs. Even considering fully coupled constitutive laws for the elements, the obtained solutions strictly preserve the two laws of thermodynamics and the symmetries of the continuum evolut...

The direct numerical solution of the index-3 algebraic-differential equation system (DAE) asso-ciated with the constrained dynamics of a multibody system poses several computational difficulties mainly related to stability. Specially in long simulations, the instability is related to the drift of the solution from the velocity constraint manifold....

Meshfree Galerkin methods have been developed recently for the simulation of complex mechanical problems involving large strains of structures, crack propagation, or high velocity impact dynamics. At the present time, the application of these methods to multibody dynamics has not been made despite their great advantage in some situations over stand...

There are many difficulties involved in the numerical integration of index-3 Differential Algebraic Equations (DAEs), mainly related to stability, in the context of mechanical systems. An integrator that exactly enforces the constraint at position level may produce a discrete solution that departs from the velocity and/or acceleration constraint ma...

In this paper we present a novel integration strategy to solve the evolution equations of deformable, nonlinear elements that possess viscoelastic mechanical response coupled with thermal dissipation. These types of elements may be found in a large number of every-day mechanical systems, such as vehicle suspensions, vibration absorbers for structur...

There are many difficulties involved in the numerical integration of index-3 Differential Algebraic Equations (DAEs), mainly related to stability, in the context of mechanical systems. An integrator that exactly enforces the constraint at position level may produce a discrete solution that departs from the velocity and/or acceleration constraint ma...

In the last decade, there has been a growing interest of meshfree methods [1] as an alternative to the widely used finite element methods. Their approach of mesh independent discretization by means of locally supported shape functions make this kind of methods well suited for very different types of problems, such as large strains, complex geometry...

Several considerations are important if we try to carry out fast and precise simulations in multibody dynamics: the choice of modeling coordinates, the choice of dynamical formulations and the numerical integration scheme along with the numerical implementation. All these matters are very important in order to decide whether a specific method is go...

This work presents the application to the dynamics of multi- body systems of two methods based on augmented Lagrangian techniques, compares them, and gives some criteria for its use in realistic problems. The methods are an augmented Lagrangian method with or- thogonalprojections of velocities and accelerations, and an aug- mented Lagrangian energy...

The motion of many practical mechanical systems is often constrained. An important example is the dynamics of multibody systems, where the numerical solution of this type of systems faces several difficulties. A strategy for to solve this type of problems is the augmented Lagrange formulation, which allows the use of numerical integrators for ODEs,...

Flexible multibody systems (MBS) appear in a number of mechanical applications, in which the model must consider the deformation of some or all of the bodies. A classical method for considering flexibility has been the floating frame technique (25), generally limited to small strains. A more general approach based on inertial coordinates may be for...

A methodology for the study of typical smooth joint clearances in multibody systems is presented. The proposed approach takes advantage of the analytical definition of the material surfaces defining the clearance, resulting in a formulation where the gap does not play a central role, as it happens in standard contact models. The contact forces are...

Real joints in multibody systems incorporate complex effects, such as clearances and friction, that may significantly affect the overall performance and serviceable life of the mechanism. The basic phenomenon is the intermittent contact between the surfaces defining the joint, involving a very high number of impact events during the typical time sc...

Mechanical simulation of tissue in the walls of coronary arteries may provide valuable quantitative information for medical practice, such as understanding the evolution of stenosis, angioplasty processes, and placement of stents and possible restenosis. The material constitutive models which represent the mechanical response to strain are highly n...

The treatment of constraints is considered here within the framework ofenergy-momentum conserving formulations for flexible multibody systems.Constraint equations of various types are an inherent component of multibodysystems, their treatment being one of the key performance features ofmathematical formulations and numerical solution schemes. Here...

A unified approach for the treatment of the non-linear dynamics of multibody systems (MBS) composed of both rigid and elastic bodies is proposed. Large displacements and rotations, large strains and non-linear elastic material response are considered for the elastic bodies. The proposed formulation exploits three key ingredients: the use of a depen...

A multibody formulation for the nonlinear dynamics of mechanical systems composed of both rigid and deformable bodies is proposed in this work, focusing on its conservation properties for basic magnitudes such as total energy and momentum.The approach is based on the use of dependent variables (cartesian coordinates of selected points) and the enfo...

The context of this work is the non-linear dynamics ofmultibody systems (MBS). The approach followed for parametrisation ofrigid bodies is the use of inertial coordinates, forming a dependent setof parameters. This approach mixes naturally with nodal coordinates in adisplacement-based finite element discretisation of flexible bodies,allowing an eff...

Esta tesis se centra en el estudio de la dinámica no lineal de sistemas multicuerpo. Se entiende como tales los compuestos por sólidos rígidos y deformables conectados mediante distintos tipos de uniones y con elementos discretos activos como muelles y amortiguadores. Se considera que los cuerpos deformables pueden experimentar grandes desplazamien...

The modeling of multibody systems in natural coordinates leads to systems of dif- ferential-algebraic equations (DAE). Penalty and augmented Lagrangian techniques have been widely used in order to solve this kind of systems. In both cases, penalty forces propor- tional to the violation of the constraints are included in the equations of motion. Con...

21 de Abril de 2003 1. Transformada Discreta de Fourier de una señal La Transformada Discreta de Fourier (TDF) permite describir una señal discreta (definida a partir de un número finito de valores en el tiempo, señalados con círculos en la Figura 1) en el dominio de la frecuencia [Newland, 1989], [Newland, 1984]. Dada una señal discreta g(k∆t), su...