621 research outputs found
Multi-Objective Design Optimization of the Leg Mechanism for a Piping Inspection Robot
This paper addresses the dimensional synthesis of an adaptive mechanism of
contact points ie a leg mechanism of a piping inspection robot operating in an
irradiated area as a nuclear power plant. This studied mechanism is the leading
part of the robot sub-system responsible of the locomotion. Firstly, three
architectures are chosen from the literature and their properties are
described. Then, a method using a multi-objective optimization is proposed to
determine the best architecture and the optimal geometric parameters of a leg
taking into account environmental and design constraints. In this context, the
objective functions are the minimization of the mechanism size and the
maximization of the transmission force factor. Representations of the Pareto
front versus the objective functions and the design parameters are given.
Finally, the CAD model of several solutions located on the Pareto front are
presented and discussed.Comment: Proceedings of the ASME 2014 International Design Engineering
Technical Conferences \& Computers and Information in Engineering Conference,
Buffalo : United States (2014
POINCARE-CHETAYEV EQUATIONS AND FLEXIBLE MULTI-BODY SYSTEMS
International audienceThis article is devoted to the dynamics of flexible multi-body systems and to their links with a fundamental set of equations discovered by H. Poincaré one hundred years ago [1]. These equations, called "Poincaré-Chetayev equations", are today known to be the foundation of the Lagrangian reduction theory. Starting with the extension of these equations to a Cosserat medium, we show that the two basic sets of equations used in flexible multi-body dynamics. The generalized Newton-Euler model of flexible multi-body systems in the floating frame approach and the partial differential equations of the nonlinear geometrically exact theory in the Galilean approach, are Poincaré-Chetayev equations
Poincaré’s Equations for Cosserat Media: Application to Shells
International audienceIn 1901 Henri Poincaré discovered a new set of equations for mechanics. These equations are a generalization of Lagrange's equations for a system whose configuration space is a Lie group which is not necessarily commutative. Since then, this result has been extensively refined through the Lagrangian reduction theory. In the present contribution, we extend these equations from classical mechanical systems to continuous Cosserat media, i.e. media in which the usual point particles are replaced by small rigid bodies, called micro-structures. In particular, we will see how the Shell balance equations used in nonlinear structural dynamics, can be easily derived from this extension of the Poincaré's result
Liquid spreading in trickle-bed reactors: Experiments and numerical simulations using Eulerian--Eulerian two-fluid approach
Liquid spreading in gas-liquid concurrent trickle-bed reactors is simulated
using an Eulerian twofluid CFD approach. In order to propose a model that
describes exhaustively all interaction forces acting on each fluid phase with
an emphasis on dispersion mechanisms, a discussion of closure laws available in
the literature is proposed. Liquid dispersion is recognized to result from two
main mechanisms: capillary and mechanical (Attou and Ferschneider, 2000;
Lappalainen et al., 2009- The proposed model is then implemented in two
trickle-bed configurations matching with two experimental set ups: In the first
configuration, simulations on a 2D axisymmetric geometry are considered and the
model is validated upon a new set of experimental data. Overall pressure drop
and liquid distribution obtained from -ray tomography are provided for
different geometrical and operating conditions. In the second configuration, a
3D simulation is considered and the model is compared to experimental liquid
flux patterns at the bed outlet. A sensitivity analysis of liquid spreading to
bed geometrical characteristics (void-fraction and particles diameter) as well
as to gas and liquid flow rates is proposed. The model is shown to achieve very
good agreement with experimental data and to predict, accurately, tendencies of
liquid spreading for various geometrical bed characteristics and/or phases
flow-rates
A Hybrid Dynamic Model Of An Insect-Like MAV With Soft Wings
International audienceThis paper presents a hybrid dynamic model of a 3-D aerial insect-like robot. The soft-bodied insect wings modeling is based on a continuous version of the Newton-Euler dynamics where the leading edge is treated as a continuous Cosserat beam. These wings are connected to an insect's rigid thorax using a discrete recursive algorithm based on the Newton-Euler equations. Here we detail the inverse dynamic model algorithm. This version of the dynamic model solves the following two problems involved in any locomotion task: 1â—¦) it enables the net motion of a reference body to be computed from the known data of internal motions (strain fields); 2â—¦) it gives the internal torques required to impose these internal (strain fields) motions. The essential fluid effects have been taken into account using a simplified analytical hovering flight aerodynamic model. To facilitate the analysis of numerical results, a visualization tool is developed
Macro-continuous dynamics for hyper-redundant robots: application to locomotion bio-inspired by elongated animals
International audienceThis article presents a unified dynamic modeling approach of continuum robots. The robot is modeled as a geometrically exact beam continuously actuated through an active strain law. Once included into the geometric mechanics of locomotion, the approach applies to any hyper-redundant or continuous robot devoted to manipulation and/or locomotion. Furthermore, exploiting the nature of the resulting models as being a continuous version of the Newton-Euler models of discrete robots, an algorithm is proposed which is capable of computing the internal control torques (and/or forces) as well as the rigid overall motions of the locomotor robot. The efficiency of the approach is finally illustrated through many examples directly related to the terrestrial locomotion of elongated animals as snakes, worms or caterpillars and their associated bio-mimetic artifacts
- …