237 research outputs found
Analyse de la rigidité des machines outils 3 axes d'architecture parallèle hyperstatique
National audienceThe paper presents a new stiffness modelling method for overconstrained parallel manipulators, which is applied to 3-d.o.f. translational mechanisms. It is based on a multidimensional lumped-parameter model that replaces the link flexibility by localized 6-d.o.f. virtual springs. In contrast to other works, the method includes a FEA-based link stiffness evaluation and employs a new solution strategy of the kinetostatic equations, which allows computing the stiffness matrix for the overconstrained architectures and for the singular manipulator postures. The advantages of the developed technique are confirmed by application examples, which deal with comparative stiffness analysis of two translational parallel manipulators
Stiffness Analysis of 3-d.o.f. Overconstrained Translational Parallel Manipulators
The paper presents a new stiffness modelling method for overconstrained
parallel manipulators, which is applied to 3-d.o.f. translational mechanisms.
It is based on a multidimensional lumped-parameter model that replaces the link
flexibility by localized 6-d.o.f. virtual springs. In contrast to other works,
the method includes a FEA-based link stiffness evaluation and employs a new
solution strategy of the kinetostatic equations, which allows computing the
stiffness matrix for the overconstrained architectures and for the singular
manipulator postures. The advantages of the developed technique are confirmed
by application examples, which deal with comparative stiffness analysis of two
translational parallel manipulators
Stiffness Analysis of Overconstrained Parallel Manipulators
The paper presents a new stiffness modeling method for overconstrained
parallel manipulators with flexible links and compliant actuating joints. It is
based on a multidimensional lumped-parameter model that replaces the link
flexibility by localized 6-dof virtual springs that describe both
translational/rotational compliance and the coupling between them. In contrast
to other works, the method involves a FEA-based link stiffness evaluation and
employs a new solution strategy of the kinetostatic equations for the unloaded
manipulator configuration, which allows computing the stiffness matrix for the
overconstrained architectures, including singular manipulator postures. The
advantages of the developed technique are confirmed by application examples,
which deal with comparative stiffness analysis of two translational parallel
manipulators of 3-PUU and 3-PRPaR architectures. Accuracy of the proposed
approach was evaluated for a case study, which focuses on stiffness analysis of
Orthoglide parallel manipulator
Stiffness Analysis Of Multi-Chain Parallel Robotic Systems
The paper presents a new stiffness modelling method for multi-chain parallel
robotic manipulators with flexible links and compliant actuating joints. In
contrast to other works, the method involves a FEA-based link stiffness
evaluation and employs a new solution strategy of the kinetostatic equations,
which allows computing the stiffness matrix for singular postures and to take
into account influence of the external forces. The advantages of the developed
technique are confirmed by application examples, which deal with stiffness
analysis of a parallel manipulator of the Orthoglide famil
Accuracy Improvement for Stiffness Modeling of Parallel Manipulators
The paper focuses on the accuracy improvement of stiffness models for
parallel manipulators, which are employed in high-speed precision machining. It
is based on the integrated methodology that combines analytical and numerical
techniques and deals with multidimensional lumped-parameter models of the
links. The latter replace the link flexibility by localized 6-dof virtual
springs describing both translational/rotational compliance and the coupling
between them. There is presented detailed accuracy analysis of the stiffness
identification procedures employed in the commercial CAD systems (including
statistical analysis of round-off errors, evaluating the confidence intervals
for stiffness matrices). The efficiency of the developed technique is confirmed
by application examples, which deal with stiffness analysis of translational
parallel manipulators
Parametric stiffness analysis of the Orthoglide
This paper presents a parametric stiffness analysis of the Orthoglide. A
compliant modeling and a symbolic expression of the stiffness matrix are
conducted. This allows a simple systematic analysis of the influence of the
geometric design parameters and to quickly identify the critical link
parameters. Our symbolic model is used to display the stiffest areas of the
workspace for a specific machining task. Our approach can be applied to any
parallel manipulator for which stiffness is a critical issue
A simple and visually orientated approach for type synthesis of overconstrained 1T2R parallel mechanisms
This paper presents a simple and highly visual approach for the type synthesis of a family of overconstrained parallel mechanisms that have one translational and two rotational movement capabilities. It considers, especially, mechanisms offering the accuracy and dynamic response needed for machining applications. This family features a spatial limb plus a member of a class of planar symmetrical linkages, the latter connected by a revolute joint either to the machine frame at its base link or to the platform at its output link. Criteria for selecting suitable structures from among numerous candidates are proposed by considering the realistic practical requirements for reconfigurability, movement capability, rational component design and so on. It concludes that a few can simultaneously fulfil the proposed criteria, even though a variety of structures have been presented in the literature. Exploitation of the proposed structures and evaluation criteria then leads to a novel five degrees of freedom hybrid module named TriMule. A significant potential advantage of the TriMule over the Tricept arises because all the joints connecting the base link and the machine frame can be integrated into one single, compact part, leading to a lightweight, cost effective and flexible design particularly suitable for configuring various robotized manufacturing cells
On the optimal design of parallel robots taking into account their deformations and natural frequencies
This paper discusses the utility of using simple stiffness and vibrations
models, based on the Jacobian matrix of a manipulator and only the rigidity of
the actuators, whenever its geometry is optimised. In many works, these
simplified models are used to propose optimal design of robots. However, the
elasticity of the drive system is often negligible in comparison with the
elasticity of the elements, especially in applications where high dynamic
performances are needed. Therefore, the use of such a simplified model may lead
to the creation of robots with long legs, which will be submitted to large
bending and twisting deformations. This paper presents an example of
manipulator for which it is preferable to use a complete stiffness or vibration
model to obtain the most suitable design and shows that the use of simplified
models can lead to mechanisms with poorer rigidity
Kinematic and stiffness analysis of the Orthoglide, a PKM with simple, regular workspace and homogeneous performances
International audienceThe Orthoglide is a Delta-type PKM dedicated to 3-axis rapid machining applications that was originally developed at IRCCyN in 2000-2001 to meet the advantages of both serial 3-axis machines (regular workspace and homogeneous performances) and parallel kinematic architectures (good dynamic performances and stiffness). This machine has three fixed parallel linear joints that are mounted orthogonally. The geometric parameters of the Orthoglide were defined as function of the size of a prescribed cubic Cartesian workspace that is free of singularities and internal collision. The interesting features of the Orthoglide are a regular Cartesian workspace shape, uniform performances in all directions and good compactness. In this paper, a new method is proposed to analyze the stiffness of overconstrained Delta-type manipulators, such as the Orthoglide. The Orthoglide is then benchmarked according to geometric, kinematic and stiffness criteria: workspace to footprint ratio, velocity and force transmission factors, sensitivity to geometric errors, torsional stiffness and translational stiffness
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