65 research outputs found
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
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
Compliance error compensation technique for parallel robots composed of non-perfect serial chains
The paper presents the compliance errors compensation technique for
over-constrained parallel manipulators under external and internal loadings.
This technique is based on the non-linear stiffness modeling which is able to
take into account the influence of non-perfect geometry of serial chains caused
by manufacturing errors. Within the developed technique, the deviation
compensation reduces to an adjustment of a target trajectory that is modified
in the off-line mode. The advantages and practical significance of the proposed
technique are illustrated by an example that deals with groove milling by the
Orthoglide manipulator that considers different locations of the workpiece. It
is also demonstrated that the impact of the compliance errors and the errors
caused by inaccuracy in serial chains cannot be taken into account using the
superposition principle.Comment: arXiv admin note: text overlap with arXiv:1204.175
Stiffness modeling of non-perfect parallel manipulators
The paper focuses on the stiffness modeling of parallel manipulators composed
of non-perfect serial chains, whose geometrical parameters differ from the
nominal ones. In these manipulators, there usually exist essential internal
forces/torques that considerably affect the stiffness properties and also
change the end-effector location. These internal load-ings are caused by
elastic deformations of the manipulator ele-ments during assembling, while the
geometrical errors in the chains are compensated for by applying appropriate
forces. For this type of manipulators, a non-linear stiffness modeling
tech-nique is proposed that allows us to take into account inaccuracy in the
chains and to aggregate their stiffness models for the case of both small and
large deflections. Advantages of the developed technique and its ability to
compute and compensate for the compliance errors caused by different factors
are illustrated by an example that deals with parallel manipulators of the
Or-thoglide famil
Compensation of compliance errors in parallel manipulators composed of non-perfect kinematic chains
The paper is devoted to the compliance errors compensation for parallel
manipulators under external loading. Proposed approach is based on the
non-linear stiffness modeling and reduces to a proper adjusting of a target
trajectory. In contrast to previous works, in addition to compliance errors
caused by machining forces, the problem of assembling errors caused by
inaccuracy in the kinematic chains is considered. The advantages and practical
significance of the proposed approach are illustrated by examples that deal
with groove milling with Orthoglide manipulator.Comment: Advances in Robot Kinematics, France (2012
Outils pour l’identification des paramètres de raideur des robots à l’aide d’un logiciel de CAO
This report proposes a CAD-based approach for identification of the elasto-static parameters of the robotic manipulators. The main contributions are in the areas of virtual experiment planning and algorithmic data processing, which allows to obtain the stiffness matrix with required accuracy. In contrast to previous works, the developed technique operates with the deflection field produced by virtual experiments in a CAD environment. The proposed approach provides high identification accuracy (about 0.1% for the stiffness matrix element) and is able to take into account the real shape of the link, coupling between rotational/translational deflections and joint particularities. To compute the stiffness matrix, the numerical technique has been developed, and some recommendations for optimal settings of the virtual experiments are given. In order to minimize the identification errors, the statistical data processing technique was applied. The advantages of the developed approach have been confirmed by case studies dealing with the links of parallel manipulator of the Orthoglide family, for which the identification errors have been reduced to 0.1%ANR COROUSS
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
CAD-based approach for identification of elasto-static parameters of robotic manipulators
The paper presents an approach for the identification of elasto-static
parameters of a robotic manipulator using the virtual experiments in a CAD
environment. It is based on the numerical processing of the data extracted from
the finite element analysis results, which are obtained for isolated
manipulator links. This approach allows to obtain the desired stiffness
matrices taking into account the complex shape of the links, couplings between
rotational/translational deflections and particularities of the joints
connecting adjacent links. These matrices are integral parts of the manipulator
lumped stiffness model that are widely used in robotics due to its high
computational efficiency. To improve the identification accuracy,
recommendations for optimal settings of the virtual experiments are given, as
well as relevant statistical processing techniques are proposed. Efficiency of
the developed approach is confirmed by a simulation study that shows that the
accuracy in evaluating the stiffness matrix elements is about 0.1%.Comment: arXiv admin note: substantial text overlap with arXiv:0909.146
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