1,185 research outputs found
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
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
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
Stiffness modelling of parallelogram-based parallel manipulators
International audienceThe paper presents a methodology to enhance the stiffness analysis of parallel manipulators with parallelogram-based linkage. It directly takes into account the influence of the external loading and allows computing both the non-linear ``load-deflection" relation and relevant rank-deficient stiffness matrix. An equivalent bar-type pseudo-rigid model is also proposed to describe the parallelogram stiffness by means of five mutually coupled virtual springs. The contributions of this paper are highlighted with a parallelogram-type linkage used in a manipulator from the Orthoglide family
Nonlinear Effects in Stiffness Modeling of Robotic Manipulators
The paper focuses on the enhanced stiffness modeling of robotic manipulators
by taking into account influence of the external force/torque acting upon the
end point. It implements the virtual joint technique that describes the
compliance of manipulator elements by a set of localized six-dimensional
springs separated by rigid links and perfect joints. In contrast to the
conventional formulation, which is valid for the unloaded mode and small
displacements, the proposed approach implicitly assumes that the loading leads
to the non-negligible changes of the manipulator posture and corresponding
amendment of the Jacobian. The developed numerical technique allows computing
the static equilibrium and relevant force/torque reaction of the manipulator
for any given displacement of the end-effector. This enables designer detecting
essentially nonlinear effects in elastic behavior of manipulator, similar to
the buckling of beam elements. It is also proposed the linearization procedure
that is based on the inversion of the dedicated matrix composed of the
stiffness parameters of the virtual springs and the Jacobians/Hessians of the
active and passive joints. The developed technique is illustrated by an
application example that deals with the stiffness analysis of a parallel
manipulator of the Orthoglide family.Comment: ISSN 2070-372
Stiffness Analysis of Parallel Manipulators with Preloaded Passive Joints
The paper presents a methodology for the enhanced stiffness analysis of
parallel manipulators with internal preloading in passive joints. It also takes
into account influence of the external loading and allows computing both the
non-linear "load-deflection" relation and the stiffness matrices for any given
location of the end-platform or actuating drives. Using this methodology, it is
proposed the kinetostatic control algorithm that allows to improve accuracy of
the classical kinematic control and to compensate position errors caused by
elastic deformations in links/joints due to the external/internal loading. The
results are illustrated by an example that deals with a parallel manipulator of
the Orthoglide family where the internal preloading allows to eliminate the
undesired buckling phenomena and to improve the stiffness in the neighborhood
of its kinematic singularities
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