2,145 research outputs found
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
Identification of geometrical and elastostatic parameters of heavy industrial robots
The paper focuses on the stiffness modeling of heavy industrial robots with
gravity compensators. The main attention is paid to the identification of
geometrical and elastostatic parameters and calibration accuracy. To reduce
impact of the measurement errors, the set of manipulator configurations for
calibration experiments is optimized with respect to the proposed performance
measure related to the end-effector position accuracy. Experimental results are
presented that illustrate the advantages of the developed technique.Comment: arXiv admin note: substantial text overlap with arXiv:1311.667
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
Modelling of the gravity compensators in robotic manufacturing cells
The paper deals with the modeling and identification of the gravity
compensators used in heavy industrial robots. The main attention is paid to the
geometrical parameters identification and calibration accuracy. To reduce
impact of the measurement errors, the design of calibration experiments is
used. The advantages of the developed technique are illustrated by experimental
result
Compliance error compensation in robotic-based milling
The paper deals with the problem of compliance errors compensation in
robotic-based milling. Contrary to previous works that assume that the
forces/torques generated by the manufacturing process are constant, the
interaction between the milling tool and the workpiece is modeled in details.
It takes into account the tool geometry, the number of teeth, the feed rate,
the spindle rotation speed and the properties of the material to be processed.
Due to high level of the disturbing forces/torques, the developed compensation
technique is based on the non-linear stiffness model that allows us to modify
the target trajectory taking into account nonlinearities and to avoid the
chattering effect. Illustrative example is presented that deals with
robotic-based milling of aluminum alloy
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
Modèle des interactions dynamiques
In robotic-based machining, an interaction between the workpiece and technological tool causes essential deflections that significantly decrease the manufacturing accuracy. Relevant compliance errors highly depend on the manipulator configuration and essentially differ throughout the workspace. Their influence is especially important for heavy serial robots. To overcome this difficulty this report presents a new technique for compensation of the compliance errors caused by technological process. In contrast to previous works, this technique is based on the non-linear stiffness model and the reduced elasto-dynamic model of the robotic based milling process. The advantages and practical significance of the proposed approach are illustrated by milling with of KUKA KR270. It is shown that after error compensation technique significantly increase the accuracy of milling.ANR COROUSS
Stiffness modeling of robotic manipulator with gravity compensator
The paper focuses on the stiffness modeling of robotic manipulators with
gravity compensators. The main attention is paid to the development of the
stiffness model of a spring-based compensator located between sequential links
of a serial structure. The derived model allows us to describe the compensator
as an equivalent non-linear virtual spring integrated in the corresponding
actuated joint. The obtained results have been efficiently applied to the
stiffness modeling of a heavy industrial robot of the Kuka family
Modèles élastiques et élasto‐dynamiques de robots porteurs
The report presents an advanced stiffness modeling technique for parallel manipulators composed of perfect and non-perfect serial chains. The developed technique contributes both to the stiffness modeling of serial and parallel manipulators under internal and external loadings. Particular attention has been done to enhancement of VJM-based stiffness modeling technique for the case of auxiliary loading (applied to the intermediate points). The obtained results allows us to take into account gravity forces induced by the link weights which are assumed to be applied in the intermediate points. In contrast to other works, the developed technique is able to take into account deviation of the end-platform location because of inaccuracy in the geometry of serial chains, which does not allow to assemble manipulator without internal stresses. The developed aggregation procedure combines the chain stiffness models and produces the relevant force-deflection relation, the aggregated Cartesian stiffness matrix and the reference point displacements caused by inaccuracy in kinematic chains. The developed technique can be applied to both over-constrained and under-constrained manipulators, and is suitable for the cases of both small and large deflections.ANR COROUSS
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