9 research outputs found
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
Kinematic and Dynamic Analysis of the 2-DOF Spherical Wrist of Orthoglide 5-axis
This paper deals with the kinematics and dynamics of a two degree of freedom
spherical manipulator, the wrist of Orthoglide 5-axis. The latter is a parallel
kinematics machine composed of two manipulators: i) the Orthoglide 3-axis; a
three-dof translational parallel manipulator that belongs to the family of
Delta robots, and ii) the Agile eye; a two-dof parallel spherical wrist. The
geometric and inertial parameters used in the model are determined by means of
a CAD software. The performance of the spherical wrist is emphasized by means
of several test trajectories. The effects of machining and/or cutting forces
and the length of the cutting tool on the dynamic performance of the wrist are
also analyzed. Finally, a preliminary selection of the motors is proposed from
the velocities and torques required by the actuators to carry out the test
trajectories
Kinematic and Dynamic Analyses of the Orthoglide 5-axis
International audienceThis paper deals with the kinematic and dynamic analyses of the Orthoglide 5-axis, a five-degree-of-freedom manipulator. It is derived from two manipulators: i) the Orthoglide 3-axis; a three dof translational manipulator and ii) the Agile eye; a parallel spherical wrist. First, the kinematic and dynamic models of the Orthoglide 5-axis are developed. The geometric and inertial parameters of the manipulator are determined by means of a CAD software. Then, the required motors performances are evaluated for some test trajectories. Finally, the motors are selected in the catalogue from the previous results
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
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
Enhanced stiffness modeling of manipulators with passive joints
The paper presents a methodology to enhance the stiffness analysis of serial
and parallel manipulators with passive joints. It directly takes into account
the loading influence on the manipulator configuration and, consequently, on
its Jacobians and Hessians. The main contributions of this paper are the
introduction of a non-linear stiffness model for the manipulators with passive
joints, a relevant numerical technique for its linearization and computing of
the Cartesian stiffness matrix which allows rank-deficiency. Within the
developed technique, the manipulator elements are presented as pseudo-rigid
bodies separated by multidimensional virtual springs and perfect passive
joints. Simulation examples are presented that deal with parallel manipulators
of the Ortholide family and demonstrate the ability of the developed
methodology to describe non-linear behavior of the manipulator structure such
as a sudden change of the elastic instability properties (buckling)
Stiffness modeling for perfect and non-perfect parallel manipulators under internal and external loadings
International audienceThe paper presents an advanced stiffness modeling technique for perfect and non-perfect parallel manipulators under internal and external loadings. Particular attention is paid to the manipulators composed of non-perfect serial chains, whose geometrical parameters differ from the nominal ones and do not allow to assemble manipulator without internal stresses that considerably affect the stiffness properties and also change the end-effector location. In contrast to other works, several types of loadings are considered simultaneously: an external force applied to the end-effector, internal loadings generated by the assembling of non-perfect serial chains and external loadings applied to the intermediate points (auxiliary loading due to the gravity forces and relevant compensator mechanisms, etc.). For this type of manipulators, a non-linear stiffness modeling technique is proposed that allows 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 the compliance errors caused by the considered factors are illustrated by an example that deals with parallel manipulators of the Orthoglide family