383 research outputs found
Kinematic Analysis of a New Parallel Machine Tool: the Orthoglide
This paper describes a new parallel kinematic architecture for machining
applications: the orthoglide. This machine features three fixed parallel linear
joints which are mounted orthogonally and a mobile platform which moves in the
Cartesian x-y-z space with fixed orientation. The main interest of the
orthoglide is that it takes benefit from the advantages of the popular PPP
serial machines (regular Cartesian workspace shape and uniform performances) as
well as from the parallel kinematic arrangement of the links (less inertia and
better dynamic performances), which makes the orthoglide well suited to
high-speed machining applications. Possible extension of the orthoglide to
5-axis machining is also investigated
Design of a Three-Axis Isotropic Parallel Manipulator for Machining Applications: The Orthoglide
The orthoglide is a 3-DOF parallel mechanism designed at IRCCyN for machining
applications. It features three fixed parallel linear joints which are mounted
orthogonally and a mobile platform which moves in the Cartesian x-y-z space
with fixed orientation. The orthoglide has been designed as function of a
prescribed Cartesian workspace with prescribed kinetostatic performances. The
interesting features of the orthoglide are a regular Cartesian workspace shape,
uniform performances in all directions and good compactness. A small-scale
prototype of the orthoglide under development is presented at the end of this
paper
Strategies for the Design of a Slide-o-Cam Transmission
The optimization of the pressure angle in a cam-follower transmission is
reported in this paper. This transmission is based on Slide-o-Cam, a cam
mechanism with multiple rollers mounted on a common translating follower. The
design of Slide-o-Cam, a transmission intended to produce a sliding motion from
a turning drive, or vice versa, was reported elsewhere. This transmission
provides pure-rolling motion, thereby reducing the friction of rack-and-pinions
and linear drives. The pressure angle is a suitable performance index for this
transmission because it determines the amount of force transmitted to the load
vs. that transmitted to the machine frame. Two alternative design strategies
are studied, namely, (i) increase the number of lobes on each cam or (ii)
increase the number of cams. This device is intended to replace the current
ball-screws in Orthoglide, a three-DOF parallel robot for the production of
translational motions, currently under development at Ecole Centrale de Nantes
for machining applications
Working Modes and Aspects in Fully-Parallel Manipulator
The aim of this paper is to characterize the notion of aspect in the
workspace and in the joint space for parallel manipulators. In opposite to the
serial manipulators, the parallel manipulators can admit not only multiple
inverse kinematic solutions, but also multiple direct kinematic solutions. The
notion of aspect introduced for serial manipulators in [Borrel 86], and
redefined for parallel manipulators with only one inverse kinematic solution in
[Wenger 1997], is redefined for general fully parallel manipulators. Two
Jacobian matrices appear in the kinematic relations between the joint-rate and
the Cartesian-velocity vectors, which are called the "inverse kinematics" and
the "direct kinematics" matrices. The study of these matrices allow to
respectively define the parallel and the serial singularities. The notion of
working modes is introduced to separate inverse kinematic solutions. Thus, we
can find out domains of the workspace and the joint space exempt of
singularity. Application of this study is the moveability analysis in the
workspace of the manipulator as well as path-planing and control. This study is
illustrated in this paper with a RR-RRR planar parallel manipulator
The Computation of All 4R Serial Spherical Wrists With an Isotropic Architecture
A spherical wrist of the serial type with n revolute (R) joints is said to be
isotropic if it can attain a posture whereby the singular values of its
Jacobian matrix are all equal to sqrt(n/3). What isotropy brings about is
robustness to manufacturing, assembly, and measurement errors, thereby
guaranteeing a maximum orientation accuracy. In this paper we investigate the
existence of redundant isotropic architectures, which should add to the
dexterity of the wrist under design by virtue of its extra degree of freedom.
The problem formulation, for, leads to a system of eight quadratic equations
with eight unknowns. The Bezout number of this system is thus 2^8=256, its BKK
bound being 192. However, the actual number of solutions is shown to be 32. We
list all solutions of the foregoing algebraic problem. All these solutions are
real, but distinct solutions do not necessarily lead to distinct manipulators.
Upon discarding those algebraic solutions that yield no new wrists, we end up
with exactly eight distinct architectures, the eight corresponding manipulators
being displayed at their isotropic postures
Design of a Spherical Wrist with Parallel Architecture: Application to Vertebrae of an Eel Robot
The design of a spherical wrist with parallel architecture is the object of
this article. This study is part of a larger project, which aims to design and
to build an eel robot for inspection of immersed piping. The kinematic analysis
of the mechanism is presented first to characterize the singular configurations
as well as the isotropic configurations. We add the design constraints related
to the application, such as (i) the compactness of the mechanism, (ii) the
symmetry of the elements in order to ensure static and dynamic balance and
(iii) the possibility of the mechanism to fill the elliptic form of the ell
sections
The Kinematic Analysis of a Symmetrical Three-Degree-of-Freedom Planar Parallel Manipulator
Presented in this paper is the kinematic analysis of a symmetrical
three-degree-of-freedom planar parallel manipulator. In opposite to serial
manipulators, parallel manipulators can admit not only multiple inverse
kinematic solutions, but also multiple direct kinematic solutions. This
property produces more complicated kinematic models but allows more flexibility
in trajectory planning. To take into account this property, the notion of
aspects, i.e. the maximal singularity-free domains, was introduced, based on
the notion of working modes, which makes it possible to separate the inverse
kinematic solutions. The aim of this paper is to show that a non-singular
assembly-mode changing trajectory exist for a symmetrical planar parallel
manipulator, with equilateral base and platform triangle
Architecture Optimization of a 3-DOF Translational Parallel Mechanism for Machining Applications, the Orthoglide
This paper addresses the architecture optimization of a 3-DOF translational
parallel mechanism designed for machining applications. The design optimization
is conducted on the basis of a prescribed Cartesian workspace with prescribed
kinetostatic performances. The resulting machine, the Orthoglide, features
three fixed parallel linear joints which are mounted orthogonally and a mobile
platform which moves in the Cartesian x-y-z space with fixed orientation. The
interesting features of the Orthoglide are a regular Cartesian workspace shape,
uniform performances in all directions and good compactness. A small-scale
prototype of the Orthoglide under development is presented at the end of this
paper
Moveability and Collision Analysis for Fully-Parallel Manipulators
The aim of this paper is to characterize the moveability of fully-parallel
manipulators in the presence of obstacles. Fully parallel manipulators are used
in applications where accuracy, stiffness or high speeds and accelerations are
required \cite{Merlet:97}. However, one of its main drawbacks is a relatively
small workspace compared to the one of serial manipulators. This is due mainly
to the existence of potential internal collisions, and the existence of
singularities. In this paper, the notion of free aspect is defined which
permits to exhibit domains of the workspace and the joint space free of
singularity and collision. The main application of this study is the
moveability analysis in the workspace of the manipulator as well as
path-planning, control and design
A New Three-DOF Parallel Mechanism: Milling Machine Applications
This paper describes a new parallel kinematic architecture for machining
applications, namely, the orthoglide. This machine features three fixed
parallel linear joints which are mounted orthogonally and a mobile platform
which moves in the Cartesian x-y-z space with fixed orientation. The main
interest of the orthoglide is that it takes benefit from the advantages of the
popular PPP serial machines (regular Cartesian workspace shape and uniform
performances) as well as from the parallel kinematic arrangement of the links
(less inertia and better dynamic performances), which makes the orthoglide well
suited to high-speed machining applications. Possible extension of the
orthoglide to 5-axis machining is also investigated
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