496 research outputs found
Regions of Feasible Point-to-Point Trajectories in the Cartesian Workspace of Fully-Parallel Manipulators
The goal of this paper is to define the n-connected regions in the Cartesian
workspace of fully-parallel manipulators, i.e. the maximal regions where it is
possible to execute point-to-point motions. The manipulators considered in this
study may have multiple direct and inverse kinematic solutions. The N-connected
regions are characterized by projection, onto the Cartesian workspace, of the
connected components of the reachable configuration space defined in the
Cartesian product of the Cartesian space by the joint space. Generalized octree
models are used for the construction of all spaces. This study is illustrated
with a simple planar fully-parallel manipulator
On the characterization of the regions of feasible trajectories in the workspace of parallel manipulators
It was shown recently that parallel manipulators with several inverse
kinematic solutions have the ability to avoid parallel singularities [Chablat
1998a] and self-collisions [Chablat 1998b] by choosing appropriate joint
configurations for the legs. In effect, depending on the joint configurations
of the legs, a given configuration of the end-effector may or may not be free
of singularity and collision. Characterization of the
collision/singularity-free workspace is useful but may be insufficient since
two configurations can be accessible without collisions nor singularities but
it may not exist a feasible trajectory between them. The goal of this paper is
to define the maximal regions of the workspace where it is possible to execute
trajectories. Twodifferent families of regions are defined : 1. those regions
where the end-effector can move between any set of points, and 2. the regions
where any continuous path can be tracked. These regions are characterized from
the notion of aspects and free-aspects recently defined for parallel
manipulators [Chablat 1998b]. The construction of these regions is achieved by
enrichment techniques and using an extension of the octree structures to spaces
of dimension greater than three. Illustrative examples show the interest of
this study to the optimization of trajectories and the design of parallel
manipulators
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
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
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
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
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
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
Position Analysis of the RRP-3(SS) Multi-Loop Spatial Structure
The paper presents the position analysis of a spatial structure composed of
two platforms mutually connected by one RRP and three SS serial kinematic
chains, where R, P, and S stand for revolute, prismatic, and spherical
kinematic pair respectively. A set of three compatibility equations is laid
down that, following algebraic elimination, results in a 28th-order univariate
algebraic equation, which in turn provides the addressed problem with 28
solutions in the complex domain. Among the applications of the results
presented in this paper is the solution to the forward kinematics of the
Tricept, a well-known in-parallel-actuated spatial manipulator. Numerical
examples show adoption of the proposed method in dealing with two case studies
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
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