1,774 research outputs found
On the optimal design of parallel robots taking into account their deformations and natural frequencies
This paper discusses the utility of using simple stiffness and vibrations
models, based on the Jacobian matrix of a manipulator and only the rigidity of
the actuators, whenever its geometry is optimised. In many works, these
simplified models are used to propose optimal design of robots. However, the
elasticity of the drive system is often negligible in comparison with the
elasticity of the elements, especially in applications where high dynamic
performances are needed. Therefore, the use of such a simplified model may lead
to the creation of robots with long legs, which will be submitted to large
bending and twisting deformations. This paper presents an example of
manipulator for which it is preferable to use a complete stiffness or vibration
model to obtain the most suitable design and shows that the use of simplified
models can lead to mechanisms with poorer rigidity
Parallel Manipulators
In recent years, parallel kinematics mechanisms have attracted a lot of attention from the academic and industrial communities due to potential applications not only as robot manipulators but also as machine tools. Generally, the criteria used to compare the performance of traditional serial robots and parallel robots are the workspace, the ratio between the payload and the robot mass, accuracy, and dynamic behaviour. In addition to the reduced coupling effect between joints, parallel robots bring the benefits of much higher payload-robot mass ratios, superior accuracy and greater stiffness; qualities which lead to better dynamic performance. The main drawback with parallel robots is the relatively small workspace. A great deal of research on parallel robots has been carried out worldwide, and a large number of parallel mechanism systems have been built for various applications, such as remote handling, machine tools, medical robots, simulators, micro-robots, and humanoid robots. This book opens a window to exceptional research and development work on parallel mechanisms contributed by authors from around the world. Through this window the reader can get a good view of current parallel robot research and applications
An Overview of Kinematic and Calibration Models Using Internal/External Sensors or Constraints to Improve the Behavior of Spatial Parallel Mechanisms
This paper presents an overview of the literature on kinematic and calibration models of parallel mechanisms, the influence of sensors in the mechanism accuracy and parallel mechanisms used as sensors. The most relevant classifications to obtain and solve kinematic models and to identify geometric and non-geometric parameters in the calibration of parallel robots are discussed, examining the advantages and disadvantages of each method, presenting new trends and identifying unsolved problems. This overview tries to answer and show the solutions developed by the most up-to-date research to some of the most frequent questions that appear in the modelling of a parallel mechanism, such as how to measure, the number of sensors and necessary configurations, the type and influence of errors or the number of necessary parameters
The Octahedral Hexarot - a novel 6-DOF parallel manipulator
A novel 6-DOF parallel kinematic manipulator named the Octahedral Hexarot is presented and analyzed. It is shown that this manipulator has the important benefits of combining a large positional workspace in relation to its footprint with a sizable range of platform rotations. These features are obtained by combining a rotation-symmetric actuating arm system with links in an octahedral-like configuration. Thus the manipulator consists of a central cylindrical column with six actuated rotating upper arms that can rotate indefinitely around the central column. Each upper arm is connected to a manipulated platform by one 5-DOF lower arm link. The link arrangement of the Octahedral Hexarot is inspired by the original Gough platform. The manipulated platform is an equilateral triangle and the joint positions on the upper arms approximately form an equilateral triangle. A task dependent optimization procedure for the structural parameters is proposed and the workspace of the resulting manipulator is analyzed in depth.<br /
Kinematics, workspace and singularity analysis of a multi-mode parallel robot
A family of reconfigurable parallel robots can change motion modes by passing
through constraint singularities by locking and releasing some passive joints
of the robot. This paper is about the kinematics, the workspace and singularity
analysis of a 3-PRPiR parallel robot involving lockable Pi and R (revolute)
joints. Here a Pi joint may act as a 1-DOF planar parallelogram if its
lock-able P (prismatic) joint is locked or a 2-DOF RR serial chain if its
lockable P joint is released. The operation modes of the robot include a 3T
operation modes to three 2T1R operation modes with two different directions of
the rotation axis of the moving platform. The inverse kinematics and forward
kinematics of the robot in each operation modes are dealt with in detail. The
workspace analysis of the robot allow us to know the regions of the workspace
that the robot can reach in each operation mode. A prototype built at
Heriot-Watt University is used to illustrate the results of this work.Comment: International Design Engineering Technical Conferences \& Computers
and Information in Engineering Conference, Aug 2017, Cleveland, United
States. 201
Kinematics and Workspace Analysis of a Three-Axis Parallel Manipulator: the Orthoglide
The paper addresses kinematic and geometrical aspects of the Orthoglide, a
three-DOF parallel mechanism. This machine consists of three fixed linear
joints, which are mounted orthogonally, three identical legs and a mobile
platform, which moves in the Cartesian x-y-z space with fixed orientation. New
solutions to solve inverse/direct kinematics are proposed and we perform a
detailed workspace and singularity analysis, taking into account specific joint
limit constraints
Technology-Oriented Optimization of the Secondary Design Parameters of Robots for High-Speed Machining Applications
International audienceIn this paper, a new methodology for the optimal design of the secondary geometric parameters (shape of links, size of the platform, etc.) of parallel kinematic machine tools is proposed. This approach aims at minimizing the total mass of the robot under position accuracy constraints. This methodology is applied to two translational parallel robots with three degrees-of-freedom (DOF): the Y-STAR and the UraneSX. The proposed approach is able to speed up the design process and to help the designer to find more quickly a set of design parameters
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