343 research outputs found
Accuracy Improvement for Stiffness Modeling of Parallel Manipulators
The paper focuses on the accuracy improvement of stiffness models for
parallel manipulators, which are employed in high-speed precision machining. It
is based on the integrated methodology that combines analytical and numerical
techniques and deals with multidimensional lumped-parameter models of the
links. The latter replace the link flexibility by localized 6-dof virtual
springs describing both translational/rotational compliance and the coupling
between them. There is presented detailed accuracy analysis of the stiffness
identification procedures employed in the commercial CAD systems (including
statistical analysis of round-off errors, evaluating the confidence intervals
for stiffness matrices). The efficiency of the developed technique is confirmed
by application examples, which deal with stiffness analysis of translational
parallel manipulators
Dynamics of the Orthoglide parallel robot
Recursive matrix relations for kinematics and dynamics of the Orthoglide
parallel robot having three concurrent prismatic actuators are established in
this paper. These are arranged according to the Cartesian coordinate system
with fixed orientation, which means that the actuating directions are normal to
each other. Three identical legs connecting to the moving platform are located
on three planes being perpendicular to each other too. Knowing the position and
the translation motion of the platform, we develop the inverse kinematics
problem and determine the position, velocity and acceleration of each element
of the robot. Further, the principle of virtual work is used in the inverse
dynamic problem. Some matrix equations offer iterative expressions and graphs
for the input forces and the powers of the three actuators
Stiffness Analysis of Overconstrained Parallel Manipulators
The paper presents a new stiffness modeling method for overconstrained
parallel manipulators with flexible links and compliant actuating joints. It is
based on a multidimensional lumped-parameter model that replaces the link
flexibility by localized 6-dof virtual springs that describe both
translational/rotational compliance and the coupling between them. In contrast
to other works, the method involves a FEA-based link stiffness evaluation and
employs a new solution strategy of the kinetostatic equations for the unloaded
manipulator configuration, which allows computing the stiffness matrix for the
overconstrained architectures, including 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 of 3-PUU and 3-PRPaR architectures. Accuracy of the proposed
approach was evaluated for a case study, which focuses on stiffness analysis of
Orthoglide parallel manipulator
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
Kinematic calibration of Orthoglide-type mechanisms from observation of parallel leg motions
The paper proposes a new calibration method for parallel manipulators that
allows efficient identification of the joint offsets using observations of the
manipulator leg parallelism with respect to the base surface. The method
employs a simple and low-cost measuring system, which evaluates deviation of
the leg location during motions that are assumed to preserve the leg
parallelism for the nominal values of the manipulator parameters. Using the
measured deviations, the developed algorithm estimates the joint offsets that
are treated as the most essential parameters to be identified. The validity of
the proposed calibration method and efficiency of the developed numerical
algorithms are confirmed by experimental results. The sensitivity of the
measurement methods and the calibration accuracy are also studied
IRSBOT-2: A Novel Two-Dof Parallel Robot for High-Speed Operations
International audienceThis paper presents a novel two-degree-of-freedom (DOF) translational parallel robot for high-speed applications named the IRSBot-2 (acronym for IRCCyN Spatial Robot with 2 DOF). Unlike most two-DOF robots dedicated to planar translational motions, this robot has two spatial kinematic chains which confers a very good intrinsic stiffness. First, the robot architecture is described. Then, its actuation and constraint singularities are analyzed. Finally, the IRSBot-2 is compared to its two-DOF counterparts based on elastostatic performances
Design of 3-legged XYZ compliant parallel manipulators with minimised parasitic rotations
This paper deals with the design of 3-legged distributed-compliance XYZ compliant parallel manipulators (CPMs) with minimised parasitic rotations, based on the kinematically decoupled 3-PPPRR (P: prismatic joint, and R: revolute joint) and 3-PPPR translational parallel mechanisms (TPMs). The designs are firstly proposed using the kinematic substitution approach, with the help of the stiffness center (SC) overlapping based approach. This is done by an appropriate embedded arrangement so that all of the SCs associated with the passive compliant modules overlap at the point where all of the input forces applied at the input stages intersect. Kinematostatic modelling and characteristic analysis are then carried out for the proposed large-range 3-PPPRR XYZ CPM with overlapping SCs. The results from finite element analysis (FEA) are compared to the characteristics found for the developed analytical models, as are experimental testing results (primary motion) from the prototyped 3-PPPRR XYZ CPM with overlapping SCs. Finally, issues on large-range motion and dynamics of such designs are discussed, as are possible improvements of the actuated compliant P joint. It is shown that the potential merits of the designs presented here include a) minimised parasitic rotations by only using three identical compliant legs; b) compact configurations and small size due to the use of embedded designs; c) approximately kinematostatically decoupled designs capable of easy controls; and d) monolithic fabrication for each leg using existing planar manufacturing technologies such as electric discharge machining (EDM)
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