136 research outputs found
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
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
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
A simple and visually orientated approach for type synthesis of overconstrained 1T2R parallel mechanisms
This paper presents a simple and highly visual approach for the type synthesis of a family of overconstrained parallel mechanisms that have one translational and two rotational movement capabilities. It considers, especially, mechanisms offering the accuracy and dynamic response needed for machining applications. This family features a spatial limb plus a member of a class of planar symmetrical linkages, the latter connected by a revolute joint either to the machine frame at its base link or to the platform at its output link. Criteria for selecting suitable structures from among numerous candidates are proposed by considering the realistic practical requirements for reconfigurability, movement capability, rational component design and so on. It concludes that a few can simultaneously fulfil the proposed criteria, even though a variety of structures have been presented in the literature. Exploitation of the proposed structures and evaluation criteria then leads to a novel five degrees of freedom hybrid module named TriMule. A significant potential advantage of the TriMule over the Tricept arises because all the joints connecting the base link and the machine frame can be integrated into one single, compact part, leading to a lightweight, cost effective and flexible design particularly suitable for configuring various robotized manufacturing cells
Simple examples of dual coupling networks
Most mechanisms are both
underconstrained and overconstrained. The motions
attributable to underconstraint can be seen so that they
are easily imagined from a drawing whereas actions
attributable to overconstraint cannot. Dual coupling
networks have the property that the action and motion
systems of one are transposed in the other. So, by finding
the dual of a mechanism, actions attributable to
overconstraint become motions in its dual that can be
imagined. Earlier work cited explains the methodology
and validates the theory mathematically: this paper
provides some simple examples
Dexterity, workspace and performance analysis of the conceptual design of a novel three-legged, redundant, lightweight, compliant, serial-parallel robot
In this article, the mechanical design and analysis of a novel three-legged, agile robot with passively compliant 4-degrees-of-freedom legs, comprising a hybrid topology of serial, planar and spherical parallel structures, is presented. The design aims to combine the established principle of the Spring Loaded Inverted Pendulum model for energy efficient locomotion with the accuracy and strength of parallel mechanisms for manipulation tasks. The study involves several kinematics and Jacobian based analyses that specifically evaluate the application of a non-overconstrained spherical parallel manipulator as a robot hip joint, decoupling impact forces and actuation torques, suitable for the requirements of legged locomotion. The dexterity is investigated with respect to joint limits and workspace boundary contours, showing that the mechanism stays well conditioned and allows for a sufficient range of motion. Based on the functional redundancy of the constrained serial-parallel architecture it is furthermore revealed that the robot allows for the exploitation of optimal leg postures, resulting in the possible optimization of actuator load distribution and accuracy improvements. Consequently, the workspace of the robot torso as additional end-effector is investigated for the possible application of object manipulation tasks. Results reveal the existence of a sufficient volume applicable for spatial motion of the torso in the statically stable tripodal posture. In addition, a critical load estimation is derived, which yields a posture dependent performance index that evaluates the risks of overload situations for the individual actuators
Topological analysis of a novel compact omnidirectional three-legged robot with parallel hip structures regarding locomotion capability and load distribution
In this study, a novel design for a compact, lightweight, agile, omnidirectional three-legged robot involving legs with four degrees of freedom, utilizing an spherical parallel mechanism with an additional non-redundant central support joint for the robot hip structure is proposed. The general design and conceptual ideas for the robot are presented, targeting a close match of the well-known SLIP-model. CAD models, 3d-printed prototypes, and proof-of-concept multi-body simulations are shown, investigating the feasibility to employ a geometrically dense spherical parallel manipulator with completely spherically shaped shell-type parts for the highly force-loaded application in the legged robot hip mechanism. Furthermore, in this study, an analytic expression is derived, yielding the calculation of stress forces acting inside the linkage structures, by directly constructing the manipulator hip Jacobian inside the force domain
Stiffness modelling of parallelogram-based parallel manipulators
International audienceThe paper presents a methodology to enhance the stiffness analysis of parallel manipulators with parallelogram-based linkage. It directly takes into account the influence of the external loading and allows computing both the non-linear ``load-deflection" relation and relevant rank-deficient stiffness matrix. An equivalent bar-type pseudo-rigid model is also proposed to describe the parallelogram stiffness by means of five mutually coupled virtual springs. The contributions of this paper are highlighted with a parallelogram-type linkage used in a manipulator from the Orthoglide family
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