A Study on Vibrations of Hexarot-Based High-G Centrifugal Simulators

Robotica ◽  
2019 ◽  
Vol 38 (2) ◽  
pp. 299-316 ◽  
Author(s):  
Siamak Pedrammehr ◽  
Houshyar Asadi ◽  
Saeid Nahavandi
Keyword(s):  
Dynamic Model ◽  
Virtual Work ◽  
Viscous Friction ◽  
Stability Index ◽  
Flexible Manipulator ◽  
Kinematics And Dynamics ◽  
Principle Of Virtual Work ◽  
End Effector ◽  
Dynamic Formulation ◽  
Different Parts

SummaryThis paper investigates the vibrations of hexarot simulators. The generalized modeling of kinematics and dynamics formulation of a hexarot mechanism is addressed. This model considers the flexible manipulator with the base motion. The dynamic formulation has been developed based on the principle of virtual work. The dynamic model consists of the stiffness of the different parts of the mechanism, the effects of gravity and inertia, torque and force related to the joints viscous friction. Finally, the response of the end effector at various frequencies has been presented, and the vibrations of the mechanism and the dynamic stability index have been investigated.

Dynamic Analysis of Flexible Manipulator Arms With Distributed Viscoelastic Damping

1997 ◽  
Vol 119 (4) ◽  
pp. 831-833 ◽  
Author(s):  
Fan Zijie ◽  
Lu Bingheng ◽  
C. H. Ku
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Dynamic Analysis ◽  
Virtual Work ◽  
Robot Manipulators ◽  
Flexible Manipulator ◽  
Viscoelastic Damping ◽  
Principle Of Virtual Work ◽  
Flexible Robot ◽  
Damping Treatments

The main objective of this work is to predict the effect of distributed viscoelastic damping on the dynamic response of multilink flexible robot manipulators. A general approach, based on the principle of virtual work, is presented for the modeling of flexible robot arms with distributed viscoelastic damping. The finite element equations are developed, and a recurrence formulation for numerical integration of these equations is obtained. It is demonstrated, by a numerical example, that the viscoelastic damping treatments have a significant effect on the dynamic response of flexible robot manipulators.

Dynamic Modeling of Overconstrained Parallel Robot

2013 ◽  
Vol 373-375 ◽  
pp. 34-37
Author(s):  
Jian Xin Yang ◽  
Zhen Tao Liu ◽  
Jian Wei Sun
Keyword(s):  
Dynamic Modeling ◽  
Virtual Work ◽  
Parallel Robot ◽  
Tree Structure ◽  
Kinematics And Dynamics ◽  
Dynamics Analysis ◽  
Forward Dynamics ◽  
Principle Of Virtual Work ◽  
Closed Form Solutions ◽  
Dynamics Models

The dynamic modeling method for parallel robot based on the principle of virtual work and equivalent tree structure is proposed by taking off the platform and the chains as well as degenerating parallel robot into a tree structure, the closed-form solutions for the inverse and forward dynamics models of parallel robot are derived. The method is applied on kinematics and dynamics analysis of a representative 3-RRR spherical parallel robot.

Kinematic Analysis and Design of Planar Parallel Mechanisms Actuated With Cables

2000 ◽  
Author(s):  
Guillaume Barrette ◽  
Clément M. Gosselin
Keyword(s):  
Virtual Work ◽  
Parametric Representation ◽  
Dynamic State ◽  
Parallel Mechanisms ◽  
Principle Of Virtual Work ◽  
Systematic Analysis ◽  
End Effector ◽  
Analysis And Design ◽  
Spring Mechanism

Abstract In this paper, we present a general and systematic analysis of planar parallel mechanisms actuated with cables. The equations for the velocities are derived, and the forces in the cables are obtained by the principle of virtual work. Then, a detailed analysis of the workspace is performed and an analytical method for the determination of the boundaries of an x-y two-dimensional subset is proposed. The new notion of dynamic workspace is denned, as its shape depends on the accelerations of the end-effector. We demonstrate that any subset of the workspace can be considered as a combination of three-cable sub-workspaces, with boundaries being of two kinds: two-cable equilibrium loci and three-cable singularity loci. By using a parametric representation, we see that for the x-y workspace of a simple no-spring mechanism, the two-cable equilibrium loci represent a hyperbolic section, degenerating, in some particular cases, to one or two linear segments. Examples of such loci are presented. We use quadratic programming to choose which sections of the curves constitute the boundaries of the workspace for any particular dynamic state. A detailed example of workspace determination is included for a six-cable mechanism.

Determination of the Dynamic Workspace of Cable-Driven Planar Parallel Mechanisms

2005 ◽  
Vol 127 (2) ◽  
pp. 242-248 ◽  
Author(s):  
Guillaume Barrette ◽  
Cle´ment M. Gosselin
Keyword(s):  
Virtual Work ◽  
Parametric Representation ◽  
Dynamic State ◽  
Two Dimensional ◽  
Parallel Mechanisms ◽  
Principle Of Virtual Work ◽  
Systematic Analysis ◽  
End Effector ◽  
Spring Mechanism

In this paper, we present a general and systematic analysis of cable-driven planar parallel mechanisms. The equations for the velocities are derived, and the forces in the cables are obtained by the principle of virtual work. Then, a detailed analysis of the workspace is performed and an analytical method for the determination of the boundaries of an x-y two-dimensional subset is proposed. The new notion of dynamic workspace is defined, as its shape depends on the accelerations of the end-effector. We demonstrate that any subset of the workspace can be considered as a combination of three-cable subworkspaces, with boundaries being of two kinds: two-cable equilibrium loci and three-cable singularity loci. By using a parametric representation, we see that for the x-y workspace of a simple no-spring mechanism, the two-cable equilibrium loci represent a hyperbolic section, degenerating, in some particular cases, to one or two linear segments. Examples of such loci are presented. We use quadratic programming to choose which sections of the curves constitute the boundaries of the workspace for any particular dynamic state. A detailed example of workspace determination is included for a six-cable mechanism.

A method for selecting driving system parameters of a new electric shovel's excavating mechanism with three-DOF

2011 ◽  
Vol 225 (11) ◽  
pp. 2661-2672 ◽  
Author(s):  
B Wei ◽  
F Gao ◽  
J Chen ◽  
J He ◽  
X Zhao
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Virtual Work ◽  
Transmission Ratio ◽  
Principle Of Virtual Work ◽  
Driving System ◽  
Generalized Coordinates ◽  
System Parameters ◽  
Three Degrees Of Freedom ◽  
Selection Of

Driving system parameters include motor parameters and transmission ratio of the reducer. In this study, a new three-degrees-of-freedom parallel excavating mechanism of electric shovel is analysed for the selection of its driving system which consists of three sub-driving parts. Based on the principle of virtual work in the form of generalized coordinates, the dynamic model of the excavating mechanism is established to calculate the external inertia loads and force (or torque) loads. For this parallel excavating mechanism which has three sub-drives, the external inertia loads cannot be fully divided into three independent parts with respect to these three sub-driving systems. Hence, the dynamic model of the system is employed to get loads characteristic of three sub-driving systems in the excavating process. Thus, the parameters' range of the motors can be obtained and then the best transmission ratio of every reducer can be obtained.

Analyses of the stiffness and elastic deformation of a 2(3-SPR) serial—parallel manipulator

2009 ◽  
Vol 223 (3) ◽  
pp. 189-198 ◽  
Author(s):  
Y Lu ◽  
B Hu ◽  
J Yu
Keyword(s):  
Elastic Deformation ◽  
Machine Tools ◽  
Parallel Manipulator ◽  
Virtual Work ◽  
Parallel Manipulators ◽  
Robot Arm ◽  
Principle Of Virtual Work ◽  
Compliance Matrix ◽  
End Effector ◽  
Machining Speed

Stiffness is one of the important indices for evaluating the performances of serial—parallel manipulators (S—PMs), particularly when the S—PMs are used as machine tools and the robot arm/leg, and higher stiffness allows higher machining speed with higher accuracy of the end-effector. In this article, the stiffness and the elastic deformation of a 2(3-SPR) S—PM are studied systematically. First, a 2(3-SPR) S—PM, including an upper 3-SPR parallel manipulator (PM) and a lower 3-SPR PM, is constructed, and its characteristics are analysed. Second, some formulae for solving the elastic deformation and the compliance matrix of the active legs are derived from the available kinematics/statics of this S—PM. Third, based on the principle of virtual work and the compliance matrix of the active legs, the elastic deformation and the total stiffness matrix of this S—PM are solved and analysed.

Kinematics and dynamics of 2(3-RPS) manipulators by means of screw theory and the principle of virtual work

2008 ◽  
Vol 43 (10) ◽  
pp. 1281-1294 ◽  
Author(s):  
Jaime Gallardo-Alvarado ◽  
Carlos R. Aguilar-Nájera ◽  
Luis Casique-Rosas ◽  
José M. Rico-Martínez ◽  
Md. Nazrul Islam
Keyword(s):  
Screw Theory ◽  
Virtual Work ◽  
Kinematics And Dynamics ◽  
Principle Of Virtual Work

On the Mechanical Behavior of the Orthotropic Cord-Rubber Composite

1976 ◽  
Vol 4 (4) ◽  
pp. 219-232 ◽  
Author(s):  
Ö. Pósfalvi
Keyword(s):  
Mechanical Behavior ◽  
Uniaxial Tension ◽  
Elastic Properties ◽  
Large Deformations ◽  
Virtual Work ◽  
Poisson's Ratio ◽  
Principle Of Virtual Work ◽  
Effective Elastic Properties ◽  
Rubber Composite ◽  
Mooney Equation

Abstract The effective elastic properties of the cord-rubber composite are deduced from the principle of virtual work. Such a composite must be compliant in the noncord directions and therefore undergo large deformations. The Rivlin-Mooney equation is used to derive the effective Poisson's ratio and Young's modulus of the composite and as a basis for their measurement in uniaxial tension.

scholarly journals Discrete element model for general polyhedra

2021 ◽  
Author(s):  
Alfredo Gay Neto ◽  
Peter Wriggers
Keyword(s):  
Frictional Contact ◽  
Virtual Work ◽  
Particle Surface ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Principle Of Virtual Work ◽  
Dynamics Model ◽  
Railway Ballast ◽  
Multibody Dynamics Model

AbstractWe present a version of the Discrete Element Method considering the particles as rigid polyhedra. The Principle of Virtual Work is employed as basis for a multibody dynamics model. Each particle surface is split into sub-regions, which are tracked for contact with other sub-regions of neighboring particles. Contact interactions are modeled pointwise, considering vertex-face, edge-edge, vertex-edge and vertex-vertex interactions. General polyhedra with triangular faces are considered as particles, permitting multiple pointwise interactions which are automatically detected along the model evolution. We propose a combined interface law composed of a penalty and a barrier approach, to fulfill the contact constraints. Numerical examples demonstrate that the model can handle normal and frictional contact effects in a robust manner. These include simulations of convex and non-convex particles, showing the potential of applicability to materials with complex shaped particles such as sand and railway ballast.

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