VIBRATION MODELING OF PARALLEL KINEMATIC MECHANISMS (PKMS) WITH FLEXIBLE LINKS: ADMISSIBLE SHAPE FUNCTIONS

2015 ◽  
Vol 39 (1) ◽  
pp. 97-113 ◽  
Author(s):  
Masih Mahmoodi ◽  
James K. Mills ◽  
Beno Benhabib
Keyword(s):  
Finite Element ◽  
Shape Functions ◽  
Flexible Links ◽  
Free Boundary Conditions ◽  
Knowing That ◽  
Parallel Kinematic ◽  
Moving Platform ◽  
Parallel Kinematic Mechanisms ◽  
Kinematic Mechanisms ◽  
Vibration Modeling

The accuracy of various admissible shape functions, for vibration modeling of flexible links of Parallel Kinematic Mechanisms (PKMs), is investigated as a function of the ratio of the mass of the moving platform to the mass of the link. Knowing that the commonly used shape functions based on “pinned”, “fixed”, or “free” boundary conditions do not incorporate the moving platform mass, “pinned-mass” and “fixed-mass” shape functions are presented herein, and are compared with finite-element based results for various mass ratios. The closest shape functions to the finite-element results are, then, utilized and compared with other shape functions in the subsequent vibration modeling to predict the tooltip response.

Workspace Analysis and the Effect of Geometric Parameters for Parallel Mechanisms of the N-UU Class

2018 ◽  
Author(s):  
Divya Shah ◽  
Giorgio Metta ◽  
Alberto Parmiggiani
Keyword(s):  
Specific Region ◽  
Geometric Parameters ◽  
Parallel Mechanisms ◽  
Workspace Analysis ◽  
Parallel Kinematic ◽  
Moving Platform ◽  
Parallel Kinematic Mechanisms ◽  
Roll Axis ◽  
Kinematic Mechanisms

N-UU class mechanisms, exemplified by the Omni-Wrist III, are compact parallel kinematic mechanisms (PKM) with large singularity free workspaces. These characteristics make them ideal for applications in robot wrists. This article presents the detailed kinematic and workspace analysis for four N-UU class mechanisms. More in detail, the equations defining the mechanism’s moving platform kinematics are derived as a function of the motion of the input links; these are then used to explore the mechanism’s workspace. These results are furthermore validated by comparing them to the results obtained from CAD-based simulations. The analyses suggests that the workspace of the mechanism is non-uniform, with a “warping” behaviour that occurs in an asymmetric fashion in a specific region of the workspace. Furthermore we show how the rotation of the input links, which mainly actuates the yaw and pitch angles of the mechanism, also causes unwanted coupled rotations along the roll axis.

Multiobjective optimization of parallel kinematic mechanisms by the genetic algorithms

Robotica ◽  
2011 ◽  
Vol 30 (5) ◽  
pp. 783-797 ◽  
Author(s):  
Ridha Kelaiaia ◽  
Olivier Company ◽  
Abdelouahab Zaatri
Keyword(s):  
Genetic Algorithms ◽  
Multiobjective Optimization ◽  
High Speed ◽  
Optimization Problem ◽  
Multiobjective Optimization Problem ◽  
Dimensional Synthesis ◽  
Nsga Ii ◽  
Parallel Kinematic ◽  
Parallel Kinematic Mechanisms ◽  
Kinematic Mechanisms

SUMMARYIt is well known that Parallel Kinematic Mechanisms (PKMs) have an intrinsic dynamic potential (very high speed and acceleration) with high precision and high stiffness. Nevertheless, the choice of optimal dimensions that provide the best performances remains a difficult task, since performances strongly depend on dimensions. On the other hand, there are many criteria of performance that must be taken into account for dimensional synthesis, and which are sometimes antagonist. This paper presents an approach of multiobjective optimization for PKMs that takes into account several criteria of performance simultaneously that have a direct impact on the dimensional synthesis of PKMs. We first present some criteria of performance such as the workspace, transmission speeds, stiffness, dexterity, precision, as well as dynamic dexterity. Secondly, we present the problem of dimensional synthesis, which will be defined as a multiobjective optimization problem. The method of genetic algorithms is used to solve this type of multiobjective optimization problem by means of NSGA-II and SPEA-II algorithms. Finally, based on a linear Delta architecture, we present an illustrative application of this methodology to a 3-axis machine tool in the context of manufacturing of automotive parts.

Study of Redundantly Actuated DELTA-Type Parallel Kinematic Mechanisms

2017 ◽  
pp. 291-298 ◽  
Author(s):  
Burkhard Corves ◽  
Seyed Amirreza Shahidi ◽  
Michael Lorenz ◽  
Sami Charaf Eddine ◽  
Mathias Hüsing
Keyword(s):  
Delta Type ◽  
Redundantly Actuated ◽  
Parallel Kinematic ◽  
Parallel Kinematic Mechanisms ◽  
Kinematic Mechanisms

Comparative Analysis of a Redundant Pentapod Parallel Kinematic Machine

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Arta Alagheband ◽  
Masih Mahmoodi ◽  
James K. Mills ◽  
Beno Benhabib
Keyword(s):  
Comparative Analysis ◽  
Dynamic Stiffness ◽  
Degree Of Freedom ◽  
Parallel Kinematic Machine ◽  
High Stiffness ◽  
Parallel Kinematic ◽  
Parallel Kinematic Mechanisms ◽  
Stiffness Characteristics ◽  
Kinematic Mechanisms ◽  
Platform Tilt

Parallel kinematic mechanisms (PKMs) provide high stiffness and compact structures that are suitable for a large number of applications, including 5-axis milling. This paper presents a new pentapod-based PKM with an additional redundant degree-of-freedom (DOF) capable of reaching platform tilt angles of at least 90 deg over a large workspace. The proposed new PKM has a 6DOF 4 × SPRR + 1 × PSPR architecture. It is compared herein to Metrom® Pentapod as well as to several other pertinent PKMs in terms of workspace and dynamic stiffness. It is shown that the proposed mechanism can yield a tangibly larger workspace volume, when compared to those PKMs, while maintaining its high stiffness characteristics.

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