scholarly journals Workspace Delineation of Cable-Actuated Parallel Manipulators

2004 ◽  
Author(s):  
Ethan Stump ◽  
Vijay Kumar
Keyword(s):  
Parallel Manipulator ◽  
Parallel Manipulators ◽  
Extensive Literature ◽  
Reachable Workspace ◽  
Planar Parallel Manipulator ◽  
Analytic Expressions

While there is extensive literature available on parallel manipulators in general, there has been much less attention given to cable-driven parallel manipulators. In this paper, we address the problem of analyzing the reachable workspace using the tools of semi-definite programming. We build on earlier work [1, 2] done using similar techniques by deriving limiting conditions that allow us to compute analytic expressions for the boundary of the reachable workspace. We illustrate this computation for a planar parallel manipulator with four actuators.

Workspace Representation of Parallel Manipulators Using the Finite Twist Method

1996 ◽  
Author(s):  
H. Singh ◽  
J. S. Dai ◽  
D. R. Kerr
Keyword(s):  
Parallel Manipulator ◽  
Parallel Manipulators ◽  
Image Space ◽  
End Effector ◽  
Unique Position ◽  
Reachable Workspace ◽  
Planar Parallel Manipulator ◽  
Position And Orientation ◽  
The Individual ◽  
Established Technique

Abstract A method has been developed that successfully represents the workspace of a parallel manipulator within a finite twist image space. A point in this space represents a unique position and orientation of the end effector. The method of analysis is based upon the established technique of simplifying the parallel manipulator, by modelling each leg as an independent serial manipulator. The workspace corresponding to each serial manipulator is mapped onto the image space to produce a hyper-volume. The intersection of the individual hyper-volumes represents the workspace of the complete parallel manipulator. Since the hyper-volume corresponds to all possible positions attainable by the end effector, this represents the reachable workspace. Within the reachable workspace there lies subsets of volumes in ⮲3 that correspond to all possible orientations attainable. Such volumes represent the dextrous workspace. Although the method is illustrated by the use of a Stewart platform, it is equally applicable to the general parallel manipulator. The method is demonstrated successfully by the use of a 3 legged, 3-DOF planar parallel manipulator.

Singularity robust inverse dynamics of planar 2-RPR parallel manipulators

2004 ◽  
Vol 218 (7) ◽  
pp. 721-730 ◽  
Author(s):  
S Kemal Ider
Keyword(s):  
Parallel Manipulator ◽  
Inverse Dynamics ◽  
Full Rank ◽  
Parallel Manipulators ◽  
Parallel Robots ◽  
Dynamic Equations ◽  
Revolute Joints ◽  
Planar Parallel Manipulator ◽  
Pass Through ◽  
Full Utilization

In planar parallel robots, limitations occur in the functional workspace because of interference of the legs with each other and because of drive singularities where the actuators lose control of the moving platform and the actuator forces grow without bounds. A 2-RPR (revolute, prismatic, revolute joints) planar parallel manipulator with two legs that minimizes the interference of the mechanical components is considered. Avoidance of the drive singularities is in general not desirable since it reduces the functional workspace. An inverse dynamics algorithm with singularity robustness is formulated allowing full utilization of the workspace. It is shown that if the trajectory is planned to satisfy certain conditions related to the consistency of the dynamic equations, the manipulator can pass through the drive singularities while the actuator forces remain stable. Furthermore, for finding the actuator forces in the vicinity of the singular positions a full rank modification of the dynamic equations is developed. A deployment motion is analysed to illustrate the proposed approach.

Path Tracking of Parallel Manipulators in the Presence of Force Singularity

2005 ◽  
Vol 127 (4) ◽  
pp. 550-563 ◽  
Author(s):  
C. K. Kevin Jui ◽  
Qiao Sun
Keyword(s):  
Motion Planning ◽  
Parallel Manipulator ◽  
Inverse Dynamics ◽  
Parallel Manipulators ◽  
Path Tracking ◽  
Singularity Avoidance ◽  
Design Complexity ◽  
Actuation Redundancy ◽  
Planar Parallel Manipulator ◽  
Simulation Results

Parallel manipulators are uncontrollable at force singularities due to the infeasibly high actuator forces required. Existing remedies include the application of actuation redundancy and motion planning for singularity avoidance. While actuation redundancy increases cost and design complexity, singularity avoidance reduces the effective workspace of a parallel manipulator. This article presents a path tracking type of approach to operate parallel manipulators when passing through force singularities. We study motion feasibility in the neighborhood of singularity and conclude that a parallel manipulator may track a path through singular poses if its velocity and acceleration are properly constrained. Techniques for path verification and tracking are presented, and an inverse dynamics algorithm that takes actuator bounds into account is examined. Simulation results for a planar parallel manipulator are given to demonstrate the details of this approach.

scholarly journals A Five-Bar Planar Parallel Manipulator with Two End-Effectors

2018 ◽  
Author(s):  
Jaime Gallardo-Alvarado ◽  
Ramon Rodriguez-Castro ◽  
Luciano Perez-Gonzalez ◽  
Carlos R. Aguilar-Najera ◽  
Alvaro Sanchez-Rodriguez
Keyword(s):  
Parallel Manipulator ◽  
Screw Theory ◽  
Parallel Manipulators ◽  
Intermediate Step ◽  
Euclidean Group ◽  
Planar Parallel Manipulator ◽  
Special Software ◽  
End Effectors ◽  
Klein Form

Parallel manipulators with multiple end-effectors bring us interesting advantages over conventional parallel manipulators such as improved manipulability, workspace and avoidance of singularities. In this work the kinematics of a five-bar planar parallel manipulator equipped with two end-effectors is approached by means of the theory of screws. As an intermediate step the displacement analysis of the robot is also investigated. The input-output equations of velocity and acceleration are systematically obtained by resorting to reciprocal-screw theory. In that regard the Klein form of the Lie algebra se(3) of the Euclidean group SE(3) plays a central role. In order to exemplify the method of kinematic analysis, a case study is included. Furthermore, the numerical results obtained by means of the theory of screws are confirmed with the aid of special software like ADAMS.TM

Workspace Analysis and Going through Singularities of 5-Bar Symmetric Planar Parallel Manipulator by Automated Selective Actuation Mechanism

2012 ◽  
Vol 588-589 ◽  
pp. 1664-1668
Author(s):  
Syam Sundar ◽  
Vijay S. Rathore ◽  
Manoj K. Sahi ◽  
V. Upendran ◽  
Anjan Kumar Dash
Keyword(s):  
Closed Form ◽  
Parallel Manipulator ◽  
Parallel Manipulators ◽  
New Approach ◽  
Serial Manipulators ◽  
Actuation Mechanism ◽  
Geometric Conditions ◽  
Workspace Analysis ◽  
Planar Parallel Manipulator ◽  
Planar Parallel Manipulators

In this article‚ a new approach is presented to determine the various shapes of workspaces of 5 bar symmetric planar parallel manipulators. Here the shape of the workspace is determined by the number of ways the workspaces of the two serial manipulators intersect with each other. Geometric conditions are established in each case and area of each shape of workspace is determined in closed form. Singularity is another important consideration in the design of parallel manipulators. In this paper, an approach is presented to go through the singularity points using an automatic selective actuation mechanism. A prototype 5-bar planar manipulator is fabricated along with an automatic selective actuation mechanism demonstrating the manipulator going through the singularity points.

Dynamic Performance With Control of a 2DOF Parallel Robot

2012 ◽  
Author(s):  
Gianmarc Coppola ◽  
Dan Zhang ◽  
Kefu Liu ◽  
Zhen Gao
Keyword(s):  
Dynamic Model ◽  
Performance Index ◽  
Parallel Manipulator ◽  
Dynamic Performance ◽  
Parallel Manipulators ◽  
Parallel Robot ◽  
Performance Study ◽  
Linear Controller ◽  
Reachable Workspace ◽  
And Control

In this work the dynamic performance and control of a 2DOF parallel robot is conducted. The study is partly motivated by large variations in dynamic performance and control within the reachable workspace of many parallel manipulators. The forward dynamic model of the robot is derived in detail. The connection method is directly utilized for this derivation. Subsequently, a dynamic performance study is undertaken. This reveals important information whilst using a forward dynamic model. A performance index is proposed to determine the variability of performance of the parallel manipulator. Then a trajectory-tracking scenario is undertaken using a linear controller. By means of control, the simulations illustrate the validity of the proposed index for parallel manipulators.

Comparative Kinematic Analysis and Design Optimization of Redundant and Nonredundant Planar Parallel Manipulators Intended for Haptic Use

Robotica ◽  
2019 ◽  
Vol 38 (8) ◽  
pp. 1463-1477 ◽  
Author(s):  
Houssem Saafi ◽  
Houssein Lamine
Keyword(s):  
Design Optimization ◽  
Kinematic Analysis ◽  
Parallel Manipulator ◽  
Kinematic Model ◽  
Parallel Manipulators ◽  
Geometric Parameters ◽  
Analysis And Design ◽  
Planar Parallel Manipulator ◽  
Forward Kinematic ◽  
Planar Parallel Manipulators

SUMMARYThis paper investigates a comparative kinematic analysis between nonredundant and redundant 2-Degree Of Freedom parallel manipulators. The nonredundant manipulator is based on the Five-Bar mechanism, and the redundant one is a 3-RRR planar parallel manipulator. This study is aimed to select the best structure for a haptic application. This latter requires a mechanism with a desired workspace of 10 cm × 10 cm and an admissible force of 5 N in all directions. The analysis criteria are the accuracy of the forward kinematic model and the required actuator torques. Thereby, the geometric parameters of the two structures are optimized in order to satisfy the required workspace such that parallel singularities are overcome. The analysis showed that the nonredundant optimally designed manipulator is more suitable for the haptic application.

Effect of Changing the Position of Tool Point on the Moving Platform on the Kinematics of a 3RRR Planar Parallel Manipulator

2014 ◽  
Vol 541-542 ◽  
pp. 792-797
Author(s):  
Roshdy Foaad Abo-Shanab
Keyword(s):  
Parallel Manipulator ◽  
Performance Criteria ◽  
Mobile Platform ◽  
Optimum Location ◽  
End Effector ◽  
Global Indices ◽  
Reachable Workspace ◽  
Planar Parallel Manipulator ◽  
Moving Platform ◽  
Structural Length

This paper discusses the effect of changing the location of the tool point, on the mobile platform, on the kinematics of a planar parallel manipulator. It is shown that changing the position of the end-effector greatly changes the shape and the area of the reachable workspace. Global conditioning index and the structural length index are used as global indices to find the optimum location of the end-effector on the mobile platform of a parallel manipulator. The results show that the performance criteria are varying in opposite directions, the dexterity is decreasing when the workspace area is increasing. Hence, the problem of optimal design becomes a problem of determination an acceptable compromise between the two requirements. The results of the present work show that the position of the end-effector on the mobile platform should be considered while optimizing the performance of a parallel manipulator.

Sensitivity Analysis of Planar Parallel Manipulators

2008 ◽  
Author(s):  
Ste´phane Caro ◽  
Nicolas Binaud ◽  
Philippe Wenger
Keyword(s):  
Sensitivity Analysis ◽  
Parallel Manipulator ◽  
Jacobian Matrix ◽  
Parallel Manipulators ◽  
Geometric Parameters ◽  
Sensitivity Coefficients ◽  
Planar Parallel Manipulator ◽  
Moving Platform ◽  
Conditioning Number ◽  
Planar Parallel Manipulators

This paper deals with the sensitivity analysis of planar parallel manipulators. A methodology is introduced to derive the sensitivity coefficients by means of the study of 3-RPR manipulators. As a matter of fact, the sensitivity coefficients of the pose of its moving platform to variations in the geometric parameters are expressed algebraically, the variations being defined both in Polar and Cartesian coordinates. The dexterity of the manipulator is also studied by means of the conditioning number of its normalized kinematic Jacobian matrix. As an illustrative example, the sensitivity of a symmetrical planar parallel manipulator is analyzed in detail. Finally, the accuracy of the manipulator is compared with its dexterity.

Dexterity and Adaptive Control of Planar Parallel Manipulators With and Without Redundant Actuation

2014 ◽  
Vol 10 (1) ◽  
Author(s):  
Weiwei Shang ◽  
Shuang Cong
Keyword(s):  
Adaptive Control ◽  
Parallel Manipulator ◽  
Adaptive Controller ◽  
Parallel Manipulators ◽  
The Other ◽  
Experimental Comparison ◽  
Redundant Actuation ◽  
Tracking Accuracy ◽  
Planar Parallel Manipulator ◽  
Planar Parallel Manipulators

The objective of this paper is to determine whether a planar parallel manipulator with redundant actuation has better tracking accuracy than a planar parallel manipulator without redundant actuation. The effects of the redundant actuation on tracking accuracy of parallel manipulators are studied by using two different experimental platforms. The first platform is the planar five-bar parallel manipulator with normal actuation, and the other one is the planar parallel manipulator with redundant actuation. The dexterity pictures and the kinematic configurations of the two platforms validate the kinematic advantages from the redundant actuation. In order to study the dynamic advantages of the redundant actuation further, a nonlinear adaptive controller is presented for the two platforms. The experimental comparison is implemented on two actual parallel manipulator platforms, and from the experimental results, one can find the tracking accuracy of the parallel manipulator with redundant actuation can be improved above 38% than that of the five-bar parallel manipulator without redundant actuation.

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