Analysis of Active Joint Failure in Parallel Robot Manipulators

2004 ◽  
Vol 126 (6) ◽  
pp. 959-968 ◽  
Author(s):  
Mahir Hassan ◽  
Leila Notash
Keyword(s):  
Jacobian Matrix ◽  
Null Space ◽  
Robot Manipulators ◽  
Parallel Manipulators ◽  
Parallel Robot ◽  
Task Space ◽  
Active Joint ◽  
Joint Failure ◽  
Space Vectors ◽  
Six Degree Of Freedom

In this study, the effect of active joint failure on the mobility, velocity, and static force of parallel robot manipulators is investigated. Two catastrophic active joint failure types are considered: joint jam and actuator force loss. To investigate the effect of failure on mobility, the Gru¨bler’s mobility equation is modified to take into account the kinematic constraints imposed by various branches in the manipulator. In the case of joint jam, the manipulator loses the ability to move and apply force in a specific portion of its task space; while in the case of actuator force loss, the manipulator gains an unconstrained motion in a specific portion of the task space in which an externally applied force cannot be resisted by the actuator forces. The effect of joint jam and actuator force loss on the velocity and on the force capabilities of parallel manipulators is investigated by examining the change in the Jacobian matrix, its inverse, and transposes. It is shown that the reduced velocity and force capabilities after joint jam and loss of actuator force could be determined using the null space vectors of the transpose of the Jacobian matrix and its inverse. Computer simulation is conducted to demonstrate the application of the developed methodology in determining the post-failure trajectory of a 3-3 six-degree-of-freedom Stewart-Gough manipulator, when encountering active joint jam and actuator force loss.

MOTION RECOVERY AFTER JOINT FAILURE IN PARALLEL MANIPULATORS

2011 ◽  
Vol 35 (4) ◽  
pp. 559-571 ◽  
Author(s):  
Leila Notash
Keyword(s):  
Failure Modes ◽  
Jacobian Matrix ◽  
Null Space ◽  
Parallel Manipulators ◽  
Point Of View ◽  
Partial Recovery ◽  
Joint Failure ◽  
Motion Recovery ◽  
Motion Performance ◽  
Planar Parallel Manipulators

In this paper, the failure of parallel manipulators is investigated. Failure modes of parallel manipulators and their causes and effects from the kinematics point of view are discussed. Methodologies for investigating the effect of failures, due to joint failure or singularity, on the motion performance of manipulators are presented, and the criteria for full and partial recovery from these failures are established. The proposed methodologies are based on the projection of the lost motion onto the orthogonal complement of the null space of the Jacobian matrix after failure. The procedure is simulated for planar parallel manipulators to examine if after joint failure the required motion of manipulator could be fully recovered; as well as to calculate the corrections to the motion of remaining joints for recovering the lost motion.

Kinematics and Singularity Analysis of the Hexaglide Parallel Robot

2008 ◽  
Author(s):  
Mansour Abtahi ◽  
Hodjat Pendar ◽  
Aria Alasty ◽  
Gholamreza Vossoughi
Keyword(s):  
Machine Tools ◽  
Parallel Manipulator ◽  
High Speed ◽  
Jacobian Matrix ◽  
Parallel Manipulators ◽  
Parallel Robot ◽  
Singularity Analysis ◽  
The Past ◽  
Different Types ◽  
Forward Kinematic

In the past few years, parallel manipulators have become increasingly popular in industry, especially, in the field of machine tools. Hexaglide is a 6 DOF parallel manipulator that can be used as a high speed milling machine. In this paper, the kinematics and singularity of Hexaglide parallel manipulator are studied systematically. At first, this robot has been modeled and its inverse and forward kinematic problems have been solved. Then, formulas for solving inverse velocity are derived and Jacobian matrix is obtained. After that, three different types of singularity for this type of robot have been investigated. Finally a numerical example is presented.

Actuation Redundancy as a Way to Improve the Acceleration Capabilities of 3T and 3T1R Pick-and-Place Parallel Manipulators

2010 ◽  
Vol 2 (4) ◽  
Author(s):  
David Corbel ◽  
Marc Gouttefarde ◽  
Olivier Company ◽  
François Pierrot
Keyword(s):  
Dynamic Model ◽  
Dynamic Capabilities ◽  
Robot Manipulators ◽  
Parallel Manipulators ◽  
Parallel Robot ◽  
Actuation Redundancy ◽  
High Acceleration ◽  
Pick And Place ◽  
Very High

This paper analyzes the possible contribution of actuation redundancy in obtaining very high acceleration with parallel robot manipulators. This study is based on redundant and nonredundant Delta/Par4-like manipulators, which are frequently used for pick-and-place applications, and addresses the cases of translational manipulators (also called 3T manipulators) and manipulators with Schoenflies motions (also called 3T1R manipulators). A dynamic model, valid for both redundant and nonredundant manipulators, is used to analyze the moving platform’s acceleration capabilities: (i) at zero speed and in any direction and (ii) at zero speed in the “best” direction. The results show that actuation redundancy makes it possible to homogenize dynamic capabilities throughout the workspace and to increase the moving platform’s accelerations. Designs of redundant Delta/Par4-like manipulators capable of high acceleration pick-and-place trajectories are presented for both 3T and 3T1R manipulators.

Task-Space Control of Robot Manipulators With Null-Space Compliance

2014 ◽  
Vol 30 (2) ◽  
pp. 493-506 ◽  
Author(s):  
Hamid Sadeghian ◽  
Luigi Villani ◽  
Mehdi Keshmiri ◽  
Bruno Siciliano
Keyword(s):  
Null Space ◽  
Robot Manipulators ◽  
Task Space ◽  
Task Space Control

Configuration Bifurcations Analysis of Six Degree-of-Freedom Symmetrical Stewart Parallel Mechanisms

2005 ◽  
Vol 127 (1) ◽  
pp. 70-77 ◽  
Author(s):  
Yu-Xin Wang ◽  
Yi-Ming Wang
Keyword(s):  
Matrix Method ◽  
Parallel Manipulator ◽  
Jacobian Matrix ◽  
Parallel Manipulators ◽  
Multiple Point ◽  
Parallel Mechanisms ◽  
Variation Trend ◽  
Bifurcation Points ◽  
Movable Platform ◽  
Six Degree Of Freedom

The configuration bifurcations of Stewart parallel manipulators at singular positions induce the uncertainty of the moving trends of the manipulative platform. The Jacobian matrix method can determine the singular position of Stewart manipulators, but it cannot determine the configuration variation trend in the vicinity of the singular position. In order to investigate the concrete motion behaviors of the Stewart parallel manipulator at singular positions, we construct the algorithm for determining all the configuration branches and bifurcation points. Through detailed investigations of configuration bifurcation characteristics, we have found that with a decrease of the extensible legs’ length, the bifurcation points of configuration branches of the movable platform get together gradually and the bifurcation type changes from turning to dual-point bifurcation, and then, finally, it becomes multiple-point bifurcation.

Natural Dynamics of Robot Manipulators in the Presence of Obstacles

1991 ◽  
Vol 113 (1) ◽  
pp. 170-174
Author(s):  
T. Jia ◽  
F. M. L. Amirouche
Keyword(s):  
Collision Detection ◽  
Jacobian Matrix ◽  
Null Space ◽  
Robot Manipulators ◽  
Dynamic Control ◽  
Inequality Constraints ◽  
Dimensional Problem ◽  
Constraint Equations ◽  
Natural Dynamics ◽  
Natural Dynamic

This paper presents the natural dynamic control problem of robot manipulators and its application to collision avoidance and path planning. A set of moving convex obstacles (or polyhedron) are modeled to achieve the desired conditions for collision detection and avoidance. The conditions represent a set of inequality constraints which are automatically incorporated to assure collision free motion. A minimum dimensional problem is achieved through the use of the null space of the Jacobian matrix associated with the constraint equations. A simple example to illustrate the procedures developed above is given.

A new computation method for the force-closure workspace of cable-driven parallel manipulators

Robotica ◽  
2014 ◽  
Vol 33 (3) ◽  
pp. 537-547 ◽  
Author(s):  
Bo Ouyang ◽  
Wei-Wei Shang
Keyword(s):  
Null Space ◽  
Parallel Manipulators ◽  
New Method ◽  
Linear Matrix ◽  
Computation Method ◽  
Detailed Calculation ◽  
Simulation Experiments ◽  
Force Closure ◽  
Moving Platform ◽  
Six Degree Of Freedom

SUMMARYFor cable-driven parallel manipulators (CDPMs), it is known that maintaining positive cable tension is critical in constraining the moving platform. Hence, the force-closure workspace of CDPMs represents a set of poses where the cable tensions can balance arbitrary external wrench applied on the moving platform, proposed by researchers. A new computation method for the force-closure workspace of CDPMs is developed in this paper, and the new method is realized by calculating the null space of the structure matrix and solving the linear matrix inequalities. The detailed calculation procedures of the force-closure workspace for the incompletely restrained, completely restrained, and redundantly restrained CDPMs are given, respectively, and the advantages of the new method are analyzed according to the time complexity. The simulation experiments of the force-closure workspace computation are implemented on a six-degree of freedom (6-DOF) CDPM with eight cables, and then the superiority of the new method over the existing algorithm is studied.

WORKSPACE OF WIRE-ACTUATED PARALLEL MANIPULATORS AND VARIATIONS IN DESIGN PARAMETERS

2013 ◽  
Vol 37 (2) ◽  
pp. 215-229 ◽  
Author(s):  
Vahid Nazari ◽  
Leila Notash
Keyword(s):  
Jacobian Matrix ◽  
Null Space ◽  
Parallel Manipulators ◽  
Mobile Platform ◽  
Design Parameters ◽  
Balance Equations ◽  
Size And Shape ◽  
Workspace Analysis ◽  
Force Moment ◽  
Simulation Results

The purpose of the paper is to investigate the effect of small variations (uncertainties) and large variations in design parameters on the size and shape of the workspace of the wire-actuated parallel manipulators. The static force/moment balance equations, taking into account the null space of the Jacobian matrix, are used for the workspace analysis. The parameters examined include: the winding direction of wires on the pulleys; the radius of the pulley; the orientation, radius, and mass of the mobile platform; the peg length; and the ratio of the peg radii at the entrance and exit. Also, the effect of the geometric arrangement of wire attachment points and the number of wire connection points on the mobile platform, on the size and shape of the workspace is considered. The simulation results show the effect of small and large variations in the aforementioned parameters on the workspace of wire-actuated parallel manipulators without and with gravity.

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