scholarly journals Geometric Reformulation of 3-Fingered Force-Closure Condition

2006 ◽  
Author(s):  
A. Sudsang ◽  
T. Phoka
Keyword(s):  
Closure Condition ◽  
Force Closure

scholarly journals A Comparative Study of 4-Cable Planar Manipulators Based on Cylindrical Algebraic Decomposition

2011 ◽  
Author(s):  
Damien Chablat ◽  
Erika Ottaviano ◽  
Guillaume Moroz
Keyword(s):  
Jacobian Matrix ◽  
Parallel Robots ◽  
Feasibility Problem ◽  
Closure Problem ◽  
Mobile Platforms ◽  
Implicit Representation ◽  
Closure Condition ◽  
Cylindrical Algebraic Decomposition ◽  
Force Closure ◽  
Cable Force

The aim of this paper is to present a systematic method for verifying the force-closure condition for general 3-DOF fully-constrained cable manipulators with four cables as based on the CAD (Cylindrical Algebraic Decomposition). A fundamental requirement for a cable manipulator to be fully controllable is that all its cables must be in tension at any working configurations. In other words, all the cable forces must be positive (assuming a positive cable force representing a tension and a negative cable force being a compression). Such a force feasibility problem is indeed referred to a force-closure problem (also called vector-closure problem assuming that the vectors of interest are the row vectors of the Jacobian matrix of the manipulator). The boundaries of the workspace can be obtained by the study of the Jacobian matrix of the manipulator. Therefore, this is equivalent to study the singularity conditions of four 3-RPR parallel robots. By using algebraic tools, it is possible to determine the singularity surfaces and their intersections yielding the workspace. Thus, it will be shown that the use of the CAD allows to get an implicit representation of the workspace as a set of cells. A comparative workspace analysis of three designs of mobile platforms, a line, a square and a triangle will be presented and discussed in this paper for a planar 4-cable fully-constrained robot.

An Enhanced Ray-Shooting Approach to Force-Closure Problems

2006 ◽  
Vol 128 (4) ◽  
pp. 960-968 ◽  
Author(s):  
Yu Zheng ◽  
Wen-Han Qian
Keyword(s):  
Convex Hull ◽  
Quality Evaluation ◽  
High Efficiency ◽  
Stability Index ◽  
Test Quality ◽  
Closure Condition ◽  
Grasp Planning ◽  
Ray Shooting ◽  
Grasp Stability ◽  
Force Closure

Force-closure is a fundamental topic in grasping research. Relevant problems include force-closure test, quality evaluation, and grasp planning. Implementing the well-known force-closure condition that the origin of the wrench space lies in the interior of the convex hull of primitive wrenches, Liu presented a ray-shooting approach to force-closure test. Because of its high efficiency in 3D work space and no limitation on the contact number of a grasp, this approach is advanced. Achieving some new results of convex analysis, this paper enhances the above approach in three aspects. (a) The exactness is completed. In order to avoid trouble or mistakes, the dimension of the convex hull of primitive wrenches is taken into account, which is always ignored until now. (b) The efficiency is increased. A shortcut which skips some steps of the original force-closure test is found. (c) The scope is extended. Our simplified ray-shooting approach yields a grasp stability index suitable for grasp planning. Numerical examples in fixturing and grasping show the enhancement superiority.

THE IMPLEMENTATION OF THE PRINCIPLE OF SEPARATION OF POWER CIRCUIT IN THE ADAPTIVE FRICTION CLUTCHES

2020 ◽  
Author(s):  
V. E Zinoviev ◽  
Keyword(s):  
Friction Coefficient ◽  
Feedback Gain ◽  
Power Circuit ◽  
Load Characteristic ◽  
The Third ◽  
Force Closure ◽  
Friction Clutch

For the third variant of the adaptive friction clutch with a separate force closure, the boundaries of the change in the value of the feedback gain are determined, within which the clutch has the highest accuracy of operation, if its load characteristic is realized in the form of a curve monotonically increasing in the range of the friction coefficient values. A variant of separate power closure is developed, which provides for the introduction of an additional spring into the clutch design in the closure node of the thorn pairs of the main friction group.

EFFICIENT GRASP PLANNING WITH REACHABILITY ANALYSIS

2011 ◽  
Vol 08 (04) ◽  
pp. 761-775 ◽  
Author(s):  
ZHIXING XUE ◽  
RUEDIGER DILLMANN
Keyword(s):  
Efficient Algorithm ◽  
Reachability Analysis ◽  
Robotic Arm ◽  
Robotic Hands ◽  
Grasp Planning ◽  
Grasping Forces ◽  
Force Closure ◽  
Geometrical Information ◽  
Kinematic Information

Grasping can be seen as two steps: placing the hand at a grasping pose and closing the fingers. In this paper, we introduce an efficient algorithm for grasping pose generation. By the use of preshaping and eigen-grasping actions, the dimension of the space of possible hand configurations is reduced. The object to be grasped is decomposed into boxes of a discrete set of different sizes. By performing finger reachability analysis on the boxes, the kinematic feasibility of a grasp can be determined. If a reachable grasp is force-closure and can be performed by the robotic arm, its grasping forces are optimized and can be executed. The novelty of our algorithm is that it takes into account both the object geometrical information and the kinematic information of the hand to determine the grasping pose, so that a reachable grasping pose can be found very quickly. Real experiments with two different robotic hands show the efficiency and feasibility of our method.

Calculation of Contact Forces of Large-Scale Heavy Forging Manipulator Grippers

2009 ◽  
Vol 419-420 ◽  
pp. 645-648 ◽  
Author(s):  
Qun Ming Li ◽  
Dan Gao ◽  
Hua Deng
Keyword(s):  
Large Scale ◽  
Optimization Method ◽  
Contact Forces ◽  
Robotic Hand ◽  
Closure Condition ◽  
Contact Points ◽  
Robot Hands ◽  
Calculation Results ◽  
Forging Manipulator ◽  
Gripping Force

Different from dexterous robotic hands, the gripper of heavy forging manipulator is an underconstrained mechanism whose tongs are free in a small wiggling range. However, for both a dexterous robotic hand and a heavy gripper, the force closure condition: the force and the torque equilibrium, must be satisfied without exception to maintain the grasping/gripping stability. This paper presents a gripping model for the heavy forging gripper with equivalent friction points, which is similar to a grasp model of multifingered robot hands including four contact points. A gripping force optimization method is proposed for the calculation of contact forces between gripper tongs and forged object. The comparison between the calculation results and the experimental results demonstrates the effectiveness of the proposed calculation method.

Simulation of Planar Dynamic Mechanical Systems With Changing Topologies: Part I — Characterization and Prediction of the Kinematic Constraint Changes

1987 ◽  
Author(s):  
B. J. Gilmore ◽  
R. J. Cipra
Keyword(s):  
Equations Of Motion ◽  
Mechanical Systems ◽  
Rigid Bodies ◽  
State Variables ◽  
Kinematic Constraint ◽  
Kinematic Constraints ◽  
Force Closure ◽  
Simulation Strategy ◽  
Reaction Forces ◽  
Discontinuous Equations

Abstract Due to changes in the kinematic constraints, many mechanical systems are described by discontinuous equations of motion. This paper addresses those changes in the kinematic constraints which are caused by planar bodies contacting and separating. A strategy to automatically predict and detect the kinematic constraint changes, which are functions of the system dynamics, is presented in Part I. The strategy employs the concepts of point to line contact kinematic constraints, force closure, and ray firing together with the information provided by the rigid bodies’ boundary descriptions, state variables, and reaction forces to characterize the kinematic constraint changes. Since the strategy automatically predicts and detects constraint changes, it is capable of simulating mechanical systems with unpredictable or unforeseen changes in topology. Part II presents the implementation of the characterizations into a simulation strategy and presents examples.

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