Stiffness Analysis for a Novel Parallel-Robot Based High-Precision Flexible Assembly Fixture

2007 ◽  
Vol 364-366 ◽  
pp. 327-332 ◽  
Author(s):  
Hong Jian Yu ◽  
Bing Li ◽  
Xiao Jun Yang ◽  
Ying Hu ◽  
Hong Hu
Keyword(s):  
Stiffness Matrix ◽  
Screw Theory ◽  
System Modeling ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Stiffness Analysis ◽  
Flexible Assembly ◽  
Global Stiffness Matrix ◽  
The Relationship ◽  
Assembly Fixture

In this paper, a novel parallel mechanism (3-RRRS/UPR) used in flexible fixture with configuration composed of two parallel robots (2-RR and 3-RRRS/ UPR) is presented. First, system modeling including the mobility study is conducted. Then a novel methodology is proposed that makes use of screw theory to analyze the deformation and stiffness of the mechanism: firstly we identified the existence of the deformation of the subchain, in terms of the relationship between the effective screw and deformation screw; then we took the deformation as an infinitesimal motion of the mechanism, and the stiffness matrix corresponding to the deformation can be deduced. Finally the global stiffness matrix of the whole mechanism is modeled by assembling different stiffness characters based on the presented methodology.

Type synthesis of coordinated multi-robot system based on parallel thought

2018 ◽  
Vol 42 (2) ◽  
pp. 164-176 ◽  
Author(s):  
Wanqiang Xi ◽  
Bai Chen ◽  
Yaoyao Wang ◽  
Feng Ju
Keyword(s):  
Degrees Of Freedom ◽  
Screw Theory ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Type Synthesis ◽  
World Coordinate System ◽  
Coordination System ◽  
Branched Chain ◽  
Branched Chains ◽  
Multi Robot

For the synthesis of the required type about the multi-robot coordination system in industrial transportation, this paper presents a novel method in which each robot in the coordinated task is viewed as a branched chain of an equivalent parallel robot (EPR), which is converted into a problem for type synthesis of parallel robots. A theoretic method is proposed to represent the kinematic features of the mechanism’s end-effector and its position and pose in the world coordinate system. The basic concept of a robotic characteristic (C) set is given, and the corresponding algorithm is analyzed. Based on the theory of C set, the concrete steps for type synthesis of EPR are presented by analyzing the characteristics of its branched chains, and many EPR groups with end kinematic features for the C sets of the operational tasks are obtained. Then three translational (3T) operational requirements that can be extended to other degrees of freedom (DOF) are adopted, and the DOF of homogeneous and heterogeneous EPR are analyzed using screw theory. Finally the validation of the method is demonstrated by Adams, which shows that the two groups are able to complete the task.

scholarly journals A Novel Three-Loop Parallel Robot With Full Mobility: Kinematics, Singularity, Workspace, and Dexterity Analysis

2017 ◽  
Vol 9 (5) ◽  
Author(s):  
Wei Li ◽  
Jorge Angeles
Keyword(s):  
High Speed ◽  
Screw Theory ◽  
Parallel Robot ◽  
Simple Expression ◽  
Parallel Robots ◽  
Forward Displacement ◽  
Design Variables ◽  
The Subject ◽  
Stewart Gough Platform ◽  
The Given

A novel parallel robot, dubbed the SDelta, is the subject of this paper. SDelta is a simpler alternative to both the well-known Stewart–Gough platform (SGP) and current three-limb, full-mobility parallel robots, as it contains fewer components and all its motors are located on the base. This reduces the inertial load on the system, making it a good candidate for high-speed operations. SDelta features a symmetric structure; its forward-displacement analysis leads to a system of three quadratic equations in three unknowns, which admits up to eight solutions, or half the number of those admitted by the SGP. The kinematic analysis, undertaken with a geometrical method based on screw theory, leads to two Jacobian matrices, whose singularity conditions are investigated. Instead of using the determinant of a 6 × 6 matrix, we derive one simple expression that characterizes the singularity condition. This approach is also applicable to a large number of parallel robots whose six actuation wrench axes intersect pairwise, such as all three-limb parallel robots whose limbs include, each, a passive spherical joint. The workspace is analyzed via a geometric method, while the dexterity analysis is conducted via discretization. Both show that the given robot has the potential to offer both large workspace and good dexterity with a proper choice of design variables.

scholarly journals Potential Energy Distribution of Redundant Cable-Driven Robot Applied to Compliant Grippers: Method and Computational Analysis

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3403 ◽  
Author(s):  
Rodriguez-Barroso ◽  
Saltaren ◽  
Portilla ◽  
Cely ◽  
Yakrangi
Keyword(s):  
Energy Distribution ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Potential Energy Distribution ◽  
End Effector ◽  
Tension Distribution ◽  
Multibody Dynamic ◽  
Compliant Actuators ◽  
Dynamic Software ◽  
The Relationship

Cable-driven parallel robots with a redundant configuration have infinite solutions for their cable tension distribution to provide a specific wrench to the end-effector. Redundancy is commonly used to increase the workspace and stiffness or to achieve secondary objectives like energetic minimization or additional movements. This article presents a method based on energy distribution to handle the redundancy of cable-driven parallel robots. This method allows the deformation and tension of each link to be related to the total energy available in the parallel robot. The study of energy distribution expression allows deformation, tension, and position to be combined. It also defines the range of tension and deformation that cables can achieve without altering the wrench exerted on the end-effector. This range is used with a passive reconfigurable end-effector to control the position of two grippers attached to some cables which act as compliant actuators. The relationship between the actuators’ energy and their corresponding gripper positions is also provided. In this way, energy measurement from the actuators allows the grasping state to be sensed. The results are validated using multibody dynamic software.

Sliding Mode Set Point Control of a Six-DOF Cable-Suspended Parallel Robot With Tension Constraints and Uncertain Disturbances

2018 ◽  
Author(s):  
Ping Ren ◽  
Yunlong Sun
Keyword(s):  
Sliding Mode ◽  
Sufficient Conditions ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Set Point ◽  
Uncertain Disturbances ◽  
Point Motion ◽  
Six Dof ◽  
Six Degree Of Freedom ◽  
The Relationship

This paper presents the design of a robust sliding mode controller for a six-degree-of-freedom cable-suspended parallel robot under uncertain disturbances. The control of cable-suspended parallel robots is quite challenging due to the unidirectional constraint of cable tensions. With the aid of interval analysis, a set of algebraic inequalities is obtained to establish the relationship between the cables’ tension constraints and the controller parameters. The sufficient conditions of the controller parameters satisfying the constraints are obtained for the set point motion within the robot’s static workspace. Numerical simulations are presented to verify the effectiveness of the proposed approach.

Optimal torque distribution method for a redundantly actuated 3-RRR parallel robot using a geometrical approach

Robotica ◽  
2012 ◽  
Vol 31 (4) ◽  
pp. 549-554 ◽  
Author(s):  
Ho-Seok Shim ◽  
TaeWon Seo ◽  
Jeh Won Lee
Keyword(s):  
Stiffness Matrix ◽  
Screw Theory ◽  
Null Space ◽  
Geometric Analysis ◽  
Parallel Robot ◽  
Geometrical Approach ◽  
Space Vector ◽  
Distribution Method ◽  
Torque Distribution ◽  
Redundantly Actuated

SUMMARYIn this paper, a novel optimal torque distribution method for a redundantly actuated parallel robot is proposed. Geometric analysis based on screw theory is performed to calculate the stiffness matrix of a redundantly actuated 3-RRR parallel robot. The analysis is performed based on statics focusing on low-speed motions. The stiffness matrix consisting of passive and active stiffness is also derived by the differentiation of Jacobian matrix. Comparing two matrices, we found that null-space vector is related to link geometry. The optimal distribution torque is determined by adapting mean value of minimum and maximum angles as direction angles of null-space vector. The resulting algorithm is validated by comparing the new method with the minimum-norm method and the weighted pseudo-inverse method for two different paths and force conditions. The proposed torque distribution algorithm shows the characteristics of minimizing the maximum torque.

Stiffness Modeling of the Soft-Finger Contact in Robotic Grasping

2004 ◽  
Vol 126 (4) ◽  
pp. 646-656 ◽  
Author(s):  
Abdul Ghafoor ◽  
Jian S. Dai ◽  
Joseph Duffy
Keyword(s):  
Stiffness Matrix ◽  
Screw Theory ◽  
Contact Stiffness ◽  
Point Contact ◽  
Elastic Model ◽  
Point Contacts ◽  
Stiffness Analysis ◽  
Stiffness Properties ◽  
Congruence Transformation ◽  
Soft Finger

This paper investigates the soft-finger contact by presenting the contact with a set of line springs based on screw theory, reveals the rotational effects, and identifies the stiffness properties of the contact. An elastic model of a soft-finger contact is proposed and a generalized contact stiffness matrix is developed by applying the congruence transformation and by introducing stiffness mapping of the line springs in translational directions and rotational axes. The effective stiffnesses along these directions and axes are hence obtained and the rotational stiffnesses are revealed. This helps create a screw representation of a six-dimensional soft-finger contact and produce an approach of analyzing and synthesizing a robotic grasp without resorting to the point contact representation. The correlation between the rotational stiffness, the number of equivalent point contacts and the number of equivalent contours is given and the stiffness synthesis is presented with both modular and direct approaches. The grasp thus achieved from the stiffness analysis contributes to both translational and rotational restraint and the stiffness matrix so developed is proven to be symmetric and positive definite. Case studies are presented with a two-soft-finger grasp and a three-soft-finger grasp. The grasps are analyzed with a general stiffness matrix which is used to control the fine displacements of a grasped object by changing the preload on the contact.

Sliding Mode Set-Point Control of a Three-DOF Cable-Suspended Parallel Robot With Uncertain Mass and Disturbances

2019 ◽  
Author(s):  
Ping Ren ◽  
Xu Sheng
Keyword(s):  
Sliding Mode ◽  
Sufficient Conditions ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Parallel Mechanisms ◽  
Set Point ◽  
Point Motion ◽  
Actuation Scheme ◽  
Three Degree Of Freedom ◽  
The Relationship

Abstract Cable-Suspended Parallel Robots (CSPRs) utilize winches and cables as the actuation scheme instead of rigid links, which renders them advantages of both parallel mechanisms and cable mechanisms. In this paper, a robust sliding mode controller was designed for a three-degree-of-freedom CSPR with uncertain end-effector mass and external disturbances. To control the motions of CSPRs is usually challenging due to the unidirectional constraints of cable tensions. Based on interval analysis, a set of analytical inequalities is obtained which establish the relationship between the cables’ tension constraints and the controller parameters. The sufficient conditions of the controller parameters satisfying the constraints are obtained for the set-point motion subject to uncertainties. Numerical simulations are presented to verify the effectiveness of the proposed approach.

scholarly journals Motion Reliability Analysis of the Delta Parallel Robot considering Mechanism Errors

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Yu Li ◽  
Deyong Shang ◽  
Xun Fan ◽  
Yue Liu
Keyword(s):  
Reliability Analysis ◽  
Structural Parameters ◽  
Kinematic Model ◽  
Vertical Direction ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Joint Clearance ◽  
Spherical Joint ◽  
Key Factor ◽  
The Relationship

Delta parallel robots are widely used in assembly detection, packaging sorting, precision positioning, and other fields. With the widespread use of robots, people have increasing requirements for motion accuracy and reliability. This paper considers the influence of various mechanism errors on the motion accuracy and analyzes the motion reliability of the mechanism. Firstly, we establish a kinematic model of the robot and obtain the relationship between the position of the end effector and the structural parameters based on the improved D–H transform rule. Secondly, an error model considering the dimension error, the error of revolute joint clearance, driving error, and the error of spherical joint clearance is established. Finally, taking an actual robot as an example, the comprehensive influence of mechanism errors on motion accuracy and reliability in different directions is quantitatively analyzed. It is shown that the driving error is a key factor determining the motion accuracy and reliability. The influence of mechanism errors on motion reliability is different in different directions. The influence of mechanism errors on reliability is small in the vertical direction, while it is great in the horizontal direction. Therefore, we should strictly control the mechanism errors, especially the driving angle, to ensure the motion accuracy and reliability. This research has significance for error compensation, motion reliability analysis, and reliability prediction in robots, and the conclusions can be extended to similar mechanisms.

Configuration Design and Kinematic Analysis on Some New 2R1T 3-DOF Parallel Robots

2011 ◽  
Vol 474-476 ◽  
pp. 840-845
Author(s):  
Da Chang Zhu ◽  
Fan Xiao ◽  
Liang Wang ◽  
Qi Hua Gu
Keyword(s):  
Dynamic Simulation ◽  
Kinematic Analysis ◽  
Screw Theory ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Configuration Design ◽  
Structural Synthesis ◽  
Systematic Method

Based on the screw theory,the paper presents a systematic method for structural synthesis of the two rotations and one translation parallel robot.According to the reciprocal product between kinetic screw and constrainted screw in screw theory.This method firstly creats possible branch structures and then generates diferent models of mechanism.By this method,the paper carries on the structural synthesis of the two rotations and one translation parallel robot,and also lists some of the mechanisms including a few new ones. Analyzsis solution of direct and inverse position.The dynamic simulation was conducted using the software of Adams.

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