Screw rolling between moving and fixed axodes traced by lower-mobility parallel mechanism

2021 ◽  
Vol 163 ◽  
pp. 104354
Author(s):  
Leilei Zhang ◽  
Yanzhi Zhao ◽  
Jiankun Ren
Keyword(s):  
Parallel Mechanism ◽  
Screw Rolling ◽  
Lower Mobility

Acceleration and Dexterity Performance Indices for 6-DOF and Lower-Mobility Parallel Mechanism

2004 ◽  
Author(s):  
X. J. Guo ◽  
F. Q. Chang ◽  
S. J. Zhu
Keyword(s):  
Parallel Mechanism ◽  
Robot Manipulator ◽  
Coefficient Matrix ◽  
Second Order ◽  
Influence Coefficient ◽  
Global Index ◽  
Performance Indices ◽  
First Order ◽  
Lower Mobility

On the basis of first-order and second-order kinematic influence coefficient matrices, dynamics characteristics indices for robot manipulator are presented in the paper. Different from indices before, these indices include not only the first-order kinematics influence coefficient matrix G, but also the second-order kinematic influence coefficient matrix H. Then with the global index, these indices can be used to guide the dynamics design.

Analysis and Design of Lower-Mobility Parallel Mechanism of Non-Symmetrical Based on Variable Topology Theory

2011 ◽  
Vol 201-203 ◽  
pp. 1907-1912
Author(s):  
Rong Jiang Cui ◽  
Zong He Guo ◽  
Zi Xun Yin ◽  
Song Song Zhu
Keyword(s):  
Parallel Mechanism ◽  
Screw Theory ◽  
Parallel Mechanisms ◽  
Basic Variable ◽  
Analysis And Design ◽  
And Topology ◽  
Variable Topology ◽  
Lower Mobility ◽  
Branched Chain ◽  
Mechanism Theory

First, the branched-chain of parallel mechanism was Classified according to reciprocal screw theory. Then, the introduction of variable topology mechanism theory, with the characteristics of parallel mechanisms themselves, the definition and basic variable topology means of variable topology parallel mechanism were given. With evolutionary theory, the method to design lower-mobility parallel mechanisms of non-asymmetric was proposed based on variable topology mechanism theory .Taking 3-RPS as ideal mechanism and topology synthesis was carried out, besides 2-RPS mechanism were analyzed. The introduction of variable topology mechanism theory provided a theoretical basis and innovative approaches for the synthesis configuration of Lower-mobility parallel mechanisms of non-asymmetric.

scholarly journals Mobility analysis of a robotic cardiopulmonary resuscitation device

2021 ◽  
Author(s):  
Mahdi Ardestani ◽  
Mohsen Asgari
Keyword(s):  
Parallel Mechanism ◽  
Jacobian Matrix ◽  
Closed Form Solution ◽  
Parallel Manipulators ◽  
Optimization Method ◽  
Form Solution ◽  
Mobility Analysis ◽  
Chest Compressions ◽  
Singularity Problem ◽  
Lower Mobility

Abstract During chest compressions action, in CPR (CPR), the 2 arms of the rescuer constitute a parallel mechanism. Inspired by this performance, during this study a specific family of lower mobility parallel manipulators by employing a modified version of Delta robot is proposed for chest compressions in rescuing a patient. One of the biggest differences between this mechanism and the Delta parallel mechanism is that the position of the three active connections of the robot relative to each other has changed the geometry of the platforms. Also, it shapes the asymmetrical structure within the robot mechanism and its workspace. Another difference is due to the architectural optimization method considering the mixed performance index, which has been used during this mechanism to achieve a much better compromise between the manipulator dexterity and its workspace. Within the present paper, after introducing the architecture of the robot, a closed-form solution is developed for the kinematic problem and therefore the results are verified using MSC. Adams©. Then Jacobian matrix is generated to gauge the singularity problem of the proposed mechanism. then, the workspace of the robot is investigated and compared with the original Delta mechanism.

Motion/Force Transmission Analysis of Parallel Mechanisms With Planar Closed-Loop Subchains

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Kristan Marlow ◽  
Mats Isaksson ◽  
Jian S. Dai ◽  
Saeid Nahavandi
Keyword(s):  
Performance Measures ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Closed Loop ◽  
Screw Theory ◽  
Parallel Mechanisms ◽  
Force Transmission ◽  
Six Degrees Of Freedom ◽  
Lower Mobility ◽  
Transmission Ability

Singularities are one of the most important issues affecting the performance of parallel mechanisms. A parallel mechanism with less than six degrees of freedom (6DOF) is classed as having lower mobility. In addition to input–output singularities, such mechanisms potentially suffer from singularities among their constraints. Furthermore, the utilization of closed-loop subchains (CLSCs) may introduce additional singularities, which can strongly affect the motion/force transmission ability of the entire mechanism. In this paper, we propose a technique for the analysis of singularities occurring within planar CLSCs, along with a finite, dimensionless, frame invariant index, based on screw theory, for examining the closeness to these singularities. The integration of the proposed index with existing performance measures is discussed in detail and exemplified on a prototype industrial parallel mechanism.

A method for force analysis of the overconstrained lower mobility parallel mechanism

2015 ◽  
Vol 88 ◽  
pp. 31-48 ◽  
Author(s):  
Yundou Xu ◽  
Wenlan Liu ◽  
Jiantao Yao ◽  
Yongsheng Zhao
Keyword(s):  
Parallel Mechanism ◽  
Force Analysis ◽  
Lower Mobility

Coupling 3-PSR/PSU 5-axis compensation mechanism for stabilized platform and its analysis

2012 ◽  
Vol 227 (7) ◽  
pp. 1619-1629 ◽  
Author(s):  
Xiao Liu ◽  
Tieshi Zhao ◽  
Erjuan Luo ◽  
Weiwei Chen ◽  
Qiuyue Pan
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Ship Motions ◽  
Equivalent Transformation ◽  
Coupling Force ◽  
Coupling Dynamics ◽  
Lower Mobility ◽  
Coupling Characteristics ◽  
Stabilized Platform

This article presents a coupling 3-PSR/PSU parallel mechanism for ship-based stabilized platform based on the coupling characteristics of the ship motions. With coupling characteristics, the goal of 3-axis drives and 5-axis compensation of the moving platform is achieved. From the screw theory, degrees-of-freedom and coupling kinematic characteristics of the mechanism are analyzed. A method for equivalent transformation of motion parameters is proposed. This presents a mapping relationship between the independent degrees-of-freedom and the coupling degrees-of-freedom. The investigations are further extended to the coupling dynamics characteristics of the mechanism. In particular, the effects produced by the coupling force/torque to the system are analyzed. Hence, taking minimum system driving force as the optimization goal, the coupling dynamic equation of the parallel mechanism is established. The numerical example reveals that this coupling parallel mechanism can be applied to the multi-axis compensation of ship-based stabilized platform. The study also enriches the application area of lower-mobility parallel mechanism.

A Systematic Approach for Accuracy Design of Lower-Mobility Parallel Mechanism

Robotica ◽  
2020 ◽  
Vol 38 (12) ◽  
pp. 2173-2188
Author(s):  
Wenjie Tian ◽  
Ziqian Shen ◽  
Dongpo Lv ◽  
Fuwen Yin
Keyword(s):  
Parallel Mechanism ◽  
Screw Theory ◽  
Geometric Error ◽  
Error Modeling ◽  
Tolerance Allocation ◽  
Design Stage ◽  
Geometric Errors ◽  
End Effector ◽  
Allocation Method ◽  
Lower Mobility

SUMMARYGeometric accuracy is a critical performance factor for parallel robots, and regardless of error compensation, accuracy design or tolerance allocation is another way to ensure the pose accuracy of a robot at design stage. A general method of both geometric error modeling and accuracy design of lower-mobility parallel mechanisms is presented. First, a general approach for error modeling of lower-mobility parallel mechanism is proposed based on screw theory, and then the geometric errors affecting the compensatable and uncompensatable accuracy of the end-effector are separated using the properties of dual vector space. The pose error aroused by compensatable geometric errors can be compensated via kinematic calibration, while the uncompensatable geometric errors should be minimized during the manufacturing and assembly processes. Based on that, the tolerance allocation method is presented, giving each uncompensatable geometric error a proper tolerance by the use of reliability theory. Compared with the traditional tolerance allocation method, the advantages of the proposed method are as follows: the number of geometric errors to be allocated is greatly reduced; the results of serialized tolerance allocation can be obtained according to different reliability indices of pose accuracy of end-effector for designers to choose; on the premise of guaranteeing the same pose accuracy of end-effector, the allocated tolerances are loose and easy to realize. Finally, the proposed methods are successfully applied to an R(2-RPS&RP)&UPS lower-mobility parallel robot, and the effectiveness and practicability of the proposed method are verified.

Transmission Index of Lower-Mobility Parallel Mechanism: Case Study on 3-PRS Mechanism

2017 ◽  
Author(s):  
Yukio Takeda ◽  
Xinghai Liang
Keyword(s):  
Parallel Mechanism ◽  
Kinematic Model ◽  
Parallel Mechanisms ◽  
Pressure Angle ◽  
Transmission Index ◽  
New Ideas ◽  
Lower Mobility ◽  
Definition Of ◽  
Actuated Joints

An extended definition of the transmission index based on the pressure angle was proposed. In order to enable evaluation of motion/force transmissibility and constrainability of parallel mechanism including lower-mobility/hybrid parallel mechanisms, pressure angle of a kinematic structure obtained by blocking all the actuated joints of the original mechanism was defined. In addition to this, an equivalent kinematic model of the original mechanism was introduced, in which the output link is supported by pure forces with the directions determined by the kinematic configuration of the mechanism. With these new ideas, a novel transmission index was proposed, and an illustrative example of 3-PRS mechanism was shown.

scholarly journals Kinematic performance evaluation of 2-degree-of-freedom parallel mechanism applied in multilayer garage

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879171
Author(s):  
Tianhua He ◽  
Junpeng Shao ◽  
Yongde Zhang ◽  
Jingang Jiang
Keyword(s):  
Parallel Mechanism ◽  
Evaluation Method ◽  
Degree Of Freedom ◽  
Evaluation Index ◽  
Global Symmetry ◽  
Symmetric Structure ◽  
Lower Mobility ◽  
Translational Degree ◽  
Kinematic Performance ◽  
Simulation Results

In this article, our recent work on a kind of 2-degree-of-freedom lower-mobility parallel mechanism, which has one rotation degree of freedom and one translational degree of freedom, used in multilayer garage is presented. It has the following characteristics: lower-mobility, non-symmetric structure but can realize symmetric movement and a good compatibility for different kinds of lifting work. Kinematic performance should be considered in the first of designing a new kind of mechanism, the optimal kinematic design and analysis of this lower-mobility parallel mechanism are primarily investigated. In process of study, the global conditioning index over workspace is adopted, we establish a new evaluation method for the lower-mobility parallel mechanism, called global symmetry index and simulation results are shown. In addition, the flexible workspace of this lower-mobility parallel mechanism is also proposed. The evaluation index can be also applied on other lower-mobility parallel mechanism, which needs steady and symmetric movement.

Sign in / Sign up

Export Citation Format

Share Document