Transmission index of a class of parallel manipulators with 3-RS(SR) primary structures based on pressure angle and equivalent mechanism with 2-SS chains replacing RS chain

2019 ◽  
Vol 139 ◽  
pp. 359-378 ◽  
Author(s):  
Xinghai Liang ◽  
Yukio Takeda
Keyword(s):  
Parallel Manipulators ◽  
Pressure Angle ◽  
Transmission Index ◽  
Primary Structures ◽  
Equivalent Mechanism

New Indices for Optimal Design of Redundantly Actuated Parallel Manipulators

2016 ◽  
Vol 9 (1) ◽  
Author(s):  
Qinchuan Li ◽  
Ningbin Zhang ◽  
Feibo Wang
Keyword(s):  
Optimal Design ◽  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Mean Value ◽  
Transmission Performance ◽  
Transmission Index ◽  
Redundantly Actuated ◽  
Lower Mobility ◽  
Six Dof ◽  
Force Transmissibility

Redundantly actuated parallel manipulators (PMs) receive growing interest due to their reduced singularity and enlarged workspace. This paper proposes new indices for optimal design and analysis of redundantly actuated PMs by evaluating their motion/force transmissibility. First, we proposed a method to extract a multi-DOF (degrees-of-freedom) redundantly actuated PM into several subsidiary one-DOF PMs with two or more actuators by locking some actuators in an ergodic manner. Then, a new index of output transmission performance is proposed by investigating the mean value of the instantaneous power produced by the multiple actuation wrenches and one twist of the moving platform of one-DOF PMs. A local transmission index (LTI) is defined as the minimum value of the index of output and input transmission performance. A global transmission index (GTI) is then established based on the LTI. The proposed LTI and GTI are coordinate-free and have clear physical interpretation. Finally, the validity and universality of the new indices are demonstrated by optimization and analysis of redundantly actuated lower-mobility PMs with extra articulated six-DOF or limited-DOF limbs.

Evaluation of Force/Torque Transmission Quality for Parallel Manipulators

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Xiang Chen ◽  
Chao Chen ◽  
Xin-Jun Liu
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Analysis And Design ◽  
Torque Transmission ◽  
Transmission Index ◽  
Internal Forces ◽  
Transmission Quality ◽  
End Effectors ◽  
External Loads

Performance evaluation is one of the most important issues in the analysis and design of parallel manipulators. The internal forces and torques in parallel manipulators contribute to manipulating the end-effectors and resisting the external loads. In this work, we propose a transmission index to evaluate the force and torque transmission quality of parallel manipulators. The index is normalized and used to analyze the exactly constrained parallel manipulators, based on the transmission matrix spanned by transmission wrench screws (TWSs). Furthermore, the index is applied to parallel manipulators with different degrees of freedom (DOF) in order to illustrate and validate the proposed approach and index. Finally, a typical parallel manipulator is selected to address the comparison analysis between different indices, which demonstrates that the proposed index, possessing respective merits, could be complementary to other existing indices.

Determination of the closed-form workspace area expression and dimensional optimization of planar parallel manipulators

Robotica ◽  
2016 ◽  
Vol 35 (10) ◽  
pp. 2056-2075 ◽  
Author(s):  
M. Ganesh ◽  
Banke Bihari ◽  
Vijay Singh Rathore ◽  
Dhiraj Kumar ◽  
Chandan Kumar ◽  
...  
Keyword(s):  
Closed Form ◽  
Degrees Of Freedom ◽  
Solution Space ◽  
Optimization Procedure ◽  
Parallel Manipulators ◽  
Force Transmission ◽  
Workspace Analysis ◽  
Planar Parallel Manipulator ◽  
Transmission Index ◽  
Planar Parallel Manipulators

SUMMARYOptimization is an important step in the design and development of a planar parallel manipulator. For optimization processes, workspace analysis is a crucial and preliminary objective. Generally, the workspace analysis for such manipulators is carried out using a non-dimensional approach. For planar parallel manipulators of two degrees of freedom (2-DOF), a non-dimensional workspace analysis is very advantageous. However, it becomes very difficult in the case of 3-DOF and higher DOF manipulators because of the complex shape of the workspace. In this study, the workspace shape is classified as a function of the geometric parameters, and the closed-form area expressions are derived for a constant orientation workspace of a three revolute–revolute–revolute (3-RRR) planar manipulator. The approach is also shown to be feasible for different orientations of a mobile platform. An optimization procedure for the design of planar 3-RRR manipulators is proposed for a prescribed workspace area. It is observed that the closed-form area expression for all the possible shapes of the workspace provides a larger solution space, which is further optimized considering singularity, mass of the manipulator, and a force transmission index.

FORCE-AND-MOTION-TRANSMISSION EVALUATION IN SPATIAL MECHANISMS

2005 ◽  
Vol 29 (4) ◽  
pp. 527-539
Author(s):  
Chao Chen ◽  
Jorge Angeles
Keyword(s):  
Force Transmission ◽  
Pressure Angle ◽  
Spatial Mechanisms ◽  
Force And Motion ◽  
Transmission Index ◽  
Transmission Quality ◽  
Special Case

We propose a generalized transmission index for spatial mechanisms, based on the virtual coefficient between the transmission wrench screw and the output twist screw. Compared with other indices, ours is well defined in any case and able to evaluate the force transmission quality more precisely. We apply this index to mechanisms with higher pairs and show that the pressure angle is a special case of our index.

Kinematics and Workspace Analyses of 3/3-RRRS Parallel Manipulator

2012 ◽  
Vol 155-156 ◽  
pp. 1090-1095 ◽  
Author(s):  
Meng Si Liu ◽  
Yi Cao ◽  
Qiu Ju Zhang ◽  
Clément Gosselin ◽  
Jian Chun Sun ◽  
...  
Keyword(s):  
Parallel Manipulator ◽  
Three Dimensional ◽  
Parallel Manipulators ◽  
Geometrical Method ◽  
Three Dimensional Model ◽  
Forward Displacement ◽  
Theoretical Results ◽  
Orientation Workspace ◽  
Forward Displacement Analysis ◽  
Equivalent Mechanism

It is known that two primary disadvantages of parallel manipulators are the complicated forward kinematics and limited workspace. This paper mainly addressed the kinematics and workspace analyses of a 3/3-RRRS 6-DOF parallel manipulator. After a brief introduction of the 3/3 -RRRS 6-DOF parallel manipulator, a three-dimensional model and its relevant structure diagram are constituted, the forward and inverse displacement analyses of the 3/3-RRRS parallel manipulator are discussed in detail, especially, a novel geometrical method referred as equivalent mechanism is proposed for the forward displacement analysis of the manipulator under consideration. Based on the displacement analyses of the manipulator, a discretization method is proposed for the computation of the reachable position/orientation workspace of the 3/3-RRRS parallel manipulator, respectively. Examples of a 3/3-RRRS parallel manipulator are given to demonstrate these theoretical results.

Extension of Motion/Force Transmission Index to Parallel Manipulators With Double Platforms: Case Study on the Par4 Manipulator

2018 ◽  
Author(s):  
Qizhi Meng ◽  
Fugui Xie ◽  
Xin-Jun Liu ◽  
Yukio Takeda
Keyword(s):  
Parallel Manipulators ◽  
Parallel Mechanisms ◽  
Force Transmission ◽  
Traditional Concept ◽  
Extended Approach ◽  
Transmission Index ◽  
Kinematic Performance ◽  
Definition Of ◽  
Unified Index

At present, the research of motion/force characteristics is concentrated on the single-platform parallel mechanisms (PMs). On the contrary, relatively little attention has been paid to the double-platform PMs, and there is also no unified index. What actually causes this? One of the reasons is that the complex and inaccessible wrench system of this manipulator with the double platforms. Especially the transmission wrench screws (TWSs) are no longer like its traditional concept, i.e., linear forces along the symmetric axis of the passive arms. Essentially, the TWSs in the double-platform PMs should be applied to the end effector but not to the sub-platforms from active arms. With this new idea, the concept equivalent transmission wrench screw (ETWS) of PMs with double platforms is firstly proposed and its identification process is also provided. Then, the motion/force transmission index which considers the input transmission index (ITI) and output transmission index (OTI) is extended to the area of kinematic performance evaluation of the double-platform PMs. Finally, the validity of the proposed extension is verified by the transmission index (TI) based on the concept of pressure angle. In this paper, the typical Par4 mechanism is investigated as an example. This extended approach with a new definition of the ETWS which covers the concept of the TWS in traditional mechanism actually provides a uniform kinematic performance index of both single- and double-platforms PMs.

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 Position-Singularity Analysis of a Class of the 3/6-Gough-Stewart Manipulators Based on Singularity-Equivalent-Mechanism

10.5772/45664 ◽  
2012 ◽  
Vol 9 (1) ◽  
pp. 9 ◽  
Author(s):  
Hui Zhou ◽  
Yi Cao ◽  
Baokun Li ◽  
Meiping Wu ◽  
Jinghu Yu ◽  
...  
Keyword(s):  
Screw Theory ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Parallel Manipulators ◽  
Singularity Analysis ◽  
Polynomial Expression ◽  
Moving Platform ◽  
Singularity Locus ◽  
Three Dimensional Space ◽  
Equivalent Mechanism

This paper addresses the problem of identifying the property of the singularity loci of a class of 3/6-Gough-Stewart manipulators for general orientations in which the moving platform is an equilateral triangle and the base is a semiregular hexagon. After constructing the Jacobian matrix of this class of 3/6-Gough-Stewart manipulators according to the screw theory, a cubic polynomial expression in the moving platform position parameters that represents the position-singularity locus of the manipulator in a three-dimensional space is derived. Graphical representations of the position-singularity locus for different orientations are given so as to demonstrate the results. Based on the singularity kinematics principle, a novel method referred to as ‘singularity-equivalent-mechanism' is proposed, by which the complicated singularity analysis of the parallel manipulator is transformed into a simpler direct position analysis of the planar singularity-equivalent-mechanism. The property of the position-singularity locus of this class of parallel manipulators for general orientations in the principal-section, where the moving platform lies, is identified. It shows that the position-singularity loci of this class of 3/6-Gough-Stewart manipulators for general orientations in parallel principal-sections are all quadratic expressions, including a parabola, four pairs of intersecting lines and infinite hyperbolas. Finally, the properties of the position-singularity loci of this class of 3/6-Gough-Stewart parallel manipulators in a three-dimensional space for all orientations are presented.

scholarly journals Optimization design using a global and comprehensive performance index and angular constraints in a type of parallel manipulator

2018 ◽  
Vol 10 (7) ◽  
pp. 168781401878706 ◽  
Author(s):  
Jiangping Mei ◽  
Xu Zhang ◽  
Jiawei Zang ◽  
Fan Zhang
Keyword(s):  
Performance Index ◽  
Parallel Manipulator ◽  
Optimization Design ◽  
Dynamic Performance ◽  
Mutual Effect ◽  
Parallel Manipulators ◽  
Pressure Angle ◽  
Global Dynamic ◽  
Comprehensive Performance ◽  
Kinematic Optimization

The kinematic optimization of a type of parallel manipulator is addressed. Based on the kinematic analysis, the pressure angles within a limb and among the limbs are introduced, which have definite physical and geometrical meanings. In particular, a type of new pressure angle among the limbs (referred to as the second type of pressure angle among the limbs) is defined and considered to be one of the pressure angle constraints to ensure the kinematic performance. In the kinematic optimization phase, a global and comprehensive performance index, which combines the conditioning number of Jacobian matrix and pressure angles with the volume of workspace, is formulated as an objective function for minimization. One optimal kinematic design example that determines the dimensional parameters is provided to clarify the availability of the proposed approach. The analytical results indicate that good kinematic and dynamic performance can be guaranteed with the suggested design approach. Furthermore, the mutual effect between the dexterity and new pressure angle is analyzed. The effects of the pressure angle constraints on the minimum and maximum conditioning numbers and global dynamic performance indices through the entire workspace are discussed. The proposed research provides a method for the kinematic optimization design of parallel manipulators.

scholarly journals Transmission Index Research of Parallel Manipulators Based on Matrix Orthogonal Degree

2017 ◽  
Vol 30 (6) ◽  
pp. 1396-1405 ◽  
Author(s):  
Zhu-Feng Shao ◽  
Jiao Mo ◽  
Xiao-Qiang Tang ◽  
Li-Ping Wang
Keyword(s):  
Parallel Manipulators ◽  
Transmission Index
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