Full Rotatability and Singularity of Six-Bar and Geared Five-Bar Linkages

2010 ◽  
Vol 2 (1) ◽  
Author(s):  
Kwun-Lon Ting ◽  
Jun Wang ◽  
Changyu Xue ◽  
Kenneth R. Currie
Keyword(s):  
Linkage Analysis ◽  
Comprehensive Treatment ◽  
Not Given ◽  
Joint Rotation ◽  
Difficult Condition ◽  
Continuous Rotation ◽  
Center Position ◽  
Analysis And Synthesis

Full rotatability identification is a problem frequently encountered in linkage analysis and synthesis. The full rotatability of a linkage refers to a linkage, in which the input may complete a continuous rotation without the possibility of encountering a dead center position. In a complex linkage, the input rotatability of each branch may be different. This paper presents a unified and comprehensive treatment for the full rotatability identification of six-bar and geared five-bar linkages, regardless of the choice of input joints or reference link. A general way to identify all dead center positions and the associated branches is discussed. Special attention and detail discussion is given to the more difficult condition, in which the input is not given through a joint in the four-bar loop or to a gear link. A branch without a dead center position has full rotatability. Using the concept of joint rotation space, the branch of each dead center position, and hence, the branch without a dead center position can be identified. One may find the proposed method to be generally and conceptually straightforward. The treatment covers all linkage inversions.

Full Rotatability of Stephenson Six-Bar and Geared Five-Bar Linkages

2008 ◽  
Author(s):  
Kwun-Lon Ting ◽  
Jun Wang ◽  
Changyu Xue ◽  
Kenneth R. Currie
Keyword(s):  
Linkage Analysis ◽  
Degree Of Freedom ◽  
Comprehensive Treatment ◽  
Joint Rotation ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Input And Output ◽  
Difficult Condition ◽  
Center Position ◽  
Analysis And Synthesis

Full rotatability identification is a problem frequently encountered in linkage analysis and synthesis. The full rotatability of a linkage is referred to a linkage in which the input may complete a full revolution without the possibility of encountering a dead center position. In a complex linkage, the input rotatability of each branch may be different. This paper presented a unified and comprehensive treatment for the full rotatability identification of six-bar and geared five-bar linkages disregard the choice of input and output joints or fixed link. A simple way to identify all dead center positions and the associated branches is discussed. Special attention and detail discussion is given to the more difficult condition with the input given through a link or joint not in the four-bar loop or on a gear-link. A branch without a dead center position has full rotatability. Using the concept of joint rotation space, the branch of each dead center position, and hence the branch without a dead center position can be identified easily. The proposed method is simple and conceptually straightforward and the process can be automated easily. It can be extended to any other single-degree-of-freedom complex linkages.

Full Rotatability of Watt Six-Bar Linkages

2014 ◽  
Author(s):  
Jun Wang ◽  
Kwun-Lon Ting ◽  
Daxing Zhao ◽  
Quan Wang ◽  
Jinfeng Sun ◽  
...  
Keyword(s):  
Linkage Analysis ◽  
Range Of Motion ◽  
Analytical Method ◽  
Joint Rotation ◽  
Center Position ◽  
Analysis And Synthesis ◽  
Prismatic Joints

The full rotatability of a linkage refers to a linkage in which the input may complete a continuous and smooth rotation without the possibility of encountering a dead center position. Full rotatability identification is a problem generally encountered among the mobility problems that may include branch (assembly mode or circuit), sub-branch (singularity-free) identification, range of motion, and order of motion in linkage analysis and synthesis. In a complex linkage, the input rotatability of each branch may be different while the Watt six-bar linkages may be special. This paper presents a unified and analytical method for the full rotatability identification of Watt six-bar linkages regardless of the choice of input joints or reference link or joint type. The branch of a Watt without dead center positions has full rotatability. Using discriminant method and the concept of joint rotation space (JRS), the full rotatability of a Watt linkage can be easily identified. The proposed method is general and conceptually straightforward. It can be applied for all linkage inversions. Examples of Watt linkage and a six-bar linkage with prismatic joints are employed to illustrate the proposed method.

Mobility Identification of a Group of Single Degree-of-Freedom Eight-Bar Linkages

2010 ◽  
Author(s):  
Jun Wang ◽  
Kwun-Lon Ting
Keyword(s):  
Linkage Analysis ◽  
Range Of Motion ◽  
Configuration Space ◽  
Mobility Analysis ◽  
Joint Rotation ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Computer Aided ◽  
Analysis And Synthesis ◽  
First Time

This paper presents the first complete and automated mobility identification method for a group of single-DOF planar eight-bar linkages and thus represents a breakthrough on the recognition and understanding of complex linkage mobility. The mobility identification in this paper refers to the configuration space, the range of motion, and configuration recognition. It is a troublesome problem encountered in any linkage analysis and synthesis. The problem becomes extremely confusing with complex multiloop linkages. The proposed approach is simple and straightforward. It recognizes that the loop equations are the mathematical fundamentals for the formation of branches, sub-branches, and other mobility issues of the entire linkage. The mobility information is then extracted through the discriminant method. The paper presents complete answers to all typical mobility issues, offers the mathematical insight as well as explanation on the effects of multiple loops via joint rotation space, and casts light for treating the mobility problems of other complex linkages. The merits of the discriminant method for mobility identification are clarified and examples are employed to showcase the proposed method. The computer-aided automated mobility analysis of eight-bar linkages is made possible for the first time.

The Spatial Linkage Analysis and Synthesis of the Vector Fitting Method

2012 ◽  
Vol 268-270 ◽  
pp. 1231-1238
Author(s):  
You Liang Xu
Keyword(s):  
Linkage Analysis ◽  
Unit Vector ◽  
New Method ◽  
Analysis And Design ◽  
Vector Fitting ◽  
The Core ◽  
Design Variables ◽  
Fitting Method ◽  
Analysis And Synthesis ◽  
Core Idea

Put forward a new method of spatial linkage analysis and synthesis of the vector fitting. The core idea is: all components available in mechanisms can be represent by one or one group of vectors, all vectors are transformed from unit vector, and the mechanism is a assemblage of those vectors. Because of kinematic variables (position, direction, changing when moving ) and design variables (shape, size, unchanging when moving ) is been properly separated which can improve the efficiency of analysis and calculation. The example shows that the method is efficient, and can be used both in the analysis and design of the mechanism.

General Mobility Identification and Rectification of Watt Six-Bar Linkages

2007 ◽  
Author(s):  
Kwun-Lon Ting ◽  
Changyu Xue ◽  
Jun Wang ◽  
Kenneth R. Currie
Keyword(s):  
Linkage Analysis ◽  
Mobility Analysis ◽  
Computer Aided ◽  
Analysis And Synthesis ◽  
General Mobility

Mobility identification is a common problem encountered in linkage analysis and synthesis. Mobility of linkages refers to the problems concerning branch defect, full rotatability, singularities, and order of motion. By introducing the concept of stretch rotation, the paper shows the existence of a hidden five-bar loop in a Watt six-bar linkage and how it affects the formation of branches, sub-branches, as well as the whole mobility of the entire linkage. The paper presents the first methodology for a fully automated computer-aided complete mobility analysis of Watt six-bar linkages.

Singularity and Sub-Branch Identification of Two-DOF Seven-Bar Parallel Manipulators

2009 ◽  
Author(s):  
Jun Wang ◽  
Kwun-Lon Ting ◽  
Changyu Xue ◽  
Kenneth R. Currie
Keyword(s):  
Parallel Manipulators ◽  
Singularity Analysis ◽  
Simple Explanation ◽  
Mobility Analysis ◽  
Joint Rotation ◽  
Computer Aided ◽  
Center Position ◽  
Planar Linkages ◽  
General Method ◽  
Unified Method

Mobility analysis of multi-DOF multiloop planar linkages is much more complicated than the single-DOF planar linkages and has been little explored. This paper offers a unified method to treat the singularity (dead center position) and sub-branch identification of the planar two-DOF seven-bar linkages regardless of the choice of the inputs or fixed links. This method can be extended for the singularity analysis of other multi-DOF multiloop linkages. Based on the concept of joint rotation space and N-bar rotatability laws, this paper presents a general method for the sub-branch identification of the seven-bar linkages. It offers simple explanation and geometric insights for the formation of branch, singularity and sub-branch of the two-DOF seven-bar linkages. The presented algorithm for sub-branch identification is suitable for automated computer-aided mobility identification. Examples are employed to demonstrate the proposed method.

Patient Involvement in Treatment Decision Making Can Help or Hinder Placebo Analgesia

2014 ◽  
Vol 222 (3) ◽  
pp. 165-170 ◽  
Author(s):  
Andrew L. Geers ◽  
Jason P. Rose ◽  
Stephanie L. Fowler ◽  
Jill A. Brown
Keyword(s):  
Patient Involvement ◽  
Cold Water ◽  
Prior Experience ◽  
Water Immersion ◽  
Treatment Decision ◽  
Cold Water Immersion ◽  
Not Given ◽  
Placebo Analgesia ◽  
Treatment Decision Making ◽  
Immersion Experience

Experiments have found that choosing between placebo analgesics can reduce pain more than being assigned a placebo analgesic. Because earlier research has shown prior experience moderates choice effects in other contexts, we tested whether prior experience with a pain stimulus moderates this placebo-choice association. Before a cold water pain task, participants were either told that an inert cream would reduce their pain or they were not told this information. Additionally, participants chose between one of two inert creams for the task or they were not given choice. Importantly, we also measured prior experience with cold water immersion. Individuals with prior cold water immersion experience tended to display greater placebo analgesia when given choice, whereas participants without this experience tended to display greater placebo analgesia without choice. Prior stimulus experience appears to moderate the effect of choice on placebo analgesia.

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