scholarly journals Type Synthesis Principle and Practice of Flexure Systems in the Framework of Screw Theory: Part I—General Methodology

2010 ◽  
Author(s):  
J. J. Yu ◽  
S. Z. Li ◽  
X. Pei ◽  
Hai-jun Su ◽  
J. B. Hopkins ◽  
...  
Keyword(s):  
System Theory ◽  
Conceptual Design ◽  
Building Block ◽  
High Performance ◽  
Screw Theory ◽  
Physical Entity ◽  
Type Synthesis ◽  
General Methodology ◽  
Synthesis Procedure ◽  
Systematic Formulation

The systematic methodologies involved in type synthesis of flexure systems are no doubt helpful to generate one and more high-performance precision machine designs at the stage of conceptual design with a rapid and effective way. This paper provides a systematic formulation of the type synthesis of parallel, serial, and hybrid flexure systems via a mapping from a geometric concept to physical entity. The whole type synthesis principle is built upon screw system theory and the geometric Freedom and Constraint Topology (FACT) approach, also combining with other concepts and methods including equivalent compliance mapping, building block etc, which enables the type synthesis of flexure systems deterministic, simple and practical. After that, Type synthesis procedure for various flexure systems are elaborated with examples. As a result, as many specified-DOF (Degree of Freedom) flexure systems as possible can be found and therefore pave the way for obtaining an optimal configuration.

scholarly journals A Screw Theory Approach for the Type Synthesis of Compliant Mechanisms With Flexures

2009 ◽  
Author(s):  
Hai-Jun Su ◽  
Denis V. Dorozhkin ◽  
Judy M. Vance
Keyword(s):  
Compliant Mechanisms ◽  
Screw Theory ◽  
Compliant Mechanism ◽  
Computational Techniques ◽  
Theory Approach ◽  
Type Synthesis ◽  
Precision Engineering ◽  
Pattern Design ◽  
Design Constraint ◽  
Systematic Formulation

This paper presents a screw theory based approach for the type synthesis of compliant mechanisms with flexures. We provide a systematic formulation of the constraint-based approach which has been mainly developed by precision engineering experts in designing precision machines. The two fundamental concepts in the constraint-based approach, constraint and freedom, can be represented mathematically by a wrench and a twist in screw theory. For example, an ideal wire flexure applies a translational constraint which can be described a wrench of pure force. As a result, the design rules of the constraint-based approach can be systematically formulated in the format of screws and screw systems. Two major problems in compliant mechanism design, constraint pattern analysis and constraint pattern design are discussed with examples in details. This innovative method paves the way for introducing computational techniques into the constraint-based approach for the synthesis and analysis of compliant mechanisms.

scholarly journals Type Synthesis Principle and Practice of Flexure Systems in the Framework of Screw Theory: Part II—Numerations and Synthesis of Complex Flexible Joints

2010 ◽  
Author(s):  
J. J. Yu ◽  
X. Pei ◽  
S. Z. Li ◽  
Hai-jun Su ◽  
J. B. Hopkins ◽  
...  
Keyword(s):  
High Performance ◽  
Screw Theory ◽  
Companion Paper ◽  
Synthesis Process ◽  
Type Synthesis ◽  
Flexible Joints ◽  
Flexible Joint ◽  
Modeling And Analysis ◽  
Revolute Joints ◽  
Application Requirements

In recent years, the increasing of application requirements call for development of a variety of high-performance (e.g. large-displacement, high-precision) flexible joints. In this paper we demonstrate how to use the proposed methodology for the type synthesis of flexure systems given in the companion paper to synthesize concepts for complex flexible joints. According to the joint characteristics other than other flexure systems, a basic design philosophy and a general type synthesis process for flexible joints are presented firstly. The numerations and type synthesis for four commonly used flexible joint types, i.e. flexible revolute joints (FRJs), flexible translational joints (FTJs), flexible universal joints (FUJs), and flexible spherical joints (FSJs) are investigated in detail. As a result, not only a variety of known flexible joints are systematically surveyed and classified, but also are some new flexible joints developed. The output of this process is the derivation of a multiple of flexible joint concepts that would then be modeled and optimized by existing modeling and analysis methods.

scholarly journals Type synthesis of freedom and constraint elements for design of flexure mechanisms

2013 ◽  
Vol 4 (2) ◽  
pp. 263-277 ◽  
Author(s):  
H.-J. Su ◽  
C. Yue
Keyword(s):  
Screw Theory ◽  
Building Blocks ◽  
Rigid Bodies ◽  
Hybrid Structures ◽  
Design Stage ◽  
Type Synthesis ◽  
Parallel Structures ◽  
Synthesis Procedure ◽  
Serial Chains ◽  
Basic Motion

Abstract. In this paper, we present the type synthesis of freedom and constraint elements for design of general flexure mechanisms. As an important step in the conceptual design stage, the goal of type synthesis is to qualitatively determine the topology or connectivity of flexure elements and rigid bodies in a mechanism. The synthesis procedure presented here is based on a recently emerging screw theory based approach for flexure mechanisms. We first categorize a list of commonly used atomic flexure primitives including blades, wires, notches and bellow springs etc. We then derive their twist and wrench matrices that mathematically represent their freedom and constraint spaces. The synthesis procedure rigorously follows screw algebra. Freedom elements including R-joints and P-joints are defined as basic motion elements that allow a single rotation or a single translation. By using parallel structures of these flexure primitives, eleven designs of R-joints and eight designs of P-joints are systematically synthesized. As a duality, constraint elements including P-constraints and R-constraints remove a single translation or rotation. In contract to freedom elements, we synthesized serial chains of flexure primitives and obtained six designs of P-constraints and three designs of R-constraints. These freedom and constraint elements form a catalogue of basic building blocks for designing more complex flexure mechanisms. At last we utilize four design examples to demonstrate how to synthesize hybrid structures with serial and parallel combination of these elements.

Type Synthesis of Three-Degree-of-Freedom Translational Compliant Parallel Mechanisms

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Cong Yue ◽  
Ying Zhang ◽  
Hai-Jun Su ◽  
Xianwen Kong
Keyword(s):  
Screw Theory ◽  
Rigid Bodies ◽  
Degree Of Freedom ◽  
Design Stage ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Geometric Conditions ◽  
Synthesis Procedure ◽  
Flexure Joints ◽  
Three Degree Of Freedom

In this paper, we apply screw theory to type synthesis of compliant parallel mechanisms (PMs) with translational degree-of-freedom (DOF). Compliant PMs are formed by a moving platform supported by three or more limbs each of which is a serial chain of flexure joints and rigid bodies. They achieve movement through the deformation of flexure joints and have been widely used in precision machinery. As an important task in the conceptual design stage, the goal of type synthesis is to determine the chain of each limb as well as their relationship when they are assembled in parallel for a prescribed motion pattern. In our approach, we study a category of commonly used flexure primitives and flexure elements whose freedom and constraint spaces are characterized by twists and wrenches in screw theory. Following the well-studied synthesis procedure for rigid body PMs, we propose a synthesis procedure for compliant PMs via screw theory. As an example, we demonstrate the procedure for synthesizing compliant PMs with three translational DOF. Tables of limbs, types, and geometric conditions for the assemblies of these limbs are presented. The paper provides a catalog of 3DOF translational compliant PM designs. At last, we developed finite element simulation to validate one of the synthesized designs.

Type Synthesis of 3-DOF Translational Compliant Parallel Mechanisms

2013 ◽  
Author(s):  
Cong Yue ◽  
Hai-Jun Su ◽  
Xianwen Kong
Keyword(s):  
Screw Theory ◽  
Rigid Bodies ◽  
Design Stage ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Geometric Conditions ◽  
Serial Chain ◽  
Synthesis Procedure ◽  
Flexure Joints ◽  
Three Degree Of Freedom

In this paper, we apply screw theory to the type synthesis of compliant parallel mechanisms (PMs). Compliant PMs are formed by a moving stage supported by three or more limbs each of which is a serial chain of flexure joints and rigid bodies. They achieve movement through the deformation of flexure joints and have been widely used in precision machinery. As an important task in the conceptual design stage, the goal of type synthesis is to determine the chain of each limb as well as their relationship when they are assembled in parallel for a prescribed motion pattern. Our approach starts with a category of commonly used flexure primitives and flexure elements whose freedom and constraint spaces are characterized by twists and wrenches in screw theory. Following the well-studied synthesis procedure for rigid body PMs, we propose a synthesis procedure for compliant PMs via screw theory. This procedure consists of four basic steps: decomposition of the screw system of the constraint space, type synthesis of limbs, assembling limbs and design of flexure joints. As an example, we demonstrate the procedure for synthesizing compliant PMs for three degree-of-freedom (DOF) translational motions. Tables of limbs, types and geometric conditions for the assemblies of these limbs are presented. The paper provides a catalogue of compliant PM designs with three translational motions. At last, we provide a case study of applying finite element simulation to validate one of the synthesized designs.

Screw Theory Based Methodology for the Deterministic Type Synthesis of Flexure Mechanisms

2011 ◽  
Vol 3 (3) ◽  
Author(s):  
Jingjun Yu ◽  
Shouzhong Li ◽  
Hai-jun Su ◽  
M. L. Culpepper
Keyword(s):  
System Theory ◽  
Screw Theory ◽  
Building Blocks ◽  
Mathematical Tool ◽  
Geometric Form ◽  
Type Synthesis ◽  
Mechanism Synthesis ◽  
Flexure Mechanism ◽  
Synthesis Methodology ◽  
Set Operation

Flexure mechanism synthesis, however, is still a comparably difficult task. This paper aims at exploring a simple but systematic type synthesis methodology for general flexure mechanisms. The applied mathematical tool is reciprocal screw system theory in geometric form, and the proposed approach is an improvement of freedom and constraint topology (FACT), which is based on the FACT approach, combining with other methods including equivalent compliance mapping, set operation on building blocks, etc. As a result, it enables the type synthesis of flexure mechanisms simple, complete, and effective. What is more significant is that the proposed approach makes the unified type synthesis of both constraint-based and kinematics-based flexure mechanisms available. That is also the new contribution to the flexure de-sign.

Conceptual Design of 2-DOF Flexure-Based Sensing Mechanisms for Superconductor Gravity Gradient

2015 ◽  
Author(s):  
M. Jia ◽  
R. P. Jia ◽  
J. J. Yu
Keyword(s):  
Finite Elements ◽  
Conceptual Design ◽  
Screw Theory ◽  
Analytical Models ◽  
Gravity Gradient ◽  
Type Synthesis ◽  
Finite Elements Analysis ◽  
Compact Structure ◽  
Sensing Mechanism ◽  
Analysis Models

By employing screw theory and the freedom and constraint topology (FACT), the type synthesis for 2-DOF flexure-based sensing mechanism of superconductor gravity gradient was produced with the parameterized compliance approach. Six types of mechanism with 1R1T DOF were deduced with freedom and constraint pattern in parallel topologies. Based on the compliance analysis, one type was selected as preferred sensing mechanism with the comparison of freedom, main direction compliance, parasitic errors, precision and complexity. For reducing the parasitic and coupling errors, optimization was produced with the parameterized compliance approach. Then specific geometric properties were presented with compact structure for the measurement application. The simulations showed the results of analytical models were close to that of FEA (finite elements analysis) models and the maximum errors of compliance parameters were less than 6%. The conceptual design of 2-DOF flexure-based sensing mechanisms could reach the required functions.

scholarly journals A New Method for Type Synthesis of 2R1T and 2T1R 3-DOF Redundant Actuated Parallel Mechanisms with Closed Loop Units

2020 ◽  
Vol 33 (1) ◽  
Author(s):  
Yongquan Li ◽  
Yang Zhang ◽  
Lijie Zhang
Keyword(s):  
Closed Loop ◽  
Screw Theory ◽  
Line Graph ◽  
Degree Of Freedom ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Allocation Criteria ◽  
Grassmann Line Geometry ◽  
Moving Platform ◽  
Atlas Method

Abstract The current type synthesis of the redundant actuated parallel mechanisms is adding active-actuated kinematic branches on the basis of the traditional parallel mechanisms, or using screw theory to perform multiple getting intersection and union to complete type synthesis. The number of redundant parallel mechanisms obtained by these two methods is limited. In this paper, based on Grassmann line geometry and Atlas method, a novel and effective method for type synthesis of redundant actuated parallel mechanisms (PMs) with closed-loop units is proposed. Firstly, the degree of freedom (DOF) and constraint line graph of the moving platform are determined successively, and redundant lines are added in constraint line graph to obtain the redundant constraint line graph and their equivalent line graph, and a branch constraint allocation scheme is formulated based on the allocation criteria. Secondly, a scheme is selected and redundant lines are added in the branch chains DOF graph to construct the redundant actuated branch chains with closed-loop units. Finally, the branch chains that meet the requirements of branch chains configuration criteria and F&C (degree of freedom & constraint) line graph are assembled. In this paper, two types of 2 rotational and 1 translational (2R1T) redundant actuated parallel mechanisms and one type of 2 translational and 1 rotational (2T1R) redundant actuated parallel mechanisms with few branches and closed-loop units were taken as examples, and 238, 92 and 15 new configurations were synthesized. All the mechanisms contain closed-loop units, and the mechanisms and the actuators both have good symmetry. Therefore, all the mechanisms have excellent comprehensive performance, in which the two rotational DOFs of the moving platform of 2R1T redundant actuated parallel mechanism can be independently controlled. The instantaneous analysis shows that all mechanisms are not instantaneous, which proves the feasibility and practicability of the method.

An expanded isoindigo unit as a new building block for a conjugated polymer leading to high-performance solar cells

2014 ◽  
Vol 2 (15) ◽  
pp. 5427-5433 ◽  
Author(s):  
Shugang Li ◽  
Zhongcheng Yuan ◽  
Jianyu Yuan ◽  
Ping Deng ◽  
Qing Zhang ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Building Block ◽  
Conjugated Polymer ◽  
High Performance ◽  
Fill Factor ◽  
Solar Cell Device ◽  
Donor Acceptor ◽  
First Time

An expanded isoindigo unit (IBTI) has been incorporated into a donor–acceptor conjugated polymer for the first time. The PCE of the solar cell device based on the new polymer reached 6.41% with a fill factor of 0.71.

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