scholarly journals Type Synthesis of Fully Decoupled Three Translational Parallel Mechanism with Closed loop Units and High Stiffness

2021 ◽  
Author(s):  
Shihua Li ◽  
Sen Wang ◽  
Haoran Li ◽  
Yongjie Wang ◽  
Shuang Chen
Keyword(s):  
Closed Loop ◽  
Screw Theory ◽  
Synthesis Method ◽  
Diagonal Matrix ◽  
Parallel Mechanisms ◽  
Durability Test ◽  
High Stiffness ◽  
New Synthesis ◽  
New Criterion ◽  
Coupling Mechanisms

Abstract In this paper, a new synthesis method of fully decoupled three translational (3T) parallel mechanisms (PMs) with closed loop units and high stiffness is proposed based on screw theory. Firstly, a new criterion for the full decoupled of PMs is presented that the reciprocal product of the transmission wrenc h screw matrix and the output twist screw matrix of PMs is a diagonal matrix, and all elements on the main diagonal are nonzero constants. The forms of the transmission wrench screws are determined by the criterion. Secondly, the forms of the actuated and unactuated screws can be obtained according to their relationships with the transmission wrench screws. The basic decoupled limbs are generated by combination of the above actuated and unactuated screws. Finally, a closed loop units construction method is investigated to apply the decoupled mechanisms in a better way on the high stiffness occasion. The closed loop units are constructed in the basic decoupled limbs to generate a high stiffness fully decoupled 3T PM. Kinematic and stiffness analys e s show that the Jacobian matrix is a diagonal matrix, and the stiffness is obviously higher than that of the orthogonal coupling mechanisms, which verifies the correctness of the proposed synthesis method. The mechanism synthesized by this method has a good applicati on prospect in vehicle durability test platform.

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.

scholarly journals Type Synthesis of 3-Translational Redundant Actuated Parallel Mechanisms With Closed-Loop Branch Chains Based On Graphical Approach

2021 ◽  
Author(s):  
Yongquan Li ◽  
Hong-Sheng Jiang ◽  
Tian-Yu Zheng ◽  
Ke-Long Xi ◽  
Han Jing ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Parallel Mechanism ◽  
Large Scale ◽  
Vibration Isolation ◽  
Closed Loop ◽  
Screw Theory ◽  
Simple Calculation ◽  
Parallel Mechanisms ◽  
Logistics Industry ◽  
Graphical Approach

Abstract The 3-translational parallel mechanism is widely used in industrial, medical, and military fields, among others. With the development of the national logistics industry, a pressing need for a kind of 3-translational parallel mechanism emerged. Such mechanisms have high stiffness and high bearing capacity and are used for cargo handling and sorting. A novel method based on the graphical approach was proposed for the synthesis of 3-translational redundancy actuated parallel mechanism with closed-loop branch chains. The new mechanism has four symmetrically arranged branch chains, which eases subsequent kinematics and dynamics analyses while providing good mechanical properties. Based on the graphical approach theory, according to the constraint number contained in the branch chain, two types of redundant driven branch chains with closed-loop structures were constructed. The first type includes rotation constraint in one direction, while the second type includes the rotation constraint in two directions. Based on various combinations of two branch chain types, their allocation schemes can be divided into two types. Moreover, said these two allocation schemes can be integrated into at least 500 and 400 types of 3-translational redundant actuated parallel mechanisms with closed-loop branch chains. Then, the degree of freedom properties of representative mechanisms were tested using the screw theory. A large number of novel mechanisms were integrated assessed using this method, and branch chains such mechanisms were symmetrically distributed. They have a strong bearing capacity, simple calculation, and control, and can be applied to the handling and sorting of goods, large-scale precision machine tools, and large construction machinery vibration isolation systems, among others.

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.

Force Analysis of Spatial Single Closed-Loop Overconstrained Mechanisms

2016 ◽  
Author(s):  
Wenlan Liu ◽  
Yundou Xu ◽  
Jiantao Yao ◽  
Yongsheng Zhao
Keyword(s):  
Closed Loop ◽  
Screw Theory ◽  
Driving Forces ◽  
Parallel Mechanisms ◽  
Force Analysis ◽  
Moving Platform ◽  
Compliance Matrices ◽  
Overconstrained Mechanisms ◽  
Force Problem ◽  
Deformation Compatibility

Taking the Bennett and Schatz mechanisms as examples, force analyses of spatial single closed-loop (SSCL) overconstrained mechanisms are demonstrated aiming to obtain the driving forces/torques and joint reactions of this kind of mechanisms. Firstly, regarding the SSCL overconstrained mechanisms as parallel mechanisms with two supporting limbs, the constraint wrenches and actuation wrenches imposed on the moving platform by the two limbs are discussed, and the mobility of each mechanism is analyzed based on the screw theory. Then, the compliance matrices of the limbs’ constraint wrenches are derived, which contribute to solve the statically indeterminate force problem of the mechanisms. Next, by combining the force and moment equilibrium equation of the moving platform with the deformation compatibility equation of the corresponding mechanism, the magnitudes of all constraint wrenches and actuation wrenches are solved. Furthermore, the driving forces/torques and joint reactions are derived. Finally, the numerical and simulation results of the two mechanisms are presented.

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

2016 ◽  
Vol 8 (4) ◽  
Author(s):  
Kristan Marlow ◽  
Mats Isaksson ◽  
Saeid Nahavandi
Keyword(s):  
High Performance ◽  
Degrees Of Freedom ◽  
Closed Loop ◽  
Screw Theory ◽  
Parallel Mechanisms ◽  
Force Transmission ◽  
Transmission Performance ◽  
Specific Mechanism ◽  
Serial Chain ◽  
Four Bar Linkage

Singularities are one of the most important issues affecting the performance of parallel mechanisms. Therefore, analysis of their locations and closeness is essential for the development of a high-performance mechanism. The screw theory based motion/force transmission analysis provides such a closeness measure in terms of the work performed between specific mechanism twists and wrenches. As such, this technique has been applied to many serial chain parallel mechanisms. However, the motion/force transmission performance of parallel mechanisms with mixed topology chains is yet to be examined. These chains include linkages in both series and parallel, where the parallel portion is termed a closed-loop subchain (CLSC). This paper provides an analysis of such chains, where the CLSC is a planar four-bar linkage. In order to completely define the motion/force transmission abilities of these mechanisms, adapted wrench definitions are introduced. The proposed methodology is applied to a family of two degrees-of-freedom planar axis-symmetric parallel mechanisms, each with a different CLSC configuration. The presented analysis provides the first complete motion/force transmission analysis of such mechanisms.

scholarly journals Research for a novel class of translational spatial multi-loop coupled mechanisms: Type synthesis and kinematic analysis

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879702 ◽  
Author(s):  
Shuang Zhang ◽  
Jingfang Liu ◽  
Huafeng Ding
Keyword(s):  
Kinematic Analysis ◽  
Degrees Of Freedom ◽  
Synthesis Method ◽  
Future Application ◽  
The Novel ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Split Method ◽  
New Synthesis ◽  
The Family

A novel type synthesis method for a class of spatial multi-loop coupled mechanisms with translational degrees of freedom is proposed in the paper. The novel class of spatial multi-loop coupled mechanisms has a stable topology layout which consists of three branches and three coupled chains. The basic idea of the new structural synthesis method lies at replacing the inputs of one mechanism by the outputs of another, thereby combining several mechanisms, where the topology split method for the topological layout and corresponding degree of freedom splitting principle are provided. The synthesis of the target mechanism is transformed into synthesis of corresponding serial and parallel mechanisms thereby, and a class of spatial multi-loop coupled mechanisms is synthesized. To validate the new synthesis method and to present a theoretical basis for future application, kinematic analysis of a single translational mobility (1T) spatial multi-loop coupled mechanism and a symmetrical two translational degrees of freedom (2T) spatial multi-loop coupled mechanism is performed. This article enriches the family of the spatial mechanisms for further instructing the study of spatial multi-loop coupled mechanisms.

Structure synthesis of reconfigurable parallel mechanisms with closed-loop metamorphic linkages

2017 ◽  
Vol 232 (7) ◽  
pp. 1303-1316 ◽  
Author(s):  
Chunxu Tian ◽  
Yuefa Fang ◽  
Sheng Guo ◽  
Haibo Qu
Keyword(s):  
Closed Loop ◽  
Screw Theory ◽  
Parallel Mechanisms ◽  
Constraint Forces ◽  
Kinematic Chains ◽  
Reconfigurable Mechanisms ◽  
Motion Modes ◽  
Structure Synthesis ◽  
Fixed Base ◽  
Moving Platform

This paper proposes a class of closed-loop metamorphic linkages, which has different phases resulting from links annexing or locking of motors. Reconfigurable limbs are obtained by assembling these metamorphic linkages with kinematic chains. The potential metamorphic linkages are presented and the working phase transformation of the metamorphic linkages is analyzed. After adding suitable kinematic joints to the metamorphic linkage, the reconfigurable limbs whose constraint can be switched among different constraint forces and couples are synthesized. The serial limbs that can provide u ( u = 0, 1, 2) constraint forces and v ( v = 0, 1, 2) constraint couples are constructed by using screw theory method. The reconfigurable limbs which possess different configurations are combined with serial kinematic chains. By connecting the end moving platform to the fixed base with three identical kinematic limbs, a family of reconfigurable mechanisms with closed-loop metamorphic linkages is derived. These mechanisms have various output motion modes, such as 3R, 1T2R, 2T1R, and 3T.

Type Synthesis of Three-DOF Translational Parallel Mechanisms

2003 ◽  
Author(s):  
Jingjun Yu ◽  
Shusheng Bi ◽  
Guanghua Zong ◽  
Tieshi Zhao ◽  
Zhen Huang
Keyword(s):  
Degrees Of Freedom ◽  
Screw Theory ◽  
Synthesis Method ◽  
Reciprocal Relationship ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Constraint Forces ◽  
Novel Synthesis ◽  
Spatial Translation ◽  
Made In

This paper presents a simple but effective type synthesis method for spatial parallel mechanisms with three translational degrees of freedom based on the screw theory. Firstly all possible connecting-chain structures of three-DOF parallel mechanisms are enumerated. According to the reciprocal relationship between screw constraint forces and the motion screw, a novel synthesis method is presented. By using this method, type synthesis for three-DOF translational parallel mechanisms has been made in a systematic and detailed way. As a result, some novel parallel mechanisms generating spatial translation have been obtained. To verify the significance of type synthesis for this kind of mechanism, the paper also gives a concrete application instance, which is used for a micromanipulator for manipulating the bio-cells.

Synthesis, Analytical Characterization and Spectroscopic Investigation of Chloramphenicol Impurity A for the Quality Control of Chloramphenicol and its Formulation as Per International Compendium

2020 ◽  
Vol 17 (5) ◽  
pp. 382-388
Author(s):  
Aparna Wadhwa ◽  
Faraat Ali ◽  
Sana Parveen ◽  
Robin Kumar ◽  
Gyanendra N. Singh
Keyword(s):  
Quality Control ◽  
Synthesis Method ◽  
Analytical Techniques ◽  
International Markets ◽  
Therapeutic Effects ◽  
Reference Standard ◽  
Working Standard ◽  
Prior Art ◽  
New Synthesis ◽  
Synthetic Procedure

Objective: The main aim of the present work is to synthesize chloramphenicol impurity A (CLRMIMP- A) in the purest form and its subsequent characterization by using a panel of sophisticated analytical techniques (LC-MS, DSC, TGA, NMR, FTIR, HPLC, and CHNS) to provide as a reference standard mentioned in most of the international compendiums, including IP, BP, USP, and EP. The present synthetic procedure has not been disclosed anywhere in the prior art. Methods: A simple, cheaper, and new synthesis method was described for the preparation of CLRM-IMP-A. It was synthesized and characterized by FTIR, DSC, TGA, NMR (1H and 13C), LC-MS, CHNS, and HPLC. Results: CLRM-IMP-A present in drugs and dosage form can alter the therapeutic effects and adverse reaction of a drug considerably, it is mandatory to have a precise method for the estimation of impurities to safeguard the public health. Under these circumstances, the presence of CLRM-IMP-A in chloramphenicol (CLRM) requires strict quality control to satisfy the specified regulatory limit. The synthetic impurity obtained was in the pure form to provide a certified reference standard or working standard to stakeholders with defined potency. Conclusion: The present research describes a novel technique for the synthesis of pharmacopoeial impurity, which can help in checking/controlling the quality of the CLRM in the international markets.

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