Method For Synthesis Of Mechanisms Research Articles

Configuration synthesis and screening method for multiple closed-loop unit tandem mechanisms

To broaden the methods of configuration synthesis, this study proposes a new method for configuration synthesis and screening of multiple closed-loop unit tandem mechanisms. Firstly, some closed-loop configurations are taken as basic units, and the closed-loop basic units are synthesized in series under the condition of considering the basic unit types, contacts, and input and output relationships. Secondly, the connectivity of the mechanism is obtained by weighting the adjacency matrix, and the entropy weight method is used for the first time to establish a comprehensive evaluation index coefficient to assess the quality of the mechanism. Then, an improved simulated annealing-greedy algorithm is proposed and an algorithm software screening platform is built to screen mechanisms. Finally, the multi-fingered grasper is used as design case to verify the practicality of the proposed configuration synthesis and screening method. This study can provide a reference for theoretical research on the configuration synthesis and screening methods of multiple closed-loop unit tandem mechanisms.

Insights into the Electrochemical CO2RR Performance and Binding of Small Molecules on Quaternary Thiospinels Ag2FeSn3S8 and Cu2FeSn3S8.

Using a mechanical synthesis method in the form of ball milling and an additional annealing step, a novel and accelerated route for the synthesis of the thiospinels toyohaite (Ag2FeSn3S8) and rhodostannite (Cu2FeSn3S8) was discovered. Both thiospinels display faradaic efficiencies of up to 73% for CO2 reduction to CO using an organic electrolyte in an H-type cell. The materials were furthermore implemented in a zero-gap electrolyzer, with toyohaite producing 22% CO and 52% H2 at 100 mA cm-2 and rhodostannite 28% CO and 37% H2. The catalytically active sites are studied using density functional theory, revealing strong CO binding interactions on both Ag and Cu, whereas Sn is found to contribute to the decomposition of Ag2FeSn3S8 and Cu2FeSn3S8 by coordination with oxygen. Postmortem analysis of the thiospinel-based electrodes by means of SEM-EDX, XRD, XPS, and Mössbauer spectroscopy showed sulfur leaching from the catalysts after applying 100 mA cm-2. These spectroscopic results-in conjunction with DFT calculations of the oxidized surfaces-suggest that the catalytically active species consists of metal oxides. As a conversion of the metal sulfides into the corresponding metallic species was observed via XRD, the decomposition pathways of both catalysts were also computed using DFT; thus, elucidating the energetically most favorable decomposition products and expanding the possible composition of the catalysts postelectrolysis.

A Synthesis Method of Open-Chain Coupled Serial Linkage Mechanism Fusing Trajectory and Posture

In order to meet the motion characteristics requirements of multi-objective fusion of execution components, a synthesis method of open-chain coupled serial linkage mechanism fusing trajectory and posture is proposed. According to periodic change characteristics of the execution component trajectory and posture of the linkage mechanism, the motion characteristics equation including trajectory and posture information is established by using Fourier series. The harmonic parameters of the link trajectory and posture are calculated according to the principle of discrete Fourier transform. The complex vector theory is applied to determine the functional relationship between the harmonic parameters of the trajectory and posture and the independent variable of the linkage mechanism, and furthermore the motion synthesis equation of the open-chain linkage mechanism fusing trajectory and posture information is established. The linkage mechanism parameters are calculated using Mathcad Prime software. The single-degree-of-freedom open-chain coupled serial linkage mechanism fusing trajectory and posture information is obtained by using a noncircular gear planetary gear train to couple the connection points of the linkage mechanism. The correctness of the method is verified through an example.

Configuration Synthesis Method of Multi-Mode Parallel Mechanism Based on Variable Mobility Branch

Abstract In order to obtain more configurations of multi-mode parallel mechanism with the expected motion modes, a new configuration synthesis method of multi-mode parallel mechanism is proposed in this paper. The generation principle of parallel mechanism with multiple motion modes is analyzed. The relation between the motion of moving platform and the motion of branch is obtained. The finite motion and instantaneous motion of existing variable mobility branches are analyzed, and variable mobility branches are decomposed into variable mobility generators. By using variable mobility generators to construct variable mobility branches, a configuration synthesis method of multi-mode parallel mechanism based on variable mobility branch is proposed. Taking the multi-mode parallel mechanism with 2T1R and 2R1T motion modes as an example, a new class of multi-mode parallel mechanisms is obtained. The proposed method enriches the configuration synthesis theory of multi-mode parallel mechanism and the synthesis results enrich the configurations of multi-mode parallel mechanism.

Synthesis on cardioid crank rocker mechanism with approximate uniform motion

The cardioid crank is a planetary mechanism that generates a cardioid line. It is a crank with varying length and speed that moves along the cardioid line. The cardioid crank is used to replace the crank of the crank rocker mechanism, and its rocker mechanism with approximate uniform motion is obtained. The kinematic analysis method of the cardioid crank rocker mechanism is studied in this paper. The calculating method for the limit position and oscillating angle and the time ratio of the guide bar are given. Finally, the approximate uniform motion conditions of the rocker are obtained. The synthesis method of the approximate uniform motion mechanism is put forward in accordance with the time ratio or rocker oscillate angle, the minimum length of the guide bar is calculated, and the influence of center distance on the kinematic performance of the mechanism is discussed.

Research on configuration synthesis method of multi-mode parallel mechanism based on lockable joints

Research on configuration synthesis method of multi-mode parallel mechanism based on lockable joints

Non-Noble Nanoparticles Cocatalysts in TiO<sub>2</sub> for Photocatalytic Hydrogen Production from Water. A review

Among the many methods, the use of solar photocatalytic water splitting to produce hydrogen is the most promising one. The water splitting process mainly includes the following three steps: solar energy capture, transfer and separation of photogenerated charges, and catalytic protons to generate hydrogen. At present, a high number of studies mainly focus on the first and second steps, and there are relatively few studies garding the third step. The introduction of a co-catalyst can effectively improve the photocatalytic activity and increase the hydrogen production rate. Co-catalysts mainly include noble metal catalysts and non-noble metal catalysts. Although noble metal catalysts provide a better performance, their high price limits their wide application. Therefore, it is particularly important to develop efficient and inexpensive non-precious metal catalysts. This paper briefly summarizes the use of non-noble metal catalysts based on TiO2 photocatalytic hydrogen evolution. The action mechanism and related synthesis methods of the co-catalysts are discussed, and the development direction of non-noble metal cocatalysts is briefly described.

Optimization Synthesis of Hybrid Six-Bar Mechanism With Non-Circular Gear Constraints

AbstractA novel hybrid six-bar mechanism with non-circular gear constraints and its optimal synthesis method for complex multi-pose rigid body guidance tasks are proposed. An innovative optimization module is proposed to optimize the non-circularity and smoothness of non-circular gear pitch curves. The optimization synthesis of this mechanism is divided into two steps. The first step is to conduct multi-objective constraint optimization with pose error and non-circular gear pitch curve as optimization objectives to obtain the required diversified non-inferior solution set. Second, a set of solutions are selected from the solution set to construct the optimization function of non-circular gear pitch curves. The non-circularity and smoothness of the pitch curve are optimized to the maximum extent, and the pose change is ensured to be small. Finally, the multi-pose picking and planting of vegetable pot seedlings were realized using the proposed mechanism and optimization synthesis method. The final optimization design results show that the error between the actual pose and the required pose of the compact hybrid mechanism is small. The optimization effect of non-circularity and smoothness of non-circular gear pitch curves is pronounced. The effectiveness of the mechanism is verified via kinematic simulation.

Modified Shadow Robot Control method for optimal path synthesis of mechanisms: Application to five-link mechanism

For optimal path synthesis of a mechanism with a single degree of freedom (DOF), a powerful method called Shadow Robot Control (SRC) has been recently proposed in the literature. However, this method is restricted to synthesis problems with prescribed timing (i.e. problems in which a particular input crank angle is associated with each point of the desired trajectory). In this paper, the SRC method was elaborated and modified to be capable of synthesizing both prescribed and nonprescribed timing problems. For this purpose, a new structure of contour error and objective function estimation was presented. As a result, there is no need to consider the input angles (crank angles) corresponding to desired path points as optimization parameters, even for non-prescribed timing problems. This prevents unnecessarily enlarging the search space, providing a more effective and robust optimization method (with respect to initial guess). The synthesis of a geared five-link mechanism was used to detail the proposed algorithm as a case study. Despite the five-link mechanism capability and simplicity of generating a complicated trajectory, this single DOF path generator seems less investigated in the literature. Few existing numerical problems of the five-link mechanism in the literature were solved. The comparison of the results shows the effective performance of the proposed algorithm in synthesizing the mechanism.

Research on mechanism dimension synthesis method of 4-bar mechanism based on improved artificial bee colony algorithm

Research on mechanism dimension synthesis method of 4-bar mechanism based on improved artificial bee colony algorithm

On the Solution of Region-Based Straight-Line Mechanism Design Optimization

A universal design method for synthesis problems of mechanisms that realize the approximate straight-line trajectory is presented in this paper. First, given the expected straight line and prescribed fixed pivots, a general mathematics model with angles as design parameters to determine the initial position of two side links is established, through which all infinite possible straight-line mechanisms are obtained. Then, kinematic constraints are imposed, including type, transmission angle, size, straightness, and defect. All feasible solution mechanisms that meet the constraints are calculated and can be expressed in solution regions. It is intuitive and comprehensive for designers to observe the distribution pattern of the solution. In the end, an optimal high-precision straight-line mechanism can be selected in the feasible solution regions by setting an optimization aim. The second-order osculating mechanism synthesis method can provide more solutions for designers, but designers can use the third-order osculating mechanism synthesis method when a higher straightness requirement is imposed. This method addresses the synthesis problem of this kind of mechanism for straight-line guidance and the problem of choosing an optimal solution from an infinite number of solutions.

Accurate detection mechanism synthesis and robot-assisted recognition method for ankle instantaneous motion

The latest rehabilitation robot based on generalized spherical parallel mechanism (GSPM) forces higher requirements for the accurate ankle motion description, but the talus, ankle core component, is hidden within soft tissue and difficult to be directly observed and described. For this problem, the accurate detection robot and robot-assisted instantaneous motion recognition method for ankle based on it are proposed. Firstly, a foot-talus coupled motion model based on ankle bone structure is established, functional requirements of the detection robot are clarified. Secondly, a type synthesis method of variable GSPM is proposed based on screw theory, and partially decoupled under-actuated GSPMs are constructed. This method can directly determine the actuators and sensors arrangement during the non-instantaneous limb synthesis to avoid complex judgment and screening. Then, the principle and method of robot-assisted ankle instantaneous motion recognition are revealed and summarized by clarifying kinematic mapping relationship of human-machine system. This method can accurately recognize talus orientation and drive repetitive foot motion to weaken subjects' fatigue factors. Finally, based on the established virtual prototype, the rationality and feasibility of the robot-assisted recognition method are verified.

Synthesis method of new weakly-coupled 5-DOF compliant parallel mechanism

Synthesis method of new weakly-coupled 5-DOF compliant parallel mechanism

Fusing Topology Optimization and Pseudo-Rigid-Body Method For the Development of a Finger Exoskeleton

Robotic hand exoskeletons can assist people who suffer from hand.functional disabilities caused by a stroke. However, currently existing hand exoskeletons remain inadequate in terms of user-friendly design, lightweight structure, and accurate modeling of hand motion. In this study, a large displacement compliant mechanism is developed as a finger exoskeleton. First, a topology configuration is developed which contains information on hand biomechanics and thus yields an efficient force-deflection mechanism for a finger. A pseudo-rigid-body model is then established using a large-deformation flexible hinge to solve the point flexure problem to create a finger exoskeleton that functions as intended. Finally, the mechanism synthesis method is used for parameter optimization to ensure that the output port of the device matches the motion of the finger. Using the proposed method, an integrated compliant finger exoskeleton is developed, and the performance of the exoskeleton is evaluated. The experimental result shows that the finger exoskeleton prototype provides suitable movement guidance for the index finger, which demonstrates that the proposed method may be a good way in the design of hand exoskeletons.

Synthesis and Optimization Method of Exoskeleton Mechanism Based on Human-machine Fusion

Synthesis and Optimization Method of Exoskeleton Mechanism Based on Human-machine Fusion

The action of enhanced reactive oxygen species production through the dopant of Al2O3/GO in piezoelectric ZnO

The application of Zinc oxide has drawn great attention in bacterial inhibition and contaminant degradation field in recent years. The internal structure and the morphology of the material was characterized by XRD, XPS, SEM, TEM. The dopant of 1 wt% graphene oxide（GO） and 30 wt% Al2O3 shows excellent piezocatalytic and antibacterial ability. Application potential of the material is investigated by the degradation of RhB and the inhibition of Bacillus. It is found that the RhB solution can be degraded 92.5% by ZA-GO in 15 min, while ZnO can degrade 64.2%. It shows superior catalytic behavior in successive experiments of degradation of RhB without obvious decrease in efficiency. The quenching experiment combined with ESR spectrum demonstrate that both •O2- and •OH radicals were generated, while •OH did the most damage. Bacterial inhibition tests have also proven that the generation of reactive oxygen species cause the bacteria inactivated. In this work, a novel composite ZnO-Al2O3/GO has been successfully prepared based on mechanical synthesis method. Graphene oxide has higher mechanical strength and higher specific surface area. Zn ions doping carbon materials not only increases its stability, but also promotes its conductivity. The doping of Al atoms effectively reduce the work function of ZnO. Graphene oxide together with alumina coordinate the band gap of piezoelectric materials ZnO and the catalytic reaction efficiency was dramatically enhanced. What’s more, this work provides a facile approach eliminated the use of solvents and organic reagents, ensuring greater environmental safety. The novel zinc oxide matrix composites are depicted as a promising candidate to be used as intelligent antibacterial agent and alleviate environmental pollution.

Geometric synthesis method of compliant mechanism based on similarity transformation of pole maps

Abstract. This paper presents a geometric synthesis method for compliant mechanisms based on similarity transformation of pole maps. Motion generation is a typical and common mechanism synthesis task, so this study takes it as the design requirement to expound the proposed method. Most of the current research work relies on numerical solution of the nonlinear Bernoulli–Euler beam model, numerical simulations or physical experiments to study the synthesis method of compliant mechanisms. There is a lack of simpler and more efficient methods to achieve motion generation of compliant mechanisms with various topologies. This study is based on pole map which is a geometric tool to describe the motion of rigid-body mechanisms. In this paper, we first demonstrate the feasibility of applying the similarity transformation of pole map to compliant mechanisms. It is proved that the pole map of compliant mechanisms has the same characteristic as rigid-body mechanisms during similarity transformation. Then we present the procedure of synthesis method in detail and expound the establishment method of function module which can avoid the functional defects of the final designed mechanism. At last, we take the compliant geared linkages and compliant four-bar linkage as examples to illustrate the novel synthesis approach. The result is an applicable and effective synthesis method for motion generation of compliant mechanisms.

ЗАСТОСУВАННЯ МЕХАНІЗМУ ЧЕТВЕРТОГО КЛАСУ ДЛЯ ПРИВОДУ ВУШКОВИХ ГОЛОК ОСНОВОВ’ЯЗАЛЬНОЇ МАШИНИ

Development and research of functionally-adequate target mechanisms of technological machines of light industry with application of applied CAE-programs. Used the apparatus of vector algebra; analytical and numerical methods for determining the position functions of planar mechanisms containing a structural group of the fourth class of the second order, based on the vector transformation of coordinates; random search method for metric synthesis of flat mechanisms; methods of computer visualization and animation of kinematic schemes of flat mechanisms of higher classes. Mathematical models describing the position functions of the mechanism of eyelets of a warp knitting machine containing a structural group of the fourth class of the second order with rotating kinematic pairs in the form of angles of moving links, free vectors constructed on these links and radius vectors of characteristic points of the mechanism as a function of the angle of rotation of the master crank. The geometrical parameters of the flat six-link mechanism of eyelets for the warp knitting machine containing the structural group of the fourth class of the second order with rotating kinematic pairs as a result of metric synthesis of the mechanism by random search in CAE-program are determined; computer circuit modeling of the obtained mechanism is performed; graphs of visualization and animation of the kinematic scheme of the received mechanism are constructed; identification of the kinematic scheme of the obtained mechanism for compliance with the accepted structure; the received graph of function of position of an auricular needle of the mechanism of the fourth class; the functions of the position of the eye needle of the new mechanism and the mechanism of the basic knitting machine OV-7 are compared. The structure of a flat six-link mechanism, containing structural groups of the fourth class of the second order with rotating kinematic pairs, is proposed for use as a drive in a warp knitting machine on the example of the mechanism of oscillating movement of eyelets. The geometric dimensions of the moving parts of the functionally adequate mechanism of the fourth class for the drive of the eye needles of the basic knitting machine are determined. Software blocks for automated computer metric synthesis and calculation of link angles and radius vectors of characteristic points of the mechanism in the CAE program have been created. Practical Value is to use the results for the design and construction of flat mechanisms of the fourth class with rotating kinematic pairs of warp knitting machines, in which the working bodies make stops during the work process.

A new method for type synthesis of parallel mechanisms using screw theory and features of genetic algorithms

The type synthesis is a fundamental phase in the design of parallel mechanisms. The type synthesis process consists of a systematic approach to generate all possible mechanical structures that are capable of performing a determined movement. The type synthesis presents two main steps: (1) generation of limbs and (2) assembly of parallel manipulators. There are basically three main approaches for type synthesis of parallel mechanisms: screw theory, lie group of rigid body displacements and evolutionary morphology. This paper presents a new method that combines screw theory and characteristics of genetic algorithms. Using the proposed method, it was generated new solutions of 3-DOF limbs (2R1T and 1R2T) for parallel manipulators.

Research on a novel configuration synthesis method of no-spin traction continuously variable transmission

The no-spin design methodology of the traction continuously variable transmission (CVT) is the latest achievement in the field of CVT mechanism research. According to this methodology, four basic no-spin traction CVT mechanisms are acquired. In order to obtain more no-spin traction CVT mechanism topologies, a novel Configuration Factor Table (CFT) method for the configuration synthesis of basic no-spin traction CVT mechanisms is proposed, of which the main idea is from the basic law of separation and free combination of genes. Then the five main steps of configuration synthesis using this CFT method are described in detail. Based on this method, the configuration synthesis case studies of logarithmic CVT and conical CVT are carried out. The results show that 14 variant mechanisms of logarithmic CVT and 10 variant mechanisms of conical CVT are obtained. Among them, the swing-logarithmic CVT, rolling-logarithmic CVT, swing-conical CVT and rolling-conical CVT are considered to have the potential to become the new generation of high-power transmitting and high-efficiency traction CVTs.