The Optimum Design of a 6 DOF Fully-Parallel Micromanipulator for Enhanced Robot Accuracy

1989 ◽  
Author(s):  
C.-S. Han ◽  
D. Tesar ◽  
A. E. Traver
Keyword(s):  
Optimization Theory ◽  
Local Stress ◽  
Internal Force ◽  
Scale Model ◽  
Robot Accuracy ◽  
Cad Cam ◽  
Deflection Analysis ◽  
Motion Range ◽  
Critical Components ◽  
Velocity Transmission

Abstract The micromanipulator is a small amplitude, high resolution motion device to enhance robot accuracy by providing fine adjustments for precise error compensation and delicate force control. This paper addresses design objectives and optimization procedures for design of a unique 6 degree-of-freedom (DOF) fully-parallel micromanipulator. Using kinematic and dynamic modeling analysis, optimum geometric parameters are found which satisfy the desired motion range, effective force and velocity transmission and minimum input loading due to the bending of flexural joints. Computer simulations, optimization theory, and the finite element method are used to model, synthesize, and analyze micromanipulator components. Internal force analysis is performed to design the hardware components for critical load conditions. Using a CAD/CAM system, a full scale model of the mechanism has been created, and local stress and deflection analysis has been performed on the critical components.

scholarly journals Critical Flow Centrality Measures on Interdependent Networks with Time-Varying Demands

2019 ◽  
Author(s):  
James Williams
Keyword(s):  
Flow Analysis ◽  
Network Capacity ◽  
Scale Model ◽  
Centrality Measures ◽  
Critical Flow ◽  
Degradation Analysis ◽  
Standard Component ◽  
Novel Method ◽  
Critical Components ◽  
Support Decision Making

This paper describes a novel method for allowing urban planners and municipal engineers to identify critical components of interdependent infrastructure networks whose attributes vary over time. The method is based on critical flow analysis, wherein system components are ranked by their role in facilitating the flow of resources to critical locations. The intent of the method is to support decision making by providing a means by which stakeholders can reason about the way in which changes in supply, demand, or network capacity can alter the distribution of critical flows within an urban environment. Individual infrastructure systems are modeled as networks that can be linked to one another by physical and geospatial dependencies. A simple instantiation of the method is presented and evaluated on a district-scale model of a city that contains water and electricity networks. The paper also discusses two forms of reliability analysis based on critical flows: a composite measure incorporating edge reliability, and a variation on standard component failure/degradation analysis.

Design of Constant-Velocity Transmission Devices Using Parallel Kinematics Principle

2014 ◽  
Author(s):  
Jingjun Yu ◽  
Jiazhu Yu ◽  
Kang Wu ◽  
Xianwen Kong
Keyword(s):  
Constant Velocity ◽  
Parallel Mechanisms ◽  
Parallel Kinematics ◽  
Pure Rolling ◽  
Motion Range ◽  
New Type ◽  
Moving Coordinate ◽  
Instant Screw Axis ◽  
Velocity Transmission ◽  
Spherical Gear

This paper presents a new type of constant-velocity transmission devices based on parallel mechanisms with properties of equal-diameter spherical pure rolling. The method we used is essentially an extension of the planar ellipse gear to the spherical one. Both the fixed and moving axodes of a specified parallel mechanism are obtained, as traced by the spatial instant screw axis (ISA) with respect to the fixed and moving coordinate systems. Based on Poinsot’s theorem and achievements, a series of these parallel mechanisms which satisfy constant-velocity condition have been disclosed correspondingly. Their motion range and transmission performances are also explored by taking the 3-4R mechanism as an instance. As the main part of this paper, two important applications for this type of constant-velocity transmission devices are also explored. One is used as a gearless spherical gear, and the other is used as a constant-velocity universal joint (CVJ). Simulations were fulfilled on ADAMS to verify the transmission performance in terms of different applications.

Local Stress Analysis and Model Test of Arch Foot for a Steel Box Arch Bridge on High-Speed Railway

2010 ◽  
Author(s):  
X. H. He ◽  
A. H. Zhao ◽  
A. Scanlon ◽  
L. P. Peng
Keyword(s):  
Model Test ◽  
High Speed ◽  
Local Stress ◽  
Scale Model ◽  
Fe Model ◽  
Stress Distributions ◽  
High Speed Railway ◽  
Arch Bridge ◽  
Railway Line ◽  
Under Construction

A large span X-style steel box arch bridge is under construction for a high speed railway line between Nanning and Guangzhou. A 1:8 scale model test of the arch foot for the bridge is described. Based on the two-step finite element (FE) analysis method using commercial software, a global FE model of the bridge and local FE model of arch foot are developed. Local stress distributions of the arch foot are obtained. Typical experimental stresses measured in the scale model are presented and compared against those obtained from FE analyses of different models. The results are used to provide recommendations for design of the bridge and other similar bridges.

scholarly journals VERTICAL CYLINDRICAL TANK WITH ANGULAR GEOMETRICAL IMPERFECTION

2005 ◽  
Vol 11 (3) ◽  
pp. 175-183 ◽  
Author(s):  
Yevgeny Gorochov ◽  
Vladimir Muschanov ◽  
Alexander Kulik ◽  
Alexander Tsyplukhin
Keyword(s):  
Large Scale ◽  
Strain State ◽  
Local Stress ◽  
Scale Model ◽  
Stress And Strain ◽  
Tank Wall ◽  
Cylindrical Tank ◽  
Geometrical Imperfection ◽  
Large Scale Model ◽  
The Ideal

In this paper the results of experimental research are given for the stress and strain state of a near seam zone. The research is executed on large‐scale model of a zone of vertical cylindrical tank assembly connection with a geometrical imperfection. As a result, the dependence is received between values of the basic stress, which take place in a tank wall of the ideal form, and local stress, which arise in a seam zone. It is proved by experiments that when the ring stress achieves value 100 mPa, then the local stress in a near seam zone achieves the stress of 280–300 mPa. Hence, they exceed three times their major importance. These stress values are coordinated satisfactorily to the data, which are received by a theoretical way.

scholarly journals Numerical and Experimental Investigation of the Mechanical Behavior of Cable-Supported Barrel Vault Structures with Varying Temperature

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Guojun Sun ◽  
Mingze Wu ◽  
Zhihua Chen ◽  
Suduo Xue
Keyword(s):  
Finite Element ◽  
Mechanical Behavior ◽  
Dynamic Characteristics ◽  
Internal Force ◽  
Scale Model ◽  
Large Temperature ◽  
String Structure ◽  
Steel Cables ◽  
Increasing Temperature ◽  
Force Displacement

The cable-supported barrel vault (CSBV) structure system is a new type of hybrid spatial steel structure based on a beam string structure (or truss string structure), suspendomes, and cylindrical lattice shells. Steel cables (e.g., steel wire rope cables, steel strand cables, semiparallel steel tendons, and steel rods) are key components of CSBV structures. However, they have different elastic moduli and thermal expansion coefficients. In this study, the roof of a textile workshop (the first CSBV structure in China) was analyzed with four types of cables under the effect of varying temperature. Under half-span loading and full-span loading, the structural internal force and displacement at varying temperatures were obtained from finite element models employing four different types of steel cables. The internal force, displacement, and horizontal arch thrust changed linearly with increasing temperature. Moreover, the dynamic characteristics of CSBV with varying temperature were analyzed. The frequency of the CSBV changed linearly with increasing temperature. Based on the dynamic characteristics of CSBV with varying temperature, a seismic response time-history analysis was performed. The variation in the maximum responses of the internal force, displacement, and horizontal arch thrust was obtained. In each case, the mechanical behavior of the CSBV with semiparallel steel tendon cables was strongly affected by the temperature. Therefore, semiparallel steel tendons are not recommended as components of CSBV in cases where large temperature changes can be expected. Thereafter, a scale model of a CSBV was designed and used for experiments and corresponding finite element analyses under varying temperature. Experimental results show that the finite element method is effective for analyzing the mechanical behavior of CSBV under varying temperature.

Large Deflection Analysis of 3D Steel Frame Using Finite Particle Method

2012 ◽  
Vol 446-449 ◽  
pp. 283-287 ◽  
Author(s):  
Ying Yu ◽  
Yao Zhi Luo
Keyword(s):  
Large Deflection ◽  
Continuous System ◽  
Particle Method ◽  
Internal Force ◽  
Beam Element ◽  
Steel Frame ◽  
Deflection Analysis ◽  
Global Equilibrium ◽  
Vector Mechanics ◽  
Finite Particle

This paper presents the large deflection analysis of 3D steel frame using the Finite Particle Method (FPM). The FPM based on the vector mechanics discretizes the analyzed domain with finite particles whose motions are described by Newton’s second law. Instead of imposing a global equilibrium of the entire continuous system, FPM enforces equilibrium on each particle. One of the features of this approach is that no iterations to follow nonlinear laws are necessary, and no global matrices are formed or solved in this method. This paper provides the fundamentals of the FPM, including the structural discretization and particle motion equation. Then internal force formulations of 3D beam element are derived using the fictitious motion method. Two typical numerical examples are given to show the capability of the FPM in the large deflection analysis of 3D steel frame.

Model Test and Numerical Simulation for Support Time of Tunnel in Loess

2011 ◽  
Vol 243-249 ◽  
pp. 3696-3700
Author(s):  
Chao Liang Ye ◽  
Yong Quan Zhu ◽  
Ben Guo He
Keyword(s):  
Model Test ◽  
High Speed ◽  
Large Scale ◽  
Internal Force ◽  
Scale Model ◽  
Underground Engineering ◽  
Passenger Rail ◽  
Rail Line ◽  
Geometric Proportion ◽  
Support Time

The work presented in this paper focuses on support time for tunnel, which has much effect on stability of tunnel. Based on loess tunnel of Zhengzhou-Xi’an high-speed passenger rail line in China, large scale model test with geometric proportion 1: 20 was applied to study on different support time. Supplemental numerical analysis was carried out to investigate the effect of release ratio of stress which cannot be covered by model test. It is revealed that it is asynchronous change for deformation, strain and stress of surround rock. If the supporting constructs prematurely, internal force of support would be excessive greatly and if the supporting constructs too late, it will bring excessive slack pressure which leads to the plastic zone unfavorable, even tunnel collapse. The reasonable support time can improve self-bearing capability of surrounding rock and reduce the cost. The limited displacements about 17.8 cm for crown and 12.9 for horizontal convergence are gained. The research results can act as reference for similar materials tunnel and underground engineering construction.

Solid Solution Effects and Deformation Micros trueture of Shock-Loaded Iron Manganese Alloys

1970 ◽  
Vol 28 ◽  
pp. 420-421
Author(s):  
A. Christou ◽  
J. V. Foltz ◽  
N. Brown
Keyword(s):  
Solid Solution ◽  
Shock Loading ◽  
High Strain ◽  
Local Stress ◽  
Strain Rates ◽  
Local Stress Concentration ◽  
Bcc Metals ◽  
Manganese Alloys ◽  
Iron Manganese ◽  
Transmission Microscope

In general, all BCC transition metals have been observed to twin under appropriate conditions. At the present time various experimental reports of solid solution effects on BCC metals have been made. Indications are that solid solution effects are important in the formation of twins. The formation of twins in metals and alloys may be explained in terms of dislocation mechanisms. It has been suggested that twins are nucleated by the achievement of local stress-concentration of the order of 15 to 45 times the applied stress. Prietner and Leslie have found that twins in BCC metals are nucleated at intersections of (110) and (112) or (112) and (112) type of planes.In this paper, observations are reported of a transmission microscope study of the iron manganese series under conditions in which twins both were and were not formed. High strain rates produced by shock loading provided the appropriate deformation conditions. The workhardening mechanisms of one alloy (Fe - 7.37 wt% Mn) were studied in detail.

The analysis of “Gels” in polymer films

1989 ◽  
Vol 47 ◽  
pp. 362-363
Author(s):  
G. M. Brown ◽  
D. F. Brown ◽  
J. H. Butler
Keyword(s):  
Molecular Weight ◽  
Film Industry ◽  
Local Stress ◽  
Melt Index ◽  
Polyethylene Films ◽  
Crosslinked Polymer ◽  
Polymeric Gels ◽  
Mineral Particles ◽  
Polymeric Species ◽  
Special Concern

The term “gel”, in the jargon of the plastics film industry, may refer to any inclusion that produces a visible artifact in a polymeric film. Although they can occur in any plastic product, gels are a principle concern in films where they detract from the cosmetic appearance of the product and may compromise its mechanical strength by acting as local stress concentrators. Many film gels are small spheres or ellipsoids less than one millimeter in diameter whereas other gels are fusiform-shaped and may reach several centimeters in length. The actual composition of gel inclusions may vary from miscellaneous inorganics (i.e. glass and mineral particles) and processing additives to heavily oxidized, charred or crosslinked polymer. The most commonly observed gels contain polymer differing from the bulk of the sample in its melt viscosity, density or molecular weight.Polymeric gels are a special concern in polyethylene films. Over the years and with the examination of a variety of these samples three predominant polymeric species have been observed: density gels which have different crystallinity than the film; melt-index gels in which the molecular weight is different than the film and crosslinked gels which are comprised of crosslinked polyethylene.

The Role of the SLP in Autism Spectrum Disorder Screening and Assessment

2008 ◽  
Vol 15 (2) ◽  
pp. 50-59 ◽  
Author(s):  
Amy Philofsky
Keyword(s):  
Language Development ◽  
Critical Role ◽  
Children With Autism ◽  
Autism Spectrum ◽  
Children With Asd ◽  
Prevalence Estimates ◽  
Notable Increase ◽  
Screening Assessment ◽  
Critical Components

AbstractRecent prevalence estimates for autism have been alarming as a function of the notable increase. Speech-language pathologists play a critical role in screening, assessment and intervention for children with autism. This article reviews signs that may be indicative of autism at different stages of language development, and discusses the importance of several psychometric properties—sensitivity and specificity—in utilizing screening measures for children with autism. Critical components of assessment for children with autism are reviewed. This article concludes with examples of intervention targets for children with ASD at various levels of language development.

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