Multiaxial Testing of Materials Using a Stewart Platform: Case Study of the Nooru-Mohamed Test

2012 ◽  
Vol 38 (2) ◽  
pp. 74-83 ◽  
Author(s):  
M. Nierenberger ◽  
M. Poncelet ◽  
S. Pattofatto ◽  
A. Hamouche ◽  
B. Raka ◽  
...  
Keyword(s):  
Stewart Platform ◽  
Multiaxial Testing

A Low-Cost Stewart Platform for a Radio Telescope

2013 ◽  
Vol 300-301 ◽  
pp. 362-370 ◽  
Author(s):  
Frank Janse van Vuuren ◽  
Yoon Soo Kim ◽  
Kristiaan Schreve
Keyword(s):  
Dynamic Models ◽  
Low Cost ◽  
Stewart Platform ◽  
Viewing Angle ◽  
Radio Telescopes ◽  
Positional Accuracy ◽  
Design Decisions ◽  
Simulation Results ◽  
Electronic Controller

Most hexapods that are currently available on the market are expensive and have extremely high positional and orientation accuracies. Although the positional accuracy is high the viewing angle is limited to 60°. These hexapods are designed with a small viewing angle, as they are not optimised for radio telescopes. The aim of this work is to highlight the various factors that should be considered during the design of a 6-3 Stewart platform for pointing applications. These factors are illustrated by presenting the case study of a small custom hexapod that is designed, built and tested. Modelling of the Platform is performed through the implementation of existing kinematic and dynamic models that could be verified through comparison to simulation results in literature. Components designed for the hexapod include the linear drives, base joints, platform joints, electronic controller and graphical user interface. The design process is documented and design decisions clearly motivated. Performance of the Stewart platform is measured with an inclinometer and the ability of the platform to track a sun simulation path is presented. Specifications which the hexapod is able to achieve include a viewing angle of 120˚±0.3˚ and the ability to carry a payload of 1kg.

A case study of yacht’s motions represented by using stewart platform

2008 ◽  
Author(s):  
Yu Kerwei ◽  
Yang Tsunlirng ◽  
Zheng Yujie
Keyword(s):  
Stewart Platform

Determination of the Actual Configuration of the General Stewart Platform Using Only One Additional Sensor

1999 ◽  
Vol 121 (1) ◽  
pp. 21-25 ◽  
Author(s):  
V. Parenti-Castelli ◽  
R. Di Gregorio
Keyword(s):  
Stewart Platform ◽  
Rigid Bodies ◽  
Displacement Sensor ◽  
Leg Length ◽  
Displacement Sensors ◽  
On Line ◽  
Actual Configuration ◽  
General Geometry

This paper presents a procedure for the determination of the actual configuration of the general geometry Stewart platform (GSP), a fully-parallel manipulator that features two rigid bodies connected to each other via spherical pairs by six controlled-length legs. The six leg length measurements, provided by the displacement sensors incorporated in the leg hardware equipment, do not make it possible to uniquely find the GSP configuration because several configurations are possible for a given set of leg lengths. Several extra sensors in addition to those incorporated in the leg equipment have been proposed in the literature in order to obtain a one-to-one correspondence between the measurements and the actual GSP configuration. The proposed procedure makes use of only one additional displacement sensor and relies upon the analytical results available in the literature for a particular type of Stewart platform. The procedure, which uniquely defines the actual configuration of the GSP, is not intended for on-line implementation. Three different algorithms are proposed for computation and their efficiency compared. A case study is reported that confirms the effectiveness of the procedure.

The Genesis and Internal Dynamics of El Salvador's People's Revolutionary Army, 1970–1976

2014 ◽  
Vol 38 (01) ◽  
pp. 102-129
Author(s):  
ALBERTO MARTÍN ÁLVAREZ ◽  
EUDALD CORTINA ORERO
Keyword(s):  
Latin America ◽  
El Salvador ◽  
Early Years ◽  
Left Wing ◽  
Internal Dynamics ◽  
Internal Coherence ◽  
The 1960S

AbstractUsing interviews with former militants and previously unpublished documents, this article traces the genesis and internal dynamics of the Ejército Revolucionario del Pueblo (People's Revolutionary Army, ERP) in El Salvador during the early years of its existence (1970–6). This period was marked by the inability of the ERP to maintain internal coherence or any consensus on revolutionary strategy, which led to a series of splits and internal fights over control of the organisation. The evidence marshalled in this case study sheds new light on the origins of the armed Salvadorean Left and thus contributes to a wider understanding of the processes of formation and internal dynamics of armed left-wing groups that emerged from the 1960s onwards in Latin America.

Culture and the plasticity of perception

2020 ◽  
Vol 43 ◽  
Author(s):  
Michael Lifshitz ◽  
T. M. Luhrmann
Keyword(s):  
Cultural Context ◽  
Sensory Experience ◽  
Cultural Learning ◽  
The World

Abstract Culture shapes our basic sensory experience of the world. This is particularly striking in the study of religion and psychosis, where we and others have shown that cultural context determines both the structure and content of hallucination-like events. The cultural shaping of hallucinations may provide a rich case-study for linking cultural learning with emerging prediction-based models of perception.

Dual systems for all: Higher-order, role-based relational reasoning as a uniquely derived feature of human cognition

2019 ◽  
Vol 42 ◽  
Author(s):  
Daniel J. Povinelli ◽  
Gabrielle C. Glorioso ◽  
Shannon L. Kuznar ◽  
Mateja Pavlic
Keyword(s):  
Temporal Reasoning ◽  
Higher Order ◽  
Important Case ◽  
Human Cognition ◽  
Relational Reasoning ◽  
Dual Systems ◽  
First Order ◽  
Reasoning System ◽  
Role Based

Abstract Hoerl and McCormack demonstrate that although animals possess a sophisticated temporal updating system, there is no evidence that they also possess a temporal reasoning system. This important case study is directly related to the broader claim that although animals are manifestly capable of first-order (perceptually-based) relational reasoning, they lack the capacity for higher-order, role-based relational reasoning. We argue this distinction applies to all domains of cognition.

Sociocultural memory development research drives new directions in gadgetry science

2019 ◽  
Vol 42 ◽  
Author(s):  
Penny Van Bergen ◽  
John Sutton
Keyword(s):  
Episodic Memory ◽  
Autobiographical Memory ◽  
Developmental Psychology ◽  
Cross Cultural ◽  
Memory Development ◽  
Development Research ◽  
Cultural Research ◽  
New Directions ◽  
Cross Cultural Research

Abstract Sociocultural developmental psychology can drive new directions in gadgetry science. We use autobiographical memory, a compound capacity incorporating episodic memory, as a case study. Autobiographical memory emerges late in development, supported by interactions with parents. Intervention research highlights the causal influence of these interactions, whereas cross-cultural research demonstrates culturally determined diversity. Different patterns of inheritance are discussed.

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

1996 ◽  
Vol 54 ◽  
pp. 636-637
Author(s):  
D. L. Callahan
Keyword(s):  
Plastic Deformation ◽  
Aluminum Nitride ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Bright Field Image ◽  
Perfectly Plastic ◽  
Contrast Analysis ◽  
Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

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