Error Analysis of a 3-DOF Parallel Mechanism for Milling Applications

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
G. E. E. Gojtan ◽  
G. P. Furtado ◽  
T. A. Hess-Coelho
Keyword(s):  
Error Analysis ◽  
Parallel Mechanism ◽  
The Other ◽  
Kinematic Structure ◽  
Positioning Error ◽  
Parallel Mechanisms ◽  
Tool Positioning ◽  
The Third ◽  
Orthogonality Conditions ◽  
Manufacturing Tolerances

Parallel mechanisms have been investigated during the last two decades, due to the fact that they present some advantages in a comparison with serial structures. This work deals with the error analysis of a 3-dof asymmetric parallel mechanism, purposely conceived for milling applications. In a comparison with the previous proposed concepts, this type of kinematic structure demonstrates a promising behavior. Topologically, the architecture is simpler and lighter than Tricept because it has no central passive limb. In addition, only the constraining active limb needs to satisfy the parallelism and orthogonality conditions. Furthermore, one degree of freedom, associated to the third actuator, is decoupled from the other two. Important issues, related to this type of kinematic structure, such as the mappings of the tool positioning error throughout the available workspace, due to the actuators imprecisions and manufacturing tolerances, are discussed in detail.

The Parallel Mechanism and Variable Acceleration Control Method

2013 ◽  
Vol 579-580 ◽  
pp. 659-664
Author(s):  
Xiang Bo Ouyang ◽  
Ke Tian Li ◽  
Hong Jian Xia ◽  
Su Juan Wang ◽  
Huan Wei Zhou ◽  
...  
Keyword(s):  
Parallel Mechanism ◽  
Control Method ◽  
The Other ◽  
Connecting Rod ◽  
Motion Platform ◽  
The Third ◽  
Symmetric Structure ◽  
Slide Block ◽  
Operation Process ◽  
Moving Platform

t presents the parallel mechanism and variable acceleration control method, which is composed of slider, connecting rod, moving platform and linear guide etc. The motion platform is supported by three connecting rods through hinging, the other end of the connecting rods are respectively hinged with two sliders. Among them two pairs of connecting rod, two sliders and the moving platform formed a symmetric structure that is the so called Parallel Mechanism. The third connecting rod is parallel to one of two connecting rods, so that the two parallel connecting rods, slide block and the moving platform formed a parallelogram structure, it makes that the moving platform is always parallel to liner guiderail in the process of movement. By controlling the two sliders moving in the way of variable acceleration, it can make the trajectory curve, speed curve and acceleration curve of the moving platform are continuous, smooth, so impact and vibration of the moving platform is limited in the operation process.

scholarly journals Reconfiguration Analysis of a 3-DOF Parallel Mechanism

Robotics ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 66
Author(s):  
Maurizio Ruggiu ◽  
Xianwen Kong
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Operation Mode ◽  
Parallel Mechanisms ◽  
Universal Joint ◽  
Kinematic Chains ◽  
Constraint Equations ◽  
The Third ◽  
Equilateral Triangles ◽  
Moving Platform

This paper deals with the reconfiguration analysis of a 3-DOF (degrees-of-freedom) parallel manipulator (PM) which belongs to the cylindrical parallel mechanisms family. The PM is composed of a base and a moving platform shaped as equilateral triangles connected by three serial kinematic chains (legs). Two legs are composed of two universal (U) joints connected by a prismatic (P) joint. The third leg is composed of a revolute (R) joint connected to the base, a prismatic joint and universal joint in sequence. A set of constraint equations of the 1-RPU−2-UPU PM is derived and solved in terms of the Euler parameter quaternion (a.k.a. Euler-Rodrigues quaternion) representing the orientation of the moving platform and of the Cartesian coordinates of the reference point on the moving platform. It is found that the PM may undergo either the 3-DOF PPR or the 3-DOF planar operation mode only when the base and the moving platform are identical. The transition configuration between the operation modes is also identified.

Positive Analysis of a New Type of Planar 3-DOF Parallel Mechanisms

2012 ◽  
Vol 522 ◽  
pp. 659-662
Author(s):  
Zhao Xin Meng ◽  
Xiao Gang Lei ◽  
Chao Mei Zhang
Keyword(s):  
Mathematical Model ◽  
Error Analysis ◽  
Positive Solution ◽  
Parallel Mechanism ◽  
Control Algorithm ◽  
Movement Analysis ◽  
Parallel Mechanisms ◽  
New Type ◽  
And Control ◽  
Polygon Method

The planar 3-DOF parallel mechanism was developed as a part of the pushing device for the wood sawing. Using closed vector polygon method to make positive movement analysis of the mechanism, establish the positive solution mathematical model. It provided the theory bases for the error analysis and control algorithm of the planar 3-DOF parallel mechanism.

Active Compliant Parallel Mechanisms

2014 ◽  
Author(s):  
Matthew Holgate ◽  
Thomas G. Sugar
Keyword(s):  
Parallel Mechanism ◽  
Gear Ratio ◽  
Parallel Mechanisms ◽  
Output Link ◽  
End Effector ◽  
Attachment Point ◽  
The Third ◽  
Output Torque ◽  
Compliant Parallel Mechanism ◽  
Parallel Fashion

In a novel compliant parallel mechanism, a motor and spring are arranged in a parallel fashion and are connected to a movable lever arm. The motor pushes and pulls on one attachment point and the spring stores and releases energy at a second attachment point. In a non-obvious choice, we do not attach the output link to the commonly thought of end-effector, but to the third link in the planar, parallel mechanism. The new mechanism allows the transmission ratio of the motor to be a function of the output angle and the force applied at the spring. For example, if there are no loads on the spring, the overall gear ratio is lowered, and the output speed can be increased. Conversely, if there are loads on the spring, the overall gear ratio is increased, and the output torque can be increased.

Realization of a Planar Stiffness With a Simple Symmetric Parallel Mechanism

2010 ◽  
Author(s):  
Shuguang Huang ◽  
Joseph M. Schimmels
Keyword(s):  
Stiffness Matrix ◽  
Parallel Mechanism ◽  
The Other ◽  
New Method ◽  
Parallel Mechanisms ◽  
Compliant Behavior ◽  
Elastic Mechanism ◽  
Symmetric Geometry ◽  
Synthesis Procedure

This paper presents a new method for the realization of a planar compliant behavior with an elastic mechanism. The mechanisms considered are parallel mechanisms with symmetric geometry. We show that any planar stiffness matrix can be realized using a parallel mechanism with four line springs connected symmetrically. Among the four springs, two are identical parallel springs equidistant from the stiffness center, and the other two identical springs intersect at the stiffness center. A synthesis procedure is presented.

Efficacy of some insecticide modules against major insect pests and spider population of rice, Oryza sativa L.

ENTOMON ◽  
2018 ◽  
Vol 43 (4) ◽  
pp. 257-262
Author(s):  
Atanu Seni ◽  
Bhimasen Naik
Keyword(s):  
Oryza Sativa ◽  
Grain Yield ◽  
Untreated Control ◽  
Insect Pests ◽  
Oryza Sativa L ◽  
Gall Midge ◽  
Stem Borer ◽  
The Other ◽  
The Third ◽  
Treated Plot

Experiments were carried out to assess some insecticide modules against major insect pests of rice. Each module consists of a basal application of carbofuran 3G @ 1 kg a.i ha-1 at 20 DAT and Rynaxypyr 20 SC @ 30 g a.i ha-1 at 45 DAT except untreated control. All modules differ with each other only in third treatment which was applied in 65 DAT. The third treatment includes: Imidacloprid 17.8 SL @ 27 g a.i ha-1, Pymetrozine 50 WG @ 150 g a.i ha-1, Triflumezopyrim 106 SC @ 27 g a.i ha-1, Buprofezin 25 SC @ 250 g a.i ha-1; Glamore (Imidacloprid 40+Ethiprole 40% w/w) 80 WG @ 100 g a.i. ha-1, Thiacloprid 24 SC @ 60 g a.i ha-1, Azadirachtin 0.03 EC @ 8 g a.i ha-1, Dinotefuran 20 SG@ 40 g a.i ha-1 and untreated control. All the treated plots recorded significantly lower percent of dead heart, white ear- head caused by stem borer and silver shoot caused by gall midge. Module with Pymetrozine 50 WG @ 150 g a.i ha-1 treated plot recorded significantly higher per cent reduction of plant hoppers (>80% over untreated control) and produced higher grain yield (50.75 qha-1) than the other modules. Among the different treated modules the maximum number of spiders was found in Azadirachtin 0.03 EC @ 8 g a.i ha-1 treated module plot followed by other treatments.

An Error Analysis of Hiragana and Katakana Writing Systems in the Learning of Japanese as Third Language at UiTM

2020 ◽  
Vol 4 (3) ◽  
pp. 46
Author(s):  
Norhazlina Husin ◽  
Nuranisah Tan Abdullah ◽  
Aini Aziz
Keyword(s):  
Error Analysis ◽  
Foreign Students ◽  
Teaching And Learning ◽  
Language Skills ◽  
The Other ◽  
Japanese Language ◽  
Writing System ◽  
Writing Systems ◽  
Third Language ◽  
Main Challenge

Abstract The teaching of Japanese language as third language to foreign students has its own issues and challenges. It does not merely involve only teaching the four language skills. Japanese language has its own unique values. These unique values also tend to differentiate the teaching of Japanese language as a third language from other third language acquisitions. The teaching of Japanese language as third language to foreign students also involves the teaching of its writing system. This makes the teaching of Japanese language rather complicated because Japanese language has three forms of writings, namely: Hiragana, Katakana and Kanji. Students are required to fully understand the Hiragana system of writing first before proceeding to learn the other two forms of writings. The main challenge in the teaching of Japanese writing systems is the time allocated that can be considered as very limited as other language aspects need to be taught too. This, which relates directly to students’ factor very much contribute to the challenges foreseen. Students are likely to face problems in understanding and using the writings as they simultaneously need to adhere to the findings teaching and learning schedules. This article discusses on the analysis conducted in terms of the learning of the Hiragana and Katagana systems of writing among foreign students. The discussion in this article is based on the teaching of Japanese language to students of Universiti Teknologi MARA(UiTM), Shah Alam. Keywords: Third language, Hiragana, Katakana, Kanji

Retroaktive Neuverhandlung

2018 ◽  
Vol 63 (1) ◽  
Author(s):  
Daniel Martin Feige
Keyword(s):  
Original Work ◽  
The Other ◽  
Final Part ◽  
Critical Reading ◽  
The Third ◽  
Works Of Art ◽  
The Relationship

Der Beitrag widmet sich der Frage historischer Folgeverhältnisse in der Kunst. Gegenüber dem Gedanken, dass es ein ursprüngliches Werk in der Reihe von Werken gibt, das späteren Werken seinen Sinn gibt, schlägt der Text vor, das Verhältnis umgekehrt zu denken: Im Lichte späterer Werke wird der Sinn früherer Werke neu ausgehandelt. Dazu geht der Text in drei Schritten vor. Im ersten Teil formuliert er unter der Überschrift ›Form‹ in kritischer Abgrenzung zu Danto und Eco mit Adorno den Gedanken, dass Kunstwerke eigensinnig konstituierte Gegenstände sind. Die im Gedanken der Neuverhandlung früherer Werke im Lichte späterer Werke vorausgesetzte Unbestimmtheit des Sinns von Kunstwerken wird im zweiten Teil unter dem Schlagwort ›Zeitlichkeit‹ anhand des Paradigmas der Improvisation erörtert. Der dritte und letzte Teil wendet diese improvisatorische Logik unter dem Label ›Neuaushandlung‹ dann dezidiert auf das Verhältnis von Vorbild und Nachbild an. The article proposes a new understanding of historical succession in the realm of art. In contrast to the idea that there is an original work in the series of works that gives meaning to the works that come later, the text proposes to think it exactly the other way round: in the light of later works, the meanings of earlier works are renegotiated. The text proceeds in three steps to develop this idea. Under the heading ›Form‹ it develops in the first part a critical reading of Danto’s and Eco’s notion of the constitution of the artworks and argues with Adorno that each powerful work develops its own language. In the second part, the vagueness of the meaning of works of art presupposed in the idea of renegotiating earlier works in the light of later works is discussed under the term ›Temporality‹ in terms of the logic of improvisation. The third and final part uses this improvisational logic under the label ›Renegotiation‹ to understand the relationship between model and afterimage in the realm of art.

Features of the course and treatment of glaucoma during pregnancy

2020 ◽  
Vol 98 (3) ◽  
pp. 178-184
Author(s):  
T. V. Chernyakova ◽  
A. Yu. Brezhnev ◽  
I. R. Gazizova ◽  
A. V. Kuroyedov ◽  
A. V. Seleznev
Keyword(s):  
Pregnant Women ◽  
Laser Treatment ◽  
Progressive Disease ◽  
Clinical Course ◽  
The Other ◽  
Third Trimester ◽  
The Third ◽  
Chronic Progressive Disease ◽  
Hypotensive Therapy ◽  
Eye Pressure

In the review we have integrated all up-to-date knowledge concerning clinical course and treatment of glaucoma among pregnant women to help specialists choose a proper policy of treatment for such a complicated group of patients. Glaucoma is a chronic progressive disease. It rarely occurs among childbearing aged women. Nevertheless the probability to manage pregnant patients having glaucoma has been recently increasing. The situation is complicated by the fact that there are no recommendations on how to treat glaucoma among pregnant women. As we know, eye pressure is progressively going down from the first to the third trimester, so we often have to correct hypotensive therapy. Besides, it is necessary to take into account the effect of applied medicines on mother health and evaluate possible teratogenic complications for a fetus. The only medicine against glaucoma which belongs to category B according to FDA classification is brimonidine. Medicines of the other groups should be prescribed with care. Laser treatment or surgery may also be a relevant decision when monitoring patients who are planning pregnancy or just bearing a child. Such treatment should be also accompanied by medicines.

The Nile Delta during the Early Dynastic and Old Kingdom periods. Preliminary remarks on the evolution of settlement landscape

2020 ◽  
pp. 13-61
Author(s):  
Natalia Małecka-Drozd
Keyword(s):  
Nile Delta ◽  
Ancient Egypt ◽  
The Other ◽  
Old Kingdom ◽  
The Third ◽  
Other Hand ◽  
Early Dynastic ◽  
Territorial Structure ◽  
Settlement Landscape ◽  
New Settlements

The 3rd millennium BC appears to be a key period of development of the historical settlement landscape in ancient Egypt. After the unification of the country, the process of disappearance of the predynastic socio-political structures and settlement patterns associated with them significantly accelerated. Old chiefdoms, along with their centres and elites, declined and vanished. On the other hand, new settlements emerging in various parts of the country were often strictly related to the central authorities and formation of the new territorial administration. Not negligible were climatic changes, which influenced the shifting of the ecumene. Although these changes were evolutionary in their nature, some important stages may be recognized. According to data obtained during surveys and excavations, there are a number of sites that were considerably impoverished and/or abandoned before and at the beginning of the Old Kingdom. On the other hand, during the Third and Fourth Dynasties some important Egyptian settlements have emerged in the sources and begun their prosperity. Architectural remains as well as written sources indicate the growing interest of the state in the hierarchy of landscape elements and territorial structure of the country.

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