Reliable and Failure-Free Workspaces for Motion Planning Algorithms for Parallel Manipulators Under Geometrical Uncertainties

2019 ◽  
Vol 14 (2) ◽  
Author(s):  
Hiparco L. Vieira ◽  
João V. C. Fontes ◽  
André T. Beck ◽  
Maíra M. da Silva
Keyword(s):  
Motion Planning ◽  
Parallel Manipulators ◽  
Monte Carlo Algorithm ◽  
Planning Algorithm ◽  
Dense Grid ◽  
Planning Strategies ◽  
Singular Configuration ◽  
The One ◽  
Failure Probabilities

Manufacturing tolerances and other uncertainties may play an important role in the performance of parallel manipulators since they can affect the distance to a singular configuration. Motion planning strategies for parallel manipulators under uncertainty require decision making approaches for classifying reliable regions within the workspace. In this paper, we address fail free and reliable motion planning for parallel manipulators. Failure is related to parallel kinematic singularities in the motion equations or to ill-conditioning of the Jacobian matrices. Monte Carlo algorithm is employed to compute failure probabilities for a dense grid of manipulator workspace configurations. The inverse condition number of the Jacobian matrix is used to compute the distance between each configuration and a singularity. For supporting motion planning strategies, not only failure maps are constructed but also reliable and failure-free workspaces are obtained. On the one hand, the reliable workspace is obtained by minimizing the failure probabilities subject to a minimal workspace area. Differently, a failure-free workspace is found by maximizing the workspace area subject to a probability of failure equal to zero. A 3RRR manipulator is used as a case study. For this case study, the usage of the reliable strategy can be useful for robustifying motion planning algorithm without a significant reduction of the reliable regions within the workspace.

scholarly journals Motion Planning of a Second-Order Nonholonomic Chained Form System Based on Holonomy Extraction

Electronics ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1337
Author(s):  
Masahide Ito
Keyword(s):  
Motion Planning ◽  
Nonholonomic Systems ◽  
Second Order ◽  
Literature Survey ◽  
First Order ◽  
Underactuated Manipulator ◽  
Planning Algorithm ◽  
The One ◽  
Specific Control ◽  
Form System

This paper proposes a motion planning algorithm for dynamic nonholonomic systems represented in a second-order chained form. The proposed approach focuses on the so-called holonomy resulting from a kind of motion that traverses a closed path in a reduced configuration space of the system. According to the author’s literature survey, control approaches that make explicit use of holonomy exist for kinematic nonholonomic systems but does not exist for dynamic nonholonomic systems. However, the second-order chained form system is controllable. Also, the structure of the second-order chained form system analogizes with the one of the first-order chained form for kinematic nonholonomic systems. These survey and perspectives brought a hypothesis that there exists a specific control strategy for extracting holonomy of the second-order chained form system to the author. To verify this hypothesis, this paper shows that the holonomy of the second-order chained form system can be extracted by combining two appropriate pairs of sinusoidal inputs. Then, based on such holonomy extraction, a motion planning algorithm is constructed. Furthermore, the effectiveness is demonstrated through some simulations including an application to an underactuated manipulator.

A CASE STUDY OF NL INFLUENCE IN UNIS FKIP ENGLISH DEPARTMENT STUDENTS' INTERLANGUAGE

2018 ◽  
Vol 18 (1) ◽  
pp. 46-54
Author(s):  
Irmala Sukendra ◽  
Agus Mulyana ◽  
Imam Sudarmaji
Keyword(s):  
Second Language ◽  
Second Language Acquisition ◽  
Native Speakers ◽  
Communicative Competence ◽  
Mother Tongue ◽  
Universal Grammar ◽  
Similar System ◽  
The One ◽  
L1 Acquisition

Regardless to the facts that English is being taught to Indonesian students starting from early age, many Indonesian thrive in learning English. They find it quite troublesome for some to acquire the language especially to the level of communicative competence. Although Krashen (1982:10) states that “language acquirers are not usually aware of the fact that they are acquiring language, but are only aware of the fact that they are using the language for communication”, second language acquisition has several obstacles for learners to face and yet the successfulness of mastering the language never surmounts to the one of the native speakers. Learners have never been able to acquire the language as any native speakers do. Mistakes are made and inter-language is unavoidable. McNeili in Ellis (1985, p. 44) mentions that “the mentalist views of L1 acquisition hypothesizes the process of acquisition consists of hypothesis-testing, by which means the grammar of the learner’s mother tongue is related to the principles of the ‘universal grammar’.” Thus this study intends to find out whether the students go through the phase of interlanguage in their attempt to acquire second language and whether their interlanguage forms similar system as postulated by linguists (Krashen).

Interrelationships between municipal spatial policy strategy and airport operation and development. Lodz Airport case study

2018 ◽  
Vol 59 (1) ◽  
pp. 65-79
Author(s):  
Katarzyna Nikorowicz-Zatorska
Keyword(s):  
Land Use ◽  
Urban Planning ◽  
Cultural Development ◽  
The Other ◽  
Local Authorities ◽  
Spatial Management ◽  
The One ◽  
Surrounding Areas

Abstract The present paper focuses on spatial management regulations in order to carry out investment in the field of airport facilities. The construction, upgrades, and maintenance of airports falls within the area of responsibility of local authorities. This task poses a great challenge in terms of organisation and finances. On the one hand, an active airport is a municipal landmark and drives local economic, social and cultural development, and on the other, the scale of investment often exceeds the capabilities of local authorities. The immediate environment of the airport determines its final use and prosperity. The objective of the paper is to review legislation that affects airports and the surrounding communities. The process of urban planning in Lodz and surrounding areas will be presented as a background to the problem of land use management in the vicinity of the airport. This paper seeks to address the following questions: if and how airports have affected urban planning in Lodz, does the land use around the airport prevent the development of Lodz Airport, and how has the situation changed over the time? It can be assumed that as a result of lack of experience, land resources and size of investments on one hand and legislative dissonance and peculiar practices on the other, aviation infrastructure in Lodz is designed to meet temporary needs and is characterised by achieving short-term goals. Cyclical problems are solved in an intermittent manner and involve all the municipal resources, so there’s little left to secure long-term investments.

De la gestión local a la gobernanza global: actores e interacciones multiniveles en la gestión del agua en la ciudad de México

2011 ◽  
Vol 1 (3) ◽  
pp. 34-66
Author(s):  
Joyce Valdovinos
Keyword(s):  
Private Sector ◽  
Water Governance ◽  
The State ◽  
Public Authorities ◽  
Service Contracts ◽  
Governance Model ◽  
Role Of The State ◽  
The One

The provision of water services has traditionally been considered a responsibility of the state. During the late 1980s, the private sector emerged as a key actor in the provision of public services. Mexico City was no exception to this trend and public authorities awarded service contracts to four private consortia in 1993. Through consideration of this case study, two main questions arise: First, why do public authorities establish partnerships with the private sector? Second, what are the implications of these partnerships for water governance? This article focuses, on the one hand, on the conceptual debate of water as a public and/or private good, while identifying new trends and strategies carried out by private operators. On the other hand, it analyzes the role of the state and its relationships with other actors through a governance model characterized by partnerships and multilevel networks.Spanish La provisión del servicio del agua ha sido tradicionalmente considerada como una responsabilidad del Estado. A finales de la década de 1980, el sector privado emerge como un actor clave en el suministro de servicios públicos. La ciudad de México no escapa a esta tendencia y en 1993 las autoridades públicas firman contratos de servicios con cuatro consorcios privados. A través de este estudio de caso, dos preguntas son planteadas: ¿Por qué las autoridades públicas establecen partenariados con el sector privado? ¿Cuáles son las implicaciones de dichos partenariados en la gobernanza del agua? Este artículo aborda por una parte, el debate conceptual del agua como bien público y/o privado, identificando nuevas tendencias y estrategias de los operadores privados. Por otra parte, se analizan el rol y las relaciones del Estado con otros actores a través de un modelo de gobernanza, definido en términos de partenariados y redes multi-niveles.French Les services de l'eau ont été traditionnellement considérés comme une responsabilité de l'État. À la fin des années 1980, le secteur privé est apparu comme un acteur clé dans la fourniture de certains services publics. La ville de Mexico n'a pas échappé à cette tendance et en 1993, les autorités publiques ont signé des contrats de services avec quatre consortiums privés. À travers cette étude de cas, nous nous interrogerons sur deux aspects : pourquoi les autorités publiques établissentelles des partenariats avec le secteur privé ? Quelles sont les implications de ces partenariats sur la gouvernance de l'eau ? Cet article s'intéresse, d'une part, au débat conceptuel sur l'eau en tant que bien public et/ou privé, en identifiant les tendances nouvelles et les stratégies menées par les opérateurs privés. D'autre part y sont analysés le rôle de l'État et ses relations avec d'autres acteurs à travers un modèle de gouvernance, défini en termes de partenariats, et des réseaux multi-niveaux.

Paranasal Sinus Mucocele Clinical, imagistic and biochemical aspects

2018 ◽  
Vol 69 (8) ◽  
Author(s):  
Doina Vesa ◽  
Cristian Martu ◽  
Razvan Leata ◽  
Ludmila Lozneanu ◽  
luminita Radulescu ◽  
...  
Keyword(s):  
Facial Asymmetry ◽  
Retrospective Case ◽  
Mri Scans ◽  
The One ◽  
Ethmoid Sinuses ◽  
Retrospective Case Study ◽  
Cellular Components ◽  
Ct And Mri

Paranasal mucoceles are a type of cysts that evolve slowly and are asymptomatic; this poses a difficulty in diagnosing the patient because the symptoms can go unnoticed. The mucocele evolves unpredictably. On the one hand, it can become infected turning into pyoceles and on the other hand, it can invade important regions such as the orbital, cranial or genian regions, creating facial asymmetry. This is a retrospective case study of 37 patients diagnosed with sinus mucoceles, followed up by clinical examination and paraclinical tests such as CT and MRI scans. The biochemical components of the liquid from within the mucocele were analyzed and the following criteria were recorded: NaCl-, Cl-, Na+ and cholesterine as well as cellular components such as mastocytes, macrophages, hematocytes and leucocytes. In all cases, the treatment option was surgery with favorable post-operative and follow-up evaluation. The mucoceles that appeared post-operatively (maxillary and ethmoid sinuses) evolved more rapidly than the mucoceles that were induced byan external injury. Longer follow-up of operated patients permitted a more timely diagnosis of recurrences.

scholarly journals A new method on motion planning for mobile robots using jump point search and Bezier curves

2021 ◽  
Vol 18 (4) ◽  
pp. 172988142110192
Author(s):  
Ben Zhang ◽  
Denglin Zhu
Keyword(s):  
Motion Planning ◽  
Initial Point ◽  
Target Point ◽  
Jump Point ◽  
Bezier Curves ◽  
Bézier Curves ◽  
Front End ◽  
Planning Algorithm ◽  
Point Search ◽  
Path Planning Algorithm

Innovative applications in rapidly evolving domains such as robotic navigation and autonomous (driverless) vehicles rely on motion planning systems that meet the shortest path and obstacle avoidance requirements. This article proposes a novel path planning algorithm based on jump point search and Bezier curves. The proposed algorithm consists of two main steps. In the front end, the improved heuristic function based on distance and direction is used to reduce the cost, and the redundant turning points are trimmed. In the back end, a novel trajectory generation method based on Bezier curves and a straight line is proposed. Our experimental results indicate that the proposed algorithm provides a complete motion planning solution from the front end to the back end, which can realize an optimal trajectory from the initial point to the target point used for robot navigation.

Freedom of speech is not freedom from ethics: the 2019 Israel Folau media controversy as a case study

2021 ◽  
pp. 1329878X2199289
Author(s):  
Jay Daniel Thompson ◽  
Denis Muller
Keyword(s):  
Content Analysis ◽  
Freedom Of Speech ◽  
Rugby Player ◽  
Ethical Principles ◽  
Framing Analysis ◽  
The Media ◽  
The One

This article examines how freedom of speech is framed in the media controversy surrounding the Australian rugby player Israel Folau’s April 2019 Instagram post. A content analysis and framing analysis of newspaper reportage reveals that the controversy has been largely discussed in terms of whether or not Folau’s speech was being curtailed and whether this curtailing indicates a broader, ideologically motivated censoriousness. This discussion is problematic in that it says little about the actual substance of Folau’s post. This article argues that debates surrounding freedom of speech such as the one involving Folau could and should be enriched by an engagement with ethical principles. This engagement is premised on a commitment to the free exchange of views, while acknowledging that ‘speech’ is not always inherently beneficial for democracy, nor worth defending.

Sign in / Sign up

Export Citation Format

Share Document