388 research outputs found
Improving incremental encoder measurement: variable acquisition window and quadrature phase compensation to minimize acquisition errors
Motion control is an important task in several areas, such as robotics where the angular position and speed should be acquired, usually with encoders. For slow angular speeds, an error is introduced spoiling the measurement. In this paper there will be proposed two new methodologies, that when combined allow to increase the precision whereas reducing the error, even on transient velocities. The two methodologies Variable Acquisition Window and a Quadrature Phase Compensation are addressed and combined simultaneously. A real implementation of the proposed algorithms is performed on a real hardware, with a DC motor and a low resolution encoder based on hall effect. The results validate the proposed approach since the errors are reduced compared with the standard Quadrature Encoder Reading.This work has been supported by FCT - Fundac¸ao˜
para a Ciencia e Tecnologia within the Project Scope: ˆ
UIDB/05757/2020info:eu-repo/semantics/publishedVersio
Indoor Localization System based on Artificial Landmarks and Monocular Vision
This paper presents a visual localization approach that is suitable for domestic and industrial environments as it enables accurate, reliable and robust pose estimation. The mobile robot is equipped with a single camera which update sits pose whenever a landmark is available on the field of view. The innovation presented by this research focuses on the artificial landmark system which has the ability to detect the presence of the robot, since both entities communicate with each other using an infrared signal protocol modulated in frequency. Besides this communication capability, each landmark has several high intensity light-emitting diodes (LEDs) that shine only for some instances according to the communication, which makes it possible for the camera shutter and the blinking of the LEDs to synchronize. This synchronization increases the system tolerance concerning changes in brightness in the ambient lights over time, independently of the landmarks location. Therefore, the environment’s ceiling is populated with several landmarks and an Extended Kalman Filter is used to combine the dead-reckoning and landmark information. This increases the flexibility of the system by reducing the number of landmarks required. The experimental evaluation was conducted in a real indoor environment with an autonomous wheelchair prototype
RANS-VOF modelling of the hydraulic performance of the LOWREB caisson
The LOWREB caisson is an innovative multi-chambered, low-reflection structure that incorporates inner weirs at each dissipative chamber to promote wave energy dissipation. It was designed to be applied either as external caisson breakwater or as low reflection quay-wall. In this paper, the OpenFOAM® CFD numerical package was used to implement a RANS-VOF numerical model of the LOWREB caisson concept, which was then validated using results from experimental tests in a two-step approach: qualitatively, by comparing the “wave-structure” interaction on both physical and numerical models, and quantitatively, by comparing the reflection coefficients determined from the results of the numerical model simulations and those from the physical model tests. Once validated, the numerical model was used to carry out a comprehensive study of the hydrodynamic behavior of the LOWREB caisson aiming the understanding of the wave energy dissipation mechanisms and the assessment of its hydraulic efficiency with respect to wave reflection under an extended range of hydrodynamic conditions (e.g., water levels, wave heights, and wave periods). The numerical study confirmed the importance of the inner weirs on the wave energy dissipation. The hydraulic efficiency of the LOWREB caisson was found to be highly influenced by the combined effect of the wave period and water level. However, the influence of the wave height is not negligible: in general, energy dissipation increases with the wave height. Overall, the LOWREB caisson presents its best performance for the high and mean water level conditions, with all the values of the reflection coefficient below 70% and most of them in the range 30%–60%. The worse results obtained for the lower water level were attributed to the difficulties that waves have to overtop the weirs and enter the dissipative chambers, for this water level. In addition, streamlines, velocity and vorticity fields enabled obtaining important insights on the wave energy dissipation processes that take place during the wave-structure interaction, which results in the development of several vortices, not only inside the dissipative chambers, but also in front of the structure.During this work I. López was supported by the postdoctoral grant ED481B 2016/125-0 of the ‘Programa de Axudas á etapa posdoutoral da Xunta de Galicia (Consellería de Cultura, Educación e Ordenación Universitaria)’S
VIRTUAL REALITY - SHOWS A NEW VISION FOR TOURISM AND HERITAGE
Observe the heritage, a monument, architecture or a sculpture and immediately receive useful additional information to interpret better. This is one of the promises of virtual reality technology. The concept of virtual reality is far from being a new concept. Many experiments on ways to overcome layers of information, in addition to the real world elements, in live observation, have been made over the past decade, exploring different types of use, in leisure and professional contexts. Improving the perception of reality, in contrast to virtual reality, offers other initiatives that replace the context of a simulated world, and the possibility of using an interactive way to manipulate it in a digitally way. Those are the latest achievements that have opened new evolution perspectives of virtual reality. The idea behind most computer applications is to improve the user interaction with the real world, adding information through the use of tools and techniques that were confined to the digital world. But those applications could be used on tourism orientation in cities and in the professional world, in diverse areas, as architecture in the BIM environment or interior design architecture, with the projection of elements like the furniture and could be visualized in the virtual space. The ability to draw, could verify and share new realities, that was already being exploited by companies, which add new layers of information to be used in their catalogs and products that literally transform the hybrid PC, tablets and smartphones customer in additional information sources, that lead to know better what is observed, but in tourism and heritage that virtual reality is being used more intensively. Virtual Reality could be a good way to travel and understand the touristic world
Contributo de um Sistema de Apoio à Decisão para a Inserção no Mercado de Trabalho de Pessoas com Deficiência: Estudo de Caso e Proposta de Intervenção na ARCIL.
Nos últimos anos, o conceito de inclusão de pessoas com deficiência ou incapacidade
tem-se enraizado cada vez mais na sociedade, enquanto fator decisivo para a melhoria da
qualidade de vida ao nível da independência económica e consecutiva valorização e
concretização pessoal. Por outro lado, as empresas debatem-se cada vez mais com a
necessidade de atrair e reter talentos capazes de se adaptar às rápidas mudanças dos
mercados, avalizando a sobrevivência das mesmas. A necessidade da conceção de estratégias
de recrutamento que fossem além do simples conjúgio entre o perfil do cargo e o perfil do
candidato, levaram as empresas a adotar práticas associadas ao conceito de employer
branding, cujo objetivo consiste na promoção da empresa como marca empregadora honesta
e atrativa. Concomitantemente, a implementação de medidas socialmente responsáveis atenta
às condições de trabalho dos seus colaboradores e, às transgressões dos direitos humanos e
ambientais, associadas a ações de comunicação e marketing tornaram-se essenciais na
construção de uma marca empregadora.
A presente dissertação procurou compreender e identificar, os principais desafios que
as organizações de cariz social se debatem aquando da inserção no mercado de trabalho de
pessoas com deficiência. As respostas obtidas, a partir do estudo de caso realizado, foram de
encontro à necessidade de implementação de um sistema que permita um aconselhamento
adequado às necessidades específicas dos intervenientes no processo de inclusão na
sociedade e, consecutivamente, no mercado de trabalho. A falta de programas de
aconselhamento adequado às necessidades específicas de cada interveniente, bem como um
adequado mapeamento das competências individuais que permita agilizar os processos de
integração no mercado de trabalho e, facilitar o alinhamento com as necessidades de
recrutamento das organizações, representam alguns dos fatores decisivos na escolha desta
investigação.
Por sua vez, a temática de sistemas de apoio à decisão em contexto das OSFL, não
tem merecido a necessária atenção por parte dos investigadores. Mais do que preencher uma
lacuna detetada na literatura, pretendemos com este estudo prestar uma contribuição prática
para o desenvolvimento de metodologias de apoio à inserção no mercado normal de trabalho
de pessoas com deficiência ou incapacidade. Para o efeito, procedemos a um estudo de caso
conduzido no contexto do centro de recursos local da Associação para a Reabilitação de
Cidadãos Inadaptados da Lousã, com recurso à metodologia de investigação-ação. A amostra
foi constituída pelos elementos da equipa técnica (um responsável e dois técnicos) do
respetivo departamento e, foi conduzida sob a forma de entrevista semiestruturada.
Os resultados apontaram para a necessidade de um sistema informático capaz de
armazenar informação e auxiliar em todas as fases do processo de inserção no mercado
normal de trabalho. Assim sendo, a partir da referida metodologia de investigação-ação,
partimos para a conceção de um sistema sob a forma de plataforma online que, juntamente
com as empresas contratantes, permitisse auxiliar os técnicos responsáveis na seleção de
pessoas com deficiência ou incapacidade que mais se adequam às necessidades específicas da
empresa. Neste contexto, as conclusões sugerem que o desenvolvimento de um sistema de
apoio à decisão pode ter um contributo significativo, no percurso da inserção de pessoas com
deficiência e incapacidades no mercado de trabalho, bem como contribuir para uma maior
visibilidade destas organizações. / In recent years, inclusion of people with disabilities has risen in importance within
the civil society as a main vehicle for improving people’s lives at an economic and social
level. At the same time, companies are more than ever willing to recruit flexible and skilled
individuals, easily adaptable to the market pressures. The need to design new recruitment
strategies, beyond the simple relation job role-candidate profile, contributed to the adoption
of practices associated with the concept of employer branding, whose primary objective is the
promotion of the company itself, as an honest and attractive brand. Simultaneously, the
adoption of measures of social responsibility, focused on employees work conditions and
human and environmental rights, have become vital, in conjunction with marketing
communication actions, for the development of a strong employer brand.
The present dissertation sought to understand and identify the main challenges that
social organizations are struggling at the time of insertion in the labour market of people with
disabilities. The answers were obtained against the need for implementation of a system that
allows a suitable advice to the specific needs of stakeholders in the process of inclusion in
society and, consecutively, in the labour market. The lack of appropriate counselling
programs to the specific needs of each party, as well as an appropriate mapping of individual
skills in order to facilitate their integration in the labor market and their alignment with
company’s needs, represent some of the most prominent factors in the choice of this
investigation.
By its turn, decision support systems in context of OSFL is a topic only rarely seen in
the literature. More than filling a gap in the literature, our objective is to provide a practical
contribution to the development of methodologies to support a more smoother (market)
integration of people with disabilities. For this end, our case study was conducted in the
context of the local resource centre of the Association for the rehabilitation of Citizens
Misfits da Lousã, using the so-called research-action methodology. The studied sample was
constituted by elements of the coaching staff (an officer and two technicians) of the
respective Department and was conducted in the form of semi-structured interviews. Results
have clearly demonstrated the need for a computer system capable of storing all the
information and assist in all phases of the regular market integration work process. Therefore,
an online platform was designed to assist the technicians responsible for selecting those
people more qualified for the specific needs of the companies involved. In this context, our
findings suggest that the development of a decision support system can have a significant
impact in the course of PCDI insertion in the market labor, as well as contributing to a greater
visibility of these organizations
Cable robot for non-standard architecture and construction: A dynamic positioning system
In the past few years, cable-driven robots have received some attention by the scientific community and the industry. They have special characteristics that made them very reliable to operate with the level of safeness that is required by different environments, such as, handling of hazardous materials in construction sites. This paper presents a cable-driven robot called SPIDERobot, that was developed for automated construction of architectural projects. This robot has a rotating claw and it is controlled by a set of 4 cables that allow 4 degrees of freedom. In addition to the robot, this paper introduces a Dynamic Control System (DCS) that controls the positioning of the robot and assures that the length of cables is always within a safe value. Results show that traditional force-feasible approaches are more influenced by the pulling forces or the geometric arrangement of all cables and their positioning is significantly less accurate than the DCS. Therefore, the architecture of the SPIDERobot is designed to enable an easily scaling up of the solution to higher dimensions for operating in realistic environments.This work is partly funded by the project PTDC/ATPAQI/
5124/2012 - Robotic Technologies for Non-Standard Design
and Construction in Architecture. This work is also
financed by the ERDF European Regional Development Fund
through the COMPETE Programme (operational programme
for competitiveness) and by National Funds through the FCT
Portuguese Foundation for Science and Technology within
project ”FCOMP - 01-0124-FEDER-022701”info:eu-repo/semantics/publishedVersio
State estimation of over-sensored systems applied to a low-cost robotic manipulator
There is an increasing demand for robotic manipulators to perform more complex and versatile tasks. In order to fulfill this need, expeditious calibration and estimation techniques are required as a first step for the correct usage of the manipulator. This article aims at finding a subset of these algorithms that could be used in a generic manipulator and should allow for its prompt use. Two models for the representation of the pose of the manipulator are described and used in the state estimation problem. The results of the implementation are tested, and some performance metrics are obtained.info:eu-repo/semantics/publishedVersio
Real-time tracking system for a moored oil tanker: a kalman filter approach
This paper presents a tracking system developed to
study the behavior of an oil tanker moored at the Berth
"A" of the Leixões oli terminal, Porto, Portugal
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