1,016 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 - FundacžaoË
para a Ciencia e Tecnologia within the Project Scope: Ë
UIDB/05757/2020info:eu-repo/semantics/publishedVersio
Modeling of an elastic joint: an experimental setup approach
Throughout this paper it is presented a novel elastic joint configuration, being compared with other similar joints found in recent literature. It is presented its modeling, being its estimation process developed offline, based on a proposed experimental setup. This setup enables to monitor and collect data from an absolute encoder and a load cell. Some data obtained from these sensors is then graphically represented, like angle and torque, obtaining some parameters. Finally, through an optimization process, where the error of the angle is minimized, the remaining parameters of the joint are estimated, thus obtaining a realistic model of the system.This work is financed by National Funds through the Portuguese funding agency, FCT- Fundação para a CiĂȘncia e a Tecnologia, with in project UIDB/50014/2020info:eu-repo/semantics/publishedVersio
Algebraic cycles and the classical groups II: Quaternionic cycles
In part I of this work we studied the spaces of real algebraic cycles on a
complex projective space P(V), where V carries a real structure, and completely
determined their homotopy type. We also extended some functors in K-theory to
algebraic cycles, establishing a direct relationship to characteristic classes
for the classical groups, specially Stiefel-Whitney classes. In this sequel, we
establish corresponding results in the case where V has a quaternionic
structure. The determination of the homotopy type of quaternionic algebraic
cycles is more involved than in the real case, but has a similarly simple
description. The stabilized space of quaternionic algebraic cycles admits a
nontrivial infinite loop space structure yielding, in particular, a delooping
of the total Pontrjagin class map. This stabilized space is directly related to
an extended notion of quaternionic spaces and bundles (KH-theory), in analogy
with Atiyah's real spaces and KR-theory, and the characteristic classes that we
introduce for these objects are nontrivial. The paper ends with various
examples and applications.Comment: Published by Geometry and Topology at
http://www.maths.warwick.ac.uk/gt/GTVol9/paper27.abs.htm
Robot at factory 4.0: an auto-referee proposal based on artificial vision
The robotization and automation of tasks are relevant processes and of great relevance to be considered nowadays. This work aims to turn the manual action of assigning the score for the robotic competition Robot at Factory 4.0 by an automatic referee. Specifically, the aim is to represent the real space in a set of computational information using computer vision, localization and mapping techniques. One of the crucial processes to achieve this goal involved the adaptive calibration of the parameters of a digital camera through visual references and tracking of objects, which resulted in a fully functional, robust and dynamic system that is capable of mapping the competitionâs objects accurately and correctly performing the refereeâs tasks.This work is financed by National Funds through the Portuguese
funding agency, FCT - FundažcËao para a CiËencia e a Tecnologia, within projects
LA/P/0063/2020 and POCI-01-0247-FEDER-072638, co-funded by FEDER through
COMPETE 2020. Authors acknowledge 5DPO RobotAtFactory team for making their
time and robot available to conduct tests. The project that gave rise to these results
received the support of a fellowship from âla Caixaâ Foundation (ID 100010434). The
fellowship code is LCF/BQ/DI20/11780028info:eu-repo/semantics/publishedVersio
Design, modeling, and control of an autonomous legged-wheeled hybrid robotic vehicle with non-rigid joints
This paper presents a legged-wheeled hybrid robotic vehicle that uses a combination of rigid and non-rigid joints, allowing it to be more impact-tolerant. The robot has four legs, each one with three degrees of freedom. Each leg has two non-rigid rotational joints with completely passive components for damping and accumulation of kinetic energy, one rigid rotational joint, and a driving wheel. Each leg uses three independent DC motorsâone for each joint, as well as a fourth one for driving the wheel. The four legs have the same position configuration, except for the upper hip joint. The vehicle was designed to be modular, low-cost, and its parts to be interchangeable. Beyond this, the vehicle has multiple operation modes, including a low-power mode. Across this article, the design, modeling, and control stages are presented, as well as the communication strategy. A prototype platform was built to serve as a test bed, which is described throughout the article. The mechanical design and applied hardware for each leg have been improved, and these changes are described. The mechanical and hardware structure of the complete robot is also presented, as well as the software and communication approaches. Moreover, a realistic simulation is introduced, along with the obtained results.info:eu-repo/semantics/publishedVersio
Systematisation of seismic retrofitting in vernacular architecture
This paper aims to identify and to systematize the data obtained during the working process of
the
research
project 'SEISMIC-V âVernacular Seismic Culture in Portugal' in terms of seismic-
retrofitting elements earthquake -resistant reinforcement implemented in vernacular buildings. The data will be distinguished based on the structural
seismic strengthening and according to the following criteria:
strengthening
elements,
perimeter
seismic-resistant elements, arches reinforcing elements, and combined
reinforcing elements.Portuguese Science and Technology Foundation (FCT) to the research project âSEISMIC - V â Vernacular Seismic Culture in Portu galâ (PTDC/ATP - AQI/ 3934/2012
Data fusion using ultra wideband time-of-flight positioning for mobile robot applications
Self-localization of a robot is one of the most important requirements in mobile robotics. There are several approaches to providing localization data. The Ultra Wide Band Time of Flight provides position information but lacks the angle. Odometry data can be combined by using a data fusion algorithm. This paper addresses the application of data fusion algorithms based on odometry and Ultra Wide Band Time of Flight positioning using a Kalman filter that allows performing the data fusion task which outputs the position and orientation of the robot. The proposed solution, validated in a real developed platform can be applied in service and industrial robots.he authors are grateful to the Foundation for Sci- ence and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES (PIDDAC) to CeDRI (UIDB/05757/2020 and UIDP/05757/2020) and SusTEC (LA/P/0007/2021). This work has been supported by NORTE- 01-0247-FEDER-072598 iSafety: Intelligent system for occu- pational safety and well-being in the retail sector. The authors also want to thank CEFET-RJ and FAPERJ.info:eu-repo/semantics/publishedVersio
Life table analysis of Diaphorina citri (Hemiptera: Psyllidae) infesting sweet orange (Citrus sinensis) in SĂŁo Paulo
An ecological life table for eggs and nymphs of Diaphorina citri Kuwayama (Hemiptera:
Psyllidae) was constructed with data obtained from orange orchards (Citrus sinensis Osbeck) in 2 regions of the State of SĂŁo Paulo, over 4 generations in the period from XI-2006
to V-2007, comprising spring, summer, and fall seasons. Young growing shoots with D. citri
eggs present were identifed, and live individuals were counted until adult emergence. No
predatory arthropods were observed in association with D. citri eggs and nymphs during
the study. The mean parasitism of fourth- and ffth-instar nymphs by Tamarixia radiata
Waterston (Hymenoptera: Eulophidae) was 2.3%. The durations of the eggâadult period
were similar among the 4 generations, ranging from 18.0 to 24.7 d (at mean temperatures
ranging from 21.6 to 26.0 °C) and followed the temperature requirement models obtained
in the laboratory for D. citri. However, survival from the egg to the adult stage for the same
period varied considerably from 1.7 to 21.4%; the highest mortalities were observed in the
egg and small nymphal (frst- to thirdinstar) stages, which were considered to be key phases
for population growth of the pest.Uma tabela de vida ecolĂłgica foi construĂda para ovos e ninfas de Diaphorina citri Kuwayama (Hemiptera: Psyllidae) com dados obtidos em pomares de laranja (Citrus sinensis Osbeck) em 2 regiĂ”es do estado de SĂŁo Paulo, com 4 geraçÔes, no perĂodo de novembro de 2006
a maio de 2007, compreendendo as estaçÔes de primavera, verão e outono. Ramos jovens
em crescimento com a presença de ovos de D. citri foram identificados e os indivĂduos vivos
foram contados atĂ© a emergĂȘncia dos adultos. Nenhum predador foi observado associado a
ovos e ninfas de D. citri durante o estudo. A taxa média de parasitismo de ninfas de quarto
e quinto Ănstares por Tamarixia radiata Waterson (Hymenoptera: Eulophidae) foi de 2.3%.
A duração do perĂodo de ovo a adulto foi semelhante entre as quatro geraçÔes, variando de
18.0 a 24.7 dias (com temperaturas médias de 21.6 a 26.0 °C) e seguiram os modelos de
exigencias térmicas obtidas em laboratório para D. citri. Todavia, a sobrevivencia de ovo
atĂ© o estĂĄgio adulto variou consideravelmente para o mesmo perĂodo, de 1.7 a 21.4%, sendo
que as maiores mortalidades foram observadas nos estĂĄgios de ovos e ninfas pequenas (de
primeiro a terceiro Ănstares), as quais foram consideradas fases chaves para o crescimento
populacional desta praga.info:eu-repo/semantics/publishedVersio
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