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

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 Ciência 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 competition’s objects accurately and correctly performing the referee’s tasks.This work is financed by National Funds through the Portuguese funding agency, FCT - Funda¸c˜ao para a Ciˆencia 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 “la Caixa” 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 motors—one 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 –Vernacular 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 ‘SEISMIC - V – Vernacular Seismic Culture in Portu gal’ (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 São 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 São 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 egg–adult 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 ecológica foi construída para ovos e ninfas de Diaphorina citri Kuwayama (Hemiptera: Psyllidae) com dados obtidos em pomares de laranja (Citrus sinensis Osbeck) em 2 regiões do estado de São Paulo, com 4 gerações, no período de novembro de 2006 a maio de 2007, compreendendo as estações de primavera, verão e outono. Ramos jovens em crescimento com a presença de ovos de D. citri foram identificados e os indivíduos vivos foram contados até a emergência 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 ínstares por Tamarixia radiata Waterson (Hymenoptera: Eulophidae) foi de 2.3%. A duração do período de ovo a adulto foi semelhante entre as quatro gerações, 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 até o estágio adulto variou consideravelmente para o mesmo período, de 1.7 a 21.4%, sendo que as maiores mortalidades foram observadas nos estágios de ovos e ninfas pequenas (de primeiro a terceiro ínstares), as quais foram consideradas fases chaves para o crescimento populacional desta praga.info:eu-repo/semantics/publishedVersio