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Publicações

2018

PID controller tuning for integrating processes

Autores
Vrancic, D; Huba, M; Oliveira, PM;

Publicação
IFAC-PapersOnLine

Abstract
The proposed tuning method for integrating processes, which is based on Magnitude optimum criterion, has been extended to PID types of controllers. The method requires either the process transfer function (in frequency-domain) or the measurement of process steady-state change (in time-domain). The PID controller parameters are calculated analytically by solving fourth-order polynomial. By changing reference-weighting parameter b, the user can favour tracking (higher b) or control performance (lower b). The proposed method has been tested on several process models (lower-order with delay, higher order with delay, and a phase non-minimum process) and the closed-loop responses were relatively fast and non-oscillatory. The comparison with other tuning method based on process step-response data results in favourable tracking and control performance. © 2018

2018

Modeling and Simulation of a Switched Reluctance Motor with Hysteresis Effect

Autores
Melo, P; Araujo, RE;

Publicação
2018 INTERNATIONAL SYMPOSIUM ON POWER ELECTRONICS, ELECTRICAL DRIVES, AUTOMATION AND MOTION (SPEEDAM)

Abstract
Switched reluctance machines (SRM) are simple, robust and fault tolerant machines, usually operating under strong nonlinear characteristics. Therefore, accurately modeling this machine is a demanding task. Several models have been proposed, where magnetic saturation is often addressed, without considering hysteresis effect. In the proposed model the SRM magnetization characteristics are generated through the Jiles-Atherton (J-A) hysteresis model. Thus, instead of a post-processing inclusion, hysteresis is considered in simulation. This is the model main attribute, which is discussed in detail. This may contribute for a better understanding of hysteresis impact over the SRM operation modes. Simulation results are also presented and discussed.

2018

Fabrication of Monolithic Add-Drop Filters in Pure Silica by Femtosecond Laser Writing

Autores
Marques, PVS; Amorim, VA; Maia, JM; Alexandre, D; Viveiros, D;

Publicação
2018 20TH ANNIVERSARY INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON)

Abstract
This paper will review the fabrication of monolithic integrated optical devices by laser direct writing with femtosecond pulsed laser sources, starting with the description of experimental procedures and optimal conditions to fabricate low loss optical waveguides, directional couplers, Y-junctions and first order Bragg gratings by point-by-point writing methods. Finally, the characterization results of a fully operational Add-Drop filter in pure fused silica substrate are described.

2018

Outliers and the Simpson's Paradox

Autores
Portela, E; Ribeiro, RP; Gama, J;

Publicação
ADVANCES IN SOFT COMPUTING, MICAI 2017, PT I

Abstract
There is no standard definition of outliers, but most authors agree that outliers are points far from other data points. Several outlier detection techniques have been developed mainly with two different purposes. On one hand, outliers are the interesting observations, like in fraud detection, on the other side, outliers are considered measurement observations that should be removed from the analysis, e.g. robust statistics. In this work, we start from the observation that outliers are effected by the so called Simpson paradox: a trend that appears in different groups of data but disappears or reverses when these groups are combined. Given a dataset, we learn a regression tree. The tree grows by partitioning the data into groups more and more homogeneous of the target variable. At each partition defined by the tree, we apply a box plot on the target variable to detect outliers. We would expected that deeper nodes of the tree contain less and less outliers. We observe that some points previously signaled as outliers are no more signaled as such, but new outliers appear. The identification of outliers depends on the context considered. Based on this observation, we propose a new method to quantify the level of outlierness of data points. © Springer Nature Switzerland AG 2018.

2018

Computer applications for education on industrial robotic systems

Autores
Fonseca Ferreira, NMF; Freitas, EDC;

Publicação
COMPUTER APPLICATIONS IN ENGINEERING EDUCATION

Abstract
The paper describes the use of computer applications on education for industrial robotic systems. Robotics evolved as a central issue in teaching for scientific and engineering courses and inherently encompasses a spectrum of sciences and technologies and qualification levels. However, most current teaching approaches, related to robotics, concentrate on individual aspects or small student groups and do not involve dangerous situations. With a mixed-reality robotics teaching, a true interdisciplinary setup can be reached, this approach has been used in a robotics course at higher education, to prepare students for future activities in industry and also in research. This active learning experience approach in the field of Industrial Robotics was implemented in a Master degree on Electrical Engineering.

2018

Telepresence Robots in the Classroom: The State-of-the-Art and a Proposal for a Telepresence Service for Higher Education

Autores
Reis, A; Martins, MG; Martins, P; Sousa, J; Barroso, J;

Publicação
Technology and Innovation in Learning, Teaching and Education - First International Conference, TECH-EDU 2018, Thessaloniki, Greece, June 20-22, 2018, Revised Selected Papers

Abstract
In this work we reviewed the current state-of-the art regarding the usage of robots, in particular telepresence robots, on educational related activities. We also researched the current consumer and corporate grade telepresence robotic equipment and tested three of these devices. Lastly, we reviewed the problem of disabled students, including students with special education needs, which fail at accessing and staying on higher education. One of the reasons for such problem is the impossibility to physically attend all the classes due to temporary or permanent limitations. As a conclusion of this work, and considering the ongoing positive cases with robotics and the current equipment availability, we propose the creation of telepresence services on the higher education institutions as a solution for those students that can’t attend classes. © Springer Nature Switzerland AG 2019.

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