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Publicações

Publicações por CRIIS

2020

Evaluation of Hunting-Based Optimizers for a Quadrotor Sliding Mode Flight Controller

Autores
Oliveira, J; Oliveira, PM; Boaventura Cunha, J; Pinho, T;

Publicação
ROBOTICS

Abstract
The design of Multi-Input Multi-Output nonlinear control systems for a quadrotor can be a difficult task. Nature inspired optimization techniques can greatly improve the design of non-linear control systems. Two recently proposed hunting-based swarm intelligence inspired techniques are the Grey Wolf Optimizer (GWO) and the Ant Lion Optimizer (ALO). This paper proposes the use of both GWO and ALO techniques to design a Sliding Mode Control (SMC) flight system for tracking improvement of altitude and attitude in a quadrotor dynamic model. SMC is a nonlinear technique which requires that its strictly coupled parameters related to continuous and discontinuous components be correctly adjusted for proper operation. This requires minimizing the tracking error while keeping the chattering effect and control signal magnitude within suitable limits. The performance achieved with both GWO and ALO, considering realistic disturbed flight scenarios are presented and compared to the classical Particle Swarm Optimization (PSO) algorithm. Simulated results are presented showing that GWO and ALO outperformed PSO in terms of precise tracking, for ideal and disturbed conditions. It is shown that the higher stochastic nature of these hunting-based algorithms provided more confidence in local optima avoidance, suggesting feasibility of getting a more precise tracking for practical use.

2020

Non-traditional processes and methodologies in Higher Education in Electrical Engineering: The perception of course coordinators in two Portuguese-speaking countries [Processos e metodologias não tradicionais no Ensino Superior de Engenharia Elétrica: A percepção de coordenadores de curso em dois países lusófonos] [Procesos y metodologías no tradicionales en la Educación Superior en Ingeniería Eléctrica: La percepción de los coordinadores de cursos en dos países de habla portuguesa]

Autores
Pereira, CA; Oliveira, PM; Reis, MJCS;

Publicação
Meta: Avaliacao

Abstract
The objective is to investigate the tools and methodologies used in Higher Education (HE) of Electrical and Computer Engineering (ECE), identifying the curricular units that used them. The analysis was based on the perception of the course coordinators. Triangulation between multiple methodologies and different methods of analysis was used, combining lexical analysis, analysis of keywords and content analysis. Course coordinators were interviewed at three universities in Portugal and Brazil. In the content analysis, two categories emerged: the coordinators' perception of non-traditional methodologies, and the perception of software tools as didactic resources. The initiatives using non-traditional teaching processes and methodologies were reduced and punctual, with individual actions by teachers and not of educational standards discussed and institutionalized. The precariousness of laboratory infrastructure and software licenses was a common report.

2020

Entropy Based Grey Wolf Optimizer

Autores
Duarte, D; Moura Oliveira, PBd; Solteiro Pires, EJ;

Publicação
Intelligent Data Engineering and Automated Learning - IDEAL 2020 - 21st International Conference, Guimaraes, Portugal, November 4-6, 2020, Proceedings, Part I

Abstract
Recently Shannon’s Entropy has been incorporated in nature inspired metaheuristics with good results. Depending on the problem, the Grey Wolf Optimization (GWO) algorithm may suffer from premature convergence. Here, an Entropy Grey Wolf Optimization (E-GWO) technique is proposed with the overall aim to improve the original GWO performance. The entropy is used to track the GWO swarm diversity, comparing the distance values between the Alpha in relation to the Beta and Delta wolves. The aim of the E-GWO variant is to improve convergence and prevent stagnation in local optima, since ideally restarting the swarm agents will prevent this from happening. Simulation results are presented showing that E-GWO restarting mechanism can achieve better results than the original GWO algorithm for some benchmark functions. © 2020, Springer Nature Switzerland AG.

2020

Swarm-Based Design of Proportional Integral and Derivative Controllers Using a Compromise Cost Function: An Arduino Temperature Laboratory Case Study

Autores
Oliveira, PBD; Hedengren, JD; Pires, EJS;

Publicação
ALGORITHMS

Abstract
Simple and easy to use methods are of great practical demand in the design of Proportional, Integral, and Derivative (PID) controllers. Controller design criteria are to achieve a good set-point tracking and disturbance rejection with minimal actuator variation. Achieving satisfactory trade-offs between these performance criteria is not easily accomplished with classical tuning methods. A particle swarm optimization technique is proposed to design PID controllers. The design method minimizes a compromise cost function based on both the integral absolute error and control signal total variation criteria. The proposed technique is tested on an Arduino-based Temperature Control Laboratory (TCLab) and compared with the Grey Wolf Optimization algorithm. Both TCLab simulation and physical data show that satisfactory trade-offs between the performance and control effort are enabled with the proposed technique.

2020

Students Drop Out Trends: A University Study

Autores
Silva, B; Solteiro Pires, EJ; Reis, A; Moura Oliveira, PBd; Barroso, J;

Publicação
Technology and Innovation in Learning, Teaching and Education - Second International Conference, TECH-EDU 2020, Vila Real, Portugal, December 2-4, 2020, Proceedings, 3

Abstract
The dropout of university students has been a factor of concern for educational institutions, affecting various aspects such as the institution’s reputation and funding and rankings. For this reason, it is essential to identify which students are at risk. In this study, algorithms based on decision trees and random forests are proposed to solve these problems using real data from 331 students from the University of Trásos-Montes and Alto Douro. In this work with these learning algorithms together with the training strategies, we managed to obtain an 89% forecast of students who may abandon their studies based on the evaluations of both semesters related to the first year and personal data. © 2021, Springer Nature Switzerland AG.

2020

Introducing Digital Controllers to Undergraduate Students using the TCLab Arduino Kit

Autores
Oliveira, PBD; Hedengren, JD; Rossiter, JA;

Publicação
IFAC PAPERSONLINE

Abstract
Many undergraduate engineering students have just a single introductory feedback control course in their study list. Often the curricula found in such courses is totally based on continuous time-domain classic control techniques. However, currently most control design techniques are implemented in digital machines. Thus, digital control concepts should be covered in introductory control courses. In this paper, the issue of how to implement and test digital industrial controllers is addressed. Teaching experiments based on the APMonitor temperature control lab (TCLab) are proposed. It will be shown that TCLab as an Arduino based portable kit, provides an excellent means to test digital controllers, as it is a compact and portable lab to be used by lecturers and students. While there are many low-cost and portable hardware options for teaching dynamics and control, a novel aspect of this paper is the digital control education methods that are validated with classroom experience, particularly with Biomedical and Bioengineering students. Preliminary results are presented. Copyright (C) 2020 The Authors.

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