Navegando por Autor "Silva, Guilherme Augusto Lopes"
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Item Self-supervised learning for arrhythmia classification.(2023) Silva, Guilherme Augusto Lopes; Luz, Eduardo José da Silva; Silva, Pedro Henrique Lopes; Luz, Eduardo José da Silva; Silva, Pedro Henrique Lopes; Freitas, Vander Luis de Souza; Meneghini, Ivan ReinaldoArrhythmias, heart diseases that are commonly diagnosed through electrocar- diograms (ECG), require computational methods for detection and classification to improve the physician’s diagnosis. Although there is abundant literature on the subject, the high intra-patient variability and noise of ECG signals pose challenges in developing practical machine-learning models. To address this, we propose a cus- tomized adjustment of machine learning models through self-supervised learning with human-in-the-loop. Our approach introduces a pretext task called ECGWavePuzzle, which improves classification performance through better generalization. Evaluation metrics on the MIT-BIH database demonstrate the effectiveness of our approach, which improved the ECGnet global accuracy by over 10% and the Mousavi’s CNN by over 13%. Additionally, the experimental results demonstrated that the proposed approach improved the sensitivity and positive predictive value of the arrhythmic classes for certain patients.Item A VNS algorithm for PID controller : hardware-in-the-loop approach.(2021) Silva, Guilherme Augusto Lopes; Silva, Pedro Henrique Lopes; Santos, Valéria; Rêgo Segundo, Alan Kardek; Luz, Eduardo José da Silva; Moreira, Gladston Juliano PratesTuning the Proportional Integral Derivative, or PID, controller in cyber-physical systems is a major challenge as it requires advanced mathematical skills. Several authors in the literature have shown that optimization algorithms are efficient for auto-adjust PID controller constants, especially when there is no mathematical modeling. However, the literature lacks works that show the efficiency of the Variable Neighborhood Search (VNS) algorithm to auto-adjust the PID. In this work, we investigate the efficiency of the Variable Neighborhood Algorithm to fine-tune a PID controller of a real cyber physical-system: a birotor flying drone. The approach consists of applying a numerical neighborhood structure to optimize the three constants of the PID, according to a proposed fitness function. Experiments reveal the feasibility of fine-tuning the PID controller and the birotor balancing with the Variable Neighborhood Algorithm with reduced time. We compared the VNS-approach against one based on genetic algorithms, and on average, the VNS-approach achieves better results with lower computational and memory costs. Results suggest that the approach may be used in real or commercial systems, helping to fine-tune the controller to new environment changes or even last-minute project modifications.