Rui Esteves Araujo

Abstract

Abstract
This paper addresses the problem of the left inversion of switched linear systems from a diagnostics perspective. The problem of left inversion is to reconstruct the input of a system with the knowledge of its output, whose differentiation is usually required. In the case of this work, the objective is to reconstruct the system’s unknown inputs, based on the knowledge of its outputs, switching sequence and known inputs. With the inverse model of the switched linear system, a real-time Fault Detection and Isolation (FDI) algorithm with an integrated Fuzzy Logic System (FLS) that is capable of detecting and isolating abrupt faults occurring in the system is developed. In order to attenuate the effects of unknown disturbances and noise at the output of the inverse model, a smoothing strategy is also used. The results are illustrated with an example. The performance of the method is validated experimentally in a DC-DC boost converter, using a low-cost microcontroller, without any additional components. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Abstract
This paper presents theory, a new approach and validation results for fault detection and isolation (FDI) in DC-DC power converters, based on inversion method. The developed method consists on the inversion-based estimation of faults and change detection mechanisms adapted to the power converters context. With the inverse model of a switched linear system, we have designed a real-time FDI algorithm with an integrated fuzzy logic scheme which detects and isolates abrupt changes (faults) at unknown time instants. A smoothing strategy is used to attenuate the effect of unknown disturbances and noise that are present at the outputs of this inverse model. Once the fault event is detected, a dedicated fuzzy-logic-based scheme is proposed to isolate the four types of faults: switch, voltage and current sensor, and capacitor. The performance of the proposed method is verified experimentally to detect and isolate the mentioned faults in the DC-DC boost power converter.

Abstract
This paper presents steganography techniques that were employed to avoid human perception of the added audio signals in an acoustic environment for indoor location purposes. In the context of audio forensics, indoor location can be used in connection with the detection of a crime. The validation of using the acoustic channel for data transmission over an almost imperceptible audio signal enables the possibility of a receiving processing mobile device (such as a smartphone) to localize itself absolutely by receiving and processing such signals from the infrastructure. Some possible applications will be presented demonstrating the utility of this technology. This paper will present the use of almost imperceptible audio signals to successfully transmit hidden information using a spread spectrum data-hiding technique or a music/speech cover signal and the echo hiding technique.

Abstract
This paper presents a high precision speed control of the reluctance machine for electric drive applications. To get high resolution speed control, it is developed a cascade control algorithm based on linear control technique. The controller was designed using the Root Locus Methodology and has been implemented on a numerical simulation platform. It is shown that Root Locus Methodology design is a viable approach, and that various problems associated with the structural torque ripple of the electric motor can be solved. An important aspect of this work is the role played by model linearization in testing the sensitivity of the controller performance to specific parameter changes. The controller was implemented in a simulated non-linear switched reluctance motor model in order to evaluate their performances. Simulations results show that the high-performance control for Switched Reluctance Motor has been achieved.