262 research outputs found
NOVEL METHODS FOR PERMANENT MAGNET DEMAGNETIZATION DETECTION IN PERMANENT MAGNET SYNCHRONOUS MACHINES
Monitoring and detecting PM flux linkage is important to maintain a stable permanent magnet synchronous motor (PMSM) operation. The key problems that need to be solved at this stage are to: 1) establish a demagnetization magnetic flux model that takes into account the influence of various nonlinear and complex factors to reveal the demagnetization mechanism; 2) explore the relationship between different factors and demagnetizing magnetic field, to detect the demagnetization in the early stage; and 3) propose post-demagnetization measures. This thesis investigates permanent magnet (PM) demagnetization detection for PMSM machines to achieve high-performance and reliable machine drive for practical industrial and consumer applications. In this thesis, theoretical analysis, numerical calculation as well as experimental investigations are carried out to systematically study the demagnetization detection mechanism and post-demagnetization measures for permanent magnet synchronous motors. At first a flux based acoustic noise model is proposed to analyze online PM demagnetization detection by using a back propagation neural network (BPNN) with acoustic noise data. In this method, the PM demagnetization is detected by means of comparing the measured acoustic signal of PMSM with an acoustic signal library of seven acoustical indicators. Then torque ripple is chosen for online PM demagnetization diagnosis by using continuous wavelet transforms (CWT) and Grey System Theory (GST). This model is able to reveal the relationship between torque variation and PM electromagnetic interferences. After demagnetization being detected, a current regulation strategy is proposed to minimize the torque ripples induced by PM demagnetization. Next, in order to compare the demagnetization detection accuracy, different data mining techniques, Vold-Kalman filtering order tracking (VKF-OT) and dynamic Bayesian network (DBN) based detection approach is applied to real-time PM flux monitoring through torque ripple again. VKF-OT is introduced to track the order of torque ripple of PMSM running in transient state. Lastly, the combination of acoustic noise and torque is investigated for demagnetization detection by using multi-sensor information fusion to improve the system redundancy and accuracy. Bayesian network based multi-sensor information fusion is then proposed to detect the demagnetization ratio from the extracted features. During the analysis of demagnetization detection methods, the proposed PM detection approaches both form torque ripple and acoustic noise are extensively evaluated on a laboratory PM machine drive system under different speeds, load conditions, and temperatures
30th International Conference on Condition Monitoring and Diagnostic Engineering Management (COMADEM 2017)
Proceedings of COMADEM 201
Three-dimensional geometry characterization using structured light fields
Tese de doutoramento. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 200
Multichannel analysis of normal and continuous adventitious respiratory sounds for the assessment of pulmonary function in respiratory diseases
Premi extraordinari doctorat UPC curs 2015-2016, à mbit d’Enginyeria IndustrialRespiratory sounds (RS) are produced by turbulent airflows through the airways and are
inhomogeneously transmitted through different media to the chest surface, where they can be recorded
in a non-invasive way. Due to their mechanical nature and airflow dependence, RS are affected by
respiratory diseases that alter the mechanical properties of the respiratory system. Therefore, RS provide
useful clinical information about the respiratory system structure and functioning.
Recent advances in sensors and signal processing techniques have made RS analysis a more objective
and sensitive tool for measuring pulmonary function. However, RS analysis is still rarely used in clinical
practice. Lack of a standard methodology for recording and processing RS has led to several different
approaches to RS analysis, with some methodological issues that could limit the potential of RS analysis
in clinical practice (i.e., measurements with a low number of sensors, no controlled airflows, constant
airflows, or forced expiratory manoeuvres, the lack of a co-analysis of different types of RS, or the use
of inaccurate techniques for processing RS signals).
In this thesis, we propose a novel integrated approach to RS analysis that includes a multichannel
recording of RS using a maximum of five microphones placed over the trachea and the chest surface,
which allows RS to be analysed at the most commonly reported lung regions, without requiring a large
number of sensors. Our approach also includes a progressive respiratory manoeuvres with variable
airflow, which allows RS to be analysed depending on airflow. Dual RS analyses of both normal RS
and continuous adventitious sounds (CAS) are also proposed. Normal RS are analysed through the RS
intensity–airflow curves, whereas CAS are analysed through a customised Hilbert spectrum (HS),
adapted to RS signal characteristics.
The proposed HS represents a step forward in the analysis of CAS. Using HS allows CAS to be fully
characterised with regard to duration, mean frequency, and intensity. Further, the high temporal and
frequency resolutions, and the high concentrations of energy of this improved version of HS, allow CAS
to be more accurately characterised with our HS than by using spectrogram, which has been the most
widely used technique for CAS analysis.
Our approach to RS analysis was put into clinical practice by launching two studies in the Pulmonary
Function Testing Laboratory of the Germans Trias i Pujol University Hospital for assessing pulmonary
function in patients with unilateral phrenic paralysis (UPP), and bronchodilator response (BDR) in
patients with asthma. RS and airflow signals were recorded in 10 patients with UPP, 50 patients with
asthma, and 20 healthy participants.
The analysis of RS intensity–airflow curves proved to be a successful method to detect UPP, since we
found significant differences between these curves at the posterior base of the lungs in all patients whereas no differences were found in the healthy participants. To the best of our knowledge, this is the
first study that uses a quantitative analysis of RS for assessing UPP.
Regarding asthma, we found appreciable changes in the RS intensity–airflow curves and CAS features
after bronchodilation in patients with negative BDR in spirometry. Therefore, we suggest that the
combined analysis of RS intensity–airflow curves and CAS features—including number, duration, mean
frequency, and intensity—seems to be a promising technique for assessing BDR and improving the
stratification of BDR levels, particularly among patients with negative BDR in spirometry.
The novel approach to RS analysis developed in this thesis provides a sensitive tool to obtain objective
and complementary information about pulmonary function in a simple and non-invasive way. Together
with spirometry, this approach to RS analysis could have a direct clinical application for improving the
assessment of pulmonary function in patients with respiratory diseases.Los sonidos respiratorios (SR) se generan con el paso del flujo de aire a través de las vÃas respiratorias y se transmiten de forma no homogénea hasta la superficie torácica. Dada su naturaleza mecánica, los SR se ven afectados en gran medida por enfermedades que alteran las propiedades mecánicas del sistema respiratorio. Por lo tanto, los SR proporcionan información clÃnica relevante sobre la estructura y el funcionamiento del sistema respiratorio. La falta de una metodologÃa estándar para el registro y procesado de los SR ha dado lugar a la aparición de diferentes estrategias de análisis de SR con ciertas limitaciones metodológicas que podrÃan haber restringido el potencial y el uso de esta técnica en la práctica clÃnica (medidas con pocos sensores, flujos no controlados o constantes y/o maniobras forzadas, análisis no combinado de distintos tipos de SR o uso de técnicas poco precisas para el procesado de los SR). En esta tesis proponemos un método innovador e integrado de análisis de SR que incluye el registro multicanal de SR mediante un máximo de cinco micrófonos colocados sobre la tráquea yla superficie torácica, los cuales permiten analizar los SR en las principales regiones pulmonares sin utilizar un número elevado de sensores . Nuestro método también incluye una maniobra respiratoria progresiva con flujo variable que permite analizar los SR en función del flujo respiratorio. También proponemos el análisis combinado de los SR normales y los sonidos adventicios continuos (SAC), mediante las curvas intensidad-flujo y un espectro de Hilbert (EH) adaptado a las caracterÃsticas de los SR, respectivamente. El EH propuesto representa un avance importante en el análisis de los SAC, pues permite su completa caracterización en términos de duración, frecuencia media e intensidad. Además, la alta resolución temporal y frecuencial y la alta concentración de energÃa de esta versión mejorada del EH permiten caracterizar los SAC de forma más precisa que utilizando el espectrograma, el cual ha sido la técnica más utilizada para el análisis de SAC en estudios previos. Nuestro método de análisis de SR se trasladó a la práctica clÃnica a través de dos estudios que se iniciaron en el laboratorio de pruebas funcionales del hospital Germans Trias i Pujol, para la evaluación de la función pulmonar en pacientes con parálisis frénica unilateral (PFU) y la respuesta broncodilatadora (RBD) en pacientes con asma. Las señales de SR y flujo respiratorio se registraron en 10 pacientes con PFU, 50 pacientes con asma y 20 controles sanos. El análisis de las curvas intensidad-flujo resultó ser un método apropiado para detectar la PFU , pues encontramos diferencias significativas entre las curvas intensidad-flujo de las bases posteriores de los pulmones en todos los pacientes , mientras que en los controles sanos no encontramos diferencias significativas. Hasta donde sabemos, este es el primer estudio que utiliza el análisis cuantitativo de los SR para evaluar la PFU. En cuanto al asma, encontramos cambios relevantes en las curvas intensidad-flujo yen las caracterÃsticas de los SAC tras la broncodilatación en pacientes con RBD negativa en la espirometrÃa. Por lo tanto, sugerimos que el análisis combinado de las curvas intensidad-flujo y las caracterÃsticas de los SAC, incluyendo número, duración, frecuencia media e intensidad, es una técnica prometedora para la evaluación de la RBD y la mejora en la estratificación de los distintos niveles de RBD, especialmente en pacientes con RBD negativa en la espirometrÃa. El método innovador de análisis de SR que se propone en esta tesis proporciona una nueva herramienta con una alta sensibilidad para obtener información objetiva y complementaria sobre la función pulmonar de una forma sencilla y no invasiva. Junto con la espirometrÃa, este método puede tener una aplicación clÃnica directa en la mejora de la evaluación de la función pulmonar en pacientes con enfermedades respiratoriasAward-winningPostprint (published version
Computational and Numerical Simulations
Computational and Numerical Simulations is an edited book including 20 chapters. Book handles the recent research devoted to numerical simulations of physical and engineering systems. It presents both new theories and their applications, showing bridge between theoretical investigations and possibility to apply them by engineers of different branches of science. Numerical simulations play a key role in both theoretical and application oriented research
Speech Recognition
Chapters in the first part of the book cover all the essential speech processing techniques for building robust, automatic speech recognition systems: the representation for speech signals and the methods for speech-features extraction, acoustic and language modeling, efficient algorithms for searching the hypothesis space, and multimodal approaches to speech recognition. The last part of the book is devoted to other speech processing applications that can use the information from automatic speech recognition for speaker identification and tracking, for prosody modeling in emotion-detection systems and in other speech processing applications that are able to operate in real-world environments, like mobile communication services and smart homes
MATLAB
A well-known statement says that the PID controller is the "bread and butter" of the control engineer. This is indeed true, from a scientific standpoint. However, nowadays, in the era of computer science, when the paper and pencil have been replaced by the keyboard and the display of computers, one may equally say that MATLAB is the "bread" in the above statement. MATLAB has became a de facto tool for the modern system engineer. This book is written for both engineering students, as well as for practicing engineers. The wide range of applications in which MATLAB is the working framework, shows that it is a powerful, comprehensive and easy-to-use environment for performing technical computations. The book includes various excellent applications in which MATLAB is employed: from pure algebraic computations to data acquisition in real-life experiments, from control strategies to image processing algorithms, from graphical user interface design for educational purposes to Simulink embedded systems
Fourier Transforms
The 21st century ushered in a new era of technology that has been reshaping everyday life, simplifying outdated processes, and even giving rise to entirely new business sectors. Today, contemporary users of products and services expect more and more personalized products and services that can meet their unique needs. In that sense, it is necessary to further develop existing methods, adapt them to new applications, or even discover new methods. This book provides a thorough review of some methods that have an increasing impact on humanity today and that can solve different types of problems even in specific industries. Upgrading with Fourier Transformation gives a different meaning to these methods that support the development of new technologies and have a good projected acceleration in the future
- …