Smart filter aided domain adversarial neural network: An unsupervised domain adaptation method for fault diagnosis in noisy industrial scenarios

The application of unsupervised domain adaptation (UDA)-based fault diagnosis methods has shown significant efficacy in industrial settings, facilitating the transfer of operational experience and fault signatures between different operating conditions, different units of a fleet or between simulated and real data. However, in real industrial scenarios, unknown levels and types of noise can amplify the difficulty of domain alignment, thus severely affecting the diagnostic performance of deep learning models. To address this issue, we propose an UDA method called Smart Filter-Aided Domain Adversarial Neural Network (SFDANN) for fault diagnosis in noisy industrial scenarios. The proposed methodology comprises two steps. In the first step, we develop a smart filter that dynamically enforces similarity between the source and target domain data in the time-frequency domain. This is achieved by combining a learnable wavelet packet transform network (LWPT) and a traditional wavelet packet transform module. In the second step, we input the data reconstructed by the smart filter into a domain adversarial neural network (DANN). To learn domain-invariant and discriminative features, the learnable modules of SFDANN are trained in a unified manner with three objectives: time-frequency feature proximity, domain alignment, and fault classification. We validate the effectiveness of the proposed SFDANN method based on two fault diagnosis cases: one involving fault diagnosis of bearings in noisy environments and another involving fault diagnosis of slab tracks in a train-track-bridge coupling vibration system, where the transfer task involves transferring from numerical simulations to field measurements. Results show that compared to other representative state of the art UDA methods, SFDANN exhibits superior performance and remarkable stability

Extraction of functional dynamic networks describing patient's epileptic seizures

International audienceIntracranial EEG studies using stereotactic EEG (SEEG) have shown that during seizures, epileptic activity spreads across several anatomical regions from the seizure onset zone towards remote brain areas. This appears like patient-specific time-varying networks that has to be extracted and characterised. Functional Connectivity (FC) analysis of SEEG signals recorded during seizures enables to describe the statistical relations between all pairs of recorded signals. However, extracting meaningful information from those large datasets is time-consuming and requires high expertise. In the present study [1], we propose a novel method named Brain-wide Time-varying Network Decomposition (BTND) to characterise the dynamic epileptogenic networks activated during seizures in individual patients recorded with SEEG electrodes. The method provides a number of pathological FC subgraphs with their temporal course of activation. The method can be applied to several seizures of the patient to extract reproducible subgraphs. To validate the extraction, we compare the activated subgraphs obtained by BTND to interpretation of SEEG signals recorded in 27 seizures from 9 different patients. We a found a good agreement about the activated subgraphs and the corresponding brain regions involved during the seizures and their activation dynamics

Réduction de dimension tensorielle parcimonieuse: Application au clustering de connectivité fonctionnelle

National audiencek-means est un algorithme célèbre pour le clustering de données, mais ses performances se dégradent sur des données de grandes dimensions. Nous proposons des décompositions tensorielles parcimonieuses pour réduire la dimension des données avant d'appliquer k-means. Nous illustrons notre méthode sur des mesures de connectivité fonctionnelle d'EEG de crises épileptiques. Abstract-k-means is famous to cluster a dataset, however it is known to perform badly on high dimensional data. To apply it on EEG functional connectivity measures, as function of the time and for different seizures of a same patient, we develop a new sparse tensorial decomposition to reduce the dimensions of the data before applying k-means

Inférence et décomposition modale de réseaux dynamiques en neurosciences

Dynamic graphs make it possible to understand the evolution of complex systems evolving over time. This type of graph has recently received considerable attention. However, there is no consensus on how to infer and study these graphs. In this thesis, we propose specific methods for dynamical graph analysis. A dynamical graph can be seen as a succession of complete graphs sharing the same nodes, but with the weights associated with each link changing over time. The proposed methods can have applications in neuroscience or in the study of social networks such as Twitter and Facebook for example. The issue of this thesis is epilepsy, one of the most common neurological diseases in the world affecting around 1% of the population.The first part concerns the inference of dynamical graph from neurophysiological signals. To assess the similarity between each pairs of signals, in order to make the graph, we use measures of functional connectivity. The comparison of these measurements is therefore of great interest to understand the characteristics of the resulting graphs. We then compare functional connectivity measurements involving the instantaneous phase and amplitude of the signals. We are particularly interested in a measure called Phase-Locking-Value (PLV) which quantifies the phase synchrony between two signals. We then propose, in order to infer robust and interpretable dynamic graphs, two new indexes that are conditioned and regularized PLV. The second part concerns tools for dynamical graphs decompositions. The objective is to propose a semi-automatic method in order to characterize the most important patterns in the pathological network from several seizures of the same patient. First, we consider seizures that have similar durations and temporal evolutions. In this case the data can be conveniently represented as a tensor. A specific tensor decomposition is then applied. Secondly, we consider seizures that have heterogeneous durations. Several strategies are proposed and compared. These are methods which, in addition to extracting the characteristic subgraphs common to all the seizures, make it possible to observe their temporal activation profiles specific to each seizures. Finally, the selected method is used for a clinical application. The obtained decompositions are compared to the visual interpretation of the clinician. As a whole, we found that activated subgraphs corresponded to brain regions involved during the course of the seizures and their time course were highly consistent with classical visual interpretation.Les graphes dynamiques permettent de comprendre l'évolution de systèmes complexes qui évoluent dans le temps. Ce type de graphe a récemment fait l'objet d'une attention considérable. Cependant, il n'existe pas de consensus sur les manières d'inférer et d'étudier ces graphes. Dans cette thèse, on propose des méthodes d'analyse de graphes dynamiques spécifiques. Ceux-ci peuvent être vues comme une succession de graphes complets partageant les mêmes nœuds, mais dont les poids associés à chaque lien évoluent dans le temps. Les méthodes proposées peuvent avoir des applications en neurosciences ou dans l'étude des réseaux sociaux comme Twitter et Facebook par exemple. L'enjeu applicatif de cette thèse est l'épilepsie, l'une des maladies neurologiques les plus rependues dans le monde affectant environ 1% de la population.La première partie concerne l'inférence de graphe dynamique à partir de signaux neurophysiologiques. Cette inférence est généralement réalisée à l'aide de mesures de connectivité fonctionnelle permettant d'évaluer la similarité entre deux signaux. La comparaison de ces mesures est donc d'un grand intérêt pour comprendre les caractéristiques des graphes obtenus. On compare alors des mesures de connectivité fonctionnelle impliquant la phase et l'amplitude instantanée des signaux. On s'intéresse en particulier à une mesure nommée Phase-Locking-Value (PLV) qui quantifie la synchronie des phases entre deux signaux. On propose ensuite, afin d'inférer des graphes dynamiques robustes et interprétables, deux nouvelles mesures de PLV conditionnées et régulariséesLa seconde partie présente des méthodes de décomposition de graphes dynamiques. L'objectif est de proposer une méthode semi-automatique afin de caractériser les informations les plus importantes du réseau pathologique de plusieurs crises d'un même patient. Dans un premier temps on considère des crises qui ont des durées et des évolutions temporelles similaires. Une décomposition tensorielle spécifique est alors appliquée. Dans un second temps, on considère des crises qui ont des durées hétérogènes. Plusieurs stratégies sont proposées et comparées. Ce sont des méthodes qui en plus d'extraire les sous-graphes caractéristiques communs à toutes les crises, permettent d'observer leurs profils d'activation temporelle spécifiques à chaque crise. Finalement, on utilise la méthode retenue pour une application clinique. Les décompositions obtenues sont comparées à l'interprétation visuelle du clinicien. Dans l'ensemble, on constate que les sous-graphes extraits correspondent aux régions du cerveau impliquées dans la crise d'épilepsie. De plus l'évolution de l'activation de ces sous-graphes est cohérente avec l'interprétation visuelle

Canonical Polyadic Decomposition and Deep Learning for Machine Fault Detection

Acoustic monitoring for machine fault detection is a recent and expanding research path that has already provided promising results for industries. However, it is impossible to collect enough data to learn all types of faults from a machine. Thus, new algorithms, trained using data from healthy conditions only, were developed to perform unsupervised anomaly detection. A key issue in the development of these algorithms is the noise in the signals, as it impacts the anomaly detection performance. In this work, we propose a powerful data-driven and quasi non-parametric denoising strategy for spectral data based on a tensor decomposition: the Non-negative Canonical Polyadic (CP) decomposition. This method is particularly adapted for machine emitting stationary sound. We demonstrate in a case study, the Malfunctioning Industrial Machine Investigation and Inspection (MIMII) baseline, how the use of our denoising strategy leads to a sensible improvement of the unsupervised anomaly detection. Such approaches are capable to make sound-based monitoring of industrial processes more reliable

Fully learnable deep wavelet transform for unsupervised monitoring of high-frequency time series

High-frequency (HF) signals are ubiquitous in the industrial world and are of great use for monitoring of industrial assets. Most deep-learning tools are designed for inputs of fixed and/or very limited size and many successful applications of deep learning to the industrial context use as inputs extracted features, which are a manually and often arduously obtained compact representation of the original signal. In this paper, we propose a fully unsupervised deep-learning framework that is able to extract a meaningful and sparse representation of raw HF signals. We embed in our architecture important properties of the fast discrete wavelet transform (FDWT) such as 1) the cascade algorithm; 2) the conjugate quadrature filter property that links together the wavelet, the scaling, and transposed filter functions; and 3) the coefficient denoising. Using deep learning, we make this architecture fully learnable: Both the wavelet bases and the wavelet coefficient denoising become learnable. To achieve this objective, we propose an activation function that performs a learnable hard thresholding of the wavelet coefficients. With our framework, the denoising FDWT becomes a fully learnable unsupervised tool that does not require any type of pre- or postprocessing or any prior knowledge on wavelet transform. We demonstrate the benefits of embedding all these properties on three machine-learning tasks performed on open-source sound datasets. We perform an ablation study of the impact of each property on the performance of the architecture, achieve results well above baseline, and outperform other state-of-the-art methods.ISSN:0027-8424ISSN:1091-649

Slab Track Condition Monitoring Based on Learned Sparse Features from Acoustic and Acceleration Signals

The implementation of concrete slab track solutions has been recently increasing particularly for high-speed lines. While it is typically associated with low periodic maintenance, there is a significant need to detect the state of slab tracks in an efficient way. Data-driven detection methods are promising. However, collecting large amounts of labeled data is particularly challenging since abnormal states are rare for such safety-critical infrastructure. To imitate different healthy and unhealthy states of slab tracks, this study uses three types of slab track supporting conditions in a railway test line. Acceleration sensors (contact) and acoustic sensors (contactless), are installed next to the three types of slab track to collect the acceleration and acoustic signals as a train passes by with different speeds. We use a deep learning framework based on the recently proposed Denoising Sparse Wavelet Network (DeSpaWN) to automatically learn meaningful and sparse representations of raw high-frequency signals. A comparative study is conducted among the feature learning / extraction methods, and between acceleration signals and acoustic signals, by evaluating the detection effectiveness using a multi-class support vector machine. It is found that the classification accuracy using acceleration signals can reach almost 100%, irrespective which feature learning / extraction method is adopted. Due to the more severe noise interference in acoustic signals, the performance of using acoustic signals is worse than of using acceleration signals. However, it can be significantly improved by leaning meaningful features with DeSpaWN

Sparse tensor dimensionality reduction with application to clustering of functional connectivity

International audienceFunctional connectivity (FC) is a graph-like data structure commonly used by neuroscientists to study the dynamic behaviour of the brain activity. However, these analyses rapidly become complex and time-consuming. In this work, we present complementary empirical results on two tensor decomposition previously proposed named modified High Order Orthogonal Iteration (mHOOI) and High Order sparse Singular Value Decomposition (HOsSVD). These decompositions associated to k-means were shown to be useful for the study of multi trial functional connectivity dataset

Extraction of functional dynamic networks describing patient's epileptic seizures

International audienceIntracranial EEG studies using stereotactic EEG (SEEG) have shown that during seizures, epileptic activity spreads across several anatomical regions from the seizure onset zone towards remote brain areas. This appears like patient-specific time-varying networks that has to be extracted and characterised. Functional Connectivity (FC) analysis of SEEG signals recorded during seizures enables to describe the statistical relations between all pairs of recorded signals. However, extracting meaningful information from those large datasets is time-consuming and requires high expertise. In the present study [1], we propose a novel method named Brain-wide Time-varying Network Decomposition (BTND) to characterise the dynamic epileptogenic networks activated during seizures in individual patients recorded with SEEG electrodes. The method provides a number of pathological FC subgraphs with their temporal course of activation. The method can be applied to several seizures of the patient to extract reproducible subgraphs. To validate the extraction, we compare the activated subgraphs obtained by BTND to interpretation of SEEG signals recorded in 27 seizures from 9 different patients. We a found a good agreement about the activated subgraphs and the corresponding brain regions involved during the seizures and their activation dynamics

Extraction of functional dynamic networks describing patient's epileptic seizures

International audienceIntracranial EEG studies using stereotactic EEG (SEEG) have shown that during seizures, epileptic activity spreads across several anatomical regions from the seizure onset zone towards remote brain areas. This appears like patient-specific time-varying networks that has to be extracted and characterised. Functional Connectivity (FC) analysis of SEEG signals recorded during seizures enables to describe the statistical relations between all pairs of recorded signals. However, extracting meaningful information from those large datasets is time-consuming and requires high expertise. In the present study [1], we propose a novel method named Brain-wide Time-varying Network Decomposition (BTND) to characterise the dynamic epileptogenic networks activated during seizures in individual patients recorded with SEEG electrodes. The method provides a number of pathological FC subgraphs with their temporal course of activation. The method can be applied to several seizures of the patient to extract reproducible subgraphs. To validate the extraction, we compare the activated subgraphs obtained by BTND to interpretation of SEEG signals recorded in 27 seizures from 9 different patients. We a found a good agreement about the activated subgraphs and the corresponding brain regions involved during the seizures and their activation dynamics