A Survey on Reachable Set Techniques for Fault Recoverability Assessment

The development of any fault-tolerant control solution is based on the strong assumption that fault situations can be accommodated. This paper provides a survey of four reachable set techniques to assess the fault recoverability property for constrained linear time invariant (LTI) systems by means of ellipsoid, zonotope, polytope and support function representations. These techniques are next applied to an angular velocity spacecraft model. A discussion is finally made to assess the computational complexity for the four algorithms

A Data-Driven Clustering Method for Discovering Profiles in the Dynamics of Major Depressive Disorder Using a Smartphone-Based Ecological Momentary Assessment of Mood.

BACKGROUND: Although major depressive disorder (MDD) is characterized by a pervasive negative mood, research indicates that the mood of depressed patients is rarely entirely stagnant. It is often dynamic, distinguished by highs and lows, and it is highly responsive to external and internal regulatory processes. Mood dynamics can be defined as a combination of mood variability (the magnitude of the mood changes) and emotional inertia (the speed of mood shifts). The purpose of this study is to explore various distinctive profiles in real-time monitored mood dynamics among MDD patients in routine mental healthcare. METHODS: Ecological momentary assessment (EMA) data were collected as part of the cross-European E-COMPARED trial, in which approximately half of the patients were randomly assigned to receive the blended Cognitive Behavioral Therapy (bCBT). In this study a subsample of the bCBT group was included (n = 287). As part of bCBT, patients were prompted to rate their current mood (on a 1-10 scale) using a smartphone-based EMA application. During the first week of treatment, the patients were prompted to rate their mood on three separate occasions during the day. Latent profile analyses were subsequently applied to identify distinct profiles based on average mood, mood variability, and emotional inertia across the monitoring period. RESULTS: Overall, four profiles were identified, which we labeled as: (1) "very negative and least variable mood" (n = 14) (2) "negative and moderate variable mood" (n = 204), (3) "positive and moderate variable mood" (n = 41), and (4) "negative and highest variable mood" (n = 28). The degree of emotional inertia was virtually identical across the profiles. CONCLUSIONS: The real-time monitoring conducted in the present study provides some preliminary indications of different patterns of both average mood and mood variability among MDD patients in treatment in mental health settings. Such varying patterns were not found for emotional inertia

Examining the Theoretical Framework of Behavioral Activation for Major Depressive Disorder: Smartphone-Based Ecological Momentary Assessment Study.

BACKGROUND: Behavioral activation (BA), either as a stand-alone treatment or as part of cognitive behavioral therapy, has been shown to be effective for treating depression. The theoretical underpinnings of BA derive from Lewinsohn et al's theory of depression. The central premise of BA is that having patients engage in more pleasant activities leads to them experiencing more pleasure and elevates their mood, which, in turn, leads to further (behavioral) activation. However, there is a dearth of empirical evidence about the theoretical framework of BA. OBJECTIVE: This study aims to examine the assumed (temporal) associations of the 3 constructs in the theoretical framework of BA. METHODS: Data were collected as part of the "European Comparative Effectiveness Research on Internet-based Depression Treatment versus treatment-as-usual" trial among patients who were randomly assigned to receive blended cognitive behavioral therapy (bCBT). As part of bCBT, patients completed weekly assessments of their level of engagement in pleasant activities, the pleasure they experienced as a result of these activities, and their mood over the course of the treatment using a smartphone-based ecological momentary assessment (EMA) application. Longitudinal cross-lagged and cross-sectional associations of 240 patients were examined using random intercept cross-lagged panel models. RESULTS: The analyses did not reveal any statistically significant cross-lagged coefficients (all P>.05). Statistically significant cross-sectional positive associations between activities, pleasure, and mood levels were identified. Moreover, the levels of engagement in activities, pleasure, and mood slightly increased over the duration of the treatment. In addition, mood seemed to carry over, over time, while both levels of engagement in activities and pleasurable experiences did not. CONCLUSIONS: The results were partially in accordance with the theoretical framework of BA, insofar as the analyses revealed cross-sectional relationships between levels of engagement in activities, pleasurable experiences deriving from these activities, and enhanced mood. However, given that no statistically significant temporal relationships were revealed, no conclusions could be drawn about potential causality. A shorter measurement interval (eg, daily rather than weekly EMA reports) might be more attuned to detecting potential underlying temporal pathways. Future research should use an EMA methodology to further investigate temporal associations, based on theory and how treatments are presented to patients. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02542891, https://clinicaltrials.gov/ct2/show/NCT02542891; German Clinical Trials Register, DRKS00006866, https://tinyurl.com/ybja3xz7; Netherlands Trials Register, NTR4962, https://www.trialregister.nl/trial/4838; ClinicalTrials.Gov, NCT02389660, https://clinicaltrials.gov/ct2/show/NCT02389660; ClinicalTrials.gov, NCT02361684, https://clinicaltrials.gov/ct2/show/NCT02361684; ClinicalTrials.gov, NCT02449447, https://clinicaltrials.gov/ct2/show/NCT02449447; ClinicalTrials.gov, NCT02410616, https://clinicaltrials.gov/ct2/show/NCT02410616; ISRCTN registry, ISRCTN12388725, https://www.isrctn.com/ISRCTN12388725

Effect of Sleep Disturbance Symptoms on Treatment Outcome in Blended Cognitive Behavioral Therapy for Depression (E-COMPARED Study): Secondary Analysis.

BACKGROUND: Sleep disturbance symptoms are common in major depressive disorder (MDD) and have been found to hamper the treatment effect of conventional face-to-face psychological treatments such as cognitive behavioral therapy. To increase the dissemination of evidence-based treatment, blended cognitive behavioral therapy (bCBT) consisting of web-based and face-to-face treatment is on the rise for patients with MDD. To date, no study has examined whether sleep disturbance symptoms have an impact on bCBT treatment outcomes and whether it affects bCBT and treatment-as-usual (TAU) equally. OBJECTIVE: The objectives of this study are to investigate whether baseline sleep disturbance symptoms have an impact on treatment outcomes independent of treatment modality and whether sleep disturbance symptoms impact bCBT and TAU in routine care equally. METHODS: The study was based on data from the E-COMPARED (European Comparative Effectiveness Research on Blended Depression Treatment Versus Treatment-as-Usual) study, a 2-arm, multisite, parallel randomized controlled, noninferiority trial. A total of 943 outpatients with MDD were randomized to either bCBT (476/943, 50.5%) or TAU consisting of routine clinical MDD treatment (467/943, 49.5%). The primary outcome of this study was the change in depression symptom severity at the 12-month follow-up. The secondary outcomes were the change in depression symptom severity at the 3- and 6-month follow-up and MDD diagnoses at the 12-month follow-up, assessed using the Patient Health Questionnaire-9 and Mini-International Neuropsychiatric Interview, respectively. Mixed effects models were used to examine the association of sleep disturbance symptoms with treatment outcome and treatment modality over time. RESULTS: Of the 943 patients recruited for the study, 558 (59.2%) completed the 12-month follow-up assessment. In the total sample, baseline sleep disturbance symptoms did not significantly affect change in depressive symptom severity at the 12-month follow-up (β=.16, 95% CI -0.04 to 0.36). However, baseline sleep disturbance symptoms were negatively associated with treatment outcome for bCBT (β=.49, 95% CI 0.22-0.76) but not for TAU (β=-.23, 95% CI -0.50 to 0.05) at the 12-month follow-up, even when adjusting for baseline depression symptom severity. The same result was seen for the effect of sleep disturbance symptoms on the presence of depression measured with Mini-International Neuropsychiatric Interview at the 12-month follow-up. However, for both treatment formats, baseline sleep disturbance symptoms were not associated with depression symptom severity at either the 3- (β=.06, 95% CI -0.11 to 0.23) or 6-month (β=.09, 95% CI -0.10 to 0.28) follow-up. CONCLUSIONS: Baseline sleep disturbance symptoms may have a negative impact on long-term treatment outcomes in bCBT for MDD. This effect was not observed for TAU. These findings suggest that special attention to sleep disturbance symptoms might be warranted when MDD is treated with bCBT. Future studies should investigate the effect of implementing modules specifically targeting sleep disturbance symptoms in bCBT for MDD to improve long-term prognosis

Contribution à la Commande Tolérante aux Défauts pour la Maitrise des Comportements Transitoires liés à une Accommodation: Des systèmes volants vers des dispositifs biomédicaux

After the success of SpaceX missions with the reuse of rockets involving a cost divided by two, the area of health management becomes crucial to guarantee system autonomy. To safe and reliable behaviors, the research on Fault Diagnosis (FD) and Fault Tolerant Control (FTC) fields has mainly been investigated. Despite plethoric published strategies, only few works try to take into account interactions between FD and FTC units, leading to questionable solutions for a reliable health management. This scientific document focusses on the development of solutions able to manage the FD and FTC interactions. More precisely, a particular attention is based on the mitigation of transient behaviors after a fault accommodation. After some norm-based solutions, the use of switching control or sliding mode theory has been investigated and assessed on academic examples. To bring the gap between academic works and industrial needs, some technology transfer activities are detailed and assessed with respect to the Technological Readiness Level (TRL) scale. Finally, some perspectives are given to highlight the important position of control researchers for the future societal challenges like a new artificial pancreas with an increased robustness against patient variability.Dans une course effreinée à l’industrialisation, les quelques dramatiques incidents nous alertent constament sur la nécessité de développer des solutions fiables et robustes à l’apparition d’une défaillance. Pour contrer la fréquence exponentielle de ces incidents, la commande tolérance aux défauts (FTC) est, petit à petit, devenue l’une des préoccupations majeures des systèmes automatisés complexes. Dans ce document scientifique, l’attention se porte sur le développement de méthodes de surveillance, d’approches FTC actives et de la maitrise de leurs interactions. Ce dernier axe de développement s’appuie sur le constat suivant : en dépit d’une interaction évidente entre les tâches de diagnostic et les actions correctives pour accommoder l’effet d’un défaut, ces deux domaines de recherche ont souvent été étudiés séparément, rendant leur fiabilité discutable. Après la présentation d’un curriculum détaillé, les premiers résultats basés sur des approches à base de normes, la théorie des systèmes commutés ou celle des modes glissants sont évalués sur des exemples académiques. Pour combler le fossé entre des travaux purement académiques et répondre aux besoins des industriels, des actions de transfert de technologie sont mis en avant et évaluer en utilisant l’échelle de maturité technologique développée par la NASA. Finallement, des perspectives de recherche sont avancées pour décloisonner, aux yeux du grand public, le métier d’automaticien et montrer son importante pour aborder les enjeux et défis sociétaux de demain

Analyse et synthèse d'une architecture coopérative pour la commande tolérante aux défauts - Application à un système aéronautique

Cette thèse porte sur une des préoccupations majeures dans la conception des systèmes automatisés : la tolérance aux défauts. L’interaction entre les tâches de surveillance et de reconfiguration de la loi de commande est examinée et un nouveau schéma coopératif est proposé pour la gestion globale des compromis. Cette architecture présente l’avantage de préserver entièrement les performances nominales (situation non défaillante) car la boucle de commande nominale est conservée au sein du schéma coopératif. Une procédure de synthèse basée sur la mise en oeuvre et l'évaluation des indicateurs de performance des modules de diagnostic et de commande, est proposée. Les résultats méthodologiques sont appliqués au modèle d'un avion gros porteur : le Boeing 747-100/200. Ce Benchmark a été établi par le groupe européen GARTEUR (AG16, Fault Tolerant Control) afin de comparer les méthodologies actives de la commande tolérante aux fautes avec les lois classiques de pilotage.This thesis discusses the design of an active Fault Tolerant Control (FTC) strategy for improvement of the operational control capability of the safety critical systems. The FTC strategy works in such a way that once a fault is detected by the Fault Detection and Isolation (FDI) unit, a compensation loop is activated for safe recovery. A key feature of the proposed strategy is that the design of the FTC loop is done independently of the nominal control law already in place. For a given application, one can select the appropriate “FTC controller / FDI unit” from the designed set of all admissible FDI/FTC units. The selection is done using performance indicators based on μ-analysis and μg-analysis. Finally, the proposed approach is applied to a faulty scenario of a realistic nonlinear benchmark of a large transport aircraft within European Flight Mechanics Action Group (FM-AG(16)) of GARTEUR program. The goal is to provide a “self-repairing” capability to enable the pilot to land the aircraft safely in the event of a stabilizer fault

ANALYSE ET SYNTHESE D'UNE ARCHITECTURE COOPERATIVE POUR LA COMMANDE TOLERANTE AUX DEFAUTS - APPLICATION A UN SYSTEME AERONAUTIQUE

This thesis discusses the design of an active Fault Tolerant Control (FTC) strategy for improvement of the operational control capability of the safety critical systems. The FTC strategy works in such a way that once a fault is detected by the Fault Detection and Isolation (FDI) unit, a compensation loop is activated for safe recovery. A key feature of the proposed strategy is that the design of the FTC loop is done independently of the nominal control law already in place. For a given application, one can select the appropriate “FTC controller / FDI unit” from the designed set of all admissible FDI/FTC units. The selection is done using performance indicators based on µ-analysis and µg-analysis. Finally, the proposed approach is applied to a faulty scenario of a realistic nonlinear benchmark of a large transport aircraft within European Flight Mechanics Action Group (FM-AG(16)) of GARTEUR program. The goal is to provide a “self-repairing” capability to enable the pilot to land the aircraft safely in the event of a stabilizer fault.Cette thèse porte sur une des préoccupations majeures dans la conception des systèmes automatisés : la tolérance aux défauts. L'interaction entre les tâches de surveillance et de reconfiguration de la loi de commande est examinée et un nouveau schéma coopératif est proposé pour la gestion globale des compromis. Cette architecture présente l'avantage de préserver entièrement les performances nominales (situation non défaillante) car la boucle de commande nominale est conservée au sein du schéma coopératif. Une procédure de synthèse basée sur la mise en œuvre et l'évaluation des indicateurs de performance des modules de diagnostic et de commande, est proposée. Les résultats méthodologiques sont appliqués au modèle d'un avion gros porteur : le Boeing 747-100/200. Ce Benchmark a été établi par le groupe européen GARTEUR (AG16, Fault Tolerant Control) afin de comparer les méthodologies actives de la commande tolérante aux fautes avec les lois classiques de pilotage

A Switching Fault-Hiding Mechanism based on Virtual Actuators and Dwell-Time Conditions

International audienceThe design of an active Fault Tolerant Control (FTC) strategy based on Virtual Actuators (VA) and switching control theory is addressed. More precisely, a bank of VA is introduced between the baseline controller and the plant to hide and accommodate the fault. If the proposed solution possesses the advantage to maintain the baseline – and potentially certified – controller, it is also assumed here to keep the analytical diagnosis filters – potentially certified too – that monitor the plant. The problem is next formulated in the context of supervisory control where the cases of intermittent and abrupt faults can be covered. It is shown how a separation principle can be found to guarantee the closed loop stability of the overall switching system by using dwell-time conditions. Finally, the proposed solution is applied to the HiMAT benchmark

Introduction of a Prognostic Decision Making in a Fault Tolerant Control Context

International audienceThe paper deals with the design of an enhanced active Fault Tolerant Control (FTC) scheme based on the concept of supervisory control for uncertain Linear Time Invariant (LTI) systems. The improvement lies on the introduction of a Prognostic Decision Making (PDM) unit and a Virtual Fault Mechanism (VFM) in the supervisory FTC setup. The main purpose is to forecast the switching control thanks to the fault prediction to better mitigate the reconfiguration transients, while exponential stability is guaranteed by the dwell-time conditions. Since the diagnosis task is maintained in FTC setup to safely react to unforeseeable events, the solution proposes a structure where diagnosis, prognostic and accommodation tasks can work together in harmony. This work is applied to the academic aeronautical benchmark to highlight its potential

Transient management of a supervisory fault-tolerant control scheme based on dwell-time conditions

International audienceThe paper deals with the design of an active fault-tolerant control strategy based on the supervisory control approach technique for linear time invariant MIMO systems affected by disturbances, measurement noise, and faults. From a bank of Luenberger observers that plays the role of a fault detection and isolation scheme, the supervisory algorithm aims at selecting the suitable fault-tolerant controller by means of a hysteresis-based switching mechanism. Based on dwell-time conditions, Lyapunov global exponential stability is addressed, and it is shown how transient behaviors due to the inherent interactions between fault detection and isolation, fault-tolerant control, and the reconfiguration mechanism can be improved. The main advantage with respect to existing solutions of open literature is relative to a simple parameterization of all controllers (possibly having different state dimensions, integral action, and/or unstable poles) in order to cope with bumps and undesirable transients when (possible multiple) switches occur. Moreover, it is shown that it is possible to improve (reduce) the dwell-time value in some cases. The efficiency of the approach is demonstrated on the academic highly maneuverable technology benchmark