Increasing the robustness of autonomous systems to hardware degradation using machine learning

Autonomous systems perform predetermined tasks (missions) with minimum supervision. In most applications, the state of the world changes with time. Sensors are employed to measure part or whole of the world’s state. However, sensors often fail amidst operation; feeding as such decision-making with wrong information about the world. Moreover, hardware degradation may alter dynamic behaviour, and subsequently the capabilities, of an autonomous system; rendering the original mission infeasible. This thesis applies machine learning to yield powerful and robust tools that can facilitate autonomy in modern systems. Incremental kernel regression is used for dynamic modelling. Algorithms of this sort are easy to train and are highly adaptive. Adaptivity allows for model adjustments, whenever the environment of operation changes. Bayesian reasoning provides a rigorous framework for addressing uncertainty. Moreover, using Bayesian Networks, complex inference regarding hardware degradation can be answered. Specifically, adaptive modelling is combined with Bayesian reasoning to yield recursive estimation algorithms that are robust to sensor failures. Two solutions are presented by extending existing recursive estimation algorithms from the robotics literature. The algorithms are deployed on an underwater vehicle and the performance is assessed in real-world experiments. A comparison against standard filters is also provided. Next, the previous algorithms are extended to consider sensor and actuator failures jointly. An algorithm that can detect thruster failures in an Autonomous Underwater Vehicle has been developed. Moreover, the algorithm adapts the dynamic model online to compensate for the detected fault. The performance of this algorithm was also tested in a real-world application. One step further than hardware fault detection, prognostics predict how much longer can a particular hardware component operate normally. Ubiquitous sensors in modern systems render data-driven prognostics a viable solution. However, training is based on skewed datasets; datasets where the samples from the faulty region of operation are much fewer than the ones from the healthy region of operation. This thesis presents a prognostic algorithm that tackles the problem of imbalanced (skewed) datasets

Adaptive locally linear kinematic modelling of concentric tube robots

Concentric tube robots comprise telescopic precurved elastic tubes. The robot's tip and shape are controlled via relative tube motions, i.e. tube rotations and translations. Non-linear interactions between the tubes, e.g. friction and torsion, as well as uncertainty in the physical properties of the tubes themselves, e.g. the Young’s modulus, curvature, or stiffness, hinder accurate kinematic modelling. In this paper, we present a machine-learning-based methodology for kinematic modelling of concentric tube robots and in situ model adaptation. Our approach is based on Locally Weighted Projection Regression (LWPR). The model comprises an ensemble of linear models, each of which locally approximates the original complex kinematic relation. LWPR can accommodate for model deviations by adjusting the respective local models at run-time, resulting in an adaptive kinematics framework. We evaluated our approach on data gathered from a three-tube robot, and report high accuracy across the robot's configuration space

Autonomous robotic intracardiac catheter navigation using haptic vision

International audienceWhile all minimally invasive procedures involve navigating from a small incision in the skin to the site of the intervention, it has not been previously demonstrated how this can be done 10 autonomously. To show that autonomous navigation is possible, we investigated it in the hardest place to do it-inside the beating heart. We created a robotic catheter that can navigate through the blood-filled heart using wall-following algorithms inspired by positively thigmotactic animals. The catheter employs haptic vision, a hybrid sense using imaging for both touch-based surface identification and force sensing, to accomplish wall following inside the blood-filled heart. 15 Through in vivo animal experiments, we demonstrate that the performance of an autonomously-controlled robotic catheter rivals that of an experienced clinician. Autonomous navigation is a fundamental capability on which more sophisticated levels of autonomy can be built, e.g., to perform a procedure. Similar to the role of automation in fighter aircraft, such capabilities can free the clinician to focus on the most critical aspects of the procedure while providing precise and 20 repeatable tool motions independent of operator experience and fatigue

Evaluating burnout syndrome among medical students at the Aristotle University of Thessaloniki in Greece: a cross-sectional study

IntroductionBurnout syndrome was first evaluated in the working environment of pilots and air-traffic controllers in 1973 and was officially described in scientific terms by the psychologist Christina Maslach. Recent research proves that the syndrome is currently present among healthcare professionals worldwide. Thus, we investigated whether it is also present in the medical student community, which faces the main characteristics of the syndrome from the beginning of their educational career.Materials and methodsThe research was conducted on a sample of 400 Greek medical students at Aristotle University of Thessaloniki, using the Maslach Basic Inventory questionnaire with three sections: exhaustion, depersonalization, and low satisfaction with personal achievements. The sample was analyzed based on the parameters of gender and the year of study of each individual participant.ResultsIn total, 33.5% of the participants were found to have a high risk or tendency for burnout syndrome, 11.75% of whom were at high risk and suffered from the syndrome. Moreover, 21.75% of the participants had a tendency toward suffering the syndrome. No remarkable correlation was discovered for the gender variable, whereas, for the year of study, there was an important correlation between the more senior years (5th and 6th) and higher risk.DiscussionThe syndrome’s prevalence from the survey is scientifically important, urging the academic community to examine whether, instead of shaping healthy doctors, in reality, the education system produces patients with the syndrome. Protective measures include cognitive-behavioral therapy, mindfulness, the six-stage adult learning technique, periodical screening of the syndrome, as well as encouragement for higher personal achievements

The workers of tourism: trade union struggles and biographical trajectories

This thesis examines the touristic phenomenon through the lens of workers, particularly by analyzing the organized labor union actions of the Hotel Workers Union (HWU) on the island of Corfu. The study delves into the challenges faced by the HWU and the life stories of its active members from 1974 to 1990.The first research question examines the formation of trade union identities within the Hotel Workers Union during two key sub-periods of Metapolitefsi: (a) the democratization period (1974-1981) and (b) the institutionalization period (1981-1990). Through archival research, we aim to trace changes in trade union demands, the adoption of different collective action repertoires, and the framing of trade union activities, all while exploring the evolving self-image of hotel workers in each sub-period. The second research question explores the factors driving the activation and deactivation of trade union participation among hotel workers in Corfu during the study period. We conducted in-depth analyses of 23 life stories from active union members to uncover how their personal experiences, work histories in the hotel industry, and the broader historical, social, and political context influenced their engagement in organized trade union activities. Through a combination of research conducted in the union's archives, interviews, and a biographical approach, our study examined the dynamics of the tourism industry as a contested arena where employers and organized labor compete for benefits from tourism development. This research contributes to shedding light on labor relations within the tourism sector, often depicted as having either absent or invisible exploitative relations. Additionally, our investigation of trade union struggles and the life trajectories of HWU members revealed how tourism served as a mechanism for shaping social consensus in Greek society during the Metapolitefsi period.Η διατριβή θέτει ως γενικό της στόχο τη προσέγγιση του τουριστικού φαινόμενου μέσα από την οπτική των εργαζομένων στον τουρισμό, και πιο συγκεκριμένα μέσα από τη μελέτη της οργανωμένης συνδικαλιστικής δράσης των εργαζομένων στα ξενοδοχεία. Η μελέτη εστιάζει στη συνδικαλιστική δράση του Συνδέσμου Ξενοδοχοϋπαλλήλων Κέρκυρας και στις ιστορίες ζωής των ενεργών μελών του από το 1974 έως το 1990. Το πρώτο ερευνητικό ερώτημα που εξετάζεται αφορά τη διερεύνηση των συνδικαλιστικών ταυτοτήτων που παράχθηκαν και χαρακτήρισαν τον Σύνδεσμο Ξενοδοχοϋπαλλήλων Κέρκυρας σε κάθε μια από τις υποπεριόδους της μεταπολίτευσης: (α) κατά την περίοδο του εκδημοκρατισμού του Συνδέσμου Ξενοδοχοϋπαλλήλων Κέρκυρας (1974-1981) και β) κατά την περίοδο της θεσμοποίησης του σωματείου (1981-1990). Στη βάση της παραπάνω περιοδολόγησης επιχειρείται, μέσα από την αρχειακή έρευνα, να αποτυπωθούν οι μεταβολές ως προς το περιεχόμενο των συνδικαλιστικών αιτημάτων, τα ρεπερτόρια της δράσης καθώς και τη νοηματική πλαισίωση της συνδικαλιστικής δράσης, που χαρακτήριζαν την κάθε υποπερίοδο. Το δεύτερο ερευνητικό ερώτημα αφορά τους λόγους και τα κίνητρα της συνδικαλιστικής ενεργοποίησης και αδρανοποίησης των εργαζομένων στα ξενοδοχεία της Κέρκυρας, που παρατηρήθηκε κατά τη διάρκεια του εξεταζόμενου χρονικού διαστήματος. Μελετήθηκαν, συγκεκριμένα, 23 καταγεγραμμένες ιστορίες ζωής πρωταγωνιστών της συνδικαλιστικής δράσης, για να αποσαφηνιστούν οι διαδικασίες με τις οποίες οι εμπειρίες που εμπεριέχονταν στο βιογραφικό απόθεμα των υποκειμένων καθώς και οι εργασιακές τους εμπειρίες στις επιχειρήσεις του τουρισμού, εμπλαισιωμένες στο ιστορικό, κοινωνικό και πολιτικό συγκείμενο, αποτέλεσαν το ευνοϊκό υπόστρωμα για την ανάληψη οργανωμένης συνδικαλιστικής δράσης. Η συνδυαστική έρευνα στο αρχείο του σωματείου (και στις υπόλοιπες αρχειακές πηγές), παράλληλα με την αξιοποίηση των συνεντεύξεων και της βιογραφικής προσέγγισης, αφενός επέτρεψε την εξέταση του τουριστικού φαινομένου ως ενός πεδίου κοινωνικού ανταγωνισμού μεταξύ εργοδοσίας και οργανωμένης εργασίας για τη διεκδίκηση περισσότερων ωφελημάτων από την τουριστική ανάπτυξη. Με αυτό τον τρόπο, η διατριβή θέλησε να συνεισφέρει στην απομάγευση της εργασίας στον τουρισμό, που συχνά παρουσιάζεται ως ένας κλάδος εντός του οποίου οι σχέσεις εκμετάλλευσης είτε απουσιάζουν είτε είναι αόρατες. Αφετέρου, η διερεύνηση των συνδικαλιστικών αγώνων και των βιογραφικών διαδρομών των ενεργών μελών του ΣΞΚ, αποκάλυψε επιπλέον και όψεις της λειτουργίας του τουρισμού ως μηχανισμού παραγωγής κοινωνικής συναίνεσης στην ελληνική κοινωνία τη μεταπολιτευτική περίοδο

Novel RUL prediction of assets based on the integration of auto-regressive models and an RUSBoost classifier

Abstract — This paper presents a novel, data-driven algorithm for the computation of the Remaining Useful Life (RUL) of an asset. The algorithm utilizes the asset’s state history to learn a prognostic model from data. The prognostic model comprises an ensemble of Auto-Regressive (AR) models, together with a state-of-the-art classifier. The AR part of the algorithm is used to predict the system’s state evolution. The classifier discriminates between healthy and faulty operation, given the asset’s current state. The predicted state, as computed by the AR model, is fed to the classifier. The first time when the predicted state is classified as faulty is returned as the RUL of the system. The resulting prognostic algorithm was tested on the CMAPSS dataset as provided from NASA Ames Research Center. Cases of unknown future input trajectory as well as cases with multiple faults have been investigated. I