Non-Destructive Techniques for the Condition and Structural Health Monitoring of Wind Turbines: A Literature Review of the Last 20 Years

A complete surveillance strategy for wind turbines requires both the condition monitoring (CM) of their mechanical components and the structural health monitoring (SHM) of their load-bearing structural elements (foundations, tower, and blades). Therefore, it spans both the civil and mechanical engineering fields. Several traditional and advanced non-destructive techniques (NDTs) have been proposed for both areas of application throughout the last years. These include visual inspection (VI), acoustic emissions (AEs), ultrasonic testing (UT), infrared thermography (IRT), radiographic testing (RT), electromagnetic testing (ET), oil monitoring, and many other methods. These NDTs can be performed by human personnel, robots, or unmanned aerial vehicles (UAVs); they can also be applied both for isolated wind turbines or systematically for whole onshore or offshore wind farms. These non-destructive approaches have been extensively reviewed here; more than 300 scientific articles, technical reports, and other documents are included in this review, encompassing all the main aspects of these survey strategies. Particular attention was dedicated to the latest developments in the last two decades (2000–2021). Highly influential research works, which received major attention from the scientific community, are highlighted and commented upon. Furthermore, for each strategy, a selection of relevant applications is reported by way of example, including newer and less developed strategies as well

The extreme function theory for damage detection: An application to civil and aerospace structures

Any damaged condition is a rare occurrence for mechanical systems, as it is very unlikely to be observed. Thus, it represents an extreme deviation from the median of its probability distribu-tion. It is, therefore, necessary to apply proper statistical solutions, i.e., Rare Event Modelling (REM). The classic tool for this aim is the Extreme Value Theory (EVT), which deals with uni-or multivariate scalar values. The Extreme Function Theory (EFT), on the other hand, is defined by enlarging the fundamental EVT concepts to whole functions. When combined with Gaussian Process Regres-sion (GPR), the EFT is perfectly suited for mode shape-based outlier detection. In fact, it is possible to investigate the structure’s normal modes as a whole rather than focusing on their constituent data points, with quantifiable advantages. This provides a useful tool for Structural Health Monitoring, especially to reduce false alarms. This recently proposed methodology is here tested and validated both numerically and experimentally for different examples coming from Civil and Aerospace Engineering applications. One-dimensional beamlike elements with several boundary conditions are considered, as well as a two-dimensional plate-like spar and a frame structure

Transformative social innovation in developing and emerging ecosystems: a configurational examination

Despite the literature on social innovation (SI) in ecosystems growing considerably in recent years, what makes an ecosystem a facilitator for transformative SI remains unexamined, particularly indeveloping and emerging countries. Our research aims to fill this literature gap by determining which combination of characteristics-stemming from stakeholder theory and knowledge management-turns local smallholder coffee farmers in developing and emerging producing countries into autonomous and empowered partners and catalysts for spreading SI initiatives locally. We adopt a configurational approach using fuzzy-set qualitative comparative analysis of 18 SI projects that coffee MNEs, nongovernmental organizations, and institutions have undertaken to favor such an egalitarian value co-creation with local stakeholders. We demonstrate that stakeholder empowerment, cooperative strategic posturing, knowledge transfer, and local knowledge exchange are necessary conditions within the ecosystem to create local autonomy as an antecedent for transformative SI. The novelty in our approach lies in proposing a shift from a pure firm-centric perspective based on stakeholder dependence to a more participatory relational perspective that entails lower-power stakeholders' interdependence and collaboration for autonomous decision-making, thereby advancing fresh thinking on stakeholder and knowledge management applied to SI in developing and emerging contexts. We also propose practical suggestions to deal with stakeholder power's imbalances, which might limit the ecosystems' adaptation toward transformative SI

Incremental Learning of Object Models From Natural Human-Robot Interactions

In order to perform complex tasks in realistic human environments, robots need to be able to learn new concepts in the wild, incrementally, and through their interactions with humans. This article presents an end-to-end pipeline to learn object models incrementally during the human-robot interaction (HRI). The pipeline we propose consists of three parts: 1) recognizing the interaction type; 2) detecting the object that the interaction is targeting; and 3) learning incrementally the models from data recorded by the robot sensors. Our main contributions lie in the target object detection, guided by the recognized interaction, and in the incremental object learning. The novelty of our approach is the focus on natural, heterogeneous, and multimodal HRIs to incrementally learn new object models. Throughout the article, we highlight the main challenges associated with this problem, such as high degree of occlusion and clutter, domain change, low-resolution data, and interaction ambiguity. This article shows the benefits of using multiview approaches and combining visual and language features, and our experimental results outperform standard baselines

A novel approach to damage localisation based on bispectral analysis and neural network

The normalised version of bispectrum, the so-called bicoherence, has often proved a reliable method of damage detection on engineering applications. Indeed, higher-order spectral analysis (HOSA) has the advantage of being able to detect non-linearity in the structural dynamic response while being insensitive to ambient vibrations. Skewness in the response may be easily spotted and related to damage conditions, as the majority of common faults and cracks shows bilinear effects. The present study tries to extend the application of HOSA to damage localisation, resorting to a neural network based classification algorithm. In order to validate the approach, a non-linear finite element model of a 4-meters-long cantilever beam has been built. This model could be seen as a first generic concept of more complex structural systems, such as aircraft wings, wind turbine blades, etc. The main aim of the study is to train a Neural Network (NN) able to classify different damage locations, when fed with bispectra. These are computed using the dynamic response of the FE nonlinear model to random noise excitation

A Library Approach to the Development of BenzaPhos, Highly Efficient Chiral Supramolecular Ligands for Asymmetric Hydrogenation

A library of chiral supramolecular ligands named BenzaPhos, of straightforward preparation (two steps from commercial or readily available starting materials) and modular structure, was designed and synthesized. The ligands were screened in the search of new rhodium catalysts for the enantioselective hydrogenation of several benchmark and industrially relevant substrates. Once a series of hits were identified, structural modifications were introduced on three of the best ligands and a small second-generation library was created. Members of the latter showed outstanding levels of activity and enantioselectivity in the hydrogenation of challenging olefins such as enamide S4 and beta-dehydroamino ester S5 (> 99% ee: best value ever reported in both cases). A series of control experiments were undertaken in order to clarify the role of hydrogen bonding in determining the catalytic properties of the new ligands. The results of these experiments, together with those of computational studies carried out on four dihydride complexes involved in the catalytic hydrogenation of substrate S4, strongly suggest that a substrate orientation takes place in the catalytic cycle by formation of a hydrogen bond between the ligand amide oxygen and the substrate amide NH

La proyección de la imagen de Benedicto XVI por parte del diario El País: una reflexión sobre ética periodística a la luz de la ética empresarial

Journalistic ethics and business ethics have more in common than has been traditionally recognized. Thus, based on a sample of the informative treatment of Benedict XVI’s pontificate by a generalist newspaper -a reference newspaper in Spain-, some of the challenges that the former should address are proposed, considering the examination of the ideas offered by those who operate from the perspective of organizations.La ética periodística y la ética empresarial tienen más en común de lo que se ha reconocido tradicionalmente. Así, a partir de una muestra del tratamiento informativo realizado por un diario generalista -referente en España- al pontificado de Benedicto XVI, se proponen algunos de los retos a los que debe atender la primera, considerando el examen de las ideas ofrecidas por quienes operan desde la perspectiva de las organizaciones

MULTI OPTICAL TRANSITION RADIATION SYSTEM FOR ATF2 ∗

In this paper we describe the design, installation and first calibration tests of a Multi Optical Transition Radiation System in the beam diagnostic section of the Extraction (EXT) line of ATF2, close to the multi wire scanner system. This system will be a valuable tool for measuring beam sizes and emittances coming from the ATF Damping Ring. With an optical resolution of about 2μm an original OTR design (OTR1X) located after the septum at the entrance of the EXT line demonstrated the ability to measure a5.5μm beam size in one beam pulse and to take many fast measurements. This gives the OTR the ability to measure the beam emittance with high statistics, giving a low error and a good understanding of emittance jitter. Furthermore the nearby wire scanners will be a definitive test of the OTR as a beam emittance diagnostic device. The multi-OTR system design proposed here is based on the existing OTR1X

An Experimental Validation of Phase-Based Motion Magnification for Structures with Developing Cracks and Time-Varying Configurations

In this study, Computer Vision and Phase-Based Motion Magnification (PBMM) are validated for continuous Structural Health Monitoring (SHM) purposes. The aim is to identify the exact instant of occurrence for damage or abrupt structural changes from video-extracted, very low amplitude (barely visible) vibrations. The study presents three experimental datasets: a box beam with multiple saw cuts of different lengths and angles, a beam with a full rectangular cross section and a mass added at the tip, and the spar of a prototype High-Aspect-Ratio wing. Both mode-shape- and frequency-based approaches are considered, showing the potential to identify the severity and position of the damage as well A high-definition, high-speed camera and a low-cost commercial alternative have been successfully utilised for these video acquisitions. Finally, the technique is also preliminarily tested for outdoor applications with smartphone cameras