69 research outputs found

    Failure Prognosis of Wind Turbine Components

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    Wind energy is playing an increasingly significant role in the World\u27s energy supply mix. In North America, many utility-scale wind turbines are approaching, or are beyond the half-way point of their originally anticipated lifespan. Accurate estimation of the times to failure of major turbine components can provide wind farm owners insight into how to optimize the life and value of their farm assets. This dissertation deals with fault detection and failure prognosis of critical wind turbine sub-assemblies, including generators, blades, and bearings based on data-driven approaches. The main aim of the data-driven methods is to utilize measurement data from the system and forecast the Remaining Useful Life (RUL) of faulty components accurately and efficiently. The main contributions of this dissertation are in the application of ALTA lifetime analysis to help illustrate a possible relationship between varying loads and generators reliability, a wavelet-based Probability Density Function (PDF) to effectively detecting incipient wind turbine blade failure, an adaptive Bayesian algorithm for modeling the uncertainty inherent in the bearings RUL prediction horizon, and a Hidden Markov Model (HMM) for characterizing the bearing damage progression based on varying operating states to mimic a real condition in which wind turbines operate and to recognize that the damage progression is a function of the stress applied to each component using data from historical failures across three different Canadian wind farms

    Condition-Based Maintenance of HVAC on a High-Speed Train for Fault Detection

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    Reliability-centered maintenance (RCM) is a well-established method for preventive maintenance planning. This paper focuses on the optimization of a maintenance plan for an HVAC (heating, ventilation and air conditioning) system located on high-speed trains. The first steps of the RCM procedure help in identifying the most critical items of the system in terms of safety and availability by means of a failure modes and effects analysis. Then, RMC proposes the optimal maintenance tasks for each item making up the system. However, the decision-making diagram that leads to the maintenance choice is extremely generic, with a consequent high subjectivity in the task selection. This paper proposes a new fuzzy-based decision-making diagram to minimize the subjectivity of the task choice and preserve the cost-efficiency of the procedure. It uses a case from the railway industry to illustrate the suggested approach, but the procedure could be easily applied to different industrial and technological fields. The results of the proposed fuzzy approach highlight the importance of an accurate diagnostics (with an overall 86% of the task as diagnostic-based maintenance) and condition monitoring strategy (covering 54% of the tasks) to optimize the maintenance plan and to minimize the system availability. The findings show that the framework strongly mitigates the issues related to the classical RCM procedure, notably the high subjectivity of experts. It lays the groundwork for a general fuzzy-based reliability-centered maintenance method.This research received no external fundin

    Incorporating fuzzy-based methods to deep learning models for semantic segmentation

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    This thesis focuses on improving the workflow of semantic segmentation through a combination of reducing model complexity, improving segmentation accuracy, and making semantic segmentation results more reliable and robust. Semantic segmentation refers to pixel-level classification, the objective of which is to classify each pixel of the input image into different categories. The process typically consists of three steps: model construction, training, and application. Thus, in this thesis, fuzzy-based techniques are utilized in the aforementioned three steps to improve semantic segmentation workflow . The widely-used semantic segmentation models normally extract and aggregate spatial information and channel-wise features simultaneously. In order to achieve promising segmentation performance, it is required to involve numerous learnable parameters, which increase the model's complexity. Thus, decoupling the information fusion tasks is an important approach in the exploration of semantic segmentation models. Fuzzy integrals are effective for fusing information, and some special fuzzy integral operators (OWA) are free of parameters and easy to implement in deep-learning models. Therefore, a novel fuzzy integral module that includes an additional convolutional layer for feature map dimensionality reduction and an OWA layer for information fusion across feature channels is designed. The proposed fuzzy integral module can be flexibly integrated into existing semantic segmentation models, and then help reduce parameters and save memory. Following the exploration of semantic segmentation models, the collected data is used to train the model. Note that the precise delineation of object boundaries is a key aspect of semantic segmentation. In order to make the segmentation model pay more attention to the boundary, a special boundary-wise loss function is desirable in the segmentation model training phase. Fuzzy rough sets are normally utilized to measure the relationship between two sets. Thus, in this thesis, to improve the boundary accuracy, fuzzy rough sets are leveraged to calculate a boundary-wise loss, which is the difference between the boundary sets of the predicted image and the ground truth image. After completing the training process with the proposed novel loss, the next step for semantic segmentation is to apply the pre-trained segmentation model to segment new images. One challenge is that there are no ground truth images to quantify the segmentation quality in the real-world application of semantic segmentation models. Therefore, it is crucial to design a quality quantification algorithm to infer image-level segmentation performance and improve the credibility of semantic segmentation models. In this thesis, a novel quality quantification algorithm based on fuzzy uncertainty is proposed as part of the model inference process without accessing ground truth images. Moreover, to further explore the practical application of the proposed quality quantification algorithm in clinical settings, this thesis goes beyond public datasets and delves into a real-world case study involving cardiac MRI segmentation. Additionally, as clinicians also provide the level of uncertainty to measure their confidence when annotating to generate ground truth images (human-based uncertainty), the correlation between human-based uncertainty and AI-based uncertainty (calculated by the proposed quality quantification algorithm) is deeply investigated. Comprehensive experiments are conducted in this thesis to demonstrate that the integration of fuzzy-based technologies can enhance the efficiency, accuracy, and reliability of semantic segmentation models compared to those without such methods

    Validation and Improvement of Reliability Methods for Air Force Building Systems

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    The United States Air Force manages its civil infrastructure resource allocation via a two-dimensional risk model consisting of the consequence of failure and reliability. Air Force civil engineers currently use the BUILDER® Sustainment Management System to estimate and predict reliability at multiple levels within its civil infrastructure systems. Alley (2015) developed and validated a probabilistic model to calculate reliability at the system level. The probabilistic model was found to be a significant improvement over the currently employed BUILDER® model for four major building systems (electrical, HVAC, fire protection, and electrical). This research assessed the performance and accuracy of both the probabilistic and BUILDER® model, focusing primarily on HVAC systems. This research used contingency analysis to assess the performance of each model for HVAC systems at six Air Force installations. Evaluating the contingency analysis results over the range of possible reliability thresholds, it was found that both the BUILDER® and probabilistic model produced inflated reliability calculations for HVAC systems. In light of these findings, this research employed a stochastic method, a Nonhomogenious Poisson Process (NHPP), in an attempt to produce accurate HVAC system reliability calculations. This effort ultimately concluded that the data did not fit a NHPP for the systems considered but posits that other stochastic process can provide more accurate reliability calculations when compared to the two models analyzed

    Aggregated DER Management in Advanced Distribution Grids

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    Evolution of modern power systems are more distinct in distribution grids, where the growing integration of microgrids as well as distributed energy resources (DERs), including renewable energy resources, electric vehicles (EVs), and energy storage, poses new challenges and opportunities to grid management and operation. Rapid growth of distribution automation as well as equipment monitoring technologies in the distribution grids further offer new opportunities for distribution asset management. The idea of aggregated DERs is proposed as a remedy to streamline management and operation of advanced distribution grids, as discussed under three subjects in this dissertation. The first subject matter focuses on DER aggregation in microgrid for distribution transformer asset management, while the second one stresses on aggregated DER for developing a spinning reserve-based optimal scheduling model of integrated microgrids. The aggregation of EV batteries in a battery swapping stations (BSS) for enhancing grid operation is investigated in the third subject. Distribution transformer, as the most critical component in the distribution grids, is selected as the component of the choice for asset management practices, where three asset management studies are proposed. First, an approach in estimating transformer lifetime is presented based on the IEEE Std. C57.91-2011 and using sensory data. Second, a methodology to obtain a low-error estimate of transformer loss-of-life is investigated, leveraging an integrated machine learning and data fusion technique. Finally, a microgrid-based distribution transformer asset management model is developed to prolong the transformer lifetime. The resulting model aims at reshaping the distribution transformer loading via aggregating microgrid DERs in an efficient and asset management-aware manner. The increasing penetration of microgrids in distribution grids sets the stage for the formation of multiple microgrids in an integrated fashion. Accordingly, a spinning reserved based optimal scheduling model for integrated microgrids is proposed to minimize not only the operation cost associated with all microgrids in the grid-connected operation, but also the costs of power deficiency and spinning reserve in the islanded operation mode. The resulting model aims at determining an optimal configuration of the system in the islanded operation, i.e., optimal super-holons combination, which plays a key role in minimizing the system-aggregated operation cost and improving the overall system reliability. The evolving distribution grids introduce the concept of the BSS, which is emerging as a viable means for fast energy refill of EVs, to offer energy and ancillary services to the distribution grids through DER aggregation. Using a mixed-integer linear programming method, an uncertainty-constrained BSS optimal operation model is presented that not only covers the random customer demands of fully charged batteries, but also focuses on aggregating the available distributed batteries in the BSS to reduce its operation cost. Furthermore, the BSS is introduced as an energy storage for mitigating solar photovoltaic (PV) output fluctuations, where the distributed batteries in the BSS are modeled as an aggregated energy storage to capture solar generation variability. Numerical simulations demonstrate the effectiveness of the proposed models as well as their respective viability in achieving the predefined operational objectives

    Incorporating fuzzy-based methods to deep learning models for semantic segmentation

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    This thesis focuses on improving the workflow of semantic segmentation through a combination of reducing model complexity, improving segmentation accuracy, and making semantic segmentation results more reliable and robust. Semantic segmentation refers to pixel-level classification, the objective of which is to classify each pixel of the input image into different categories. The process typically consists of three steps: model construction, training, and application. Thus, in this thesis, fuzzy-based techniques are utilized in the aforementioned three steps to improve semantic segmentation workflow . The widely-used semantic segmentation models normally extract and aggregate spatial information and channel-wise features simultaneously. In order to achieve promising segmentation performance, it is required to involve numerous learnable parameters, which increase the model's complexity. Thus, decoupling the information fusion tasks is an important approach in the exploration of semantic segmentation models. Fuzzy integrals are effective for fusing information, and some special fuzzy integral operators (OWA) are free of parameters and easy to implement in deep-learning models. Therefore, a novel fuzzy integral module that includes an additional convolutional layer for feature map dimensionality reduction and an OWA layer for information fusion across feature channels is designed. The proposed fuzzy integral module can be flexibly integrated into existing semantic segmentation models, and then help reduce parameters and save memory. Following the exploration of semantic segmentation models, the collected data is used to train the model. Note that the precise delineation of object boundaries is a key aspect of semantic segmentation. In order to make the segmentation model pay more attention to the boundary, a special boundary-wise loss function is desirable in the segmentation model training phase. Fuzzy rough sets are normally utilized to measure the relationship between two sets. Thus, in this thesis, to improve the boundary accuracy, fuzzy rough sets are leveraged to calculate a boundary-wise loss, which is the difference between the boundary sets of the predicted image and the ground truth image. After completing the training process with the proposed novel loss, the next step for semantic segmentation is to apply the pre-trained segmentation model to segment new images. One challenge is that there are no ground truth images to quantify the segmentation quality in the real-world application of semantic segmentation models. Therefore, it is crucial to design a quality quantification algorithm to infer image-level segmentation performance and improve the credibility of semantic segmentation models. In this thesis, a novel quality quantification algorithm based on fuzzy uncertainty is proposed as part of the model inference process without accessing ground truth images. Moreover, to further explore the practical application of the proposed quality quantification algorithm in clinical settings, this thesis goes beyond public datasets and delves into a real-world case study involving cardiac MRI segmentation. Additionally, as clinicians also provide the level of uncertainty to measure their confidence when annotating to generate ground truth images (human-based uncertainty), the correlation between human-based uncertainty and AI-based uncertainty (calculated by the proposed quality quantification algorithm) is deeply investigated. Comprehensive experiments are conducted in this thesis to demonstrate that the integration of fuzzy-based technologies can enhance the efficiency, accuracy, and reliability of semantic segmentation models compared to those without such methods

    Neuro-fuzzy resource forecast in site suitability assessment for wind and solar energy: a mini review

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    Abstract:Site suitability problems in renewable energy studies have taken a new turn since the advent of geographical information system (GIS). GIS has been used for site suitability analysis for renewable energy due to its prowess in processing and analyzing attributes with geospatial components. Multi-criteria decision making (MCDM) tools are further used for criteria ranking in the order of influence on the study. Upon location of most appropriate sites, the need for intelligent resource forecast to aid in strategic and operational planning becomes necessary if viability of the investment will be enhanced and resource variability will be better understood. One of such intelligent models is the adaptive neuro-fuzzy inference system (ANFIS) and its variants. This study presents a mini-review of GIS-based MCDM facility location problems in wind and solar resource site suitability analysis and resource forecast using ANFIS-based models. We further present a framework for the integration of the two concepts in wind and solar energy studies. Various MCDM techniques for decision making with their strengths and weaknesses were presented. Country specific studies which apply GIS-based method in site suitability were presented with criteria considered. Similarly, country-specific studies in ANFIS-based resource forecasts for wind and solar energy were also presented. From our findings, there has been no technically valid range of values for spatial criteria and the analytical hierarchical process (AHP) has been commonly used for criteria ranking leaving other techniques less explored. Also, hybrid ANFIS models are more effective compared to standalone ANFIS models in resource forecast, and ANFIS optimized with population-based models has been mostly used. Finally, we present a roadmap for integrating GIS-MCDM site suitability studies with ANFIS-based modeling for improved strategic and operational planning

    Proceedings of the 1st Doctoral Consortium at the European Conference on Artificial Intelligence (DC-ECAI 2020)

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    1st Doctoral Consortium at the European Conference on Artificial Intelligence (DC-ECAI 2020), 29-30 August, 2020 Santiago de Compostela, SpainThe DC-ECAI 2020 provides a unique opportunity for PhD students, who are close to finishing their doctorate research, to interact with experienced researchers in the field. Senior members of the community are assigned as mentors for each group of students based on the student’s research or similarity of research interests. The DC-ECAI 2020, which is held virtually this year, allows students from all over the world to present their research and discuss their ongoing research and career plans with their mentor, to do networking with other participants, and to receive training and mentoring about career planning and career option
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