104,692 research outputs found
Health monitoring of wind turbine: Data-based approaches
No full textThis chapter presented a robust data-driven fault detection scheme with the application to a wind turbine benchmark. The proposed scheme is based on robust residual generators constructed directly from available process measurements. For this purpose, a parity space is first identified from the measured data, and optimal parity vectors are selected from the parity space according to a given performance index and an optimization criterion to generate a robust residual vector. A proper evaluation approach as well as a suitable decision logic is further given to make a correct final decision. The effectiveness of the proposed scheme is finally demonstrated by the results obtained from the simulation of a wind turbine benchmark model
Toward farm-level health management of wind turbine systems: Status and scope for improvements
No full textAn outline of health management for OWFs has been detailed in this chapter with description of various important elements. The need for such farm level management is explained and benefits are discussed. Key gaps to be filled in order to realize such a system are identified. The proposed health management system is mainly based on the existing knowledge of fleet-level management in the aerospace sector. Health management is much broader than CM; there are a number of aspects beyond the prognostics capabilities that are to be designed in order to arrive at a comprehensive maintenance management scheme. A comprehensive maintenance program that is sensitive to the health of the assets and adapts maintenance schedule accordingly, depending upon resource availability, logistics and inventory, is key to cost optimization while ensuring reliability and availability. The advances in CM and diagnostics in wind energy are in the right direction, and many of them are building blocks for health management. Offshore wind faces a number of unique challenges that can be satisfactorily addressed by following a suitable systematic approach. RCM implementation appears to be the most suitable as it encompasses other maintenance strategies and is suitable for farm-level deployment
Analysis of damage mechanisms in drilling of composite materials by acoustic emission
No full textComposite Structures
Volume 131, November 01, 2015, Pages 107-114
Analysis of damage mechanisms in drilling of composite materials by acoustic emission (Article)
Zarif Karimi, N.a ,
Minak, G.a ,
Kianfar, P.b
a Alma Mater Studiorum-Università di Bologna, Department of Industrial Engineering DIN, via Fontanelle 40, Forlì, Italy
b Amirkabir University of Technology, Department of Bioengineering, 424 Hafez Ave., Tehran, Iran
View references (49)
Abstract
Conventional methods for analysis of drilling of composite materials usually study the amount of damaged area and effective parameters. However, these methods do not provide investigators with sufficient information regarding drilling-induced damage. In this paper, a procedure for discrimination and identification of different damage mechanisms based on the analysis of acoustical signals emitted during the process is presented. Using principle component analysis for data reduction and unsupervised pattern recognition analysis, the drilling process was divided into three main stages, i.e. entry stage, cutting stage and exit stage. Different methods of signal processing were then used to identify and discriminate the most active damage mechanisms in each stage. As a result, matrix cracking, delamination, fiber pull out and friction were discriminated and the frequency distribution of each one was identifie
Fault diagnostics for electrically operated pitch systems in offshore wind turbines
No full textIn this chapter, the main objective is to determine the feasibility and applicability of current signature analysis for pitch motors in typical operating profiles. In order to determine pitch system operation profiles, the 5 MW reference wind turbine is simulated in FAST analysis tools developed by National Renewable Energy Laboratory [10]. The pitch systems however pose significant challenge in terms of intermittent, start-stop operating profiles and low speed operations. The main contribution of this chapter is therefore twofold: (1) to develop a detailed physical modelling of various motor faults and study their effect on motor currents in pitch system operating profiles and (2) to determine the feasibility of current signature analysis in such operating profiles. The rest of this chapter is organised as follows: In Section 8.2, determination of the typical pitch profiles from FAST analysis tool is described. Further, a detailed modelling of induction motor with implementation of various fault conditions is described in Section 8.3. In Section 8.4, the motor current signature analysis (MCSA) is tested for pitch motor diagnostics in various wind turbine operating profiles. Finally, accuracy of the fault detection algorithms and steps towards implementation in wind farms are discussed
A Wiki-Space Driven Approach To Reinforce Collective Learning
No full textLearning is a keystone for the development of a collective intelligence environment. Specifically, in a collaborative effort within inter-organizational ecosystems, learning can create new knowledge with the potential to influence behaviour and activate organisational collaboration as well as redesign social aspects and reconfigure the existing norms and values. To mobilise collective intelligence, creating crowdsourcing environments can be considered as learning experience tools that provide information based on real-life contexts. For migrants and refugees learning to access and feed reliable information can be a fundamental path toward their integration into a host community. To validate the possibility of developing a collective intelligence environment in a form of a wiki-space for (and by) migrants, this paper adopts the Triple-Loop Learning mechanism and the three learning drivers (what, how, and why) developed by the easyRights project. To do that, the paper presents the lessons learned from two hackathon initiatives organised in Palermo in Italy and in Malaga in Spain. The two subsequent hackathon initiatives had the scope to a) frame the wiki-space as an informative and crowdsourcing environment, b) create reliable content, and c) activate the necessary governance to guarantee its sustainability after the project’s termination for the very complex and ambiguous procedure of job seeking. The results led to a shared solution among the two cities as a service to sustain migrants' job seeking in the form of a wiki-space with two collective learning spheres: the methodology (the how dimension), and the platform itself (what, how, why dimensions). Through the findings from the two pilots' learning experiences, the paper essentially discusses how the project targets a systemic change by revisiting the existing knowledge in the organizations and creating a crowdsourcing platform of collective intelligence through a new mechanism that feeds the creation of values in different extents (societal, approach and service) toward a more inclusive society
Non-rigid image registration to reduce beam-induced blurring of cryo-electron microscopy images
No full textMicroscopic imaging and technolog
Innovative ICT Based Solutions and (Im)migrants Integration
No full textIn this special issue, we explore how ICTs can contribute to providing migrants inclusion and in general how to develop better links between theoretical and empirical research and policy practice related to (im)migrant integration. The collected articles give large emphasis to co-creation with a dual focus: on one hand it entails design suggestions supported by the engagement of all stakeholders including (im)migrants, and, on the other hand, with the co-evaluation, co-implementation, and co-validation of the insurgent solutions. The papers gathered in this special issue represent a collective attempt to bring together explorations of socio-technical innovations in migration studies as well as the identification of promises, pitfalls, and obstacles of ICT based technologies
APPLYING BIM TO BUILT HERITAGE WITH COMPLEX SHAPES: THE ICE HOUSE OF FILARETE’S OSPEDALE MAGGIORE IN MILAN, ITALY
No full textThis paper presents the development of a BIM model for a stratified historic structure characterized by a complex geometry: Filarete’s Ospedale Maggiore ice house, one of the few remaining historic ice houses in Milan (Fig. 1). Filarete, a well-known Renaissance architect and theorist, planned the hospital in the 15th century, but the ice house was built two centuries later with a double-storey irregular octagonal brick structure, half under and half above ground, that enclosed another circular structure called the ice room. The purpose of the double-walled structure was to store ice in the middle and store and preserve perishable food and medicine at the outer side of the ice room. During World War II, major portions of the hospital and the above-ground section of the ice house was bombed and heavily damaged. Later, in 1962, the hospital was restored and rehabilitated into a university, with the plan to conceal the ice house’s remaining structure in the courtyard, which ultimately was excavated and incorporated into a new library for the university.
A team of engineers, architects, and students from Politecnico di Milano and Carleton University conducted two heritage recording surveys in 2015 and 2016 to fully document the existing condition of the ice house, resulting in an inclusive laser scanner and photogrammetric point cloud dataset. The point cloud data was consolidated and imported into two leading parametric modelling software, Autodesk Revit© and Graphisoft ArchiCAD©, with the goal to develop two BIMs in parallel in order to study and compare the software BIM workflow, parametric capabilities, attributes to capture the complex geometry with high accuracy, and the duration for parametric modelling. The comparison study of the two software revealed their workflow limitations, leading to integration of the BIM generative process with other pure modelling software such as Rhinoceros©. The integrative BIM process led to the production of a comprehensive BIM model that documented related historic data and the existing physical state of the ice house, to be used as a baseline for preventive maintenance, monitoring, and future conservation projects
L ∞ control for positive delay systems with semi-Markov process and application to a communication network model
No full textThis paper deals with the problem of L ∞ control for positive delay systems with semi-Markov process. The system is subjected to a semi-Markov process that is time-varying, dependent on the sojourn time, and related to Weibull distribution. The main motivation for this paper is that the practical systems such as the communication network model (CNM) described by positive semi-Markov jump systems (S-MJSs) always need to consider the sudden change in the operating process. To deal with the corresponding problem, some criteria about stochastic stability and L ∞ boundedness are presented for the open-loop positive S-MJSs. Further, some necessary and sufficient conditions for state-feedback controller satisfying L ∞ boundedness and positivity of the resulting closed-loop system is established in standard linear programming. Finally, the practical system about the CNM is given to verify the validity of the proposed method
SMC for nonlinear stochastic switching systems with quantization
No full textThis paper focuses on the sliding mode control (SMC) design for nonlinear stochastic switching systems subject to semi-Markov switching parameters and signal quantization. The aim of this work is to design an efficient SMC scheme under quantization error effect. To this end, a mode-independent sliding surface is adopted to avoid the potential repetitive jumping effects. Then, based on the weak infinitesimal operator theory, sufficient conditions are given for the corresponding stochastic stability criteria. Furthermore, an appropriate SMC law is proposed to drive the state signals onto the predefined manifold and the effect of quantization error can be effectively attenuated. Finally, a single-link robot arm model is provided to illustrate the effectiveness of the theoretical findings
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