1,721,053 research outputs found
Virtual assessment of structural health monitoring techniques for wind turbines using vibration data
No full textOperational Modal Analysis (OMA), also known as output-only modal analysis, allows identifying modal parameters only by using the response measurements of the structure in operational conditions when the input forces cannot be measured. This information can then be used to improve numerical models in order to monitor the operating and structural conditions of the system. This is a critical aspect both for condition monitoring and maintenance of large wind turbines, particularly in the off-shore sector where operation and maintenance represent a high percentage of total costs.
The availability of commercial numerical aeroelastic simulation codes simulating the response of wind turbines in operation can be used as a virtual design and verification tool. Effects of design modifications and variations in the environmental and structural conditions can all be simulated using these tools. However, experimental test campaigns should be able to provide accurate and reliable data with which the model can be updated and be more representative of the real response. Thus, the improvement of these simulation models is strongly related to the improvement of the current Operational Modal Analysis (OMA) modal parameter estimation techniques. The main issue for these methods is that, due to blade rotation, force periodicity and the presence of control surfaces which modify continuously the system configuration, most of the applicability assumptions of OMA are violated. In this paper, some preliminary assessments on how to combine numerical and experimental techniques for Structural Health Monitoring (SHM) of wind turbines are investigated
Application of digital image correlation in operational modal analysis of rotating structures
No full textConventional methods for Operational Modal Analysis (OMA) typically involve the placement of stationary probes, such as accelerometers, to measure the vibration modes of structures. However, the use of Digital Image Correlation (DIC) for OMA offers the advantage of being a non-contact, full-field measurement technique. This approach is particularly advantageous for rotating machines, as it eliminates the effects of adding sensor masses to the structure and data transmission problems. This work addresses the challenges associated with applying the DIC technique to vibration analysis on rotating components and proposes a new methodology for Rigid Body Motion (RBM) compensation. This methodology addresses the complexities in the analysis of rotating structures, ensuring accurate results. The effectiveness of the proposed methodology is demonstrated through its application in the experimental analysis of the impulse response of a rotating rectangular plate using high-speed cameras and DIC technique
Order-based modal analysis: a modal parameter estimation technique for rotating machineries
No full textAdvanced Notch Prediction using Time Simulation
No full textDuring vibration test of space hardware safety measures are never enough. In addition to all the self-check, system identification and drive limiting measures, it is customary for engineers also to define a notching profile. With this strategy one or more control (or measurement) channels have individual frequency ranges where each response must not exceed a predetermined level. Unfortunately, when many channels are ???active??? it is often the case that, for excess of safety, the target is no inherent of the control loop for the response to overshoots and they are not able to accommodate specific aerospace applications in which there are highly restrictive specifications. This paper presents an approach to automate and optimize the definition of a notch profile. The method is developed in a Matlab/Simulink environment which replicates the LMS Sine Control software and is based on a model of the structure under test
Wind turbine gearbox dynamic characterization using Operational Modal Analysis
No full textThe aim of this paper is to characterize the dynamic behavior of a wind turbine gearbox installed on a dynamic test rig to replicate operational conditions. Wind turbines and gearboxes operate under very dynamic and complex conditions, caused by turbulent wind, fluctuations in the electricity grid etc. In those conditions, structural nonlinearities in bearings and gears cause natural frequencies to be significantly influenced by the operational conditions. To verify the dynamic response of a multi-megawatt gearbox, a comprehensive test campaign has been performed in the context of the European project ALARM at the ZF Wind Power test rig. Accelerations have been measured at more than 250 locations on the test rig and for different load levels and operating conditions. This paper focuses on the influence of the torque levels on the identified modal parameters. The acquired time histories during run-ups have been processed using different Operational Modal Analysis techniques. The aim is to provide a modal model that can be used for correlation and updating of a flexible nonlinear multibody model of the whole test rig as well as vibration levels to estimate structure-borne noise in the different operating conditions
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