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마평식(Pyung Sik Ma),김재은(Jae Eun Kim),김윤영(Yoon Young Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The topology optimization method is applied to the design of a vibration-powered, cantilevered Piezoelectric Energy Harvester (PEH) whose base is subject to a vibrating motion. The optimization problem is so formulated as to maximize the Electro-Mechanical Coupling Coefficient (EMCC) with volume constraints because the EMCC is the key factor affecting electrical power output for a given base input acceleration. Since the present PEH is supposed to operate at either short-circuit or open-circuit resonant frequencies for producing the maximum output power, the resonant frequency is also considered in the topology optimization formulation. In order to investigate the dimensional effects of a PEH on the power output, a number of different combinations of piezoelectric composite beam and tip mass dimensions are considered. The optimized results are presented and findings from this research that can be useful for practical design of PEH’s are summarized.
석션 버켓 지지구조 해상 풍력발전기의 고유진동수 예측과 구조물 건전성 감시 시스템을 이용한 고유진동수 관찰
서윤호,마평식,김상렬,김봉기 한국풍력에너지학회 2019 풍력에너지저널 Vol.10 No.2
As the reliability of a tripod support structure with suction buckets should be evaluated by avoiding resonance, an efficient method to predict natural frequency, which is also known as an effective tool to show the existence of damage in wind turbines, is suggested. The whole structure is modeled by beam elements, while a nacelle with blades is considered as a mass. A boundary condition of the suction buckets is described by a serial combination of stiffness elements for soil and a connecting part of a suction bucket. Then, an effective structural health monitoring (SHM) system is developed to validate the proposed modelling method. Accelerometers, strain gauge and various sensors for measurement of sea environment are installed in proper locations, and measured natural frequency is extracted by measured bending strain. It is validated that the measured natural frequency is the almost the same as the predicted one, with an error rate below 1%, and the natural frequency has sufficient margin to major excitation frequencies such as 1P and 3P. Also, it is observed that the measured natural frequency is constant for 3 months.