• 한국정밀공학회지
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• 제18권11호
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• pp.86-92
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• 2001

Vibrational characteristics and tension fluctuation of a translating wire in WEDM are the main problems to deteriorate the cutting accuracy and processing performance. In this paper, we analyze natural frequencies of the wire used in WEDM, both theoretically and experimentally. To reduce the tension variation of the wire, which directly affects cutting performance, we have designed a simply tension reduction device using springs and rollers. It is shown that tension fluctuation is reduced about 35% using the passive tension controller.

• 한국항공우주학회지
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• 제50권3호
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• pp.181-192
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• 2022

헬기의 능동진동제어시스템(AVCS)은 주로터로부터 발생되는 진동을 제어하며, 수동형 진동저감장치 대비 저중량으로 우수한 진동저감 성능을 발휘한다. 본 논문에서는 FxLMS 알고리즘을 기반으로 타코미터 및 가속도 센서 신호를 통해 연산된 제어명령을 하중발생기(CFG)로 전달하여 소형민수헬기의 진동을 제어하는 소프트웨어 개발 및 검증 내용을 제시하였다. DO-178C /DO-331 표준에 따라 모델 기반 설계 기법을 통해 진동제어 소프트웨어를 개발하였으며, PILS 및 HILS 환경에서 실시간 작동 성능을 평가하였다. 특히, PILS 환경에서는 LDRA 기반 검증 커버리지를 통해 소프트웨어의 신뢰성을 향상시켰다. AVCS를 소형민수헬기에 적용하기 위해 지상/비행시험을 통해 대상 헬기 동적응답특성 모델을 획득하였다. 이를 기반으로 시스템 최적화 분석 및 비행시험을 통해 최적 성능을 발휘하는 AVCS 형상을 결정하고, STC 인증을 획득하였다.

• Computers and Concrete
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• 제20권5호
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• pp.545-553
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• 2017

A pounding tuned mass damper (PTMD) can be considered as a passive device, which combines the merits of a traditional tuned mass damper (TMD) and a collision damper. A recent analytical study by the authors demonstrated that the PTMD base on the energy dissipation during impact is able to achieve better control effectiveness over the traditional TMD. In this paper, a PTMD prototype is manufactured and applied for seismic response reduction to examine its efficacy. A series of shaking table tests is conducted in a three-story building frame model under single-dimensional and two-dimensional broadband earthquake excitations with different excitation intensities. The ability of the PTMD to reduce the structural responses is experimentally investigated. The results show that the traditional TMD is sensitive to input excitations, while the PTMD mostly has improved control performance over the TMD to remarkably reduce both the peak and root-mean-square (RMS) structural responses under single-dimensional earthquake excitation. Unlike the TMD, the PTMD is found to have the merit of maintaining a stable performance when subjected to different earthquake loadings. In addition, it is also indicated that the performance of the PTMD can be enhanced by adjusting the initial gap value, and the control effectiveness improves with the increasing excitation intensity. Under two-dimensional earthquake inputs, the PTMD controls remain outperform the TMD controls; however, the oscillation of the added mass is observed during the test, which may induce torsional vibration modes of the structure, and hence, result in poor control performance especially after a strong earthquake period.