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시스템 응답속도 개선을 위한 새로운 입력성형기 설계 방법
최훈석(Hun-Seok Choi),박상원(Sang-Won Park),홍성욱(Seong-Wook Hong) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
It is well known that input shaping is an efficient tool to eliminate transient and residual vibration caused by motion of mechanical systems. However, the rise time of the systems tends to increase due to the presence of input shapers. This paper proposes an input shaper design method for a single mode system using a virtual mode, which is not an actual mode but reflected in the design process. The essence of the proposed method is to design a three-impulse input shaper as if the single mode system has two modes: one actual mode and one virtual mode. The natural frequency of the virtual mode is a design parameter to change the rise time of the system. Then, the rise time can be determined according to the design requirement. This paper discusses the performance of the proposed input shapers by simulation.
Cold Stretching 압력용기용 ASS304 소재의 극저온 인장 및 피로거동
최훈석(Hoon Seok Choi),김재훈(Jae Hoon Kim),나성현(Seong Hyun Na),이윤형(Youn Hyung Lee),김성훈(Sung Hun Kim),김영균(Young Kyun Kim),김기동(Ki Dong Kim) 대한기계학회 2016 大韓機械學會論文集A Vol.40 No.5
ASS304 소재로 제작된 cold stretching 압력용기는 극저온 액화천연가스의 운반 및 저장에 이용된다. Cold stretching 압력용기는 특정 수압을 이용하여 허용응력까지 기존의 압력용기를 신장시킴으로써 재료에 상당량의 소성변형이 나타난다. 이 경우, ASS304 소재의 특성에 따라 소성변형 후 항복강도가 증가하며, 신장량에 따라 두께가 감소한다. 따라서 강도 및 무게측면에서 기존의 압력용기 대비 높은 효율을 나타낸다. 본 연구에서는 ASME 코드에 의거하여 제작된 소형 cold stretching 압력용기에서 직접 채취한 시편을 이용하여 극저온 인장 및 피로특성을 평가하였다. 또한 저온피로시험으로부터 획득한 S-N 선도를 통계적으로 접근하여 P-S-N 선도를 작성하였으며, SEM 을 이용하여 파단면을 분석하였다. Cold stretching(CS) pressure vessels from ASS304 (austenitic stainless steel 304) are used for the transportation and storage of liquefied natural gas(LNG). CS pressure vessels are manufactured by pressurizing the finished vessels to a specific pressure to produce the required stress σk. After CS, there is some degree of plastic deformation. Therefore, CS vessels have a higher strength and lighter weight compared to conventional vessels. In this study, we investigate the tensile and fatigue behavior of ASS304 sampled by CS pressure vessels in accordance with the ASME code at cryogenic temperature. From the fatigue test results, we show S-N curves using a statistical method recommended by JSEM-S002. We carried out the fractography of fractured specimens using scanning electron microscopy (SEM).
박상원,최훈석,홍성욱 한국공작기계학회 2008 한국공작기계학회 추계학술대회논문집 Vol.2008 No.-
Input shaping is an efficient tool to eliminate residual vibration caused by motion of mechanical systems. However, the presence of input shapers may increase the rise time of system. This paper is concerned with the rise time reduction when using input shaping. To this end, this paper proposes an input shaper design method for an undamped single mode vibration system using virtual modes, which are not actual mode but reflected in the design process. This paper proposes a new input shaper which has multiple impulses as if a single mode system has more than one modes: one actual mode and several virtual modes. The natural frequencies of the virtual modes are design parameters to change the rise time of the system. This paper discusses the characteristics of the 1 virtual mode and 2 virtual mode input shapers. The performance of the proposed input shapers is tested by experiments.