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정밀작업용 테이블의 직동 외란 억제 시스템 설계에 관한 연구
김형진,이동훈,박환철,김영복 대한기계학회 2020 大韓機械學會論文集A Vol.44 No.11
In this paper, we propose a novel method for designing a vibration suppression system that rejects the impact of irregular disturbances on high precision fabrication tables. In particular, we derive a new feedforward control method to suppress the direct disturbances generated from on-table machine operations effectively. To verify the effectiveness of the proposed control method, a simulation is performed by combining it with feedback control for floor disturbances. By providing this proposed feedforward control method, the suppression of vibration is significantly improved, thereby enabling higher precision works. 본 논문에서는 정밀작업용 테이블에 미치는 외란의 영향을 억제하기 위한 새로운 진동 억제 시스템 설계 방법을 제안하였다. 바닥으로부터 유입되는 외란뿐만 아니라 테이블 상부에 설치된 장치로부터 발생하는 비규칙적이고 비주기적인 직동(장치) 외란 억제 문제에 대해 고찰하였다. 기존의 확정적이고 규칙적인 장치 외란 억제 방법은 아주 특수한 경우에만 그 효과를 기대할 수 있으나 일반적인 기기 운용 환경에서는 외란 억제 효과를 기대할 수 없고 활용성도 떨어진다. 그래서 본 연구에서는 운동 장치의 구동 신호를 이용하는 새로운 피드포워드 제어기법을 통해, 비규칙적이고 비주기적인 장치 외란을 억제하는 방법을 제안하였다. 바닥 및 장치 외란이 독립적으로 존재할 경우뿐만 아니라 두 가지 형태의 외란이 동시에 인가될 경우에도 제안된 제어기법이 효과적으로 대응할 수 있음을 시뮬레이션을 통해 검증하였다.
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김형진,Kumiko Takata,Katsunori Tanaka,Ryoji Yamashima,Jun Matsumoto,Kazuyuki Saito,Toshihiko Takemura,Tetsuzo Yasunari 한국기상학회 2014 Asia-Pacific Journal of Atmospheric Sciences Vol.50 No.4
A series of 60-year numerical experiments starting from 1851 was conducted using a global climate model coupled with an aerosol-cloud-radiation model to investigate the response of the Asian summer monsoon to variations in the secondary organic aerosol (SOA) flux induced by two different estimations of biogenic volatile organic compound (BVOC) emissions. One estimation was obtained from a pre-existing archive and the other was generated by a next-generation model (the Model of Emissions of Gases and Aerosols from Nature, MEGAN). The use of MEGAN resulted in an overall increase of the SOA production through a higher rate of gasto- particle conversion of BVOCs. Consequently, the atmospheric loading of organic carbon (OC) increased due to the contribution of SOA to OC aerosol. The increase of atmospheric OC aerosols was prominent in particular in the Indian subcontinent and Indochina Peninsula (IP) during the pre- and early-monsoon periods because the terrestrial biosphere is the major source of BVOC emissions and the atmospheric aerosol concentration diminishes rapidly with the arrival of monsoon rainfall. As the number of atmospheric OC particles increased, the number concentrations of cloud droplets increased, but their size decreased. These changes represent a combination of aerosol-cloud interactions that were favorable to rainfall suppression. However, the modeled precipitation was slightly enhanced in May over the oceans that surround the Indian subcontinent and IP. Further analysis revealed that a compensating updraft in the surrounding oceans was induced by the thermally-driven downdraft in the IP, which was a result of surface cooling associated with direct OC aerosol radiative forcing, and was able to surpass the aerosolcloud interactions. The co-existence of oceanic ascending motion with the maximum convective available potential energy was also found to be crucial for rainfall formation. Although the model produced statistically significant rainfall changes with locally organized patterns, the suggested pathways should be considered guardedly because in the simulation results, 1) the BVOC-induced aerosol direct effect was marginal; 2) cloud-aerosol interactions were modeldependent; and 3) Asian summer monsoons were biased to a nonnegligible extent.
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