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컨벡스 최적화 기반의 가변유동형 덕티드 로켓 유도탄의 중기궤적 최적화 연구
김보석,정철구,이용건,성홍계,이창훈 제어·로봇·시스템학회 2023 제어·로봇·시스템학회 논문지 Vol.29 No.8
This paper presents a convex optimization-based trajectory optimization method for variable-flow ducted rocket missiles during midcourse engagement to reach the predicted intercept point (PIP). The minimum-intercept time problem is established by reflecting the dynamics and some flight constraints for ducted rocket missiles. An artificial neural network (ANN) is utilized to approximate the nonlinear relationship between several flight conditions and the performance of ducted rockets. In addition, this study, unlike previous studies, proposes selecting the air-to-fuel ratio instead of the fuel mass-flow rate as a control input. This can alter the nonlinear constraint as an equivalent linear constraint by combining it with the pseudospectral method, which is demonstrated in this paper. A convex sub-problem is established by applying successive linearization to the nonlinear dynamic constraint. An improved trust-region algorithm is utilized with the convex sub-problem to solve the original non-convex problem. Numerical optimization results are provided to demonstrate the performance of the proposed method and investigate the optimal trajectory for variable-flow ducted rocket missiles.
증착 중 자외광 노광에 의한 산화 아연 박막의 특성 변화
김보석,백승재,Kim, Bo-Seok,Baik, Seung Jae 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.4
ZnO thin films have wide application areas due to its versatile properties as transparent conductors, wide-bandgap n-type semiconductors, gas sensor materials, and etc. We have performed a systematic investigation on ultraviolet-assisted CVD (chemical vapor deposition) method. Ultraviolet irradiation during the deposition of ZnO causes chemical reduction on the growing surface; which results in the reduction of the deposition rate, increase in the surface roughness, and decrease of the electrical resistivity. These effects produce larger characteristic variation with various deposition conditions in terms of surface morphology and optical/electrical properties compared to normal CVD deposited ZnO thin films. This versatile controllability of ultraviolet-assisted CVD can provide a larger processing options in the fabrication of nano-structured materials and flexible device applications.