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Collision Avoidance Using Linear Quadratic Control in Satellite Formation Flying
Sung-Hoon Mok,Yoon-Hyuk Choi,Hyo-Choong Bang 한국항공우주학회 2010 International Journal of Aeronautical and Space Sc Vol.11 No.4
This paper proposes a linear system control algorithm with collision avoidance in multiple satellites. Consideration of collision avoidance is augmented by adding a weighting term in the cost function of the original tracking problem in linear quadratic control (LQC). Because the proposed algorithm relies on a similar solution procedure to the original LQC, its inherent advantages, including gain-robustness and optimality, are preserved. To confirm and visualize the derived algorithm, a simple example of two-vehicle motion in the two-dimensional plane is illustrated. In addition, the proposed collision avoidance control is applied to satellite formation flying, and verified by numerical simulations.
Choi, Hye-Won,Jeong, In-Sung,Park, Sang-Yong,Choi, Hyo-Sang IEEE 2018 IEEE transactions on applied superconductivity Vol.28 No.3
<P>In this study, superconducting coil-type dc fault current limiter (SC-DC FCL) was proposed. The interruption and operation characteristics of the SC-DC FCL were analyzed, which was applied to a 7.98 kW-class photovoltaic (PV) generation system. Electro magnetic transients including direct current/power system computer aided design (EMTDC/PSCAD) have been used for the simulation. The simulation results showed that the interruption operation time of the mechanical circuit breaker, the power burden applied to the circuit breaker, and the peak value of the fault current were significantly reduced by the application of the SC-DC FCL. In addition, when the SC-DC FCL was applied, the fault current flowing through the line was limited by approximately 78% or more.</P>
ESTUARY TYPE AND PLUME STRUCTURE OF THE KEUM RIVER ESTUARY
Sang Ho Lee,Hyun Yong Choi,Hyo Keun Kwon,Eun Ju Shin 한국해안해양공학회 1999 학술강연회 발표논문초록집 Vol.1 No.1
We studied the type and circulation of estuary and the structure of river plume from the data obtained after the dyke construction in the Keum River estuary. The observed tidally averaged salinity profiles correspond to the partially mixed estuary, with increasing the mean salinity in downstream direction and with depth regardless of the amount of the river discharge. During the temporary river discharge in May 1998, the releasing of fresh water from the upper layer in the estuary mouth in the ebbing is a supplying process of the low salinity water to the offshore river plume. The estuary type agrees with the stratification and circulation diagram calculated by Lee et al. (1999). The observed tide-mean flows reverse with depth, which are correspondent to the circulation type of partially mixed estuary, implying that suspended sediments are deposited in the upstream region near the Keum River dyke. For the large river discharge in August 1998 the river plume makes a strong jet of low salinity water west of the estuary mouth. Low salinity water extends farther seaward beyond Oeyon-do, showing a tongue-like distribution, which is deflected to the right from the jet. The distance of the plume reaches 60㎞ from the river mouth. The plume jet has a lens of low salinity in the section, of which the size and depth of the deep axis in the first observation is much larger and deeper than in the second probably due to the difference of the river discharge volume. In the farther offshore section the depth of extended plume is much shallower, overlying the ambient water.