• Ocean Systems Engineering
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• v.6 no.3
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• pp.265-287
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• 2016

The change of the global performance of a turret-moored FPSO (Floating Production Storage Offloading) with DP (Dynamic Positioning) control is simulated, analyzed, and compared for two different internal turret location cases; bow and midship. Both collinear and non-collinear 100-yr GOM (Gulf of Mexico) storm environments and three cases (mooring-only, with DP position control, with DP position+heading control) are considered. The horizontal trajectory, 6DOF (degree of freedom) motions, fairlead mooring and riser tension, and fuel consumptions are compared. The PID (Proportional-Integral-Derivative) controller based on LQR (linear quadratic regulator) theory and the thrust-allocation algorithm which is based on the penalty optimization theory are implemented in the fully-coupled time-domain hull-mooring-riser-DP simulation program. Both in collinear and non-collinear 100-yr WWC (wind-wave-current) environments, the advantage of mid-ship turret is demonstrated by the significant reduction in heave at the turret location due to the minimal coupling with pitch mode, which is beneficial to mooring and riser design. However, in the non-collinear WWC environment, the mid-turret case exhibits unfavorable weathervaning characteristics, which can be reduced by employing DP position and heading controls as demonstrated in the present case studies. The present study also reveals the plausible cause of the failure of mid-turret Gryphon Alpha FPSO in milder environment than its survival condition.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.4
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• pp.195-203
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• 2017

A 2U cube satellite called SNUGLITE has been developed by GNSS Research Laboratory in Seoul National University. Its main mission is to perform actual operation by mounting dual-frequency global positioning system (GPS) receivers. Its scientific mission aims to observe space environments and collect data. It is essential for a cube satellite to control an Earth-oriented attitude for reliable and successful data transmission and reception. To this end, an attitude estimation and control algorithm, Attitude Determination and Control System (ADCS), has been implemented in the on-board computer (OBC) processor in real time. In this paper, the Extended Kalman Filter (EKF) was employed as the attitude estimation algorithm. For the attitude control technique, the Linear Quadratic Gaussian (LQG) was utilized. The algorithm was verified through the processor in the loop simulation (PILS) procedure. To validate the ADCS algorithm in the ground, the experimental verification via a single axis Hardware-in-the-loop simulation (HILS) was used due to the simplicity and cost effectiveness, rather than using the 3-axis HILS verification (Schwartz et al. 2003) with complex air-bearing mechanism design and high cost.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.700-705
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• 2005

The purpose of this project is the derivation and development of techniques for the new estimation of robustness for the systems having uncertainties. The basic ideas to analyze the system which is the originally nonlinear is Lyapunov direct theorems. The nonlinear systems have various forms of terms inside the system equations and this investigation is confined in the form of bounded uncertainties. Bounded means the uncertainties are with same positive/negative range. The number of uncertainties will be the degree of freedoms in the calculation of the stability region. This is so called the robustness bounds. This proposition adopts the theoretical analysis of the Lyapunov direct methods, that is, the sign properties of the Lyapunov function derivative integrated along finite intervals of time, in place of the original method of the sign properties of the time derivative of the Lyapunov function itself. This is the new sufficient criteria to relax the stability condition and is used to generate techniques for the robust design of control systems with structured perturbations. Using this relaxing stability conditions, the selection of Lyapunov candidate function is of various forms. In this paper, the quadratic form is selected. this generated techniques has been demonstrated by recent research interest in the area of robust control design and confirms that estimation of robustness bounds will be improved upon those obtained by results of the original Lyapunov method. In this paper, the symbolic algebraic procedures are utilized and the calculating errors are reduced in the numerical procedures. The application of numerical procedures can prove the improvements in estimations of robustness for one-and more structured perturbations. The applicable systems is assumed to be linear with time-varying with nonlinear bounded perturbations. This new techniques will be extended to other nonlinear systems with various forms of uncertainties, especially in the nonlinear case of the unstructured perturbations and also with various control method.

• Journal of Ocean Engineering and Technology
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• v.19 no.2 s.63
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• pp.67-73
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• 2005

This paper describes depth, heading and speed control of an underwater vehicle that has four stern thrusters of which forces are coupled in the diving and, steering motion, as well as the speed of the vehicle. The optimal linear quadratic controller is designed based on a linearized- state space model, developed by combining the dynamic equations of speed, steering and diving motion. The designed controller gives provides an optimal thrust distribution, minimizing the given performance index to control speed, depth and heading simultaneously. To validate the performance of the controller, a simulation and tank-test are carried out with DUSAUV (Dual Use Semi-Autonomous Underwater Vehicle), developed by KORDI as a test-bed for testing new underwater technologies. Optimal gains of the controller are tuned, using a computer simulation environment with a nonlinear 6-DOF numerical DUSAUV model, developed by PMM (Planner Motion Mechanism) test. To verify the performance of the presented controller in experiment, a tank-test with DUSAUV is carried out in the ocean engineering basin in KORDI. The experimental results are also compared with the simulation results to investigate the accordance of the numerical and the real mode.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.11
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• pp.1559-1567
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• 2012

The objective of this study was to evaluate ruminal degradability and intestinal digestibility of crude protein (CP) and amino acids (AA) in hempseed cake (HC) that were moist heat treated at different temperatures. Samples of cold-pressed HC were autoclaved for 30 min at 110, 120 or $130^{\circ}C$, and a sample of untreated HC was used as the control. Ruminal degradability of CP was estimated, using the in situ Dacron bag technique; intestinal CP digestibility was estimated for the 16 h in situ residue using a three-step in vitro procedure. AA content was determined for the HC samples (heat treated and untreated) of the intact feed, the 16 h in situ residue and the residue after the three-step procedure. There was a linear increase in RUP (p = 0.001) and intestinal digestibility of RUP (p = 0.003) with increasing temperature during heat treatment. The $130^{\circ}C$ treatment increased RUP from 259 to 629 g/kg CP, while intestinal digestibility increased from 176 to 730 g/kg RUP, compared to the control. Hence, the intestinal available dietary CP increased more than eight times. Increasing temperatures during heat treatment resulted in linear decreases in ruminal degradability of total AA (p = 0.006) and individual AA (p<0.05) and an increase in intestinal digestibility that could be explained both by a linear and a quadratic model for total AA and most individual AA (p<0.05). The $130^{\circ}C$ treatment decreased ruminal degradability of total AA from 837 to 471 g/kg, while intestinal digestibility increased from 267 to 813 g/kg of rumen undegradable AA, compared with the control. There were differences between ruminal AA degradability and between intestinal AA digestibility within all individual HC treatments (p<0.001). It is concluded that moist heat treatment at $130^{\circ}C$ did not overprotect the CP of HC and could be used to shift the site of CP and AA digestion from the rumen to the small intestine. This may increase the value of HC as a protein supplement for ruminants.

• Journal of Broadcast Engineering
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• v.16 no.2
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• pp.216-225
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• 2011

Following the proliferation of three-dimensional video contents and displays, many terrestrial broadcasting companies have been preparing for stereoscopic 3DTV service. In terrestrial stereoscopic broadcast, it is a difficult task to code and transmit two video sequences while sustaining as high quality as 2DTV broadcast due to the limited bandwidth defined by the existing digital TV standards such as ATSC. Thus, a terrestrial 3DTV broadcasting with a heterogeneous video codec system, where the left image and right images are based on MPEG-2 and H.264/AVC, respectively, is considered in order to achieve both high quality broadcasting service and compatibility for the existing 2DTV viewers. Without significant change in the current terrestrial broadcasting systems, we propose a joint rate control scheme for stereoscopic 3DTV service based on the heterogeneous dual codec systems. The proposed joint rate control scheme applies to the MPEG-2 encoder a quadratic rate-quantization model which is adopted in the H.264/AVC. Then the controller is designed for the sum of the left and right bitstreams to meet the bandwidth requirement of broadcasting standards while the sum of image distortions is minimized by adjusting quantization parameter obtained from the proposed optimization scheme. Besides, we consider a condition on maintaining quality difference between the left and right images around a desired level in the optimization in order to mitigate negative effects on human visual system. Experimental results demonstrate that the proposed bit rate control scheme outperforms the rate control method where each video coding standard uses its own bit rate control algorithm independently in terms of the increase in PSNR by 2.02%, the decrease in the average absolute quality difference by 77.6% and the reduction in the variance of the quality difference by 74.38%.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.7
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• pp.965-973
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• 2014

Three studies were conducted to investigate whether a chelated Cu can replace $CuSO_4$ as a growth promoter in pigs. In Exp. 1, a total of 240 piglets (Large White${\times}$Landrace, $7.36{\pm}0.10kg$) were randomly allocated to 1 of 3 treatments with 8 replicates and 10 piglets per pen. Treatments included a NRC control ($CuSO_4$, 6 mg/kg), two Cu supplementations from either $CuSO_4$ or $Cu(HMTBa)_2$ at 170 mg/kg. Pigs fed $Cu(HMTBa)_2$ were 6.0% heavier than pigs fed either the NRC control or 170 mg/kg $CuSO_4$ (p = 0.03) at the end of the experiment. During the 42 days of experimental period, pigs fed $Cu(HMTBa)_2$ gained 9.0% more (p = 0.01), tended to eat more feed (p = 0.09), and had better feed efficiency (p = 0.06) than those fed $CuSO_4$. Compared with the 6 mg/kg $CuSO_4$ NRC control, liver Cu was increased 2.7 times with 170 mg/kg $CuSO_4$ supplementation, and was further increased with $Cu(HMTBa)_2$ (4.5 times, p<0.05). In Exp. 2, a total of 616 crossbred piglets (PIC, $5.01{\pm}0.25kg$) were randomly allocated to 1 of 4 treatments with 7 replicates and 22 piglets per pen. Treatments included a NRC control (from $CuSO_4$), and three pharmaceutical levels of Cu (150 mg/kg) supplemented either from C$CuSO_4$, tri-basic copper chloride ($Cu_2[OH]_3C1$), or $Cu(HMTBa)_2$. Pigs fed $CuSO_4$ or $Cu(HMTBa)_2$ had better feed efficiency (p = 0.01) and tended to gain more (p = 0.08) compared with those fed the NRC control. Pigs fed $Cu_2[OH]_2C1$ were intermediate. Pigs fed $Cu(HMTBa)_2$ had the highest liver Cu, which was significantly higher than those fed ($Cu_2[OH]_3C1$) or the negative control (p = 0.01). In Exp. 3, a total of 1,048 pigs (PIC, $32.36{\pm}0.29kg$) were allotted to 6 treatments with 8 replicates per treatment and 20 to 22 pigs per pen. The treatments included a NRC control with 4 mg/kg Cu from $CuSO_4$, a positive control with 160 mg/kg Cu from $CuSO_4$, and incremental levels of $Cu(HMTBa)_2$ at 20, 40, 80, and 160 mg/kg. During the overall experimental period of 100 days, no benefit from 160 mg/kg $CuSO_4$ was observed. Pigs fed $Cu(HMTBa)_2$ had increased ADG (linear and quadratic, $p{\leq}0.05$) and feed efficiency (linear and quadratic, $p{\leq}0.05$) up to 80 mg/kg and no further improvement was observed at 160 mg/kg for the whole experimental period. Pigs fed 80 mg/kg $Cu(HMTBa)_2$ weighed 1.8 kg more (p = 0.07) and were 2.3 kg heavier in carcass (p<0.01) compared with pigs fed 160 mg/kg $CuSO_4$. In addition, loin depth was increased with increased $Cu(HMTBa)_2$ supplementation with pigs fed 80 mg/kg $Cu(HMTBa)_2$ had the greatest loin depth (p<0.05). In summary, $Cu(HMTBa)_2$ can be used to replace high $CuSO_4$ as a growth promoter in nursery and grower-finisher pigs.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.425-429
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• 2006

The understanding and prediction of the behavior of flow in open channels are important to the solution of a wide variety of practical flow problems in water resources engineering. Recently, frequent drought has increased the necessity of an effective water resources control and management of river flows for reserving instream flow. The objective of this study is to develop an efficient and accurate finite element model based on Streamline Upwind/Petrov-Galerkin(SU/PG) scheme for analyzing and predicting two dimensional flow features in complex natural rivers. Several tests were performed in developed all elements(4-Node, 6-Node, 8-Node elements) for the purpose of validation and verification of the developed model. The U-shaped channel of flow and natural river of flow were performed for tests. The results were compared with these of laboratory experiments and RMA-2 model. Such results showed that solutions of high order elements were better accurate and improved than those of linear elements. Also, the suggested model displayed reasonable velocity distribution compare to RMA-2 model in meandering domain for application of natural river flow. Accordingly, the developed finite element model is feasible and produces reliable results for simulation of two dimensional natural river flow. Also, One contribution of this study is to present that results can lead to significant gain in analyzing the accurate flow behavior associated with hydraulic structure such as weir and water intake station and flow of chute and pool.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1318-1320
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• 1999

Recently, according to the growth of national economy and the improvement of lining conditions, electric power demand is increasing gradually. So it is being examined to construct large thermal power plants or nuclear plants. For the effective use of lands and for the economy of generations sites, the distance between generation and demand locations becomes farther and farther. At the same time, people desire higher quality or electric power. So in this paper, the optimal modulation controller for HVDC transmission system are designed by a recursive algorithm that determines the state weighting matrix Q of a linear quadratic performance. It means that the application of optimal modulation controller in HVDC transmission system can contribute the propriety to the improvement of the stability in HVDC transmission system.

• Journal of Communications and Networks
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• v.15 no.4
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• pp.370-382
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• 2013

Distributed massive MIMO systems, which have high bandwidth efficiency and can accommodate a tremendous amount of traffic using algorithms such as zero-forcing beam forming (ZFBF), may be deployed in large public venues with the antennas mounted under-floor. In this case the channel gain matrix H can be modeled as a multi-banded matrix, in which off-diagonal entries decay both exponentially due to heavy human penetration loss and polynomially due to free space propagation loss. To enable practical implementation of such systems, we present a multi-banded matrix inversion algorithm that substantially reduces the complexity of ZFBF by keeping the most significant entries in H and the precoding matrix W. We introduce a parameter p to control the sparsity of H and W and thus achieve the tradeoff between the computational complexity and the system throughput. The proposed algorithm includes dense and sparse precoding versions, providing quadratic and linear complexity, respectively, relative to the number of antennas. We present analysis and numerical evaluations to show that the signal-to-interference ratio (SIR) increases linearly with p in dense precoding. In sparse precoding, we demonstrate the necessity of using directional antennas by both analysis and simulations. When the directional antenna gain increases, the resulting SIR increment in sparse precoding increases linearly with p, while the SIR of dense precoding is much less sensitive to changes in p.