• 전기의세계
• /
• 제49권9호
• /
• pp.17-24
• /
• 2000

This paper presents sufficient conditions7 for monotonicity of the saddle point value for receding-horizon H$\infty$ control(RHHC). The resulting monotonicity is used to prove the stability of the closed-loop. Under these sufficient conditions the well-known terminal equality condition is handled as a special case and the condition on the state weighting matrix is weakened so as to include even the zero matrix. The whole procedure is much simpler than the previous results and thus is expected to be easily extended for constrained delayed and/or nonlinear systems with the RHHC.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2003년도 ICCAS
• /
• pp.1901-1904
• /
• 2003

MPC or model predictive control is representative of control methods which are able to handle physical constraints. Closed-loop stability can therefore be ensured only locally in the presence of constraints of this type. However, if the system is neutrally stable, and if the constraints are imposed only on the input, global aymptotic stability can be obtained; until recently, use of infinite horizons was thought to be inevitable in this case. A globally stabilizing finite-horizon MPC has lately been suggested for neutrally stable continuous-time systems using a non-quadratic terminal cost which consists of cubic as well as quadratic functions of the state. The idea originates from the so-called small gain control, where the global stability is proven using a non-quadratic Lyapunov function. The newly developed finite-horizon MPC employs the same form of Lyapunov function as the terminal cost, thereby leading to global asymptotic stability. A discrete-time version of this finite-horizon MPC is presented here. The proposed MPC algorithm is also coded using an SQP (Sequential Quadratic Programming) algorithm, and simulation results are given to show the effectiveness of the method.

• 한국토양비료학회지
• /
• 제42권3호
• /
• pp.160-166
• /
• 2009

We estimated site productivity for unstocked land based on the relationship between site index (i.e., average height of dominant trees at fixed age) and soil physico-chemical properties of Pinus densiflora stands. Site index relates to a direct method of determining a tree's response to a specific environment such as forest soil and climate conditions. We selected 78 sites in 22 P. densiflora stands of central temperate forest zone, and sampled soils for physicochemical analyzing. And 13 properties of soils were statistically treated by stepwise regression. In the degree of contribution of the variables to site index, the highly effective variables in A horizon were OM, clay content, sand content, available $P_2O_5$, and Exch. $Ca^{{+}{+}}$ inorder, and in B horizon T.N., O.M., Soil pH, cation exchange capacity(C.E.C.), and sand content in order. In both A and B horizon of the soil for P. densiflora stands, the variables commonly contributed to the site index were sand content and OM. These results may be useful to provide not only important criteria for establishment of Pinus densiflora stand sespecially in unstocked land but also aguidance for reforestation.

• 한국토양비료학회지
• /
• 제37권5호
• /
• pp.322-328
• /
• 2004

Available nutrients in soil solution play key roles on the growth of plants, but the equilibria in soil solution can be disturbed by acid precipitation. In this study, we investigated the relationships between element concentrations in the needles of Pinus thunbergii and chemical properties of forest soil solutions in the industrial complexes as an effort to find the possible limiting factor(s) causing the forest decline. The Ca/Al molar ratios in needles of Pinus thunbergii collected from the control sites were 18. However, at Onsan and Ulsan industrial complexes, those were decreased to the ranges from 10 to 11 for the one-year old needles and from 9 to 10 for the two-year old needles. The Mg/Al molar ratios showed similar tendencies with the Ca/Al molar ratios of the needles of Pinus thunbergii. In the A horizon, there existed a significant correlation between Mg concentrations in the needles of Pinus thunbergii and Ca/Al molar ratio of forest soil solution. Calcium concentrations in the needles of Pinus thunbergii in the B horizon were also significantly correlated with Ca/Al molar ratios of forest soil solutions. The uptakes of Ca and Mg by Pinus thunbergii were mainly limited by Al in the soil solutions of the A horizon and by Mn and Al in the soil solutions of the B horizon.

• 한국지구과학회지
• /
• 제26권8호
• /
• pp.828-835
• /
• 2005

본 연구는 남한강 중류의 좌안에 분포하는 하성 고위면의 지형특성과 그 단구퇴적층을 모재로 발달한 토양특성을 밝히는데 있다. 조사토양인 적색토는 토양의 형태적, 물리 화학적 및 점토광물의 특성으로 보아 적색토로 분류된다. 토양특성과 고위면의 지형적 특성으로 보아 본 적색토는 제4기의 현재와는 다른 생물 기후환경차에서 탈규산화 작용과 적색토화 작용에 의하여 생성된 고적색토로 사료된다.

• Journal of Electrical Engineering and Technology
• /
• 제12권1호
• /
• pp.378-384
• /
• 2017

In this paper, an efficient short-time Fourier analysis method for the quasi-periodic signals is proposed via an optimal fixed-lag finite impulse response (FIR) smoother approach using a receding horizon scheme. In order to deal with time-varying Fourier coefficients (FCs) of quasi-periodic signals, a state space model including FCs as state variables is augmented with the variants of FCs. Through an optimal fixed-lag FIR smoother, FCs and their increments are estimated simultaneously and combined to produce final estimates. A lag size of the optimal fixed-lag FIR smoother is chosen to minimize the estimation error. Since the proposed estimation scheme carries out the correction process with the estimated variants of FCs, it is highly probable that the smaller estimation error is achieved compared with existing approaches not making use of such a process. It is shown through numerical simulation that the proposed scheme has better tracking ability for estimating time-varying FCs compared with existing ones.

• Advances in robotics research
• /
• 제2권2호
• /
• pp.161-182
• /
• 2018

This paper proposes a novel receding horizon control (RHC) algorithm for formation control of a swarm of unmanned surface vehicles (USVs) using particle swarm optimization (PSO). The proposed control algorithm provides the coordinated path tracking of multi-agent USVs while preventing collisions and considering external disturbances such as ocean currents. A three degrees-of-freedom kinematic model of the USV is used for the RHC with guaranteed stability and convergence by incorporating a sequential Monte Carlo (SMC)-based particle initialization. An ocean current model-based estimator is designed to compensate for the effect of ocean currents on the USVs. This method is compared with the PSO-based RHC algorithms to demonstrate the performance of the formation control and the collision avoidance in the presence of ocean currents through numerical simulations.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 추계학술대회논문집A
• /
• pp.659-664
• /
• 2000

Fuel-consumption and catalyst-out emissions of a parallel hybrid electric vehicle are affected by operating region of an engine. In many researches, It is generally known that it is profitable in fuel- consumption to operate engine in OOL(Optimal Operating Line). We established the mathematical model of a parallel hybrid electric vehicle, which is linear time-invariant. To operate an engine in OOL, we applied RHC(Receding Horizon Control) to the driving control of a parallel hybrid electric vehicle. And it is known that the RHC has advantages such as good tracking performance under state and control constraints. This RHC is obtained by using linear matrix inequality (LMI) optimization. In this paper, there are three main topics. First, without state and control constraints, the optimal tracking of OOL was simulated. Second, with state and control constraints by engine and motor performances, the optimal tracking of OOL was simulated. In the last, we studied on the optimal gear ratio. That is to say, we combined the RHC and the iterative simulation to extract the optimal gear ratio. In this simulation, the vehicle is commanded to track the reference vehicle trajectory and the engine is operated in the optimal operating region which is made by the state constraints.

• The Korean Journal of Ecology
• /
• 제9권4호
• /
• pp.231-241
• /
• 1986

The annual decomposition of cellulose and hemicellulose by microorganism and distribution of soil microbial flora were investigated in the humus horizon of a Pinus rigida stand in Mt. Kwanak. The cellulase activity was the lowest, 142$\mu$g glucose/g/hr from Dec. 1985 to Mar. 1986 and the highest, 760~1, 072$\mu$g glucose/g/hr in Jul. and Aug. 1985. The xylanase activity was 47% higher than the cellulase activity and was the lowest, 211~275$\mu$g xylose /g/hr from Feb. to Mar. 1986 and the highest as 799~1, 322$\mu$g xylose/g/hr from Jun. to Aug. 1986. The vertical distribution of the enzyme activity was decreased with the order of F, H, L, and A1 in both enzymes and the activities were exponentially decreased below L horizon, which suggests that most decomposition be done in F and H horizons with lots of organic matters. The SEM study slowed that the main decomposers of litters were fungi and initial attack into litters was also made by them. The enzyme activities of soil had strong correlations with the temperature and the precipitation. The correlation coefficients were 0.813 and 0.886 in the cellulase, and 0.673 and 0.626 in the xylanase for the temperature and the precipitation, respectively.

• 한국토양비료학회지
• /
• 제7권2호
• /
• pp.65-70
• /
• 1974

본(本) 연구(硏究)는 우리나라 내륙평탄지(內陸平坦地)에 분포(分布)하고 배수(排水)가 야간불량(若干不良)한 식질(埴質) 답토양(畓土壤)인 호남통(湖南統)에 대(對)하여 B층(層)의 토양생성학적(土壤生成學的) 특성(特性)을 미세형태학적(微細形態學的) 입장(立場)에서 구명(究明)해보고자 수행(遂行)하였다. 토양미세형태(土壤微細形態)에 관(關)한 분석(分析)은 토양(土壤)을 원상시료(原狀試料)(Undisturbed sample)로 채취(採取) 부편(溥片)을 제작(製作)한 후편광현미경(後偏光顯微鏡)을 이용(利用)하였으며 그 결과(結果)는 다음과 같다. 1. 호남통(湖南統)의 B층(層)에서 정방위점토(定方位粘土)가 (Oriented clay)가 확인(確認)되어 B층(層)은 Bt층(層)(Argillic Horizon)으로 간주(看做)된다. 2. B21t 층(層)에서 토양기질외(土壤基質外)의 정방위점토(定方位粘土)는 주(主)로 비대칭면상공극(非對稱面狀孔隙)(Skew plane) 및 관상공극(管狀孔隙)(Channel) 벽(壁)에 형성(形成)된 층상점토(層狀粘土)(Argillans)가 대부분(大部分)이나 토양기질내(土壤基質內)에 있는 정방위점토(定方位粘土)는 응력(應力)에 의(依)하여 토양기질내(土壤基質內)로 이동(移動)되고 있어 토양원질(土壤原質)(Plasma)의 분리현상(分離現象)이 뚜렷하다(Masepic). 3. B22t 및 B23t 층(層)에서의 정방위점토(定方位粘土)는 균일(均一)하지 않은 조점토(粗粘土)(Coarse, dirty clay)로 구성(構成)되여있으며 배열정도(排列程度)가 약(弱)하다(less oriented). 4. B24t 에서의 특징적(特徵的)인 정방위점토(定方位粘土)는 응력성점토피막(應力性粘土皮膜)(Stress cutans)이며 점토함량(粘土含量)이 높은 토양기질(土壤基質)이 오랜 기간(期間) 외부(外部)로부터 물리적(物理的)인 작용(作用)을 받아 일정(一定)한 방향(方向)으로 배열형성(排列形成)되었다.