• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.4
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• pp.387-407
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• 2015

This paper analyzes the $h{\times}p$ version of the finite element method for optimal control problems constrained by elliptic partial differential equations with random inputs. The main result is that the $h{\times}p$ error bound for the control problems subject to stochastic partial differential equations leads to an exponential rate of convergence with respect to p as for the corresponding direct problems. Numerical examples are used to confirm the theoretical results.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.4
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• pp.203-211
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• 1999

A control approach for the robust position control of induction motors based on the binary disturbance observer is described. The conventional binary disturbance observer is used to remove the chattering problem of a sliding mode disturbance observer. However, the steady state error may exist in the conventional binary disturbance observer because it estimates external disturbance with a constant boundary layer. In order to overcome this problem, new binary disturbance observer with an integral augmented switching hyperplane is proposed. The robustness is achieved, and the continuous control is realized by employing the proposed observer without the chattering problem and the steady state error. The effectiveness of the proposed observer is confirmed by the comparative experimental results.

• International Journal of Aerospace System Engineering
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• v.5 no.1
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• pp.9-18
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• 2018

The longitudinal flight parameters of a light airplane are estimated from flight test data by use of the output error method. The reliability of the flight test measurement is examined in engineering judgment, scatter and Cramer-Rao bound, which turns out to be satisfactory with minor defects. Estimated parameter values are validated by comparing the simulated responses with the ones from actual flight tests. The FTD(Flight Training Device) of a light airplane turns out to satisfy the qualification of FAA Level 5 FTD in longitudinal motion. All the necessary practices for generation of high-fidelity data in longitudinal motion of a light aircraft are successfully performed in this study.

• Computational Structural Engineering
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• v.11 no.4
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• pp.187-196
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• 1998

불연속 갤러킨 정식화에 기초를 둔 시간적분법에 대하여 시간을 변수로 한 유한요소적 접근법을 시도하였다. 단일 형상함수와 두 형상함수 정식화에 대해 각각 선형, 이차 형상함수를 적용하여 모두 네 종류의 시간적분법을 유도하였으며, 각 방법에 대하여 시간시텝의 증가에 따른 변위와 속도의 관계를 나타내는 증폭행렬을 계산하였다. 유도된 방법들의 성능을 평가하기 위하여 부하가 갑자기 변화는 진동 문제를 해석하고 변위의 오차를 비교하였다. 네 가지의 방법에 대하여 국부 오차 추정치를 개발하였으며, 오차 추정치의 정확도를 수치예를 이용하여 평가하였다. 단일 형상함수 정식화에서 이차 형상함수를 이용한 오차 추정치가 실제 국부오차를 잘 나타내었으며 유도된 오차 추정치는 시간간격제어 기법에서 시간간격의 크기를 결정하는 척도로 이용 가능하다.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.8
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• pp.450-456
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• 2003

This paper proposes a multiple time-series model with dummy variables for one-hour ahead load forecasting. We used 11 dummy variables that were classified by day characteristics such as day of the week, holiday, and special holiday. Also, model specification and selection of input variables including dummy variables were made by test statistics such as AIC(Akaike Information Criterion) and t-test statistics of each coefficient. OLS (Ordinary Least Squares) method was used for estimation and forecasting. We found out that model specifications for each hour are not identical usually at 30％ of optimal significance level, and dummy variables reduce the forecasting error if they are classified properly. The proposed model has much more accurate estimates in forecasting with less MAPE (Mean Absolute Percentage Error).

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.426-428
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• 1998

In this paper, a ramp tracking controller design method is proposed for the systems with nonlinear frictions. The objective is to design a controller which is capable of tracking a ramp reference input without steady state error. The controller is composed of a linear controller, integrators for error compensation, and a friction compensator. The compensator estimates the parameters of friction model. The friction parameters are estimated using two different method. Simulation and experimental results show that the proposed method is effective.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.11
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• pp.984-990
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• 2002

We propose a new type of nonlinear fixed interval smoother to which an existing nonlinear smoother is modified. The nonlinear smoother is derived from two-filter formulas. For the backward filter. the propagation and the update equation of error states are derived. In particular, the modified update equation of the backward filter uses the estimated error terms from the forward filter. Data fusion algorithm, which combines the forward filter result and the backward filter result, is altered into the compatible form with the new type of the backward filter. The proposed algorithm is more efficient than the existing one because propagation in backward filter is very simple from the implementation point of view. We apply the proposed nonlinear smoothing algorithm to off-line navigation system and show the proposed algorithm estimates position, and altitude fairly well through the computer simulation.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.69-72
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• 2002

In this paper, adaptive minimum mean-squared error (MMSE) multiuser detector combined with decision-feedback detector (DFD) is considered fur near-far resistant DS-CDMA system. To provide a reliable input to the adaptive MMSE detector, multiple-access interference (MAI) is regenerated using bit estimates from DFD and subtracted from the received signal. In the adaptive MMSE detector, the effect of the imperfect cancellation is compensated by a least mean square (LMS) algorithm. Through the numerical results, it is shown that, in a near-far situation, the proposed scheme provides superior performance to the matched filter (MF) receiver, adaptive MMSE detector, and DFD in terms of the bit error rate (BER).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5A
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• pp.500-508
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• 2008

Direct-sequence ultra-wideband(DS-UWB) system is being considered as one of promising transmission technologies for wireless personal area networks(WPANs). Due to relatively low spreading factors and huge bandwidth of transmit signal, a DS-UWB receiver needs to be equipped not only with a rake receiver but also with an equalizer, of which the equalizer is not required for traditional direct-sequence code division multiple access(DS-CDMA) systems. The number of rake fingers is limited in practice, influencing the performance of the subsequent equalizer. In this paper, we derive a decision feedback equalizer(DFE) for DS-UWB systems based on the minimum mean square error(MMSE) criterion, and investigate the impact of various parameters on the DFE performance in realistic scenarios. In particular, we propose an approach to improving the performance of the DFE using additional channel estimates for multipaths not combined in the rake receiver, and discuss how the accuracy of channel estimation affects desirable DFE configuration. Moreover, we present simulation results that show the impact of turbo equalization on the DFE performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.46-51
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• 2001

For Fast Real-time Recognition of Nonlinear Error Data, a new Neural Network algorithm which recognized the map in real time is proposed. The proposed neural network technique is the real time computation method through the inter-node diffusion. In the network, a node corresponds to a state in the quantized input space. Each node is composed of a processing unit and fixed weights from its neighbor nodes as well as its input terminal. The most reliable algorithm derived for real time recognition of map, is a dynamic programming based algorithm based on sequence matching techniques that would process the data as it arrives and could therefore provide continuously updated neighbor information estimates. Through several simulation experiments, real time reconstruction of the nonlinear map information is processed.