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공남웅(NamWoong Kong),박인석(In Seok Park),김민수(Min Su Kim),최용준(Yong-Joon Choi),박부견(Poogyeon Park),윤종필(Jong Pil Yun) 대한전자공학회 2018 대한전자공학회 학술대회 Vol.2018 No.6
In order to develop the precise camber simulator, it is necessary to predict the value of roll force. Thus, this paper considers the problem of prediction of the roll force in hot rolling mill process via deep nerual network. The neural network is constructed as 4 hidden layers. The training data is obtained from the real hot rolling mill process: 20832 samples. Since, in general, the simulator and controller are designed by using MATLAB, the artificial neural network model is designed by using MATLAB.
An Affine Projection Algorithm Based on Reuse Time of Input Vectors
MoonSoo Chang,NamWoong Kong,PooGyeon Park IEEE 2010 IEEE signal processing letters Vol.17 No.8
<P>This letter proposes an affine projection algorithm (APA) based on the concept of reuse time of the current input vector. Reuse time is defined as the survival period of an input vector, during which the input vector is continuously reused in the subsequent update equations. The algorithm consists of two key procedures: assignment and reduction. The assignment procedure assigns a fundamental reuse-time or zero to the individual reuse time of each current input vector only once by checking whether the current input vector has enough information for update, which eliminates the repetitive selection procedure for input vectors. The reduction procedure gradually decreases the fundamental reuse time by examining, from a stochastic point of view, whether the current error reaches the steady-state value, which indirectly controls the number of input vectors; this leads to fast convergence and small estimation errors. Through these two procedures, the proposed algorithm achieves not only improved performance but also extremely low computational complexity.</P>
Normalised subband adaptive filter with variable step size
JaeWook Shin,NamWoong Kong,PooGyeon Park IET 2012 Electronics letters Vol.48 No.4
<P>Proposed is a normalised subband adaptive filter algorithm with a variable step size based on the mean-square deviation (MSD) analysis. Since the spectrum of each input signal in subbands is close to that of white noise, the MSD can be approximated. The step size in this study is chosen such that the MSD undergoes the largest decrease from one iteration to the next, which leads to a fast convergence rate and a small misalignment. Simulation results confirm that the proposed algorithm outperforms existing algorithms in the literature.</P>
Normalized LMS algorithm with Evolutionary Change of Orthogonal Correction Factors
JiHye Seo,NamWoong Kong,PooGyeon Park 제어로봇시스템학회 2011 제어로봇시스템학회 국제학술대회 논문집 Vol.2011 No.10
This paper proposes a normalized LMS algorithm which automatically determines the number of orthogonal correction factors using an evolutionary method. The evolutionary method increases or decreases the number of orthogonal correction factors by comparing the squared output errors with some threshold. The experimental results show that the proposed algorithm has not only a fast convergence rate and a small steady-state estimation error but also lower computational complexity than the existing algorithms with multiple input vectors.
A Fast Image Stitching Algorithm in The Endless Hot Rolling Process
JongSeok Lee,NamWoong Kong,JinWoo Yoo,PooGyeon Park 제어로봇시스템학회 2011 제어로봇시스템학회 국제학술대회 논문집 Vol.2011 No.10
Camber is one of the most important defects in the endless hot-rolling process, and can be defined as the longitudinal curvature of a slab or strip in the plan view. To obtain a value of the camber for a steel bar, the overall shape of a slab or strip is required. However, the strip is too long to capture overall image at once. In order to obtain precise information on the overall shape of the bar, two area-scan charge-coupled device (CCD) cameras to obtain partial bar images and the image stitching algorithm are needed. This paper proposes a fast algorithm to obtain the overall shape of a steel bar in the endless hot rolling process. The proposed algorithm reduces the computational complexity and the running time of the image stitching process by adaptively selecting the search region to find feature points in steel bar images. The algorithm consists of three parts: generating the feature points and descriptors of the selected regions of continuous images for the steel bar, choosing the overlapped region between the present image and the next image, and stitching the partial bar images after calibrating them. The proposed stitching algorithm based on adaptive selection of the search region improves the performance of the camber measurement system during the image stitching process.
Scheduled-Stepsize NLMS Algorithm
Poogyeon Park,Moonsoo Chang,Namwoong Kong IEEE 2009 IEEE signal processing letters Vol.16 No.12
<P>This paper presents a method of scheduling stepsizes for the normalized least-mean-squares (SS-NLMS) algorithm. Geometrically interpreting the mean square deviation (MSD) learning curve leads to establishing an objective curve and to constructing a lookup table of stepsizes in order for the MSD to follow the curve. The SS-NLMS shows not only good performance but also robustness with respect to different signal-to-noise ratio (SNR) in measurement noise and different correlation in input signals with a very small number of online computations. Moreover, the scalability of the tabled stepsize with respect to the number of taps is described. For the efficient memory usage in practice, a modified version replaces the tabled stepsizes by down-sampled stepsizes with no performance degradation.</P>
Development of Defect Detection Algorithm in Cold Rolling
Sung Wook Yun,NamWoong Kong,Gyumin Lee,PooGyeon Park 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
In this paper, we propose the defect detection algorithm using the image processing in cold rolling. This algorithm consists of two separated parts: defect detection of the steel sheet in a rolling process and defect detection of the cutting plane in a side trimming process. The objective of the crack and hole detection is to find the position and diameter of holes and some information of cracks such as the depth, width, position, and type. Furthermore, the objective of the defect detection for the cutting plane is to find the position of defects on the cutting plane, the number of those, and the thickness ratio between the cutting plane and the cold rolled steel sheets. Experimental results show that the proposed algorithm finds the defect information of cold rolled steel sheets satisfying the processing-speed constraint of 30 frames/sec.
몰드 오실레이터 이중구조 실린더의 정현파 진동 특성을 이용한 위치동기화 알고리즘 개발
김승훈(Seung Hun Kim),최두철(Doo Chul Choi),공남웅(NamWoong Kong),김상우(Sang Woo Kim) 제어로봇시스템학회 2015 제어·로봇·시스템학회 논문지 Vol.18 No.1
Improvement in the control strategy for continuous casting is a crucial requirement to enhance the slab’s quality and to increase productivity. The mold oscillator adopts the dual cylinders due to its heavy weight, so the synchronized motion of two cylinders is an important aspect when precise control is needed. The conventional method uses the master-slave control applied to the valve input reference, but the synchronization performance should still be improved. This paper proposes a novel synchronization algorithm for dual cylinders used in a mold oscillator. The master-slave concept is applied to the target reference position, that is, the slave target reference position is controlled to match the slave cylinder’s position with the master cylinder’s position. In the simulation based on a Simulink model, the proposed algorithm shows a better synchronization performance in aspect of the mean of the absolute error and the peak synchronization error.