• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.64-74
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• 2007

Because of the size and environment in the shipbuilding process, the portable type robot is required for the automatic seam tracking. For this reason, the structure of laser sensor should be considered in the initial design step and the coordinate transformation between welding robot and laser sensor, which is joint finder, must be identified exactly and the real time tracking algorithm based on these consideration could be developed. In this research, laser displacement sensor in which its structure is laser beam's vertical projection, is developed to recognize the location of weld joint. In practical applications, however, images of weld joints are often degraded because of the surface specularity or spatter. To overcome the problem, the constrained joint finding algorithm is proposed. In the approach of coordinate conversion rule for the visual feedback control among welding torch, robot body and laser sensor is applied by the same reference point method. In the real time seam tracking algorithms we propose constrained sampling method which uses look ahead distance. The RLS(Recursive Least Square) filter is applied to obtain the smooth tracking path from the sensitive edge data. From the experimental results, we could see the possibility that the developed laser sensor with proposed processing algorithm and real time seam tracking method can be used as a welding under the shipbuilding condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.3
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• pp.443-448
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• 2022

This paper presents a subband affine projection algorithm with variable step size to improve convergence performance in adaptive filtering applications with long adaptive filters and highly correlated input signals. The proposed algorithm can obtain fast convergence speed and small steady-state error by using different step sizes for each adaptive sub-filter in the subband structure to which polyphase decomposition and noble identity are applied. The step size derived to minimize the mean square error of the adaptive filter at each update time shows better convergence performance than the existing algorithm using a variable step size. In order to confirm the convergence performance of the proposed algorithm, which is superior to the existing algorithm, computer simulations are performed for mean square deviation(MSD) for AR(1) and AR(2) colored input signals considering the system identification model.

• Journal of the Korean Society of Radiology
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• v.2 no.3
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• pp.5-9
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• 2008

In the computerized tomography(CT), various filters are using in the reconstruction algorithm to reduce or eliminate the artifacts which are intrinsically induced by the imperfection of mathematical methods for reconstruction, lack of real informations about anatomic structures in the projection image, errors in data acquisition and so on. Hann filter was used to evaluate the filter effects on the elimination of reconstruction artifact in the CT image. The quantitative study was done by changing cut-off frequency of Hann filter from 0.1 to 0.9 with frequency increasement by 0.2. NPS analysis was fulfilled for the quantitative evaluation of filter effect.

• Journal of Broadcast Engineering
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• v.9 no.1
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• pp.91-94
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• 2004

The vergence controls of the parallel stereoscopic camera need only the disparity information of left and right images in horizontal direction. This paper proposed past and precise disparity value for stereoscopicimage pair in horizontal direction and the algorithm which can abstract disparity information through the HCF(Hybrid Cepstral Filter) for sign information. The proposed disparity information- extracting algorithm can obtain accurate disparity value of horizontal direction and signinformation by using both the one dimension cepstral filter which uses vertical projection data of left and right Image and the two dimension cepstral filter which uses down sampled image.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.557-562
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• 2003

An output multiplexer of manifold type is widely used in a recent satellite transponder for its mass and volume reduction. For correct operation, the filters of such a multiplexer must be singly terminated. In this paper, a simple synthesis method of a 6-pole dual-mode singly-terminated filter is described. From the transfer function of the filter, network parameters such as in/output terminations and coupling coefficients are obtained easily without complicated matrix algebra such as orthogonal projection and similarity transformation. Two different-structure filters are taken into consideration and the network parameters of each filter have been extracted from the same transfer function. It is shown that the responses of two filters are same to each other since their network parameters are obtained from the same transfer function. The method described in this paper can be applied to the other degree singly terminated filter.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.1
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• pp.14-22
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• 1980

The Fourier convolution algorithm is used to reconstruct a 34 density function from projection data sets. The convolved data are then back-projected to obtain a density function. There are several choices of the weighting function for the design of the reconstruction(deblurring) filter. Present Paper reviews the published reconstruction liters theoretically and proposes a new reconstructirm filter design method, considering the problems such as the effects of sampling rate, aliasing, and noise. Several previous reconstructirn filters are compared with the proposed filter by computer simulations.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.184-187
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• 2002

Two-dimensional (2-D) X-ray computerized tomography (CT) equipments are widely used in industrial and medical fields, and nowadays studies on reconstruction algorithm for 3-D cone-beam acquisition systems are active for better utilization. The authors recent-By have proposed a fast reconstruction aigorithm using tree-structured filter bank for 2-D C1, and shown the algorithm is applicable to an approximate reconstruction of 3-D CT. For exact 3-D CT reconstruction, however, we have to backproject 1-D signal into 3-D space. This paper proposes a fast implementation method for this back-projection by use of tree-structured filter bank. and shows the proposed method works approximately 700 times faster than the direct one with almost same reconstruction image quality.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.3
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• pp.20-25
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• 1980

A singular value decomposition (SVD) pseudo-inversion method has been applied to the image reconstruction from projections. This approach is relatively unknown and differs from conventionally used reconstructioll methods such as the Foxier convolution and iterative techniques. In this paper, two SVD pseudo-inversion methods have been discussed for the search of optimum reconstruction and restoration, one using truncated inverse filtering, the other scalar Wiener filtering. These methods partly overcome the ill-conditioned nature of restoration problems by trading off between noise and signal quality. To test the SVD pseudo-inversion method, simulations were performed from projection data obtained from a phantom using truncated inversefiltering. The results are presented together with some limitations particular to the applications of the method to the general class of 3-D image reconstruction and restoration.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.335-339
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• 1998

This paper presents a closed loop identification algorithm in time domain. This algorithm can be used for identification of unstable system and for model validation of system which is difficult to derive analytical model. In time domain, projection filter, which projects a finite number of input output data of a system into its current space, is used to relate the state space model with a finite difference model. Then recursive relations between the Markov parameters and the ARX model coefficients are derived to identify the system, controller and Kalman filter Markov parameters recursively, which are finally used to identify the system, controller and Kalman filter gains. The NASA LAMSTF is used to validate the algorithms developed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.5
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• pp.410-418
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• 2017

Results of an analysis of the continuous motion effect for FMCW-SAR system and a signal processing to correct it are presented in this paper. SAR images reconstructed by back-projection algorithm are included as well. To analyze how platform velocity and sampling frequency affect the continuous motion effect, FMCW signal model was used, and the signal processing in time-doppler(t, $k_u$) domain was adopted. Then, back-projection algorithm and modified matched-filter was used to reconstruct SAR images, and it was validated using measured data by airborne FMCW-SAR system in X-band frequency.