• 제어로봇시스템학회논문지
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• 제10권11호
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• pp.1028-1036
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• 2004

Ultrasonic sensors are widely used in mobile robot applications to recognize external environments by virtue that they are cheap, easy to use, and robust under varying lighting conditions. In most cases, a single ultrasonic sensor is used to measure the distance to an object based on time-of-flight (TOF) information, whereas multiple sensors are used to recognize the shape of an object, such as a comer, plane, or edge. However, the conventional sequential driving technique involves a long measurement time. This problem can be resolved by pulse coding of ultrasonic signals, which allows multi-sensors to be emitted simultaneously and adjacent objects to be distinguished. Accordingly, this paper presents a new simultaneous coded driving system for an ultrasonic sensor array for object recognition in autonomous mobile robots. The proposed system is designed and implemented. A micro-controller unit is implemented using a DSP, Polaroid 6500 ranging modules are modified for firing the coded signals, and a 5-channel coded signal generating board is made using a FPGA. To verify the proposed method, experiments were conducted in an environment with overlapping signals, and the flight distances fur each sensor were obtained from the received overlapping signals using correlations and conversion to a bipolar PCM-NRZ signal.

• 제어로봇시스템학회논문지
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• 제8권12호
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• pp.1056-1060
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• 2002

Model-based tuning rules of the PID controller are proposed incorporating with real-coded genetic algorithms. The optimal parameter sets of the PID controller for step set-point tracking are obtained based on the first-order time delay model and a real-coded genetic algorithm as an optimization tool. As for assessing the performance of the controllers, performance indices(ISE, IAE and ITAE) are adopted. Then tuning rules are derived using the tuned parameter sets, potential rule models and another real-coded genetic algorithm A set of simulation works is carried out to verify the effectiveness of the proposed rules.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권11호
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• pp.491-494
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• 2006

In the adder design, reduction of the delay of the carry propagation or ripple is the most important consideration. Previously, it was introduced that, if a redundant number system is adopted, the carry propagation is completely eliminated, with which addition can be done in a constant time, without regarding to the count of the digits of numbers involved in addition. In this paper, a RBCD(Redundant Binary Coded Decimal) is adopted to code 0 to 11, and an efficient and economic carry-free BCD adder is designed.

• 한국통신학회논문지
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• 제22권4호
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• pp.648-661
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• 1997

This paper presents a new method for post-processing of coded images based upon the low-pass filtering followed by the projection onto the NQCS (narrow quantization constraint set). We also investigate how the proposed method works on JPEG-coded real images. The starting point of the QCS-based post-processing techniques is the centroid of the QCS, where the original image belongs. The low-pass filtering followed by the projection onto the QCS makes the images lie on the boundary of the QCS. It is likely that, however, the original image is inside the QCS. Hence projection onto the NQCS gives a lower MSE (mean square error) than does the projection onto the QCS. Simulation results show that setting the narrowing coefficients of the NQCS to be 0.2 yields the best performance in most cases. Even though the JPEG-coded image is low-pass filtered and projected onto the NQCS repeatedly, there is no guarantee that the resultant image has a lower MSE and goes closer to the original image. Thus only one iteration is sufficient for the post-processing of the coded images. This is interesting because the main drawback of the iterative post-processing techniques is the heavy computational burden. The single iteration method reduces the computational burden and gives us an easy way to implement the real time VLSI post-processor.

• 대한전자공학회논문지TC
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• 제46권1호
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• pp.32-39
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• 2009

송신 단에서 채널 상태 정보를 알고 있는 폐루프 시스템은 개방 루프 시스템에 비하여 더 효율적인 전송을 수행할 수 있다. 그러나 실제 시스템은 제한된 피드백 채널을 가지므로 송신단에서 완벽한 채널 정보를 알 수 없으며, 따라서 부분 채널 정보를 활용하는 시스템의 설계가 중요한 요소로 부각되고 있다. 특히, 모바일 환경에서는 사용자의 이동성으로 인하여 채널 상태가 유동적으로 변화하며 이는 성능의 열화를 초래한다. 본 논문에서는 비트 인터리버와 결합한 부호화된 직교 주파수 다중 분할(BIC-OFDM; Bit-Interleaved Coded Orthogonal Frequency Division Multiplexing) 시스템을 위하여 채널 변화에 적절히 대응하는 적응 변조 코딩 기법을 제안한다. 합리적인 피드백 정보량을 통해, 제안하는 기법은 도플러 확산에 의한 채널 변화를 보상하여 향상된 성능을 제공한다. 실험 결과를 통해 제안하는 기법이 정확한 비트 에러율의 추정을 통한 성능 이득을 가짐을 확인한다.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2250-2261
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• 2020

Accurate localization of radioactive materials is crucial in homeland security and radiological emergencies. Coded-aperture gamma camera is an interesting solution for such applications and can be developed into portable real-time imaging devices. However, traditional reconstruction methods cannot effectively deal with signal-independent noise, thereby hindering low-noise real-time imaging. In this study, a novel reconstruction method with excellent noise-suppression capability based on a multi-layer perceptron (MLP) is proposed. A coded-aperture gamma camera based on pixel detector and coded-aperture mask was constructed, and the process of radioactive source imaging was simulated. Results showed that the MLP method performs better in noise suppression than the traditional correlation analysis method. When the Co-57 source with an activity of 1 MBq was at 289 different positions within the field of view which correspond to 289 different pixels in the reconstructed image, the average contrast-to-noise ratio (CNR) obtained by the MLP method was 21.82, whereas that obtained by the correlation analysis method was 5.85. The variance in CNR of the MLP method is larger than that of correlation analysis, which means the MLP method has some instability in certain conditions.

• 한국통신학회논문지
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• 제35권6C호
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• pp.562-571
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• 2010

차세대 대부분의 무선 통신 시스템에서는 심각한 페이딩을 극복하기 위하여 터보부호와 같은 연판정 입출력을 반복적으로 사용하는 오류정정부호화 방식을 사용하는 동시에, 시공간부호를 활용하여 다이버시티 이득을 얻고자 한다. 그러므로 수신단에서 시공간부호에서 검출된 신호는 연판정 출력 형태로 오류정정 복호기에 전달되어야 한다. 본 논문에서는 QAM과 같은 고차원 변조방식을 사용하여 시공간부호화와 반복 복호를 사용하는 오류정정부호화 방식이 결합된 경우에 성능의 극대화를 위하여 최적의 연판정 검출 방법을 제시한다. 터보부호를 사용하는 시스템에서 여러 가지 시공간부호화 방식과 고차원 변조 방식이 결합될 경우 여러 가지 연판정 검출 방법에 대한 시뮬레이션 결과를 제시하여, 제안된 방식이 적은 복잡도로 우수한 성능을 얻을 수 있음을 보인다.

• 한국통신학회논문지
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• 제25권8B호
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• pp.1499-1509
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• 2000

본 논문에서는 송.수신 다이버시티를 갖는 시.공간 부호화된 OFDM(Orthogonal Frequency-Division Multiplexing)시스템의 효율적인 채널추정기법을 제안한다 제안된 기법은"comb"형태의 훈련심볼을 사용하여 시.공간부호화된 OFDM 시스템의 복호기에서 필요한 채널의 주파수 응답을 구한다. 제안된 기법은 수신단의 주파수 영역에서 처리되므로 기존의 최소평균제곱오차(Minimum Mean-Squared Error: MMSE)기법에 비해 계산량을 크게 감소시킬 수 있다 또한 제안된 기법의 성능을 향상시키기 위해 랜덤 잡음의 영향을 감소시키고 채널의 변화를 추적할 수 있는 기법도 함께 제안한다 제안된 기법의 성능을 부선 이동 채널에서의 모의 실험을 통해 확인한다.을 통해 확인한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1645-1650
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• 2005

FOPDT(First-Order Plus Dead-Time) and SOPDT(Second-Order Plus Dead-Time) process, which are used as the most useful process in industry, are difficult about process identification because of the long dead-time problem and the model mismatch problem. Thus, the accuracy of process identification is the most important problem in FOPDT and SOPDT process control. In this paper, we proposed the real-coded genetic algorithm for identification of FOPDT and SOPDT processes. The proposed method using real-coding genetic algorithm shows better performance characteristic comparing with the existing an area-based identification method and a directed identification method that use step-test responses. The proposed strategy obtained useful result through a number of simulation examples.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.9-12
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• 2001

In this paper, the natural space-time coding is applied for a DS-CDMA system with multiple transmit/receive antennas in a Rayleigh fading channel. With difference of arrival times from transmit antennas a modified maximum likelihood (ML) decoding algorithm is proposed for the space-time coded DS-CDMA system. The proposed decoding algorithm performs ML decoding over the transition of two consecutive branches by using a modified branch metric with the partial autocorrelation. By simulation, it is shown that the proposed decoding algorithm achieves significant performance improvement over the ML decoding algorithm without the modified branch metric.