• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.476-478
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• 1997

A new speed detection method using low resolution incremental encoders, especially excellent in the low speed region and in the transient state, is proposed. The half period error of an incremental encoder is greater than the period error. So it's not recommended to quadruple the number of pulses per revolution, because it increase the ripple of speed. To overcome this restriction a speed detection, method has been proposed. But it requires so many latch circuits. Therefore we propose a new speed detection method that has different concept and has fewer latch circuits.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.377-382
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• 1993

The low speed control of a servo motor using instantaneous speed detection method is described. To estimate the instantaneous speed from the average speed, the speed estimator of the first or second order is used. We confirm that these estimatorsimprove the speed control performance of a servo system with experiments.

• 전자공학회논문지B
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• 제31B권9호
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• pp.36-46
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• 1994

A analog disturbance observer, which is suitable for servo motor drive, was employed to suppressi control of the impact drop disturbance. The main advantage of the observer is that a fast response disturbance estimation is obtained using the detected motor cuttent and speed. And the new M/T method for motor speed detection is proposed. The method should be able to reduce the detection dead time compared with the Ohmae's M/T method. Also, the low speed control of a servo motor using instantaneous speed detection method is described. To estimate the instantaneous speed from the average speed, the speed estimator of the first order is proposed. Actually we confirmed that these methods improve the speed control performance of the servo system with experiments.

• 전기학회논문지
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• 제65권5호
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• pp.895-901
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• 2016

Nowadays, the axle counter has been developed to the wide range of the track circuit blocks as well as the wheel detection device. The axle counter, as becoming an important device for the high speed railway, must be guaranteed in accordance with the safety. With considering the safety and the high speed, performance evaluation a wheel detection sensor is described in this paper. To increase the safety, digital proximity sensor instead of analog is employed in the wheel detection sensor. Therefor the wheel detection sensor can minimize noisy signals caused by the harsh railway environments. And, to meet the high speed railway requirements, the performance of the wheel detection sensor is also successfully verified using the speed simulator at the velocity 500Km/h.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.88-94
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• 2007

This study deals with on-line fault detection and diagnosis for heat exchanger of variable speed refrigeration system. Conventional studies about fault of heat exchanger in refrigeration system have used temperature and pressure information. The temperature and pressure are able to be used valuably for faults detection of constant speed refrigeration system. However in case of variable speed refrigeration system, the temperature and pressure are no longer useful information for fault detection due to compensation effect of feedback controller. While current information is possible to detect faults of variable speed refrigeration system. The current information was detected in an inverter, it was used after transforming rms value. The faults of variable speed refrigeration system are divided into electrical faults and mechanical faults. We performed fault detection and diagnosis about heat exchanger among mechanical faults such as condenser fouling and evaporator fan fouling through some experiments.

• Smart Structures and Systems
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• 제30권3호
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• pp.303-315
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• 2022

The degradation of wheel tread may result in serious hazards in the railway operation system. Therefore, timely wheel defect diagnosis of in-service trains to avoid tragic events is of particular importance. The focus of this study is to develop a novel wheel defect detection approach based on the relevance vector machine (RVM) which enables online detection of potentially defective wheels with trackside monitoring data acquired under different running-speed conditions. With the dynamic strain responses collected by a trackside monitoring system, the cumulative Fourier amplitudes (CFA) characterizing the effect of individual wheels are extracted to formulate multiple probabilistic regression models (MPRMs) in terms of multi-kernel RVM, which accommodate both variables of vibration frequency and running speed. Compared with the general single-kernel RVM-based model, the proposed multi-kernel MPRM approach bears better local and global representation ability and generalization performance, which are prerequisite for reliable wheel defect detection by means of data acquired under different running-speed conditions. After formulating the MPRMs, we adopt a Bayesian null hypothesis indicator for wheel defect identification and quantification, and the proposed method is demonstrated by utilizing real-world monitoring data acquired by an FBG-based trackside monitoring system deployed on a high-speed trial railway. The results testify the validity of the proposed method for wheel defect detection under different running-speed conditions.

• 센서학회지
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• 제6권4호
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• pp.280-289
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• 1997

엔코더를 사용한 모터의 속도 검출은 저속에서 엔코더의 스텝과 스텝사이의 간격이 넓어서 속도와 회전방향을 정확히 검출하기 어렵다. 따라서 저속에서 좀 더 정확한 속도정보를 얻기위한 여러 가지의 속도추정기술들이 발표되었다. 또한 저속에서는 회전방향의 검출이 속도의 측정만큼이나 중요하다. 그러나 기존의 방향판별회로는 엔코더 펄스 1주기에 1번씩만 방향을 검출하므로 시간지연이 크기때문에 정확한 검출이 힘들다. 따라서 본 논문에서는 각각의 엔코더 펄스의 상승과 하강천이시마다 회전방향을 검출해 엔코더 펄스 1주기에 4번씩 검출할 수 있는 2중천이 검출방식을 제안한다. 그러므로 제안된 회로를 사용하면 기존의 회로보다 검출시간을 1/4로 단축시킬 수 있어 보다 정확한 속도와 회전방향의 검출이 가능하다. 그리고 제안된 회로의 성능과 효과를 시뮬레이션과 실험을 통해 확인하고 기존회로와의 비교를 통해 결과들을 분석한다.

• 대한교통학회지
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• 제19권6호
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• pp.7-17
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• 2001

본 연구는 교통관리 시스템의 유고검지 체계를 검토하여 기존 체계의 문제점과 한계점을 극복할 수 있는 새로운 검지체계를 구축하고 새로 구축된 검지 체계에 맞는 알고리즘을 개발하는데 연구 목적이 있다. 새로운 검지체계는 검지기 1개소의 설치로 다차로를 검지할 수 있으며 특히 1개 차로 내에서도 검지영역을 여러 개 검지할 수 있는 다 검지체계의 장점을 최대한 살린 시스템이므로 기존 체계의 한계성인 단일 검지영역 문제를 해소할 수 있으며 경제적으로 교통관리 시스템을 구축할 수 있는 장점을 가지고 있다. 이 시스템으로 고속도로와 국도상에서 유고 검지율을 기존의 APID와 DES를 비교하여 현장 시험 평가한 결과 이 시스템이 제일 높은 유고 검지율을 나타내어 기존 시스템보다 우수한 것으로 판명되었다.

• IEIE Transactions on Smart Processing and Computing
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• 제4권4호
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• pp.237-250
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• 2015

This paper describes a hardware-oriented algorithm and its conceptual implementation in a real-time speed limit traffic sign detection system on an automotive-oriented field-programmable gate array (FPGA). It solves the training and color dependence problems found in other research, which saw reduced recognition accuracy under unlearned conditions when color has changed. The algorithm is applicable to various platforms, such as color or grayscale cameras, high-resolution (4K) or low-resolution (VGA) cameras, and high-end or low-end FPGAs. It is also robust under various conditions, such as daytime, night time, and on rainy nights, and is adaptable to various countries' speed limit traffic sign systems. The speed limit traffic sign candidates on each grayscale video frame are detected through two simple computational stages using global luminosity and local pixel direction. Pipeline implementation using results-sharing on overlap, application of a RAM-based shift register, and optimization of scan window sizes results in a small but high-performance implementation. The proposed system matches the processing speed requirement for a 60 fps system. The speed limit traffic sign recognition system achieves better than 98% accuracy in detection and recognition, even under difficult conditions such as rainy nights, and is implementable on the low-end, low-cost Xilinx Zynq automotive Z7020 FPGA.

• 전기학회논문지P
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• 제64권3호
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• pp.193-198
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• 2015

A large number of vision applications rely on matching keypoints across images. Pedestrian detection is under constant pressure to increase both its quality and speed. Such progress allows for new application. A higher speed enables its inclusion into large systems with extensive subsequent processing, and its deployment in computationally constrained scenarios. In this paper, we focus on improving the speed of pedestrian detection using HOG(histogram of oriented gradient) and multi frame operation which is robust to illumination changes in cluttering images. The result of our simulation indicates that the detection rate and speed of the proposed method is much faster than that of conventional HOG and differential images.