• 한국항행학회논문지
• /
• 제8권1호
• /
• pp.26-37
• /
• 2004

차분 위성 항법에 있어서 빈번한 동적 변화를 수반하는 항체에 대하여 편향되지 않은 위치 추정치를 생성하기 위해서는 위상 평활화 코드 필터가 널리 사용되고 있다. 위치추정, 오차해석, 고장진단, 그리고 미지정수 결정 등 보정위성항법시스템의 다양한 응용분야에 있어서 정확한 오차공분산 정보는 중요한 역할을 담당한다. 반면, 기존의 위상 평활화 코드 필터 알고리즘들은 대부분 누적위상 측정오차에 의한 시전달 오차를 무시하므로 실재에 비하여 낙관적인 오차공분산 정보를 생성할 위험성을 내포하고 있다. 위상 평활화 코드 기법의 활용에 있어서 일관성 있고 적절한 오차공분산 정보를 생성하기 위하여 본 논문에서는 Stepwise Optimal Position Projection Filter와 Stepwise Unbiased Position Projection Filter 알고리즘을 제안하였다. 제안된 필터는 기존의 필터에 비하여 누적위상의 특성에 기인하는 시전달 오차의 특성을 정확하고 상세하게 고려하여 주며 잦은 가시위성의 변화도 함께 고려할 수 있는 장점을 가진다. 몬테카를로 시뮬레이션에 의하여 수신기 Kalman 필터, 기존의 위상 평활화 코드 필터, 그리고 제안된 두 필터들의 성능을 비교 분석 하였다.

• 대한기계학회논문집A
• /
• 제22권3호
• /
• pp.688-694
• /
• 1998

The ability to locate the defects in materials is one of the major attrations of the acoustic emission(AE) technique. The most conventional method for planar AE source localization is to place three or more AE sensors on the plate and to determine the source position by measuring the differences in the arrival times of the AE wave at the sensors, which is called as triangulation method. But this method can not be applied in the material of which elastic wave propagtion velocity is not known. In this paper, we propose two methods, vector method and error minimization method, for AE source location on the material with unknown AE wave velocity. In this method, it is not needed to know the propagation velocity previously, that is, we can apply this method to arbitrary material of which properties are not known exactly. Also, in this paper, the robustness to the error in the measurement of time differences are discussed for both methods. Finally, in order to evaluate the actual performances, experiments using a pencil lead break as the AE source were carried out on the aluminum plate.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권2호
• /
• pp.988-1001
• /
• 2018

Arrhythmia has recently emerged as one of the major causes of death in Koreans. Premature Ventricular Contraction (PVC) is the most common arrhythmia that can be found in clinical practice, and it may be a precursor to dangerous arrhythmias, such as paroxysmal insomnia, ventricular fibrillation, and coronary artery disease. Therefore, we need for a method that can detect an abnormal heart beat and diagnose arrhythmia early. We extracted the features corresponding to the QRS pattern from the subject's ECG signal and classify the premature ventricular contraction waveform using the features. We modified the weighting and bias values based on the error back-propagation algorithm through learning data. We classify the normal signal and the premature ventricular contraction signal through the modified weights and deflection values. MIT-BIH arrhythmia data sets were used for performance tests. We used RR interval, QS interval, QR amplitude and RS amplitude features. And the hidden layer with two nodes is composed of two layers to form a total three layers (input layer 0, output layer 3).

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제17권1호
• /
• pp.65-78
• /
• 2017

Single Event Transient has a critical impact on highly integrated logic circuits which are currently common in various commercial and consumer electronic devices. Reliability against the soft and intermittent faults will become a key metric to evaluate such complex system on chip designs. Our previous work analyzing soft errors was focused on parallelizing and optimizing error propagation procedures for individual transient faults on logic and sequential cells. In this paper, we present a new propagation technique where a fault binary decision diagram (BDD) continues to merge every new fault generated from the subsequent logic gate traversal. BDD-based transient fault analysis has been known to provide the most accurate results that consider both electrical and logical properties for the given design. However, it suffers from a limitation in storing and handling BDDs that can be increased in size and operations by the exponential order. On the other hand, the proposed method requires only a visit to each logic gate traversal and unnecessary BDDs can be removed or reduced. This results in an approximately 20-200 fold speed increase while the existing parallelized procedure is only 3-4 times faster than the baseline algorithm.

• Journal of Power Electronics
• /
• 제8권4호
• /
• pp.354-362
• /
• 2008

This paper presents neural load torque compensation method which is composed of a deadbeat load torque observer and gains compensation by a parameter estimator. As a result, the response of the PMSM (permanent magnet synchronous motor) obtains better precision position control. To reduce the noise effect, the post-filter is implemented by a MA (moving average) process. The parameter compensator with an RLSM (recursive least square method) parameter estimator is adopted to increase the performance of the load torque observer and main controller. The parameter estimator is combined with a high performance neural load torque observer to resolve problems. The neural network is trained in online phases and it is composed by a feed forward recall and error back-propagation training. During normal operation, the input-output response is sampled and the weighting value is trained multi-times by the error back-propagation method at each sample period to accommodate the possible variations in the parameters or load torque. As a result, the proposed control system has a robust and precise system against load torque and parameter variation. Stability and usefulness are verified by computer simulation and experiment.

• 한국산업융합학회 논문집
• /
• 제8권2호
• /
• pp.97-104
• /
• 2005

Usually, propagation attenuation of millimeter wave occurs by rainfall, snowfall, temperature, effect of pressure of air. In 60GHz wave band wireless communication network, temperature change becomes big factor of propagation loss department. Also, temperature change causes disturbance of 60GHz frequency at transceiver. In this study, we used 60GHz transceiver and found propagation loss of wireless path and operating frequency disturbance characteristics. In transceiver that there is no temperature compensated device, operating frequency of TX changed by 60.865GHz at temperature of $-5^{\circ}C$, and appeared by 60.730GHz when is $50^{\circ}C$. Therefore, operating frequency change width by temperature change are about 100MHz, greatly. But, in transceiver that there is temperature compensated device, operating frequency of TX changed by 60.830GHz at temperature of $-5^{\circ}C$, and appeared by 60.710GHz when is $50^{\circ}C$. Therefore, operating frequency change width by temperature change are about 20MHz. According to these result, we constructed between buildings examination wireless site for point to point wireless communication using 60GHz band transceivers who have do temperature compensated device, and investigated data transmission characteristics about ambient temperature change. Therefore, if use transceiver that have temperature compensated device, may overcome the wireless transmission error in 60GHz band wireless communication LAN networks despite of ambient temperature change.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제49권8호
• /
• pp.557-564
• /
• 2000

A very simple control approach using neural network for the robust position control of a Permanent Magnet Synchronous Motor(PMSM) is presented. The linear quadratic controller plus feedforward neural network is employed to obtain the robust PMSM system approximately linearized using field-orientation method for an AC servo. The neural network is trained in on-line phases and this neural network is composed by a feedforward recall and error back-propagation training. Since the total number of nodes are only eight, this system can be easily realized by the general microprocessor. During the normal operation, the input-output response is sampled and the weighting value is trained multi-times by error back-propagation method at each sample period to accommodate the possible variations in the parameters or load torque. In addition, the robustness is also obtained without affecting overall system response. This method is realized by a floating-point Digital Signal Processor DS1102 Board (TMS320C31).

• 한국항공우주학회지
• /
• 제49권6호
• /
• pp.515-519
• /
• 2021

IEEE 1588 PTP는 두 시스템이 GPS의 도움 없이 송수신 시간 정보를 포함한 패킷을 주고받으면서 동기화하는 정밀 시각 프로토콜인데 시각 동기화 과정에서 전파 지연 시간을 계산하고 이를 이용하여 두 시스템 간의 거리를 측정할 수 있다. 본 논문에서는 수신 패킷의 프리앰블에서 추출한 타이밍 오류 정보를 이용하여 변조 심벌 주기 이하로 거리 측정 정밀도를 향상하는 방법을 제안하였다. 컴퓨터 시뮬레이션을 통해 거리 측정 정밀도는 프리앰블 PN 시퀀스의 길이와 신호대잡음비에 비례하는 것을 보였다.

• 대한기계학회논문집A
• /
• 제25권12호
• /
• pp.2040-2047
• /
• 2001

In this paper, a singularity problem of the state transition matrix is investigated in the spatial propagation when the spatial matrix differential equation is constructed via time finite element analysis. A parametric study shows that the degree of singularity of the state transition matrix depends on the degree of flexibility of the structures. As an alternative to avoid the numerical problems due to the singularity, an analytic solution fur spatial propagation of the flexible structures is proposed. In the proposed method, the spatial properties of the structure are analytically expressed by a combination of transcendental functions. The analytic solution serves fast and accurate results by eliminating the possibility of the error accumulation caused by the boundary condition. Several numerical examples are shown to validate the effectiveness of the proposed methods.

• Journal of Astronomy and Space Sciences
• /
• 제16권2호
• /
• pp.159-166
• /
• 1999

As the spatial resolution of remote sensing satellites becomes higher, very accurate determination of the position of a LEO (Low Earth Orbit) satellite is demanding more than ever. Non-symmetric Earth gravity is the major perturbation force to LEO satellites. Since the orbit propagation is performed in the celestial frame while Earth gravity is defined in the terrestrial frame, it is required to convert the coordinates of the satellite from one to the other accurately. Unless the coordinate conversion between the two frames is performed accurately the orbit propagation calculates incorrect Earth gravitational force at a specific time instant, and hence, causes errors in orbit prediction. The coordinate conversion between the two frames involves precession, nutation, Earth rotation and polar motion. Among these factors, unpredictability and uncertainty of Earth rotation, called UTI-UTC, is the largest error source. In this paper, the effect of UTI-UTC on the accuracy of the LEO propagation is introduced, tested and analzed. Considering the maximum unpredictability of UTI-UTC, 0.9 seconds, the meaningful order of non-spherical Earth harmonic functions is derived.