• Title/Summary/Keyword: actual error

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Analysis of Phase Error Effects Due to Grid Frequency Variation of SRF-PLL Based on APF

  • Seong, Ui-Seok;Hwang, Seon-Hwan
    • Journal of Power Electronics
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    • v.16 no.1
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    • pp.18-26
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    • 2016
  • This paper proposes a compensation algorithm for reducing a specific ripple component on synchronous reference frame phase locked loop (SRF-PLL) in grid-tied single-phase inverters. In general, SRF-PLL, which is based on all-pass filter to generate virtual voltage, is widely used to estimate the grid phase angle in a single-phase system. In reality, the estimated grid phase angle might be distorted because the phase difference between actual and virtual voltages is not 90 degrees. That is, the phase error is caused by the difference between cut-off frequency of all-pass filter and grid frequency under grid frequency variation. Therefore, the effects on phase angle and output current attributed to the phase error are mathematically analyzed in this paper. In addition, the proportional resonant (PR) controller is adapted to reduce the effects of phase error. The validity of the proposed algorithm is verified through several simulations and experiments.

Studies on the Improvement and Analysis of Data Entry Error to the AIS System for the Traffic Ships in the Korean Coastal Area (우리나라 연안해역을 통항하는 선박에 대한 AIS 데이터 입력 오류의 분석 및 개선 방안 연구)

  • JEON, Jae-Ho;JEONG, Tae-Gweon
    • Journal of Fisheries and Marine Sciences Education
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    • v.28 no.6
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    • pp.1812-1821
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    • 2016
  • The purpose of this study is to survey input data error of ship automatic identification system (AIS) and suggest its improvement. The effects of AIS were observed. Input data error of AIS was investigated by dividing it into dynamic data, static data by targeting actual ships and its improvement method was suggested. The findings are as follows. Looking into accidents before and after AIS is enforced to install on the ship, total collision were decreased after AIS installed. Static data error of AIS took place mainly in the case that ship name, call sign, MMSI, IMO number, ship type, location of antenna (ship length and width) were wrongly input or those data were not input initially. Dynamic data error of AIS was represented by input error of ship's heading. As errors of voyage related data take place as well, confusion is made in sailing or ship condition. Counter measures against the above are as follows. First, reliability of AIS data information should be improved. Second, incessant concern and management should be made on the navigation officers.

RFID Indoor Location Recognition with Obstacle Using Neural Network (신경망을 이용한 장애물이 있는 RFID 실내 위치 인식)

  • Lee, Jong-Hyun;Lee, Kang-bin;Hong, Yeon-chan
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.22 no.11
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    • pp.1442-1447
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    • 2018
  • Since the indoor location recognition system using RFID is a method for predicting the indoor position, an error occurs due to the surrounding environment such as an obstacle. In this paper, we plan to reduce errors using back propagation neural networks. The neural network adjusts and trains the connection values between the layers to reduce the error between the actual position of the object with the reader and the expected position of the object through the experiment. In this paper, we propose a method that uses the median method and the radiation method as input to the neural network. Among the two methods, we want to find out which method is more effective in recognizing the actual position in an environment with obstacles and reduce the error. Consequently, the method using the median has less error, and we confirmed that the more the number of data, the smaller the error.

A Study on the Actual Equilibrium Analysis for Membrane Structures (막구조물의 준공평형 형상해석에 관한 연구)

  • 이장복;김재열;권택진
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2000.04b
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    • pp.61-68
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    • 2000
  • In general, the design of membrane structures takes three steps. The first is shape finding analysis which is determination of initial equilibrium geometry with uniform stresses. The second step involve the computation of the stress-deformation to get completed membrane under various load conditions. The third step is to divide the membrane structures into several plan strips from the initial equilibrium states. This procedure is needed because of the initial shape has usually undevelopable curved surface and is called as "cutting patterns generation". By introducing this work, the deformation due to the initial stress is removed and approximate cutting patterns are generated. In this approach, however, material properties is not considered, therefore the error between the design stresses and actual stresses during the fabrication of plan strips should be occurred. In this paper, actual equilibrium shape analysis procedure for HP shape models is presented. The deviations of stresses between the design stresses and actual stresses are estimated.

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Minimum Number of Input Ground-motions to Assess Seismic Performance of Nuclear Facilities (원전시설의 내진성능평가를 위한 입력지반운동의 최소개수)

  • Hong, Kee-Jeung;Choi, Ji-Hae;Kim, Hyun-Uk;Joo, Kwang-Ho
    • Journal of the Earthquake Engineering Society of Korea
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    • v.20 no.5
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    • pp.341-349
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    • 2016
  • Currently, researches are being actively conducted in assessing seismic performance of nuclear facilities in USA and Europe. In particular, applying this technique of assessing seismic performance to design of isolation systems in nuclear power plants is being performed and then ASCE 4 Draft (2013) is being revised accordingly in the United States. In order to satisfy the probabilistic performance objectives described by seismic responses with certain confidence levels (ASCE 43, 2005), the probability distributions of these responses have to be defined. What is the minimum number of input ground-motions to obtain the probability distribution precise enough to represent the unknown actual distribution? Theoretical basis, for how to determine the minimum number of input ground-motions for given a logarithmic standard deviation to approximate the unknown actual median of the log-normal distribution within a range of error at a certain level of confidence, is introduced by Huang et al. (2008). However, the relationship between the level of confidence and the range of error is not stated in the previous study. In this paper, based on careful reviews on the previous work, the relationship between the level of confidence and the range of error is logically and explicitly stated. Furthermore, this relationship is also applied to derive the minimum number of input ground-motions in order to approximate the unknown actual logarithmic standard deviation. Several recommendations are made for determining the minimum number of input ground-motions in probabilistic assessment on seismic performance of facilities in nuclear power plants.

Measurement and Compensation of Heliostat Sun Tracking Error Using BCS (Beam Characterization System) (광특성분석시스템(BCS)을 이용한 헬리오스타트 태양추적오차의 측정 및 보정)

  • Hong, Yoo-Pyo;Park, Young-Chil
    • Journal of Institute of Control, Robotics and Systems
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    • v.18 no.5
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    • pp.502-508
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    • 2012
  • Heliostat, as a concentrator to reflect the incident solar energy to the receiver, is the most important system in the tower-type solar thermal power plant since it determines the efficiency and ultimately the overall performance of solar thermal power plant. Thus, a good sun tracking ability as well as a good optical property of it are required. Heliostat sun tracking system uses usually an open loop control system. Thus the sun tracking error caused by heliostat's geometrical error, optical error and computational error cannot be compensated. Recently use of sun tracking error model to compensate the sun tracking error has been proposed, where the error model is obtained from the measured ones. This work is a development of heliostat sun tracking error measurement and compensation method using BCS (Beam Characterization System). We first developed an image processing system to measure the sun tracking error optically. Then the measured error is modeled in linear polynomial form and neural network form trained by the extended Kalman filter respectively. Finally error models are used to compensate the sun tracking error. We also developed the necessary image processing algorithms so that the heliostat optical properties such as maximum heat flux intensity, heat flux distribution and total reflected heat energy could be analyzed. Experimentally obtained data shows that the heliostat sun tracking accuracy could be dramatically improved using either linear polynomial type error model or neural network type error model. Neural network type error model is somewhat better in improving the sun tracking performance. Nevertheless, since the difference between two error models in compensation of sun tracking error is small, a linear error model is preferred in actual implementation due to its simplicity.

A Study on the Machining Error Characteristics in Ball-End Milling of Surface (곡면의 볼 엔드밀 가공에서 가공오차 특성에 관한 연구)

  • Sim, Ki-Joung;Yu, Jong-Sun;Yu, Ki-Hyun;Cheong, Chin-Yong
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.3 no.1
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    • pp.7-14
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    • 2004
  • Machining error is defined the normal distance between designed surface and actual tool path with tool deflection. This is inevitably caused by the tool deflection, tool wear, thermal effect and machine tool errors and so on. Among these factors, tool deflection is usually known as the most significant factor of machining error. Tool deflection problem is analyzed using Instantaneous horizontal cutting forces. The high quality and precision of machining products are required in finishing. In order to achieve these purposes, it is necessary work that decrease the machining error. This paper presents a study on the machining error caused by the tool deflection in ball end milling of 2 dimensional surface. Tool deflection model and simple machining error prediction model are described. This model is checked the validity with machining experiments of 2 dimensional surface. These results may be used to decrease machining error and tool path decision.

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A Case Study of Marine Accident Investigation and Analysis with Focus on Human Error (해양사고조사를 위한 인적 오류 분석사례)

  • Kim, Hong-Tae;Na, Seong;Ha, Wook-Hyun
    • Journal of the Ergonomics Society of Korea
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    • v.30 no.1
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    • pp.137-150
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    • 2011
  • Nationally and internationally reported statistics on marine accidents show that 80% or more of all marine accidents are caused fully or in part by human error. According to the statistics of marine accident causes from Korean Maritime Safety Tribunal(KMST), operating errors are implicated in 78.7% of all marine accidents that occurred from 2002 to 2006. In the case of the collision accidents, about 95% of all collision accidents are caused by operating errors, and those human error related collision accidents are mostly caused by failure of maintaining proper lookout and breach of the regulations for preventing collision. One way of reducing the probability of occurrence of the human error related marine accidents effectively is by investigating and understanding the role of the human elements in accident causation. In this paper, causal factors/root causes classification systems for marine accident investigation were reviewed and some typical human error analysis methods used in shipping industry were described in detail. This paper also proposed a human error analysis method that contains a cognitive process model, a human error analysis technique(Maritime HFACS) and a marine accident causal chains, and then its application to the actual marine accident was provided as a case study in order to demonstrate the framework of the method.

Quality Check Monitoring System for Advancing the Yield Rate based on Sensor (베어링 생산수율 향상을 위한 센서기반 품질 체크 모니터링 장치)

  • Xiang, Zhao;Yoon, Dal-Hwan
    • Journal of IKEEE
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    • v.23 no.1
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    • pp.22-28
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    • 2019
  • This paper presents the monitoring method of machining error and quality check to improve the productivity of boring manufacturing process. Machining error usually appears as the offset of spatial location of actual cutting path compared to ideal cutting path. In order to monitor an error of workpiece, multiple factors affecting quality of boring, such as distortion of workpiece, clamping error, radial rotation error of the spindle and motion error of machine tools, were took into account. To verify the productive quality, we propose the quality check system. The system based on IT convergence analyzes the process error rate and saves the analyzed data in memory. Also, these play important roles in detecting an inferior production goods and can decrease the production cost and loss of bearing.

A Study on Human Error Risk Analysis of Helicopter Frequent Accidents through AHP Method (AHP 방법을 통한 헬리콥터 다빈도 사고의인적오류 위험도 분석에 관한 연구)

  • TaeJung Yu
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.31 no.2
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    • pp.46-54
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    • 2023
  • Helicopter pilots are required to perform many visual workloads in topographical avoidance, flight path modification and navigation, because helicopters operate at very low altitudes. The helicopter-specific instability also require the pilot to have precise perception and control. This has caused frequent human error in helicopter accidents. In Korea, two to three cases have occurred annually on average over the past 10 years, and this trend has not decreased. The purpose of this study was to identify human error risks in advance to prevent helicopter accidents and to help develop measures for missions and mission phases with high risk of human error. Through the study, the tasks and mission phases where accidents occur frequently were classified and the risk of human error was calculated for each mission phases. To this end, the task of frequent accidents during helicopter missions was first identified, detailed steps were classified, and the number of accidents was analyzed. Next, the AHP survey program was developed to measure the pilot's risk of human error and the survey was conducted on the pilots. Finally, the risk of human error by helicopter mission and by mission phases calculated and compared with the actual number of accidents.