• Title, Summary, Keyword: mode acceleration method

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Output-only modal parameter identification for force-embedded acceleration data in the presence of harmonic and white noise excitations

  • Ku, C.J.;Tamura, Y.;Yoshida, A.;Miyake, K.;Chou, L.S.
    • Wind and Structures
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    • v.16 no.2
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    • pp.157-178
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    • 2013
  • Output-only modal parameter identification is based on the assumption that external forces on a linear structure are white noise. However, harmonic excitations are also often present in real structural vibrations. In particular, it has been realized that the use of forced acceleration responses without knowledge of external forces can pose a problem in the modal parameter identification, because an external force is imparted to its impulse acceleration response function. This paper provides a three-stage identification procedure as a solution to the problem of harmonic and white noise excitations in the acceleration responses of a linear dynamic system. This procedure combines the uses of the mode indicator function, the complex mode indication function, the enhanced frequency response function, an iterative rational fraction polynomial method and mode shape inspection for the correlation-related functions of the force-embedded acceleration responses. The procedure is verified via numerical simulation of a five-floor shear building and a two-dimensional frame and also applied to ambient vibration data of a large-span roof structure. Results show that the modal parameters of these dynamic systems can be satisfactorily identified under the requirement of wide separation between vibration modes and harmonic excitations.

Structural Dynamic Analysis by Ritz Vector Method Modified with Lanczos Algorithm (Lanczos 알고리즘을 도입한 Ritz Vector법에 의한 구조물의 동적해석)

  • 심재수;황의승;박주경
    • Computational Structural Engineering
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    • v.8 no.4
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    • pp.181-187
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    • 1995
  • Recent researches in dynamics are focused on finding effective methods to analyze the dynamic behavior of structures by fewer mode shapes their number of dgrees of freedom. Ritz algorithm and mode acceleration method were developed to improved the mode superposition. Ritz algorithm can include distribution of external loads but be apt to lose the orthogonality condition, which is useful properties in the analysis. Also mode acceleration method should consider a large number of mode shapes to get a satisfactory results. Another method, combining previous two method, was developed but too much computational efforts and times were required. The purpose of this study is to develop and evaluate the Ritz algorithm modified with the lanczos algorithm to improve the efficiency and accuracy. As a result of !this study, dynamic analysis using modified Ritz algorithm was proved to be the rational analysis method.

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Suggested Accelerated Life Test Method of SMPS for Outdoor Lighting LED (실외조명 LED용 SMPS의 가속수명시험법 제안)

  • Lim, Seong-Yong;Hyong, Jae-Phill;Lim, Hong-Woo;Oh, Geun-Tae
    • Journal of Applied Reliability
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    • v.18 no.1
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    • pp.8-19
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    • 2018
  • Purpose: This study has developed the accelerated lifetime test method for smps for outdoor lighting LED through two factors of temperature and humidity. Methods: Acceleration condition was confirmed for each stress and model, and acceleration life test model was estimated according to acceleration condition. Results: As a result of confirming the accelerated life test model, in the case of humidity, acceleration was established only in the foreign products. Therefore, it is confirmed that the acceleration condition is insufficient. However, the estimated parameters for temperature are relatively constant. It is therefore suitable for power supply acceleration tests for outdoor lighting LEDs. Conclusion: The SMPS acceleration test for outdoor lighting LED can improve the availability of the product by developing an accelerated life test method that guarantees the reliability of the product.

Dynamic Analysis for Mechanical Systems with Multi-Degree of Freedom under Base Excitation Using Relative Acceleration (상대 가속도를 이용한 기초 가진을 받는 다자유도 기계 시스템의 동적 해석)

  • Lee, Tae Won
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.19 no.3
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    • pp.36-41
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    • 2020
  • Mechanical systems installed in transport devices, such as vehicles, airplanes, and ships, are mostly subject to translational accelerations at the joints during operations. This base acceleration excitation has a large influence on the performance of the system, therefore, its response must be well analyzed. However, the existing methods for dynamic analysis of structures have some limitations in use. This study presents a new numerical method using relative acceleration to solve these limitations. If the governing equation of motion is linear and the mass matrix, the damping matrix, and the stiffness matrix are constant over time in the finite element analysis, the proposed method can be applied to the transient behavior analysis and the harmonic response analysis of the structure. Because it is not necessary to introduce a virtual mass and the rigid body motions are removed from the analysis, it is possible to use not only the direct integration method in the time domain but also the mode superposition method to obtain the dynamic responses. This paper demonstrates with three examples how the present method is suitable for the dynamic analysis of a structure with multi-degree of freedom.

Extraction of bridge information based on the double-pass double-vehicle technique

  • Zhan, Y.;Au, F.T.K.;Yang, D.
    • Smart Structures and Systems
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    • v.25 no.6
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    • pp.679-691
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    • 2020
  • To identify the bridge information from the response of test vehicles passing on it (also known as the indirect approach) has aroused the interest of many researchers thanks to its economy, easy implementation and less disruption to traffic. The surface roughness of bridge remains an obstacle for such method as it contaminates the vehicle response severely and thereby renders many vehicle-response-based bridge identification methods ineffective. This study aims to eliminate such effect with the responses of two different test vehicles. The proposed method can estimate the surface profile of a bridge based on the acceleration data of the vehicles running on the bridge successively, and obtain the normalized contact point response, which proves to be relatively immune to surface roughness. The frequencies and mode shapes of bridge can be further extracted from the normalized contact point acceleration with spectral analysis and Hilbert transform. The effectiveness of the proposed method is verified numerically with a three-span continuous bridge. The influence of measurement noise is also examined.

A Study on the Characteristics of Smoke Emissions from Heavy Duty Diesel Vehicles Using a Chassis Dynamometer (차대동력계를 이용한 대형 디젤 차량의 매연 배출 특성 연구)

  • Jin, Kwang-Suk;Lee, Choong-Hoon
    • Journal of the Korean Society of Safety
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    • v.24 no.4
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    • pp.1-10
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    • 2009
  • The characteristics of smoke emissions from diesel heavy duty vehicles which weigh over 5.5 tons was investigated by driving the vehicles with both the Lugdown 3 modes in the chassis dynamometer and tree accelerating mode under no load. The vehicles include commercial vehicles such as bus, microbus, trucks and specialized vehicles, etc. The total numbers of the vehicles tested were 200. The light extinction method was used to measure the smoke emissions from the vehicles tail pipe. The values of the smoke emissions in the tree accelerating mode showed $0{\sim}20%$ band nearly independent of both the mileage and year of production of the tested vehicles, while those in the Lugdown 3 modes showed $0{\sim}99%$ of wide band. The correlation coefficients between the values of the smoke emissions with both the Lugdown 3 modes and the free acceleration mode were 0.12, 0.08, 0.12, respectively. The inspection with Lugdown 3 modes is better one than that with tree acceleration from the point of exact inspection of the diesel vehicles' smoke emission.

Design of Zigbee based Portable ECG monitoring system (지그비 기반의 휴대형 심전도 모니터링 시스템 설계)

  • Hong, Joo-Hyun;Kim, Nam-Jin;Cha, Eun-Jong;Lee, Tae-Soo
    • Proceedings of the KIEE Conference
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    • pp.51-53
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    • 2006
  • This paper proposes a portable ECG monitoring system, which integrates uptodate PDA and RF communication technology. The aim of the study is to acquire the subject's biomedical signal without any constraint. It has two types of transmission mode, which are total signal transmission mode and HR(heart rate)/SC(step count) transmission mode. In audition, wireless communication technology uses Zigbee Wireless PAN and can work in low-power mode, which is one of the advantages of ZiBbee communication technology. The developed system is composed of a transmitter and a receiver. The transmitter has three-axial acceleration sensor. ECG amplifier and Zigbee communication controller. In total signal transmission mode, it can send data 50 packets per second whose transmission speed corresponds to 300 ECG samples and 60 acceleration samples. In HR/SG transmission mode, it can calculate heart rate from EEG data with 216 samples per second and step count from acceleration data and send a packet every cardiac cycle. The receiver forwards the received data to PDA, where the data can be stored and displayed. Therefore, the developed device enables to continuous monitoring for Activities of Daily Living(ADL). Also, this method will reduce medical costs in the aged society.

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Characteristics of Smoke Emissions from Light Duty Diesel Vehicles Using Light Extinction Smoke Measurement Method under free Acceleration Test Mode (광투과식 매연 측정법을 이용한 소형 디젤 차량의 무부하 급가속 조건에서의 매연 배출 특성)

  • Kang, Il-Ho;Lee, Choong-Hoon
    • Journal of the Korean Society of Safety
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    • v.27 no.3
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    • pp.1-8
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    • 2012
  • Characteristics of smoke emission in light duty diesel vehicles was investigated according to the year of production, engine displacement volume, and mileage. The smoke emission was measured using light extinction smoke measurement method under free acceleration test mode. Total number of the tested vehicles was 180. The year of production of the tested vehicles distributed from 2002 to 2007. The displacement volumes of the tested vehicles were categorized as 2-liter, 2.5-liter, 2.7-liter, and 3-liter. The mileage of the tested vehicles distributed from 20,000 km to 400,000 km. The more recent in the year of production of the tested vehicles did not show clearly lower in smoke emissions. Smoke emission showed different values according to driver's pedal pushing pattern. Also, smoke emission peak for each free acceleration test initially increased and reach a maximum of the peak values. Afterwards, the smoke peak gradually decreased as number of test increased. A new guide line was proposed to determine the smoke value from the light duty diesel vehicles based on smoke emission peak patterns which were obtained with several repeated free acceleration tests.

Precise position control with a low cost BLDCM drive (저가형 BLDCM 구동장치를 이용한 정밀위치제어)

  • 강석주;김준석;설승기;김덕근
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.44 no.4
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    • pp.447-452
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    • 1995
  • In this paper a simple method of a position control for brushless DC motor is presented. For precise position control, a high performance torque controller is needed and a novel current control method is proposed. The current controller detects the uncommutating mode current for every 60.deg. (elec. angle) and controls it with PI controller. The current control loop includes the feedforward of back EMF and the feedforward of the neutral voltage between the neutral point of the inverter and the neutral point of the machine. In the position control, the acceleration pattern is calculated from the position reference. Then the speed trajectory is calculated from the acceleration pattern. The experimental results are presented to verify the proposed methods.

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Development of Accelerated Life Test Method for Constant Electrical Potential Electrolysis Gas Sensor (정전위 전해식 가스센서의 가속수명시험법 개발)

  • Yang, Il Young;Kang, Jun Gu;Yu, Sang Woo;Oh, Geun Tae;Na, Yoon Gyoon
    • Journal of Applied Reliability
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    • v.16 no.3
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    • pp.180-191
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    • 2016
  • Purpose: The purpose of this study was to develop the accelerated life test method for Constant Electrical Potential Electrolysis gas sensor (CEPE gas sensor). Methods: The parts and modules of CEPE gas sensor were analyzed by using Reliability Block Diagram (RBD). Failure Mode and Effect Analysis (FMEA) and Quality Function Deployment (QFD) methods were performed for each part to determine the most affecting stress factor in its life cycle. The long term testing was conducted at three different dry heat levels and the acceleration factor was developed by using Arrhenius relationship. Conclusion: The acceleration factor for CEPE gas sensor was developed by using FMEA, QFD, and statistical analysis for its failure data. Also qualification tests were designed to meet the target life.