• Title, Summary, Keyword: Hold Time

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On the zeros of a multivariable discrete-time control system with approximate fractional order hold

  • Han, Seong-Ho;Yoshihiro, Takita
    • 제어로봇시스템학회:학술대회논문집
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    • pp.47.2-47
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    • 2001
  • This paper is concerned with the limiting zeros, as the sampling period tends to zero, of a multivariable discrete-time system composed of an approximate fractional-order hold (AFROH), a continuous-time plant and a sampler in cascade. An approximate fractional-order hold is proposed to implement fractional-order hold (FROH) and is applied to instead of the zero-order hold (ZOH). The implementing problem of the fractional-order hold is overcome. The properties of the limiting zeros are studied and the location problem of them is solved. In addition, a stability condition of the zeros for sufficiently small sampling period is derived ...

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PFC 컨버터에서의 hold-up time 제어 기법

  • Jang, Yu-Jin;Mun, Geon-U
    • Proceedings of the KIPE Conference
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    • pp.167-168
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    • 2014
  • 본 논문은 CCM PFC Boost 컨버터에서 부하의 크기에 상관없이 Hold-up 시점 에서, 회로의 안정적 동작 및 소음을 방지하는 보호회로를 제안 한다. 앰프 오프셋 저감 및 Hold-up time 보호 회로를 240W CCM Boost 컨버터에 적용 하여, Hold-up time에서 안정적 동작 및 소음이 없음을 확인하였다.

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Hold up Time Extension Technique for high efficiency, high power density server power supply (고효율 고밀도 서버용 전원장치를 위한 Hold up Time 보상 기술)

  • Kim, Young-Do;Cho, Kyu-Min;Moon, Gun-Woo
    • The Transactions of the Korean Institute of Power Electronics
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    • v.15 no.2
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    • pp.96-102
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    • 2010
  • Nowadays, climate change becomes serious problem in all around country. Especially because of global warming problem, every country is suffered from various natural disasters. To prevent these changes, every industry are keep requiring the increase in energy efficiency. Recently, in the regulation of CSCI (climate savers computing initiate), the efficiency of server power supply should meet the demand of 94% at 50% load condition by 2010, which is called platinum level. Hence, server power system has been dramatically developed with the various technique for the high efficiency of it. Among those technique, hold up time extension technique has received wide attention and has been researched for a long time. In this paper, technical trend of hold up time extension circuit will be covered for the high efficiency, high power density server power supply.

A Study on the Life Prediction Method using Artificial Neural Network under Creep-Fatigue Interaction (인공 신경망을 이용한 크리프-피로 상호작용시 수명예측기법에 관한 연구)

  • 권영일;김범준;임병수
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.6
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    • pp.135-142
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    • 2001
  • The effect of tensile hold time on the creep-fatigue interaction in AISI 316 stainless steel was investigated. To study the fatigue characteristics of the material, strain controlled low cycle fatigue(LCF) tests were carried out under the continuous triangular waveshape with three different total strain ranges of 1.0%, 1.5% and 2.0%. To study the creep-fatigue interaction, 5min., 10min., and 30min. of tensile hold times were applied to the continuous triangular waveshape with the same three total strain ranges. The creep-fatigue life was found to be the longest when the 5min. tensile hold time was applied and was the shortest when the 30min. tensile hold time was applied. The cause fur the shortest creep-fatigue life under the 30min. tensile hold time is believed to be the effect of the increased creep damage per cycle as the hold time increases. The creep-fatigue life prediction using artificial neural network(ANN) showed closer prediction values to the experimental values than by the modified Coffin-Manson method.

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Taylor Series Discretization Method for Input-Delay Nonlinear Systems

  • Zhang, Zheng;Chong, Kil-To
    • Proceedings of the KIEE Conference
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    • pp.152-154
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    • 2007
  • Anew discretization method for the input-driven nonlinear continuous-time system with time delay is proposed. It is based on the combination of Taylor series expansion and first-order hold assumption. The mathematical structure of the new discretization scheme is explored. The performance of the proposed discretization procedure is evaluated by case studies. The results demonstrate that the proposed discretization scheme can assure the system requirements even though under a large sampling period. A comparison between first order hold and zero-order hold is simulated also.

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Impact Analysis of Communication Time Delay and Properties of a Haptic Device on Stability Boundary for a Haptic System with a First-Order Hold (일차홀드 방식을 포함한 햅틱 시스템의 안정성 영역에 대한 통신시간지연과 햅틱장치 물성치의 영향 분석)

  • Lee, Kyungno
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.1
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    • pp.572-578
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    • 2017
  • Haptic systems help users feel a realistic sensation when they manipulate virtual objects in the remote virtual environment. However, there are communication time delays that may make the haptic system unstable. This paper shows the relationship between communication time delay, properties of a haptic device, and the stability of the haptic system with the first-order hold method in a simulation. The maximum available stiffness of a virtual spring with the first-order hold method is larger than in the zero-order hold method when there is no time delay. However, when the communication time delay is much larger than the sampling time, the maximum available stiffness to guarantee the stability becomes the same, irrespective of the sample-hold methods. Besides, the maximum available stiffness increases in inverse proportion to the communication time delay and in proportional to the damping coefficient of the haptic device.

CREEP-FATIGUE CRACK GROWTH AND CREEP RUPTURE BEHAVIOR IN TYPE 316 STAINLESS STEELS- EFFECT OF HOLD TIME AND AGING TREATMENT

  • Mi, J.W.;Won, S.J.;Kim, M.J.;Lim, B.S.
    • International Journal of Automotive Technology
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    • v.1 no.2
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    • pp.71-77
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    • 2000
  • High temperature materials in service are subjected to mechanical damage due to operating load and metallurgical damage due to operating temperature. Therefore, when designing or assessing life of high temperature components, both factors must be considered. In this paper, the effect of tensile hold time on high temperature fatigue crack growth and long term prior thermal aging heat treatment on creep rupture behavior were investigated using STS 316L and STS 316 austenitic stainless steels, which are widely used for high temperature components like in automotive exhaust and piping systems. In high temperature fatigue crack growth tests using STS 316L, as tensile hold time increased, crack growth rate decreased in relatively short tensile hold time region. In long term aged specimens, cavity type microcracks have been observed at the interface of grain boundary and coarsened carbide.

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The Effect of Tensile Hold time on the Fatigue Crack Propagation Property and Grain Size on the Creep Behavior in STS 316L. (STS316L의 고온피로균열에 미치는 인장유지시간의 효과 및 결정립크기에 따른 크리프 거동에 관한 연구)

  • 김수영
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • pp.373-378
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    • 2000
  • The heat resistant material, in service, may experience static loading, cyclic loading, or a combination of two. An experimental study of crack growth behavior of STS 316L austenitic stainless steel under fatigue, and creep-fatigue loading conditions were carried out on compact tension specimens at various tensile hold times. In the crack growth experiments under hold times. In the crack growth experiments under hold time loading conditions, tensile hold times were ranged from 5 seconds to 100 seconds and its behavior was characterized using the $\Delta$K parameter. The crack growth rates generally increase with increasing hold times. However in this material, the trend of crack growth rates decreases with increasing hold times for short hold time range relatively. It is attributed to a decline in the cyclic crack growth rate as a result of blunting at the crack tip by creep deformation. The effect of grain size on the creep behavior of STS 316L was investigated. Specimens with grain size of 30, 65 and 125${\mu}{\textrm}{m}$ were prepared through various heat treatments and they were tested under various test conditions. The fracture mode of 316L changed from transgranular to intergranular with increasing grain size.

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Effects of the time delay on the stability of a virtual wall model with a first-order-hold method (시간지연에 의한 일차홀드 방식을 포함하는 가상벽 모델의 안정성 영향 분석)

  • Lee, Kyungno
    • Journal of Institute of Convergence Technology
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    • v.4 no.2
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    • pp.17-21
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    • 2014
  • This paper presents the effects of the time delay on the stability of the haptic system that includes a virtual wall and a first-order-hold method. The model of a haptic system includes a haptic device model with a mass and a damper, a virtual wall model, a first-order-hold model and a time delay model. In this paper, the time delay is considered as the computational time delay that is assumed to be as much as the sampling time. As the time delay increases, the maximal available stiffness of a virtual wall model is reduced reversely. The relation among the time delay and the maximum available stiffness, the mass and the damper of the haptic device are analyzed using the MATLAB simulation.

Analysis for the Stability of a Haptic System with the Computational Time-varying Delay (가변적인 계산시간지연에 의한 햅틱 시스템에서의 안정성 영향 분석)

  • Lee, Kyungno
    • Journal of Institute of Convergence Technology
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    • v.5 no.2
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    • pp.37-42
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    • 2015
  • This paper presents the effects of the computational time-varying delay on the stability of the haptic system that includes a virtual wall and a first-order-hold method. The model of a haptic system includes a haptic device model with a mass and a damper, a virtual wall model, a first-order-hold model and a computational time-varying delay model. In this paper, the maximum of the computational time-varying delay is assumed to be as much as the sampling time. Using the simulation, it is analyzed how the sample-hold methods and the computational time-varying delay affect the maximum available stiffness. As the maximum of computational time-varying delay increases, the maximal available stiffness of a virtual wall model is reduced.