• Title/Summary/Keyword: 주파수가중곡선

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Development of Frequency Weighting Shape for Evaluation of Discomfort due to Vertical Whole-body Shock Vibration (수직방향 전신 충격진동의 불편함 평가를 위한 주파수가중곡선 개발)

  • Ahn, Se-Jin;Jeong, Weui-Bong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.6 s.111
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    • pp.658-664
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    • 2006
  • Shock vibrations are usually experienced in vehicles excited by impulsive input, such as bumps. The frequency weighting functions of the current standards in ISO 2631 and BS 6841 are to help objectively predict the amount of discomfort of stationary vibration. This experimental study was designed to develop frequency weighting shape for shock vibration having various fundamental frequencies from 0.5 to 16Hz. The specks were produced from the response of single. degree-of-freedom model to a half-sine force input. Fifteen subjects used the magnitude estimation method to judge the discomfort of vertical shock vibration generated on the rigid seat mounted on the simulator. The magnitudes of the shocks, expressed in terms of both peak-to-peak value and un-weighted vibration dose values (VDVs) , were correlated with magnitude estimates of the discomfort. The frequency weighting shapes from the correlation were developed and investigated having nonlinearity due to the magnitude of the shock.

Equivalent Discomfort Curve on Idle Vibration Frequency of Passenger Vehicle (승용차량의 정차진동 주파수에 대한 불편함의 등감각곡선)

  • Jeon, Gyeoung-Jin;Lee, Jae-Young;Ahn, Se-Jin;Jeong, Weui-Bong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.6
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    • pp.535-541
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    • 2012
  • The three-down one-up method which is commonly used in the field of psychophysics is employed in this study that is to reveal how much magnitude of vibration makes discomfort in passenger vehicle on idle condition. Thirteen taxi drivers were invited for subject of the experiment where they evaluated the controlled vibrations on rigid seat in terms of idle vibration on passenger vehicle at frequency range from 15 Hz to 40 Hz. As the result, vibration of 100~105 dB is marginal range to make discomfort on passenger seat. Frequency dependency of the discomfort was found at the frequency range, which is the higher frequency the lower discomfort with the same magnitude of vibration. The frequency dependency found here was compared with ISO 2631-1 that is more sensitive at the frequency range.

The Reduction of Pass Band Error in the Order Reduction of the Discrete Time Linear Systems (이산시간 선형 시스템의 차수 감소에 있어서 대역통과 오차 감소)

  • 김정화;정찬수
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.17 no.1
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    • pp.11-19
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    • 1992
  • This paper proposes a reduced order method which reduces passband error by changing controllability and observability gramian based on weighted functions in the linear time invariant system. In the case that the 4-order model is the reduced to 3-order model in the low-pass filter, the QEI in the proposed method is improved to 6.15724 compared to 10.16464 in the balanced realization method and the sensitivity is improved to 5.45962 compared to 7.790568. The frequency property curves show that the proposed method is superior to the balanced realization method.

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Study on Discomfort of Vertical Whole-body Shock Vibration Having Various Magnitudes, Frequencies and Damping (다양한 크기와 주파수 그리고 감쇠를 갖는 상하방향 전신 충격진동에 대한 불편함 연구)

  • Ahn, Se-Jin;Griffin, Michael J.;Yoo, Wan-Suk;Jeong, Weui-Bong
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.2
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    • pp.50-57
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    • 2007
  • Shocks are excited by impulsive forces and cause discomfort in vehicles. Current standards define means of evaluating shocks and predicting their discomfort, but the methods are based on research with a restricted range of shocks. This experimental study was designed to investigate the discomfort of seated subjects exposed to a wide range of vertical shocks. Shocks were produced from the responses of one degree-of-freedom models, with 16 natural frequencies (from 0.5 to 16 Hz) and four damping ratios (0.05 0.1, 0.2 and 0.4), to a hanning-windowed half-sine force inputs. Each type of shock was presented at five vibration dose values in the range $0.35\;ms^{-1.75}$ to $2.89\;ms^{-1.75}$. Fifteen subjects used magnitude estimation method to judge the discomfort of all shocks. The exponent in Stevens' power law, indicating the rate of growth in discomfort with shock magnitude, decreased with increasing fundamental frequency of the shocks. At all magnitudes, the equivalent comfort contours showed greatest sensitivity to shocks having fundamental frequencies in the range 4 to 12.5 Hz. At low magnitudes the variations in discomfort with the shock fundamental frequency were similar to the frequency weighting $W_b$ in BS 6841, but low frequency high magnitudes shocks produced greater discomfort than predicted by this weighting. At some frequencies, for the same unweighted vibration dose value, there were small but significant differences in discomfort caused by shocks having different damping ratios. The rate of increase in discomfort with increasing shock magnitude depends on the fundamental frequency of the shock. In consequence, the frequency-dependence of discomfort produced by vertical shocks depends on shock magnitude. For shocks of low and moderate discomfort, the current methods seem reasonable, but the response to higher magnitude shocks needs further investigation.