• Title, Summary, Keyword: variation of parameters

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Statistical Performance Estimation of a Multibody System Based on Design Variable Samples (설계변수 표본에 근거한 다물체계 성능의 통계적 예측)

  • Choi, Chan-Kyu;Yoo, Hong-Hee
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.12
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    • pp.1449-1454
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    • 2009
  • The performance variation of a multibody system is affected by a variation of various design variables of the system. And the effects of design variable variations on the performance variation must be considered in design of a multibody system. Accordingly, a variation analysis of a multibody system needs to be conducted in design of a multibody system. For a variation analysis of a performance, population mean and variance which are called statistical parameters of design variables are needed. However, an evaluation of statistical parameters of design variables is impossible in many practical cases. Therefore, an estimation of statistical parameters of the performance based on sample mean and variance which are called statistic of design variables is needed. In this paper, the variation analysis method for a multibody system based on design variable samples was proposed. And, using the proposed method, a variation analysis of the vehicle ride comfort based on sample statistic of design variables was conducted.

Interspecific and Intraspecific Variation in Pollen Grains of Quercus Subgenus Lepidobalanus Endl. in Korea

  • Kim, Sang-Yong;Kim, Kae hwan
    • Plant Resources
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    • v.5 no.1
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    • pp.17-28
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    • 2002
  • Palynological characters such as pollen grain polar axis length (PL), pollen equatorial diameter (ED), colpus length, colpus width, and P/E ratio of six species of Quercus subgenus Lepidobalanus Endl. from Korea were studied. A significant interspecific variation, unequal distances between the species, and various degree of intraspecific variations were found. The taxonomic value of the pollen morphology parameters measured was found to vary according to species. These results suggest a possible relationship between parameters measured and ploidy level of the Quercus species studied.

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The Effect of Machining Parameters on Tool Electrode Edge Wear and Machining Performance in Electric Discharge Machining (EDM)

  • Cogun, Can;Akaslan, S.
    • Journal of Mechanical Science and Technology
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    • v.16 no.1
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    • pp.46-59
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    • 2002
  • The main purpose of this study is to investigate the variation of tool electrode edge wear and machining performance outputs, namely, the machining rate (workpiece removal rate), tool wear rate and the relative wear, with the varying machining parameters (pulse time, discharge current and dielectric flushing pressure) in EDM die sinking. The edge wear profiles obtained are modeled by using the circular arcs, exponential and poller functions. The variation of radii of the circular arcs with machining parameters is given. It is observed that the exponential function models the edge wear profiles of the electrodes, very accurately. The variation of exponential model parameters with machining parameters is presented.

Speaker Variation in Number Production by Males (남성의 숫자음 발성에 나타난 화자변이)

  • Yang, Byung-Gon
    • Speech Sciences
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    • v.8 no.3
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    • pp.93-104
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    • 2001
  • The author analyzed acoustic parameters of ten Korean numbers produced by ten male students using Praat. Variations of f0, F1, F2 and F3 within and between speakers were examined by determining an average and standard deviation of the parameters of each number and by comparing the acoustic values with one another. Results showed that each subject produced the numbers within a certain range of variation across time. Thus, speaker identification can be more certain using dynamic information of the acoustic parameters within each vocalic segment. Also, percent difference of within-subjects' variation to that of between-subjects can be utilized to determine which sounds would be better stimuli for speaker identification. According to the criteria, the number '2' proved the best stimulus while the number '7' was the worst. Future studies will be necessary to explore robust methods of speaker identification under noisy conditions.

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Optimization of Geometric Dimension & Tolerance Parameters of Front Suspension System for Vehicle Pulls Improvement (차량 쏠림 개선을 위한 전륜 현가시스템의 기하공차 최적화)

  • Kim, Yong-Suk;Jang, Dong-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.9
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    • pp.903-912
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    • 2009
  • This study is focused on simulation-based dimensional tolerance optimization process (DTOP) to minimize vehicle pulls by reduction of dimensional variation in front suspension system. In previous studies, the effect of tires and wheel alignment sensitivity have mainly been investigated to eliminate vehicle pulls in nominal design condition without allocating optimal tolerance level for selected components, among various factors regarding vehicle pulls such as vehicle design parameters, vehicle weight balance, tires, and environmental factors. Unfortunately, there are wide variations in the real vehicle, and these have impacted actual vehicle pulls, especially wheel alignment effects from suspension geometry variation has not been considered in the previous studies. In the tolerance design of suspension, tolerance variables with the uncertainty such as parts dimensional variation, assembly process, datum position and direction, and assembly tool tolerance has a great influence on the variation of the suspension dimensional performances. This study introduces total vehicle pull prediction model in considering major key factors for vehicle pull sensitivity. The Monte Carlo-based tolerance analysis model using Taguchi robust method is developed to optimize dimensional tolerance parameters, satisfying on the target variation level.

The Analysis of Groundwater Hydrograph According to the Variation of Hydrologic Physical Characteristics (수문학적 물리적 특성치의 변화에 따른 지하수 수문곡선 분석)

  • 김재한
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.123-137
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    • 1987
  • The groundwater hydrographs due to the recharge of water table aquifer resulting from rainfall are simulated by relating the existing linearized method, which is originally the non-linear equation suggested by Boussinesq, to the basin charcteristics. To thes end, the recharge curve is assumed as the skewed distribution of sine curve, and the parameters contained in the equation are determined from the geomorphologic and soil maps. The whole drainage area is divied in order to consider the spatial variation of parameters. The obtained parameters are tried for several cases with different values given arbitrarily to study the aspects of hydrographs according to their variation. This procedures are applied to the natural basin of Bocheong watershed(area:475.5$\textrm{km}^2$) in Korea. As a result, it is shown that considerable uncertainty is expressed for the results obtained with the given values of parameters. Thus, such uncertainty should be precluded to a certain extent by examining and observing the physical characteristics as much as possible for the determination of groundwater flows.

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A Study on the Influence of Design Parameters on the Automotive Shock Absorber Performance (차량용 충격흡수기의 설계변수에 따른 성능고찰)

  • 이춘태;이진걸
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.6
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    • pp.167-177
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    • 2003
  • In this study, a mathematical nonlinear dynamic model is introduced to predict the damping force of automotive shock absorber. And 11 design parameters were proposed for the sensitivity analysis of damping force. Design parameters consist of 5 piston valve design parameters, 5 body valve design parameters and 1 initial pressure of reservoir chamber air. All of these design parameters are main design parameters of shock absorber in the procedure of shock absorber design. The simulation results of this paper offer qualitative information of damping force variation according to variation of design parameters. Therefore, simulation results of this paper can be usefully use in the design procedure of shock absorber

Digital adaptive control of electro hydraulic velocity control system (전기.유압 속도제어 시스템의 디지탈 적용제어에 관한 연구)

  • 장효환;전윤식
    • 제어로봇시스템학회:학술대회논문집
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    • pp.321-325
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    • 1988
  • The objective of this study is to develop a microcomputer-based adaptive controller for an electro hydraulic velocity control system subjected to the variation of system parameters. The step response performance of the system with the adaptive controller is investigated for the variation of the external load torque, the moment of inertia and the reference inputs, and compared with that obtained by PID controller whose gains are constant. The experimental results show that this proposed model reference adaptive controller is robust to the variation of system parameters and yield much better control performance compared with the conventionel PID controller.

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Performance improvement of a vehicle suspension by sensitivity analysis (민간도해석에 의한 자동차 현가장치의 성능개선에 관한 연구)

  • Song, Chuck-Gee;Park, Ho;Oh, Jae-Eung;Yum, Sung-Ha
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.6
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    • pp.1464-1473
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    • 1990
  • Optimal design parameters are estimated from the sensitivity function and performance index variation. Suspension design modification for performance improvement and basic materials for practical applications are presented. The linear quarter model of a vehicle suspension is analyzed in order to represent the utilities of sensitivity analysis, and sensitivity function is determined in the frequency domain. The change of frequency response function is predicted, which depends on the design parameter variation and the property is verified by computer simulation. As an investigation results of sensitivity function for the vibrational amplitude of sprung mass to road profile input, it is shown that the most sensitive parameters are the suspension damping and the suspension stiffness. In order to identify the effects of these two parameters to the performance of suspension system, the performance index variation according to the changes of parameters is considered and then optimal design parameters are determined. It is verified that the system response is improved noticeably in the both of frequency and time domain after the design modification with the optimal parameters.

A Study on Tire Radial Force Variation and Modal Testing (타이어 상하 힘변동과 모드 시험에 관한 연구)

  • Park, S.K.;Kim, J.K.;Song, S.K.
    • Journal of Power System Engineering
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    • v.2 no.3
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    • pp.55-59
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    • 1998
  • This paper probes into the influence of tire uniformity on tire's modal parameters with the method of experimental modal analysis. Two radial tires of the same kind with different uniformity level are taken to be tested at different exciting points and real modal parameters are abstracted. The differences of their modal parameters are presented. Then tire transfer functions are constructed with experimental modal parameters and ideal modal parameters respectively. It is found that the measured transfer functions of tire of good uniformity are closer to ideal transfer function than that of tire of bad uniformity. The study shows evident interrelation of experimental modal parameters and tire uniformity, and further study should be of great value.

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