• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.41-45
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• 1997

To design a control system, it is a elementary point that the stability of the system should be guaranteed. Also, the phase of the system plays an important role for its frequence performance. In this paper, we present two stability criterion of repetitive control system with phase-lead and lag compensator. First, the stability criterion for the servo control system with phase-lead and lag compensator is shown by using small-gain theorem. Second, for the repetitive control system with the compensator, the stability criterion, also, is determined by using small-gain theorem. Two stability criterions show the same results that the stability depends on a coefficient of the phase-lead and lag compensator under some condition in servo control system and repetitive control system.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.137-143
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• 2002

This paper presents the In-process compensation to control cutter runout and improve the machined surface quality. Cutter runout compensation system consists of the micro-positioning servo system with piezoelectric actuator which is embeded in the sliding table to manipulate radial depth of cut in real-time. Cutting force feedback control was proposed in the angle domain based upon repetitive learning control strategy to eliminate chip load variation in end milling process. Micro-positioning control due to adaptive actuation force response improves the machined surface quality by compensation runout effect induced cutting force variation. This result will provide lots of information to build-up the preciswion machining technology.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.170-176
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• 2005

Analysis of structures which are composed of numerous repeated unit structures can be simplified by using homogenized properties. If the unit structure is repeated in one direction, the whole structure may be regarded as a beam. Once the effective stiffness is obtained from the analysis of the unit structure in a proper way, the effort for the detail modeling of the global structure is not required, and the real structure can be replaced simply with a beam. This study proposes a kinematical periodicity constraint to be imposed on the FE model of the unit structure, which improves the accuracy of the effective stiffness. The method is employed to a one dimensionally arrayed 3D structure containing periodically repeated un-symmetric holes. It is demonstrated that the deformation behavior of the homogenized beam agrees well with that of the real structure.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.1
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• pp.143-152
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• 1996

The vibratory bowl feeder is the most versatile of all hopper feeding devices for small engineering parts, and the typical nonlinear dynamic system experiencing repeated impacts with friction. We model and analyze the dynamic behavior of a single part on the vibrating track of the bowl feeder. While the previous studies are restricted to the sliding regime, we focus our analysis on the hopping regime where the high conveying rate is available. We present the numerical analysis results for conveying rate and frictional impact process both in periodic and chaotic regimes. We examined the dynamic effects from the variation of several physical parameters, and presented the important features for the design of the vibratory bowl feeder. This research holds much potential for leverage over design problems of wide range of mechanisms and tools with repeated collisions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.38-44
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• 1995

We made a counter to measure the output of motor encoders for the motion error analysis of a CNC machining center, and have measured the dynamic characteristics and the position errors experimentally. Especially, we measured the radius errors for different feedrates and different radii when the CNC machining center performed a circular interpolation. We have also used an iterative learning method to reduce the radius errors and stick motion errors generated by the CNC machining center performing a circular interpolation. The results show that the proposed learning scheme can reduce the radius error and stick motion error significantly. The reduction of errors becomes more pronounced for higher feedrate and smaller radius.

• Proceedings of the KIEE Conference
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• summer
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• pp.890-892
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• 2004

단락발전기를 이용하여 대전류 단락시험을 실시하는 시험 설비중 단락전류 투입시 정밀한 투입 위상각 제어와 주접점 접촉시 바운싱이 없는 투입개폐기 특성이 요구된다. 이러한 특성을 만족시키기 위하여 공압식, 모터식, 유압식등 여러 종류의 투입개폐기가 사용되고 있으며 Actuator와 주 접점 형상설계 및 조립기술에 의한 바운싱이 없는 제품 제작이 중요하다. 본 논문에서는 정격전압 24 kV 단락전류 47 kA, 통전시간 0.5 s의 투입용량과 연속 반복 투입시 $\pm0.1$ ms의 오차특성을 가진 정밀급 유압식 투입개폐기의 동작특성과 핵심부품 조사 및 바운싱 제거를 위한 대책실시와 반복시험을 통하여 투입개폐기 특성에 대한 연구를 목적으로 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.1
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• pp.79-88
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• 2014

Enhancing the working speed and positional accuracy of high-speed press machines is essential for improving the parts accuracy and productivity. However it is known that the positional accuracy decreases and the risk of parts failure increases as the working speed of press machine increases. Therefore predicting such problems during the stage of press structure design is necessary for precise design of high-speed press machines. In the present investigation, the dynamic-elastic deformation of press drive module parts with eccentric masses was examined by finite element analysis and experiment. Then the positional accuracy and parts failure of high-speed press machines was evaluated.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.112-118
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• 2000

A modified repetitive control is formulated and analyzed in the discrete-time domain. Sufficient conditions for the stability of a class of repetitive controllers are given by means of the regeneration spectrum method. When a periodic signal input is drived into the two-mass-spring plant, the performance of the proposed controller which comprises a low-pass filter and two feed-forward compensators, turns out highly accurate by comparing the tracking result from the conventional LQ controller.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.928-934
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• 1998

This paper describes a fully digitalized driver for BLDC motors which is realized by a single chip microprocessor. The speed change can be done by using the signal obtained from the position detecting sensor and adjusting the pulse width at the input channel of power module. In order to establish a speed control system a repetitive control method is adopted to track a periodic refer-ence change in the BLDC motor system. The experimental results show accurate reference track-ing performance under the given periodic reference in the repetitive controller design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.37-41
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• 2002

Thermal characteristics of hydrostatic guideway is largely depended on the temperature of supplied oil. For improving the positioning accuracy of hydrostatic guideway, relationship between setting temperature of oil cooler and thermal characteristics is analyzed, and influence of thermal characteristics on positioning accuracy is also analyzed experimental1y in this paper. Laser scale which has 0.01 $\mu\textrm{m}$ of resolution is used as feed-back unit. From the experimental results, it is confirmed that positioning error and repeatability is minimize upto 0.21 $\mu\textrm{m}$ and 0.18 $\mu\textrm{m}$ when the temperature of supplied oil is setting equal to temperature of atmosphere, and also confirmed that thermal deformation, which occurs by the temperature deviation between table and rail or scale supporter, works as limit of repeatability in long time operation.