• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1176-1181
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• 1995

Microdrilling is one of the most difficult operations because of the poor chip discharge and the weakness of tool. This study is concerned about the development of a microdrilling monitoring system that is useful for minimizing the tool breakage and enhancing the machinability in the air spindle based microdrilling. The system is composed of a drilling state detection unit and an adaptive step-feed control unit that controls the micro-stepping motor driven spindle axis. Drilling states such as overload, tood breakage are recognized by the change of the air spindle speed which is measured via the reflective photo sensor. Based on the monitoring results, the adaptive step-feed control algorithm adjusts the step increment to keep the decrease of spindle speed within a specified range. The results of evaluation tests have shown that the developed system is very effective to prevent the breakage of microdrill and improves the productivity in comparison with the conventional microdrilling.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.64-68
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• 1995

미세드릴가공은 최근의 공업제품의 소형 경량화 추세로 인해 수요가 급증하고 있으나 가공시에 있어서 많은 난 점이 존재 하기 때문에 강도 높은 가공기와 숙련된 가공전문가를 필요로 한다. 본 연구에서는 미세드릴가공을 수행하기 위해 우선 절삭상태 검출방법으로써 실용적이고 가공상황에 간섭을 일으키지 않는 주축용 모터의 전류 값을 이용하며 제어기 설계를 위해 퍼지추론과 유전알고리즘 이론을 도입한다. 이러한 지능형 가공방법을 미세 드릴가공에 구현하기 위해서 오프라인으로 안정한 가공조건을 초기화한 다음 퍼지제어기를 이용하여 일정한 절삭력을 유지할 수 있도록 실시간으로 이송속도를 제어하며 가공상황 변동에 따른 적절한 퍼지규칙을 자기 동조하는 최적화 알고리즘을 제안한 후 실제가공을 통하여 미세드릴가공의 특성과 제어기의 성능을 평가한다.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.2
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• pp.267-275
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• 2012

In this study, normal wind load and blast wind load are modeled mathematical. And the periodical torque and bending moments transmitted to the main shaft of wind turbine are investigated. A normal wind model assumed, of which the wind velocity is increased according to the height from ground. The average values and the harmonic terms of the transmitted moments are studied on the wind direction of range $-45^{\circ}{\sim}45^{\circ}$ and the bending moment characteristics are examined, which is regarded as the main source of the misalignment of gear train. In normal wind load case, excitation frequency is 3X (X : Rotor speed). When the wind direction is $+22.5^{\circ}$, the horizontal axis of bending moment occur the 50% of main torque. This result leads to edge contact of gear teeth by shaft elastic deformation. In blast wind load case, excitation frequency are 3X,6X,9X. Additional, in the (+) direction of wind load, relative harmonic percentage is increase.