• Tribology and Lubricants
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• 제10권4호
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• pp.33-42
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• 1994

An influence of inlet pressure on the performance of sector-shaped pad thrust bearings is investigated theoretically. The optimum conditions of film thickness or the optimum positions of pivot are found through the evaluation of load capacity for all available conditions of film thickness, under the operating conditions which the thermal and pad deformation effects can be neglected. The bearing performance including the inlet pressure effects is obtained for a wide operating ranges that inertia parameter(Re$^{*}$) is up to unity, and for the various cases of pad extent angle (number of pad) and the three cases of the angle between pads. The results show that the inlet pressure has a large influence on the performance of sector-shaped pad thrust bearings. In the design of sector-shaped pad bearings, due to the inlet pressure, the optimum number of pad is varied with the operating speed and the angle between pads, and the optimum position of pivot is located toward the leading edge along with the operating speed increases.

• 제어로봇시스템학회논문지
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• 제7권5호
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• pp.399-406
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• 2001

This paper presents a dynamic modeling and a sliding mode controller for the high-speed/high-accuracy position control system. The selected target system is the wire bonder assembly which is used in the semiconductor assembly process. This system is a reciprocating one around the pivot point that consists of VCM(voice coil motor) as an actuator and transducer horn as a bonding tool. For the modeling elements, the sys-tem is divided into electrical circuit, magnetic circuit and mechanical system. Each system is modeled using the bond graph method and united into the full system. Two major aims are considered in the design of the controller. The first one is that the horn must track the given reference trajectory. The second one is that the controller must be realizable by using the DSP board. Computer simulation and experimental results show that the designed sliding mode controller provides better performance than the PID controller.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 추계학술대회논문집 - 한국공작기계학회
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• pp.83-89
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• 2000

This paper presents a dynamic modeling and a sliding mode controller for the high-speed / high-accuracy position control system. Selected target system is the wire bonder head assembly which is used in semiconductor assembly process. This system is a reciprocating one around the pivot point that consists of VCM(voice coil motor) as a actuator and transducer horn as a bonding tool. For the modeling elements, the system is divided into electrical circuit, magnetic circuit and mechanical system. Each system is modeled by using the bond graph method and united into the full system. Two major aims are considered in the design of the controller. The first one is that the horn must track the given reference trajectory. The second one is that the controller must be realizable by using the DSP board. Computer simulation and experimental results show that the designed sliding mode controller provides better performance than the PID controller.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.111-118
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• 1999

In this paper, linearized dynamic characteristics of parallel line pivoted pad thrust bearing(hereinafter refer to PLP thrust bearing) was analyzed by perturbation method with inlet pressure. Inlet pressure and excitation frequency irfluence dynamic characteristics of PLP thrust bearing at all operating condition, such as angular pivot position, mass of pad. Therefore, the characteristics is have to analyzed with inlet pressure, excitation frequency, mass of pad and thickness of pad. Otherwise, the analysis is able to estimate the characteristics over or under.

• Tribology and Lubricants
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• 제16권4호
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• pp.274-281
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• 2000

In this paper, linearized dynamic characteristics of parallel line pivoted pad thrust bearing (here-inafter refer to PLP thrust bearing) was analyzed by perturbation method with inlet pressure. Inlet pressure and excitation frequency influence dynamic characteristics of PLP thrust bearing at all operating conditions, such as angular pivot position, mass of pad. Therefore, the characteristics have to be analyzed with inlet pressure, excitation frequency, mass of pad and thickness of pad. Otherwise, the analysis may be over or under estimate.

• 대한관절경학회지
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• 제9권2호
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• pp.143-147
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• 2005

목적: 슬개 건을 이용한 전방 십자 인대 재건술 시, 이식 건을 경골 쪽에서 고정할 때 일반적으로 슬관절의 굴곡 각도는 신전 위치에서 시행한다. 저자들은 슬괵 건을 이용한 전방 십자 인대 재건술 시, 이식 건을 고정 할 때 슬관절의 굴곡 각도가 수술 후 슬관절 안정성과 운동 범위에 미치는 영향을 알아보고자 하였다. 대상 및 방법: 2002년 5월부터 2003년 1월까지 슬괵 건을 이용한 전방 십자 인대 재건술 시, Rigidfix system(Mitek Product, Johnson and Johnson, USA)와 intrafix를 이용하여 고정하였다. 전방 십자 인대 재건술을 시행 받은 39명 중 추시 관찰이 되지 않은 2명을 제외한 37명의 환자를 대상으로 하였다. 평균 추시 기간은 14개월(범위: $13{\sim}25$개월) 이었다. 완전 신전 위 또는 20도 굴곡 위의 슬관절 굴곡 각도의 결정은 수술 순서에 따라서 교대로 선택하였다. 내측 반월상 연골의 절제 2예, 내측 반월상 연골의 봉합 2예 외측 반월상 연골의 봉합 1예에서 시행하였다. 임상적 평가는 이학적 검사인 Lachman검사, Pivot shift검사와 재건술 후의 Lysholm점수, IKDC( international knee documentation committee)평가 기준, KT-1000관절 계측 결과를 이용하였다. 결과: 최종 추시 상 수술 후 Lysholm 점수는 93.1점(범위: $65{\sim}98$점), IKDC 평가 기준에 의한 최종 평가 상 정상(A) 26예, 거의 정상(B) 10예, 비정상(C) 1 예이었으며, 심한 비정상은 (D)은 없었다. 최종 추시 상 KT-1000 관절계를 이용한 최대 도수 부하 검사 상 건 측 과의 차이는 평균 2.5 mm 이였다. 술 후 시행한 Lachman 검사상 정상 32예, 1 등급 4예, 2 등급 II 1예 이었고, Pivot shift 검사 상 정상 34예, 1 등급 2예, 2 등급 1예 이었다. KT-1000 관절계를 이용한 최대 도수 부하 검사 상 건 측 과의 차이는 20도 고정을 한 경우는 평균 2.3 mm, 완전 신전 위에서 고정한 경우는 평균 2.7 mm이였다(P<0.05). 수술 후 1년 슬관절의 운동 범위는 20도 굴곡 위에서 고정한 경우에 1례 에서 5도의 굴곡 구축이 있었고, 신전 위에서 고정한 경우는 2례 에서 건측 보다 10도의 굴곡 제한이 있었다. 결론: 자가 슬괵 건을 이용한 전방 십자 재건술 시, 경골 부의 고정 시 슬관절의 굴곡 각도 따른 슬관절의 전방 안정성에 차이는 없었으나, 신전 위에서 고정하는 것이 과도한 이식 건의 장력으로 인한 슬관절 굴곡 구축을 예방하는데 도움이 될 것으로 사료된다.

• 한국정밀공학회지
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• 제32권12호
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• pp.1049-1054
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• 2015

Nowadays, there are many researches involving structural actuators, which have adjustable stiffness; they are also called variable stiffness actuators (VSA). The VSAs can adjust the characteristics of actuators for various functions and human-machine safety. This paper describes the design and analysis of two types of VSAs. To adjust stiffness, the actuators are controlled by a principle of lever ratio mechanism, by changing a pivot position or a spring position in the structure with springs. To make the principle workable, the designs are simplified by using a ball screw system with a motor. Each structure shows different static properties with variable rates of stiffness. We have also shown the experimental verification of the dynamic performance of the two types of VSAs. This research can be applied to various industrial fields, where humans work in conjunction with robots.

• Structural Engineering and Mechanics
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• 제17권5호
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• pp.611-626
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• 2004

On the basis of a structural analysis of radial gate (i.e. Tainter gate), the current paper focuses on weight minimization according to the location of the arms on a radial gate. In spite of its economical significance, there are hardly any previous studies on the optimum design of radial gate. Accordingly, the present study identifies the optimum position of the support point for a radial gate that guarantees the minimum weight satisfying the strength constraint conditions. This study also identifies the optimum position for 2 or 3 radial arms with a convex cylindrical skin plate relative to a given radius of the skin plate curvature, pivot point, water depth, ice pressure, etc. These optimum designs are then compared with previously constructed radial gates. Local genetic and hybrid-type genetic algorithms are used as the optimum tools to reduce the computing time and enhance the accuracy. The results indicate that the weights of the optimized radial gates are appreciably lower than those of previously constructed gates.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.539-539
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• 2000

This paper shows how to implement force reflection for a needle insertion problem. The target is a needle spine biopsy simulator for tumor inspection by needle insertion. Simulated force is calculated from the relationship of volume graphic data and the orientation and Position of the needle, and it is generated using PHANTOM$^{TM}$. To generate realistic force reflection, the directional force of the needle has been generated by tissue model. The other rotational force is generated using a pivot to keep the needle in the initial inserted direction after puncturing the skin. Since the used haptic device has limitation for generating high stiffness and large damping, scale downed model and digital filter are used to stabilize the system.m.

• 한국군사과학기술학회지
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• 제11권4호
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• pp.68-75
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• 2008

This paper proposes a new data hiding method for binary images using the weighting value of pixel-value differencing. The binary cover image is partitioned into non-overlapping sub-blocks and find the most suitable position to embed a secret bit for each sub-block. The proposed method calculates the weighted value for a sub-block to pivot a pixel to be changed. This improves the image quality of the stego-image. The experimental results show that the proposed method achieves a good visual quality and high capacity.