• 한국소음진동공학회논문집
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• 제23권7호
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• pp.640-644
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• 2013

The present study provides the characteristics of friction noise under reciprocating sliding. The friction contact is generated between the aluminum plate and plastic, which results in friction noise. The experimental results reveal that the friction noise under reciprocating sliding can be produced as the friction coefficient increases. It is also shown that the vibration modes of the pin with dominant deflection in the sliding direction is participated on the friction noise.

• 제어로봇시스템학회논문지
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• 제18권3호
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• pp.275-284
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• 2012

This paper proposes an attitude and direction control of a single wheel balanced robot. A unicycle robot is controlled by two independent control laws: the mobile inverted pendulum control method for pitch axis and the reaction wheel pendulum control method for roll axis. It is assumed that both roll dynamics and pitch dynamics are decoupled. Therefore the roll and pitch dynamics are obtained independently considering the interaction as disturbances to each other. Each control law is implemented by a controller separately. The unicycle robot has two DC motors to drive the disk for roll and to drive the wheel for pitch. Since there is no force to change the yaw direction, the present paper proposes a method for changing the yaw direction. The angle data are obtained by a fusion of a gyro sensor and an accelerometer. Experimental results show the performance of the controller and verify the effectiveness of the proposed control algorithm.

• 한국해안해양공학회지
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• 제16권1호
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• pp.27-38
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• 2004

본 연구에서는 Shimosako and Takashi(1999)가 직립방파제 케이슨의 기대활동량을 계산하기 위해 개발한 신뢰성 설계법을 방향 불규칙파의 방향 분산, 심해 설계주파향이 해안선에 직각 방향과 이루는 각도, 심해 주파향의 설계치에 대한 변동 등과 같은 파향의 변동성을 고려할 수 있도록 확장하였다. 심해로부터 방파제 설계 위치까지의 파랑변형을 계산하기 위하여 Shimosako and Takahashi는 평행한 등심선을 갖는 직선 해안에 직각으로 입사하는 일방향 불규칙파를 가정하여 Goda(1975)가 개발한 모형을 사용하였다. 본 연구에서는 방향 불규칙파의 변형을 계산하기 위하여 Kweon et al.(1997)이 개발한 모형을 사용하였다. 파랑의 방향분산 및 심해 주파향의 변동에 의한 영향은 별로 크지 않은 반면에, 심해 설계주파향이 해안선에 직각 방향과 이루는 각도의 영향은 상대적으로 커서, 이 각도가 증가함에 따라 기대활동량이 감소하는 경향을 보였다. 특히 우리나라 동해안 일부 지역의 현장 자료를 이용한 경우 파향의 변동성을 고려했을 때의 기대활동량이 이를 고려하지 않았을 때에 비해 약 1/3수준으로 감소하였다. 파랑변형 계산을 위하여 Goda 모형을 사용하는 경우 무시되는 굴절의 영향을 보정하기 위하여 계산된 유의파고를 일률적으로 6% 감소시키는 것은 심해 설계주파향이 약 20$^{\circ}$인 경우에 적합한 값이며, 심해 설계주파향이 보다 작은 경우에는 6%보다 작은 값을, 보다 큰 경우에는 6%보다 큰 값을 사용해야 한다. 케이슨의 기대활동량을 30cm로 설계할 경우 수심이 약 25 m 이하의 지역에서는 파향의 변동성을 고려하지 않더라도 기존의 결정론적 설계보다 최대 약 30% 정도까지 케이슨의 폭을 줄일 수 있다. 동해안 일부 지역의 현장 자료를 사용하여 파향의 변동성을 고려할 경우에는 이를 고려하지 않은 경우보다 최대 약 10% 정도까지 케이슨의 소요 폭이 감소하며, 고려한 전 수심 구간(10∼30 m)에서 결정론적 설계보다 작은 케이슨 폭이 요구된다.

• 한국지반공학회지:지반
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• 제8권3호
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• pp.13-22
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• 1992

Model pile tests using calibration chamber are performed in !his paper in order to clarify the effect of the fundamental differences between the newly developed SPLT(Simple Pile Loading Test)and the conventional pile loading test on the pile bearing capacity. They are : (1) the direction of the applied load to mobilize the skin friction ; and (2) the use of reduced sifted sliding core. The conclusions obtained from the model pile tests are as follows : (1) The skin friction in tension loading is found to be somewhat smaller than that in compression loading. The average ration is 0.73 with the coefficient of variation (COV) of 0.18. (2) The ratio of the tip resistance rosin연 the reduced sized sliding core to that using the whole shoe shows wide scattering ; its average is 0.99 and the COV is 0.28. The aver - age of 0.99 means that there is no considerable difference in the tip resistance whether the reduced sized sliding core or the whole shoe is used, on condition that penetration depth ratio is larger than 4 : if the boundary effect of the chamber test is considered, the resistance of the whole shoe might be even larger.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.297-302
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• 1999

Finite element analysis is peformed about the crack propagation in half-space due to sliding contact. The analysis is based on linear elastic fracture mechanics and stress intensity factor concept. The crack location is fixed and the friction coefficient between asperity and half-space is varied to analyze the effect of surface friction on stress Intensity factor for horizontal crack. The crack propagation direction is predicted based on the maximum range of shear and tensile stress intensity factor.

• 한국전기전자재료학회논문지
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• 제14권7호
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• pp.578-583
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• 2001

The bushing for high voltage and large and power should endure weight of itself and force of pushing from contact with circuit breaker. Like this, epoxy mold bushing has to be strong without fault. However, the external circumstances and internal factors was caused by partial discharge, flashover and dielectric breakdown. Therefore, to remove external factor of defect and to prevent the internal cracks and cavity generated from the contraction on interface of Cu-Epoxy, we should form semi-conductive layer on Cu bar by carbon. Then, the PD properties and the insulation qualities of epoxy mold type bushing was able to improved by roles of cushions for the direction of diameter and by effects fo natural sliding like as separated from conductor for the direction of length. So, in this work, we could prove the method of semi-conductive layer in making the long conductor.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.180-184
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• 2004

The tribological behavior of carbon epoxy composites whose surfaces have many small grooves of $100\mu m$ width was experimentally investigated with respect to the sliding direction against groove orientation, surface pressure (P) and velocity (V). The wear mechanism of the composites was observed to calculate the wear volume with respect to the friction coefficient using scanning electron microscopic (SEM). Experimental results show that the abrasive wear is dominant wear mechanism for the grooved composite surface and the friction and wear are greatly reduced when the sliding direction is parallel to the axis of groove because abrasive particles are removed through the grooves effectively.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.947-948
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• 2006

This paper proposes a robust posture stabilization control method for wheeled mobile robots. To solve the robust posture stabilization, we introduce reference generation mode, reference tracking mode, and reference regulation mode. In reference generation mode, a kinematic time-invariant controller is used to generate the reference trajectory which starts from the initial posture of the actual robot to the desired posture. In reference tracking mode, a sliding mode position controller is employed in such a way that the actual robot can follow the reference trajectory in the desired forward or backward moving direction, even in the presence of the disturbances in the dynamics. In reference regulation mode, a sliding mode heading direction controller is used such that the actual robot can maintain the desired posture against the disturbances. In this way, robust posture stabilization can be achieved at almost all global regions.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.220-224
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• 1999

Sliding wear test was employed to determine the effect of whisker content and orientation on the firiction and wear behavior of SiC whisker reinforced alumina. Composites containing unidirectionally oriented whiskers were prepared by a modified tape casting followed by lamination, binder removal and hot pressing in order to align the whiskers in the tape casting direction. Wear coefficients on three directions were measured; parallel and normal to the tape casting direction on the tape casting surface and normal to lamination direction on surfnce normal to the tape casting direction. In the effect of whisker orientation, the highest wear rate was obtained in the direction parallel tape casting direction and the lowest in the direction normal to lamination direction at all temperatures. Silicon oxide layer amoothing the surface was detected by energy dispersive X-ray analysis on the worn surface.

• Journal of Mechanical Science and Technology
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• 제16권11호
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• pp.1379-1394
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• 2002

In case of a single input single output (SISO) system with a nonlinear term, a signal compression method is useful to identify a system because the equivalent impulse response of linear part from the system can be extracted by the method. However even though the signal compression method is useful to estimate uncertain parameters of the system, the method cannot be directly applied to a unique system with hysteresis characteristics because it cannot estimate all of the two different dynamic properties according to its motion direction. This paper proposes a signal compression method with a pre-processor to identify a unique system with two different dynamics according to its motion direction. The pre-processor plays a role of separating expansion and retraction properties from the system with hysteresis characteristics. For evaluating performance of the proposed approach, a simulation to estimate the assumed unknown parameters for an arbitrary known model is carried out. A motion platform with several single-rod cylinders is a representative unique system with two different dynamics, because each single-rod cylinder has expansion and retraction dynamic properties according to its motion direction. The nominal constant parameters of the motion platform are experimentally identified by using the proposed method. As its application, the identified parameters are applied to a design of a sliding mode controller for the simulator.