• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.80-88
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• 2010

A simple computational model for modeling of subsurface crack growth under cyclic contact loading is presented. In this model, it is assumed that the initial fatigue crack will initiate in the region of the maximum equivalent stress at certain depth under the contacting surface. The position and magnitude of the maximum equivalent stress are determined by using the equivalent contact model, which is based on the Hertzian contact conditions with frictional forces. The virtual crack extension method is used for simulation of the fatigue crack growth from the initial crack up to the formation of the surface pit due to contact fatigue. The relationships between the stress intensity factor and crack length are then determined for various combinations of equivalent contact radii and loadings.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.145-148
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• 1990

In this paper, the problem of designing a feedback controller for a robotic manipulator, which is activated by a D.C. motor through a gear train and a flexible shaft or chain, is considered. When the response of the closed loop control system is relatively slow, a satisfactory controller may be designed as a PID controller. As the speed of the control system increases, however, the spring effect of the linkage becomes profound, and as a result, the transient response exhibits a substantial oscillation. To eliminate this oscillation, it is necessary to design the controller based on at least a fourth order system model. This, in turn, requires the feedback of the entire state variables. In practice, however, only the position of the manipulator and the velocity of the motor are readily measurable. The state variable reconstruction method or a state observer cannot be used because of the system nonlinearities such as the Coulomb frictions. In this study, an alternative controller, which is based on delayed feedback of the output variable only, is proposed, and a successful delayed feedback controller is designed and implemented on an actual experimental manipulator.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2501-2513
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• 1994

In this paper, a compact, light-weight, universal, spherical 3-degree-of-freedom, parallel-structured manual controller with high reflecting-force capability is implemented. First, the position analysis, kinematic modeling and analysis, force reflecting transformation, and applied force control schemes for a parallel structured 3 degree-of-freedom spherical system have been described. Then, a brief description of the system integration, its actual implementation hardware, and its preliminary analysis results are presented. The implemented parallel 3 degree-of-freedom spherical module is equipped with high gear-ratio reducers, and the friction due to the reducers is minimized by employing a force control algorithm, which results in a "power steering" effect for enhanced smoothness and transparency (for compactness and reduced weight).d weight).

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.10
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• pp.572-581
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• 2000

When the manipulator consisting of high ratio gear reducers at its joints is used as the slave manipulator in teleoperated systems, its dynamic characteristics is much slower than that of the master manipulator and it is likely to encounter the saturation in the input magnitude. The control input saturation generates an windup phenomenon that the system stability and position tracking performance of the slave manipulator are to be deteriorated. This paper proposes an force reflecting control scheme and its design method which compensates the control input saturation with absolute stability. The proposed scheme is shown to give a stable force reflection while compensating for control input saturation effectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.138-140
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• 2014

The image quality of the color laser printer is highly related with the motion quality of actuators. However, the high precision system requires high production costs in general. The proposed design method in this paper improves image quality without increasing production costs. Using the synchronization method, time gap between exposure and transfer in organic photo conductive (OPC) drum and the period of driving gear revolution are synchronized. The proposed method is verified by computer simulations and experiment, and showed by printed images.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.487-489
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• 1998

To evaluate vehicle performances and driving behavior of a vehicle, it is necessary to acquisit and analyze vehicle data during the vehicle driving, which affect fuel economy and emissions. An in-vehicle data acquisition system, which is called Mode Survey System(MOSS), is designed and developed to analyze the traffic and driving patterns of the vehicle. MOSS is a stand-alone system based on the 68HC11 MCU. MOSS logs various data relating to powertrain and vehicle driving such as vehicle speed, engine RPM, gear position, brake, clutch, fuel consumption, and others. The driving patterns are dependent on the driver's habit and the road and traffic conditions, these driving patterns would be able to make a official driving mode to be used in emission, fuel efficiency, shift survey, catalyst durability, and other tests using the analyzed driving patterns.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.311-312
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• 2012

Blade pitch control system monitors and adjusts angle of the blades and controls rotation speed of blades. This paper shows 2MW pitch system hardware and electric part. Blade pitch system consists of pitch drive, gear box, motor and energy storage. Fieldbus is base on CANopen protocol. Fail-Safe system moves the blades to a safety position in case of any fault condition. The super capacitor energy storage provides emergency back up to the Pitch servo driver during feathering the blades. This paper studied Blade pitch servo driver and a bi-directional DC-DC converter for fail-safe system.

• Journal of the Korean Society of Costume
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• v.50
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• pp.33-50
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• 2000

A comparative and an analysis of the resemblance and the particularity of the women's headgear which has been developed in accordance with each of climate and historical beck ground of the Eastern Slavs: the Russians the Belarusians and the Ukrainians those are deeply influenced by the culture of costume of the Scythians which is considered as the origin of the Koreans culture of costume is presented in this study. A well-known Russian ethnographer D. K. Jelenin classifies the women's head gear of the Eastern Slavs as a platok a chepetch a shapka and a unmarried women's venetch by its structural figure. Those 4 kinds of head gears are the basic head gears of the Eastern Slavic woman. However the characteristics and the features of the head gears of the Eastern Slavic woman However the characteristics and the features of the head gears of each nations show us that they have been developed differently not only by the climatic and the geological influences but also by the influence of their historical background. Furthermore we could realize that the Eastern Slavs had classified a person's social position and a standing in family members by the head gear. The incantational and the religious meanings of the hair styles and the head gears are shown in this paper. For instance they has been considered that a married woman without a hat is a disgrace and it even affects to the harvest. Even they believed that a corn styled Russian woman's hat named "Roga" protects a mother and her baby from the evil spirit. It seems that such a ethnographical culture is caused by their own faith of Russian orthodox and a non-Christian ancient religious culture of those regions.

• Journal of Fisheries and Marine Sciences Education
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• v.6 no.1
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• pp.11-19
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• 1994

The North Pacific midwater trawling which is one of the important fishing methods for Korean fishing industry is working in the Bering Sea and the sea near Kamchaka Peninsula. The catch by Korean midwater trawlers had been recorded about 300 thousands $^{M/_T}$ a year. Six types of midwater trawl net-ordinary midwater trawl net, super-V trawl net, super mesh trawl net, rope trawl net, super plus trawl net and kite trawl net-have been widely used by large trawlers above 1,500gt in size since 1982. Regarding the fishing efficiency, the super plus trawl net and kite trawl net were acknowledged as higher than other nets. Maximum mesh size of super-plus trawl net and kite trawl net ranges about 20m, whereas the length of net about 150m, and high-tech polyethylene is used as the material of rope part. The problems involved in the North Pacific midwater trawl net may be summarized as follows ; (1) The dimension of fishing gear is too big compared with the towing power of trawler. (2) The mesh size of the rope part is too big compared with that of the common netting part. (3) The net is often torn out in the connecting position of the rope part and the netting part. (4) The net is not matched with the trawler and the otter board in many trawlers, so the shape of the trawl gear in the water is instable. (5) The fish school located near head rope, ground rope and side rope in the net recorder is not caught in practice because of the net instability.

• Journal of the Korean Solar Energy Society
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• v.30 no.3
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• pp.98-107
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• 2010

This paper introduces step by step procedures for the design, fabrication and operation of a solar tracking system. The system presented in this study consists of motion controllers, motor drives, step-motors, feedback devices and other accessories to support its functional stability. CdS sensors are used to constantly generate feedback signals to the controller, which assures a high-precision solar tracking even under adverse conditions. It enables instant correction if the system goes off track by strong winds causing gear backlash. A parabolic dish concentrator is mounted on the tracking system whose diameter was 30cm. The solar position data, in terms of azimuth and elevation, sunrise and sunset times were compared with those of the Astronomical Applications Department of the U.S. Naval Observatory. The results presented here clearly demonstrate the high-accuracy of the present system in solar tracking, which are applicable to many existing solar systems.