• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.125-128
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• 1994

One of the abnormal motions of the projectile in the coil gun is spinning. It is found that the spinning force is closely related with air gap distance. Modified and detail analysis for the spinning is suggested in this paper. Two reasons for spinning force and Lorentz force affecting on the spinning are introduced. Nutation, which is a result of spinning, is explained there after.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.7
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• pp.109-116
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• 2010

The magnet wheel which generates on its interfacing conductive part a repulsive force and a traction torque by rotation of permanent magnets is used to manipulate the conductive plate without mechanical contact. Here, the air-gap magnetic field of the magnet wheel is shielded partially to convert the traction torque into a linear thrust force. Although a magnitude of the thrust force is constant under the fixed open region, we can change the direction of force by varying a position of the shield sheet. So, the spatial position of conductive plate is controlled by not the force magnitude from each magnet wheel but the open position of shield sheet. This paper discusses non-contact conveyance system of the conductive plate using electromagnetic forces from multiple magnet wheels.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.9
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• pp.454-461
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• 2001

Acoustic noise and vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and electromagnetic origins through the motor air-gap. When a relative misalignment of rotor in the air-gap center exists on the assemblage, it is considered to influence the motor system characteristics. In this paper, the back electro motive force(BEMF) is analyzed by Finite Element Method(FEM) and verified by experiments for the SPM and IPM type motors. For magnetic field analysis, a FEM is used to account for the magnetic saturation. Using these results, the FEM is made to determine the appropriate electromagnetic field analysis in BLDC motors with rotor eccentricity ratio. A radial magnetic imbalance force of BLDC motor with rotor eccentricity is analyzed. Results demonstrate that the imbalance force is increased according to the degree of misalignment. An IPM motor, mostly chosen to realize high-speed operation, shows a worse effect on magnetic unbalanced forces and dynamic responses compared with SPM motor due to magnetic saturation when the rotor eccentricity exists.

• Journal of Advanced Navigation Technology
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• v.20 no.3
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• pp.203-209
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• 2016

Among the various fields in the communications, navigation, and surveillance/air traffic management (CNS/ATM) scheme, the surveillance field, which includes an automatic dependent surveillance - broadcast (ADS-B) system and a multilateration (MLAT) system, is implemented using satellite and digital communications technology. These systems provide better performance than radar, but still incur position error. To reduce the error, we propose an efficient information fusion method called the reweighted convex combination method for ADS-B and MLAT systems. The reweighted convex combination method improves aircraft tracking performance compared to the original convex combination method by readjusting the weights given to these systems. In this paper, we prove that the reweighted convex combination method always provides better performance than the original convex combination method. Performance from the fusion of ADS-B and MLAT improves an average of 51.51% when compared to the original data.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.1
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• pp.10-19
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• 2022

Recently, the Defense Advanced Research Projects Agency(DARPA) in the United States is studying a new concept of war called Mosaic Warfare, and MUM-T(Manned-Unmanned Teaming) through the division of missions between expensive manned and inexpensive unmanned aircraft is at the center. This study began with the aim of deriving the priority of autonomous functions according to the role of unmanned aerial vehicles in the present and present collaboration that is emerging along with the concept of mosaic warfare. The autonomous function of unmanned aerial vehicles between the presence and absence collaboration may vary in priority depending on the tactical operation of unmanned aerial vehicles, such as air-to-air, air-to-ground, and surveillance and reconnaissance. In this paper, ACE (Air Combat Evaluation), Skyborg, and Longshot, which are recently studied by DARPA, derive the priority of autonomous functions according to air-to-air collaboration, and use AHP analysis. The results of this study are meaningful in that it is possible to recognize the priorities of autonomous functions necessary for unmanned aircraft in order to develop unmanned aerial vehicles according to the priority of autonomous functions and to construct a roadmap for technology implementation. Furthermore, it is believed that the mass production and utilization of unmanned air vehicles will increase if one unmanned air vehicle platform with only essential functions necessary for air-to-air, air-to-air, and surveillance is developed and autonomous functions are expanded in the form of modules according to the tactical operation concept.

• Proceedings of the ESK Conference
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• 1995.04a
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• pp.117-123
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• 1995

The anthropometric data are one of the most important factors to be considered for an aircraft systems design. Rescently, co-development program between the countries is considered frequently as a type of aircraft acquisition in aircraft industry. Consequently, the comparision of anthropometric data beteen the countries for the cockpit design is essential. In this paper, we simpoly compares anthropometric data of Korean air force pilots with those of Japan air force pilots. Although further collection of data are reauired, the result shows a few differences and it shows the possibility of future co-development program between the countries.

• Safety and Health at Work
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• v.12 no.2
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• pp.282-283
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• 2021

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1149-1156
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• 2008

The principle of self clamping friction clutch is presented in this paper and the transmitted torque capacity is also calculated. In order to enlarge the friction force, a part of rotating force of driving side is converted to normal force of friction materials by clamping arm. The increased normal force of friction materials assures the large friction force and the transmitted torque capacity of clutch becomes large. The self clamping friction clutch is adopted in the tube type air pressure clutch and the condition of stability is investigated. It is proven that the inclined angle of clamping arm and the friction factor of friction materials are the essential elements in stability and torque capacity of self clamping friction clutch. The transmitted torque capacity of self clamping friction clutch is compared with air pressure clutch. The normal force of friction lining is magnified by 1/(1-k) and the transmitted torque capacity is also magnified with same proportion comparing with air pressure clutch. The larger the friction factor of friction lining, the larger the magnification factor. The longer the clamping arm, the smaller the magnification factor. It must be also noted that the value of k=${\mu}Y/X$ is the criterion of stability. If the value of k=${\mu}Y/X$ is greater than or equal to 1, the self clamping friction clutch is unstable and it can not be used as clutch.

• Tribology and Lubricants
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• v.33 no.6
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• pp.309-314
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• 2017

This paper presents a theoretical investigation of the dynamic characteristics of externally pressurized air pad bearings with closed loop grooves. These grooves are made on the surface of bearings to reduce the number of supply holes so that manufacturing costs can be reduced. The semi-implicit method is applied to calculate the time varying pressure profile on the air bearing surface owing to the advantages of numerical stability and fast time tracing characteristics. The static pressure of the groove bearings is much higher than that without grooves, so the groove bearings can provide high load carrying capacity. The equation of motion considering vertical motion and tilting motion are also solved using the Runge-Kutta 4th order method. By combining the semi-implicit method and the Runge-Kutta method, fast calculations of the dynamic behavior of the air bearing can be achieved. The variations of bearing reaction force, air film reaction moment, height, and tilting angle are investigated for the step force input, which is 20% higher than the bearing reaction, when the nominal clearance is 6 mm. The effect of the groove width and the groove depth are investigated by calculating the dynamic behavior. The possibility of the air hammering with the depth of the groove is found and discussed.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.78-80
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• 2005

Haptic interface apparatus is the device which can offer users virtual reality not only by visualization of virtual space but also by force or tactile feedback. In this paper, we designed and fabricated a 2D haptic interface device that can be used for various purposes, and implemented a virtual air-hockey system that users can easily find in game rooms. By suitable modeling and haptic rendering, users can feel the impact and the reaction force with his/her hand holding the handle through 2D haptic interface device when he/she hit an air-hockey puck with the handle. Through the trial demonstration. we observed the reasonable effect of direction and speed of a ball like doing in reality.