• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1824-1827
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• 2003

The sheet metal shearing process is normally used in the precision elements such as semi-conductor components. In precision elements, burrs usually reduce the quality of machined parts and cause interference, jamming and misalignment during assembly procedures and because of their sharpness, they can be safety hazard to personnel. Furthermore, not only burrs are hard to predict and avoid, but also deburring, the process of removing burrs, is time-consuming and costly. In order to get the burr-free parts, therefore, we developed the precise burr measuring system using the laser. The laser burr measuring system consists of the laser probe, the photo detector, the achromatic doublet lens, and the rotary ＆ the X-Y table. In previous reports, we used simple vertical measuring method. But, as we used relatively bigger laser spot diameter and had the limited reflection angle, it was difficult to obtain the precise measuring results. So called, the spot size effect makes the profile of burr measured distorted and the burr height measured smaller. By introducing the novel laser measuring method which employing the achromatic lens system and the tilting mechanism, we could make the spot size smaller and get the appropriate beam direction angle. Through the experiments, the accuracy of the developed system is proved. The burr height measured during the punching process can be used for automatic deburring and in-situ aligning.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.4797-4813
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• 2018

The transform domain communication system (Hereinafter referred to as TDCS) takes on numerous advantages, inclusive of anti-jamming and low probability of detection. Yet its application is confined by the consistent spectrum in the transmitter and receiver, which is not possible in the case of a huge distance exsits between them. In this paper, a TDCS based modified weighted fractional fourier transform (WFRFT) is proposed to solve the problem resulting from spectrum mismatching for TDCS application. The amplitude and phase information are incorporated with the TDCS signals and transmit to the receiver together in the wake of a modified WFRFT. The basic function and the TDCS signals shall be accessible to the receivers in the wake of an inverse WFRFT transform, which make sure that the original information can be demodulated properly. The system's reliability while transmitting signals with different modulation methods and with spectrum mismatching is demonstrated by bit error rate (BER). In the meantime, the constellations of the signals and the BER performances at the eavesdropper demonstrate the proposed system is better secured.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.2
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• pp.99-115
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• 2020

Since GNSS is easily affected by jamming and/or spoofing, alternative navigation systems can be operated as backup system to prepare for outage of GNSS. Alternative navigation systems are being researched over the world, and a multi-radio integrated navigation system using alternative navigation systems such as KNSS, eLoran, Loran-C, DME, VOR has been researched in Korea. Least Square or Kalman filter can be used to estimate navigation parameters in the navigation system. A large number of measurements of the Kalman filter may lead to heavy computational load. The decentralized Kalman filter and the federated Kalman filter were proposed to handle this problem. In this paper, the decentralized Kalman filter and the federated Kalman filter are designed for the multi-radio integrated navigation system and the performance evaluation result are presented. The decentralized Kalman filter and the federated Kalman filter consists of local filters and a master filter. The navigation parameter is estimated by local filters and master filter compensates navigation parameter from the local filters. Characteristics of three Kalman filters for a linear system and nonlinear system are investigated, and the performance evaluation results of the three Kalman filters for multi-radio integrated navigation system are compared.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.555-559
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• 2003

Recently, in accordance with the commercialization of novel radio frequency utilization technologies, the radiated power must be rigorously limited for the purpose of protection of wireless facilities against frequency jamming or interference and for maintaining the quality of communication service. At present, the output power is measured from the conducted power for the domestic measurement criterion but is not a real radiated power and inaccurate. So, it is peformed to survey the more precisely accurate measurement scheme and analyze its criterion and methodology in comparison with foreign one. As a result of surveying and analyzing, it is concluded that the U.S. and E.U. is actually using the measurement method in consideration of terms of the Equivalent Isotropic Radiated Power(EIRP) and Effective Radiated power(ERP). In case of the frequency below 1 GHz, the half wave-length dipole antenna is used to measure the ERP and above 1 GHz the horn antenna as a reference antenna is used to measure the EIRP. Therefore, for the domestic purpose it is also necessary to take EIRP and ERP into consideration as a measurement criterion in order to make an accurate measurement and regulation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.256-265
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• 2018

We herein analyze the survivability of an airborne platform when an active decoy delivers jamming attacks against an active RF seeker system that operates based on the proportional navigation guidance law. In encounter scenarios with various conditions, such as platform maneuvering, the decoy's RF specification, and the seeker's approaching range and angles, the missed distance of the RF seeker is evaluated. By comparing the missed distance with the proximity of the fuze range, the platform's survivability is determined and the survival area of the platform is drawn on several encounter scenarios.

• Journal of Drive and Control
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• v.12 no.4
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• pp.28-34
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• 2015

Because heavy-duty construction vehicles such as excavators are required for good engine-room cooling capacity, a hydraulic gear motor is adopted in the cooling fan drive mechanism to actively control the output speed, instead of adopting the conventional ON/OFF type belt drive. While gear motors are normally limited to 140bars of operating pressure, those for the cooling fan are capable of operating at continuous pressures of up to 220bars. After assembly, all gear motors for high pressure must pass an aging test which is a kind of the wearing process between the gear teeth and motor housing. During the aging process with gradual pressure increments, gear sticking sometimes occurs due to abnormal wear, resulting in defects. This paper focuses on a gear-sticking free aging test controller that is designed together with the knowledge of an experienced operator and the analysis results of experimental data of the gear jamming phenomenon. From the aging experiment, it is demonstrated that the developed controller that can alter the setting pressure of the load pump is effective for stabilizing the abrupt increase in the motor input pressure, thus preventing the hydraulic motor from stopping. This is expected to be helpful for the reduction of defects and increase in productivity.

• Journal of Drive and Control
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• v.11 no.1
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• pp.8-13
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• 2014

Hydraulic servo valves are widely used in various fluid power systems because of their fast response and precision control. In this paper, we studied the effect of metering notch shapes and amount of their openings on the flow characteristics within the spool valve using a computational fluid dynamic (CFD) code, FLUENT. To obtain the results for more realistic operating conditions, viscous heating due to the jet flow and viscosity variation of the hydraulic fluid with temperature were considered. For two types of notch shape, streamlines, oil temperature and viscosity distributions, and variations of flow and friction forces acting on spool were showed. The flow and friction forces affected by the metering notch shapes and their openings, and oil temperature rise near metering notch was significant enough to results in the jamming phenomenon. A thermohydrodynamic (THD) flow analysis adopted in this paper can be used in optimum design of hydraulic servo valves.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.1960-1965
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• 1999

In this paper, we propose a new method of erased concatenated code with RS-convolutional code. In the method, we make use of erasure for undecoded information when we have some errors in RS decoding. For decoding with erasure, the method is processed inner decoding and outer decoding again. After the erasure decoding, if the decoding result is better than the previous one, then we use this result. If not, use the previous one. In this paper, we use concatenated RS(63,31)-convolutional(4.1/2) code. Simulation result is compared with calculation result for performance analysis. According to the result, the proposed method has better performance than the others without erasure such that 2dB when 0.5$\leq\rho\leq$1 and 4dB when $\rho\leq$0.3.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.4
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• pp.63-70
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• 2005

LINK16 is a system which is designed to maximize performance in a particular tactical environment with high levels of jamming. In this paper, transmission performance of synchronization pattern for cipher communication in aerial tactical communication link is presented. Transmission architecture of operating mode (standard DP, P2SP, P2DP, P4mode) in LINK16 network is discussed, and an effect of synchronization pattern, a quality of degraded effect of transmission communication for collision probability between hopping frequencies and fading channel in crypto communication is analyzed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.357-358
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• 2018

The track radar use the range track loop to track the target range. The bandwidth of the radar range tracker can be determined by tradeoff according to signal to noise ratio and the target range. On the other hand, electronic warfare is carried out to prevent the radar from tracking targets by electronic attack. The deception or noise jamming in electronic warfare can be performed to interfere with the range track loop of the radar. In order to efficiently perform electronic warfare, the bandwidth in radar tracking loop is estimated and can be used for electronic attack. To do this, we have studied the method of estimating the bandwidth of radar tracking loop using the variables that can be gathered in electronic warfare.