• Proceedings of the KIEE Conference
• /
• 2005.07d
• /
• pp.3040-3042
• /
• 2005

During the last several years, interest in broad-band power line communications (PLC) has been grown over medium voltage(MV) power distribution lines as well as low voltage lines. This paper introduces a medium voltage PLC test field that is set up in the suburbs of Euiwang city in Korea. This test field could be used not only for the measurement of communication channel environment but also for internet service. This paper shows the configuration of medium voltage test field with network devices like MV signal coupler and the results of channel environment like noise and impulse response. It also shows the service performance of PLC access network through network management system.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.1020-1025
• /
• 2007

The reciprocating type hydrogen compressor is for high pressure and volume. However this type compressor makes pulsation caused by mechanical characteristic. This type compressor also makes noise and vibration that cause negative effect to machine and working condition. Therefore, diagnosis and countermeasure are needed to decrease vibration for safety on hydrogen compressor. therefore in this paper, the numerical analysis and vibration measurement is conducted in order to investigate vibration characteristic and to evaluation vibration condition, Respectively

• Journal of KSNVE
• /
• v.6 no.5
• /
• pp.567-574
• /
• 1996

This paper concerns an articulated space robot with flexible links. The equations of its motion are derived by means of the Lagrangian mechanics. Assuming that magnitude of elastic motions are relatively small, the perturbation approach is taken to separate the original equations of motion into linear and nonlinear equations. Th effect the desired payload motion, open loop control inputs are first determined based on the nonlinear equations. One the other hand, in order to reduce the positional errors during the maneuver, vibration suppression is actively done with a feedforward control for disturbance cancellation to some extent. Additionally, for performance robustness against residual disturbance, an LQ control modified to have a prescribed degree of stability is applied based on the linear equations. Measurement equations are formulated to be used for the maximum likelihood estimator to reconstruct states from the original robot equations of motion. Finally, numerical simulations show effectiveness of the proposed control design scheme.

• Journal of KSNVE
• /
• v.11 no.2
• /
• pp.354-364
• /
• 2001

The vibration induced by high speed train running on rail is dealt with as an environmental problem. The train induced vibration is characterized by moving loads at specific frequencies and soil conditions. In fact, it is predicted that the vibration sources are involved the wheel distance, number of cars, speed of operation, drift of rails, structural born vibration, etc. In this paper the characteristics of transferring vibration induced by the high-speed train in operation is discussed. Field measurements was conducted at region from Chungnam Yungj So-jung-myan to Chungbuk Chungwon hyun-do-myun. In the near future. these data will be used as the fundamental data for establishment of the countermeasure for vibrational reduction of high speed train using the results of the field measurements and quantitative prediction of the vibration level

• Journal of KSNVE
• /
• v.5 no.3
• /
• pp.403-411
• /
• 1995

Square beam type piezoelectric vibrating gyro is developed for the measurement of angular velocity, which is compact, small in size and mass- producible. It features that three pieces of piezoelectric ceramics and bonded onto one face of equilateral square bar type gyro head. Two of them are used as sentuators which drive the gyro head and measure Coriolis force. The third piece is used for the feedback signal in order to resonate the gyro head and measure Coriolis force. The third piece is used for the feedback signal in order to resonate the gyro head with its fundamental natural frequency. Matching two fundamental natural frequencies in the gyro head with its driving frequency is found critical in the design of vibration gyro. Calibration results show that the vibrating gyro developed has the dynamic characteristics of first-order system within the frequency range of interest, which can be easily compensated by a lead compensator.

• Journal of KSNVE
• /
• v.1 no.2
• /
• pp.129-140
• /
• 1991

The boiler feed pump located at a power plant has been experienced a severe vibration since the plant began to service in early 1980. The research is focused on the field measurement and implementation of simple signal processing techniques in order to provide realistic and effective solution which could be implemented into the plant. Based on the root cause analysis for the trouble-making pump system, the driving part gear in the fluid coupling system is identified as a potential source. The followed verification test confirms the analytical result. The test result shows that vibration reduction obtained after the gear replacement reaches up 15.8 dB, which is 1/6 times of the vibration level compared to that of the troble-making pump. The measured vibration level of the pump satisfies the manufacture criteria and guarantees the smoothed operation.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.1 no.1
• /
• pp.41-49
• /
• 1993

Piston slap is one of the major sources of noise in a 4-cycle diesel engine. Piston slap is not only one of major source mounted near the top and bottom of the piston thrust and antithrust skirts. Effects of engine speed, load and coolant temperature on piston motion were investigated. The measured piston motion showed 6 slapes per cycle resulting from the change of side force. Major piston slap timing was retarded as engine speeds became higher. The increase of engine load made large piston transverse movement toward thrust side of cylinder block. Piston transverse movement was due to reduced piston-liner clearance at higher coolant temperature.

• Journal of the korean Society of Automotive Engineers
• /
• v.14 no.5
• /
• pp.117-127
• /
• 1992

In this work, the possibility to diagnose valve lashes of an automotive diesel engine via cylinder head vibration/noise analysis is studied. First of all the measurement signals and conditions are selected after considering which signals and conditions are most suitable to diagonse valve lashes. Both accelerometer and microphone are used to measure cylinder head accelerations and acoustic pressure due to valve impact on cylinder head. The signals are measured in both cranking and engine firing conditions. Finally, it was found that acceleration signal obtained in engine operating condition is the most reliable signal to diagnose the valve lash condition. The valve closing angle and the peak acceleration due to valve close are chosen to analyze the valve lash condition. The measured cylinder head acceleration signals are statistically tested to derive information which are useful to judge the valve lash. In conclusion, it was found that the developed technique can be one of feasible methods to diagnose the valve conditions while the engine is in operation.

• Journal of Astronomy and Space Sciences
• /
• v.28 no.3
• /
• pp.193-201
• /
• 2011

A strategy for geostationary orbit (or geostationary earth orbit [GEO]) surveillance based on optical angular observations is presented in this study. For the dynamic model, precise analytical orbit model developed by Lee et al. (1997) is used to improve computation performance and the unscented Kalman filer (UKF) is applied as a real-time filtering method. The UKF is known to perform well under highly nonlinear conditions such as surveillance in this study. The strategy that combines the analytical orbit propagation model and the UKF is tested for various conditions like different level of initial error and different level of measurement noise. The dependencies on observation interval and number of ground station are also tested. The test results shows that the GEO orbit determination based on the UKF and the analytical orbit model can be applied to GEO orbit tracking and surveillance effectively.

• International Journal of Aeronautical and Space Sciences
• /
• v.12 no.1
• /
• pp.37-42
• /
• 2011

An extended scalar adaptive filter for guided missiles using a global positioning system receiver is presented. A conventional scalar adaptive filter is adequate filter for eliminating sudden abnormal jumping measurements. However, if missile or vehicle velocities have variation, the conventional filter cannot eliminate abnormal measurements. The proposed filter utilizes an acceleration term, which is an improvement not used in previous conventional scalar adaptive filters. The proposed filter continuously estimates noise measurement variance, velocity error variance and acceleration error variance. For estimating the three variances, an innovation method was used in combination with the least square method for the three variances. Results from the simulations indicated that the proposed filter exhibited better position accuracy than the conventional scalar adaptive filter.