• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.27-31
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• 2003

Underwater acoustic navigation systems are classified into three systems: ultra-short baseline (USBL), short baseline (SBL), and long baseline (LBL). Because the USBL system estimates the angle of a submersible, the estimation error becomes large if the submersible is far from the USBL transducer array mounted under a support vessel. SBL and LBL systems estimate submersible's location more accurately because they have wider distribution of measuring sensors. Especially LBL systems are widely used as a navigation system for deep ocean applications. Although it is most accurate system it still has estimation errors because of noise, measurement error, refraction and multi-path of acoustic signal, or wrong information of the distributed transponders. In this paper the estimation error of the LBL system are analyzed from a point of sensitivity. It is assumed that the error exists only in the distance between a submersible and the transponders. For this purpose sensitivity of the estimated position with respect to relative distances between them is analyzed. The result says that estimation error is small if the submersible is close to transponders but not near the ocean bottom.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.2
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• pp.110-118
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• 1997

This paper describes the dissipation factor measuring techniques of insulating oil on operating pole transformers by using digital signal processor. After applying voltage to the condenser which is in¬stalled in a transformer, acquiring source voltage and current of condenser and using cross-correla¬tion techniques, we can check the dissipation factor of insulating oil. To improve measuring accuracy and the speed of process, we use hardware such as TMS320C31 DSP board and software such as cross -correlation techniques. We simulated the measuring accuracy and the degree of the noise effect of this new measuring techniques by using computer simulation, and compared the simplified measuring devices with Schering bridge on degraded insulating oil. The result showed that this measuring tech¬nique can be used as diagnostic method on the pole transformers.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.854-860
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• 2004

The result of fingerprint matching is different as the quality or the state of input fingerprint image. We can extract the false direction information when the quality of fingerprint is degraded by the noise or the scars of the ridges. The information of the direction is very important for the elimination of the false minutia, the measurement of the ridge distance, matching, finding of cores and deltas. We need the method which can compensate or correct the false information of directions because the false directions include serious errors in the fingerprint recognition. We propose a method which can compensate or correct the false direction of fingerprint with a \alpha$-trimmed mean filter followed by LPF to reconstruct the false direction information when fingerprints are corrupted by scars.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.8
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• pp.996-1003
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• 1999

This paper propose a position-speed controller with an estimator which can estimate states and disturbance. The overall control system consists of two parts: the position-speed controller and an estimator. The Kalman filter applied as state-feedback controller is an optimal state estimator applied to a dynamic system that involves random perturbations and gives a linear, unbiased and minimum error variance recursive algorithm to optimally estimate the unknown state. Therefore, we consider the error problem about the servo system modeling and the measurement noise as a stochastic system and implement a optimal state observer, and enhance the estimate performance of position and speed using that. Using two-degree-of freedom(TDOF) conception, we design the command input response and the closed loop characteristics independently. The servo system is to improve the closed loop characteristics without affecting the command imput response. The characteristics of the closed loop system is improved by suppressing disturbance torque effectively with the disturbance observer using a inverse-transfer matrix. Therefore, the performance of overall position-speed controller is enhanced. Finally, the performance of the proposed controller is exemplified by some simulations and by applying the real servo system.

• Journal of Power Electronics
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• v.16 no.1
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• pp.238-248
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• 2016

The state-of-charge (SOC) and state-of-health (SOH) estimation of batteries play important roles in managing batteries for automotive applications. However, an accurate state estimation of a battery is difficult to achieve because of certain factors, such as measurement noise, highly nonlinear characteristics, strong hysteresis phenomenon, and diffusion effect of batteries. In certain vehicular applications, such as idle stop-start systems (ISSs), significant errors in SOC/SOH estimation may lead to a failure in restarting a combustion engine after the shut-off period of the engine when the vehicle is at rest, such as at a traffic light. In this paper, a dual extended Kalman filter algorithm with a dynamic equivalent circuit model of a lead-acid battery is proposed to deal with this problem. The proposed algorithm adopts a battery model by taking into account the hysteresis phenomenon, diffusion effect, and parameter variations for accurate state estimations of the battery. The validity of the proposed algorithm is verified through experiments by using an absorbed glass mat valve-regulated lead-acid battery and a battery sensor cable for commercial ISS vehicles.

• Proceedings of the KIEE Conference
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• 2004.05b
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• pp.132-135
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• 2004

In generally, compared with VHF band, electromagnetic waves of UHF band have a low influence for external noise. We can detect the real abnormality with several pC in GIS using UHF method. Recently, it has applied to use the external UHF sensor attached on spacer to GIS of existing substation. In this paper, we firstly described the technique of the partial discharge measurement using frequency analysis and phase analysis in UHF band. Secondly, we presented the results of sensitivity, the relationship of dBm-pC and diagnosis of the reason of PD source by phase analysis. And then, we report the diagnosis result of partial discharge on 800kV GIS in domestic substation. rge diagnosis of GIS.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.462-463
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• 1996

This study describes the dissipation factor measuring techniques of insulating oil on the operating, transformer by using digital signal processing. After applying voltage to the sensor which is installed in a transformer, acquiring source voltage and current of sensor and using cross-correlation techniques, we can check the dissipation factor of insulating oil. To improve measuring accuracy and the speed of process, we use hardware such as TMS320C31 DSP board and analog filter and software such as fast cross-correlation techniques, rectangular window, and digital filtering techniques. We simulated the measuring accuracy and the degree of the noise effect of this new measuring techniques by computer simulation, and compared the simplified measuring devices with Schering Bridge on degraded insulating oil. The result showed that this measuring technique can be used as diagnostic method on the pole transformers.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.270-272
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• 1996

This paper describes the dissipation factor measuring techniques of insulating oil on operating pole transformer by using digital signal processor. After applying voltage to the electrodes which is installed in a transformer, acquiring source voltage and current of electrodes and using cross-correlation techniques, we can check the dissipation factor of insulating oil. To improve measuring accuracy and the speed of process, we use hardware such as TMS320C31 DSP board and software such as cross-correlation techniques and rectangular window techniques. We simulated the measuring accuracy and the degree of the noise effect of this new measuring techniques by using computer simulation, and compared the simplified measuring devices with schering bridge on degraded insulating oil. The result showed that this measuring technique can be used as diagnostic method on the pole transformers.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.93-99
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• 2006

Flexible couplers are widely used for exhaust transmitted vibration reduction in vehicles. This paper describes an investigation into the acoustical characteristics of exhaust flexible coupler by the simulation and testing. Computational acoustic simulation is carrying out to investigate resonance frequency and transmission loss of decoupler using the boundary element method and transfer matrix approach. To confirm the acoustical simulation results of exhaust decoupler, we compare with measured experimental results by the test of transmission loss measurement system. In the comparison with simulation results and tests results, there is correctly fit the resonance frequency and the trend of transmission loss. Also, we show that the acoustical structure of decoupler is analogous to the expended tube or side branch resonator. The characteristics of exhaust decoupler have a marked increase in the acoustic attenuation at the specified frequency bend. Therefore the decoupler is applied to develop the exhaust system not only for the vibration isolator but also for the noise attenuator.

• International Journal of Automotive Technology
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• v.8 no.2
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• pp.249-258
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• 2007

This paper proposes a method that can be used for the resistance estimation of a PWM (Pulse Width Modulation)-driven solenoid. By using estimated solenoid resistance, the PWM duty ratio was compensated to be proportional to the solenoid current. The proposed method was developed for use with EHB (Electro-Hydraulic Braking) systems, which are essential features of the regenerative braking system of many electric vehicles. Because the HU (Hydraulic Unit) of most EHB systems performs not only ABS/TCS/ESP (Electronic Stability Program) functions but also service braking function, the possible duration of continuous solenoid driving is so long that the generated heat can drastically change the level of solenoid resistance. The current model of the PWM-driven solenoid is further developed in this paper; from this a new resistance equation is derived. This resistance equation is solved by using an iterative method known as the FPT (fixed point theorem). Furthermore, by taking the average of the resistance estimates, it was possible to successfully eliminate the effect of measurement noise factors. Simulation results showed that the proposed method contained a sufficient pass-band in the frequency response. Experimental results also showed that adaptive solenoid driving which incorporates resistance estimations is able to maintain a linear relationship between the PWM duty ratio and the solenoid current in spite of a wide variety of ambient temperatures and continuous driving.