• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2172-2174
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• 1998

In this paper, a speed estimation based on the quick torque control is proposed to realize speed sensorless control in a full range of induction motors. The proposed method can be formulated simply from a motor circuit equation and conducted easily by detecting primary motor currents and a voltage command at every sampling time. Since the method need not the differential values of primary currents in an arithmetic of a speed, it can be expected to improve the precision of speed estimation in a very low speed area, especially. Some numerical simulations were conducted with the assumption of using a Pulse Width Modulation voltage source inverter.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.52
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• pp.1-8
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• 1999

This study was conducted to collect data concerning the preferred driving postures and adopted seat adjustment levels and to grasp relationships among drivers' body sizes, postural angles, and adopted seat positions and angles. Also optimum driving posture and seat adjustment level estimation models were constructed. An experiment was conducted to investigate observed optimum driving posture, and seat adjustment level. Thirty-six subjects (male=20, female=16) was selected to include a wide range of percentiles in the dimensions important for automotive driving workstation design and to be representative of the automotive driving population in Korea. New guidelines and estimation models for optimum postural comfort were developed. There were significant differences between male and female in postural angles but not in seat adjustment levels. Taller subjects preferred a more open and reclined posture. Estimation models enable us to estimate the quantitative optimum driving posture and seat adjustment level with some drivers' physical dimensions.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.1
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• pp.48-53
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• 2000

The novel integration method with programmable high-pass filter is suggested in order to solve the problem of integration for stator flux estimation in a stator flux oriented direct vector controlled induction motor drive system. The dc offset in a pure integrator is eliminated using high-pass filter with fixed time constant, and then time constant of programmable high-pass filter is controlled with a inverter frequency for integration in a wide frequency range, considering phase lag and attenuation due to both the hardware low-pass filter and high-pass filter. The proposed method is verified with the experimental results implemented by 32-bit DSP.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.3
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• pp.16-21
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• 2012

Global navigation satellite systems (GNSS) use dual frequency signals to remove ionosphere delay effect. GNSS receivers have their own biases, called inter-frequency bias (IFB) between dual frequencies due to differential signal delays in receiving each frequency codes. The IFB degrades pseudo-range and ionosphere delay accuracies, and they must be accurately estimated. Simultaneous estimation of ionosphere map and IFB is applied in order to analyze the IFB estimation accuracy and variability. GPS network data in Korea is used to compute each receiver's IFB. Accuracy changes due to ionosphere model changes is analyzed and the effect of external GNSS satellite IFB on the receiver IFB is analyzed.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.2 s.25
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• pp.20-25
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• 2006

Low frequency towed line array with high array gain and beam resolution is a long range surveillance sensor for anti-submarine warfare. The beam characteristics is however deteriorated due to the distorted line array sensor caused by low towing speed, wind, current, and towing ship maneuvering. An adaptive beamforming method is utilized in this paper to enhance the distorted line array beam performance by estimating and compensating the nonlinear array shape. A polynomial curve fitting in the least square sense is used to estimate the array shape iteratively with the distributed heading sensors data along the array. Real time array shape estimation and nonlinear array beam calculation is applied to a very long towed line array sensor system and the beam performance is evaluated and compared to the linear beamformer for the simulation and sea trial data.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.892-896
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• 2005

This paper presents method of depriving the relationship between static passive RFID tag and mobile robot In the field of tag-range. We use probabilistic sensor model of RFID reader by experiments. And we proposed estimation techniques by using direction of identification and relative-distance from the sensor model. Corresponding to distribution of identification, we can correct estimated tag position in relative coordinate. Simulation and Experimental Results show that the proposed method can provide good performance and thus be used fer mobile-robot localization.

• Korean Journal of Remote Sensing
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• v.23 no.5
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• pp.421-430
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• 2007

This paper presents the results of the ocean surface current velocity estimation using 6 Radarsat-1 SAR images acquired in west coastal area near Incheon. We extracted the surface velocity from SAR images based on the Doppler shift approach in which the azimuth frequency shift is related to the motion of surface target in the radar direction. The Doppler shift was measured by the difference between the Doppler centroid estimated in the range-compressed, azimuth-frequency domain and the nominal Doppler centroid used during the SAR focusing process. The extracted SAR current velocities were statistically compared with the current velocities from the high frequency(HF) radar in terms of averages, standard deviations, and root mean square errors. The problem of the unreliable nominal Doppler centroid for the estimation of the SAR current velocity was corrected by subtracting the difference of averages between SAR and HF-radar current velocities from the SAR current velocity. The corrected SAR current velocity inherits the average of HF-radar data while maintaining high-resolution nature of the original SAR data.

• Earthquakes and Structures
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• v.16 no.1
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• pp.69-82
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• 2019

As the residual displacement and/or drift demands are commonly used for seismic assessment of buildings, the estimation of these values play a very critical role through earthquake design philosophy. The residual displacement estimation of fixed base structures has been the topic of numerous researches up to now, but the effect of soil flexibility is almost always omitted. In this study, residual displacement demands are investigated for SDOF systems with period range of 0.1-3.0 s for near-field and far-field ground motions for both fixed and interacting cases. The elastoplastic model is used to represent non-degrading structures. Based on time history analyses, a new simple yet effective equation is proposed for residual displacement demand of any system whether fixed base or interacting as a function of structural period, lateral strength ratio and spectral displacement.

• Journal of the Korean earth science society
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• v.31 no.2
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• pp.119-128
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• 2010

To make reliable interpretations on the sparse spatial data, the spatial distribution characteristics that are inevitable for spatial estimation should be properly analyzed. Variograms have been widely used for obtaining the spatial characteristics inherent to data in spatial estimation problems. But their applications were limited as the basic information for further data estimation. Therefore, the additional analysis of the meaning of variograms is required for more reliable data processing and interpretations. In this paper, we investigated the proper meaning of variogram values and the specific features of distributions which can be obtained through variogram analysis. Variograms can provide the information on both linearity and the strength changes of interrelationships between the data sets according to the direction and lag distance. First, sill and range values, which are main parameters of variograms, were analyzed. Then a similarity range using spatial auto-correlation values was introduced to verify the applicability of linearity analysis through the comparative study of spatial distribution features of gravity and magnetic data collected in Hwasan caldera. Through these analyses, we were able to identify the dissimilar patterns of gravity and magnetic data that became apparent according to the distribution and variation ranges of the data sets. It is inferred that the gravity and magnetic anomalous bodies are extended to the ground because linearity direction of gravity and magnetic data appear similarly with linearity derection of topography in Hwasan caldera.

• Journal of Sensor Science and Technology
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• v.14 no.2
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• pp.116-124
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• 2005

In this paper range measurement systems are designed using an ultrasonic sensor and a camera. An ultrasonic sensor provides the range measurement to a target quickly and simply but its low resolution is a disadvantage. We tackle this problem by employing a camera. Instead using a stereoscopic sensor, which is widely used for 3D sensing but requires a computationally intensive stereo matching, the range is measured by focusing and structured lighting. In focusing a straightforward focusing measure named as MMDH(min-max difference in histogram) is proposed and compared with existing techniques. In the method of structure lighting, light stripes projected by a beam projector are used. Compared to those using a laser beam projector, the designed system can be constructed easily in a low-budget. The system equation is derived by analysing the sensor geometry. A sensing scenario using the systems designed is in two steps. First, when better accuracy is required, measurements by ultrasonic sensing and focusing of a camera are fused by MLE(maximum likelihood estimation). Second, when the target is in a range of particular interest, a range map of the target scene is obtained by using structured lighting technique. The systems designed showed measurement accuracy up to 0.3[mm] approximately in experiments.