• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.183-187
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• 2007

This paper proposes Fuzzy Speed Estimator using Fuzzy Logic Controller(FLC) as a adaptive law in Model Reference Adaptive System(MRAS) in order to realize the speed-sensorless control of an induction motor. Fuzzy Speed Estimator estimates the speed of an induction motor with a rotor flux of the reference model and the adjustable model in MRAS. Fuzzy logic controller reduces the error of the rotor flux between the reference model and the adjustable model using the error and the change of error of the rotor flux as the input of FLC. The experiment is executed to verify the propriety and the effectiveness of the proposed speed estimator.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.795-796
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• 2008

H.264/AVC standard adopts multiple reference frames for motion estimation. This method improves coding efficiency, but it increases complexity of encoder. In this paper, we propose a algorithm that reduces the search range by using the correlation of motion vector. Consequently, motion estimation processing time is 47.5% when compared with standard of five reference frames, and SNR and bitrate are better than that of standard of three multi reference frames.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.8 s.197
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• pp.97-107
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• 2007

The present CNC machining system if without any CAM software has been limited to 2D or 2.5D plane cut using lines, arcs and curves. If the CNC is equipped with a surface interpolation module and a surface reorganizing module inside it, we can easily try 3D surface machining without aid of CAM software. The existing NURBS surface interpolator is simple and direct to use for a unit surface. However, it enables only machining of each reference surface individually even when machining a simple composite surface. In this paper, we propose a method which can unify and reorganize various reference surfaces with a newly defined NURBS surface cycle command: a multi-repetitive cycle command such as in a CNC turning center. We also introduce a reorganizing rule for reference surfaces using NURBS properties. The usefulness of the proposed method is verified through computer simulation.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.292-294
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• 2007

Recently, for satisfying many application demands such as coding delay, computing power, transporting channel characteristic, etc, many profiles are supported in video coding standards. Therefore, in transcoding between same standards or between other standards, the functional difference of profiles supported by application occur many problems. In this paper, transcoding MPEG-2 main profile to H.264/AVC baseline profile which has restriction in the number of reference frame is focused. In this case, the bidirectional prediction supported in MPEG-2 main profile is not supported in H.264/AVC baseline profile. Also, in the restriction of reference frame, motion vectors in the MPEG-2 decoder as predictor should be adjusted. In this paper, the proposed algorithm is based on the characteristic of which motion. vector is uniform according to the distance from reference frame. The adaptive search techniques through the determination of the uniformity extremely reduce the computational complexity.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.6
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• pp.102-109
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• 2000

In this industrial induction motor speed and torque controlled drive system, the closed loop control usually requires the measurement of speed or position of amotor. However a sensorless drive of an induction motor has several advantages ; low cost and mechanical simplicity. Thus this paper investigates a field oriented control method without speed and flux sensors. The proposed control strategy is based on the Model Reference Adaptive System(MRAS) using a new flux estimator which replaces integrators with two lag circuits as the reference model. This algorithm may overcome several shortages of conventional MRAS such as integrator problems, small EMF at low speed. The simulation and experimental results indicate good speed responses.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.11-16
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• 1998

In this paper, simultaneous estimation of rotor speed and time constant for a voltage source inverter (VSI) fed induction motor drive are disccussed. The theory is based on the Model Reference Adaptive System (MRAS). The identifier executes Simultaneous rotor speed and time constant so that vector control of the induction may be achieved in the rotor-flux oriented reference frame. Furthermore, to eliminate the offset error caused by the change in the stator resistance, a fuzzy resistance regulator is also designed which operates in parallel with the rotor speed and time constant identifier

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.222-224
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• 2002

This paper investigates the adaptive control of a fuzzy logic based speed and flux controller for a vector controlled induction motor drive. A model reference adaptive scheme is proposed in which the adaptation mechanism is executed by fuzzy logic based on the error and change of error measured between the motor speed and output of a reference model. The control performance of the model reference adaptive control(mAC) fuzzy controller is evaluated by simulation for various operating conditions. The validity of the proposed MRAC fuzzy controller is confirmed by performance results for induction motor drive system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.5
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• pp.1388-1399
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• 2012

This paper proposes a quality metric based on a No-Reference Bitstream (NR-B) having least computational complexity for the assessment of the human-perceptual quality of H.264 encoded video. The proposed NR-B method performs a modeling of encoding distortion with three bit-stream information (i.e. frame-rate, motion-vector, and quantization-parameter) that can be directly extractable from the encoded bitstream and does not require additional complex processing of final pictures. From performance evaluation using 165 compressed video sequences, the experiment results show that the proposed metric has a higher correlation with subjective quality than is achieved with other comparable methods.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.8
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• pp.81-95
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• 1996

In this paper, we propose a motio estiamtion algorithm using low-resolution quantization to reduce the computation of the full search algorithm. The proposed algorithm consists of the low-resolution search which determins the candidate motion vectors by comparing the low-resolution image and the full-resolution search which determines the motion vector by comparing the full-resolution image on the positions of the candidate motion vectors. The low-resolution image is generated by subtracting each pixel value in the reference block or the search window by the mean of the reference block, and by quantizing it is 2-bit resolution. The candidate motion vectors are determined by counting the number of pixels in the reference block whose quantized codes are unmatched to those in the search window. Simulation results show that the required computational cost of the proposed algorithm is reduced to 1/12 of the full search algorithm while its performance degradation is 0.03~0.12 dB.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.7
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• pp.494-499
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• 2000

In a conventional stator flux-oriented(SFO) induction machine drive system, the field weakening method is to vary flux reference in proportion to the inverse of the rotor speed. This paper investigates that maximum torque capability cannot be obtained in the conventional system and proposes a new selection method of flux reference to obtain maximum torque capability over the field weakening region by considering voltage, torque, and current limits.