• The KIPS Transactions:PartC
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• v.15C no.1
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• pp.31-36
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• 2008

The clock frequency difference of sensor nodes is one of main parameters in TOF estimation and affect to degrade ranging algorithms to estimate positions of mobile nodes in wireless sensor networks. The specification of IEEE802.15.4a describes asynchronous TWR and SDS-TWR insensitive to frequency difference without any additional network synchronization. But the TWR and SDS-TWR can not eliminate sufficiently the effect of frequency difference of node pair, packet processing delay and its difference. Especially use of low cost oscillator with wide range offset, sensor node with different hardware and software can make the positioning errors worse. We propose an estimation method of frequency differences, and apply the measured frequency differences to TWR and SDS-TWR. We evaluate the performance of the proposed algorithm with simulation, and make certain that the proposed method enhances the performance of existing algorithms with positioning errors less than 25 cm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.2C
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• pp.170-183
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• 2002

This paper proposes an efficient frequency and symbol synchronization structure which could solve problems of the conventional methods to implement DVB-T receive modem which adopted OFDM transmission method. The main considerations of frequency synchronization algorithms are that the frequency tracking performance is not stable enough, and lots of symbols are required, especially when the decimal part of normalized frequency offset (which original frequency offset is divided by the subcarrier spacing) is around $\pm$0.5 to solve these problems, we propose an efficient frequency offset is divided by the subcarrier spacing) is around $\pm$0.5 by using the average of coarse synchronization over several symbol. Also, we suggest a new symbol synchronization structure which is easy to implement without performance degradation in multipath fading channel with only coarse symbol synchronization by making window offset to the range of guard interval in contrast to the conventional structure of dividing symbol synchronization in fine and coarse mode during synchronization. By extensive simulation, we have shown the superiority of the proposed schemes.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.12
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• pp.1209-1218
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• 2016

In order to safely and speedily transport a load such as a large glass plate using four electric cylinders, the synchronous error outside the permitted range should not be continuously generated between the cylinders. In this study, a methodology of synchronous control which can be applied to synchronization of four or more cylinders is developed. The synchronous control system based on the decoupling structure is composed of a reference model, position and synchronous controllers in the respective cylinders. The reference model is used for calculating the decoupled synchronous error and control input for the each cylinder. The position controller of I-PD type is designed in order that the cylinder may follow the reference signal without overshoot and input saturation. And the synchronous controller of lead compensator is designed to achieve stable and accurate synchronization through loop shaping approach. Finally, the simulation results show that the synchronization between the four cylinders can be quickly and stably while each cylinder rod is transferred to the target point under torque disturbance.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.158-159
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• 2017

본 논문에서는 매입형 영구자석 동기전동기를 위치센서 없이 기동하기 위해 회전자의 초기 위치를 추정하는 방법을 제안한다. 제안된 방법은 자기 인덕턴스의 포화현상에 따른 고정자 전류를 해석하고 최소자승법을 통해 회전자의 초기 위치를 추정한다. 전 구간에서 회전자의 초기 위치와 극성을 정확하게 알아낼 수 있어 돌극성 때문에 나타나는 릴럭턴스 토크를 효과적으로 사용할 수 있다. 또한, 전동기 정수에 영향을 받지 않으므로 다양한 전동기 구동 시스템에 적용할 수 있으며, 추가적인 하드웨어가 필요하지 않아 경제적이다. 제안하는 방법의 유효성과 우수성은 시뮬레이션을 통해 검증한다.

• Journal of Advanced Navigation Technology
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• v.26 no.5
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• pp.319-324
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• 2022

If radio interference occurs or there is no navigation device, radio navigation of high-speed moving object becomes impossible. Nevertheless, if there are multiple ground stations and precise range measurement between the high-speed moving object and the ground station can be secured, it is possible to estimate the position of moving object. This paper proposes a position estimation method using high-precision TDOA measurement generated using TLM signal. In the proposed method, a common error of moving object is removed using the TDOA measurements. The measurements is generated based on TLM signal including SOQPSK PN symbol capable of precise timing synchronization. Therefore, since precise timing synchronization of the system has been performed, the timing error between ground stations has a very small value. This improved the position estimation performance by increasing the accuracy of the measured values. The proposed method is verified through software-based simulation, and the performance of estimated position satisfies the target performance.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.2
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• pp.124-129
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• 2005

This paper presents an advanced method for an initial pole position estimation of a Permanent Magnet Linear Synchronous Motor(PMLSM) that has an accurate incremental encoder for servo applications but does not have Hall sensors as a magnetic pole sensor. By appropriately using the secant method as a numerical method the proposed algorithm finds either of two zero force positions and then the correct d-axis by applying a q-axis test current. It only requires the tuned current controller and the relative position information md so it can be simply applicable to a rotary PMSM. The experimental results show the validity of the proposed method, which has an excellent performance with respect to an accurate pole position estimation under the minimal moving distance(average of about 85㎛) during the estimation process.

• 전자공학회논문지 IE
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• v.43 no.1
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• pp.59-66
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• 2006

In this study, we have proposed a motion equation to control synchro drive mobile robot, a path plan to compute and track the best path to given destination and a technique utilizing uniform distribution and cluster management based Monte Carlo localization to have track current position of moving robot. In the localization test which was repeated 73 times resulted as following. The average process time of original Monte Carlo localization was 12.8ms. The proposed cluster management Monte Carlo localization resulted 9.3ms. Also the proposed method resulted correctly in the cases where original method failed.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.214-216
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• 2003

아날로그 NTSC 비디오 디코더 신호를 디코딩하여 디지털화된 컬러 값을 얻기 위해서는 컬러 버스트 신호를 동기화 해야 한다. 이 버스트 신호를 이용하여 Y. I. O의 값을 분리하기 때문이다. 아날로그 디코더의 경우에는 내부에 버스트 신호와 동기화 한 클럭을 PLL이나 DLL등을 이용하여 발생시켜서 I의 위치를 알아낸다. 비디오 신호 해독을 위한 전용의 PLL을 위해 아날로그 방식의 VLSI설계를 하는 것은 많은 노력이 들어갈 뿐만 아니라 특정 Fab에 종속되어 전체 칩의 이식성을 떨어뜨리게 된다. 본 논문에서는 아날로그 PLL이 없이도 디지털 입력데이터의 산술 연산을 통해서 컬러 버스트 동기화를 검출하는 방법을 제안한다.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.567-568
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• 2011

영구자석 동기 전동기의 센서리스 구동에 있어서 위치와 속도를 정확히 추정하는 것이 중요하다. 정확한 위치와 속도의 추정을 위해서는 정확한 모터 파라미터가 필요한데, 특히나 magnetic saturation에 의한 q-축 인덕턴스의 영향이 가장 크기 때문에 이 논문에서는 매입형 영구자석 동기 전동기(IPMSM)의 센서리스 구동을 위한 q축 인덕턴스 추정에 대한 시뮬레이션 결과와 실험 결과를 나타내었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.9
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• pp.1415-1421
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• 2004

In this study, a position synchronous control algorithm applied to two-axes pneumatic cylinder driving apparatus is proposed. The position synchronous control algorithm is composed of position controller and synchronous controller. The position controller is designed to minimize the effect of several nonlinear characteristics peculiar to the pneumatic cylinder driving apparatus on position control performance. The synchronous controller is designed to reduce the synchronous error. The effectiveness of the proposed control algorithm is proved by experimental results.