• Maxillofacial Plastic and Reconstructive Surgery
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• 제42권
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• pp.37.1-37.13
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• 2020

Background: The human mandible is variable in shape, size and position and any deviation from normal can affect the facial appearance and dental occlusion. Objectives: The objectives of this study were to determine whether the Sassouni cephalometric analysis could help predict two-dimensional mandibular shape in humans using cephalometric planes and landmarks. Materials and methods: A retrospective computerised analysis of 100 lateral cephalometric radiographs taken at Kingston Hospital Orthodontic Department was carried out. Results: Results showed that the Euclidean straight-line mean difference between the estimated position of gonion and traced position of gonion was 7.89 mm and the Euclidean straight-line mean difference between the estimated position of pogonion and the traced position of pogonion was 11.15 mm. The length of the anterior cranial base as measured by sella-nasion was positively correlated with the length of the mandibular body gonion-menton, r = 0.381 and regression analysis showed the length of the anterior cranial base sella-nasion could be predictive of the length of the mandibular body gonion-menton by the equation 22.65 + 0.5426x, where x = length of the anterior cranial base (SN). There was a significant association with convex shaped palates and oblique shaped mandibles, p = 0.0004. Conclusions: The method described in this study can be used to help estimate the position of cephalometric points gonion and pogonion and thereby sagittal mandibular length. This method is more accurate in skeletal class I cases and therefore has potential applications in craniofacial anthropology and the 'missing mandible' problem in forensic and archaeological reconstruction.

• 한국산학기술학회논문지
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• 제11권4호
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• pp.1294-1300
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• 2010

노드들 모두가 움직이는 환경에서 센서 노드는 통신반경 안의 앵커 노드 위치정보를 수신 받아 자신이 이동한 거리와 방향만큼 수신한 앵커 노드 위치정보를 수정하여 자신의 메모리에 저장하고, 3개 이상이 되면 삼변 측량에 의해 localization을 수행하여 자신의 위치를 결정한다. 일정한 거리를 유지하고 노드들이 같은 방향으로 움직이는 환경에서는 센서 노드가 1홉 범위에서 절대좌표를 가진 앵커 노드를 3개 이상 만날 확률이 적다. 만약 센서 노드가 3개 이상의 비콘 정보로 자신의 위치를 추정하였다고 하여도 시간이 경과하면서 가속도기와 디지털 나침반의 각 ${\theta}$ 오차가 지속적으로 적용되어 오차범위는 커지고 추정된 위치도 신뢰받지 못한다. Dead reckoning 기술은 GPS가 동작하지 않는 곳에서 보조적인 위치 추적 항법 기술로 사용되고 있는데 가속도 센서와 디지털 나침반으로 노드가 움직인 거리와 방향을 알면 자신의 위치를 추정할 수 있다. 위치 인식 알고리즘은 Dead reckoning 을 이용한 위치인식 기법으로 모든 노드가 전방향성 안테나를 장착하고, 가속도기와 디지털 나침반으로 자신이 이동한 거리와 이동 방향을 알 수 있다고 가정한다. Matlab을 이용하여 시뮬레이션한 결과 다른 기법(MCL,DV-distance)들 보다 우수함을 증명하였다.

• 한국통신학회논문지
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• 제37B권10호
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• pp.889-900
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• 2012

무선 센서 네트워크에서 수신 신호 세기를 이용한 위치추정 방식은 다수의 저전력 노드로 구성된 센서네트워크에 적합한 방법 중의 하나로 고려되고 있다. 수신 신호 세기를 이용한 위치추정 방식의 오차를 줄이기 위해서는 적절한 경로 감쇄 지수 (path-loss exponent, PLE)의 추정이 요구된다. 기존의 위치 추정 방식은 자신의 위치를 알고 있는 각각의 앵커가 인접한 앵커들을 참조하여 PLE를 측정하고, 자신의 위치를 알고자 하는 센서 노드는 수신 신호 세기를 기반으로 가장 인접한 앵커를 판별한 후, 해당 앵커가 측정한 PLE를 자신의 위치 추정에 이용하는 방식을 취하고 있다. 이때의 PLE는 인접한 앵커의 위치에서 측정된 것이기 때문에 실제 측정한 위치에서만 높은 신뢰성을 가지며, 그 외의 위치에서는 다른 값을 갖는 경우가 일반적이다. 따라서 인접한 앵커들을 참조하여 추정한 PLE를 센서 노드의 위치 추정에 직접적으로 이용하는 것은 위치 추정 시 오차를 발생 시키는 주요 원인이 된다. 본 논문에서는 센서 노드 스스로가 각각의 인접한 앵커들에 대한 PLE를 추정하고, 이를 이용하여 센서 노드의 위치를 추정하는 기법을 다루며, 특히, 추정된 센서 노드의 위치에서 각 앵커들까지의 거리를 기반으로 PLE를 반복적으로 재추정하도록 하여 위치 추정 오차를 줄이도록 하는, 반복 PLE 추정을 통한 위치 추정 기법을 제안한다. 성능평가에서는 제안된 기법이 기존의 방법보다 위치 추정 오차를 줄일 수 있음을 보였다.

• 제어로봇시스템학회논문지
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• 제14권12호
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• pp.1205-1211
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• 2008

This paper describes methods to estimate 3-D position of target with respect to reference frame through monocular image from unmanned aerial vehicle (UAV). 3-D position of target is used as information for surveillance, recognition and attack. In this paper. 3-D position of target is estimated to make guidance and control law, which can follow target, user interested. It is necessary that position of target is measured in image to solve 3-D position of target. In this paper, kalman filter is used to track and output position of target in image. Estimation of target's 3-D position is possible using result of image tracking and information of UAV and camera. To estimate this, two algorithms are used. One is methode from arithmetic derivation of dynamics between UAV, carmer, and target. The other is LPV (Linear Parametric Varying). These methods have been run on simulation, and compared in this paper.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제2B권3호
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• pp.125-132
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• 2002

PMSMS (permanent magnet synchronous motors) are widely used in industrial applications and home appliances because of their high torque to inertia ratio, superior power density, and high efficiency. For high performance control, accurate informations about the rotor position is essential. Sensorless algorithms have lately been studied extensively due to the high cost of position sensors and their low reliability in harsh environments. A novel position sensorless speed control for PMSMs uses indirect flux estimation and is presented in this paper. Rotor position and angular velocity are estimated by the proposed indirect flux estimation. Linkage flux and magnetic field flux are calculated by the voltage equations and the measured phase current without any integration. Instead of linkage flux calculation with integral operation, indirect flux and differential magnetic field are used for the estimation of rotor position. A proper rejection technique fur current noise effect in the calculation of differential linkage flux is introduced. The proposed indirect flux detecting method is free from the integral rounding error and linkage flux drift problem, because differential linkage flux can be calculated without any integral operation. Furthermore, electrical parameters of the PMSM can be measured by the proposed TCM (time compression method) for soft starting and precise estimation of rotor position. The position estimator uses accurate electrical parameters that are obtained from the proposed TCM at starting strategy. In the operating region, a proper compensation method fur temperature effect can compensate fir the estimation error from the variation of electrical parameters. The proposed novel position sensorless speed control scheme is verified by the experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.134-136
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• 2008

In recent years, the switched reluctance motor have been used many industrial application because of its cost advantage. SRM drivers are accomplished by switching the phase currents on and off synchronously with the rotor position which is fed back to the controller by position may deteriorate in harsh environments and increase the size and cost of the SRM drive system. This paper proposes a position sensorless method that is based on impressed pulse voltage using impressed at unenergised phases to estimate the rotor position. The current value by impressed pulse voltage compare with the threshold value. The rotor position can be estimated by observing the current value. Finally, simulation results compare with the sensor type SRM and confirm the proposed method to be useful.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.176-178
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• 2003

This paper presents a new velocity estimation strategy of a non-salient permanent magnet synchronous motor(PMSM) drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system which has the information of rotor position error. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error to aero. For zero and low speed operation, the PI gains of rotor position tracking controller have a variable structure. The PI tuning formulas are derived by analyzing this control system using the frequency domain specifications such as phase margin and bandwidth assignment.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1449-1455
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• 2017

The vector control technique using low-resolution Hall-effect sensors has been widely used especially in consumer electronics. Due to electrical and/or mechanical unevenness related to binary-type Hall sensors, the calculated or estimated position information has discontinuities so called bumps, which causes the deterioration of vector control performance. In order to obtain a linearly changing position signal from low-precision Hall-effect sensors, this paper proposes a simple bumps in position signal removal algorithm that consists of a first-order observer with low-pass filtering scheme. The proposed algorithm has the feature of no needs for system parameters and additional estimation processes. The validity of the proposed method is verified through simulation and experimental results.

• 제어로봇시스템학회논문지
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• 제10권4호
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• pp.317-324
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• 2004

The ink jet printer media advance system is required to be exactly driven to the target position via tracking the reference velocity profile to obtain the high quality print image. A single gain PID controller is not sufficient to fulfill the control objectives, the exact velocity tracking and the accurate positioning, at the same time. A dual PID controller and its switching strategy are presented in this paper to achieve the control objectives. The media advance system is controlled by two separate PID controllers, one of which is for velocity control, and the other is for position control. A PID controller controls the velocity of the media advance system until it reaches the predetermined switching position. When the media advance system passes the predetermined position, the controller is switched to the other PID controller which is more profitable for exact positioning. The switching position is determined by the estimated stop distance. The simulation and experimental results are presented to show the validity and effectiveness of the proposed controller.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.127-131
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• 2003

This paper describes an initial pole position estimation method of a magnetic pole sensorless permanent magnet synchronous motor(PMSM) with an incremental encoder, The accurate initial pole position is estimated by using an efficient numerical method of Secant Method, which finds either of two zero torque/force positions and then the correct d-axis. It can be simply applicable to both rotary and linear PMSM because it only requires the tuned current controller and the relative position information. The experimental results show the validity of the proposed method with respect to highly accurate pole position estimation under the moderate moving distance and convergence time.