• Journal of Electrical Engineering and Technology
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• 제2권2호
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• pp.241-248
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• 2007

The accuracy of all the schemes that belong to vector controlled induction machine drives is strongly affected by parameter variations. The aim of this paper is to examine iron losses and magnetic saturation effect in sensorless vector control of induction machines. At first, an approach to induction machine modelling and vector control scheme, which account for both iron loss and saturation, is presented. Then, a model reference adaptive system (MRAS) based speed estimator is developed. The speed estimation is modified in such a way that iron losses and the variation in the saturation level are compensated. Thus by substituting an artificial neural network flux estimator into the MRAS speed estimator. Experimental results are presented to verify the effectiveness of the proposed approach.

• 방송공학회논문지
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• 제22권3호
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• pp.397-400
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• 2017

최근 드론, 액션캠 등과 같은 촬영 장비의 활성화로 다양한 전역 움직임을 내포한 영상들이 많이 생성되고 있다. 이때 회전, 확대, 축소 등의 움직임이 발생한 경우, 2D motion vector를 활용하는 기존의 화면 간 예측 방법은 높은 부호화 효율을 기대하기 어렵다. 본 논문에서는 전역 움직임을 homography 참조 픽처를 통해 반영한 비디오 부호화 방법을 제안한다. 제안방법으로, 1) 현재 픽처와 참조 픽처간 전역 움직임 관계를 homography로 파악하여 새로운 참조 픽처를 생성하는 방법, 2) homography 참조 픽처를 화면 간 예측에 활용하는 방법이 있다. 실험은 HEVC 참조 소프트웨어인 HM 14.0에 적용하였고, 실험결과 RA 기준 6.6% 부호화 효율이 증가했다. 특히, 회전 전역 움직임을 지니는 영상을 이용한 실험 결과에서는 기존대비 최대 32.6%의 부호화 효율이 증가하는 결과를 나타내어, 드론과 같이 복잡한 전역 움직임이 자주 나타나는 비디오에서 높은 효율을 보일 수 있을 것으로 기대된다.

• 한국멀티미디어학회논문지
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• 제16권9호
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• pp.1057-1066
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• 2013

손가락 관절문(FKP, finger-knuckle-print)을 이용한 개인 인증은 손가락 관절부에 나타나는 주름의 특징을 이용하는 것으로, 텍스처의 방향 정보가 중요한 특징이 된다. 본 논문에서는 SIFT 알고리즘을 이용하여 특징점들을 추출하고, 벡터 유사도 정합을 통해 FKP를 효과적으로 인증할 수 있는 방법을 제안하다. 벡터는 질의 영상에서 추출한 특징점과 이에 대응되는 참조 영상의 특징점을 연결하는 방향 벡터로 정의된다. 국소적인 특징점 쌍으로부터 방향 벡터를 생성하기 때문에 방향 벡터 자체는 국소적인 특징만을 나타내지만, 두 영상 간에 존재하는 다른 벡터들 간의 유사도를 비교함으로써 전역적인 특징으로 확장되는 장점이 있다. 실험결과 제안하는 방법은 기존의 방향코드를 이용한 다양한 방식에 비하여 우수한 성능을 나타내었다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권4호
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• pp.350-357
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• 2005

This paper presents a mechanical sensorless vector-controlled system with parameter identification by the aid of image processor. Based on the flux observer and the model reference adaptive system method, the proposed sensorless system includes rotor speed estimation and stator resistance identification using flux errors. Since the mathematical model of this system is constructed in a synchronously rotating reference frame, a linear model is easily derived for analyzing the system stability, including motor operating state and parameter variations. Because it is difficult to identify rotor resistance simultaneously while estimating rotor speed, a low-accuracy image processor is used to measure the mechanical axis position for calculating the rotor speed at a steady-state operation. The rotor resistance is identified by the error between the estimated speed using the estimated flux and the calculated speed using the image processor. Finally, the validity of this proposed system has been proven through experimentation.

• Journal of information and communication convergence engineering
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• 제8권4호
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• pp.349-354
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• 2010

Moving pixel displacement detection algorithm using correlation functions for making panorama image on the continuous images is presented in this paper. The input images get from a CMOS image sensor (CIS). The camera is maintained by constant brightness and uniform sensing area in test input pattern. For simple navigation and capture image has to 70% overlapped region. A correlation rate in two image data is evaluated by using reference image with first captures, and compare image with next captures. The displacement of the two images are expressed to second order function of x, y and solved with finding the coefficient in second order function. That results in the change in the peak correlation displacement from the reference to the compare image, is moving to pixel length. The navigating error is reduced by varying the path because the error is shown in the difference of the positioning vector between the true pixel position and the navigated pixel position. The algorithm performance is evaluated to be different from the error vector to vary the navigating path grid.

• 한국항공우주학회지
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• 제47권3호
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• pp.220-227
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• 2019

궤도상에 있는 인공위성은 천문력 기반 태양 모델을 사용하여 기준 벡터를 형성한다. 이를 위해 제트 추진 연구소(JPL)에서 개발한 천문력인 DE-Series, 또는 Vallado가 제안한 기준 벡터 생성식을 사용한다. DE-Series는 체비셰프 다항식의 수치 계수를 제공하는데 정밀도가 높다는 장점이 있지만 인공위성의 탑재 컴퓨터의 계산 부담이 있으며, Vallado 방식은 생성식을 통해 태양 벡터를 간단히 구할 수 있지만 낮은 정밀도를 제공한다. 본 논문에서는 DE-Series를 통해 얻은 태양의 위치를 체비셰프 다항식으로 Curve fitting하여, 관성좌표계에서의 태양 위치좌표를 구할 수 있는 체비셰프 다항식 계수를 제공하는 프로그램을 개발하였다. 기존 방식에 비해 정밀도를 향상시킬 수 있었으며, 제안된 방법은 고성능, 고정밀 초소형위성 임무에 활용될 수 있다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.443-447
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• 2001

In this paper, a robust sensorless vector control system for induction motors with a speed estimator and an uncertainty observer is presented. At first, the proposed speed estimator is based on the MRAS(Mode Reference Adaptive System) scheme and constructed with a simple fuzzy logic(FL) approach. The structure of the proposed FL estimator is very simple. The input of the FL is the rotor flux error difference between reference and adjustable model, and the output is the estimated incremental rotor speed Secondly, the unmodeled uncertainties such as parametric uncertainties and external load disturbances are modeled by a radial basis function network(RBFN). In the overal speed control system, the control inputs are composed with a norminal control input and a compensated control input, which are from RBFN observer output and the modeling error of the RBFN, repectively. The compensated control input is derived from Lyapunov unction approach. The simulation results are presented to show the validity of the proposed system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.466-469
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• 2001

In this paper, closed loop V/f control of induction motor has been implemented by the estimated speed. Closed loop V/f control improve the performance of induction motor drive system at low speed compared to open loop V/f control. However, closed loop V/f control need speed sensor. By using the estimated speed, closed loop V/f control is possible without speed sensor. Rotor speed is calculated from the difference between synchronous frequency and slip angular frequency. 3-phase voltage reference is obtained from synchronous frequency. And the PWM technique using space vector PWM is applied in this scheme. In the space vector PWM, effective time of 3-phase voltage reference is used to simplify the calculation of effective voltage time. This scheme is simple to implement and one chip microprocessor was used in experimental system.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1366-1370
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• 2010

This paper supposes the vector control algorithm to estimate the rotor position of permanent magnet synchronous traction motor using the hall-effect sensor. The hall-effect provides 60 electrical degrees resolution in rotor position sensing and it is very low resolution. The algorithm makes resolution high as optical encoders or electromagnetic resolver. If necessary, the reference rotor position angle is controlled by adjusting the variable. When a rotor position sensor such as either a optical encoder or a electromagnetic resolver is misalignment, it is useful to align with those. The method on adjusting the reference rotor position angle can compensate for misalignment error degrees by 60 electrical degrees.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.200-204
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• 2002

When the vector control, which does not need a speed? signal from a mechanical speed sensor, it is possible to reduce the cost of the control equipment and to improve the control performance in many industrial application. This paper describes a rotor speed identification method of induction motor based on the theory of flux model reference adaptive system. The estimator execute the rotor speed identification so that the vector control of the induction motor may be achieved. The improved auxiliary variable of the two model are introduced to perform accurate rotor speed estimation. Simulation result show the validity of the proposed control method.