• Journal of Power Electronics
• /
• 제14권6호
• /
• pp.1243-1253
• /
• 2014

The phase inductance of a switch reluctance motor (SRM) is significantly nonlinear. With different saturation conditions, the phase inductance shape is clearly changed. This study focuses on the relationship between coefficient and current in an inductance model with ignored harmonics above the order of 3. A position estimation method based on the variable coefficient inductance model is proposed in this paper. A four-quadrant sensorless control system of the SRM drive is constructed based on the relationship between variable coefficient inductance and rotor position. The proposed algorithms are implemented in an experimental SRM test setup. Experimental results show that the proposed method estimates position accurately in operating two/four-quadrants. The entire system also has good static and dynamic performance.

• 한국정밀공학회지
• /
• 제17권6호
• /
• pp.153-161
• /
• 2000

In controlling servomechanism, such as X-Y tables, friction is one of the most significant source of tracking error. Existing friction models work well when the direction of the motion does not change. However, when the direction of motion changes such as traversing a circular profile, relatively large tracking errors referred to as 'quadrant glitches' are introduced. In this paper, a new friction model, which has a term that can compensate the effect of the quadrant glitches, is proposed. The performance and effectiveness of the proposed model are evaluated through the experimental work. The results show that the controlling servomechanism with the proposed model completely remove the quadrant glitches.

• Journal of international Conference on Electrical Machines and Systems
• /
• 제1권2호
• /
• pp.91-97
• /
• 2012

This paper presents a state space model of a two quadrant chopper and PWM inverter-fed Interior Permanent Magnet Synchronous Motor (IPMSM) drive system and its application to hybrid vehicles. The drive system has two different state equations for motoring and regenerating action. This paper presents a common state equation by using State Space Averaging method. Using this model of the IPMSM drive system, detailed simulation and controller design of the drive system, including PWM inverter switching, are given. The validity of this model and usefulness, according to a comparison among Maximum Torque/Ampere control, Maximum Torque/Flux control, and Maximum Efficiency optimization, are confirmed from simulation results.

• 제어로봇시스템학회논문지
• /
• 제5권4호
• /
• pp.462-470
• /
• 1999

In this paper, we proposed a cross-couple controller for compensating nonlinear friction of the X-Y table of CNC machines. Due to the nonlinearity of the frictions, large contour errors, referred to as quadrant glitches, occur when each axis of the X-Y table makes a zero velocity crossing. To reduce the quadrant glitches the friction compensators and nonlinear friction observers for estimating Coulomb frictions are employed in the proposed method. A hyperbolic tangent function is used in reducing the magnitude of quadrant glitches and the CEM (Contour Error Model) is utilized for the estimation of the velocities. The performance of the proposed compensators is evaluated for several trajectories by computer simulations.

• 대한조선학회논문집
• /
• 제38권4호
• /
• pp.1-10
• /
• 2001

비 압축성 점성 유동에 대한 RANS 방정식의 수치 해법을 사용해서 4상한(four quadrant) 조건에서 작동하는 박용 프로펠러 주위의 난류 유동과 프로펠러 단독 성능을 계산하였다. 4상한 조건의 단독 성능에 대한 실험결과가 존재하는 모형 프로펠러 P4381에 대하여 계산된 유동은 다양한 조건에서 프로펠러에 발생하는 3차원 유동박리를 포함한 복잡한 점성유동 특성을 잘 보여주었으며, 계산된 프로펠러 추력과 토크는 실험에서 캐비테이션이 심하게 발생된 일부 경우를 제외하고는 실험 결과와 잘 일치하였다.

• International Journal of Reliability and Applications
• /
• 제7권1호
• /
• pp.55-69
• /
• 2006

This paper presents a new class of multivariate distributions with Pareto where dependence among the components is characterized by a latent random variable. The new class includes several multivariate and bivariate models of Marshall and Olkin type. It is found the bivariate distribution with Pareto is positively quadrant dependent and its mixture. Some important structural properties of the bivariate distributions with Pareto are discussed. The distribution of minimum in a competing risk Pareto model is derived.

• Journal of Power Electronics
• /
• 제14권3호
• /
• pp.572-579
• /
• 2014

As a non-linear time variant system, the four-quadrant line converter of an electric multiple unit (EMU) was expressed by linear time periodic functions near an operating point and modeled by a steady-state harmonic domain matrix. The components were then combined according to the circuit connection and relations of the feedback control loops to form a complete converter model. The proposed modeling method allows the study of the amplitude of harmonic impedances to explore harmonic coupling. Moreover, the proposed method helps provide a better design for the converter controllers, as well as solves the problem in coordination operation between the EMUs and the AC supply. On-site data from an actual $CRH_2$ high-speed train were used to validate the modeling principles presented in the paper.

• 통상정보연구
• /
• 제12권2호
• /
• pp.59-83
• /
• 2010

The purposes of the study is to evaluate the discrepancy between user's expectation and satisfaction degree in the service of uTradeHub. In this regard, this study infers general solutions in order to induce the intersection area using IPA technique. Then this paper will present directions to improve the service of uTradeHub. In terms of methodology, this article disclosed that IPA model approach is greatly useful to evaluate user's attribute. First, variables like the link of different works(f1), trust of system(f4), information connection(f7) are located on the first quadrant. This means that importance and satisfaction are all high variables for user. So, this is very important variables that need continuous administration in order to maintain present state. Second, variables such as the speed of information acquisition(f2), improvement of use(f3), stability of system(f5) are located on the second quadrant. This means that user's importance is high but user's satisfaction is low. Therefore, this area needs an active improvement strategy and quick maintenance for e-Trade application. Third, variables like the appropriateness of information usage fees(f8), easy subscription(f9), customer support service(f10) are located on the third quadrant. Because these variables are all low for user's importance and satisfaction, we have to arrange strong and radical remedy for e-Trade service. Finally, variables like information offer(f6) are located on the fourth quadrant. This means that user's satisfaction is high but user's importance is low. The research result suggests that e-Trade service development would be re-organised as much as user feels the importance of process innovation.

• 한국식품영양학회지
• /
• 제21권1호
• /
• pp.97-105
• /
• 2008

An IPA model was used to evaluate customer service encounters at a large food court; also the gaps between importance and performance from were also evaluated from both perspectives. The findings of this study will be applied in order to improve service quality at various large food service operations. A total of 298 customers from a large shopping mall food court completed the study questionnaire, asking them to evaluate the important and performance attributes of service. Seven underlying dimensions were identified and labeled by factor analysis: factor 1 was "safety": factor 2 "time": factor 3 "atmosphere": factor 4 "quality of food": factor 5 "menu attributes": factor 6 "comfort": and the last and seventh factor was "comprehension". As a result of IPA analysis the overall mean scores between the importance attributes and performance attributes showed significant differences by independent t-tests(p<0.001). Quadrant I was classified with unnecessary items including interior design, proper lighting, suitable chairs, and proper room temperature. In quadrant II thirteen variables showed high scores for both importance and performance, such as various menu choices, hygienic food, dishes, chairs, food court, kitchen, and employees; proper ventilation, employee kindness, waiting time to order, and received food; automatic system for ordering-serving. Quadrant III included eight variables identified as low priority, including appearance of food, nutrient content of food, proper portions, new menu, proper music, proper location of cashier, services for children and efficiency of movement. In quadrant IV six variables were included as areas to focus management's efforts, such as food taste, proper food temperature, use of safe food materials, maintenance of food quality, existence of preferred foods, and proper food prices. These results suggest that food court customers have interests that are distinct from restaurant customers and may need to be treated differently. It is anticipated that this data will be useful to the foodservice industry in order to segment customer characteristics by different dinning behaviors.

• 한국통신학회논문지
• /
• 제27권4A호
• /
• pp.371-382
• /
• 2002

현재까지 스테레오 시각 분야에서 사용된 카메라 구조는 대부분 두 광축이 평행한 시각 모델이였으나, 본 논문에서는 인간시각체계에 기반한 교차시각 스테레오 카메라 모델을 사용한다. 교차시각에서 획득한 스테레오 영상을 고정점에 대해서 4개의 영역으로 구분한다. 이러한 사분면 형태의 영역 분할 근거를 인간시각체계에서 살펴보고, 타당성을 기하학적으로 입증할 것이다. 그리고 분할된 한 쌍의 스테레오 영상으로부터 합성 영상 조각들을 형성한 후, 수정된 켑스트럼 작용과 피크 검출 알고리즘을 수행하여, 수평 및 수직 변위를 추출한다. 측정된 변위 벡터와 교차시각 스테레오 카메라 모델의 변수로부터 합성영상의 3차원 정보를 계산한다. 여러 스테레오 영상에 대해서 제안 방법의 결과가 인간시각체계처럼 고정점 부근에서 정확함을 보여주었다.