• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.9
• /
• pp.1741-1749
• /
• 2009

It is very important to maintain the balanced output voltage waveforms under the unbalanced DC-link voltages in the four-switch three-phase inverter(FSTPI). In this paper, the improvement of output voltage waveforms is proposed with the aid of DC-link voltage ripple estimation. The proposed method can be implemented without the additional voltage sensor. The proposed method applied to the permanent magnet synchronous motor (PMSM) is simulated and experimented in order to verify its feasibility.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.498-499
• /
• 2007

금속 비저항의 측정방법은 4단자 방법을 비롯한 van der Pauw 방법, Four-Point Probe(FPP) 방법, eddy current 방법 등이 사용되고 있으며, 시료의 혈상과 크기에 따라서 그 측정방법은 각각 다르다. 본 연구에서는 그 중 4단자 방법에 의한 정밀측정방법과 측정불확도 평가에 관하여 고찰하였다. 4단자 방법은 시료가 바(bar)나 봉(rod) 형상이면 측정이 가능하며, 시료의 정밀가공과 측정기술을 통하여 측정 불확도를 줄일 수 있다.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.11 no.6
• /
• pp.361-367
• /
• 2016

In this paper, we propose an improved single view metrology (SVM) algorithm to accurately measure the height of objects. In order to accurately measure the size of objects, vanishing points have to be correctly estimated. There are two methods to estimate vanishing points. First, the user has to choose some horizontal and vertical lines in real world. Then, the user finds the cross points of the lines. Second, the user can obtain the vanishing points by using software algorithm such as [6-9]. In the former method, the user has to choose the lines manually to obtain accurate vanishing points. On the other hand, the latter method uses software algorithm to automatically obtain vanishing points. In this paper, we apply image resizing and edge sharpening as a pre-processing to the algorithm in order to improve performance. The estimated vanishing points algorithm create four vanishing point candidates: two points are horizontal candidates and the other two points are vertical candidates. However, a common image has two horizontal vanishing points and one vertical vanishing point. Thus, we eliminate a vertical vanishing point candidate by analyzing the histogram of angle distribution of vanishing point candidates. Experimental results show that the proposed algorithm outperforms conventional methods, [6] and [7]. In addition, the algorithm obtains similar performance with manual method with less than 5% of the measurement error.

• Journal of the Optical Society of Korea
• /
• v.18 no.5
• /
• pp.523-530
• /
• 2014

Machine material and structural strain are critical factors for appraising mechanical properties and safety. Particularly in three and four-point bending tests, which appraise the deflection and flexural strain of an object due to external force, measurements are made by the crosshead movement or deflection meter of a universal testing machine. The Digital Image Correlation (DIC) method is one of the non-contact measurement methods. It uses the image analyzing method that compares the reference image with the deformed image for measuring the displacement and strain of the objects caused by external force. Accordingly, the advantage of this method is that the object's surface roughness, shape, and temperature have little influence. However, its disadvantage is that it requires extensive time to compare the reference image with the deformed image for measuring the displacement and strain. In this study, an algorithm is developed for DIC that can improve the speed of image analysis for measuring the deflection and strain of an object caused by a three-point bending load. To implement this algorithm for improving the speed of image analysis, LabVIEW 2010 was used. Furthermore, to evaluate the accuracy of the developed fast correlation algorithm, the deflection of an aluminum specimen under a three-point bending load was measured by using the universal test machine and DIC measurement system.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.1
• /
• pp.142-149
• /
• 2011

This paper presents a new state of charge(SOC) estimation of large capacity of Li-ion battery (LIB) based on the multiple model adaptive estimation(MMAE) method. We first introduce an equivalent circuit model of LIB. The relationship between the terminal voltage and the open circuit voltage(OCV) is nonlinear and may vary depending on the changes of temperature and C-rate. In this paper, such behaviors are described as a set of multiple linear time invariant impedance models. Each model is identified at a temperature and a C-rate. These model set must be obtained a priori for a given LIB. It is shown that most of impedances can be modeled by first-order and second-order transfer functions. For the real time estimation, we transform the continuous time models into difference equations. Subsequently, we construct the model banks in the manner that each bank consists of four adjacent models. When an operating point of cell temperature and current is given, the corresponding model bank is directly determined so that it is included in the interval generated by four operating points of the model bank. The MMAE of SOC at an arbitrary operating point (T $^{\circ}C$, $I_{bat}$[A]) is performed by calculating a linear combination of voltage drops, which are obtained by four models of the selected model bank. The demonstration of the proposed method is shown through simulations using DUALFOIL.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.1
• /
• pp.100-109
• /
• 2017

This paper proposes performance improvement schemes for sensorless PMSM control drive using a four-switch three-phase inverter (so-called B4 inverter). In the proposed scheme, the back-EMF estimation-based sensorless control algorithm is used to control the brushless PMSM without position sensors. In order to have stable operation, this paper presents a gain adjustment scheme that compensates the reduction of stable sensorless operation range as long as the rotor speed increases. In B4 topology, the center point of dc-link capacitors is connected to 3-phase load, and it is prone to have the load current distortion. Hence, to mitigate this problem, a distortion compensation scheme by modifying voltage commands using measured dc-link potentials is proposed in this paper. The validity of the proposed method is evaluated by simulations and experiments.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.11b
• /
• pp.183-195
• /
• 2000

Slopes near a dam body can be categorized into 4 groups, such as right and left abutment slopes, reservoir slopes, slopes along the access road and slopes along the relocated road. For each of the geological investigation, the design standards, the evaluation methods of safety and the maintenance methods, both abutment slopes in the four dams have different characteristics from the conventional cut slopes in that they can severely affect the dam safety. From this point of view this study compares and analyzes the geological investigation methods, the status of design and construction, evaluation method of safety, and monitoring & maintaining methods for four major dams in Korea, such as Soyanggang dam, 'Andong dam, Chungju dam and Boryong dam.

• Journal of the Korean Applied Science and Technology
• /
• v.6 no.1
• /
• pp.21-26
• /
• 1989

Four fatty acid vinyl esters were synthesized by transesterification between vinyl acetate and lauric acid, myristic acid, palmitic acid, stearic acid, respectively. Fatty acid vinyl ester oligomers were prepared from polymerization of four fatty acid vinyl esters in the presence of potassium persulfate in methanol. The ${\alpha}-sulfonation$ of these four fatty acid vinyl ester oligomer were carried by direct addition of sulfur trioxide. Especially, molecular weights of sodium ${\alpha}-sulfo$ fatty acid vinyl ester oligomers were measured by boiling point method.

• Industrial Engineering and Management Systems
• /
• v.11 no.1
• /
• pp.11-17
• /
• 2012

Along with the recent trend toward increasing variety and shorter life of products in the market, evaluation of risk for economic investment alternatives is of practical importance in manufacturing companies. This paper assumes that each alternative is composed of demand volume and unit sales price as income factors, and unit variable cost and fixed cost as expense factors. The paper assumes that these four factors move worse from the originally expected values, toward the direction of decreasing profit. Values of these four factors are also assumed to fluctuate from year to year over the entire multi-period. By applying the analysis of the breakeven points to each of the four factors, safer area against these changes is represented on the two dimensional domain called normalized total-cost unit-cost domain. A practical numerical example is analyzed to verify the validity of the proposed method.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.9 s.180
• /
• pp.2313-2318
• /
• 2000

The method of photoelasticity allows one to obtain principal stress differences and principal stress directions in a photoelastic model. In the classical approach, the photoelastic parameters are measured manually point by point. This is time consuming and requires skill in the identification and measurement of photoelastic data. Fringe phase shifting method has been recently developed and widely used to measure and analyze fringe data in photo-mechanics. This paper presents the test results of photoelastic fringe phase shifting method for the stress analysis of a curved beam plate. The technique used here requires four phase stepped photoelastic images obtained from a circular polariscope by rotating the analyzer at 0˚, 45˚, 90˚ and 135˚. Experimental results are compared with those of ANSYS and calculated by the simple beam theory. Good agreement among the results can be observed.