• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.697-702
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• 2016

To control permanent magnet synchronous motors smoothly, it is important to know the exact parameter values of the stator resistance, various inductances, and the flux linkage of the permanent magnet. In practice, these parameters vary due to a variable operating point, temperature change, or a fault. This paper proposes a MRAS (Model Reference Adaptive System) based parameter estimator and adaptive control scheme. Owing to the non-linearity of the system equation with respect to these parameters, although many schemes proposed previously assumed that some parameters are known, all the parameters were assumed to be unknown. The simulation results revealed the effectiveness of the proposed algorithm.

• International conference on construction engineering and project management
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• 2011.02a
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• pp.382-388
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• 2011

Being aware of the risk in advance necessitates intricate processes but is feasible. Although previous studies have demonstrated high accuracy, their performance still leaves room for improvement. A self-organizing feature map (SOM) based neurofuzzy model is developed in this study to provide another alternative for forecasting corporate financial distress. The model is designed to yield high prediction accuracy, as well as reference rules for evaluating corporate financial status. As a database, the study collects all financial reports from listed construction companies during the latest decade, resulting in over 1000 effective samples. The proportion of "failed" and "non-failed" companies is approximately 1:2. Each financial report is comprised of 25 ratios which are set as the input variable s. The proposed model integrates the concepts of pattern classification, fuzzy modeling and SOM-based optimization to predict corporate financial distress. The results exhibit a high accuracy rate at 85.1%. This model outperforms previous tools. A total of 97 rules are extracted from the proposed model which can be also used as reference for construction practitioners. Users may easily identify their corporate financial status by using these rules.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1883-1887
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• 1991

Identification theory for linear discrete system has been presented by a great many reference, but research works for identification of continuous-time system are less than preceding identification. In fact, a great man), systems for engineering are continuous-time systems, hence, research for identification of continuous-time system has important meaning. This paper offers the following results: 1. Corresponding relations for the parameters of continuous-time model and discrete model may be shown, when single input-output system has general characteristic roots. 2. To do identification of single variable continuity linear system with stability constraints from samples of input-output data, it is necessary to use optimization with stability constraints. 3. Main results of this paper may be explained by a simple example.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2399-2410
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• 2017

In this paper, a linear matrix inequality-based sampled-data fuzzy observer design method is proposed based on the exact discretization approach. In the proposed design technique, a numerically relaxed observer design condition is obtained by using the discrete-time fuzzy Lyapunov function. Unlike the existing studies, the designed observer is robust to the uncertain premise variable because the fuzzy observer is designed under the imperfect premise matching condition, in which the membership functions of the system and observer are mismatched. In addition, we apply the proposed method to the state estimation problem of the attitude and heading reference system (AHRS). To do this, we derive a Takagi-Sugeno fuzzy model for the AHRS system, and validate the proposed method through the hardware experiment.

• Nuclear Engineering and Technology
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• v.39 no.4
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• pp.313-326
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• 2007

In this paper, an algorithm to reconstruct two orthogonal images into a three-dimensional image is developed in order to measure the bubble size and volume in a two-phase boiling flow. The central-active contour model originally proposed by P. $Szczypi\'{n}ski$ and P. Strumillo is modified to reduce the dependence on the initial reference point and to increase the contour stability. The modified model is then applied to the algorithm to extract the object boundary. This improved central contour model could be applied to obscure objects using a variable threshold value. The extracted boundaries from each image are merged into a three-dimensional image through the developed algorithm. It is shown that the object reconstructed using the developed algorithm is very similar or identical to the real object. Various values such as volume and surface area are calculated for the reconstructed images and the developed algorithm is qualitatively verified using real images from rubber clay experiments and quantitatively verified by simulation using imaginary images. Finally, the developed algorithm is applied to measure the size and volume of vapor bubbles condensing in a subcooled boiling flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.4
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• pp.159-166
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• 2017

The growing global interest in energy saving is particularly evident in the building sector. The transmitted solar irradiance is an important input in the prediction of the building-energy load, but it is a value that is difficult to measure. In this paper, a calculation method, for which the total horizontal irradiance that can be easily measured is employed, for the measurement of the transmitted solar irradiance through windows is proposed. The method includes a direct and diffuse split model and a variable-transmittance model. The results of the proposed calculation model are compared with the TRNSYS-simulation results at each stage for the purpose of validation. The final results show that the CVRMSE over the year between the proposed model and the reference is less than 30 %, whereby the ASHRAE guideline was achieved.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.403-405
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• 1999

The model reference adaptive control(MRAC) algorithm is applied to the speed control of an inverter driven permanent magnet brushless do motor MRAC is compared to a standard PI controller. Applying this algorithm has also been proved by simulations that quick speed response without over-shoot could be obtained for the motor system with variable parameters. Simulation results show that the adaptive controller is superior to the PI controller.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.241-244
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• 2006

In this paper, we suggest the high efficient control method based on general PI control law to control the refrigeration system of the ship effectively. In the variable speed refrigeration system, the capacity and the superheat are controlled by inverters and electronic expansion valves respectively for saving energy and improving cost performance. Thus, we propose decoupling model to eliminate the interfering at first. Next, we design PI controller to control capacity and superheat independently. Finally the control performance was investigated through some experiments. The experiments results show that the PI control design can obtain good control performance deal with the varied control reference and thermal load.

• East Asian mathematical journal
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• v.33 no.4
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• pp.467-482
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• 2017

This paper studies the relationship between the college entrance examination scores and college mathematics achievements of the freshman, who are the students of college of technology and management in Yanbian University, by employing statistical analysis. First of all, we start from the correlation analysis of the majors and regions of students. Secondly, with gender and region as the classification, we divide the sample into two parts and test the mean significance, and we find that not only different gender but also different region have significant differences to college mathematics achievements. Thirdly, we use the college entrance examination scores as independent variable, and college mathematics achievement as the dependent variable to establish regression model. The model provides a realistic basis for the education department of our school, and provides reference value for the other major research.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.3
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• pp.29-37
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• 2001

The purpose of this study is to determine the suitable illuminance model of an urban neighborhood park. To this end, 1 dependent variable and 11 independent variables were set, and multiple regression analysis was applied to find correlation between variables and the model. The results of this study are as follows; 1) Among 11 independent variables abstracted to study suitable illuminance model of an urban neighborhood park, as a result of analysis on correlation between suitable illuminance of a dependent variable and activity space by using dummy variables, activity type and illuminance by spaces the suitable illuminance required for an urban neighborhood park was much influenced by activity type, and the fact that the activity was not limited to a specific space. 2) As a result of multiple regression analysis, independent variables influencing the suitable illuminance model of an urban neighborhood park were activity space, illuminance by spaces, seated activity, standing activity, and sporting activity. And, for relative contribution of independent variables to suitable illuminance, activity with sporting showed an importance 22 times higher than seated activity. When the central square(Sp_1) of activity spaces was set to reference category using dummy variables, it showed a contribution 52 times higher than sorting space(Sp_7) and the central square as the most important variable. 3) It was analyzed that suitable illuminance of an urban neighborhood part was most influenced by sporting activity but the relative contribution of a sporting space where activity with sporting occurs was least in view of the function of the space. Very high illuminance is required to accept high activity, and if illuminance at a certain space becomes too high, it may influence the illuminance of other spaces, and may consequently have a negative effect on the suitable illuminance of an urban neighborhood park. The results of this study were mainly for teenagers and young adults in their twenties, so further concrete studies which consider gender and a wider age range are needed in the future. Based on subsequent study, suitable illuminance by spaces shall be suggested.