• International Journal of Automotive Technology
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• v.8 no.4
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• pp.429-436
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• 2007

In this study, we improved control performance of an EMV (electromechanical valve) system using a PM/EM (permanent magnet/electromagnet) hybrid EMA (electromagnetic actuator) and showed the feasibilities of both soft landing and fast transition of the EMV system using a simple PID control. The conventional EMV systems using only EM show significant nonlinear characteristics. Therefore, it is very difficult to control the valve position and several complex control schemes are used. This paper focused on the control performance improvement using a PM/EM hybrid actuator. In particular, a PM is used as a key design parameter such as a bias current of a magnetic bearing in order to improve the linear characteristic of the actuator, although most PM/EM hybrid actuators use a PM as a power saver during valve-open and -closed states. First, a FE (finite element) analysis was performed to confirm its linear static force characteristics. Then, both a test rig and a valve control system were built in order to prove experimentally the control performance improvement of the actuator. Finally, feasibilities of both soft landing and fast transition of the system were shown experimentally through gain-scheduled PID (proportional derivative integral) control.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.7
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• pp.539-546
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• 2002

This paper presents a new direct seek control scheme that provides fast data access capability and robust performance for high-speed rotational optical disk drives (ODD). When a disk is rotating at a high speed to obtain fast data transfer in ODD, the magnitude and frequency of velocity disturbance caused by eccentric rotation of the disk increase in proportion to the rotational speed of the disk. Such disturbances make it almost impossible for the conventional seek control scheme to achieve stable and satisfactory seek performance. We analyze the problems that may arise when the conventional seek control scheme is applied to the high-speed rotational ODD and propose a new direct seek control scheme that will solve such problems. In the proposed scheme, a seek control system is designed such that its performance is guaranteed for a set of plants with parameter perturbations. The performance of the proposed seek control scheme is shown by experiments using a high-speed rotational ODD.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.10
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• pp.1978-1983
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• 2011

BLDC motor is used in a wide variety of industrial and servo applications. Its features and advantages mainly consist in high value of torque/inertia ratio, high efficiency with speed range and high dynamic performance. This paper deals with the speed control of a trapezoidal type brushless DC motor using Fuzzy PI controller. The conventional PI controller has been widely used in industrial applications. If we select a optimal PI control gain, the PI controller shows very good control performance. But it is very difficult to find the optimal PI control gain. Fuzzy control does not need any model of plant and is basically adaptive and gives robust performance for plant parameter variation. Therefore the combinations of conventional PI controller and fuzzy controller seem to be very effective. This paper deals with PI controller with 4-rule based fuzzy controller. The proposed fuzzy PI controller increases the control performance of the conventional PI controller. Simulation and experimental results show that fuzzy PI controller has a good robustness regarding the improper tuned PI controller.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.498-501
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• 2005

This paper deals with the design and evaluation of the robust controller for a synchronous generator excitation system to improve the steady state and transient stability. The nonlinear characteristics of the system is treated as model uncertainties, and then the robust control techniques are introduced into the power system stability design to take into account these uncertainties at the controller design stage. The performance of the designed controller is examined by extensive non-linear time domain simulation. It is shown that the performance of the robust controller is superior to that of the conventional PI controller. This paper also proposes an improved digital exciter control system for a synchronized generator using a digitally designed controller with database. Results show that the proposed control system manifests excellent control performance compared to existing control systems. It has also been confirmed that it is easy for the proposed control system to implement digital control.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.8 s.101
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• pp.911-917
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• 2005

There were many attempts to reduce noise behind the noise barrier using active control techniques. Omoto(1993) Shao(1997) and Yang(2001) tried to actively control the diffracted noise behind the barrier and main concerns were about the arrangement methods for the control sources. Baek (2004) tried to get better results using the simulated annealing method and the sequential searching technique. The main goal of this study is to develop and compare the performance of several optimization techniques including those mentioned above, hybrid version of simulated annealing and genetic algorithm for the optimal control source positions of active noise barrier system. The simulation results show fairly similar performance lot the small size of searching problem. However, as the number of control sources are increased, the performance of simulated annealing algorithm and genetic algorithm are better than the others. Simulations are also made to show the performance of the selected optimal control source positions not only at the receiver position but at the surrounding volume of the receiver position and plotted the noise reduction level in 3-D.

• Korean Journal of Adult Nursing
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• v.24 no.3
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• pp.232-243
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• 2012

Purpose: This study was to identify the level of knowledge and performances on evidence-based infection control and influencing factors on performance among nurses in intensive care unit. Methods: A descriptive cross-sectional survey design was used. Two hundred thirty-nine nurses at intensive care units were conveniently recruited from seven hospitals located in Seoul and Kyounggi province. Data were collected with a questionnaire survey about evidence-based infection control. Data were analyzed using SPSS/WIN 17.0 program. Results: Both level of knowledge (mean 9.15 out of 19) on preventing ventilator-associated pneumonia and central venous catheter induced bloodstream infection, and performance on evidence-based infection control (1.94 out of 4) were moderate. Performance of evidence-based practice for infection control was related to reading research articles regularly, professional satisfaction, and taken education course. Conclusion: These results indicate that systematic and organizational strategies for enhancing evidence-based infection control are needed to improve quality of intensive nursing care.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.60-67
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• 2003

The goal of this paper is to improve EMC performance of circuit breaker. Circuit breaker and control cubicle are interconnected by multi control cable. Also many control cables are laid on each apparatus. These control cables are directly connected by electronic components. So control cables are very important to improve EMC performance of circuit breaker. This paper suggests installing a ground conductor in parallel(PGC) to control cables. Also this paper suggests using shielding cables as secondary cables of voltage transformer in circuit breakers, and grounding both ends of shielding. After applying suggested methods, we verified EMC performance of circuit breaker is improved.

• Nuclear Engineering and Technology
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• v.39 no.1
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• pp.63-74
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• 2007

In this paper, a reconfigurable controller consisting of a normal controller and a standby controller is designed to control the thermoelectric (TE) power in the SP-100 space reactor. The normal controller uses a model predictive control (MPC) method where the future TE power is predicted by using support vector regression. A genetic algorithm that can effectively accomplish multiple objectives is used to optimize the normal controller. The performance of the normal controller depends on the capability of predicting the future TE power. Therefore, if the prediction performance is degraded, the proportional-integral (PI) controller of the standby controller begins to work instead of the normal controller. Performance deterioration is detected by a sequential probability ratio test (SPRT). A lumped parameter simulation model of the SP-100 nuclear space reactor is used to verify the proposed reconfigurable controller. The results of numerical simulations to assess the performance of the proposed controller show that the TE generator power level controlled by the proposed reconfigurable controller could track the target power level effectively, satisfying all control constraints. Furthermore, the normal controller is automatically switched to the standby controller when the performance of the normal controller degrades.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.246-254
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• 2015

This study was conducted as a descriptive study with the aim of identifying the effects of safety knowledge and safety control on early childhood teachers' safety performance. Data collection for the study was carried out between October $10^{th}$ and $30^{th}$, 2014 by surveying 187 early childhood teachers working in child day care center and kindergarten located in P, K, & Y city. Measures were subjects' safety knowledge, safety control, and safety performance. For the analysis of the data, the statistical methods of frequency, mean and standard deviation, t-test, ANOVA, Pearson's correlation coefficients, and multiple regression analysis were employed. When the category of safety performance was analyzed by general features, marital status, educational career, and degree of assistance of safety education, there were significant differences. Safety performance correlated positively with safety knowledge and safety control. Factors affecting early childhood teachers' safety performance were identified in the order of safety knowledge and safety control and the explanatory power was 60.0%. The findings of the study indicate that in order to increase early childhood teachers' safety performance, their safety knowledge and safety control have to be enhanced.

• Journal of muscle and joint health
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• v.26 no.3
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• pp.241-250
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• 2019

Purpose: This study was conducted to identify influencing factors on the performance of healthcare-associated infection control and microbiological hand contamination among caregivers at a tertiary hospital. Methods: The participants of this study were 59 caregivers woring at a tertiary hospital. Data were collected from July 1 to 30, 2018. Data were analyzed using descriptive statistics, t-test, ANOVA, Scheffé test, Pearson's correlation coefficients and stepwise multiple regression by SPSS 23.0 Win program. Results: Multiple regression analysis revealed that factors influencing performance of healthcare-associated infection control were awareness (β=.63, p<.001) and the experience of infection-related education (β=-3.40, p=.042). Regression equations describing the performance of healthcare-related infection control were found to be appropriate (F=27.29, p<.001) and accounted for 68% of variance. Factors affecting the degree of microbiological hand contamination were work experience (β=-0.28, p=.026) and healthcare-related infection performance (β=-0.28, p=.029). A regression equation describing the microbiological hand contamination was appropriate (F=6.10, p=.004) and accounted for 42% of variance. Conclusion: The findings of this study suggest that it is necessary to increase performance of healthcare-associated infection control by caregivers. Also, educations for preventing healthcare-associated infection and guidelines for increasing compliance with healthcare-associated infection control are recommended to improve performance of healthcare-associated infection control.