• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.3
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• pp.232-239
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• 2013

This paper proposes an improved stator flux estimator through ensuring conventional PLPF to act as a pure integrator for sensorless control of induction motors. Conventional PLPF uses the estimated synchronous speed as a cut-off frequency and has the gain and phase compensators. The gain and phase compensators are determined on the assumption that the estimated synchronous angular speed is coincident with the real speed. Therefore, if the synchronous angular speed is not same as the real speed, the gain and phase compensation will not be appropriate. To overcome the problem of conventional PLPF, this paper analyzes the relationship between the synchronous speed error and the phase lag error of the stator flux. Based on the analysis, this paper proposes the synchronous speed error compensation scheme. To achieve a start-up without speed sensor, the current model is used as the stator flux estimator at the standstill. When the motor starts up, the current model should be switched into the voltage model. So a stable transition between the voltage model and the current model is required. This paper proposes the simple transition method which determines the initial values of the voltage model and the current model at the transition moment. The validity of the proposed schemes is proved through the simulation results and the experimental results.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.8
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• pp.619-630
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• 2003

We present a method of runtime configuration scheduling in reconfigurable SoC design. As a model of computation, we use a popular formal model of computation, hierarchical FSM (HFSM) with synchronous dataflow (SDF) model, in short, HFSM-SDF model. In reconfigurable SoC design with HFSM-SDF model, the problem of configuration scheduling becomes challenging due to the dynamic behavior of the system such as concurrent execution of state transitions (by AND relation), complex control flow (HFSM), and complex schedules of SDF actor firing. This makes it hard to hide configuration latency efficiently with compile-time static configuration scheduling. To resolve the problem, it is necessary to know the exact order of required configurations during runtime and to perform runtime configuration scheduling. To obtain the exact order of configurations, we exploit the inherent property of HFSM-SDF that the execution order of SDF actors can be determined before executing the state transition of top FSM. After obtaining the order information and storing it in the ready configuration queue (ready CQ), we execute the state transition. During the execution, whenever there is FPGA resource available, a new configuration is selected from the ready CQ and fetched by the runtime configuration scheduler. We applied the method to an MPEG4 decoder and IS95 design and obtained up to 21.8% improvement in system runtime with a negligible overhead of memory usage.

• Journal of Korean Academy of Nursing Administration
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• v.4 no.1
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• pp.129-150
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• 1998

The purpose of this study was to exame the effect of the planned indoctrination program on the role transition of new graduate nurses in one educational hospital located in Seoul. The planned in doctrination program was a 1-month program and consisted of 3 days induction and 22 days orientation- socialization. The simulated control group pretest-posttest research was designed for this study. One hundred and twenty subjects were selected from the new graduate nurses who were employed by the Seoul National Univerty Hospital. Sixty of them were assigned to the pretest, and the rest to the posttest. To collect the data on role transition, the researcher developed the instrument, measuring 3 differert areas : inducction, orientation, and socialization. The reliability of the instrument were induction area's Chronbach ${\alpha}$ .8291, orientation area's Chronbach ${\alpha}$ .9809, and soialization area's Chronbach ${\alpha}$ .8524. The data were collected from Aprial to October 1995 at three different times: (1) immediately before indoctrination program began, (2) immediately after the program ended, and (3) 2 months after the program ended. In addition to the self-report of the subjects, their superiors filled out the same instrument on role transition to compare the scores between the subjects and their superiors at 2 months after the program. T-test was utilized to test differences between the means of pre- and post-tests. The result of this study are as follows : 1. There was a significant difference in the mean scores between before and immediately after the indoctrination program (t=-12.65, P=.000). There were significant differences in all 3 areas of role transition. 2. There was a significant difference in the mean scores between immediately after and 2 months after the program (t=-2.91, P=.004), Among 3 areas of role transition, however, only in the orientation area was there significant difference (t=-3.26, P=.001). 3. There was no significant difference in total mean scores between subjects' self-report and their superiors' report 2 months after the program ended (t =.97, p= .335). Among 3 different areas, however, there was a significant difference in the induction area (t=2.41, P=.018). 4. There was significant difference in mean scores between the group Of 3-year diploma and 4-year bachelor's degree only at pretest (t=-2.56, P= .013), but not at two posttests (t=-1.08, P=.250: t=-.34, P=.733). In conclusion, the planned indoctrination program for new graduate nurses was proved to be effective on the role transition in the study. But the result in the study showed that the indoctrination program had not equal effect On 3 different areas of role transition. There were significant differences in the scores between after and 2 months after the program only in the orientation area. These suggest that indoctrination program should be developed more focusing on induction and socialization areas to help new graduate nurses have a high morale and enthusiasm for the organization. Also contineous program to facilitate induction and socialization might be necessary for them to have a successful role transition.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.403-406
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• 1997

This paper presents a Petri net approach for the control and monitoring of discrete event system. The proposed model is fuzzy Petri nets based on the fuzzy logic with Petri nets and the hierarchy concept. Fuzzy Petri nets have been used to model the imprecise situations which can arise within automated manufacturing system, and also the hierarchy concept allow to handle the refinement of places and transition in Petri nets model. These will form the foundation of a simulator-tool with manipulation interface for application of fuzzy Petri nets.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.476-481
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• 1991

This paper investigates the relationship between the two problems, supervisor reduction and observation function (projection) design, which arise in supervisory control of DEDS. It is shown through an example that a reduced supervisor of minimal size does not necessarily result in a maximal projection when a projection design method which uses the transition structure of a supervisor is applied. Also, if an L-realizable projection P is available and if a supervisor has a special structural feature, a cover C for supervisor reduction can be easily obtained. By investigating the control-compatibility of states of the reduced supervisor based on C, we can also check maximality of P in a simple manner.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.10-13
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• 1998

In this paper, a control strategy of the three phase ZVT inverter for ac motor drives is proposed. The topology of ZVT inverter analyzed with a description of the control conditions dependent on the load current and MSVM(Modified Space Vector Modulation). The detailed simulation results indicate that zero-voltage operation during transition of the MSVM algorithm can be achieved.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.2
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• pp.129-136
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• 2002

A single-phase inverter using a diode bridge-type resonant circuit to implement ZVT(Zero Voltage Transition) switching is presented. It Is shown that the ZACE(Zero Average Current Error) algorithm based Polarized ramptime current control can provide a suitable interface between DC link of diode bridge-type resonant circuit and the inverter. The current control algorithm is analyzed about how to design the circuit with auxiliary switch which can ZVT operation for the main power switch. The simulation and experimental results would be shown to verify the proposed current algorithm, because the main Power switch is turn on with ZVT and the hi-directional inverter is operated.

• The Journal of Korean Academic Society of Nursing Education
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• v.19 no.4
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• pp.640-647
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• 2013

Purpose: The purpose of this study was to identify the effectiveness of smoking cessation education using the transtheoretical model on the process of change, smoking temptation, decisional balance and stage change transition. Methods: A nonequivalent control group non-synchronized design was used for this study. The study population was 44 male college students in the experimental group and 66 students in the control group. Smoking cessation education was administered to the experimental group at one university. Descriptive analysis, t-test, and ANCOVA were used with the SPSS 19.0 program to analyze the data. Results: After providing a smoking cessation program, the experimental group showed significantly higher scores for self-efficacy for smoking cessation, process of change, and a lower score in decisional balance for pros of smoking and nicotine dependancy compared to the control group two weeks after the pre-test. However, no significant differences were found at four weeks after the pre-test. Conclusion: The findings indicate that this program could have a positive effect on process of change, decisional balance and stage transition for college student smokers.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.9
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• pp.642-649
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• 2006

In order to recognize a situation from a environment which provides an intelligent service, we propose state-transition based situation modeling which is suitable for a low computing power and restricted resources like embedded systems, and we designed its application to a situation-action converter(SAC)which is consist of two parts; situation detector recognized wanted situations and action generator generated various control actions. Then, we implemented a situation manager for smart scheduler service by using a SAC which is installed to a ARM processor based embedded Linux evaluation board.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.18-20
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• 2008

An electrical balance of plant(EBOP) of a 600kW molten carbonate fuelcell (MCFC) has to transit from grid-connected(GC) mode to grid-independent(GI) mode when a grid is in a fault conditions. A minimum transition time is limited by four cycle for a 600kW MCFC to ride through a grid fault. In this paper, we propose a control algorithm of a 600kW EBOP for a MCFC system. The EBOP has three operation modes, i.e., GC mode, GI mode, and grid-synchronized(GS) mode. The EBOP controls output currents in a GC mode and regulates output voltages in GI or GS mode. GS mode is defined as an interface between GC mode and GI mode to make a mode transition smooth, i.e., limitation of inrush currents, regulation of output voltages within ANSI standard. Simulations and experiments carried out to verify the effectiveness of the proposed control algorithm.