• Journal of Power Electronics
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• 제15권3호
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• pp.660-669
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• 2015

This paper presents a control scheme with a focus on the combination of phase disposition pulse width modulation (PDPWM) and DC capacitor voltage control for a chopper-cell based modular multilevel converter (MMC) for the purpose of eliminating the time-consuming voltage sorting algorithm and complex voltage balancing regulators. In this paper, the convergence of the DC capacitor voltages within one arm is realized by charging the minimum voltage module and discharging the maximum voltage module during each switching cycle with the assistances of MAX/MIN capacitor voltage detection and PDPWM signals exchanging. The process of voltage balancing control introduces no extra switching commutation, which is helpful in reducing power loss and improving system efficiency. Additionally, the proposed control scheme also possess the merit of a simple executing procedure in application. Simulation and experimental results indicates that the MMC circuit together with the proposed method functions very well in balancing the DC capacitor voltage and improving system efficiency even under transient states.

• 제어로봇시스템학회논문지
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• 제20권2호
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• pp.163-169
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• 2014

Using the classical cascade voltage control strategy, this paper proposes an analytical solution to an MPC (Model Predictive Control) problem with a hexagonal input constraint set for the inner-loop to regulate the output voltage of the UPS (Uninterruptible Power Supply). Focus is placed on how to deal with the hexagonal input constraint set without any approximation. Following the conventional cascade voltage control strategy, the PI (Proportional-Integral) controller is used in the outer-loop in order to regulate the output voltage. The simulation results illustrate that the capacitor voltage rapidly goes to its reference in a satisfactory manner while keeping other state variables bounded under an unexpected load changes.

• 기본간호학회지
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• 제18권2호
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• pp.217-225
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• 2011

Purpose: The purpose of this study was to analyzing the relationship between perceived health status, health locus of control, self-esteem, self-efficacy and HPB in patients with multiple myeloma to identify factors influencing health promoting behavior (HPB). Methods: One hundred patients were recruited into the study. The data were collected by personal interviews using questionnaires. Descriptive statistics, Pearson's correlation coefficients and stepwise multiple regression analysis were used with SPSS program to were analyze the data. Results: There were significant relationships between self-esteem (r=.787, p<.001), self-efficacy (r=.681, p<.001), internal health locus of control (r=.557, p<.001), powerful others health locus of control (r=.517, p<.001), chance health locus of control (r=-.251, p=.012), perceived health status (r=.532, p<.001) and HPB. Significant factors in explaining HPB were self-esteem, powerful others health locus of control, self-efficacy and perceived health status and together they accounted for 71% of variance. Conclusion: The study findings indicate that self-esteem, powerful others health locus of control, self-efficacy, and perceived health status were important factors in explaining HPB in patients with multiple myeloma. As self-esteem was an important variable in HPB, health promotion program designed for this population should focus on self-esteem and these other factors to enhance effective health promotion behavior.

• Smart Structures and Systems
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• 제14권6호
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• pp.1081-1103
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• 2014

Real-time hybrid simulation (RTHS) has emerged as an important tool for testing large and complex structures with a focus on rate-dependent specimen behavior. Due to the real-time constraints, accurate dynamic control of servo-hydraulic actuators is required. These actuators are necessary to realize the desired displacements of the specimen, however they introduce unwanted dynamics into the RTHS loop. Model-based actuator control strategies are based on linearized models of the servo-hydraulic system, where the controller is taken as the model inverse to effectively cancel out the servo-hydraulic dynamics (i.e., model-based feedforward control). An accurate model of a servo-hydraulic system generally contains more poles than zeros, leading to an improper inverse (i.e., more zeros than poles). Rather than introduce additional poles to create a proper inverse controller, the higher order derivatives necessary for implementing the improper inverse can be calculated from available information. The backward-difference method is proposed as an alternative to discretize an improper continuous time model for use as a feedforward controller in RTHS. This method is flexible in that derivatives of any order can be explicitly calculated such that controllers can be developed for models of any order. Using model-based feedforward control with the backward-difference method, accurate actuator control and stable RTHS are demonstrated using a nine-story steel building model implemented with an MR damper.

• 한국정밀공학회지
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• 제22권4호
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• pp.136-143
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• 2005

Open architecture controller (OAC) is well known technology in factory automation. To better understand the requirements of OAC, authors have discussed the OAC related topics with a number of control experts who represents different segments of the machining industry. There is no common concept that is accepted or used, however, the common ideas for OAC is the control system that is hardware independent, interchangeable, and easily scalable. This paper presents summary of the understaning and requirements of OAC. Based on the requirements of OAC, authors developed the software based PC-CNC. The main focus of the PC-CNC was on the user customization capability and open interface between control networks in manufacturing system. This paper introduces the developed PC-CNC briefly. In addition to introduction of the PC-CNC, to fill the gap between end users and vendors of OAC, this paper presents two applications using OAC. One is a remote monitoring system. The OPC (Ole for Process Control) standard interface was used to monitor the status of open architecture CNC across network. The other is the remote production management module for machine tools using standard database interface.

• Child Health Nursing Research
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• 제26권3호
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• pp.357-365
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• 2020

Purpose: The aim of this study was to investigate internet addiction among middle school students and to examine the mediating effects of social support in the relationships of self-efficacy and self-control with internet addiction. Methods: The participants in the study were 119 middle school students in J city. The measurements included a self-efficacy scale, a self-control scale, a social support scale, and the Internet Addiction Scale for Youth. Data were analyzed using the independent t-test or Mann-Whitney U test, one-way analysis of variance, the Scheffé test, Pearson correlation coefficients, and multiple-regression using SPSS version 22.0. Mediation effects were analyzed by the Sobel test and Baron and Kenny's hierarchical analysis technique. Results: Significant correlations were found among self-efficacy, self-control, and internet addiction. Social support had partial mediating effects in the relationship between self-efficacy and internet addiction, as well as in the relationship between self-control and internet addition. Conclusion: In order to prevent internet addiction, the promotion of interactions among peers, which is a component of social support, is particularly important. It is also necessary to promote face-to-face activities that can strengthen relationships. The findings suggest that intensifying social support may help reduce the level of internet addiction in middle school students.

• Journal of Communications and Networks
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• 제12권5호
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• pp.499-509
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• 2010

A plethora of transmission control protocol (TCP) congestion control algorithms have been devoted to achieving the ultimate goal of high link utilization and fair bandwidth sharing in high bandwidth-delay product (HBDP) networks. We present a new insight into the TCP congestion control problem; in particular an end-to-end delay-based approach for an HBDP network. Our main focus is to design an end-to-end mechanism that can achieve the goal without the assistance of any network feedback. Without a router's aid in notifying the network load factor of a bottleneck link, we utilize goodput and throughput values in order to estimate the load factor. The obtained load factor affects the congestion window adjustment. The new protocol, which is called TCP-goodput and throughput (GT), adopts the carefully designed inversely-proportional increase multiplicative decrease window control policy. Our protocol is stable and efficient regardless of the link capacity, the number of flows, and the round-trip delay. Simulation results show that TCP-GT achieves high utilization, good fairness, small standing queue size, and no packet loss in an HBDP environment.

• 대한산업공학회지
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• 제25권1호
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• pp.87-99
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• 1999

A shop floor control system(SFCS) performs the production activities required to fill orders. In order to effectively control these activities, the autonomous agent-based heterarchical shop floor control architecture is adopted where a supervisor does not exist. In this paper, we define functional perspective of the heterarchical shop floor control using planning, scheduling, and execution modules. In particular, we focus on an execution module that can coordinate the planning and scheduling modules and a general execution module that easily can be modified to execute the other equipment. The execution module can be defined informally as a module that downloads and performs a set of scheduled tasks. The execution module is also responsible for identifying and resolving various errors whether they come from hardware or software. The purpose of this research is to identify all the execution activities and solving techniques under the assumptions of the heterarchical control architecture. And we model the execution module in object-oriented modelling technique for generalization. The execution module modeled in object-oriented concept can be adopted to the other execution module easily. This paper also proposes a classification scheme for execution activities of the heterarchical control architecture. Petri-nets are used as a unified framework for modeling and controlling execution activities. For solving the nonexistence of a supervisor, a negotiation-based solution technique is utilized.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.249-254
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• 2001

Abstract In this paper, we propose a method of cooperative control based on artifical intelligent system in distributed autonomous robotic system. In general, multi-agent behavior algorithm is simple and effective for small number of robots. And multi-robot behavior control is a simple reactive navigation strategy by combining repulsion from obstacles with attraction to a goal. However when the number of robot goes on increasing, this becomes difficult to be realized because multi-robot behavior algorithm provide on multiple constraints and goals in mobile robot navigation problems. As the solution of above problem, we propose an architecture of fuzzy system for each multi-robot speed control and fuzzy-neural network for obstacle avoidance. Here, we propose an architecture of fuzzy system for each multi-robot speed control and fuzzy-neural network for their direction to avoid obstacle. Our focus is on system of cooperative autonomous robots in environment with obstacle. For simulation, we divide experiment into two method. One method is motor schema-based formation control in previous and the other method is proposed by this paper. Simulation results are given in an obstacle environment and in an dynamic environment.

• 한국식품영양학회지
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• 제20권4호
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• pp.421-426
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• 2007

This study was carried out to investigate the properties of Kimchi made with potato as compared to Kimchi made with radish. The pH, acidity, hardness, and number of lactic acid bacteria were examined as properties of the Kimchi to determine the suitability of adding the potato and with focus on the possible duration of storage. First in the case of pH, the storage duration at pH $4.2{\sim}4.3$, which is the state for optimal tasting Kimchi, was approximately 10days in the control group, while that of the experimental group was 10 to 16 days, and thus, longer than the control. Second in the case of acidity, representing the maturity of Kimchi, we examined the time it took to reach 0.6% acidity, in which the experimental group took more longer time than the control. Although the experimental group was slower to mature than the control, the period for keeping at the proper pH was longer than that of the control group. Thirdly, in the case of hardness, which relates to softening, the experimental group had remarkably high values. This suggests that the Kimchi in the experimental group had a more rigid texture and more difficultly softening than the control group. Lastly in the case of the number of lactic acid bacteria, which closely relates to the process of fermentation, there were no significant differences. In conclusion, these results indicate that adding potato to Kimchi can extend its storage period.