• Journal of the Korean Society of Systems Engineering
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• v.1 no.1
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• pp.20-25
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• 2005

This paper presents the general system theory and its applications to the safety analysis method that is a recent trend over the traditional event-driven model. This new model is known as STAMP(Systems Theory Accident Modeling and Process) proposed by Nancy G. Leveson in MIT. The new model has benefits o f systemic approaches concerning the system safety as a whole including the context it is in, its stimulants and outcomes, and its parts as well as the relationships among them in a holistic manner. The method consists of a hierarchical control structure, a process model, and the safety constraints governing the control. This paper demonstrates an example that contrasts the differences between the approaches of STAMP and the traditional safety models.

• Journal of Power System Engineering
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• v.21 no.4
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• pp.18-25
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• 2017

This paper deals with vibration control of a small mount with MR(Magneto-Rheological) fluid as a functional fluid mount for precision equipment of automobiles. Damping and stiffness coefficients of the mount with MR fluid are changed by variations of the applied magnetic field strength. We present the robust control scheme, based on a conventional sliding mode control theory, for the design of a stable controller that is capable of vibration control due to various disturbances such as impact and periodic excitations, and is insensitive to dynamic properties of the mount. We got stable controller by using Lyapunov stability theory. The controller is then realized by using a semi-active control condition in simulations. Chattering problem of the sliding mode control is eliminated by saturation function instead of signum function. The sliding mode control with Lyapunov stability theory is superior to passive and Sky-Hook control in performance.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.129-132
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• 2001

she purpose of this paper is to propose an approach to suppress the vibration of three-mass inertia system based on the LMI theory. and confirm its validity through simulations under the condition of parameter variation. First, the existing $H_{\infty}$ servo problem is modified to a structure to which the LMI theory can be applied by virtue of the interval model principle. By adopting this structure, we can divide given specifications fur the vibration suppression problem into $H_2$and $H_{\infty}$ performance criteria. The results of simulation for the three-mass inertia system show that the proposed design approach is quite effective.

• Asia pacific journal of information systems
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• v.12 no.1
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• pp.123-138
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• 2002

For the last two decades, there has been much research on computer abuse from the perspective of the general deterrence theory based on objectism, which covers security policy, security awareness programs, and physical security system. The traditional view offered by the general deterrence theory indicates that security policy, security awareness, and security system play a major role in preventing computer abuse. In spite of continuous organizational efforts and investments based on these systematic factors, the incidence of computer abuse in organizations is still rapidly increasing. This paper proposes another perspective-the social control theory based on subjectism-in preventing computer abuse. According to the social control theory, organizational trust, which comprises organizational attachment, commitment, involvement and norms, can prevent computer abuse by reducing insider's computer abuse. The aim of this article is to assess the role of organizational trust come from attachment, commitment, involvement, norms in preventing computer abuse. The results indicate that both organizational trust and deterrent factors are effective in preventing computer abuse.

• Research in Community and Public Health Nursing
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• v.8 no.2
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• pp.314-326
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• 1997

In Korea, the nosocomial infection control program is not well developed. This situation is created by a lack of interest from medical personnel and the medical payment system. This study identifies current problems and develops a model for nosocomial infection control. The studies of Lee & Kim(1995), Lee (1993) and SENIC project model were used to construct this model. 1. The problems of nosocomial infection control were identified as the following: dis approval by hospital authorities, lack of sources for program direction, lack of overall structure and function in the program, inadequate direct action, lack of education and training, and so on. 2. The problems are reorganized according to the 5 elements of system theory. 3. As a result, the new nosocomial infection control model was developed. The inputs of the model were the elements, resources and boundaries of nosocomial infection. With the new model, each hospital can evaluate their current programs and plan a new program for the better control of nosocomial infection.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.19-24
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• 1992

Real-time mobile robot controllers usually have been designed with an emphasis on control theory ignoring the importance of system integration. This paper demonstrates that useful mobile robots require a real time controller with a wide range of capabilities in addition to control theory. These capabilities include: path-planning, position estimation, path tracking control and wheel control. An architectural framework supporting these capabilities has been designed and implemented. Using this frame work, individual modules such as a path planner, a path tracking controller, position estimators, wheel controllers and other cruical elements have been successfully integrated into the control system for the LCAR robot which was developed as a proto-type mobile robot in our laboratory. The context of the research, the architecture, its implementation and performance results from experiments are discussed.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.425-428
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• 1998

This paper proposes a new fuzzy controller using variable structure control theory. In this paper, after the time-varying fuzzy sliding surface is designed, the fuzzy rules are defined based on the variable structure control theory. This design method makes the fuzzy controller design more structured and can guarantee the stability and robustness of the fuzzy controller and overcome the shortcoming of the variable structure system. Through computer simulation and experiment of nonlinear inverted pendulum system, this thesis demonstrate that system has the robustness against disturbance and modelling error, and the tracking performance of it is improved.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.337-341
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• 1989

This theory has fast response and low overshoot by transforming its structure and this system may have new character which did not appear in this system. The VSS system transform its structure by switching logic. Then, the state trajectory is to sliding along the switching line to the phase-plane orgin. The phase trajectory is known as the sliding mode of this controller. This paper performed position control in the theory and analysised the change in variable loads.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2088-2100
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• 1994

Considerable attention has been given to controller designs that utilize the variable structure system theory in order to achieve robust tracking performance of robotic manipulators subjected to parameter variations and extraneous disturbances. However, the theory has not had wide spread acceptance in practical control engineering community due mainly to the worry of chattering which is inherently ever-existing in the variable structure system. This paper presents a novel type of fuzzy-sliding mode controller to alleviate the chattering problem. A sliding mode controller for robust robot control is firstly synthesized with an assumption that the imposed system uncertainties satisfy matching conditions so that certain deterministic performances can parameters and control rules are obtained from a relation between predetermined sliding surfaces and representative points in the error state space. A two degree-of-freedom robotic manipulator subjected to a variable payload and a torque disturbance is considered in order to demonstrate superior tracking performance accrued from the proposed methodology.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.466-468
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• 1998

This paper designs a robust controller with improved stability of a system. Robust control theory has been developed by many researchers. The controller derived in that using robust control theory has an assumption that it will be exactly implementation. But, It is very hard because of truncation errors, D-A, A-D transformation, and finite resolution, etc. Such perturbations would make problems in the stability of the system. Recently, Keel's paper presents some examples which shows controllers based on the robust controller design method are very fragile on its own perturbation. In this paper, we try to improve the stability of the closed-loop system in which there exist perturbation in the plant as well as in the controller. The results shows that the stability is improved and the performance is still satisfied.