• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.4
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• pp.65-75
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• 2022

This study aims to forecast of Air Passenger Demand between South Korea and North Korea using the system dynamics analysis methodology that is based on the system thinking. System dynamics is not only a tool that makes the systematic thought to a model but also a computer program-based analysis methodology that mathematically models the system varying according to time variation. This study analyzed the causal relationship based on the interrelation among variables and structured them by considering various variables that affect aviation cooperation from the perspective of Air passenger demand forecasting. In addition, based on the causal relationship between variables, this study also completed the causal loop diagram that forms a feedback loop, constructed the stock-flow diagram of Inter-Korean model using Vensim program. In this study, Air passenger demand was using by the simulation variable value into System Dynamics. This study was difficult to reflect the various variables constituting the North Korea environment, and there is a limit to the occurrence of events in North Korea.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.792-798
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• 2008

Supply chain management (SCM) has been drawn increasing attention in industries and academia. The attention is mainly due to a need to integrate the multiple activities in a process network from the overall perspective under the constantly varying economic environment. While many researchers have been addressing various issues of SCM, there is not much research explicitly handling the overall dynamics of supply chain entities from PSE literature. In this two-part series paper, it is investigated how the overall supply chain processing times vary in response to the variation of individual entities using Monte Carlo simulation. Instead of figuring out the operation levels of individual entities, the overall operation time called TAT(Turn-Around-Time) is proposed as a performance indicator. An example of 7 entity-supply chain is presented to illustrate the proposed methodology.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.85-87
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• 2002

The paper describes the formulation of state matrix equations from the linearized multi-machine power system including network dynamics and the application of IEEE First Benchmark Model. The eigenvalues of IEEE First Benchmark Model are investigated not only by changing the compensation of series capacitance at no-load conditions, but also by varying the generator loading at fixed compensation of capacitance. In addition, the pure electrical self-excited mode is also examined by an eigen analysis and time domain simulation.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.72-72
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• 2000

This paper presents a methodology combining sliding mode control and fuzzy control to tune the boundary layer and input gain according to the system state. The equivalent control is designed such that the nominal system exhibits desirable dynamics, The robust control with fuzzy self-tuning is then developed to guarantee the reaching condition and reduce chattering phenomenon in the presence of parameter and disturbance uncertainties.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.211-214
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• 1997

This paper applies fuzzy self-tuning PID controller in DS/CDMA cellular system. Power control is essential in DS/CDMA to compensate for the differing received powers due to both the slowly varying long-term and fast varying short-term fading processes and co-channel interference. The controller proposed is adaptable for the variations of the system dynamics and especially for the variable time delay which exists in mobile radio systems. Accordingly the results is the smaller power control error, that is, the smaller average transmitting power of mobile compared with the conventional control schemes. Because interferences to the other mobiles are reduced, the capacity of CDMA can be increased.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2001.12a
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• pp.69-73
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• 2001

The dynamic characteristics of turning processes are complex, non-linear and time-varying. Consequently, the conventional techniques based on crisp mathematical model may not guarantee surface roughness regulation. This paper presents a fuzzy controller which can regulate surface roughness in milling process using end-mill under varying cutting condition. The fuzzy control rules are established from operator experience and expert knowledge about the process dynamics. regulation which increases productivity and tool life is achieved by adjusting feed-rate according to the variation of cutting conditions. The performance of the proposed controller is evaluated by cutting experiments in the converted CNC milling machine. The result of experiments show that the proposed fuzzy controller has a good surface roughness regulation capability in spite of the variation of cutting conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.1
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• pp.113-120
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• 1994

The dynamic characteristics of turning processes are complex, non-linear and time-varying. Consequently, the conventional techniques based on crisp mathematical model may not guarantee cutting force regulation. This paper presents a fuzzy controller which can regulate cutting force in turning process under varying cutting conditions. The fuzzy control rules are extablished from operator experience and expert knowledge about the process dynamics. Regulation which increases productivity and tool life is achieved by adjusting feedrate according to the variation of cutting conditions. The performance of the proposed controller is evaluated by cutting experiments in the converted conventional lathe. The results of experiments show that the proposed fuzzy controller has a good cutting force regulation capability in spite of the variation of cutting conditions.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.2
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• pp.81-87
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• 1996

Time delay control(TDC) law has been recently suggested as an effective control technique for nonlinear time-varying systems with uncertain dynamics and/or unpredictable disturbances. This paper focuses on the applications of the TDC algorithm to torque control of an engine system and speed control of an engine/automatic transmission system. Through the stability analysis of the engien system based on TDC, determination of the appropriate time delay and control factor is investigated. It was revealed that the size of time delay of the TDC law should be greater than that of transport delay of the system for both stability and better control performance. Simulation and experimental results for the engine torque control and engine/automatic transmission speed control systems show both relatively good command following and disturbance rejection properties. However, TDC controller shows rather slow responses when applied to the system with large transport delay.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.4
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• pp.45-52
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• 2011

In the real-field of control cases for robot manipulators, there always exists a modeling error, which results the model has the uncertainties in its parameters and/or structure. In many modem applications, digital computers are extensively used to implement control algorithms to control such systems. The discretization of the nonlinear dynamic equations of such systems results in a complicated discrete dynamic equations. Therefore, it will be difficult to design a discrete-time controller to give good tracking performances in the presence of certain uncertainties. In this paper, a discrete-time sliding mode control algorithm for nonlinear and time varying robot manipulators with uncertainties is presented. Sufficient conditions for guaranteeing the convergence of the discrete-time SMC system are derived. As example simulations, the proposed SMC algorithm is applied to a two-link robotic manipulator with unknown dynamics. The results of the simulation indicate that the developed control scheme is effective in manipulators and electro-mechanical system control.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.342-347
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• 2003

In this paper, an active vibration control of a translating tensioned string with the use of an electro-hydraulic servo mechanism at the right boundary is investigated. The dynamics of the moving strip is modeled as a string with tension by using Hamilton’s principle for the systems with changing mass. The control objective is to suppress the transverse vibrations of the strip via boundary control. A right boundary control law in the form of current input to the servo valve based upon the Lyapunov’s second method is derived. It is revealed that a time-varying boundary force and a suitable passive damping at the right boundary can successfully suppress the transverse vibrations. The exponential stability of the closed loop system is proved. The effectiveness of the control laws proposed is demonstrated via simulations.