• Journal of the Korea Society for Simulation
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• v.21 no.3
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• pp.71-78
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• 2012

This research discusses the application of the control variables to achieve a more precise estimation for the target response in queueing network simulation. The efficiency of control variable method in estimating the response depends upon how we choose a set of control variables strongly correlated with the response and how we construct a function of selected control variables. For a class of queuing network simulations, the random variables that drive the simulation are basically the service-time and routing probability random variables. Most of applications of control variable method focus on utilization of the service time random variables for constructing a controlled estimator. This research attempts to suggest a controlled estimator which uses these two kinds of random variables and explore the efficiency of these estimators in estimating the reponses for computer network system. Simulation experiments on this model show the promising results for application of routing probability control variables. We consider the applications of the routing probability control variables to various simulation models and combined control variables using information of service time and routing probability together in constructing a control variable as future researches.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.740-743
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• 1997

Reference models are used in many control algorithms for improvement of transient response characteristics. They provide desired trajectories that the plant should follow. Most control systems have bounded control inputs to avoid saturation of the plant. If we design reference models that do not account for limits of control inputs, control performance of the system may be deteriorated. In this paper, therefore, the way of determining variable reference models for TDC(time delay control) technique is proposed. The variable reference model is determined based on the information of bounded control inputs and reference inputs. This proposed method is also verified by application to the position control experiment using the BLDC motor.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.9-15
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• 2008

In this paper, we suggest PI control with a predictive controller to progress both energy saving and coefficient of performance(COP) in a variable speed refrigeration system. The capacity and superheat are controlled simultaneously and independently by an inverter and an electronic expansion valve respectively for saving energy and improving COP in the system. The refrigeration system has long dead time in superheat inherently. The dead time makes the system difficult to achieve the satisfactory quick control response, especially superheat control response. In order to solve this problem, we designed a predictive controller based on PI control to progress superheat control performance. The control performance was investigated through some experiments to verify the effectiveness of the predictive controller.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.1
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• pp.26-31
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• 1998

For the semiactive vibration control, a variable damper and proper control systems are essential. In this research, a controllable damper was designed using the MR fluids and its mechanical properties such as damping constant and response time were measured. Since the response time of the MR damper was much longer than nominal MR fluid response time, the time delay of the damper should be considered in the design of controllers. It is shown that the advanced On/Off vibration control which includes the damper time delay performs more effectively than the conventional one.

• Korean Journal of Chemical Engineering
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• v.36 no.3
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• pp.356-367
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• 2019

This work presents an advanced and systematic approach to analytically design the optimal parameters of a two parameter second-order internal model control (IMC) filter that satisfies operational constraints on the output process, the manipulated variable as well as rate of change of the manipulated variable, for a first-order plus dead time (FOPDT) process. The IMC parameters are designed to minimize a control objective function composed of the weighted sum of the error between the process variable and the set point, and the rate of change of the manipulated variable, and to satisfy the desired constraints. The feasible region of the constrained IMC control parameters was graphically analyzed, as the process parameters and the constraints varied. The resulting constrained IMC control parameters were also used to find the corresponding industrial proportional-integral controller parameters of a Smith predictor structure.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.391-395
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• 1990

A new control algorithm is developed to achieve the robust performance of the system during the overall control process. Time-varying sliding manifolds are proposed to remove the reaching phase which is one of common shortcomings of variable structure control scheme. A necessary and sufficient condition for the existence of a sliding mode on the newly proposed time-varying sliding mode on the newly proposed time-varying sliding manifolds is derived by Lyapunov's second method. The digital simulation results show that the newly proposed control algorithm is superior to the typical variable structure control algorithm with respect to the robust performance of the system. The simplicity of the proposed control algorithm encourages control engineers to implement the proposed control algorithm in many control problems.

• Journal of KSNVE
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• v.8 no.4
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• pp.683-689
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• 1998

A control algorithm for multi-stage dampers is developed based on the mode skyhook control concept, and implemented on the full vehicle system environment. The test vehicle system is equipped with the real time controller, four-stage variable dampers and sensors. The real time controller is developed using a digital signal processor(DSP), digital I/O, A/D and D/A converters. The dampers are driven by the electromagnetic actuators of less than 20 msec response time. The sensors include accelerometers, relative displacement transducers, and steering wheel rate sensors, etc. Through a series of tests in laboratory and proving ground, the performance of the semi-active suspension system is evaluated and it is shown that the vehicle dynamic characteristics is improved with the developed damping system. Futhermore, the parameter tuning methods to enhance vehicle dynamic performance are propsoed.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1987-1992
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• 2004

A Variable Structure Model Reference Adaptive Controller (VS-MRAC) using state Variables is proposed for single input multi output systems. . The structure of the switching functions is designed based on stability requirements, and global exponential stability is proved. Transient behavior is analyzed using sliding mode control and shows perfect model following at a finite time. The effect of input disturbances on stability and transients is investigated and shows preference to the conventional MRAC schemes with integral adaptation law. Sliding surfaces are independent of system parameters and therefore VS-MRAC is insensitive to system parameter variations. Simulation is presented to clear the theoretical results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.1
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• pp.65-75
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• 1996

A pilot plant, which is simplified the hot water heating control system of a large scale residential building, is used to investigate the effects of control methods and operating conditions on the system performance and to compare control characteristics. Digital variable structure controller(DVSC) and digital PI controller are implemented to control the speed of the circulating pump for the pilot plant using PC. For the DVSC, a control algorithm is suggested, which using a nonlinear sliding surface and a PID sliding surface outside and inside of output error boundary layer, respectively. Smith predictor algorithm is used for the compensation of long dead time. The suggested DVSC yields improved control performance compared with existing DVSC using linear sliding surface only. the system responses with the suggested DVSC shows good responses without overshoot for various operating conditions and robust under external disturbances compared with digital PI controller.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.755-760
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• 2013

The dynamics of the winder roller of a roll-to-roll printing system for printed electronics is a time-varying system because of the variation of the winder roller radius owing to rewinding or unwinding of the web. Therefore, an adaptive control method considering the time-variant characteristics is required for precise tension control. In this study, the variable PID gain method is applied to the actual roll-to-roll system and verified by experiments for unwinder tension control. The required value of the winder roller radius for the application of the variable PID gain is estimated from the measurement of the winder tension and winder motor torque. The simulation results as well as experimental results show that the fixed PID gain control cannot stabilize the tension of the winder roller with varying winder roller radius. On the other hand, the variable PID gain method can control the tension of the winder roller regardless of the winder roller radius.