• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.151.1-151
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• 2001

This paper establishes some integral equalities formulated by zeros located in the convergence region of Laplace transformable function. Using the definition of Laplace transform, it is shown that time-domain integral equalities have to be satisfied by the function, and those can be applied to understanding of the fundamental limitations of the control system represented by the transfer function, which has been Laplace transform. In the unity-feedback control scheme, another integral equality is also derived on the output response of the system with open-loop poles and zeros located in the convergence region.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.240-243
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• 2001

This paper presents the digital controller using variable gain for single-phase power factor correction (PFC) converter. Generally, the gain of inner current control loop in single-stage PFC converter has a constant magnitude. This is why input current is distorted under low input voltage. In particular, a digital controller has more time delay than an analog controller which degrades characteristics of control loop. So, it causes the problem that the gain of current control loop isn't increased enough. In addition, the oscillation happens in the peak value of the input voltage open loop PFC system gain changes according to ac input voltage. These aspects make the design of the digital PFC controller difficult. In this paper, the improved digital control method for single-phase power factor converter is presented. The variable gain according to input voltage and input current help to improve current shape. The 800W converter is manufactured to verify the proposed control method.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.629-632
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• 2003

Piezo actuators are mainly used in precision position control system because of their high position resolution. Although there have been many approaches in open loop control of this, those method turn out to be not effective in precision control due to hysteresis and creep. To overcome the problems, closed loop PI control method is used in commercial products. However, it is very difficult to obtain fast response with conventional PI control although piezo actuator has fast response. In this paper, we propose a fuzzy PI control method with the proposed fuzzy PI controller, we obtains faster settling response over the conventional PI controller. We verify the effectiveness of the proposed method with experimental results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.279-286
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• 2010

In this paper, we provide a robust track-following controller design method for the stable coarse seek control. Due to the inaccurate velocity control during a coarse seek, the shake of fine actuator is generated and thus a gain-up track-following control is required to complete stably the coarse seek. To this end, a loop gain adjustment algorithm is introduced to estimate accurately the shake of fine actuator. A weighting function can be properly selected from a minimum tracking gain-up open-loop gain, calculated from the estimated shake quantity of fine actuator. A robust tracking gain-up controller is designed by considering a robust $H_{\infty}$ control problem using the weighting function. The proposed design method is applied to the coarse seek control system of an optical rewritable drive and is evaluated through the experimental results.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.187-189
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• 2000

In this paper, QFT robust control strategy is proposed to improve stability of power systems in the presence of parametric uncertainty. The basic idea in QFT is to convert design specifications of a closed loop system and plant uncertainties into robust stability and performance bounds on the open loop transmission of the nominal system and then to design a controller by using the gain-phase loop sharing technique. The robustness of the QFT controller has been investigated on a single machine infinite bus model by nonlinear simulations.

• International Journal of Control, Automation, and Systems
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• v.5 no.3
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• pp.223-233
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• 2007

Crane payloads frequently swing with large amplitude motion that degrades safety and throughput. Open-loop methods have addressed this problem, but are not effective for disturbances. Closed-loop methods have also been used, but generally require the speed of the driving motors to be precisely controlled. This paper develops a feedback control method for controlling motors to cancel the measured payload oscillations by intelligently timing the ensuing on and off motor commands. The effectiveness of the oscillation suppression scheme is experimentally verified on an industrial bridge crane.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1337-1342
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• 1990

This paper deals with control system design strategy for electrolmaginetic suspension (E.M.S.) system. For a successful control of E.M.S. system, the nature of E.M.S. system is deeply studied in the view point of non-linear, open-loop unstable, time-varying, non-minimum phase system. To find a special control treatment for E.M.S. system, analyses and simulations for various models are carried out. As one of the successful candidates, adaptive control concept is introduced and sample hardware system using digital signal processor is implemented.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.4
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• pp.299-305
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• 2013

The complexity and severe nonlinearity of multi-machine power systems make it difficult to design a control input for voltage regulation using modern control theory. This paper presents a model-based PID control scheme for the regulation of the bus voltage to a desired value. To this end, a fourth-order linear system is constructed using input and output data obtained using the TSAT (Transient Security Assessment Tool); the input is assumed to be applied to the grid through the STATCOM (STATic synchronous COMpensator) and the output from the grid is a bus voltage. On the basis of the model, it is identified as to which open-loop poles of the system make the response to a step input oscillatory. To reduce this oscillatory response effectively, a model-based PID control is designed in such a way that the oscillatory poles are no longer problematic in the closed loop. Simulation results show that the proposed PID control dampens the response effectively.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.10a
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• pp.187-190
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• 1998

The values of physical components of the plants and controllers as well as the relevant environmental conditions change in time, thus the output performance can be deteriorated during the operating span of the system. Naturally the duty of calibration or the prevention of performance deterioration due to excessive component sensitivity should be provided to the control system. The proposed controller, whenever necessary, measures the open-loop and close-loop characteristics, and then calculates the offset and sensor gain correction values based on the prepared standard measurements It is applied to the control of a flexible link system with the gain and offset calibration problems in the light sensor module for position to show the applicability. In this paper, we propose a digital controller which has the capability of calibration gain and offset adjustment using fuzzy methods.

• Smart Structures and Systems
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• v.14 no.4
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• pp.643-658
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• 2014

This paper presents the design, modelling and, simulation and experimental results of a shape memory alloy (SMA) actuator based critical motion control application. Dynamic performance of SMA and its ability in replacing servo motor is studied for which the famous open loop unstable balancing ball and beam system direct driven by antagonistic SMA is designed and developed. Simulation uses the mathematical model of ball and beam structure derived from the first principles and model estimated for the SMA actuator by system identification. A PID based cascade control system consisting of two loops is designed and control of ball trajectory for various target positions with settling time as control parameter is verified experimentally. The results demonstrate the performance of SMA for a complicated i.e., under actuated, highly nonlinear unstable system, and thereby it's dynamic behaviour. Control strategies bring out the effectiveness of the actuator and its possible application to much more complex applications such as in aerospace control and robotics.