• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1389-1399
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• 2013

A discrete controller is designed for low power dc-dc switched mode power supplies. The approach is based on time domain and the control loop continuously and concurrently tunes the compensator parameters to meet the converter specifications. A digital state feedback control combined with the load estimator provides a complete compensation, which further improves the dynamic performance of the closed loop system. Simulation of digitally controlled Buck converter is performed with MATLAB/Simulink. Experimental results are given to demonstrate the effectiveness of the controller using LabVIEW with a data acquisition card (model DAQ Pad - 6009).

• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1608-1615
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• 2003

This paper studies on the linearization of a looper system in hot strip mills, that plays an important role in regulating a strip tension or a strip width. Nonlinear dynamic equations of the looper system are analytically linearized by a static feedback linearization algorithm with a compensator. The proposed linear model of the looper is validated by a comparison with a linear model using Taylor's series. It is shown that the linear model by static feedback well describes nonlinearities of the looper system than one using Taylor's series. Furthermore, it is shown from the design of an ILQ controller that the linear model by static feedback is very useful in designing a linear controller of the looper system.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.2
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• pp.140-147
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• 2008

This paper describes a Neural Network based PD control scheme for motion control of pneumatic servo cylinder. Pneumatic systems have inherent nonlinearities such as compressibility of air and nonlinear frictions present in cylinder. The conventional linear controller is limited in some applications where the affection of nonlinear factor is dominant. A self-excited oscillation method is applied to derive the dynamic design parameters of linear model. Based on the parameters thus identified, a PD feedback compensator is designed first and then a neural network is incorporated. The experiments of a trajectory tracking control using the proposed control scheme are performed and a significant reduction in tracking error is achieved by comparing with those of a PD control.

• Journal of KSNVE
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• v.5 no.3
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• pp.403-411
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• 1995

Square beam type piezoelectric vibrating gyro is developed for the measurement of angular velocity, which is compact, small in size and mass- producible. It features that three pieces of piezoelectric ceramics and bonded onto one face of equilateral square bar type gyro head. Two of them are used as sentuators which drive the gyro head and measure Coriolis force. The third piece is used for the feedback signal in order to resonate the gyro head and measure Coriolis force. The third piece is used for the feedback signal in order to resonate the gyro head with its fundamental natural frequency. Matching two fundamental natural frequencies in the gyro head with its driving frequency is found critical in the design of vibration gyro. Calibration results show that the vibrating gyro developed has the dynamic characteristics of first-order system within the frequency range of interest, which can be easily compensated by a lead compensator.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.966-972
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• 2007

This paper presents position control of nonlinear three-dimensional crane systems using neural network approach. Such crane system generally includes very complicated characteristic dynamics and mechanical framework such that its mathematical model is expressed by strong nonlinearity. This leads difficulty in control design for the systems. We linearize the nonlinear system model to construct PID control applying well-known linear control theory and then neural network is utilized to compensate system perturbation due to linearization. Thus, control input of the crane system is composed of nominal PID and neural output signals respectively. Our method illustrates simple design procedure, but system perturbation and modelling error are overcome through a neural compensator. As well. adaptive neural control is constructed from online learning. Computer simulation demonstrates our control approach is superior to the classic control systems.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.760-763
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• 2004

The recent growth in the use of impactive and nonlinear loads, electronic, and medical devices sensitive to power quality has caused many power quality problems and power supply-and-demand problem. Recently, in power system not only the reliability of the power supply but also the DVR(Dynamic Voltage Restorer), UPS, and APF are being studied more and more. Hence, in this paper, Voltage sag detection algorithm for voltage sag corrector is proposed. Also, simple circuit for the experimental voltage sag is Introduced.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.566-569
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• 2004

The recent growth in the use of impactive and nonlinear loads, electronic devices sensitive to power quality has caused many power quality problems. Recently, in power system, not only the reliability of the power supply but also the DVR(Dynamic Voltage Restorer) are being studied more and more. The DVR is a series compensator which can instantaneously compensate a voltage variation in supply side, and is a more effective than a existing UPS(Uninterruptible Power Supply) which can be only used in limited range of loads such as single load. Hence, in this paper, a study of inverter side L-C filter output Voltage for DVR is discussed.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.69-71
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• 2008

Recently, the interest on power quality has been hot issue because the equipments cause voltage disturbance and become more sensitive to the voltage disturbance. The DVR(Dynamic Voltage Restorer) is one of the Custom Power Device that can compensate the voltage. DVR operates as a series connected compensator whose output voltage can be controlled system voltage. And the magnitude of compensation voltage is limited by the characteristics of system and load. Compensation capability of DVR was simulated by EMTDC under several condition. This paper analyzed effect of DVR's compensation at power quality test center which has SSFG(Sag, swell, and Flicker Generator, CPDs(SSTS, DVR, DSTATCOM), and loads.

• Proceedings of the KIEE Conference
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• 1999.11a
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• pp.56-60
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• 1999

This paper presents the high performance real time control system of PWM inverter for uninterruptible power supply(UPS). This system is based on a digital control scheme which calculates the pulse widths of the inverter switches for the next sampling time in digital signal processor(DSP). A PI compensator is used to eliminate the voltage error caused by the difference between the actual values of LC filter and those designed. Double regulation loops which are the inner current loop and the outer voltage loop are used to make the transient response time reduce in load disturbance and nonlinear load. This method makes it possible to obtain better response in comparison to conventional digital control system. The proposed scheme provides good performance such as stable operation, low THD of the output voltage, and good dynamic response for load variations and nonlinear load.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.965-967
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• 2001

전원 측 전압강하/상승 (Voltage sag/swell)을 보상하기 위한 동적전압보상기(Dynamic Voltage Restorer)등의 직렬 보상기에서 스위칭으로 인한 인버터 출력전압의 맥동(ripple)을 제거하기 위해 LC 필터가 사용된다. 본 논문에서는 LC 필터에서 커패시터의 전압을 상태 궤환을 이용하여 제어하는 알고리즘을 제시한다. LC 필터의 이산시간 상태 방정식을 구한 후, 궤환 이득값을 구하는 과정이 z-평면에서 이루어진다. 그리고, 제어기의 계산지연을 고려하여, 상태 관측기를 설계한다. 제안된 제어기는 기존 직렬보상기와 달리 전류 센서를 필요로 하지 않기 때문에 경제적인 이점을 가지게 된다.