• Journal of the Korean Solar Energy Society
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• v.29 no.5
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• pp.65-72
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• 2009

The new method is proposed to improve high speed detection of grid voltage phase and magnitude during a voltage dip due to a grid faults. Usually, A LPF(Low Pass Filter) is used in the feedback loop of PLL (Phase Locked Loop) system because the measured grid voltage contains harmonic distortions and sensor noises. so, a new design method of the loop gain of the PI -type controller in the PLL system is proposed with the consideration of the dynamics of the LPF. As a result, a better transient response can be obtained with the proposed design method. The LPF frequency and PI controller gain are designed in coordination according to the steady state and dynamic performance requirement. This paper shows the feasibility and the usefulness of the proposed methods through the computer simulation and the lab-scale experiments.

• Transactions on Control, Automation and Systems Engineering
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• v.2 no.3
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• pp.196-200
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• 2000

A neural controller for process control is proposed that combines a conventional multi-loop PID controller with a neural network. The concept of target signal based on feedback error is used fur on-line learning of the neural network. This controller is applied to distillation column control to illustrate its effectiveness. The result shows that the proposed neural controller can cope well with disturbance, strong interactions, time delays without any prior knowledge of the process.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.3
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• pp.17-24
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• 2003

One of the most important performance criteria related to the gain tuning of controller for CNC machining center is the contour error. This study analyzed circular error by the axis-matched and mismatched cases. To reduce ellipse and radius error, it is necessary to set the gain for each axis to be same bandwidth and high response. Based on the analysis in the frequency domain, we simulate feed system by mathematical model and then predict bandwidth of each axis. For analysis of structure vibration while the each axis is moving, we try the various of measuring method and position loop is improved by jerk limit.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.4
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• pp.167-175
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• 2001

This paper presents design of active roll controller of a vehicle and experimental study using the electric actuating roll control system. Firstly, parameter sensitivity analysis is performed based on 3DOF linear vehicle model. The controller is designed in the frame work of gain-scheduled H$\infty$ control scheme considering the varying parameters induced by laden and running vehicle condition. In order to investigate a feasibility of an active control system, experimental work is performed using hardware-in-the -loop setup which has been constructed by the devised electric actuating system and the full vehicle model with tire characteristics. The performance is evaluated by experiment using hardware-in-the -loop simulation under the conditions of some steer maneuvers and parameter variations.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.830-835
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• 1998

This paper describes a new digital control method of 3-phase PWM inverter with LC filter for uninterruptible power supply(UPS). The overall control system is based on the dead beat control, which has the minor loop of current control within the voltage control major loop. In this paper, the full-order disturbance observer is proposed to compensate the disturbances generated due to a sudden change of load currents. The proposed disturbance observer is composed of dead beat observer which estimates state values within a finite time, and cancels the disturbances by adding feedforward compensation loop in the control system. In addition, on order to remove a defect of oscillation generated in output of conventional dead beat controller, a modified dead beat algorithm is proposed in this paper.

• International Journal of Automotive Technology
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• v.8 no.3
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• pp.351-359
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• 2007

In this study, a hierarchical switching control scheme based on robust control theory is proposed for tracking control of vehicle longitudinal acceleration in the presence of large uncertainties. A model set consisting of four multiplicative-uncertainty models is set up, and its corresponding controller set is designed by the LMI approach, which can ensures the robust performance of the closed loop system under arbitray switching. Based on the model set and the controller set, a switching index function by estimating the system gain of the uncertainties between the plant and the nominal model is designed to determine when and which controller should be switched into the closed loop. After theoretical analyses, experiments have also been carried out to validate the proposed control algorithm. The results show that the control system has good performance of robust stability and tracking ability in the presence of large uncertainties. The response time is smaller than 1.5s and the max tracking error is about $0.05\;m/S^2$ with the step input.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.538-548
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• 2014

This study provides a robust control of a grid-connected three-phase two-level photo voltaic inverter. The introduced control method uses the cascade control strategy to regulate AC-side current and DC-link voltage. A robust controller with integration action is used for the inner-loop AC-side current control, which maximizes the convergence rate using a linear matrix inequality-based optimization design method and eliminates the offset error. The robust controller design method considers the parameter uncertainty set to accommodate parameter mismatch and un-modeled components in the inverter model. An outer-loop proportional-integral controller is used to regulate DC-link voltage with linearization of DC/AC relation. The proposed control strategy is applied to a grid-connected 100 kW photo voltaic inverter.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.396-400
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• 1996

It is prerequisite to apply dynamics controller to control robot manipulator required to perform fast and Precise motion. In this Paper, we Propose an adaptive 3earning control method for the dynamic control of a robot manipulator. The proposed control scheme is made up of PD controller in the feedback loop and the adaptive learning controller in the feedforward loop. This control scheme has the ability to estimate uncertain dynamic parameters included intrinsically in the system and to achieve the desired performance without the nasty matrix operation. The proposed method is applied to a SCARA robot and experimentally verified.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3B
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• pp.570-576
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• 2000

This paper proposed LQ-Servo PI controller by considering LQ-Servo structure as PI controller with a partial state feedback and concerns about the development of the flexible design algorithm by introducing weights to the design parameters of the previous LQ-Servo design method. the propose algorithm improves the matchings of the maximum and minimum singular values at high and low frequencies of the design loop transfer function as well as its loop shaping for performance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.3 s.108
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• pp.298-306
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• 2006

In our previous paper, we developed a robust saturation controller for the linear time-invariant (LTI) system involving both actuator's saturation and structured real parameter uncertainties. This controller can only guarantee the closed-loop robust stability of the system in the presence of actuator's saturation. But we cannot analytically make any comment on control performance of this controller. In this paper, we suggest a method to use linear matrix inequality (LMI) optimization problem which can analytically explain control performance of this robust saturation controller only in nominal system. The availability of design method using LMI optimization problem for this robust saturation controller is verified through a numerical example for the building with an active mass damper (AMD) system.