• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1659-1663
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• 2006

A many-body master equation is constructed by incorporating stochastic terms responsible for chemical reactions into the many-body Smoluchowski equation. Two forms of Langevin-type of memory equations describing the time evolution of dynamical variables under the influence of time-independent perturbation with an arbitrary intensity are derived. One form is convenient in obtaining the dynamics approaching the steady-state attained by the perturbation and the other in describing the fluctuation dynamics at the steady-state and consequently in obtaining the linear response of the system at the steady-state to time-dependent perturbation. In both cases, the kinetics of statistical averages of variables is found to be obtained by analyzing the dynamics of time-correlation functions of the variables.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.174-178
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• 2001

An improved stationary frame-based digital current control technique for a permanent magnet (PM) synchronous motor is presented. Generally, the stationary frame current controller is known to provide the advantage of a simple implementation. However, there are some unavoidable limitations such as a steady-state error and a phase delay in the steady-state. On the other hand, in the synchronous frame current regulator, the regulated currents are dc quantities and a zero steady-state error can be obtained through the integral control. However, the need to transform the signals between the stationary and synchronous frames makes the implementation of a synchronous frame regulator complex. Although the PI controller in the stationary frame gives a steady-state error and a phase delay, the control performance can be greatly improved by employing the exact decoupling control inputs for the back EMF, resulting in an ideal steady-state control characteristics irrespective of an operating condition as in the synchronous PI decoupling controller. However, its steady-state response may be degraded due to the inexact cancellation inputs under the parameter variations. To improve the control performance in the stationary frame, the disturbance is estimated using the time delay control. The proposed scheme is implemented on a PM synchronous motor using DSP TMS320C31 and the effectiveness is verified through the comparative simulations and experiments.

• Journal of Power Electronics
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• v.1 no.2
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• pp.88-98
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• 2001

An improved stationary frame-based digital current control technique for a permanent magnet(PM) synchronous motor is presented. Generally, the stationary frame current controller is known to provide the advantage of a simple implementation. However, there are some unavoidable limitations such as a steady-state error and a phase delay in the steady-state. On the other hand, in the synchronous frame current regulator the regulated currents are dc quantities and a zero steady-state error can be obtained through the integral control. However, the need to transform the signals between the stationary and synchronous frames makes the implementation of a synchronous frame regulator complex. Although the PI controller in the stationary frame gives a steady-state error and a phase delay, the control performance can be greatly improved by employing the exact decoupling control inputs for the back EMF., resulting in an ideal steady-state control characteristics irrespective of an operating condition as in the synchronous PI decoupling controller. However, its steady-state response may be degraded due to the inexact cancellation inputs under the parameter variations. To improve the control performance in the stationary frame, the disturbance is estimated using the time delay control. The proposed scheme is implemented on a PM synchronous motor using DSP TMS320C31 and the effectiveness is verified through the comparative simulations and experiments.

• Journal of Power Electronics
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• v.15 no.2
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• pp.346-355
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• 2015

On the basis of the conventional PID control algorithm, a modified adaptive PID (MA-PID) control algorithm is presented to improve the steady-state and dynamic performance of closed-loop systems. The proposed method has a straightforward structure without excessively increasing the complexity and cost. It can adaptively adjust the values of the control parameters ($K_p$, $K_i$ and $K_d$) by following a new control law. Simulation results show that the line transient response of the MA-PID is better than that of the adaptive digital PID because the differential coefficient $K_d$ is introduced to changes. In addition, experimental results based on a FPGA indicate that the MA-PID control algorithm reduces the recovery time by 62.5% in response to a 1V line transient, 50% in response to a 500mA load transient, and 23.6% in response to a steady-state deviation, when compared with the conventional PID control algorithm.

• Journal of Power Electronics
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• v.18 no.3
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• pp.766-777
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• 2018

In this paper, a sliding mode and proportional plus integral (SM-PI) control combined with self-sustained phase shift modulation (SSPSM) for LLC resonant converters is presented. The proposed control scheme improves the transient response while preserving good steady-state performance. An averaged large signal model of an LLC converter with the ZVS modulation technique is developed for the SM control design. The sliding surface is obtained based on the input-output linearization concept. A system identification method is adopted to obtain the transform function of the LLC resonant converter, which is used to design the PI control. In order to reduce the inherent chattering problem in the steady state, the combined SM-PI control strategy is derived with fuzzy control, where the SM control is responsive during the transient state while the PI control prevails in the steady state. The combination of SSPSM and the SM-PI control provides ZVS operation, robustness and a fast transient response against step load variations. Simulation and experimental results validate the theoretical analysis and the attractive features of the proposed scheme.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.246-250
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• 2015

In this paper, Timoshenko and Euler-Bernoulli beam theories(EB-beam) are used, and Fast Fourier Transformation(FFT) analysis is then employed to extract their natural frequencies using both analytical approach and Co-rotational plane beam(CR-beam) EDISON program. EB-beam is used to analyze a spring-mass system with a single degree of freedom. Sinusoidal force with various frequencies and constant magnitude are applied to tip of each beam. After the oscillatory tip response is observed in EB-beam, it decreases and finally converges to the so-called 'steady-state.' The decreasing rate of the tip deflection with respect to time is reduced when the forcing frequency is increased. Although the tip deflection is found to be independent of the excitation frequency, it turns out that time to reach the steady state response is dependent on the forcing frequency.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.64-69
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• 2004

The work presented here deals with controller design using error model constructed with proportional control ramp response. The design aims at the improvement of transient response, steady-state error reduction with stability preservation, generation of the consistent contour error through the proportional gain regulation of a mismatched system. The first step is to generate tracking-error curve with proportional control only and decide the added error signal shape on the error curve. The next is to construct a table for the steady-state loop gain with step input. The table is used for selecting the proportional gain. The effectiveness of the proposed controller is confirmed through the simulation and experiment.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1992.11a
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• pp.51-55
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• 1992

By using the state plane approach, the steady state analysis and design of a half bridge parallel-series (LLC-type) resonant converter (HBPSRC) operating in the continous conduction made is presented. The state-plane diagram representation of the converter response gives good insight into the converter operation. Based on this analysis, a set of steady state characteristic waves for HBPSRC is presented. A simple design procedure is given and design example for a 100watts, 30KHz HBPSRC is presented for illustrative purposes.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.179.5-179
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• 2001

Generally, while PD-type fuzzy controller has good performance in transient period, it has uniform steady state error of response. To improve limitations of PD-type fuzzy controller, we propose a new fuzzy controller to improve the performance of transient response and to eliminate the steady state error of response. In this paper, PD-type fuzzy controller is used a simplified indirect inference method(SIIM). When the SIIM is applied, the proposed method has the capability of the high speed inference and adapting with increasing the number of the fuzzy input variables easily. The outputs of this controller are the output calculated by PD-type fuzzy controller and the accumulated error scaling factor. Here, the accumulated error scaling factor is adjusted by fuzzy rule according to the system state variables. To show the usefulness of the proposed controller, it is applied to 0-type 2nd-order linear system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12A
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• pp.983-990
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• 2003

In this paper, a noncoherent code tracking loop is designed for 3GPP MODEM and its performance is analyzed in terms of steady-state jitter variance and transient response characteristics. An analytical closed-form formula for steady-state jitter variance is Int derived for AWGN environments as a general function of a pulse-shaping filter, timing offset, signal-to-interference ratio, and loop bandwidth, together with the analysis on the transient response characteristic of a tracking loop. Based on the analysis, the code tracking loop with variable loop bandwidth that is efficient for full digital H/W implementation is designed and its performance is compared with that of the code tracking loop with fixed loop bandwidth, along with the verification by computer simulations.