• 제어로봇시스템학회:학술대회논문집
• /
• 1999.10a
• /
• pp.284-287
• /
• 1999

A design of I-PDA controller for the third order plant by CDM is presented in this paper. Using CDM in the controller design procedures, the step responses of the controlled system with the I-PDA controller satisfied both transient and steady state response specifications without adjustment, and also satisfy the requirements of stability, faster response and robustness. The step responses of the controlled system using I-PDA controller are coiniciding to the ones using PIDA controller, and the integral gain of the I-PDA controller also equals to the prefilter gain of the PIDA controller designed by CDM. The effect of the disturbances can also be lastly eliminated. The fast step response of the controlled system can be obtained by reducing the equivalent time constant. MATLAB's numerical results show that the desired specifications of the controlled system using I-PDA controller is obtained. Furthermore, the results also show a good robustness that the desired performances of the controlled system have no significant changed when the plant parameters are varied.

• Progress in Superconductivity
• /
• v.7 no.1
• /
• pp.1-5
• /
• 2005

A pseudogap in the normal-state quasiparticle density of states of $high-T_c$ superconductors has been revealed in many different kinds of experiments. The existence of the pseudogap and the superconducting gap, and the correlation between them has attracted considerable attention because they are believed to be a key to understanding the mechanism of the $high-T_c$ superconductivity. The interlayer tunneling spectroscopy, excluding the surface-dependent effect, is one of the most accurate means to examine the electron spectral characteristics both in the superconducting and the normal states. In this study, a new constant-temperature intrinsic tunneling spectroscopic technique, excluding the overheating effect using the in-situ temperature monitoring combined with the digital proportional-integral-derivative control, is introduced. The implication on the $high-T_c$ superconductivity of the detailed temperature dependencies of the observed spectral weight in $Bi_{2}Sr_{2}CaCu_{2}O_{8+x}\;high-T_c$ material for overdoped and underdoped levels is discussed.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.3
• /
• pp.544-558
• /
• 2013

This paper proposes a simplified and efficient control scheme for Unified Power Quality Conditioner (UPQC) based on three-level (NPC) inverter capable to mitigate source current harmonics and compensate all voltage disturbances perturbations such us, voltage sags, swells, unbalances and harmonics. The UPQC is designed by the integration of series and shunt active filters (AFs) sharing a common dc bus capacitor. The dc voltage is maintained constant using proportional integral voltage controller. The shunt and series AF are designed using a three-phase three-level (NPC) inverter. The synchronous reference frame (SRF) theory is used to get the reference signals for shunt and the power reactive theory (PQ) for a series APFs. The reference signals for the shunt and series APF are derived from the control algorithm and sensed signals are injected in tow controllers to generate switching signals for series and shunt APFs. The performance of proposed UPQC system is evaluated in terms of power factor correction and mitigation of voltage, current harmonics and all voltage disturbances compensation in three-phase, three-wire power system using MATLAB-Simulink software and SimPowerSystem Toolbox. The simulation results demonstrate that the proposed UPQC system can improve the power quality at the common connection point of the non-linear load.

• Journal of the Korean Mathematical Society
• /
• v.45 no.2
• /
• pp.435-453
• /
• 2008

In this paper, by using q-deformed bosonic p-adic integral, we give $\lambda$-Bernoulli numbers and polynomials, we prove Witt's type formula of $\lambda$-Bernoulli polynomials and Gauss multiplicative formula for $\lambda$-Bernoulli polynomials. By using derivative operator to the generating functions of $\lambda$-Bernoulli polynomials and generalized $\lambda$-Bernoulli numbers, we give Hurwitz type $\lambda$-zeta functions and Dirichlet's type $\lambda$-L-functions; which are interpolated $\lambda$-Bernoulli polynomials and generalized $\lambda$-Bernoulli numbers, respectively. We give generating function of $\lambda$-Bernoulli numbers with order r. By using Mellin transforms to their function, we prove relations between multiply zeta function and $\lambda$-Bernoulli polynomials and ordinary Bernoulli numbers of order r and $\lambda$-Bernoulli numbers, respectively. We also study on $\lambda$-Bernoulli numbers and polynomials in the space of locally constant. Moreover, we define $\lambda$-partial zeta function and interpolation function.

• Bulletin of the Korean Mathematical Society
• /
• v.51 no.5
• /
• pp.1241-1257
• /
• 2014

We consider a class of hypoelliptic operators of the following type $$L=\sum_{i,j=1}^{p_0}a_{ij}{\partial}^2_{x_ix_j}+\sum_{i,j=1}^{N}b_{ij}x_i{\partial}_{x_j}-{\partial}_t$$, where ($a_{ij}$), ($b_{ij}$) are constant matrices and ($a_{ij}$) is symmetric positive definite on $\mathbb{R}^{p_0}$ ($p_0{\leqslant}N$). By establishing global Morrey estimates of singular integral on the homogenous space and the relation between Morrey space and weak Morrey space, we obtain the global weak Morrey estimates of the operator L on the whole space $\mathbb{R}^{N+1}$.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.271-272
• /
• 2006

This paper presented a new experimental gain tuning technique for a Multi-Axis Servo System. First, the investigation for proportional gain of velocity control loop by using a Dynamic Signal Analyzer (DSA) was performed. Using the FUNCTION characteristic of DSA based on the Bode plot, the Bode plot of open loop transfer function was obtained. In turn, the integral gain of a servo controller can be found out by using the Integration time constant extracted from the Bode plot of open loop transfer function. In the meanwhile, the positional gain of the servo controller has been obtained by using the Bode plot of the closed loop transfer function. We have also proposed the technique to find out an optimal parameter of a notch filter, which has a great influence on vibration reduction, by using the damping factor extracted from the Bode plot of closed loop transfer function.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.25 no.6
• /
• pp.410-420
• /
• 2016

The geometric dimension and shape of microchannels that are formed during surface texturing are widely studied for applications in flow control, and drag and friction reduction. In this research, a new method for controlling the deformation of U channels during micro-rolling-based surface texturing was developed. Since the width of the U channels is almost constant, controlling the depth is essential. A calibration procedure of initial rolling gap, and proportional-integral PI controllers and a linear interpolation have been applied simultaneously to control the depth. The PI controllers drive the position of the pre-U grooved roll as well as the rolling gap. The relationship between the channel depth and rolling gap is linearized to create a feedback signal in the depth control system. The depth of micro channels is studied on A2021 aluminum lamina surfaces. Overall, the experimental results demonstrated the feasibility of the method for controlling the depth of microchannels.

• Korean Journal of Remote Sensing
• /
• v.27 no.3
• /
• pp.225-234
• /
• 2011

This study proposes an inversion algorithm to extract the surface parameters, such as surface roughness and soil moisture contents, using multi-frequency SAR data. The study areas include the tidal flats of Jebu Island and the reclaimed lands of Hwaong district on the western coasts of the Korean peninsula. SAR data of three frequencies were accordingly calibrated to provide precise backscattering coefficients through absolute radiometric calibration. The root mean square (RMS) height and the correlation length, which can describe the surface roughness, were extracted from the backscattering coefficients using the inversion of the Integral Equation Method (IEM). The IEM model was appropriately modified to accommodate the environmental conditions of tidal flats. Volumetric soil moisture was also simultaneously extracted from the dielectric constant using the empirical model, which define the relations between volumetric soil moistures and dielectric constants. The results obtained from the proposed algorithm were verified with the in-situ measurements, and we confirmed that multi-frequency SAR observations combined with the surface scattering model for tidal flats can be used to quantitatively retrieve the geophysical surface parameters in tidal flats.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.4 no.4
• /
• pp.423-436
• /
• 2012

Unstiffened plates are integral part of all kinds of structures such as ship and offshore oil platforms. Openings are unavoidable and absolutely reduce the ultimate strength of structures. In this study, the finite element analysis package, ABAQUS, is used to analyze the behavior of unstiffened plate with rectangular opening. The rectangular opening form is divided into two cases. In case1, opening depth is constant, but opening width is varied. Meanwhile, in case2 opening width is fixed and opening depth is varied. Besides, for the two different form opening, the effect of plate slenderness parameter (${\beta}$), opening area ratio (AR) and opening position ratio (PR) on the ultimate strength of plate with opening under axial compression are presented. It has been found that the ultimate strength of plate ofcase1is much more sensitive to the plate slenderness parameter (${\beta}$) and opening area ratio (AR) than that of case2. However, for case1, opening position (PR) almost has no effect on the ultimate strength, whereas, regardingcase2, the influence of opening position (PR) depends on the plate slenderness parameter (${\beta}$). Based on nonlinear regression analysis, three design formulae are not only developed but also approved reasonably for the practical engineering design.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.12
• /
• pp.1864-1871
• /
• 2012

This paper proposes the hybrid proportional integral(HBPI) controller for maximum power point tracking(MPPT) control of photovoltaic system. The output characteristics of the solar cell are a nonlinear and affected by a temperature, the solar radiation and influence of a shadow. The MPPT control is a very important technique in order to increase an output and efficiency of the photovoltaic system. The conventional constant voltage(CV), perturbation and observation(PO) and incremental conductance(IC) are the method which finding maximum power point(MPP) by the continued self-excitation vibration, and uses the fixed step size. If the fixed step size is a large, the tracking speed of maximum power point is faster, but the tracking accuracy in the steady state is decreased. On the contrary, when the fixed step size is a small, the tracking accuracy is increased and the tracking speed is slower. Therefore, in order to solve these problems, this paper proposes HBPI controller that is adjusted gain of conventional PI control using fuzzy control, and the maximum power point tracks using this controller. The validity of the controller proposed in this paper proves through the results of the comparisons.