• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.384-388
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• 1996

The closed-loop system modeling of an Active/semiactive suspension system has been accomplished through an artificial neural Networks. The 7DOF full model as the system equation of motion has been derived and the output feedback linear quadratic regulator has been designed for the control purpose. For the neural networks training set of a sample data has been obtained through the computer simulation. A 7DOF full model with LQR controller simulated under the several road conditions such as sinusoidal bumps and the rectangular bumps. A general multilayer perceptron neural network is used for the dynamic modeling and the target outputs are feedback to the input layer. The Backpropagation method is used as the training algorithm. The modeling of system and the model validation have been shown through computer simulations.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.128-130
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• 2001

This paper proposes the design of LQ-PSS(linear quadratic power system stabilizer) for improving power system stability using genetic algorithm(GA). We are tuned weighting matriecs of LQ-PSS using GA. To evalute the usefulness of the proposed method. we performed the nonlinear simulation on a single machine infinite system. As results of the simulation. the proposed method shows the better control performance than CPSS(conventional power system stabilizer) in trems of settling time and damping effects.

• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.584-586
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• 1997

The orthogonal polynomials have been widely employed to solve control problems, but the LQG(linear quadratic gaussian) problem remains unsolved. In this paper, we obtained the solutions of Riccati equation and covariance matrix Riccati equation by two point boundary problem and matrix fraction method using BPF(Block Pulse Function), respectively. This solutions are solved the problem of the LQG controller design.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.3 no.1
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• pp.58-65
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• 2003

In this paper, a new model, which is a Takagi-Sugeno fuzzy model, for mobile robot is presented. A controller, consisting of two loops the one of which is the inner state feedback loop designed for stability and the outer loop is a PI controller designed for tracking the reference input, is suggested. Because the robot dynamics is nonlinear, it requires the controller to be insensitive to the nonlinear term. To achieve this objective, the model is developed by well known T-S fuzzy model. The design algorithm of inner state-feedback loop is regional pole-placement. In this paper, regions, for which poles of the inner state feedback loop are lie in, are formulated by LMI's. By solving these LMI's, we can obtain the state feedback gains for T-S fuzzy system. And this paper shows that the PI controller is equivalent to the state feedback and the cost function for reference tracking is equivalent to the LQ(linear quadratic) cost. By using these properties, it is also shown in this paper that the PI controller can be obtained by solving the LQ problem.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.6 no.1
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• pp.1-5
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• 2006

This paper deals with a fault detection system design for uncertain nonlinear systems modelled as T-S fuzzy systems with the integral quadratic constraints. In order to generate a residual signal, we used a left coprime factorization of the T-S fuzzy system. From the filtered signal of the residual generator, the fault occurence can be detected effectively. A simulation study with nuclear steam generator level control system shows that the suggested method can be applied to detect the fault in actual applications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.7
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• pp.1309-1313
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• 2010

In this paper, we propose a novel guidance law for controlling an UAV(Unmanned Air-Vehicle) to follow a reference line in vertical plane. A kinematics model representing the relative motion of the UAV to the reference line is derived. And then LQR(Linear Quadratic Regulator) theory is applied to the model to derive the VLFG(Vertical Line Following Guidance) law. The resultant guidance law forms a gain-scheduling controller scheduled by a simple parameter $\sigma$ which is a function of the UAV's velocity, axial acceleration, gravity, and the slope of the reference line. Also derived is a stability condition for the $\sigma$ variation based on Lyapunov theory. Simulation results show that the proposed guidance law can be applied effectively to UAV guidance algorithm design.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.72-74
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• 1994

This paper presents a linear quadratic gaussian(LQG) based power system stabilizer(PSS) to control subsynchronous resonance(SSR) that occurs in a series capacitor compensated power systems. The complete SSR system based on the IEEE first benchmark model is employed in this study. Eigenvalue analysis and time domain simulations using a nonlinear system model show that the proposed PSS controls SSR efficiently.

• Current Optics and Photonics
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• v.5 no.3
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• pp.289-297
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• 2021

We describe a comb-mode resolving spectroscopic technique by direct time-domain phase correction of unstable interferograms obtained from loosely locked two femtosecond lasers. A low-cost continuous wave laser and conventional repetition rate stabilization method were exploited for locking carrier and envelope phase of interferograms, respectively. We intentionally set the servo control at low bandwidth, resulting in severe interferograms' fluctuation to demonstrate the capability of the proposed correction method. The envelope phase of each interferogram was estimated by a quadratic fit of carrier peaks to correct timing fluctuation of interferograms in the time domain. After envelope phase correction on individual interferograms, we successfully demonstrated 1 Hz linewidth of RF comb-mode over 200 GHz optical spectral-bandwidth with 10-times signal-to-noise ratio (SNR) enhancement compared to the spectrum without correction. Besides, the group delay difference between two femtosecond pulses is successfully estimated through a linear slope of phase information.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.9
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• pp.1299-1303
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• 2001

For the Exp. 1, a total of fifty four crossbred [(Duroc Yorkshire)${\times}$Landrace] pigs ($77.67{\pm}1.42kg$ average initial BW) were used in a 41-d growth assay to determine the effects of yucca extract supplementation on growth performance, nutrient digestibility and serum characteristics of finishing pigs. Dietary treatments included 1) Control (basal diet), 2) YE60 (basal diet+60 ppm yucca extract), 3) YE120 (basal diet+120 ppm yucca extract). Average daily gain was not improved by yucca extract supplementation during the whole experimental perid (d 0 to 41). Pigs fed control diet showed the best average daily gain. Pigs fed control and YE120 diets tended to increase average daily feed intake compared with pigs fed YE60 diet (quadratic effect, p<0.0001). Gain/feed with control treatment was significantly better than the YE groups (linear effect, p<0.071). However, there was no significant difference among levels of yucca extract (p>0.10). Apparent digestibility of dry matter in pigs fed yucca extract were greater than for pigs fed control diets (linear effect, p<0.017). Pigs fed YE120 tended to have higher digestibility of nitrogen than pigs fed the control diets (linear effect, p<0.019). There were no significant differences in Total-, HDL- and LDL-cholesterol concentrations of serum, and the blood urea nitrogen (BUN) concentrations in serum was not influenced by the yucca extract supplementation (p>0.10). For the Exp. 2, fifteen [(Duroc${\times}$Yorkshire)${\times}$Landrace] pigs ($25.00{\pm}0.50kg$ average initial BW) were used in a 30-d metabolism experiment to determine the effects of yucca extract supplementation on fecal ammonia gas production. Treatments were : 1) Control (basal diet); 2) YE (basal diet+150 ppm yucca extract); 3) BD (basal diet+100 ppm Bio-Dr; yucca extract+far infrared emitted materials). Fecal ammonia gas production differences between d 0 and d 30 were significantly reduced (p<0.05) by feeding BD compared to control and YE. Also, when pigs were fed the diet with YE tended to be decreased ammonia gas production compared to pigs fed the control diet without significant differences (p>0.05). There were no differences for DM and N digestibility among pigs fed the treatment diets. In conclusion, yucca and (or) far infrared radiological materials can be used to make environment-friendly diets for growing-finishing pigs without negative effects on growth performance and nutrient digestibility.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.46-54
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• 1998

This paper presents a method for designing robust fuzzy $H^{\infty}$ controllers which stabilize nonlinear systems with parameter uncertainty adn guarantee an induced $L_{2}$ norm bound constraint on disturbance attenuation for all admissible uncertainties. Takagi and Sugeno's fuzzy models with uncertainty are used as the model for the uncertain nonlinear systems. Fuzzy control systems utilize the concept of so-called parallel distributed compensation(PDC). Using a single quadratic Lyapunov function, the stability condition satisfying decay rate and disturbance attenuation condition for Takagi and Sugeno's fuzzy model with parameter uncertainty are discussed. A sufficient condition for the existence of robust fuzzy $H^{\infty}$ controllers is then presented in terms of linear matrix inequalities(LMIs). Finally, design examples of robust fuzzy $H^{\infty}$ controllers for uncertain nonlinear systems are presented.