• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2240-2245
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• 2003

In this paper, the controller design by coefficient diagram method (CDM) for controlling the trolley position, load-swing angle and hoisting rope length of the overhead crane system simultaneously is proposed. The overhead crane system is a MIMO system consisting of two inputs and three outputs. Its mathematical model is nonlinear with coupling characteristics. This nonlinear model can be approximated to obtain a linear model where the first input mainly affects the trolley position and the load-swing angle while the second input mainly affects the hoisting rope length. In order to utilize the CDM concept for assigning the controllers, namely PID, PD and PI controllers separately, the model is approximated to be three transfer functions in accordance with trolley position, the load-swing angle and the hoisting rope length controls respectively. The satisfied performances of the overhead crane system controlled by the these controllers and fast rejection of the disturbance effect occurred at the trolley position are shown by simulation and experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.433-437
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• 2003

Quantitative Feedback Theory (QFT) is one of effective methods of robust controller design. In QFT design we can considers the phase information of the perturbed plant so it is less conservative than $H_{\infty}$ and ${\mu}$-synthesis methods and as be shown, it is more transparent than the sensitivity reduction methods mentioned . In this paper we want to overcome the major drawback of QFT method which is lack of an automatic method for loop-shaping step of the method so we focus on the following problem: Given a nominal plant and QFT bounds, synthesize a controller that achieves closed-loop stability and satisfies the QFT boundaries. The usual approach to this problem involves loop-shaping in the frequency domain by manipulating the poles and zeros of the nominal loop transfer function. This process now aided by recently developed computer aided design tools proceeds by trial and error and its success often depends heavily on the experience of the loop-shaper. Thus for the novice and First time QFT user, there is a genuine need for an automatic loop-shaping tool to generate a first-cut solution. Clearly such an automatic process must involve some sort of optimization, and while recent results on convex optimization have found fruitful applications in other areas of control theory we have tried to use LMI theory for automating the loop-shaping step of QFT design.

• International Journal of Control, Automation, and Systems
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• v.6 no.5
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• pp.639-650
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• 2008

Electricity price forecasting has become an integral part of power system operation and control. In this paper, a wavelet transform (WT) based neural network (NN) model to forecast price profile in a deregulated electricity market has been presented. The historical price data has been decomposed into wavelet domain constitutive sub series using WT and then combined with the other time domain variables to form the set of input variables for the proposed forecasting model. The behavior of the wavelet domain constitutive series has been studied based on statistical analysis. It has been observed that forecasting accuracy can be improved by the use of WT in a forecasting model. Multi-scale analysis from one to seven levels of decomposition has been performed and the empirical evidence suggests that accuracy improvement is highest at third level of decomposition. Forecasting performance of the proposed model has been compared with (i) a heuristic technique, (ii) a simulation model used by Ontario's Independent Electricity System Operator (IESO), (iii) a Multiple Linear Regression (MLR) model, (iv) NN model, (v) Auto Regressive Integrated Moving Average (ARIMA) model, (vi) Dynamic Regression (DR) model, and (vii) Transfer Function (TF) model. Forecasting results show that the performance of the proposed WT based NN model is satisfactory and it can be used by the participants to respond properly as it predicts price before closing of window for submission of initial bids.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2056-2062
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• 2013

The dihydroxy naphthalene/$TiO_2$ complexes with different substitution patterns were prepared by surface modification. X-ray diffraction, UV-Vis spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy were used to characterize the prepared composite materials. The results indicated that the surface modification did not influence the crystallization of $TiO_2$. The visible-light absorbances of prepared dihydroxy naphthalene/$TiO_2$ complexes could be assigned to the ligand-to-metal charge transfer. The obtained catalyst exhibited outstanding photocatalytic activity and stability under visible light. A linear relationship existed between the percentages of hydroxynaphthalenes coordinated on $TiO_2$ surface and $H_2$ production ability. The substitution pattern of dihydroxy naphthalene and $CH_3OH$ content could also influence the photocatalytic performance remarkably. The photocatalytic $H_2$ production ability was further improved after loading with ultra low concentration of Pt, 0.02 wt %. The possible mechanism was proposed.

• Steel and Composite Structures
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• v.20 no.4
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• pp.869-887
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• 2016

The socket-spigot template supporting system is widely used in engineering applications in China. As a newer type of support structure, there has been growing research interest in its bearing capacity. In this paper, four vertical bearing capacity tests were carried out on the basic mechanical unit frame of a socket-spigot template supporting system. The first goal was to explore the influence of the node semi-rigid degree and the longitudinal spacing of the upright tube on the vertical bearing capacity. The second objective was to analyze the displacement trend and the failure mode during the loading process. This paper presents numerical analysis of the vertical bearing capacity of the unit frames using the finite element software ANSYS. It revealed the relationship between the node semi-rigid degree and the vertical bearing capacity, that the two-linear reinforcement model of elastic-plastic material can be used to analyze the socket-spigot template supporting system, and, through node entity model analysis, that the load transfer direction greatly influences the node bearing area. Finally, this paper indicates the results of on-site application performance experiments, shows that the supporting system has adequate bearing capacity and stability, and comments on the common work performance of a socket and fastener scaffold.

• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.396-403
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• 2014

This paper considered the prediction of the tension force in the design of a TLP tendon, particularly focusing on the springing problem. Springing is an important parameter that exerts a large tension in special cases. It is a nonlinear phenomenon and requires the 2nd-order wave loads to solve. In this paper, a new prediction method for springing and the resultant extreme tension on the tendon of a TLP is introduced. Using the 2nd-order response function computed using the commercial program WADAM, the probability density function of the 2nd-order tension is obtained from an eigenvalue analysis using a quadratic transfer function and sea spectra. A new method is then suggested to predict the extreme tension loads with respect to the number of occurrences. It is shown that the PDF suggested in this study properly predicts the extreme tension in comparison with the time histories of the 2nd-order tension. The expected tension force is larger than that from a linear analysis in the same time windows. This supports the use of the present method to predict the tension due to springing.

• Structural Engineering and Mechanics
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• v.73 no.2
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• pp.123-132
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• 2020

Steel spherical hinged bearings have high loading capacity, reliable load transfer, flexible rotation with universal hinge and allowance of large displacement and rotation angle. However, bearings are in complex forced states subject to various load combinations, which lead to the significant influence on integral structural safety. Taking the large-tonnage complex steel spherical hinged bearings of Terminal 2 of Guangzhou Baiyun International Airport as an example, full-scale rotation and shear behaviour tests of the bearings subject to axial tensile load are carried out, and the corresponding finite element simulation analyses are conducted. The results of experiments and finite element simulations are in good agreement with the coincident development tendency of stress and deformation. In addition, the measured rotational moment is less than the calculated moment prescriptive by the code, and the relationship between horizontal displacement and horizontal shear force is linear. Finally, based on these results, the rotation and shear stiffness models of bearings subject to axial tensile load are proposed for the refinement analysis of integral structure.

• Analytical Science and Technology
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• v.28 no.6
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• pp.425-429
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• 2015

A cholesterol biosensor was developed using a modified carbon electrode with carbon nanotubes. The disposable cholesterol biosensor was modified with carbon nanotubes to enhance electron transfer during the enzymatic reaction of cholesterol. Cholesterol oxidase and peroxidase, with potassium ferrocyanide as a mediator, were immobilized on a screen-printed carbon nanotube electrode. The electrochemical cholesterol biosensor developed using carbon nanotubes showed a rapid and reliable signal for measuring total cholesterol. The cholesterol sensor showed a linear response in 5 seconds with a small volume (0.5 μL) in the range of 100~400 mg/dL, with a coefficient of variation of 4.0%.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.163-163
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• 2015

The effect of nematic liquid crystal(5CB-4-Cyano-4'-pentylbiphenyl) on the amorphous indium gallium zinc oxide thin film transistors(a-IGZO TFTs) was investigated. Through dropping the 5CB on the a-IGZO TFT's channel layer which is deposited by RF-magnetron sputtering, properties of a-IGZO TFTs was dramatically improved. When drain bias was induced, 5CB molecules were oriented by Freedericksz transition generating positive charges to one side of dipoles. From increment of the capacitance by orientation of liquid crystals, the drain current was increased, and we analyzed these phenomena mathematically by using MOSFET model. Transfer characteristic showed improvement such as decreasing of subthreshold slope(SS) value 0.4 to 0.2 and 0.45 to 0.25 at linear region and saturation region, respectively. Furthermore, in positive bias system(PBS), prevention effect for electron trapping by 5CB liquid crystal dipoles was observed, which showing decrease of threshold voltage shift [(${\delta}V$]_TH) when induced +20V for 1~1000sec at the gate electrode.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1123-1131
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• 1993

A robust controller is proposed to design a flight autopilot for lateral motion control. The control system has two control loops in order to meet the performance and to maintain the stability-robustness for a nonsquare flight system with uncertain aerodynamic variations and disturbance. One is designed via linear quadratic Gaussian with loop transfer recovery(LQG/LTR) design methodology for the inner loop. The other is designed via proportional controller design method for the outer loop. To show the effectiveness of this control system, it is compared with the LQG/LTR control system for a square flight system and is analyzed for the performance/stability-robustness to model uncertainties and disturbance via wind gusts. It is found that the proposed control system has good heading command-following performance under allowable sideslip angle in spite of model uncertainties and disturbance.