• Journal of information and communication convergence engineering
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• 제17권4호
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• pp.255-260
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• 2019

A pendubot is a representative example of an underactuated system that has fewer actuators than the degree of freedom of the system. In this study, the characteristics of the pendubot are first reviewed; each part is then designed using Solidworks by dividing the pendubot into three parts: the base frame, first link frame, and second link frame. These three parts are then imported into the Simulink environment via a STEP file format, which is the standard protocol used in data exchange between CAD applications. A 3D model of the pendubot is then constructed using Simscape, and the usefulness of the 3D model is validated by a comparison with a dynamic equation derived using the Lagrangian formulation. A linearized model around an upright equilibrium position is finally obtained, and a sliding mode controller is designed based on the linear quadratic regulator. Simulation results showed that the designed controller effectively maintained upright balance of the pendubot in the presence of disturbance.

• 한국지능시스템학회논문지
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• 제12권3호
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• pp.255-260
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• 2002

This paper describes a fuzzy-based system for analyzing the stress intensity factors (SIFs) of three-dimensional (3D) cracks. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy knowledge processing. Nodes are generated by the bucketing method, and ten-coded quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. The singular elements such that the mid-point nodes near crack front are shifted at the quarter-points, and these are automatically placed along the 3D crack front. The complete finite element(FE) model is generated, and a stress analysis is performed. The SIFs are calculated using the displacement extrapolation method. To demonstrate practical performances of the present system, semi-elliptical surface cracks in a inhomogeneous plate subjected to uniform tension are solved.

• 한국정밀공학회지
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• 제21권7호
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• pp.107-114
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• 2004

This paper presents a two-time scale approach for vibration reduction of a high speed Cartesian manipulator. High speed manipulators would be subject to mechanical vibration due to high inertia forces acting on linkages. To achieve high throughput capability, such motion induced vibration would have to be damped quickly, to reduce settling time of the manipulator end-effector. This paper develops a two-time scale model fer a structurally-flexible Cartesian manipulator. Based on the two-time scale model, a composite controller consisting of a computed torque method for the slow time-scale rigid body subsystem, and a linear quadratic state-feedback regulator for the fast time-scale flexible subsystem, is designed. Simulation results show that the proposed two time-scale controller yields good performance in attenuating structural vibration arising due to excitation from inertial forces.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.510-513
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• 2004

This paper represents the response surface model for the cell gap on the flexible liquid crystal display (LCD) process. Using response surface methodology (RSM). D-optimal design is carried out to build the design space and the cell gap is characterized by the quadratic model. The statistical analysis is used to verify the response surface model. This modeling technique can predict the characteristics of the desired response, cell gap, varying with process conditions.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.566-573
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• 1999

This paper is the result of sensitivity analysis of derailment with respect to the selected suspension elements for the rail vehicle. Derailment phenominon has been explained by the derailment quotient. Thus, the sensitivity of derailment is suggested by a response surface model(RSM) which is a functional relationship between derailment quotient and characteristics of suspension elements. To summarize generation of RSM, we can introduce the procedure of sensitivity analysis as follows. First, to form a RSM, a experiment is performed by a dynamic analysis code, VAMPIRE according to a kind of the design of experiments(DOE). Second, RSM is constructed to a 1$\^$st/ order polynomial and then main effect fators are screened through the stepwise regression. Finally, we can see the sensitivity level through the RSM which only consists of the main effect factors and is expressed by the liner, interaction and quadratic effect terms.

• Membrane and Water Treatment
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• 제10권6호
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• pp.431-440
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• 2019

A novel composite membrane was synthesized using crosslinked polyamide and fly ash ceramic substrate for phenol removal. Glutaraldehyde was used as crosslinker. Characterization shows that synthesized membrane possesses good permeability ($0.184l.m^{-2}.h^{-1}.kPa^{-1}$), MWCO (1.7 kDa), average pore size (1.08 nm) and good chemical stability. RSM was adopted for phenol removal studies. Box-Behnken-Design using quadratic model was chosen for three operating parameters (feed phenol concentration, pH and applied pressure) against two responses (phenol removal, flux). ANOVA shows that model is statistically valid with high coefficient of determination ($R^2$)value for flux (0.9897) and phenol removal (0.9302). The optimum conditions are obtained as pH 2, $46mg.l^{-1}$ (feed phenol concentration) and 483 kPa (applied pressure) with 92.3% phenol removal and $9.2l.m^{-2}.h^{-1}$ flux. Data validation with deviation of 4% confirms the suitability of model. Obtained results reveal that prepared composite membrane can efficiently separate phenol from aqueous solution.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.115-123
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• 2003

With the advent of high performance computers and more efficient numerical algorithms, computational fluid dynamics(CFD) has come out as a modem alternative for reducing the use of wind tunnels test in automotive engineering. However, in spite of the fact that many competent researchers have made all their talents in developing turbulence model over since the past dozen or more years, it has been an important impediment in using the CFD effectively to design machinery and to diagnose or to improve engineering problems in the industry since the turbulence model has been acting as the Achilles' tendon in aspect of the reliability even to this time. In this study, Reynolds-averaged Wavier-Stokes equations were solved to simulate an incompressible turbulent flow around a bus-like bluff body near ground plane. In order to investigate the effect of the discretisation schemes and turbulence model on the aerodynamic forces several turbulence models with five convective difference schemes are adopted. From the results of this study, it is clear that choice of turbulence model and discretisation scheme profoundly affects the computational outcome. The results also show that the adoption of RNG $k-\varepsilon$ turbulence model and nonlinear quadratic turbulence model with the second order accurate discretisation scheme predicts fairly well the aerodynamic coefficients.

• 농업과학연구
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• 제41권4호
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• pp.461-472
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• 2014

This study was conducted to build the CFD simulation model which can quantify the distribution of the meteorological factors in air-heated greenhouse for chrysanthemum according to the location and capacity of air-circulation fan. The CFD model was also verified by experiment. It was judged that SST model was the most appropriate turbulence model which can properly describe the airflow by the air-circulation fan. According to the simulation results, the differences between the measured and predicted temperatures from 18 points at each height in the greenhouse were $0.2{\sim}0.4^{\circ}C$ in average. This showed a good agreement between the predicted data and the measured ones. The developed CFD model can be a useful tool to evaluate and design the air-circulation systems in the greenhouse with various configurations.

• 한국수산과학회지
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• 제28권5호
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• pp.607-623
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• 1995

A numerical model of hydraulic resistance by hanging aquaculture facilities is developed and applied to a model basin and a field. A drag stress term formulated by the quadratic law of drag force is introduced Tn the equations of motion for a two-dimensional depth-averaged flow. In the model basin, numerical experiments ave tarried out for the various shape of obstructions, string density and layout of facilities etc.. The flow pattern around the facilities is affected sensitively by the density of string and the layout of facilities. On the other hand, the velocity decay due to the hanging oyster aquaculture facilities is observed in Kamak bay, where the maximum velcocity decay rate is $25\%$ in spring tide. The model is also applied to the field, Kamak bay. The velocity decay rate in the model is comparable with the field measurement data. The velocity decreases around the down-stream area of the facilities, .hut it increases in the other region. The water elevation decreases during the flood and it increases during the ebb.

• 소성∙가공
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• 제26권6호
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• pp.341-347
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• 2017

Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to produce multi-curvature surfaces by controlling strain distribution along longitudinal direction. Reconfigurable rollers could be arranged to implement a kind of punch die set. By utilizing these reconfigurable rollers, desired curved surface can be formed. In FRRF process, three-dimensional surface is formed from two-dimensional curve. Thus, it is difficult to predict the forming result. In this study, a regression analysis was suggested to construct a predictive model for a longitudinal curvature of FRRF process. To facilitate investigation, input parameters affecting the longitudinal curvature of FRRF were determined as maximum compression value, curvature radius in the transverse direction, and initial blank width. Three-factor three-level full factorial experimental design was utilized and 27 experiments using FRRF apparatus were performed to obtain sample data of the regression model. Regression analysis was carried out using experimental results as sample data. The model used for regression analysis was a quadratic nonlinear regression model. Determination factor and root mean square root error were calculated to confirm the conformity of this model. Through goodness of fit test, this regression predictive model was verified.