• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.9 s.240
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• pp.1243-1252
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• 2005

A current trend of design methodologies is to make engineers objectify or automate the decision-making process. Numerical optimization is an example of such technologies. However, in numerical optimization, the uncertainties are uncontrollable to efficiently objectify or automate the process. To better manage these uncertainties, the Taguchi method, reliability-based optimization and robust optimization are being used. To obtain the target performance with the maximum robustness is the main functional requirement of a mechanical system. In this research, a design procedure for global robust optimization is developed based on the kriging and global optimization approaches. The DACE modeling, known as the one of Kriging interpolation, is introduced to obtain the surrogate approximation model of the function. Robustness is determined by the DACE model to reduce real function calculations. The simulated annealing algorithm of global optimization methods is adopted to determine the global robust design of a surrogated model. As the postprocess, the first order second-moment approximation method is applied to refine the robust optimum. The mathematical problems and the MEMS design problem are investigated to show the validity of the proposed method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.2
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• pp.83-91
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• 2003

Pantograph design Process must be considered in terms of stability of aerodynamics and reduction of aeroacoustics. Furthermore pantograph needs to be insensible to severe circumstance condition like typhoon, tunnel, a change of season. In this paper, robust design of panhead sections is conducted based on the Taguchi's design of experiment method. In the aeroacoustic noise analysis, an acoustic analogy using the Ffowcs Williams and Hawkings(FW-H) equation is used to calculate the flow induced sound pressure level in aeroacoustics. From the near-field CFD analysis data, the far-field noise is predicted at the positions of 25 m away from Pantograph. Based on aerodynamic(CFD) and aeroacoustic(FW-H) analysis data, the optimal sizing and Positioning of panhead elements are determined using robust design optimization method. Design parameters such as thickness, length and radius are controllable factors, while outdoor air temperature and atmospheric pressure are considered as uncontrollable factors in the context of Taguchi's approach. A number of CFD simulation and aeroacoustic analysis are performed based on orthogonal arrays. In this paper, two-step optimization method is used as a parameter design procedure. It is executed using signal to noise(S/N) ratio and analysis of means(ANOM) method. So Thus, an optimal level of design parameters Is extracted to minimize the disconnection ration between contact strips and catenary system, and reduce the far-field aeroacoustic noise.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.6
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• pp.73-81
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• 2014

In this paper, multiple gate locations and process conditions under concern are automatically optimized by considering robustness to minimize the injection pressure required to mold an automotive dashboard. Computer simulation-based experiments using orthogonal arrays(OA) and a design-range reduction algorithm are consolidated into an iterative search scheme, which is then used as a tool for the optimization process. The robustness of a design is evaluated using an OA-based simulation of process fluctuations due to noise as well as the signal-to-noise ratio. The optimal design solution for the automotive dashboard shows that the robustness of the injection pressure is significantly improved when compared to the initial design. As a result, both the die clamping force and the pressure distribution in the part cavity are also much improved in terms of their robustness.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1235-1241
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• 2001

Pantograph design process must be considered in terms of stability of aerodynamics and reduction of aeroacoustics. Furthermore Pantograph needs to be insensible to severe circumstance condition like typhoon, tunnel, a change of season. In this paper, robust design of panhead sections is conducted based on the Taguchi's design of experiment method. In the aeroacoustic noise analysis, an acoustic analogy using the Ffowcs Williams and Hawkings (FW-H) equation is used to calculate the flow induced sound pressure level. From the near-field CFD analysis data, the far-field noise is predicted at the positions of 25m away from panhead contact strips. Based on aerodynamic (CFD) and aeroacoustic (FW-H) analysis data, the optimal sizing and positioning ofpanhead elements are determined using robust design optimization method. Design parameters such as thickness, length and radius are controllable factors, while outdoor air temperature and atmospheric pressure are considered as uncontrollable factors in the context of Taguchi's approach. A number of CFD simulation and aeroacoustic analysis are performed based on orthogonal arrays. Using a parameter design procedure associated with signal-to-noise (SIN) ratio and sensitivity analysis, an optimal level of design parameters are extracted to minimize the disconnection ratio between contact strips and catenary system, and reduce the far-field aeroacoustic noise.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.2
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• pp.99-104
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• 2008

This study performed robust design optimization of fighter wing planform, considering uncertainty based on neural network model. To construct uncertainty model, aerodynamic performance and their sensitivity were evaluated by 3-dimensional Euler equations and adjoint variable method at experimental points selected from central composite design. In addition, because a neural network model has the advantage of capturing non-linear characteristic, it was possible to predict sensitivity of the aerodynamic performance efficiently and accurately . From the results of robust design optimization, it could be confirmed that the robustness of the objective function and constraints were improved if the variation of uncertainty and sigma level were increased.

• Journal of KSNVE
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• v.6 no.1
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• pp.35-44
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• 1996

This paper presents a new type of fuzzy-sliding mode controller for robust tip position control of a single-link flexible manipulator subjected to parameter variations. A sliding mode controller is formulated with an assumption that imposed parameter variations are bounded so that certain deterministic performance can be guaranted. In the design of the sliding mode controller, so called moving sliding surface is adopted to minimize the reaching phase and thus mitigate system sensitivity to the variations. The sliding mode controller is then incorporated with a fuzzy technique to reduce inherently ever-existing chattering which is impediment in position control of flexible manipulators. A set of fuzzy parameters and control rules are obtained from a relation between predetermined sliding surface and representative points in the state space. Computer simulations are undertaken in order to demonstrate superior control performance of the proposed methodology.

• Explosives and Blasting
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• v.31 no.2
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• pp.1-5
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• 2013

Parameters of Swedish bench blast design was analyzed by robust design method. Orthogonal array which is adopted in this study was $L_9(3^4)$ and the parameters were hole diameter, explosive type, hole inclination and rock factor of 3 levels. Result of analysis showed that maximum and minimum burden are most affected by hole diameter, followed by explosive type, rock type and inclination of hole. Parameters affecting specific charge are in the order of rock type, explosive type and to specific drilling are hole diameter and explosive type. Cost analysis showed that robust design is capable of parameter optimization.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.3
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• pp.41-49
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• 1999

In this paper, we design a controller using the $\mu$-synthesis method and apply it for the spring-mass system with noncollocated sensors and actuators. We assume that the values of the spring stiffness and load mass of the plant are uncertain. The plant is modeled with parametric uncertainty by using the state space equation, especially the descriptor form. The $H_\infty$ controller designed by the $\mu$-synthesis method is compared with the standard $H_\infty$ controller To compare performances of two $H_\infty$ controllers, it is assumed that both controllers were designed with same weighting functions except that the $\mu$-synthesis controller has structured uncertainties. By compared with the standard $H_\infty$ controller, we show that the designed controller has satisfactory robust performance as well as robust stability by simulations and experiments.

• The Korean Journal of Applied Statistics
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• v.20 no.2
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• pp.267-280
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• 2007

Various single-valued design optimality criteria such as D-, G-, and V-optimality are used often in constructing optimal experimental designs for mixture experiments in a constrained region R where lower and upper bound constraints are imposed on the ingredients proportions. Even though they are optimal in the strict sense of particular optimality criterion used, it is known that their performance is unsatisfactory with respect to the prediction capability over a constrained region. (Vining et at., 1993; Khuri et at., 1999) We assume the quadratic polynomial model as the mixture response surface model and are interested in finding efficient designs in the constrained design space for a mixture. In this paper, we make an expanded list of candidate design points by adding interior points to the extreme vertices, edge midpoints, constrained face centroids and the overall centroid. Then, we want to propose a robust design with respect to D-optimality, G-optimality, V-optimality and distance-based U-optimality. Comparing scaled prediction variance quantile plots (SPVQP) of robust designs with that of recommended designs in Khuri et al. (1999) and Vining et al. (1993) in the well-known examples of a four-component fertilizer experiment as well as McLean and Anderson's Railroad Flare Experiment, robust designs turned out to be superior to those recommended designs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.5
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• pp.914-923
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• 2002

Recently, there has been considerable interest in micro gyroscopes made of silicon chips. It can be applied to many micro-electro-mechanical systems (MEMS): devices for stabilization, general rate control, directional pointing, autopilot systems, and missile control. This paper shows how the mechanical design of the gyroscope can be done using axiomatic design, followed by the application of the Taguchi robust design method to determine the dimensions of the parts so as to accommodate the dimensional variations introduced during manufacturing. Functional requirements are defined twofold. One is that the natural frequencies should have fixed values, and the other is that the system should be robust to large tolerances. According to the Independence Axiom, design parameters are classified into a few groups. Then, the detailed design process is performed fellowing the sequence indicated by the design matrix. The dimensions of the structure are determined to have constant values fur the difference of frequencies without consideration of the tolerances. It is noted that the Taguchi concept is utilized as a unit process of the entire axiomatic approach.