• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.31-38
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• 2004

Mechanical design process is generally accomplished by design, analysis, and test. Designers use programs fitting purpose, and obtain repeatedly a response of a simulation program, a sub-program for optimization. In this paper, shape optimization using approximate optimization technique is carried out with sequential design domain(SDD). In addition, algorithm executing Pro/Engineer and ANSYS automatically are adopted in the approximate optimization program by SDD. It is difficult for design problem to be approximated accurately for the whole range of design space. However, more or less accurate approximation is constructed if SDD is applied to that case. SDD starts with a certain range which is off-seted from midpoint of an initial design domain and then SDD of the next step is determined by a move limited. Convergence criterion is defined such that optimal point must be located within SDD during the two steps. Also, the PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm is used to solve approximate optimization problems. This algorithm uses the second-order information and the active set strategy, in order to seek the direction of design variables.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.3
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• pp.437-443
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• 1987

An optimal design to improve the ride quality was performed with the time and frequency domain analysis based on both of deterministic and random road profiles. The objective function is established to minimize the absorbed power while the constraints are taken so as to satisfy the condition for the stability of vehicle. The result of the optimal design shows that the rms for the acceleration of a driver and his seat is within the critical values for the ride quality from ISO. The optimal values obtained show that the maximum absolute acceleration of the driver and his seat has significantly been reduced and the reference limits on the relative displacement have satisfied their feasibility. As the optimal value according to a specific speed is the results from the optimization process, a global optimum value should be determined to be the one which gives th minimum values of total sum of absorbed power with respect to various speed.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.2
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• pp.170-177
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• 1998

In this paper, a unified solution of Hankel norm approximation problem is proposed by $\delta$-operator. To derive the main result, all-pass property is derived from the inner and co-inner property in the $\delta$-domain. The solution of all-pass becomes an optimal Hankel norm approximation problem in .delta.-domain through LLFT(Low Linear Fractional Transformation) inserting feedback term $\phi(\gamma)$, which is a free design parameter, to hold the error bound desired against the variance between the original model and the solution of Hankel norm approximation problem. The proposed solution does not only cover continuous and discrete ones depending on sampling interval but also plays a key role in robust control and model reduction problem. The verification of the proposed solution is exemplified via simulation for the zero-order Hankel norm approximation problem and the model reduction problem applied to a 16th order MIMO system.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.2
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• pp.144-155
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• 1992

A design of a highly stable current-controlled power supply combining the phase-controlled rectifier (PCR), passive filter and active filter is investigated. A digital phase-looked voltage control (PLVC) with a capability of compensating the thyristor firing angles under unvalanced power source is proposed` otherwise the PCR output voltage has low-order subharmonics whose suppression requires a bulky passive filter. The digital PLVC has a fast dynamic characteristics as an inner control loop of the PCR. To suppress further the output ripple, an active filter using a transformer is introduced and its design is described through the frequency domain analysis. An optimal integral, proportional and measurable variable feedback (IPM) controller is designed using the time-weighted performance index based on the time domain analysis. The design method based on the time-weighted performance index gives better response characteristics than that based on the conventional performance index. It is also shown via experimental results that the proposed scheme gives better response characteristics than that based on the conventional performance index. It is also shown via experimental results that the proposed scheme gives good dynamic and static performances.

• Steel and Composite Structures
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• v.21 no.6
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• pp.1389-1410
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• 2016

This paper proposes a hybrid of topological derivative-based level set method (LSM) and isogeometric analysis (IGA) for structural topology optimization. In topology optimization a significant drawback of the conventional LSM is that it cannot create new holes in the design domain. In this study, the topological derivative approach is used to create new holes in appropriate places of the design domain, and alleviate the strong dependency of the optimal topology on the initial design. Furthermore, the values of the gradient vector in Hamilton-Jacobi equation in the conventional LSM are replaced with a Delta function. In the topology optimization procedure IGA based on Non-Uniform Rational B-Spline (NURBS) functions is utilized to overcome the drawbacks in the conventional finite element method (FEM) based topology optimization approaches. Several numerical examples are provided to confirm the computational efficiency and robustness of the proposed method in comparison with derivative-based LSM and FEM.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.897-899
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• 2004

There is scientific work containing the recurrence method of synthesis the new class of orthogonal circle m-invariant signals: designed effective algorithms of fast-direct computing m-convolution in time domain: engineer methods of design economic scheme of decoders for optimal receiving in aggregate of suggested signal.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.327-330
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• 2003

This paper presents an optimal robust LQ-PID controller design method for the second-order system with both small state delay and small input delay to satisfy the design specifications in time domain. The modified sensitivity approach method is considered for its optimization.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.365-370
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• 2001

In order to minimize unstable flow occurred at a multiblade fan/scroll system, optimal angle and shape of cut-off was determined by using two-dimensional turbulent fluid field analyses and neural network. The results of CFD analyses were used for learning as data of input and output of neural network. After learning neural network optimization process was accomplished for design variables, the angle and the shape of cut-off, in the design domain. As a result of optimization, the optimal angle and shape were obtained as 71 and 0.092 times the outer diameter of impeller, respectively, which are very similar values to previous studies. Finally, it was verified that the fluid field is very stable for optimal angle and shape of cut-off by two-dimensional CFD analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.6
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• pp.656-666
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• 1999

In this paper, we design the optimal PD control system which has the robust performance. This PD control system is designed by applying genetic algorithm (GA) to the determination of proportional gain KP and derivative gain KD that are given by PD servo controller, to make the output of plant follow the output of reference model optimally. These proportional and derivatibe gains are simultaneously optimized in the search domain guaranteeing the robust performance of system. And, this PD control system is compared with $\mu$ -synthesis control system for the robust performance. The PD control system designed by the proposed method has not only the robust performance but also the better command tracking performance than that of the $\mu$ -synthesis control system. The effectiveness of this control system is verified by computer simulation.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.2
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• pp.234-234
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• 1999

The aim of this paper is to suggest a design method of the optimal model following control system using genetic algorithm (GA). This control system is designed by applying GA with reference model to the optimal determination of weighting matrices Q, R that are given by LQ regulator problem. The method to do this is that all the diagonal elements of weighting matrices are optimized simultaneously by GA, in the search domain selected adequately. And we design the model following control system to boi1er-turbine equipment by the proposed method. The model following control system designed by this method has the better command tracking performance than that of the control system designed by the trial-and-error method. The effectiveness of this control system is verified by computer simulation.