• Journal of Advanced Marine Engineering and Technology
• /
• v.11 no.3
• /
• pp.61-69
• /
• 1987

The PID controller is one of the most popular devices for control systems and the adjustment of its parameters has been generally accomplished by semi-empirical rules and has been considered only in the view of improvement of the control performance. But in modern control theory, a quadratic form is introduced as a criterion function which considers not only to improve quality of control but also to save energy required for the control. In this paper, authors propose a method of the parameter adjustment of the PID controller by means of maximum principle minimizing the quadratic criterion function and establish a link between the conventional parameter adjustment method and the technique of the modern optimal control theory in the design of a PID controller.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.55 no.7
• /
• pp.369-373
• /
• 2006

In this paper, an optimal method for determining design parameters of a Switched Reluctance Motor is researched. The dominant design parameters are stator and rotor pole arc and switching on and off angle. The parameters affecting performance are examined and selected using evolutionary computations and commercial CAD program. The simulated design method is compared with conventional procedure.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.21 no.2
• /
• pp.35-47
• /
• 1996

The tolerance approach to the sensitivity analysis in linear programming considers simultaneous and independent variations in the coefficients of the objective function or of the right-hand side terms and gives a region in which the coefficients and terms can be changed and still keeps the current optimal basis B for the original problem as an optimal basis for the perturbed problem. In this paper we describe a procedure that expands the region S obtained by the tolerance approach into a larger region R, so that more variations in the objective function coefficients or the right-hand side terms are permissible.

• Management Science and Financial Engineering
• /
• v.16 no.1
• /
• pp.81-117
• /
• 2010

Semi-supervised learning incorporates unlabeled examples, whose labels are unknown, as well as labeled examples into learning process. Although transductive support vector machine (TSVM), one of semi-supervised learning models, was proposed about a decade ago, its application to large-scaled data has still been limited due to its high computational complexity. Our previous research addressed this limitation by introducing a branch-and-bound algorithm for finding an optimal solution to TSVM. In this paper, we propose three new techniques to enhance the performance of the branch-and-bound algorithm. The first one tightens min-cut bound, one of two bounding strategies. Another technique exploits a graph-based approximation to a support vector machine problem to avoid the most time-consuming step. The last one tries to fix the labels of unlabeled examples whose labels can be obviously predicted based on labeled examples. Experimental results are presented which demonstrate that the proposed techniques can reduce drastically the number of subproblems and eventually computational time.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.386-386
• /
• 2000

Cell mapping is a powerful computational technique for analyzing the global behavior of nonlinear dynamic systems. It simplifies the task of analyzing a continuous phase space by partitioning it into a finite number of disjoint cells and approximating system trajectories as cell transitions. A cell map for the system is then constructed based on the allowable control actions. Next search algorithms are employed to identify the optimal or near-optimal sequence(s) of control actions required to drive the system from each cell to the target cell by an "unravelling algorithm." Errors resulting from the cell center-point approximation could be reduced and eliminated by fuzzifying the bonders of cells. The dynamic system control method based on the cell mapping has been demonstrated for a motor control problem.l problem.

• Journal of Institute of Control, Robotics and Systems
• /
• v.7 no.4
• /
• pp.319-325
• /
• 2001

Recently. AGV systems are used to serve the raw material to each work stations automatically. There exists a trade-off between the adequate service supply and the number of purchased AGVs. Also, to reduce the overall production cost, the amount of inventory hold on the shop floor should be considered. In this paper, we present a heuristic technique for determining the number of AGVs which includes the net present fixed costs of each station, each purchased AGV, delivering cost, stock inventory cost, and safety stock inventory cost. Secondly, by using a genetic algorithm, the optimal number of AGVs and the optimal reorder quantity at each station are decided. Lastly, to verify then heuristic algorithm, we have done a computer simulation with different GA parameters.

• Applied Microscopy
• /
• v.46 no.3
• /
• pp.164-166
• /
• 2016

Electron channeling contrast imaging (ECCI) is a powerful analyzing tool for identifying lattice defects like dislocations and twin boundaries. By using diffraction-based scanning electron microscopy technique, it enables microstructure analysis, which is comparable to that obtained by transmission electron microscopy that is mostly used in defect analysis. In this report, the optimal conditions for investigating crystal defects are suggested. We could obtain the best ECCI images when both acceleration voltage and probe current are high (30 kV and 20 nA). Also, shortening the working distance (6 mm) enhances the quality of defect imaging.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.548-554
• /
• 1996

A new method to locate modular fixtures using an optimization technique is proposed. The optimal fixture arrangement is derived to minimize the elastic deformation of a workpiece. That is, a fixture arrangement is regarded better if it minimized the elastic deformation of the workpiece while fixing a workpart of course. In this approach, the workpiece is projected into two dimensional domain to simplify the 3-dimensional fixture arrangement problem into 2-dimensional one. Thus the problem is reduced to find the optimal positions of one horizontal clamp and three locators which minimize the total deformation of the workpiece and the design variables are the location of the contact points between the boundary of the workpiece and the 4-fixels. The Genetic Algorithm is used for the optimization by mapping each design variables to a gene of a chromosome. The fitness value is the total strain energy of the workpiece calculated by the fin element analysis.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.4 s.97
• /
• pp.116-121
• /
• 1999

At the exit stage of drilling, the burr generates and deburring process is required to remove it. Since the additional process reduces productivity, a burr minimization technique is necessary in the servo system of drilling machines. In this research, cutting force is modelled with tool geometry and the optimal velocity profile with which the desired cutting force maintains is generated to minimize burr. Experiments show that the proposed velocity profile tracking effectively minimizes burr compared to the constant velocity feed.

• Journal of Korean Society for Quality Management
• /
• v.27 no.2
• /
• pp.218-236
• /
• 1999

The purpose of parameter design is to determine optimal settings of design parameters of a product or a process such that the performance characteristics of a product exhibit small variabilities around their target values. Taguchi made significant contributions in this area. However, his analysis of the problem focused on only one performance characteristic or response, although in product and process design, multiple characteristics are more common. The critical problem in dealing with multiple characteristics is how to compromise the conflict among the selected levels of the design parameters for each individual characteristic. In this paper, Methodology using SN ratio optimized by univariate technique is proposed and a parameter design procedure to achieve the optimal balance among several different response variables is developed. Existing case studies are solved by the proposed method and the results are compared with ones by the sum of SN ratios, the expected weighted loss, the desirability function, and EXTOPSIS model.