Song-Yop Hahn

A study on comparison of optimization performances between immune algorithm and other heuristic algorithms

Usefulness of heuristic algorithms as the search method for diverse optimization problems is examined. Immune algorithm (IA), genetic algorithm (GA) and evolution strategy (ES) are used to search the optimal value for some numerical functions. Then those results are compared each other. It is shown that IA is more useful for most of problems. Especially the structure and characteristic of immune algorithm (IA) are inspected in detail. Finally a surface permanent magnet synchronous motor (SPMSM) is designed by using the algorithms.

Topology optimization of electrostatic actuator using design sensitivity

In this paper, a topology optimization approach is used for the design of an electrostatic actuator that can be manufactured using microelectromechanical system (MEMS) technology. The design goal is to obtain constant maximum torque by properly distributing dielectric material in the rotor design space. The objective function is defined for the difference of the system energy to be maximized with respect to the rotation of the rotor. The detailed design with unique rotor pole shape is achieved. Also, the effects of mesh size and initial conditions on final rotor shape are discussed.

A new design technique of magnetic systems using space mapping algorithm

In this paper, a new design method using a space mapping algorithm is presented for the design of magnetic systems. The method mathematically combines the magnetic equivalent circuit method and the finite element method and the optimal design is achieved by employing a quasi-Newton iteration in conjunction with first-order derivative approximations updated by the classic Broyden formula. Therefore, this method can preserve the computational efficiency of the magnetic equivalent circuit method and the accuracy of finite element method. Two numerical examples are tested to prove feasibility and numerical efficiency of the implementation of the proposed design method.

Design sensitivity analysis for nonlinear magnetostatic problems using finite element method

The authors present a sensitivity analysis for the shape design problems of a two-dimensional nonlinear magnetostatic system. In order to derive the design sensitivity, the algebraic equation resulting from the finite element method is exploited and the adjoint variable method is used. This algorithm is applied to the shape design problem of a quadrupole magnet which operates in the magnetic saturation region. Numerical results validate the algorithm. The optimal pole shape with a tolerable deviation is obtained after several iterations. >

Optimal design procedure for a practical induction heating cooker

This paper presents a practical optimal design procedure for small induction heating devices. An experimental modeling of the physical properties and a practical simulation technique for the nonsinusoidal input waveform is adopted. The design sensitivity analysis with Levenberg-Marquardt method is used for the optimal design process. The proposed method is applied to an induction heating pan cooker model, and the result is verified by experiment.

Design of HTS Magnets for a 600 kJ SMES

Development of a 600 kJ Superconducting Magnetic Energy Storage (SMES) system is in progress by Korean Electric Research Institute (KERI). High-temperature superconducting (HTS) wires are going to be used for the winding of the system. The design of the HTS windings for the system is presented in this paper. We considered BSCCO-2223 wire for the HTS windings. The operating temperature of the winding was decided to be 20 K which will be accomplished by conduction cooling method using cryo-coolers. Auto-Tuning Niching Genetic Algorithm was adopted for an optimization method of the HTS magnets in the SMES system. The objective function of the optimal process was minimizing the total amount of the HTS wire. We also estimated the AC loss which can be generated in the discharge period. These HTS windings are going to be applied to the SMES system whose purpose is the stabilization of the power grid

Optimal shape design of microwave device using FDTD and design sensitivity analysis

In this paper, a novel optimal shape design method is proposed using the finite-difference time-domain (FDTD) method and the design sensitivity analysis to obtain broad-band characteristics of microwave devices. In shape design problem, the nodes that describe the shape of geometry to be optimized are taken as design variables. The design sensitivity is evaluated using the adjoint variable equation that is obtained from a terminal-value problem. The adjoint equation can be solved by the FDTD technique with the backward time scheme. With this method, a Ka-band unilateral fin line is tested to show validity.

Implementation of continuum sensitivity analysis with existing finite element code

A numerical implementation of continuum sensitivity analysis in electromagnetic devices is presented, taking advantage of the convenience of existing finite-element codes. The state of adjoint variables are computed by the finite-element codes, and an adjoint load and the sensitivity coefficients are calculated using postprocessing data. Sensitivity evaluation can be performed outside of existing finite-element codes, and it can be implemented without finite-element codes, and it can be implemented without extensive access to the insides of standard finite-element codes. >

Application of vector optimization employing modified genetic algorithm to permanent magnet motor design

This paper presents a method to solve the vector optimization problem that determines both the noninferior solution set and the best compromise solution employing a modified genetic algorithm. The algorithm differs from the conventional one in the definition of fitness value and convergence criterion. Some parameters of the algorithm are adjusted to the vector optimization. The algorithm also contains the additional routine for searching the best compromise solution. This method is applied to the optimal design of the permanent magnet synchronous motor for which two objective functions regarding motor efficiency and weight are used.

Inverse problem application of topology optimization method with mutual energy concept and design sensitivity

In this paper, a new topology optimization technique that incorporates design sensitivity and mutual energy concept is presented and applied to the inverse problem. The sensitivity in each design cell is calculated directly from potential distribution obtained from FEM (finite element method) simulation, and the material property in each cell is changed simultaneously using sensitivity information. The steepest-descent method is used as an optimization technique. The proposed method is applied to a numerical model whose permittivity of the design region is under consideration.