Il-Han Park

Topology optimization of electrical devices using material energy and sensitivity

This paper presents a new topology optimization technique for electromagnetic problems. Mutual energy terms are defined in the electromagnetic system, and the objective function that represents the design objective is expressed in terms of mutual energy. The design sensitivity is calculated from the first variation of mutual energy and the density method is used to optimize the material property distribution in the design region using the obtained sensitivity. The proposed algorithm is applied to a numerical example of transformer core topology optimization and verified.

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.

Optimal shape design of iron core to reduce cogging torque of IPM motor

This paper presents a practical design method to dramatically reduce cogging torque of an interior permanent-magnet (IPM) motor without deteriorating other performances. Using the continuum sensitivity analysis combined with the finite-element method (FEM), the optimal shape of a rotor is investigated. The Lagrange sliding interface technique and an objective function expressed in terms of stored system energy allow fast convergence and simple implementation of the optimization algorithm. Experimental results show that the proposed method is very effective in suppressing the cogging torque of an IPM motor.

Minimization of higher back-EMF harmonics in permanent magnet motor using shape design sensitivity with B-spline parameterization

This paper presents a shape optimal design method for reducing the higher back-EMF harmonics generated in the permanent magnet motors, in which torque ripples could occur. The continuum shape design sensitivity formula and the finite element method are employed to calculate the sensitivity of flux-linkage to the design variables, which determine the shape of iron pole piece. The design variables are optimized with a B-Spline parameterization in order to provide the back-EMF waveform as close as possible to a sinusoidal form. The design algorithm is applied to a three-phase interior permanent magnet motor that contains a mount of higher back-EMF harmonics.

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. >

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.

Comparison of mechanical deformations due to different force distributions of two equivalent magnetization models

In magnetic systems, electromagnetic force density distribution may cause mechanical deformation, which results in the mechanical noise and vibration. The electromagnetic force density can be analyzed with several techniques such as stress tensors, equivalent magnetization models and energy approaches and etc. that may produce different force densities. From the view-point of mechanical deformation, they are theoretically analyzed and compared to explain the differences between the force fields using the property of scalar pressure. In uncompressible media the gradient of scalar pressure, which is a term of Korteweg-Helmholtz force density, does not cause any mechanical deformation. In this paper, two magnetization source models of magnetic charge and magnetization current, which produce quite different distributions of force density, are employed to see their mechanical deformations. Three numerical examples are tested to examine their validity and usefulness.

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

In order to obtain broadband characteristics of passive microwave device, we propose an optimal shape design method in this paper. The proposed method utilizes the FDTD technique based on the design sensitivity analysis (DSA). In DSA, a sensitivity is evaluated by solving the adjoint variable equation derived from a terminal value problem using the FDTD method with proper terminal conditions. As a two-dimensional design example, an E-plane horn antenna is tested to show the validity of the proposed method.