Hee Sung Yoon

Shape Optimization of a Large-Scale BLDC Motor Using an Adaptive RSM Utilizing Design Sensitivity Analysis

This paper proposes a new algorithm for the shape optimization of a large-scale brushless dc (BLDC) motor to reduce the cogging torque. In the algorithm, an adaptive response surface method (RSM) using the multiquadric radial basis function is employed to interpolate the objective function in design parameter space, and incorporated with (1+1) evolution strategy to find an optimal point. In the adaptive RSM, an adaptive sampling point insertion method is developed utilizing the design sensitivities computed by using the finite-element method to get a reasonable response surface with a relatively small number of sampling points. The developed algorithm is applied to the shape optimization of a 5-MW BLDC motor, and the cogging torque was reduced to 17% of the initial one

A Robust and Computationally Efficient Optimal Design Algorithm of Electromagnetic Devices Using Adaptive Response Surface Method

This paper presents a robust and computationally efficient optimal design algorithm for electromagnetic devices by combining an adaptive response surface approximation of the objective function and (1+λ) evolution strategy. In the adaptive response surface approximation, the design space is successively reduced with the iteration, and Pareto-optimal sampling points are generated by using Latin hypercube design with the Max Distance and Min Distance criteria. The proposed algorithm is applied to an analytic example and TEAM problem 22, and its robustness and computational efficiency are investigated.

Shape Optimal Design of a 9-pole 10-slot PMLSM for Detent Force Reduction Using Adaptive Response Surface Method

The detent force of a permanent magnet linear synchronous motor (PMLSM) consists of cogging and drag forces, and should be minimized for high precision purpose application. This paper suggests a new 9-pole 10-slot structure of a short primary PMLSM to remove the cogging force. Through theoretical and finite element analysis, the proposed structure is proven to remove most of the cogging force. The detent force is minimized by optimizing the length of armature core and shape of the exterior teeth simultaneously by using (1+lambda) evolution strategy coupled with response surface method using multi-quadric radial basis function. Additionally, simulation results for the proposed structures are verified by experimental measurements.

A Novel Optimal Design Method of Passive Shimming for Permanent MRI Magnet

In magnetic resonance imaging (MRI) magnets, field shimming technique is, in general, necessary to increase the field homogeneity in imaging region to an acceptable level after manufacturing. This paper presents a novel passive shimming method using permanently magnetized shimming pieces. In the method, the shimming design is modeled as an integer programming problem, and the distribution of shimming pieces is optimized. Through an application to a 0.3-T permanent magnet MRI system, the optimally designed shimming pieces are proven to improve the field homogeneity from 1456 to 784 ppm after just one iteration of shimming courses is carried out.

Analysis of Parameters Influence on the Characteristics of Thomson Coil Type Actuator of Arc Eliminator Using Adaptive Segmentation Equivalent Circuit Method

A Thomson coil type actuator is applied as the driving unit in an arc eliminator system. To eliminate the arc efficiently, the speed of the actuator is required as fast as possible with certain limit of the exciting current. Therefore, the dynamic characteristics of the Thomson coil type actuator should be analyzed in an effective way. In this paper, a novel solving technique has been developed based on the equivalent circuit model which is set up by dividing the conducting plate into multi segments. To guarantee the calculation accuracy and improve the calculation efficiency, an adaptive refinement algorithm is suggested based on the field continues condition. The proposed method has been verified by the FEM calculation and experiment. The influence of circuit and plate parameters to the performance of the actuator is also investigated, from which a reasonable set of parameters can be found.

Comparison of Magnetic Reluctivity Models for FEA Considering Two-Dimensional Magnetic Properties

An improved magnetic reluctivity model is developed to describe two-dimensional magnetic properties of anisotropic material. In this model, the behavior of magnetic field intensity is explained in terms of magnitude and direction of magnetic flux density, and reluctivity tensor always has zero off-diagonals. The proposed reluctivity model is incorporated into nonlinear finite element formulation using Newton-Raphson method, and applied to magnetic field analysis of a single-phase transformer core model. By comparing the analyzed B -waveforms with experimental ones, the effectiveness of the proposed reluctivity model and FE formulation is investigated.

New Development of Monohedral Magnet for MRI Using the Combination of Genetic Algorithm and FEM-NESM

A novel monohedral permanent magnet (PM) configuration is suggested and geometrically optimized to have higher magnetic efficiency as well as higher degree of access to imaging region of a magnetic resonance imaging (MRI) system. The configuration has a pair of main PMs magnetized in the opposite directions, respectively. The geometry of the main PMs is optimized by using genetic algorithm combined with a novel flexible magnetic field analysis method which combines finite-element method and new-type equivalent source method. Through an optimal design, the suggested PM configuration is proven to provide a sufficiently homogeneous and strong magnetic field for MRI application.

Multi-Objective Optimal Design of a Single Phase AC Solenoid Actuator Used for Maximum Holding Force and Minimum Eddy Current Loss

A new Pareto-optimal design algorithm, requiring least computational work, is proposed for a single phase AC solenoid actuator with multi-design-objectives: maximizing holding force and minimizing eddy current loss simultaneously. In the algorithm, the design space is successively reduced by a suitable factor, as iteration repeats, with the center of pseudo-optimal point. At each iteration, the objective functions are approximated to a simple second-order response surface with the CCD sampling points generated within the reduced design space, and Pareto-optimal solutions are obtained by applying (1+λ) evolution strategy with the fitness values of Pareto strength.

Finite element analysis of a very large-scale permanent magnet BLDC motor considering two-dimensional magnetic properties of electrical steels

In this paper, a novel finite element analysis taking account of two-dimensional magnetic properties of non-oriented electrical steel sheet is suggested and applied to performance analysis of a large-scale permanent magnet brushless DC motor. The magnetic properties of non-oriented silicon steel (50A1300) is measured by two-dimensional single sheet tester, and modeled by using extended B-H curve method for non-linear finite element analysis. Through the suggested finite element analysis, the performance such as iron loss and cogging torque is analyzed and compared with numerical results from conventional analysis method.

Analysis of magnetic characteristic in the three-phase transformer core considering two-dimensional magnetic anisotropic property

This paper presents a magnetic reluctivity tensor model considering the two-dimensional magnetic anisotropy of the Grain-oriented electrical steel sheet from the point of view of numerical implementation, in which the behavior of magnetic field intensity is explained in terms of magnitude and direction of magnetic flux density, and reluctivity tensor is derived into zero off-diagonals. The finite element formulation for considering the magnetic reluctivity tensor model is also derived. The model is applied to finite element analysis of transformer cores and the computed results are compared with traditional anisotropic model.