Seung Geon Hong

Adaptive level set method for accurate boundary shape in optimization of electromagnetic systems

Purpose – The purpose of this paper is to present a new numerical technique, called adaptive level set method, for use with the finite element method. Design/methodology/approach – A conventional level set method using the smeared Heaviside function has been employed for shape and topology optimizations. The smeared Heaviside function yields an indistinct interface boundary, and so can increase computational time and cause numerical errors. The adaptive level set method does not use the smeared Heaviside function. To coincide with the material interface, it processes the zero level as the boundary data of element meshing. Findings – Usefulness and accuracy of shape optimization using the adaptive level set method are shown by comparison to the conventional level set method. A shape optimization procedure using the adaptive level set method is introduced. Numerical examples are employed to explain how the adaptive level set method is applied. Originality/value – The adaptive level set method is proposed to...

Alleviation of Electric Field Intensity in High-Voltage System by Topology and Shape Optimization of Dielectric Material Using Continuum Design Sensitivity and Level Set Method

A new design method for topology and shape optimization to preserve high-voltage systems is proposed. The level set technique for the topology optimization is employed with the finite-element method. For the velocity field in the level set equation, the continuum sensitivity formula is used for accurate information of the electric field effect on the topology and shape variation. This technique is applied to three practical examples and the optimum designs of insulating dielectric for the systems are obtained. The optimum designs could suppress troubles, such as thermal deterioration or electrical breakdown, in the systems.

Hole Sensitivity Analysis for Topology Optimization in Electrostatic System Using Virtual Hole Concept and Shape Sensitivity

In this paper, the hole sensitivity analysis is proposed for topology optimization in the electrostatic system. The hole sensitivity formula is derived using the virtual hole concept and the continuum shape sensitivity. Since the derived formula is expressed as a closed form, it is simple and easy to implement and apply to real problems. The hole sensitivity analysis provides information for topology variation. The geometrical expression of the topology variation is obtained using the level set method. Two numerical examples are tested to show the usefulness of the hole sensitivity analysis.

Derivation of Hole Sensitivity Formula for Topology Optimization in Magnetostatic System Using Virtual Hole Concept and Shape Sensitivity

In this paper, hole sensitivity formula is analytically derived for topology optimization in magnetostatic system. With the concept of virtual hole, the hole sensitivity is obtained using continuum shape sensitivity. To demonstrate the validity of the hole sensitivity, topology optimization of synchronous reluctance motor is tested. Since the hole sensitivity formula is represented only with electromagnetic field, it is easily implemented for topology optimization.

Shape and topology optimization of rotor in synchronous reluctance motor using continuum sensitivity and adaptive level set method

In this paper, the rotor shape of synchronous reluctance motor (SynRM) is designed using the sensitivity analysis along with the level set method. To reduce numerical errors of sensitivity value on the interface, the adaptive level set method is adopted. The rotor shape of the SynRM is designed to maximize average torque or to minimize cogging torque by distributing the ferromagnetic material over the design domain of the rotor.

Numerical Analysis and Experiment of Floating Conductive Particle Motion Due to Contact Charging in High-Voltage System

In this paper, the motion of conductive particles is modeled and analyzed using a coupled equation. A neutral conductive particle obtains charge when it comes into contact with an electrode. The forces acting on a particle consist of electric, drag, and gravitational forces. When the electric force is dominant over the other forces, a particle lifts up toward the upper electrode. The electric force on a particle is calculated using surface charge distribution, which is analyzed using the finite-element method. The dominant forces on the particles are used as a driving force in Newtons motional equation to analyze a particle motion. The analysis results show that the total charge, which enables the particle to lift off, is calculated using the coupled equation with respect to the applied voltage. The experiment using a spherical conductive particle is conducted, and the experiment result is compared with the numerical one to validate the numerical method.

Adaptive Level Set Method for Finite Element Model of Geometrically Evolving Electromagnetic Systems

We present a new numerical technique of adaptive level set method coupled with the finite element method. A conventional level set method with the smeared Heaviside function has been employed for electromagnetic topology optimization. However, the smeared Heaviside function can yield vague interface boundary and numerical error. The proposed adaptive method does not use the smeared Heaviside function but it processes the zero level set as the boundary data of element meshing in order to coincide with the material interface. The adaptive level set method is shown to be useful and accurate in comparison with the conventional method.

Design of contactless inductive energy transmission systems with large air-gap

A contactless inductive energy transmission system (CIETS) transmits electric energy via a alternating magnetic field through an air-gap. In contrast to a non air-gap energy transmission system, the power capacities per frequency of the primary and secondary sides in a CIETS are different. Therefore, a new method is needed for designing a CIETS that has an asymmetric structure. In this paper, we propose a new design method to improve the efficiency of CIETSs by increasing the coupling coefficient. Core shape is an important parameter to be optimized in order to increase the coupling coefficient. Several core shapes are analyzed by a finite element method (FEM). Calculated coupling coefficients are compared to determine the optimal core shape design.

Dot Sensitivity Analysis for Topology Optimization of Dielectric Material in Electrostatic System

In this paper, a dot sensitivity analysis is proposed for the topology optimization of dielectric materials in an electrostatic system. Dot sensitivity formula is analytically derived in closed form using the continuum shape sensitivity formula. The level set method is used for evolving the geometry in the topology optimization. As the dot sensitivity analysis can generate new material in a vacant region, it does not require an initial design for the dielectric material and widens the design space. Two numerical examples are tested to show the usefulness of dot sensitivity analysis.

Dot sensitivity analysis for topology optimization of dielectric material in electrostatic system

This paper proposes a dot sensitivity analysis for topology optimization of dielectric material in the electrostatic system. A dot sensitivity formula derived as a closed form is coupled to the level set method. Since the dot sensitivity analysis can generate a new material in a vacant region, it does not only require the initial design of the material, but also can generate diverse topologies. Numerical models are tested to show the usefulness of the dot sensitivity analysis.