Some articles that concern simulation and optimization for electromagnetism and mechanics are introduced. Many technologies on them, for example, large scale simulation, coupled simulation, and topology optimization in design are extremely progressing. Model sizes for simulation and optimization are becoming larger and larger with increasing computer performance. Therefore, useful design information can be obtained. In addition, design tools which can get solution to make a decision for design easily and quickly in early design stage are also progressing. Many simulation and optimization tools are widely diffused in designing machines. It is important for good design to select and use suitable tools.
Numerical simulation of electromagnetic field is widely used for the optimal design of electric apparatus in the field of the research and development. In particular, the magnetic field analysis using the three-dimensional finite element method (3-D FEM) has been made progress steadily. This paper describes the outline of the magnetic field analysis based on the 3-D FEM in recent years, and the numerical simulation combined with several equations.
When a train runs through a tunnel, pressure variation and train draft are generated in the tunnel, and air temperature in the tunnel rises by running resistance. For the design of structures in a tunnel and for the protection of electric instruments in a tunnel, it is necessary to estimate the pressure variation, the flow velocity and the air temperature. For this purpose, we have developed a numerical simulation program for predicting the pressure variations, the flow velocity, and the air temperature in a railway tunnel. In this paper, calculation method and results of their verification by experiments are presented.
This paper reports the state-of-the-art of optimization methods based on computational electromagnetism. This paper describes genetic algorithm which has widely been used for optimization of electromagnetic devices and machines, hierarchical voxel finite element method suitable for parameter optimization, single and multi-objective parameter optimizations, topology optimizations using the level-set method coupled with GA-based ON-OFF method, and NGnet-based topology optimization, and robust optimization.
In this paper, optimization technique of mechanical structures is explained focusing on topology optimization. Since holes can be generated inside objects, the flexibility of topology optimization is higher than that of size optimization and shape optimization. The feature and formulation of topology optimization are described. In topology optimization, the problem which should be solved is transformed from the moving boundary line problem to the material density distribution problem in the extended fixed design domain. The characteristic function corresponding to existence of material is introduced. In order to avoid the discontinuity of the characteristic function and to obtain sensitivity, relaxation of design variables is performed. As the practical example, the block configuration optimization of XY-stage plate model composed of four types of ceramics block is conducted. As a result, the optimal block configurations are obtained in a realistic time scale for each volume constraint ratio.
This paper represents the research finding of wireless electric power transmission using same or different outer diameter flat spiral coil. The coupling factor, transmission power and transmission efficiency of asymmetrical coil which has same inner diameter but different turn numbers was compared with symmetrical coil which has same inner diameter and same turn numbers. In the application of wireless electric power transmission for electric assisted bicycles, small size diameter coil (less than ø10 cm) is more suitable than large size diameter coil (larger than ø50 cm), therefore, a small size coil is used. In the results, an electric power transmission by using asymmetrical coil was found the same as that of symmetrical coil. However, the distance for power transmission by asymmetrical coil was found smaller than symmetrical coil. When a secondary battery was connected with wireless power transmission as a load, the apparent resistance of secondary battery had influence on charging rate. This resistance change was used for battery charging apparatus instead of feedback control.
Treatment for deep local cancer has not yet been established. We propose a hyperthermia treatment method for deep local cancer by using implantable electrodes. In this study, a method for suppressing the edge effect in the implantable electrode was examined using electromagnetic and thermal simulation. Three types of models were proposed for this method—one with a bolus, one without a bolus, and one in the shape of the insulation sheet—and their temperature distributions were evaluated. The best model was then applied to a numerical human model that included 51 types of tissue and the pancreas (target organ), and the temperature was evaluated. As a result, temperature rise value of 1.5 °C in the deep of the target organ and that of 4.5 °C near the heating electrodes were obtained when the input power to the electrodes was 2 W at a frequency of 8 MHz. Therefore, it was found that the bolus and the insulation sheets covering the stepped edge of the electrode were effective to suppress the edge effect near the electrodes and to increase the temperature of the deep in the target organ. Thus, our method has a high capacity for deep local heating.
Recently, magnetic-geared motors that are a type of the low-speed and high-torque actuator attract attention. We have proposed a half- and a 3/4-permanent-magnet magnetic-geared motor, and their torque characteristics have been compared with conventional magnetic-geared motors. As a result, it was clarified that the maximum transmission torque and torque constant of both magnetic-geared motors are larger than those of the conventional magnetic-geared motors. This paper compares the torque characteristics of the half- and 3/4-permanent-magnet magnetic-geared motors with the conventional brushless motors in terms of the cogging torque, torque ripple, and N-T curve.