Jang-Ho Seo

Multimodal function optimization based on particle swarm optimization

In this paper, a new algorithm for the multimodal function optimization is proposed, based on the particle swarm optimization (PSO). A new method, named the multigrouped particle swarm optimization (MGPSO), keeps basic concepts of the PSO, and, thus, shows a more straightforward convergence compared to conventional hybrid type approaches. Moreover, the MGPSO has a unique advantage in that one can search N superior peaks of a multimodal function when the number of groups is N. The usefulness of the proposed algorithm was verified by the application to various case studies, including a practical electromagnetic optimization problem

An Improved Particle Swarm Optimization Algorithm Mimicking Territorial Dispute Between Groups for Multimodal Function Optimization Problems

In the present paper, an improved particle swarm optimization (PSO) algorithm for multimodal function optimization is proposed. The new algorithm, named auto-tuning multigrouped PSO (AT-MGPSO) algorithm mimics natural phenomena in ecosystem such as territorial dispute between different group members and immigration of weak groups, resulting in automatic determination of the size of each groups territory and robust convergence. The usefulness of the proposed algorithm is verified by the application to a specially designed test function and a practical electromagnetic optimization problem.

A Research on Iron Loss of IPMSM With a Fractional Number of Slot Per Pole

In this paper, we investigated rotor iron loss of interior permanent magnet synchronous machine (IPMSM), which has distributed armature windings. In order to study the iron loss with the effect of slot-pole combination, two machines for high-speed operation such as electric vehicle were designed. One is fractional slot winding and the other is conventional one. In the analysis, we developed a new iron loss model of electrical machines for high-speed operation. The calculated iron loss was compared with the experimental data. It was clarified that the proposed method can estimate iron loss effectively at high-speed operation. Based on this newly proposed method, we analyzed iron loss of the two machines according to their driving conditions. From the analysis results, it was shown that rotor iron loss of machine employing fractional slot-winding is definitely large at load condition. In addition, it is interesting that the ratio (rotor iron loss/stator iron loss) becomes larger as the speed of the machines increase if the number of slot per pole is fractional.

Harmonic Iron Loss Analysis of Electrical Machines for High-Speed Operation Considering Driving Condition

In this paper, we proposed new harmonic iron loss calculation methods for electrical machines. The new methods based on the concept of variable loss coefficients due to their flux density and frequency estimate harmonic iron loss in the time domain and the frequency domain. In order to verify the performance of the proposed method, we calculated the iron loss with conventional methods. Then, the estimated iron losses were compared with the experimental data. It was clarified that the proposed methods are more effective than the conventional methods at high-speed operation. Based on these newly proposed methods, we analyzed the iron loss of the machine for electric vehicle (EV) according to its driving condition. From the analysis results, it was shown that the harmonic iron losses of stator are larger than before at field-weakening region. In addition, it was revealed that rotor iron loss mainly induced by stator slot ripples does not show strong dependence on the current angle and only varied primarily according to the speed.

A Study on Loss Characteristics of IPMSM for FCEV Considering the Rotating Field

This paper presented the loss characteristics of interior permanent-magnet machines (IPMSM) for a fuel-cell electric vehicle. In order to study the loss characteristics of the machine, one prototype machine having 100 [kW] was designed. In the analysis, to consider the harmonic magnetic field and the rotational variation of flux vectors in the core of the machine effectively, we proposed a new harmonic iron-loss calculation method based on adaptive loss coefficients. To verify the performance of the proposed method, we calculated a no-load iron loss in an IPMSM with conventional methods. Then, the estimated iron losses were compared with the experimental data. It was clarified that the proposed method is more effective than conventional methods at high-speed operation. Based on this proposed method, we investigated the losses of the machine considering operating points according to its speed. From the results, it was shown that the main loss component and the location of iron-loss distribution change depending on operating condition.

Rotor-Design Strategy of IPMSM for 42 V Integrated Starter Generator

In this paper, we proposed an optimal design strategy of interior permanent magnet synchronous machine (IPMSM) considering various design constraints in the 42 V integrated starter generator (ISG). Since conventional optimal process needs much calculating time to check many constraints such as high starting torque, the high generating power at the maximum speed, we adopted AT-MGPSO as an optimization algorithm due to its special advantage that it can efficiently search superior peaks in the multimodal problem with short time. In addition, in order to deal with mechanical stress in the rotor by centrifugal force at maximum speed we combined mechanical stress analysis with the optimal design process. The validity of our proposed methods was verified by comparing simulation results with experimental data.

Characteristic Analysis for IPMSM Considering Flux-Linkage Ripple

In a multi-layer interior permanent magnet synchronous motor, the d- and q-axis parameters vary nonlinearly according to different load conditions, consequently changing the level of saturation. The flux-linkage of d- and q-axis conveys ripple characteristics resulting from mechanical structure and degree of magnetic saturation. If the calculated flux-linkage is correct, the torque using the Maxwell stress tensor method is the same torque calculated by the flux-linkage. However, discrepancy between results exists. In this paper, the d- and q-axis flux-linkage, in consideration of the ripple characteristic, is calculated. Simulation results are then compared with experimental results.

Optimal rotor structure design of interior-permanent magnet synchronous machine base on improved niching genetic algorithm

In this paper, an improved niching genetic algorithm applying the concept of auto-tuning and detecting traces is proposed for asymmetrical multimodal function optimization. Population size and both (right and left) niche radii of each peak in an asymmetrical objective function can be determined automatically. This method is applied to the numerical examples and the optimal design of interior permanent magnet synchronous machine (IPMSM). Through the comparison between simulation results and experimental ones, the validity of the proposed method is verified.

Hybrid Optimization Strategy using Response Surface Methodology and Genetic Algorithm for reducing Cogging Torque of SPM

Numerous methodologies have been developed in an effort to reduce cogging torque. However, most of these methodologies have side effects that limit their applications. One approach is the optimization methodology that determines an optimized design variable within confined conditions. The response surface methodology (RSM) and the genetic algorithm (GA) are powerful instruments for such optimizations and are matters of common interest. However, they have some weaknesses. Generally, the RSM cannot accurately describe an object function, whereas the GA is time consuming. The current paper describes a novel GA and RSM hybrid algorithm that overcomes these limitations. The validity of the proposed algorithm was verified by three test functions. Its application was performed on a surface-mounted permanent magnet.

A study on characteristics of rotor losses for IPMSM considering slot-pole combination

In this paper, we investigated the effect of slot-pole combi nation on rotor loss in interior permanent magnet synchronous machine (IPMSM) with distributed armature windings. In order to study the characteristics of the rotor los ses, two machines for high-speed operation such as electric vehicle were designed. One is fractional slot winding and the other is conventional one. Based on 2-D time-stepped finite element m ethod (FEM) we analyzed both iron loss and eddy-current loss in the permanent magnet of the machines according to their driving conditions. From the analysis results, it was shown that rotor iron loss and eddy-current loss of PM of machine employing fractional slot-winding is definitely large at load condition .