Shinji Wakao

An optimal design of interior permanent magnet synchronous motor for the next generation commuter train

In this paper, we propose a computational approach to the design of an interior permanent magnet synchronous motor to clarify its optimal design applied for traction systems of the next generation commuter train. In the approach, the finite element method, the multiobjective optimization technique, and the response surface methodology are effectively introduced. This approach enables us to save the CPU-time dramatically without degrading accuracies. Additionally, the proposed approach provides the effective information to design engineers. Finally we validate the proposed approach.

Electromagnetic field computations by the hybrid FE-BE method using edge elements

The authors present a hybrid finite-element (FE) and boundary-element (BE) method using edge elements for an open-boundary 3-D electromagnetic problem. In this method, the modified magnetic vector potential A* and the magnetic field intensity H are adopted as the physical quantities. The appropriate BE discretization described makes it easy to couple the BE region with the FE region through the transformation of unknown variables. Several practical applications of this method to 3-D eddy current problems are presented. The calculated values agree well with the experimental results. >

Sensorless control for permanent magnet synchronous motor with reduced order observer

This paper describes a simple sensorless control scheme for permanent magnet synchronous motors based on the reduced order observer. By introducing the new control inputs, we realize both the decoupling and the linearization of the nonlinear electrical equations. This allows us to construct the reduced order observer for estimating the rotor speed and position. Owing to the linearization of the motor model, we can fix optimum gains of the observer under any operating condition. The validity of the proposed control scheme is confirmed by experiments as embedded code in a DSP-TMS320C32. The experimental results show high dynamic performance of the proposed control scheme.

Large-scale and Fast Nonlinear Magnetostatic Field Analysis by the Magnetic Moment Method with the Adaptive Cross Approximation

This paper describes large-scale and fast nonlinear magnetostatic field analyses by the magnetic moment method (MMM) with the adaptive cross approximation. In order to stabilize the convergence characteristic of the Newton-Raphson method, we apply a line search technique to the MMM. Some numerical results that demonstrate the validity of the developed method are also presented

Multiobjective design optimization of brushless permanent magnet motor using 3D equivalent magnetic circuit network method

In this paper, we discuss multiobjective design optimization of brushless permanent magnet motor (BLPMM) solved by genetic algorithm (GA) and 3D equivalent magnetic circuit network (EMCN) method. In the multiobjective optimization (MO) problem, we choose the decrease of cogging torque and the increase of torque as objectives. The airgap length, teeth width and magnetization angle of permanent magnet (PM) are also selected for the design variables respectively. From the results, our approach method enabled us to efficiently obtain diverse Pareto optimal (PO) solutions from the practical point of view. The experimental results are shown to confirm the validity of the optimization results.

Large-scale analysis of eddy-current problems by the hybrid finite element-boundary element method combined with the fast multipole method

This paper shows large-scale eddy-current analysis by a hybrid finite-element and boundary-element (FE-BE) method. We introduce the fast multipole method (FMM) into the two kinds of hybrid FE-BE formulations developed by ourselves. To achieve more reduction of CPU time, we propose a novel preconditioning technique suitable for the hybrid FE-BE methods with the FMM. Furthermore, we improve the FMM calculation process in the hybrid method using magnetic field intensity. Some numerical results that demonstrate the effectiveness of these approaches are also presented

Convergence Acceleration of Time-Periodic Electromagnetic Field Analysis by the Singularity Decomposition-Explicit Error Correction Method

This paper proposes a novel method for the improvement of the convergence to a steady state in time-periodic transient nonlinear eddy-current analyses. The proposed method, which is based on the time-periodic finite element method and the singularity decomposition-explicit error correction method, can extract poorly converged error components corresponding to the large time constants of an analyzed system. The correction of the extracted error components efficiently accelerates the convergence to a steady state. Numerical results verify the effectiveness of the proposed method.

Starting Procedure of Rotational Sensorless PMSM in the Rotating Condition

This paper investigates a starting procedure of rotational sensorless permanent magnet synchronous motor (PMSM) in the rotating condition, which is suitable for some applications with higher maximum rotor frequency and longer current sampling time. Instantaneous estimation of initial rotor position and frequency, right after gates start, is essential for restarting the operation of inverters. Existing estimation methods are not available for the aforementioned applications because of their higher maximum rotor frequency and longer current sampling time. To cope with this problem, we propose a novel initial rotor frequency estimation method. The proposed estimation method is verified by experiments using a 2-kW interior PMSM and a numerical simulation.

Novel boundary element formulation in hybrid FE-BE method for electromagnetic field computations

The authors propose a novel boundary element formulation using the scalar potential in the hybrid finite element (FE) and boundary element (BE) method for electromagnetic problems. They adopt the analytical integration as much as possible in this method. This approach has the advantage of reducing the number of unknown variables and makes it easy to couple the BE region with the FE region. A practical application of the proposed method to the three-dimensional eddy current problem is presented. The calculated values agree well with experimental results. >

Large-scale and highly accurate magnetic field analysis of magnetic shield

This paper describes a large-scale and highly accurate magnetostatic field analysis targeting a magnetic shield. The hybrid finite element–boundary element method and the magnetic moment method do not require mesh division for the free space and can easily treat the nonlinearity of magnetic property. Therefore, these methods are considered very effective for the analysis of a magnetic shield which has a high aspect ratio of the size scale to the thickness. However, large memory and computational time have been required due to the dense matrices generated by those integral-based formulations. To overcome the difficulties, we introduce the fast multipole method into the hybrid method and the magnetic moment method. Furthermore, to achieve more reduction of CPU time, we propose an effective preconditioning technique suitable for the hybrid method. Some numerical results that demonstrate the effectiveness of these approaches are also presented.