This paper considers a linear tubular permanent magnet motor (LTPMM) for an active suspension system. The LTPMM has an end effect due to its structure. This can be an important factor for analysis and design of the LTPMM because it distorts the air-gap magnetic flux distribution. The field reconstruction method (FRM) was developed for an effective evaluation of the magnetic field in the electric machine. It can reduce the computation time using the basis-function which reconstructs the air-gap magnetic flux distribution with a static finite element analysis. In this paper, we adopted the FRM to evaluate the LTPMM. However, the FRM has been applied only to the rotating machines and does not take into account the distortion of the magnetic flux distribution in the LTPMM. To deal with this problem, we proposed an enhanced FRM with new basis-function. The proposed method is verified by comparing between experiment result, conventional and enhanced FRM. INDEX TERMS Active suspension system, linear active suspension, linear permanent magnet motor, field reconstruction method.

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This paper presents a characteristic analysis of axial flux permanent magnet machines (AFPMMs) for in-wheel electric vehicles. Preferentially, a novel quasi-3-D model is developed for the fast and accurate design of AFPMMs. In electromagnetic field analysis, combined with field reconstruction method, the computation time of 2-D solutions is significantly reduced. With the use of time sweeping of the basis function, only the static finite element (FE) analysis is performed to calculate the air-gap flux distribution at the entire rotor position, whereas the conventional 2-D solutions require a transient FE analysis. In the shape sweeping process of the basis function, the virtual air-gap section method is introduced to take into account that the ratio of slot opening to slot pitch is different depending on the radius of analysis plane, which causes errors in the analysis results of the conventional quasi-3-D method. The virtual air-gap sections are obtained by interpolation of the spatial field between the mapped cylindrical planes. The proposed technique reduces the number of 2-D analysis planes required for high accuracy in the conventional quasi-3-D method, and it can also predict the air-gap magnetic flux distribution for skewed permanent magnets without additional FE analysis. Finally, using the magnetic fields calculated in the proposed method, the electromagnetic performances of the AFPMM are calculated, such as load torque, cogging torque, attraction force, and back-EMF. The analysis results were verified by comparison with the measurement results.INDEX TERMS Axial flux permanent magnet machine, in-wheel motor, magnetic field reconstruction, permanent magnet skew, quasi-3-D finite element analysis, virtual air-gap section method.

This work presents the comparative study of the linear tubular permanent magnet motor (LTPMM) for the active suspension system in vehicles. To analyse and design the LTPMM, a finite element-based optimisation process is proposed. Since the proposed method reconstructs the entire field by storing the information of the air-gap magnetic flux distribution in the form of a snapshot, it provides high accuracy and a reduced computation time. The magnetic fields are analysed in LTPMMs with external and internal permanent magnets that are classified according to the position of the permanent magnet. In the comparative analysis, an optimal model for the LTPMM is presented, taking into account characteristics such as thrust, detent force and THD. Especially, various magnetisation patterns are considered to accomplish high force density. The analytical model is verified by performing finite element analysis and experiments.

This paper presents a fast design optimization using an effective characteristic analysis for linear permanent magnet motors (LPMMs) with techniques for improving motor performance such as using an auxiliary tooth, permanent magnet (PM) skew, and overhang structures. These techniques have different effects on the characteristics of the LPMM depending on the combinations of each other, resulting in complexity in the design optimization process. In particular, the three-dimensional (3-D) effect of the PM skew and overhang structure takes a lot of time to be analyzed. To deal with this problem, an effective magnetic field analysis method and a novel optimization algorithm are proposed. Preferentially, the field reconstruction method is used for a fast and accurate evaluation of the magnetic field of the LPMM. In the proposed magnetic field analysis method, the change of magnetic field distribution due to the addition of an auxiliary tooth is predicted, and the 3-D magnetic field effect of PM skew and overhang structure is considered. By reducing the computational burden in the magnetic field analysis, the electromagnetic characteristics of LPMMs can be calculated quickly, such as detent force, end force, thrust force, and back-EMF. The effect of the auxiliary tooth and overhang structure on the optimal PM skew length is investigated with comparative study results. Subsequently, the proposed optimization algorithm has the advantage of reducing time cost by providing multimodal optimization and robustness evaluation of local peaks at the same time. The proposed method is verified via comparison with finite element analysis and experimental results.