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Purpose The purpose of this paper is to investigate a novel axial flux-switching motor with sandwiched permanent magnet for direct drive electric vehicles (EVs), in which the torque density is increased and the cogging torque is decreased. For reducing the back-electromotive force (EMF) harmonics and cogging torque, a twisted structure is employed. To improve the dynamic performance of the axial field flux-switching sandwiched permanent magnet (AFFSSPM) motor a space vector modulation-direct torque and flux control scheme is proposed. Design/methodology/approach A multi-objective optimization is performed by means of artificial neural network and non-sorting genetic algorithm II to minimize the cogging torque while preserving the average torque. Findings A comparative study between two proposed machines and the conventional flux-switching permanent magnet (FSPM) machine is accomplished and the static electromagnetic characteristics are analyzed. It is demonstrated that the proposed model with twisted structure has significantly improved performance over the conventional FSPM machine in back-EMF and efficiency. The proposed controller has a speed loop only and contains neither the current loop nor hysteresis control. The AFFSSPM motor exhibits excellent dynamic performance with this scheme. Originality value The axial flux-switching permanent-magnet machine is one of the most efficient machines but the AFFSSPM with sandwiched permanent magnet has not been specially reported to date. Thus in this paper, the authors report on optimal design of an axial flux-switching sandwiched permanent magnet machine for electric vehicles and investigate its dynamic performance.

Purpose The purpose of this paper is to suggest a novel current sensor-less drive system for a novel axial flux-switching permanent-magnet motor drive to reduce the costs and avoid problems caused by faults of the current sensors. Design/methodology/approach Commonly, a conventional controller needs at least two current sensors; in this paper, the current sensors are removed by replacing estimated stator current with the extended Kalman filter. Findings A prototype of the novel axial flux-switching permanent-magnet motor is fabricated and tested. It is found that the experimental results confirm the proposed method and show that the control has almost the same performance and ability as the conventional control. Originality/value The axial flux-switching permanent-magnet motor is one of the most efficient motors, but current sensor-less control of an axial flux-switching permanent-magnet motor with a sandwiched permanent magnet and a unity displacement winding factor has not been specially reported to date. Thus, in this paper, the authors report on current sensor-less control based on the extended Kalman filter for electric vehicles.

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