Owing to the merits of good fault-tolerant capacity, wide-speed range, and good sensorless operation capacity, a five-phase reverse-salient fault-tolerant permanent magnet (FPRSFT-PM) motor with the inductance characteristics of L_d > L_q is very suitable for the electric vehicle (EV) applications. However, due to the different effects of motor parameters caused by the realization of multiobjective performances such as good flux-weakening (FW) capacity and obvious reverse-salient characteristic, there are constraints in the process of realizing multiobjective performances, which cause serious interference to the design process of the FPRSFT-PM motor. Also, in the existing study, the design guidance for the FPRSFT-PM motor considering these different constraints is still absent. Hence, this article first develops the design criterion and optimization for the FPRSFT-PM motor considering multiobjective constraints. Furthermore, the FW ratio is innovatively introduced in the multiobjective optimization process to act as a new optimization objective and new objective functions are subtly changed, which can effectively balance the requirements of FW capacity and reverse-salient characteristic. Finally, the constraints between the FW capacity, reverse-salient characteristic, and the reluctance torque are greatly weakened, and all these performances of the FPRSFT-PM motor can meet the design requirements. Through simulation analysis and experimental tests, the rationality and validity of the proposed design criterion and optimization are verified.

Under the flux-weakening (FW) operation, the sensorless control of a five-phase flux-intensifying permanent magnet (FP-FIPM) motor faces the dilemma of reduced torque output and poor estimated accuracy caused by the serious space coupling between sensorless control and FW control. To overcome the abovementioned problems, a novel space decoupling sensorless control strategy for the FP-FIPM motor under FW operation is proposed in this article. Based on the decoupling model of the FP-FIPM motor, this article first proposes the dual space design to achieve the decoupling of sensorless control and FW control. For the FW control, an adaptive third-harmonic current injection strategy is proposed based on the fundamental space, which can effectively improve the torque output capability of the FP-FIPM motor. For the sensorless control, an adaptive frequency complex coefficient filter sliding mode observer (AFCCF-SMO) is developed based on the third-harmonic space, which can reduce complex disturbances and further improve the estimated rotor position accuracy. The feasibility of the proposed strategy is verified by experimental results.

A comparative study of new partitioned stator hybrid excitation axial flux switching permanent magnet (HEAFSPM) motors with different partitioned excitation stator topologies for in-wheel traction applications is presented in this paper. The realization approaches of the partitioned stator HEAFSPM motor are discussed, and the motor topology with windings and permanent magnets (PMs) separately setting on different stators is selected in view of the advantageous structure for thermal management. On this basis, two partitioned excitation stator topologies including C-type tooth core and T-type tooth core stator configuration are proposed, and the air-gap flux modulation and flux regulation principle of the motors are analyzed. In addition, the design method of the partitioned stator HEAFSPM motor considering the effect of hybrid excitation sources is provided, and the two motors with different tooth cores are designed respectively. Meanwhile, for a fair comparison, the multiple objectives optimization method coupled with the sensitivity analysis is employed to optimize the two motors. The electromagnetic performances, anti-demagnetization capability, and flux regulation performance of the two motors are all investigated in detail. Finally, two prototype motors are fabricated and tested. Both the theoretical analysis and experimental results verify the effectiveness and reasonability of the motor.

This paper proposes a new five-phase flux-intensifying fault-tolerant interior-permanent-magnet (FIFT-IPM) motor to realize high fault tolerance and sensroless operating capacity of the motor drive system for electric vehicles (EVs). By employing the new concept of flux-intensifying, the proposed motor owns the outstanding characteristic of Ld >Lq, which can contribute the sensorless operation significantly. By integrating the special design of stator tooth, using the masterly PM placement and increasing the length of air gap in q-axis, the high fault tolerance and high reliability can be obtained, which is essential for EV applications. The static performances of the proposed motor are investigated by using finite-element analysis. And the corresponding sensorless operation experiments are implemented based on the prototyped motor. Both theoretical analysis and the experimental results verify the validity of the proposed five-phase FIFT- IPM motor design.

A generalized fault-tolerant control (FTC) strategy for the field-oriented control (FOC) and direct torque control (DTC) of five-phase fault-tolerant permanent magnet (FPFTPM) motors under various open-circuit faults is presented in this article. Most previous studies regarding FTC target a specific primary control algorithm and involve different reduced-order transformation matrices and additional current controllers, which increase the complexity of the entire drive system. In this study, a solution to the aforementioned problems is devised by developing optimal fault-tolerant voltages, which are derived from fault-tolerant mechanism analysis and steady-healthy design. Because the coordinate transformation need not be changed and additional voltage compensation is not required, a minimal control drive system reconfiguration under various open-circuit faults can be achieved to avoid accommodating the change of the primary control algorithm. The proposed control strategy not only improves the torque performance and dynamic response under healthy and fault conditions, but also adapts to both FOC and DTC. Experimental results for a 2 kW FPFTPM motor prototype are provided to evaluate the proposed strategy.

A fault-tolerant MTPA control strategy of five-phase flux-intensifying fault-tolerant permanent magnet synchronous motor (FI-FTPMSM) under open-circuit and short-circuit faults is presented. In previous studies, existing fault-tolerant MTPA control strategies suffer from weak robustness to the parameter variation, which is not suitable for the utilization of reluctance torque of the FI-FTPMSM. In this article, a five-phase FTPMSM with flux-intensifying effect is designed and proposed. To fully utilize the reluctance torque with flux-intensifying effect under fault conditions, an extended VSI-MTPA control strategy with a compensation factor is proposed, which can improve the dynamic and steady-state performance of the motor drive system under fault conditions. In addition, an extended sliding-mode disturbance observer with adaptive gain is proposed to suppress the harmonic interference caused by faults, which possesses good resistance to complex disturbance. Finally, the feasibility and effectiveness of the proposed strategy are verified by experimental results.