2×3-phase surface-mounted permanent magnet synchronous motor (SPMSM) is gaining increasing attention due to its strong reliability and redundancy characteristic, in which winding configuration plays a crucial role. However, most existing research focus on fault-tolerant control strategies, and there are few research on the comprehensive comparisons of the performance under normal and faulty operations for different connection modes. In this article, the mono-inverter parallel drive method is employed to smaller the size and reduce the cost of drive system. Additionally, theoretical derivation is conducted for mathematic models under different connection methods, as well as under normal and passive fault-tolerant conditions. Furthermore, the comprehensive evaluation of all connection modes is conducted. Finally, the experimental results validate the correctness of the above theoretical analysis.

ABSTRACT Magnetic screw motor (MSM) is a typical double degree‐of‐freedom actuator. Inevitably, such actuators require two position encoders, including a linear encoder and a rotary encoder. To achieve the reduction of system costs and the improvement of system reliability, a sensorless control strategy based on high‐frequency square‐wave signal injection is proposed to replace the rotary position encoder. By injecting high‐frequency pulsating square‐wave signals into the d ‐axis voltage, the estimated rotor position information can be decoupled from the αβ ‐axes voltage through a signal processing module. Simultaneously, to simplify the system structure and improve the control performance, a sliding‐mode controller with an improved reaching law is utilised. The proposed sliding‐mode controller is implemented based on the mathematical model of the MSM. The given q ‐axis current can be obtained from the given linear displacement through the mathematical model of the MSM; thus, the rotor speed closed‐loop can be eliminated, and the traditional three‐closed‐loop structure can be simplified to a double‐closed‐loop structure. Moreover, the used reaching law can reduce chattering while ensuring the convergence speed. Consequently, the reliability and validity of the proposed method are verified through experimental results.

Aiming at the defects of traditional fault-tolerant control (FTC) and fault detection systems, a diagnosis-free passive FTC (PFTC) scheme for nx3 phase surface-mounted permanent-magnet synchronous motors (SPMSMs) with connected neutral point is proposed. To reduce the cost, volume, and complexity of the driver, this article adopts a mono-inverter parallel drive for nx3 phase motors, which is a prerequisite for achieving passive fault tolerance. By combining the i(d)=0 control strategy and field-oriented control (FOC) technology of the traditional three-phase PMSMs, the self-healing capability can be realized after nx3 phase SPMSMs experience double-phase open-circuit faults. Due to the proposed PFTC scheme not requiring the fault diagnosis process, the impact of misdiagnosis and diagnostic delays can be fundamentally avoided. In addition, there is no need to optimize the modulation strategy, motor model, or reference current before and after the fault, thus enabling smooth switching between different operating states. The proposed PFTC scheme can not only achieve seamless switching under multiple operating conditions but also be simple and easy to operate. The experimental results are carried out to verify the effectiveness and feasibility of the proposed method.

While permanent magnet vernier motors offer the advantage of high torque density, they require a large amount of permanent magnets, resulting in high cost in application. Consequent-pole permanent magnet Vernier (CPPMV) motor exhibit reduced permanent magnet (PM) consumption but typically compromise torque density. This paper proposes a CPPMV motor with embedded Halbach arrays, which can obtain higher torque density and less PM consumption. The flux concentration and modulation effects of magnetic field is analyzed. For fair comparison, all the motors are optimized by multi-objective optimization. Compared with two traditional Halbach structures, the proposed motor exhibits higher output performance, effectively validating the advantages of the proposed motor.

This article proposes a fault-tolerant sensorless control strategy based on a frequency adaptive extended state observer (ESO) with complex coefficient filter (FAESO-CCF) for a 3x3 -phase permanent magnet (PM)-assisted synchronous reluctance motor (PMA-SynRM) with single-phase open-circuit fault (OCF). By controlling the cooperative operation of each module, the torque ripple can be significantly reduced, thereby realizing the fault-tolerant operation under single-phase OCF. In order to meet the requirements of fault tolerance, the input voltage and current of the position sensorless are severely distorted, resulting in a decrease in the estimation accuracy of the rotor position. To solve this problem, the frequency adaptive ESO (FAESO) with bandpass filter properties is proposed. Moreover, a complex coefficient filter (CCF) is introduced to extract the third and fifth harmonics in the active flux estimated by FAESO, so that the bandwidth of FAESO can be appropriately relaxed and the response speed of the system can be improved. Meanwhile, a type-3 phase-locked loop (PLL) is designed to overcome the defect of type-2 PLL that there is a steady-state error during ramp acceleration, which further improves the accuracy of system. Finally, the accuracy and effectiveness of the proposed observer are evaluated by experiments.

Stator-permanent magnet (stator-PM) motor has garnered significant attention due to its high robustness, making it more suitable for operation in textile industry, small conveyor belt, tracked robot etc. However, the use of rare-Earth permanent magnets (PM) in such motors, while possessing desirable properties, comes with a high cost, limiting its widespread industrial application. In this article, a less rare-Earth flux reversal permanent magnet (FRPM) motor with integer slot distributed winding is proposed, which can significantly improve the utilization ratio of PM material. An orthogonal modulation analysis method is proposed to clarify the operation principle of the proposed FRPM motor. Utilizing this method, the harmonic distributions of radial and tangential magnetic fields generated by PM material and armature current can both be derived. Additionally, employing maxwell tensor method, the torque generated by each harmonic is calculated, which verifies that the static fundamental harmonic can also generate the main output torque. Furthermore, the multiobjective genetic algorithm method is applied to optimize the parameters. Three existing PM motors, namely one flux-switching PM motor and two conventional FRPM motors, are used to compare with the proposed motor. The results indicate that the proposed motor can reach higher torque with less PM consumption. Finally, a prototype is processed and tested to validate the correctness of the design and analysis.

Permanent-magnet vernier (PMV) motor is well-known for its distinctive performances of high torque at low speeds, making it suitable for direct drive application. However, the rich harmonics lead to the high loss and low efficiency of motor system. To suppress the harmonic loss, a stator modular design concept is proposed for PMV motor. Firstly, the precondition that the motor meets the stator modular design is derived, and according to this, a variety of options for modular design are expounded, including uniform or non-uniform modular designs and tooth or yoke modular designs. Then, the harmonic distributions of PM field, armature reaction field, and harmonic loss of PMV motor with fractional slot concentrated winding (FSCW) are analyzed. Based on finite element analysis, the inhibitory effect of modular design method on the amplitude of the harmonic with low pole pair number in the motor armature reaction field is verified. Through comparison, it is found that the proposed stator modular design method can suppress motor losses without reducing output performance. Finally, a PMV motor with modular stator is processed and tested to verify the analysis.

ABSTRACT The development of a natural fault‐tolerant algorithm significantly reduces the dependence of surface‐mounted permanent magnet synchronous motor (SPMSM) control systems on conventional fault‐detection methods. This advancement effectively mitigates misdiagnosis risks while enhancing overall system reliability. This paper presents a comprehensive investigation and analysis of passive fault‐tolerant mechanisms in delta‐connected 2 × 3‐phase SPMSM systems under two‐phase open circuit fault (OCF) conditions. Owing to its distinctive topological configuration, the proposed system exhibits inherent self‐regulating characteristics. Specifically, when a two‐phase OCF occurs in a delta‐connected 2 × 3‐phase SPMSM driven by a mono‐inverter, the healthy phases connected in parallel with the faulty ones automatically increase their current to maintain the required magnetomotive force for continuous motor operation. Finally, the feasibility and reliability of the proposed fault‐tolerant scheme are validated experimentally.

The magnetic screw motor (MSM) drive systems often require both a rotary encoder and a linear encoder for their precise positioning, which makes the design of such systems very challenging and costly. This article proposes a novel position sensorless control strategy. First, an improved pulsating current injection (IPCI) sensorless control is proposed to replace the rotary encoder. This method associates the amplitude of the injection signal with the q-axis current by introducing a transformation matrix. In the proposed method, the amplitude of the injection signal increases with the load/speed variation, which enhances the rotary speed estimation accuracy in transients. Meanwhile, when the motor operates in a steady state, the amplitude of the injection signal is maintained in a low range, which reduces the audible noise. Second, the linear encoder is eliminated using a relative speed compensation based on a lookup table (LUT) method. The relative speed under different linear speeds can be obtained and tabulated from several experimental tests. The presented experimental results verify the proposed method and its performance.

In this paper, a new fault-tolerant control (FTC) strategy based on minimum torque ripple is proposed for a triple redundant permanent magnet assisted synchronous reluctance motor under single-phase and double-phase faults. Different from removing the faulty modules (single six-phase (S6) operation or single three-phase (S3) operation), the proposed strategy makes full use of the healthy phase of the faulty modules. By precisely controlling the d-q axes currents of each module, the ripple of permanent magnet torque and reluctance torque can be suppressed simultaneously, thus achieving the minimum output torque ripple. Moreover, the ratio ( k ) of the d-q axes current to the stator current can be determined under the constraint of minimum copper loss. In addition, by changing the ratio k , the proposed strategy can be combined with S6 or S3 strategy to achieve the minimum copper loss in a wide torque range. In summary, the proposed FTC strategy not only achieves the minimum torque ripple but also ensures the minimum copper loss. Finally, experiments are carried out to verify the accuracy and validity of the theory.

Fault-tolerant control (FTC) strategy can be realized without modifying the peripheral hardware circuit when the open-circuit fault (OCF) occurs in the multiphase motor. However, FTC relies on accurately identifying the fault location and switching to a new reconfiguration fault-tolerant algorithm. This can significantly increase the complexity of the system. To overcome the challenge, this article investigates a passive fault-tolerant scheme of a 2 × 3-phase surface-mounted permanent-magnet synchronous motor (SPMSM) driven by a mono-inverter when single-phase OCF occurs. The state equations based on field-oriented control of 2 × 3-phase SPMSM under healthy and single-phase OCF are discussed. The special motor drive mode and the constraint of id = 0 make the phase currents of each module passively optimized under the two neutral point configurations (i.e., isolated or connected), thus meeting the demand of restraining torque ripple. In the proposed PFTS, when the OCF occurs, the system does not require to attempt to diagnose or correct faults. Hence, a seamless transition from normal to faulty operation is guaranteed. Moreover, it enhances system reliability and stability. Furthermore, taking an existing 2 × 3-phase SPMSM as an example, the experiments are carried out for validation.

Sliding-mode observer (SMO) has attracted extensive attention in the field of medium- and high-speed sensorless control of permanent magnet synchronous motor (PMSM) because of its strong robustness and stability. However, the traditional methods are vulnerable to dc bias caused by measurement errors and parameter changes. Therefore, in this article, an improved SMO algorithm by disturbance observer compensation is proposed. The algorithm unifies the mathematical models of surface PMSM and interior PMSM. Besides, a bandpass filter (BPF) is used to replace the traditional low-pass filter, so it can effectively suppress dc bias and high-frequency noise. In addition, at any BPF center frequency, the proposed disturbance observer with low-pass filter (LPF) characteristics can perfectly compensate the position error caused by the digital filter in real time. Moreover, through sensitivity analysis, the influence of model uncertainty on the observation position is studied, and an adaptive extended state observer is added to mitigate the influence of parameter mismatch on the performance, hence improving the estimation accuracy. Finally, a triple redundant permanent magnet-assisted synchronous reluctance motor is taken as an example to verify the feasibility and effectiveness of the proposed observer.

Sensorless control methods based on flux observer have been widely used in motor drives with medium-high speed operation. However, the conventional methods have some shortcomings in estimation accuracy due to the dc bias caused by the integration, measurement, and parameter uncertainty. In this article, a new frequency adaptive disturbance observer with band-pass filter characteristics is proposed. It is insensitive to dc bias and high-frequency noise, hence improving the robustness of the system. Since the proposed method has no phase delay at any synchronous rotor frequency and can amplify the amplitude of the estimated active flux, it does not need a phase compensation module and can obtain a wider operating range. Moreover, an adaptive extended state observer is added to estimate the disturbance caused by parameter mismatch. The estimated disturbance is fed back to the estimated active flux, which further improves the accuracy of the system. Finally, experiments based on a triple redundant permanent magnet-assisted synchronous reluctance motor are accomplished to verify the effectiveness and accuracy of the proposed observer.

单逆变器驱动的3×3相永磁辅助同步磁阻电机系统具有低成本、高可靠性的优点.该文针对此系统的两相开路故障,提出一种各模块转矩重新分配的容错控制策略.当同一模块发生两相开路故障时,将该故障模块完全切除,通过增加非故障模块的电流来实现容错运行.对于不同模块同相位两相开路,通过分析故障后各模块的等效电路,获得两相静止坐标系下电流之间的关系,然后构造拉格朗日函数,以铜耗最小为目标,求解电流幅值的最优解,最终实现转矩的重新分配.当发生不同相位两相开路时,以故障模块输出最大平均转矩以及总的转矩脉动最小为目标,对各模块转矩进行重新分配.该方法通过增加正常模块转矩脉动来部分抵消故障模块产生的脉动,达到抑制输出转矩脉动的目的.实验结果验证了所提容错控制策略能有效降低故障后电机的转矩脉动,提高了控制系统的可靠性.

In this article, the fault-tolerant control (FTC) strategy based on current redistribution is compared for three types of triple redundant $3\times 3$ -phase motor: surface-mounted permanent magnet synchronous motor (SPMSM), synchronous reluctance motor (SynRM), and permanent magnet-assisted synchronous reluctance motor (PMa-SynRM), under a single-phase open-circuit fault. The output torque of SPMSM and SynRM is produced by permanent magnet (PM) torque and reluctance torque, respectively. Nevertheless, for PMa-SynRM, it is necessary to determine the distribution ratio of PM torque and reluctance torque in the proposed FTC strategy. By comparing the FTC performance of motors, the conclusions are as follows: 1) torque ripple of the SPMSM can be completely suppressed; 2) torque ripple minimization for the SynRM and PMa-SynRM can be realized; and 3) optimal solution obtained in SynRM can also be applied to the PMa-SynRM when the load is heavy. In addition, to reduce the complexity and improve the reliability of the control system, a mono-inverter-driven triple-paralleled control system is constructed in healthy and postfault operations. The comparison results of the FTC strategy for three types of motor are obtained by simulation. And the experimental results based on a $3\,\times \,3$ -phase PMa-SynRM are accomplished to verify the feasibility of the theory.

In this article, a new fault-tolerant control strategy for a triple redundant 3 × 3 phase permanent magnet assisted synchronous reluctance motor under a single-phase open-circuit fault has been proposed. In order to reduce the cost of the system, a two-level three-phase inverter is constructed to drive the parallel-connected motor under normal and fault-tolerant conditions. In normal operations, the current and torque are equally distributed to the three modules of the motor, while in a fault-tolerant state, they should be redistributed according to a specific ratio. The optimal ratio is obtained by investigating the control strategy of minimum copper loss and minimum torque ripple. The torque ripple of the normal module is increased to offset the torque ripple of the fault module, thereby reducing the total electromagnetic torque ripple after the failure. It means that no auxiliary switching devices need to be added even if the failure happened, which can significantly reduce the complexity and improve the reliability of the control system. To verify the theoretical analysis, simulations and experiments have been conducted. The results are in good agreement with that of theoretical analysis.

To improve the torque performance of five phase permanent magnet synchronous motor under fault condition,a decoupling fault tolerant control method based on minimum copper loss was proposed.The method which based on the principle of the constant stator magnetic motive force and minimum copper loss could be used to calculating the fault-tolerant current.Then,according to the compensation current,the reduced-order transformation matrix had been deduced.In the rotating coordinates,the mathematical model of the five-phase permanent-magnet synchronous motor was established.And the decoupling vector control method is achieved.The effectiveness of the proposed fault-tolerant control algorithm is verified by the method of co-simulation.The results of the simulation showed that the proposed fault-tolerant control could reduce the torque ripple under the faulty condition.

Considering the problem of over many current sensors used in five-phase permanent magnet synchronous motor control system,a new method of current reconstruction for five-phase permanent magnet synchronous motor was proposed.This method used only two current sensors to realize full acquisition of five-phase current,could effectively reduce the cost and complexity of the hardware circuit.The reconstruction precision and speed could meet the needs of five-phase permanent magnet synchronous motor control.Finally,the proposed method was validated in MATLAB.Results showed the correctness and effectiveness of the proposed method.