Most fault-tolerant control schemes work based on fault diagnosis and control reconstruction, which suffers the misdiagnosis risk and process complexity. To address this issue, the natural fault-tolerant schemes are being developed for multi-phase motors, however, the use of virtual vector synthesis still makes it a large computational burden. This paper proposes a new natural fault-tolerant model predictive voltage control (NFT-MPVC) for the open-phase fault of a symmetrical six-phase vernier permanent magnet motor (SSP-VPMM), which directly uses appropriate actual voltage vectors specifically existed in symmetrical six-phase motors to avoid the complex calculation and the high switching frequency caused by virtual vector synthesis. Meanwhile, by combing the deadbeat control principle with sector judgment, the number of candidate voltage vectors is reduced to only two in one control cycle, thus further simplifying the calculation. The simulation and experimental results show that the proposed NFT-MPVC can provide satisfactory fault-tolerant performance with lower switching frequency compared with traditional natural fault-tolerant scheme using synthesized virtual vectors, and the computational burden of the proposed method can be reduced by at least 22%.

The abnormal electromagnetic responses of Gas Insulated Transmission Lines (GILs) pose a significant risk to equipment and grid safety; yet, the traditional full 3D electro-magnetic analysis method is limited by computational efficiency and structural applicability. Thus, the paper introduces a cross dimensional multi-physics coupling method to study the electro-magnetic responses of single-phase and three-phase enclosed GILs under different operating conditions. First, a novel 2D nod al electromagnetic analysis model is developed, incorporating the field-circuit coupling strategy to clarify the electromagnetic responses. Second, a 3D model of GILs is constructed for structural field analysis. Through an electromagnetic-mechanical coupling strategy, cross-dimensional transmission of 2D nodal electro-magnetic responses is achieved. Third, the use of a transient analysis method uncovers patterns of electromagnetic stress distribution. Finally, the findings are verified using Finite Element Analysis (FEA) and live examination experiments on GILs.

The equivalent parasitic capacitance (Cp) of motor windings causes the voltage/current overshoot and ringing during the switching of wide-bandgap semiconductor devices. Therefore, it is necessary to model and calculate Cp to evaluate its impact on the switching devices. However, due to the winding deviations and spatial constraints of the slots, the arrangement of coils is disordered. Using the ideal single value of Cp may lead to the significant deviations in the evaluation of switching transients. To address the above issues, the analytical method of parasitic capacitance considering the impact of distributed disorder is studied in this paper. The impact of the winding model on the calculated value of Cp is investigated. The winding distribution patterns are categorized into three types: uniform, partially disordered, and fully disordered. An analytical method for the distributed capacitance is developed, incorporating the influence of random coil placement. A set of samples for the parasitic capacitance values of disordered windings is generated using a random sampling method. The sample distribution is determined through confidence intervals and the Chernoff bound to approximate the original distribution. The similarity between the two distributions is verified using the K-S test. The region with the highest frequency in the sample distribution is identified as the prediction interval for the winding's parasitic capacitance value. Finally, the measurements are performed on the disordered distribution winding samples. The results prove the effectiveness and feasibility of the proposed method.

Harmonic currents are commonly employed in multiphase permanent magnet machines to enhance the output torque, which essentially improves the tangential force. However, as the radial force is also affected by the harmonic currents, the high noise and vibration may be induced. This paper systematically investigates the dual impacts of harmonic currents on both radial and tangential force characteristics. Analytical derivations reveal that armature-induced radial forces correlate with current phase, enabling anti-phase compensation between current-induced and inherent radial forces to suppress vibrations. However, the optimal phase angles for vibration minimization and torque maximization are inherently mismatched. A detailed parametric analysis is performed through finite element simulations on a five-phase permanent magnet machine with 10-slot/8-pole configuration, employing third harmonic current injection with varying amplitudes. The amplitude-phase relationships of both tangential and radial force components are quantitatively examined. Results demonstrate the fundamental compromise between torque improvement and vibration reduction in current injection strategies. Experimental validation is subsequently conducted through prototype testing, with measured vibration acceleration and output torque data confirming the analytical findings.

Stator winding insulation is one of the most fragile components in electric drive system. To prevent insulation-related failures, online condition monitoring of stator insulation is critical to ensure high reliability requirements in inverter-fed ac motors. Groundwall insulation monitoring can be achieved by common-mode (CM) measuring methods, which evaluate insulation by CM impedance spectrum shifts. However, CM impedance shows distinct insulation-related characteristics over broadband frequency range. In this article, insulation-related characteristics are revealed and compared by developing individual models in different frequency regions. Besides, a hybrid model-data driven method is proposed to achieve assessment of groundwall insulation in this article. Phase-to-ground and neutral-to-ground insulation are distinguished by pretrained network, which establishes the link between CM features and insulation capacitances. Experimental results have been conducted on inverter-fed induction machine with an accelerated aging procedure. The experiment results prove that the proposed method can achieve detection of groundwall insulation in real time.

Six-phase motor drive systems are widely used in industrial drives, transportation, and other fields because of their many advantages, such as high reliability, high fault tolerance, low amplitude of torque pulsation, and a large degree of control freedom. Six-phase motor drive topology is mainly based on the voltage-source inverter (VSI), which has a simple circuit structure and is widely used; however, this topology has the shortcomings of poor output voltage waveform quality, high voltage step, high output common-mode voltage (CMV) step, only step-down output, small output voltage range, and so on, most of the control strategies used are relatively complex, and the control system cost is high. To address the shortcomings of the traditional six-phase VSI, a six-phase motor driver based on a buck-boost converter is proposed, which adopts a voltage closedloop control strategy using simple constant voltage-frequency (V/F) ratio control. The proposed topology has the advantages of low CMV fluctuation, low common-mode current, high-quality voltage waveform, wide-range voltage output, single-stage power conversion, high efficiency, high reliability, and so on. The adopted control strategy is simple, and the cost and difficulty of the actual experimental platform design are small, which can realize a good closed-loop control of motor speed. In this article, a 2-kW 60V(DC)/127V(AC) six-phase buck-boost motor drive experimental prototype platform is designed and developed, and the feasibility and advancement of the control scheme of the proposed topology are verified through experimental results

To meet the high-precision control requirements of Permanent Magnet Synchronous Motors (PMSM) in servo systems, this study investigates a sensorless hybrid control strategy, overcoming the issues of low reliability and high cost associated with traditional mechanical sensors in harsh environments. The proposed method combines the characteristics of low-speed and high-speed operation by integrating a high-frequency (HF) signal injection algorithm with a flux observer algorithm into a hybrid observation strategy: at low speeds, rotor position information is extracted using HF injection, while at high speeds, the flux observer algorithm is employed. To address the switching between these two algorithms, a weighted switching algorithm with a phase compensation mechanism is designed to enhance estimation accuracy and reduce torque transients. Simulation and experimental results demonstrate that the hybrid strategy achieves accurate rotor position and speed estimation across the entire speed range, effectively suppresses torque ripple, and ensures stable motor operation. This research provides a feasible sensorless technical solution for PMSM control, offering significant theoretical and engineering value for improving the reliability and environmental adaptability of servo systems.

Phase locked loop (PLL) is adopted to obtain the position and speed signals, in terms of sensorless control for permanent magnet synchronous motor (PMSM) drives. However, the position estimation accuracy with the traditional PLL deteriorates during fast dynamic process, especially for ship propulsion with frequent speed change and load mutation. To enhance the dynamic response performance, extended state observer (ESO) is embedded into PLL. The PI controller is replaced by ESO, to enhance the tracking capability of dynamic signals. The system characteristics are illustrated and compared. Finally, the feasibility and performance are validated on the PMSM prototype under various operating conditions.

Due to frequent external disturbances occurring in linear motors, especially in long-distance drive systems, traditional proportional-integral (PI) controllers cannot meet the requirements of dynamic performance and robustness capability. The active disturbance rejection controller (ADRC) has been widely adopted for its effectiveness in improving the disturbance immunity of motor drives. Nonetheless, conventional nonlinear ADRC (NLADRC) and linear ADRC (LADRC) have their own advantages, disadvantages, and specific application scopes in the disturbance range. To extend the application range and enhance the dynamic performance and anti-interference capability, a cascaded ADRC (CADRC) is proposed as the speed regulator, which integrates the linear extended state observer (LESO) and the nonlinear extended state observer (NLESO) to estimate the total disturbance. Then the stability and the performance indicators of the proposed CADRC are theoretically analyzed using the Routh-Hurwitz stability criterion and frequency-domain analysis. Finally, the feasibility and effectiveness of the control scheme are verified through simulations and experiments on a prototype of a linear flux-switching permanent magnet (LFSPM) motor.

Traditional laser powder bed fusion typically employs lasers with a Gaussian intensity distribution. This type of energy distribution is prone to forming keyholes with a high aspect ratio, which are less stable and can lead to a higher incidence of porosity defects in the fabricated parts. In contrast, when using a flat-top distribution laser for powder bed fusion, the molten pool temperature is more uniform, resulting in a wide and shallow keyhole that exhibits better molten pool stability and a broader process window. On the premise of successfully fabricating high-density Ti6Al4V samples using flat-top laser powder bed fusion, this paper investigates the effects of process parameters on the microstructure and mechanical properties. The study reveals that although higher heat input (low scan spacing and scan speed) is not conducive to the refinement of beta grains, the heat accumulation may induce an in-situ heat treatment effect, promoting the decomposition of martensite and the formation of extremely fine alpha/beta lamellar structures with alpha lath widths of approximately 300 nm. The tensile strength of samples fabricated using flat-top laser powder bed fusion is generally greater than 1000 MPa. Increasing the heat input can facilitate the decomposition of martensite. When the martensite is fully decomposed into alpha/beta lamellar structures, the material achieves a combination of high strength (tensile strength of 1255 MPa) and good ductility (elongation of 11.5 %). This study provides new insights and references for the comprehensive control of the mechanical properties of Ti6Al4V fabricated by laser powder bed fusion.

The position estimation accuracy of the traditional model reference adaptive system (MRAS) deteriorates, affected by parameter perturbation and heavy load disturbance, given the complex working conditions of the shaftless rim-driven thruster (RDT). In this study, an MRAS-based sensorless control scheme of permanent magnet synchronous motor (PMSM) drives using extended state observer (ESO) is proposed to enhance the robustness to large load torque change of the sensorless drive. Quasi-resonant (QR) controller is embedded in the ESO to improve the estimation performance of periodic disturbance, and the detailed parameter tuning method is assessed using the stability analysis. In addition, a supertwisting sliding mode control (STM)-based adaptive mechanism is used to replace the PI-based adaptive mechanism, considering the linear structure and limited bandwidth of the PI controller. Finally, comparative experiments on a 2-kW PMSM drive platform illustrate the validity of the proposed sensorless control method under various working conditions to the traditional control scheme.

Accurate calculation of air-gap magnetic field distribution in permanent magnet machine (PMSM) constitutes a critical foundation for the design and optimization of electromagnetic performance in machines. This paper presents a complete analytical subdomain model for predicting the airgap field distribution in consequent-pole PMSM with the spoke and surface-mounted hybrid permanent magnet (SSHPM) rotor accounting for tooth-tips and slotting effect, during open-circuit, armature reaction and on-load conditions. Taking a 30-pole/27slot SSHPM rotor PM machine as an example, a comparative analysis between analytically computed air-gap flux density and torque and 2-D finite element analysis (FEA) results is conducted, demonstrating excellent agreement between analytical and numerical solutions, thereby verifying the fidelity of the proposed analytical model.

This paper describes an optimal torque per peak current control method for a five-phase permanent magnet (PM) machine considering both 3 rd and 5 th harmonic currents.These optimal ratios to the fundamental component are analytically derived to maximize the output torque.It is found that except for the 3 rd harmonic current contributing to the output torque, the 5 th harmonic current can also produce the additional positive torque.However, the 5 th harmonic is zero sequence component for the five-phase machines, which does not exist in the phase windings.Hence, the neutral point is required to connect the middle point of the DC link capacitors for constructing flowing path.The conventional vector space decomposition (VSD) control is extended to zero sequence sub-plane, which can quantitatively control 5 th harmonic current.For a prototype five-phase PM machine, the average torque can be increased by 21.4% with 3 rd harmonic current injection.Meanwhile, 10.7% additional positive torque is achieved together with 3 rd and 5 th harmonic injection.The torque ripple remains similar to that without harmonics injection.Finally, the experiments are given to demonstrate the theoretical analysis.

This paper presents a two-dimensional exact subdomain model for motor magnetic field prediction in the design of rim-driven permanent magnet machine. Based on the proposed model, the electromagnetic performances under various conditions can be evaluated. The proposed model is universally applicable to permanent magnet machines accounting for the effects of both stator and rotor slotting with any pole and slot combinations. Taking a 24-slot/20-pole rim-driven permanent magnet machine as an example, the analytical results issued from this model are evaluated by comparing them with the results issued from finite element analysis model, verifying the accuracy of the presented model.

Due to nonideal factors such as initial integrator conditions, parameter mismatches, converter nonlinearitles, and measurement errors, rotor flux estimation using conventional rotor flux observer is prone to DC offsets and harmonic distortion. This paper proposes a frequency adaptive observer based on active rotor flux observer. Experimental results demonstrate that the method significantly reduces harmonics and speed ripple, achieving superior control accuracy compared to existing methods.

Unlike traditional permanent magnet synchronous motors (PMSMs), the vernier PM motors (VPMMs) commonly suffer from a low power factor. The purpose of this article is to develop a parameter-layered-based multiobjective optimization method for a surface-mounted vernier PM motor surface-mounted vernier permanent-magnet motor (SVPMM), aiming to enhance the power factor. By deriving the power factor expression, the optimization of power factor can be converted to optimize the no-load back electromotive force (EMF) and q-axis inductance. With the help of sensitivity analysis, the key is to implement the parameter layering and optimization objective decoupling simultaneously, thus, jointly employing with the response surface (RS) method and artificial bee colony (ABC) algorithm for layers 1 and 2, respectively, to quickly obtain satisfactory optimization solutions compared to conventional motor design approaches. The performance comparison between the initial and optimized SVPMM is conducted by using the finite element analysis (FEA), and the experimental verification is also carried out, which evidences the validity of power factor enhancement after the proposed parameter-layered-based multiobjective optimization.

The sensorless control system of permanent magnet synchronous motor (PMSM) is affected by periodic disturbances such as cogging torque, resulting in significant speed fluctuations and even oscillations in the low-speed region. In order to achieve smooth speed control in the low-speed operation, active disturbance rejection control (ADRC) based on generalized integrator extended state observer (GIESO) is proposed to suppress periodic torque disturbance. The effectiveness of the proposed method is verified on the dSPACE DS1202 experimental platform.

Because of the advantages of high power factor and high power, and has been gradually applied in the field of industrial drive. The permanent magnet assisted synchronous reluctance motor has been widely applied in the field of industrial drive. The drive motor requires large output torque, high power factor and small torque ripple, thereby imposing more stringent demands on motor optimization. However, due to the complex rotor structure with the complex magnetic barrier, the optimization parameters of the permanent magnet assisted synchronous reluctance motor is large. Aiming at the above-mentioned problems, a three-step optimization method is studied. The relationship between the rotor structural dimensions is studied to reduce the number of parameters to be optimized. The parameter sensitivity is used to optimize the structure parameters. The response surface method and genetic algorithm are combined used to realize the comprehensive optimization of multi-objective. Then, the parameters with high sensitivity of single target are optimized by the single parameter scanning method. Finally, the structural detail of the magnetic barrier tip is precisely optimized to reduce the torque ripple. A 15kW / 1500rpm permanent magnet assisted synchronous reluctance motor is optimized by the three-step optimization method. The simulation and experimental results are presented to verify the improvement of the motor performance.

In model-free predictive current control (MFPCC), the existing current gradient updating schemes for single-vector MFPCC are difficult to be directly applied to multi-vector MFPCC. The purpose of this paper is to propose a novel double-vector model-free predictive current control (DV-MFPCC) for symmetrical six-phase surface vernier permanent magnet motor (SSP-SVPMM). The key is to take advantage of unique feature in surface-mounted PM motor that the natural response components of current gradients caused by different voltage vectors (VVs) are the same and the forced response components are proportional to the amplitude of VVs, thus using only one measured current gradient to achieve current gradients real-time updating caused by all candidate VVs. Furthermore, the duty cycle of non-zero VV is calculated through the q-axis current gradient to reduce the torque and speed ripple, and its validity is verified by comparative simulation results.

In order to balance the torque density and utilization of permanent magnet (PM) material in large air gap rim-driven thruster (RDT), a three-segment Halbach array consequent-pole PM rim driven machine (HCPM-RDM) with unequal pole arc is proposed in this paper. In this design, the proposed HCPM-RDM can significantly reduce the PM volume, while taking advantage of the flux focusing effects of the Halbach structure, and improve the torque density. To satisfy the operating requirements of the RDT, a multi-objective stratified optimization design is conducted, in which the response surface (RS) coupled genetic algorithm (GA) and particle swarm optimization (PSO) algorithm are purposely utilized. Then, the electromagnetic performance of the HCPM, CPM, SPM machinesis extensively compared, which include the cogging torque, electromagnetic torque, torque ripple, loss and efficiency. Finally, the RDM prototype is tested to verify the effectiveness of corresponding optimization design and finite element analysis (FEA).