Search Results (2,373)

In applications with a wide constant power speed range, the use of conventional permanent magnet machines is complicated by their uncontrolled magnetic flux, increased losses at high speeds, increased inverter current, and dangerous open circuit back EMF. For this reason, synchronous machines without magnets and with a field winding on the rotor are increasingly being used in traction applications. However, due to high electrical losses in the field winding, rotor cooling becomes a critical issue. An alternative is to use hybrid excited machines, which retain the advantages of electrically excited machines while significantly reducing rotor losses. This paper presents a comparison between a conventional electrically excited machine and a novel hybrid excited machine for traction applications with a wide constant power speed range of 9.3:1 (4200 to 450 rpm, mechanical power 23.6 kW). Both machines have the same external dimensions and were optimized using the same optimization algorithm. It is shown that the hybrid excited machine provides a reduction in rotor losses by 1.8–2.8 times depending on load conditions. Its total loss is also reduced, although its cost of active materials increased by a factor of 2.8 due to the use of permanent magnets. Full article

A line-start permanent-magnet motor (LSPM) combines the direct-on-line starting capability of a squirrel-cage induction motor (IM) with permanent-magnet-assisted synchronous operation. Previous studies on LSPM winding connections have mainly focused on load-dependent efficiency and the power factor, while their effects on harmonics, torque ripple, and synchronization across different rotor configurations remain unclear. This study compares Y- and delta-connected windings in two 5.5 kW, four-pole LSPM models using transient finite-element analysis. Current and voltage harmonics, losses, efficiency, torque ripple, and synchronization response were evaluated. The Y-connected cases exhibited lower current harmonic distortion and stator copper loss, whereas the delta-connected cases reduced torque ripple and maximum speed overshoot but required slightly longer settling times. For LSPM-B, the Y connection achieved the highest efficiency of 92.92% with a stator copper loss of 137.81 W, while the delta connection reduced the torque ripple ratio from 43.8% to 39.5%. These results demonstrate that winding-connection effects depend on the rotor magnetic circuit and cage-assisted starting characteristics, requiring a trade-off among efficiency, harmonic loss, torque ripple, and synchronization response. Full article

Facing strict requirements on reliability, power density, vibration and noise for electrified underwater propulsion (EUP) drive motors, this paper investigates dual three-phase winding selection and structural parameter multi-objective optimization of a 24-slot/22-pole surface-mounted permanent magnet (PM) synchronous motor (PMSM). According to winding function theory and magnetomotive force (MMF) harmonic analysis under normal and faulty operation, a double-layer 30° phase-shifted (DL30°) winding is chosen, which is proven to boost torque output and attenuate torque ripple via finite-element (FE) analysis. Key dimensions are globally optimized by the multi-objective particle swarm optimization algorithm, yielding a 5.36% torque density rise and a 41.46% reduction in torque ripple. Prototype experiments agree well with simulations and validate the design strategy. Full article

To mitigate the chattering and limited adaptability of conventional sliding mode observers (SMOs) in position sensorless control for permanent magnet synchronous motors (PMSMs) across a wide range of operating conditions, a control strategy based on an adaptive-gain super-twisting sliding mode observer (AST-SMO) combined with improved particle swarm optimization (PSO) for speed loop PI parameter tuning is proposed. The observer incorporates a time-varying gain function, which is driven by the magnitude of the current observation error and governed by an integral-type adaptive law. This replaces the fixed-gain structure that necessitates a predetermined disturbance upper bound, thereby effectively suppressing chattering and ensuring high estimation accuracy across a wide speed range and under abrupt load changes. For speed loop control, an improved PSO algorithm with cooperative adjustment of learning factors and inertia weight is introduced for offline optimization of PI parameters, further enhancing dynamic response and anti-disturbance capability. Simulation and experimental results demonstrate that, compared with the traditional ST-SMO and LST-SMO, the proposed AST-SMO yields lower rotor position estimation errors and reduced speed fluctuations under both steady-state and transient conditions. Meanwhile, the PSO-optimized PI controller significantly shortens settling time and reduces overshoot. The proposed strategy features a simple structure and is suitable for engineering implementation. Full article

This structured critical review examines wearable brain–computer interface (BCI) systems that integrate electroencephalographic (EEG) and electromyographic (EMG) signals for post-stroke motor rehabilitation. The central engineering problem is the spatio-temporal heterogeneity between cortical and muscular signals, which limits the reliability and generalizability of conventional EEG–EMG fusion. We review acquisition and synchronization methods, data-, feature-, and decision-level fusion, deep-learning architectures, wearable implementation, and clinically oriented closed-loop rehabilitation. Conventional fusion can exploit complementary information but usually treats the cross-modal relationship as fixed. By contrast, dynamic brain–muscle coupling is defined here as the explicit, time-resolved estimation of interaction strength, delay, directionality, or network topology between cortical regions and target muscles. Measurable candidates include time-resolved corticomuscular coherence, phase locking, lagged dependence, information-theoretic directionality, and dynamic graph connectivity. Coupling-aware and graph-based methods are promising, but clinical translation remains constrained by artifacts, inter-subject and cross-session variability, overfitting, limited clinical datasets, interpretability, synchronization error, and embedded-computing requirements. The review therefore proposes a transparent pathway from static signal stacking toward physiologically grounded, dynamically coupled, and adaptively controlled rehabilitation systems. Full article

Fast-switching transients and high dv/dt associated with PWM inverters exacerbate the reflected-wave effects in the motor feeder cable. This leads to higher motor-side overvoltages, which increase the stress on the motor winding insulation, potentially accelerating insulation degradation and increasing the risk of partial discharge within the motor windings. Moreover, the common-mode voltages at the motor terminals propagate through parasitic capacitive paths within the motor, inducing shaft voltages that lead to electric discharge machining (EDM) currents and premature bearing failure. This paper experimentally investigates the influence of motor feeder cable length and type (shielded and unshielded) on motor terminal overvoltage, shaft voltage, and bearing current behavior in an inverter-fed 11 kW permanent magnet synchronous motor drive system. Three cable lengths (1 m, 3 m, and 16 m) with shielded and unshielded configurations are evaluated under identical operating conditions. Measurements of line-to-line voltage, line-to-ground voltage, shaft voltage, bearing current, and EDM discharge currents are recorded and statistically analyzed to assess the influence of cable configuration. The study also examines the influence of the motor grounding configuration on common-mode current and bearing current behavior. Overall, the findings provide comprehensive insights into the influence of motor feeder cable on overvoltage, shaft voltage, and bearing discharge behavior, supporting informed cable selection for WBG inverter-fed electric drives. Full article

A torque-preserving flux-weakening control strategy combining q-axis current compensation with a bandwidth-based speed-adaptive voltage regulator is proposed for interior permanent magnet synchronous motor (IPMSM) drives. The conventional negative d-axis current compensation method is first analyzed, showing that the associated current-vector variation can cause transient torque deviation during flux-weakening operation. A q-axis current compensation law is therefore derived based on the torque-preservation condition. In addition, a speed-dependent tuning law for the voltage closed-loop regulator is developed through frequency-domain analysis, with the voltage-loop bandwidth as the principal design parameter. Experimental results show that, compared with the conventional method, the proposed strategy reduces the torque-fluctuation amplitude from 2.35 N·m to 1.83 N·m, corresponding to a reduction of approximately 22.1%, and suppresses the approximately 9% q-axis current overshoot observed with the conventional method. Under a sudden-load condition, the maximum speed dip is reduced from 66 r/min to 61 r/min (7.6%), while the recovery time is shortened from 0.28 s to 0.25 s (10.7%). These results demonstrate improved transient torque stability and disturbance-rejection performance in the flux-weakening region. Full article

This study investigated the effects of high-definition transcranial alternating current stimulation (HD-tACS) on cognitive–motor dual-task performance and upper-limb multi-joint motor control. Sixteen right-handed healthy male participants completed a double-blind, randomized crossover experiment involving active tACS and sham tACS conditions separated by a one-week washout interval. A 4 × 1 HD-tACS montage was applied over the left dorsolateral prefrontal cortex at 5 Hz for 20 min. Participants performed a synchronous cognitive–motor dual-task paradigm that combined an N-back working memory task with an upper-limb throwing task under different task difficulty levels. Task performance outcomes included accuracy, reaction time, release velocity, peak velocity, movement duration, and dual-task cost. Upper-limb motor control outcomes included elbow and wrist joint range of motion, peak angular velocity, and peak joint flexion and extension moments. Accuracy showed a significant Stimulation × Time interaction. Under active stimulation, adjusted accuracy increased by 5.4 percentage points in N1 and 10.1 percentage points in N2, whereas the corresponding changes under sham stimulation were not significant. Reaction time, release velocity, peak velocity, and movement duration showed no significant stimulation-related changes. Release-velocity DTC also showed a significant Stimulation × Time interaction across N1 and N2. Under active stimulation, the signed DTC shifted upward, indicating a smaller release-velocity decrement relative to N0. The task-specific follow-up was significant for N2 but not N1; however, the Stimulation × Time × Task interaction was not significant. Most upper-limb kinematic and kinetic outcomes showed no significant stimulation-related changes. Active HD-tACS was associated with higher accuracy and a favorable shift in release-velocity DTC, while most motor, kinematic, and kinetic outcomes were unchanged. The effects were limited to selected behavioral outcomes and did not differ significantly between N1 and N2. Full article

Incipient stator interturn short-circuit faults in permanent magnet synchronous motors produce only weak changes in the terminal currents, which limits the sensitivity of conventional amplitude- and unbalance-based indicators. This paper proposes a phase-wise diagnostic framework that combines multiscale sample entropy (MSE), topological data analysis (TDA), and a Gaussian mixture model (GMM). For each three-period current window, ten scale-dependent sample-entropy components and two persistent-entropy components are concatenated into a 12-dimensional feature vector. A separate GMM is trained for each phase using healthy data only. The resulting likelihood-based health scores are used for fault detection and faulty-phase localization, while physically defined score boundaries calibrated from measured short-circuit-current groups are used for severity assessment. Experiments on a 1.5 kW, 8-pole, 12-slot PMSM demonstrate class-wise recalls of 96.50–100% and an overall accuracy of 97.50% under the investigated operating conditions. The results show that the combined temporal and topological representation can reveal weak current changes that are difficult to distinguish using conventional terminal-current indicators. Full article

Driven by the engineering requirement for high acoustic stealth of unmanned underwater vehicles (UUVs), this paper investigates the electromagnetic vibration of an 8-pole, 48-slot, surface-mounted permanent magnet synchronous motor (SPMSM) employed in the propulsion system through multi-physics coupling analysis and experimental testing. First, analytical calculations of electromagnetic force waves are performed based on the Maxwell stress tensor method and the magnetomotive force–permeance method to analyze the spatial orders, temporal orders, and sources of the harmonics. Then, a two-dimensional motor model is established using ANSYS electromagnetic field simulation software to investigate the temporal and spatial characteristics of electromagnetic force waves under both no-load and on-load conditions. Fourier decomposition is applied to obtain the amplitude-frequency characteristics, thereby verifying the correctness of the analytical results. Subsequently, three-dimensional models of the stator core and the complete stator assembly are constructed in the physical field, and their modal frequencies and mode shapes are obtained through simulation. On this basis, harmonic response analysis is conducted by applying electromagnetic force waves to the stator teeth, and vibration simulations are performed in ANSYS Workbench to acquire vibration characteristics. Vibration experiments are then carried out at multiple rotational speeds, and the experimental results are compared with the simulation results to validate the feasibility and accuracy of the finite element modeling approach. Since the measured motor vibration results are influenced not only by electromagnetic excitation forces, but also by various factors such as mechanical structure, instrument installation, and fixture conditions, while the simulation model in this paper inevitably simplifies damping, housing details, inverter control effects, and considers only the effect of radial electromagnetic forces, there exists a certain discrepancy between the simulated and measured motor vibration acceleration results. However, the main vibration trends in the low-frequency range below 800 Hz are basically consistent, particularly at the second and fourth harmonic frequencies, where the vibrations are electromagnetic vibrations caused by radial electromagnetic force waves, with relative errors between the measured and simulated values of 18% and 25%, respectively. This finite element model can be used for preliminary design evaluation of PMSMs and rapid prediction of electromagnetic vibration, providing researchers with a convenient and practical research approach and methodology. Finally, by analyzing factors that may influence motor vibration, this paper proposes design modifications to the stator structure and air-gap width, providing an optimized solution for reducing electromagnetic vibration of the permanent magnet synchronous motor and avoiding resonance. Full article

For the problem of additional copper loss, iron loss, and efficiency degradation caused by current harmonics in surface-mounted permanent magnet synchronous motor (SPMSM), this study proposes a novel optimization strategy based on harmonic current and the conventional loss minimization control (LMC) strategy, namely Harmonic-Current-Inclusive Loss Minimization Control (HCI-LMC). For the 5th, 7th, and 11th current components, a compensatory harmonic voltage injection scheme is adopted for suppression. Simulation studies are conducted to verify the effectiveness of the proposed optimization strategy. The total harmonic distortion (THD) of the stator current is reduced from 14.87% to 1.36%, and the amplitudes of the 5th, 7th, and 11th harmonics are attenuated by 82.6%, 80.0%, and 79.3%, respectively. The results indicate that HCI-LMC can significantly suppress harmonic losses and improve the overall motor efficiency by 1.32% compared with the conventional LMC strategy. Full article

Permanent Magnet Synchronous Motors (PMSMs) are widely employed in electric vehicle (EV) propulsion systems because of their high efficiency, high power density, and superior dynamic performance. The performance of field-oriented control (FOC)-based PMSM drives strongly depends on accurate tuning of the proportional–integral (PI) controllers governing the speed and current loops. Conventional tuning approaches often optimize a single performance index and therefore fail to simultaneously enhance the dynamic behavior of all control loops. This paper proposes a multi-error Integral of Time-weighted Absolute Error (ITAE)-based optimization framework for simultaneous tuning of the PI controllers by minimizing a composite objective function that incorporates the time-weighted absolute errors of the rotor speed, q-axis current, and d-axis current. To validate the effectiveness and optimizer independence of the proposed framework, five metaheuristic optimization algorithms—Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Gray Wolf Optimizer (GWO), Gazelle Optimization Algorithm (GOA), and White Shark Optimization (WSO)—are evaluated under identical optimization settings. MATLAB/Simulink simulations are performed for reference-speed tracking, load disturbance rejection, and variable-speed operation. The results demonstrate that the proposed optimization framework consistently improves tracking accuracy and dynamic response regardless of the selected optimizer, while WSO provides the best overall performance. In the variable-speed tracking scenario, WSO achieved the lowest RMSE of 0.96 rad/s and the minimum ITAE value of 0.1716, confirming its effectiveness as the most suitable optimizer for the proposed framework in high-performance PMSM drive applications. Full article

Few-shot compound fault diagnosis of induction motors can be overestimated when correlated windows from the same continuous run are split across support and query sets. This study develops a run-disjoint few-shot framework in which each complete experimental run is treated as one shot and support and query sets are separated by run ID. Forty-eight multidomain features are extracted from synchronized triaxial vibration windows, classified using task-specific XGBoost, and aggregated to obtain run-level predictions; TreeSHAP provides post hoc feature attribution. In a matched comparison with identical query runs and windows, window-mixed partitioning increased the task-level mean run-level Macro-F1 from 0.9212 to 0.9934. After repeated predictions were aggregated over 108 unique query runs, the corresponding difference was 0.0093 with a 95% paired-bootstrap confidence interval of [0.0000, 0.0282], showing that the estimated magnitude depends on the statistical unit. Under the predefined strict 3-shot protocol, XGBoost achieved a Macro-F1 of 0.9263 and run-level accuracy of 0.9292. Additional sensitivity and controlled comparisons showed that performance depends on within-run sampling, representation, and classifier design, while strict cross-speed tests revealed the limitation of fixed-frequency features under rotational-speed shifts. The framework provides a leakage-aware evaluation procedure for few-shot compound-fault diagnosis using independently labeled runs. Full article

Permanent magnet synchronous motors (PMSMs) operating at low speeds are susceptible to parameter mismatches, periodic harmonics, and various internal and external disturbances, which result in steady-state current errors and low-frequency speed oscillations. To address these issues and improve low-speed PMSM performance, an automatic tuning disturbance rejection incremental deadbeat predictive current control (AT-DR-IDPCC) method is proposed. First, an incremental extended-state observer (IESO) is incorporated into the incremental deadbeat predictive current control (IDPCC) framework to estimate and compensate for lumped disturbances caused by resistance and inductance mismatches, thereby improving parameter robustness. Meanwhile, a quasi-resonant controller (QRC) is connected in parallel with the current loop to selectively suppress sixth-order current harmonics induced by inverter nonlinearities and flux harmonics. Furthermore, a deep deterministic policy gradient (DDPG)-based parameter optimization scheme is introduced to automatically tune the controller parameters, overcoming the limitations of conventional trial-and-error tuning and achieving the coordinated optimization of dynamic response, steady-state accuracy, and disturbance rejection capability. Simulation and experimental results demonstrate that, compared with proportional–integral (PI) control and IDPCC incorporating the IESO (IESO-IDPCC), AT-DR-IDPCC reduces the phase current’s total harmonic distortion (THD) by 56.1% and 23.7% while also decreasing the speed fluctuation amplitude by approximately 50% and 20%, respectively. The proposed method significantly enhances the robustness, harmonic suppression capability, and low-speed control performance of PMSM drives. Full article

This paper introduces a direct oil cooling concept for rotor coils of an electrically excited synchronous propulsion motor. The proposed approach utilizes a hollow shaft and two distinct laminations to guide non-conductive, ultra-low-viscosity automotive oil onto the rotor coils. Radial channels are positioned at the rotor center to transfer oil from the hollow shaft to the axial channels at the outer surface of the rotor. Axial channels direct the coolant from the radial channels and splash it onto the rotor end windings. The proposed approach enhances the thermal management of the heat generated by rotor coils, and helps improve the motor performance and power density. Computational fluid dynamics (CFD) simulations were conducted to analyze the effectiveness of the cooling method under various operating conditions. Full article