Search Results (84)

Conventional flux-reversal permanent magnet motors have problems such as excessive torque ripple and rich harmonic content in direct drive applications such as oil exploration, which restrict their application in high-precision scenarios. To address this issue, this paper presents a hybrid excitation topology that integrates double-armature windings, stator Halbach hybrid permanent magnet arrays, rotor-staggered unequal-tooth and rotor-hybrid permanent magnets. Two-dimensional finite element analysis was conducted using ANSYS Maxwell 2023 R1 to evaluate electromagnetic performance under rated steady-state conditions, rated power 300 kW, rated speed 83 rpm, rated voltage 660 V, rated phase current 307 A, and axial core length 200 mm. The simulation results show that the proposed topology has an average output torque of 34.5 kN·m at rated conditions compared with the traditional flux-to-reverse permanent magnet motor of the same size, and the torque ripple rate is reduced from 27.5% to 17.4%, a relative reduction of 36.8%. The results are based only on numerical simulation and have not been verified by physical prototype experiments. Dynamic control strategies, multi-load transient responses and experimental verification will be carried out in subsequent work. Full article

The growing demand for compact and high-performance motors in industrial robotic joints has intensified interest in axial flux permanent magnet motors (AFPMs), which inherently offer high torque density and a thin form factor compared with conventional radial flux permanent magnet motors (RFPMs). Among various AFPM structures, printed circuit board (PCB) Stator motors have gained significant attention due to their slotless configuration, reduced cogging torque, low vibration and acoustic noise, and enhanced geometric thinness enabled by PCB-etched conductors. This study proposes a conductor arrangement strategy that mitigates back-EMF imbalance in concentrated-winding single-rotor PCB AFPM for robotic joints. Several conductor configurations are analyzed and compared through electromagnetic finite-element evaluation, and an optimized arrangement is identified that effectively improves phase EMF symmetry while maintaining structural thinness. The results provide design guidelines for high-performance PCB AFPMs suitable for next-generation robotic actuators. Full article

This study proposes a printed circuit board (PCB) stator pattern for alleviating the trade-off between DC copper loss and AC winding loss in a slotless axial flux permanent magnet motor (AFPM). The proposed pattern has a structure in which the width of the effective conductor region directly exposed to time-varying magnetic flux is reduced, and two additional conductors with the same width are placed within the available axial space and then connected in parallel through vias. Three-dimensional finite element analysis was performed while varying the effective conductor width ratio from 0.3 to 0.8, and an additional refined sweep was conducted in the range of $\alpha$ = 0.5–0.6, where the minimum total winding loss appeared in the initial sweep. Under the rated operating condition, the minimum total winding loss was obtained at $\alpha =0.53$ based on the refined sweep results. Under this condition, the phase resistance, DC copper loss, AC winding loss, and total winding loss were reduced by 11.82%, 12.1%, 15.09%, and 12.48%, respectively. As a result, the efficiency increased from 81.53% to 83.5%, while the back electromotive force (BEMF), torque, and output were nearly unchanged. In addition, the AC winding loss distribution decreased in both the coil region closest to the magnets and the coil region farthest from the magnets. These results demonstrate that the proposed pattern is an effective design method for improving the winding loss characteristics of slotless PCB AFPM without meaningful degradation of the fundamental electromagnetic performance. Full article

Electric power steering (EPS) motors require low torque ripple, low cogging torque, and smooth torque output to ensure precise control and driving comfort. However, consequent pole permanent magnet synchronous motors (CP-PMSMs), although advantageous in reducing permanent magnet usage, exhibit an imbalanced magnetic flux distribution due to the iron poles, resulting in even-order harmonic components in the back electromotive force (BEMF) and significant torque ripple. In this paper, a rotor pole arrangement for CP-PMSMs is proposed to improve torque characteristics for EPS applications. Symmetric and asymmetric pole arrangements are introduced to modify the magnetic flux distribution and suppress harmonic components generated by the iron poles. In addition, the iron pole arc ratio is selected as a key design variable and analyzed for each model to achieve low torque ripple while maintaining torque performance. The electromagnetic characteristics of the proposed structures are evaluated using finite element analysis under identical operating conditions. The results show that the torque ripple of the proposed models is reduced by approximately 33.3%p and 34.1%p compared with the conventional CP-PMSM, and the cogging torque is also significantly reduced. Although average torque decreases, overall torque characteristics improve due to reduced torque ripple and harmonic components. These results demonstrate that the proposed rotor pole arrangement effectively enhances torque quality in CP-PMSMs without increasing axial length or requiring three-dimensional analysis. Full article

With the rapid proliferation of industrial robots, compact electric motors have become increasingly critical for robot joint actuation. This paper proposes a fan–trapezoidal combined magnetic pole and auxiliary pole structure. A three-dimensional simulation model of a disk-type motor incorporating this magnetic pole configuration is established using the finite element analysis method. Its electromagnetic characteristics are then investigated through finite-element simulations and optimization analysis. With the total harmonic distortion (THD) of the air-gap flux density as the primary optimization objective, the optimal design is selected by adjusting the fan–trapezoidal pole angle and the dimensions of the soft magnetic auxiliary poles. The accuracy of parametric optimization is subsequently verified by employing the multi-objective genetic algorithm (MOGA). The results indicate that for a coreless axial-flux permanent magnet motor equipped with the proposed fan–trapezoidal combined poles and auxiliary poles, the THD of the air-gap flux density is reduced to 3.53%. This represents a reduction of 38.72% compared to an optimized conventional modular-pole structure. Furthermore, the harmonic distortion rate of the no-load back electromotive force decreased by 83.91%. The sinusoidal characteristics of the air-gap flux density waveform are significantly improved. This work provides insights into the design of coreless axial-flux permanent magnet motors. Full article

The Axial Flux Permanent Magnet Synchronous Motor (AFPMSM) has gained significant attention as a core power source for next-generation industrial sectors, including electric vehicles, wind turbines, robot joints, and drone propulsion motors, due to its high power density from a short axial length and large radial dimensions. Despite these structural advantages, cogging torque caused by magnetic interaction between the stator teeth and permanent magnets remains a critical drawback, inducing noise and vibration. While conventional Soft Magnetic Composite (SMC) core methods facilitate 3D flux paths, they suffer from low magnetic permeability, insufficient mechanical strength, and manufacturing complexity. To address these issues, this study proposes a stepped structure model utilizing electrical steel sheets to effectively reduce cogging torque. This structure features radial stacking of identical electrical steel sheets with varying widths, where each layer’s center is incrementally shifted in the rotational direction. This configuration achieves an effect analogous to continuous skewing without specialized 3D machining. To validate the proposed design, 3D Finite Element Analysis (FEA) was conducted. Results demonstrate that the peak-to-peak cogging torque was reduced to approximately 86% of the conventional model’s value, while maintaining the back-EMF reduction rate within 5%. By presenting a novel skewing technique, this research provides a practical alternative for high-precision and high-power AFPMSM. Full article

Axial Flux Permanent Magnet Synchronous Motors (AFPMSMs) are gaining increasing attention for their application in electric vehicle (EV) drive systems. Their high torque density and compact axial geometry make them attractive for high-performance EV drive systems. However, cogging torque remains a major challenge, degrading low-speed drivability, noise performance, and control stability. This article proposes a magnet skew on rotor modulation structure using a genetic algorithm (GA) to reduce cogging torque in AFPMSMs utilizing a 12/15 non-integer pole/slot arrangement. The objective of optimization is to simultaneously reduce cogging torque under identical electromagnetic constraints. A complete three-dimensional finite element model (3D-FEM) incorporating nonlinear magnetic material properties has been developed to evaluate the electromagnetic field distribution and torque components. The results indicate that a 12/15 non-integer pole/slot arrangement improves harmonic distribution and extends the operating range with lower cogging torque compared to integer pole/slot designs. Combined with GA-optimized skew angles, this reduces peak-to-peak cogging torque to less than 50%. This design is ideally suited for the traction requirements of electric vehicles, including premium electric vehicles where smooth operation at low speeds is critical. Full article

Recently, the demand for electric motors that can achieve high performance while ensuring stable magnet supply has continued to increase across various industrial sectors. Although rare-earth permanent magnets, such as neodymium and samarium cobalt, enable superior electromagnetic performance, their high cost and supply instability have motivated growing interest in motors employing non-rare-earth permanent magnets, such as ferrite magnets. Due to the relatively low remanent flux density and coercivity of non-rare-earth magnets, spoke-type rotor structures are commonly adopted to enhance flux concentration. However, spoke-type configurations inherently suffer from axial leakage flux, in which a portion of the magnetic flux generated by the permanent magnets fails to link with the stator and instead leaks along the axial direction. This axial leakage flux reduces the effective air-gap flux density, leading to a degradation of back electromotive force (back-EMF) and overall motor performance. In this study, a double-spoke-type motor employing asymmetric permanent magnet geometry is investigated. Finite element analysis (FEA) is performed to identify an effective rotor structure that reduces axial leakage flux without increasing magnet usage, demonstrating the feasibility of performance improvement in non-rare-earth permanent magnet motors. Full article

This paper presents a detailed parametric optimization of a spoke-type double stator and single-rotor (DSSR)-type axial flux permanent magnet (AFPM) motor based on the design of experiment (DoE) method coupled with 3D finite element analysis (FEA). Design variables are selected, and their individual effects on the output characteristics of the spoke-type DSSR AFPM motor are analyzed. The interactive effects of the design variable pairs are also investigated to understand their mutual influence on the spoke-type DSSR AFPM motor’s output characteristics. For the optimal design of the spoke-type DSSR AFPM motor, different values of each design variable are determined using Latin Hypercube Sampling (LHS) and analyzed using the 3D FEA method. Full article

Electric Water Pumps (EWPs) are being adopted more widely to improve thermal management in internal combustion engines and electrified powertrain systems. In this context, the drive motor must deliver high efficiency and reliability despite a strict volume constraint. This paper addresses a key drawback of coreless printed circuit board (PCB) stator axial-flux permanent-magnet machines for EWP use: the PCB traces are directly exposed to the magnet flux, which increases AC loss, while the required phase resistance also leads to non-negligible DC copper loss. To mitigate both loss components within the same conductor design space, a pyramid trace concept is introduced. A magnetic equivalent circuit (MEC) based model is first used to estimate the baseline performance as the number of PCB stator modules changes, and the resulting scalability is examined in terms of module commonality. The final design then applies the pyramid trace layout with a layer-dependent trace width that is narrower on the layers closer to the magnets and wider on the layers farther away—the trade-off between AC loss and DC loss is optimized using 3D finite element analysis. Torque predictions from the simplified MEC model are cross-checked against 3D finite element analysis (FEA), and finally, a prototype is built to validate the analysis with experimental measurements; for the final selected model, the torque prediction error is 2.37% compared with the validation result. Full article

This paper proposes a multiphysics-based optimal design process for a 750 W axial-flux ferrite consequent-pole (AFCP) pump motor aimed at reducing permanent magnet usage. To mitigate the high computational cost associated with repetitive numerical analyses, a metamodel (surrogate model)-based optimization framework is adopted. A consequent-pole (CP) structure is applied to an initial ferrite axial-flux permanent magnet (AFPM) motor, and ten key design variables are selected for optimization. The electromagnetic performance corresponding to variations in these variables is evaluated using three-dimensional finite element analysis (3D FEA), and the resulting dataset is used to construct metamodels. In AFPM motors incorporating ferrite permanent magnets and a CP structure, electromagnetic performance, thermal saturation, and structural stability collectively limit reliable operation. Therefore, a multiphysics-based evaluation is essential. The optimal design is assessed through electromagnetic, thermal, and structural finite element analyses. According to the 3D FEA results, the optimal model achieves a 46.85% reduction in permanent magnet volume while improving efficiency by 0.75%, reaching 95.53%, compared to the initial model. The torque ripple and peak-to-peak cogging torque are reduced by 28.81% and 31.37%, reaching 0.08 Nm and 0.06 Nm, respectively. In addition, the total harmonic distortion (THD) of the back-electromotive force waveform decreases from 12.4% to 2.53%. Stable operating characteristics are confirmed through demagnetization, thermal, and structural analyses, demonstrating that the proposed optimal design process successfully achieves both permanent magnet reduction and overall performance improvement in ferrite-based AFCP motors. Full article

Wheel load is a critical information source reflecting the status of vehicle load distribution and motion. Yet, existing in-wheel motor products are primarily designed as propulsion units and inherently lack the load-sensing capabilities required by intelligent vehicles. To address this research gap, this paper presents a novel intelligent electric drive wheel (i-EDW) with an integrated transmission system and a load-sensing unit (LSU). The i-EDW adopts an Axial Flux Permanent Magnet Synchronous Motor (AFPMSM), while the integrated LSU ensures high-precision measurement of six-dimensional wheel forces and moments. According to this multi-axis force information, a real-time estimation and stability control method based on the tire–road friction circle concept is proposed. Instead of the complex decoupling and multi-objective optimization with the multi-actuator systems, this paper focuses on minimizing the tire load rate of i-EDWs, which significantly advances the state of the art in terms of calculation efficiency and respond speed. To validate this theoretical framework, a full-vehicle model equipped with four i-EDWs is developed. In the MATLAB R2022A/Simulink co-simulation environment, a virtual prototype is tested under typical driving scenarios, including the straight-line acceleration and double-moving-lane (DML) steering. The simulation results prove a reliable safety margin from the friction circle boundaries, laying a solid foundation for precise motion control and improved system robustness in future intelligent vehicles. Full article

Permanent Magnet Synchronous Generators (PMSGs) have become increasingly important in industrial applications such as wind turbine systems due to their high efficiency and power density. However, their operational reliability can be affected by asymmetries such as static eccentricity (SE) and load current unbalance (UnB), which exhibit similar spectral features and are therefore difficult to differentiate using conventional techniques such as Motor Current Signature Analysis (MCSA). Stray flux analysis provides an alternative diagnostic approach, yet single-point measurements often lack the sensitivity required for accurate fault discrimination. This study introduces a diagnostic methodology based on the Space Vector Stray Flux (SVSF) for identifying static eccentricity (SE) and load current unbalance (UnB) faults in PMSG-based systems. The SVSF is derived from three external stray flux sensors placed 120° electrical degrees apart and analyzed through symmetrical component decomposition, focusing on the +5f_s positive-sequence harmonic. Two-dimensional Finite Element Analysis (FEA) conducted on a 36-slot/12-pole PMSG model shows that the amplitude of the +5f_s harmonic increases markedly under static eccentricity, while it remains nearly unchanged under load current unbalance. To validate the simulation findings, comprehensive experiments have been conducted on a dedicated test rig equipped with high-sensitivity fluxgate sensors. The experimental results confirm the robustness of the proposed SVSF method against practical constraints such as sensor placement asymmetry, 3D axial flux effects, and electromagnetic interference (EMI). The identified harmonic thus serves as a distinct and reliable indicator for differentiating static eccentricity from load current unbalance faults. The proposed SVSF-based approach significantly enhances the accuracy and robustness of fault detection and provides a practical tool for condition monitoring in PMSG. Full article

Reducing iron loss in axial flux permanent magnet (AFPM) motors is critical for improving efficiency. This study proposes a design-optimization procedure that combines 3D finite-element analysis (FEA) data with an artificial neural network (ANN) surrogate. For four design variables—airgap length, rotor back-yoke thickness, stator slot width, and stator slot depth—the search bounds were defined to avoid tooth and back-yoke saturation, and the corresponding space was sampled to construct a dataset. Using this dataset, the ANN was trained and then used to explore low-iron loss solutions. On an independent validation set, ANN predictions showed high agreement with 3D-FEA reference values, enabling rapid evaluation of many design candidates. As a result of the optimization, total iron loss decreased relative to the baseline, and torque increased by 3 Nm. These results demonstrate that the ANN-based surrogate model can reliably perform geometry-dependent iron loss optimization in AFPM motors, providing a fast and accurate alternative to repetitive 3D-FEA evaluations. Full article

Axial Flux Permanent Magnet Synchronous Motor (AFPMSM) offers high power density in structures with short axial lengths and large radial dimensions, making it attractive for applications that require thin structures, such as in-wheel motors. This study proposes an AFPMSM design process applicable under fixed inner/outer diameter and axial length constraints. The proposed process is presented as step-by-step procedures: selection of pole/slot combinations, adjustment of slot depth, determination of stator/rotor dimensional ratios, and slot structure design. It is universally applicable to both bobbin-type rectangular wire windings and shoe-type round wire windings. The validity of the proposed process was verified through finite element method (FEM) analysis, and the differences between the two winding structures were examined through post-processing of the results. By presenting an AFPMSM design methodology that can be consistently applied under constrained spatial conditions, this study provides practical design guidelines for the development of in-wheel motors for next-generation mobility applications. Full article