This paper presents a novel design and optimization methodology for hybrid-dual rotor permanent magnet synchronous machines (HDR-PMSMs) featuring a double-sided stator structure. The machine comprises two distinct rotor types, positioned with an offset angle relative to one another, which enables maximization of torque density. Consequently, the presence of numerous design variables on each rotor side significantly increases the complexity of the design and optimization process. To address this challenge, a combined strategy involving magnetic circuit decoupling (MCD) and waveform targeting surrogate modeling (WTSM) is adopted to facilitate multi-objective optimization. As part of the MCD approach, a set of analytical equations is developed to predict the magnetic flux density in the stator yoke. It is demonstrated that, under unsaturated conditions, the HDR-PMSM can be decoupled into two independently modeled rotor systems, effectively simplifying the overall optimization problem. Furthermore, the WTSM framework reduces the number of finite element (FE) simulations required to identify optimal designs. The effectiveness of the proposed method is validated through a multi-objective optimization process, targeting improvements in average torque, torque ripple, and permanent magnet (PM) volume, while ensuring safe magnetic operation through the consideration of anti-demagnetization constraints.

Wireless power transfer (WPT) is a reliable method for powering implantable medical devices. However, achieving high efficiency with a compact receiver (RX) remains a major challenge. Self-resonant wireless power transfer (SRWPT) systems enhance reliability by using parasitic capacitance within planar coils, eliminating external compensation components. This paper presents a fully self-resonant three-coil PCB system that eliminates external capacitors while improving power transfer efficiency for compact RX coils. The system utilizes three specially designed double-layer coil structures: two dedicated to generating high inductance values (L₂ and L₃), and one configured as an auxiliary coil to further enhance impedance. This arrangement achieves inductances up to four times greater than those of a traditional coil with the same footprint. Through a series combination of mutual inductance (Lm) and mutual capacitance (Cm) within the auxiliary coil network, the resonant frequency and system impedance are significantly increased, leading to improved overall efficiency and system robustness. Moreover, the size mismatch between the transmitter (TX) and receiver (RX) coils necessitates precise synchronization of their resonant frequencies. To achieve this, an air-core structure is employed instead of FR4, allowing flexible frequency tuning through coil spacing adjustments while simultaneously reducing power losses. Simulation results demonstrate that the proposed system achieves a power transfer efficiency of 94.6% at a transmission distance of 10 mm.

Reluctance machines with DC field coil in the stator is a competitive candidate for electric vehicle propulsion due to the elimination of rare-earth permanent magnets (PM), robust structures and controllable excitation. However, their torque density cannot be compared with PM machines. Introducing rare-earth PMs into reluctance machines can be an effective way to boost torque density, but the costs will greatly increase as well. To solve this problem, this paper proposes a hybrid reluctance motor using assistive ferrite magnets in stator slots. The introduced ferrite magnets operate based on the flux modulation effect for torque density improvement. It is revealed by finite element analysis, with ferrite magnets in stator slots, machine torque density and efficiency can be improved by 20.2% and 5.1%, respectively.

This paper proposes three novel dual-stator flux-modulated permanent magnet (DSFMPM) machine concepts, which are particularly suitable for direct-drive applications with the virtue of their high torque density and low operation speed. The dual-stator configuration can help improve the use of inner cavity space, and achieve higher torque density comparing with the single-stator counterparts. Moreover, flux modulation is artfully employed to produce the gear effect, which can further benefit for the torque improvement. According to the PM location, the proposed DSFMPM machines are referred as (i) Stator-PM machine, (ii) Stator-rotor-PM machine, and (iii) Rotor-PM machine. Finite element method coupled with genetic algorithm, namely FEM-GA coupled method, is used to optimal design the proposed DSFMPM machines. Their electromagnetic performances are investigated in detail and quantitatively compared. The results show that the dual-stator topology can well improve the torque capability. Among all the proposed DSFMPM machines, the stator-PM one owns the lowest torque density because it has more short-circuit leakage flux.