With the merits of high torque density, unintentional demagnetization (UD) withstand capability and satisfactory flux regulation range, series magnetic circuit variable flux memory machines (VFMMs) have been recently utilized in the new-generation household appliance, e.g., washing machine. However, the conventional series structure leads to the increase of cost and magnetization current amplitude due to a larger volume of permanent magnet (PM) material, which are unfavorable for the industrialization of this kind of machines in domestic appliance applications. In order to address the foregoing issues, a novel consequent-pole hybrid magnet VFMM (CPHM-VFMM) with dual-layer delta-type PMs is proposed and optimized for belt-drive washing machine application in this paper. The machine is geometrically characterized by a novel rotor-PM consequent-pole (CP) design, which replaces half of the magnetic poles with iron parts, thus increasing d -axis magnetic permeance to decrease the corresponding required magneto-motive-force (MMF) for flux regulation while maintaining satisfactory electromagnetic performance. The topology and operating principles of the proposed CPHM-VFMM are firstly introduced and analyzed. The air-gap flux density and flux regulation range of the machine are analytically identified with equivalent magnetic circuit method. Then the machine is optimized with multimode field-current coupled (MMFCC) solution considering the operation situation in the washing machine. Afterwards, the electromagnetic characteristics of the machine are evaluated and compared with those of a conventional VFMM by finite element (FE) method. It shows that the proposed CPHM-VFMM has the merits of smaller PM usage, higher torque density, lower flux regulation current, wider flux regulation range, as well as higher global efficiency compared with the conventional counterpart. A 36-slot/6-pole CPHM-VFMM prototype is manufactured and tested to validate the FE analyses.

Magnetization state (MS) manipulation is crucial to the comprehensive performance improvement of variable flux memory machine (VFMM) drive system. This article proposes a novel MS manipulation control method wherein variable time magnetization current trajectories can be adaptively controlled to reduce the MS manipulation losses. A fuzzy proportional integral (PI) feedforward current controller is newly structured to track the trajectories, improving the current tracking ability. First, dynamic MS manipulation processes are simulated and analyzed deeply, in which the variable machine parameters are calculated by finite element method (FEM) and fitted with polynomial formulas. Based on these, the maximum di _d / dt of magnetization current pulse trajectory, namely the shortest MS manipulation time, can be adaptively acquired to reduce the MS manipulation losses at different running conditions. Then, a fuzzy PI feedforward current controller is developed by combining the feedforward and fuzzy logic controls, ensuring the real current tracks its reference well at different speed and load conditions, particularly in the MS manipulation process. Finally, the effectiveness and feasibility of the proposed MS manipulation method are verified by experimental results on a hybrid-magnetic-circuit VFMM (HMC-VFMM) prototype.

In this article, a novel asymmetric-hybrid-pole variable flux memory machine (AHP-VFMM) is proposed and designed to realize satisfactory unintentional demagnetization (UD) withstand capability and high global efficiency, as well as lower flux regulation (FR) current level. The machine is structurally distinguished by a simple structure of asymmetric high coercive force (HCF) and low coercive force (LCF) permanent magnets (PMs). The main magnetic path of the proposed machine can be changed by manipulating the magnetization state (MS) of LCF PMs, resulting in significantly different field distributions and a large flux regulation range. The proposed AHP-VFMM and symmetric hybrid-pole VFMM (SHP-VFMM) are analyzed based on an equivalent magnetic circuit, and the design criteria of HCF PM in the AHP-VFMM to achieve better magnetic stability is deduced. Sensitive analysis is conducted to identify high- and low-sensitivity parameters of the AHP-VFMM. Then a two-layer optimization is conducted based on multi-objective genetic algorithm. The shape of LCF PM is further modified to improve the UD withstand capability. Afterwards, the AHP-VFMM is compared with an optimized SHP-VFMM with respect to electromagnetic and structural characteristics. Finally, an AHP-VFMM prototype is fabricated and tested to validate the feasibility of the proposed design.

This paper focuses on the electromagnetic-thermal coupled design optimization of a yokeless and segmented armature (YASA) Halbach-array axial flux permanent magnet (AFPM) machine for direct-drive automated guided vehicles (AGVs). According to the application condition, extra high torque density is required with the constraints of natural-cooling and compact size. The machine topology with Halbach-array permanent magnets (PMs) and segmented stator is firstly introduced, and different slot/pole combinations are compared. Then, comprehensive sensitivity analysis is carried out, and the electromagnetic-thermal coupled design optimization consisting of rough and refined processes is carried out based on a newly established thermal network model. Subsequently, the electromagnetic performance of the optimized machine is evaluated and compared with that of an optimized surface-mounted PM YASA (SPM-YASA) benchmark with the same envelop dimension by three-dimensional (3D) finite-element (FE) method. The mechanical structure of the investigated machine with specially-designed heat-transmission mechanism is introduced, and the mechanical strength analysis is carried out. Finally, a machine prototype is manufactured and tested to validate the FE analyses.

In this article, the balanced bidirectional-magnetization effect of a newly developed hybrid-magnet-circuit variable-flux memory machine (HMC-VFMM) is revealed and investigated. First, the machine topology and variable-flux principle of the HMC-VFMM are described. In addition, the balanced bidirectional-magnetization effect is analytically unveiled by using a Fourier-series-based hysteresis model of low coercive force (LCF) magnet. The PM magnetization characteristics are then investigated by a coupled solution, which is employed to identify the mismatch between the LCF magnet movement trajectories subject to either continuous one-way or bidirectional alternate current pulses. Finally, a prototype is manufactured and tested to verify the theoretical analyses.

This paper proposes a multi-objective sequential topology optimization method (MSTOM) for interior permanent magnet (IPM) machines based on normalized Gaussian network (NGnet). Its methodology is mainly composed of global topology coarse optimization, design region reduction, local topology fine optimization and postprocessing successively. This method can alleviate the computation burden and promote the optimization efficiency. For machine topology structure quality, a postprocessing method called NGnet-oriented topology optimization mending postprocessing (NTOMP) is further introduced to guarantee a complete, connected and smooth optimized topology. Furthermore, the foregoing methods have been illustrated by a typical topology optimization example with an IPM machine. Finally, the feasibility, reliability and effectiveness of MSTOM have been confirmed by the optimization results of this machine case study, which is portable to other similar topology optimization scenarios.