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In this article, a new type of electric machine called limited-angle vibration motor (LAVM) for the motion of high-frequency reciprocating rotation is proposed. The corresponding coupled model, resonance principle, and design guidelines are established. Contrary to the conventional limited-angle motors, the LAVM mainly utilizes cogging torque within a limited angle and, thus, can be restored as an electromagnetic spring. By proposing the linear torque models, an analytical model coupling the output torque with the mechanical load is derived, which explains the resonance phenomenon occurring in LAVMs, finding that the maximum vibration amplitude and efficiency can be achieved at resonance frequency, and being verified by the field-circuit-coupled finite-element simulation. Guided by analytical results from resonance principles, a design method, supporting matching the motor with target reciprocating frequency and amplitude by designing the key geometry parameters referring to restoring coefficient and electromagnetic torque coefficient aided by finite-element analysis results, is proposed. Furthermore, an improved concurrent design method is presented focusing on the application of LAVMs in the flapping-wing microair vehicle (FWMAV). Finally, validations are conducted through experiments on three prototypes fabricated according to the design principles, and the application feasibility in FWMAV is also provided.

This article presents a new machine topology configuration of a self-aligning limited-angle vibration torque permanent magnet (PM) machine (LAVM). This kind of machine has a simple structure including 4 pieces of PMs and 2 stator teeth. It can operate in a reciprocating rotation at a high frequency and generate high-frequency vibration torque. Unlike conventional limited-angle torque motors, the LAVM is naturally equipped with auto zero-returning (ZR) performance for its rotor can return to the initial position automatically when no current is applied. The LAVM also shows a resonance phenomenon for the vibration amplitude reaches the maximum in a certain excitation frequency. The operation principles and optimization of LAVM are analyzed through finite element analysis (FEA). To increase the zero-position torque and improve the auto ZR capacity, a sensitivity analysis is conducted first, and then the parameters of this machine are optimized in the aspects of applied current value, PM geometric, PM-pole angle, and overlap coefficient using the parametric sweep method. The analysis results can serve as the design guidelines of LAVM. Finally, the prototype machine is manufactured and tested to validate the theoretical analyses.

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.

This article proposes an improved maximum torque per ampere (MTPA) control method for variable-flux memory machine (VFMM) with operating envelop prediction-based magnetization state (MS) manipulation. The proposed method can achieve the MTPA control under the voltage limitation and simplify the MS adjustment process for expanding the operating region. The mathematical model of the studied VFMM is established to calculate the reference current for MTPA control online as well as to predict the operating envelop at each MS. According to the calculated operating envelop, the proposed MS manipulation method can separate the magnetization and demagnetization processes by setting two MS manipulation boundaries correspondingly, which is easily implementable and can avoid frequent MS manipulation processes. Besides, the inductance characteristics of the machine are measured to improve the model accuracy and control performance. Experiments are carried out on a VFMM prototype to validate the feasibility and effectiveness of the proposed method.

To achieve flexible flux regulation, variable flux memory machines (VFMMs) are normally characterized by a high permanent magnet (PM) flux linkage design, which generally reduces the saliency ratio of the machine. In order to further reveal the internal performance tradeoffs, this paper investigates the relationship between the saliency ratio and PM flux linkages of VFMMs by combining the equivalent magnetic circuit models and the finite element (FE) method. Three hybrid-magnetic-circuit (HMC) VFMMs having different PM grades and saliency ratios are chosen as the case studies to analyze and reveal the influence of flux linkages and saliency ratios on the major electromagnetic characteristics. First, the no-load and dq-axes equivalent magnetic circuit models of the investigated machines are established successively to obtain the PM flux linkages and dq-axes inductances of the machines. Then, the relationships between the electromagnetic torque and the key design parameters are obtained based on the space vector model. Next, the maximum torque per ampere (MTPA) trajectory is portrayed to determine the flux-weakening characteristics of the VFMMs. Afterwards, the electromagnetic characteristics of the three machines are compared and analyzed to confirm the previous theoretical analyses. Finally, an HMC-VFMM prototype is fabricated and tested to verify the effectiveness of the analysis.