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Variable-flux memory machines (VFMMs) are considered as promising candidate in adjustable speed drive applications. However, the exploration of VFMMs with acceptable magnetization state (MS) regulating current and high-torque density is still a challenging issue. This article presents a high-torque-density VFMM which is comparable with conventional permanent-magnet machines. The newly developed (Ce, Nd)-Fe-B magnet with remarkable characteristics is employed in the investigated VFMM. The characteristics of the (Ce, Nd)-Fe-B magnet are firstly introduced. Second, a simple and superior VFMM topology with (Ce, Nd)-Fe-B magnet is evaluated in terms of torque production capability, MS regulation characteristics, and overall efficiency and compared with the benchmark machine.

The development of traditional permanent magnet synchronous machines (PMSMs) in electric vehicle (EV) industry is limited by the unalterable permanent magnet (PM) excitation field. Variable-flux PMSMs are considered as a good candidate for EV propulsion for their ability to operate in a wide speed range with high efficiency by manipulating the magnetization state dynamically. A novel hybrid-PM variable-flux PMSM with series–parallel magnetic circuits is proposed in this article. The structure and operating principle of the proposed machine are introduced. The electromagnetic performances of the proposed machine are analyzed and compared with the series-connected and parallel-connected variable-flux machines, and the proposed machine combines the advantages of these two kinds of machines. The inductance characteristics of the proposed machine are analyzed by frozen permeability method (FPM), and the variation laws of inductance are quite different in different magnetization states and load conditions. The torque capacity of the proposed machine is analyzed. The torque ripple can be significantly reduced and the output torque can be improved by properly applying flux-weakening control.

In order to satisfy with the demand of high reliability in the aerospace field, a unified control scheme is proposed for five-phase open-winding permanent-magnet synchronous generator (FPOWPMSG) in this paper. Firstly, the mathematical model of FPOWPMSG in the phase coordinate system is established. Then, the proposed unified control scheme is presented in detail, which is mainly composed of the unified reference current generator, the current regulator, the synchronous electromotive force (EMF) compensator, and the piecewise nonlinear predictive compensator. In the unified reference current generator, normal operation, single-phase open-circuit, adjacent two-phase open-circuit, and non-adjacent two-phase open-circuit are taken into account by introducing a fault matrix. In the current regulator, the PI regulator is used. And the current tracking accuracy and the torque ripple are improved by both the synchronous EMF compensator and the piecewise nonlinear predictive compensator. Finally, the effectiveness of the proposed unified control scheme is validated by experimental results.

Variable-flux permanent-magnet synchronous machines have gained a lot of attention for their ability to expand the speed range and reduce loss over an electric vehicle drive circle by manipulating magnetization state (MS) dynamically. In this paper, a combined-magnet-pole variable-flux machine (CMP-VFM) using both AlNiCo and NdFeB is analyzed. To obtain the variation laws of MS quickly and precisely, a 3-D neural-network hysteresis model of AlNiCo is proposed, and the accuracy and time consumption of the proposed neural-network hysteresis model are evaluated. In order to optimally utilize the speed expansion and loss minimization capability with precise MS control, a flux observer based on model reference adaptive theory is proposed for the closed-loop flux control of CMP-VFM and validated by simulations. The simulation results prove that the accuracy of the proposed adaptive flux observer is almost not affected by parameter disturbance.

Electric vehicle (EV) is a promising technology for saving fossil energy and reducing pollution. Hybrid-permanent-magnet (PM) variable-flux machine is a competitive candidate for EV propulsion since it has wide speed range and high efficiency at high-speed region. A novel hybrid-PM variable-flux machine with magnetic barriers is proposed in this paper, and a new magnet material CeFeB is used. The structure and operating principle are introduced, and different magnetization states of the machine are analyzed. The equivalent magnetic circuit model of the machine is established considering the influence of magnetic barriers, and the model is proven with good precision for the calculation of air gap flux density and PM operating point. The electromagnetic performances are analyzed, and compared with a traditional variable-flux machine. It is verified that the added magnetic barriers improve the distribution of air gap flux and load magnetization performance of the machine. The no-load back electromotive force, electromagnetic torque, speed range, and load magnetization ratio of the proposed scheme are all improved.

With the advantages of good driving performance, high fuel economy, and low emission, the series-parallel hybrid electric vehicles (HEVs) are widely developed. Power-split device, which is a kernel part of HEV, can be based on planetary gear or compound-structure machine (CSM). A transverse-flux brushless double-rotor machine (TF-BDRM), which can form a CSM by being connected with a traditional permanent-magnet synchronous machine (PMSM), is investigated in this paper. The equivalent magnetic circuits are established, and the equivalent reluctances, and d - and q -axis armature-reaction reactance are deducted. It is found that the armature-reaction reactances are in direct proportion to pole-pair number. The reluctances of stator core, inner, and outer air gaps, transverse-flux (TF) tooth and leakage reluctance are analyzed, and it is found that the improvement of reluctances may affect other performances of the machine. Flux-concentration structure is investigated to increase the main flux of the machine. Flux-concentration factor ξ FC is used to illustrate the effect of flux-concentration structure, which can be increased by the increase of the radial and circumferential thickness of permanent-magnet. The flux-density distributions of two typical situations are simulated, and the flux-density distribution laws in inner and outer air gaps are given. With manufacturing technology investigated, the TF-BDRM prototype is made, and experiments are carried out. The tested waveforms of the back electromotive force are approximately sinusoidal, and the tested torque ripple is obvious

The classical Preisach hysteresis model and its modifications are time consuming to implement due to the determination of the weight function. Another defect of the Preisach-based model is that it could only be an approximation in the absence of the congruency property. For such reasons, this paper proposes a hysteresis model identification method based on support vector regression which could be a promising alternative in practical applications. Support vector machine is attractive in regression analysis due to its strong generalization capability. A four-stage identification procedure is implemented and key techniques are introduced in detail. The penalty parameter and the kernel parameter are optimized using grid search and cross-validation method. The influences of data scaling and parameter optimization are analyzed. An identified hysteresis model of aluminum nickel cobalt alloy is evaluated and verified with the criteria of mean squared error and identified time.

The flux-modulated compound-structure permanent magnet synchronous machine (CS-PMSM), composed of a brushless double rotor machine (DRM) and a conventional permanent magnet synchronous machine (PMSM), is a power split device for plug-in hybrid electric vehicles. In this paper, its operating principle and mathematical model are introduced. A modified current controller with decoupled state feedback is proposed and verified. The system control strategy is simulated in Matlab, and the feasibility of the control system is proven. To improve fuel economy, an energy management strategy based on fuzzy logic controller is proposed and evaluated by the Urban Dynamometer Driving Schedule (UDDS) drive cycle. The results show that the total energy consumption is similar to that of Prius 2012.

The permanent-magnet variable-flux machine (PM-VFM) is a promising candidate in the application of extended-speed operation. In this paper, a V-type hybrid PMVFM which utilizes AlNiCo magnet to enable the magnetization state regulation and the NdFeB magnet to enhance the power density is investigated. The magnetic circuit models (MCMs) of the machine under positive magnetization state and negative magnetization state are developed and solved iteratively. The calculated results of the air-gap flux density, open-circuit leakage flux factor, and the operating points of the AlNiCo magnet and the NdFeB magnet are obtained and compared with the simulated results of finite element analysis (FEA). The selection rules of dimensional parameters of hybrid PMs are investigated. To reduce the negative influence of the q-axis armature magnetic field on the electromagnetic performance of PM-VFMs, the effects of the q-axis flux barrier on the air-gap flux density, flux variation range (FVR) and torque characteristics are investigated. The mechanical strength of the rotor with q-axis flux barrier is verified.

Variable-flux permanent-magnet synchronous machines (VF-PMSMs) have been widely researched for their ability to expand the speed range and reduce loss by manipulating magnetization state (MS) dynamically. The hybrid PM configuration using variable PM (VPM) with low coercive force and constant PM (CPM) with high coercive force, is widely used in VF-PMSMs to improve the torque density. A novel VF-PMSM with parallel hybrid magnets is proposed in this paper. The topology, operating principle and pole/slot combinations of the proposed machine are analyzed. And the electromagnetic performances, including air-gap flux density, back-EMF and torque capability, are evaluated through finite element analysis (FEA). The efficiency improvement of the proposed machine is evaluated. The results prove that the proposed machine is capable of operating in a wide speed range with high performance.

In this paper, a new current sensing method which combined delta-sigma ADC and SINC3 digital filter is proposed to reduce the effect of large resistance and low inductance on current control. An improved FOC control method combined with delta-sigma ADC is used to implement sinusoidal commutation for a micro coreless BLDC motor to reduce torque ripple. The improved FOC control method can guarantee smaller current loop steady-state error. The proposed methods are simulated.

A hybrid-magnetic-pole variable-flux machine (HMP-VFM) is proposed in this paper. The low- and high-coercive-force magnets are utilized in the rotor in V-shape alternately, and each kind of magnets forms a magnetic pole. The proposed machine features the capability of changing the magnetization state of the low coercive-force (LCF) magnetic poles via stator winding. The structure of the machine and operating principle of the LCF magnet are given, and the electromagnetic performance, including magnetic field distribution, no-load air-gap flux density, back electromotive force (EMF) and torque-angle characteristics, in different magnetization states is investigated by finite element method (FEM). Besides, the torque-speed curves and efficiency maps are calculated, and the results show that the HMP-VFM can operate over a wide-speed range with high efficiency.

Variable-flux machine has good application prospect at wide-speed-range field. This paper investigates the electromagnetic performance of a novel hybrid-permanent-magnet (PM) variable-flux machine. The effects of PM thickness, PM ratio and flux barrier on back electromotive force (EMF), electromagnetic torque and magnetization-adjustment ability of the machine are analyzed. The machine is proved with good speed-regulation capability by investigating the efficiency map at different magnetization states.

Variable-flux permanent magnet synchronous machine (VF-PMSM) is a promising candidate for adjustable speed applications, which utilizes low coercivity $(\boldsymbol{H_{c}})$ magnets to enable the flexible magnetic flux regulation. Aiming at providing some useful insight into the usage of low- $\boldsymbol{H_{c}}$ magnets in VF-PMSMs, this paper firstly gives a comparison of different low- $\boldsymbol{H_{c}}$ magnets not only in terms of general properties but also practical application characteristics in VF-PMSMs. Then, an investigation of electromagnetic performance of VF-PMSMs employing different types of low- $\boldsymbol{H_{c}}$ magnets is carried out. Low- $\boldsymbol{H_{c}}$ magnet design considerations for VF-PMSMs based on distinguishing PM characteristics are also given.

Permanent-magnet synchronous machines (PMSMs) with hybrid PMs have attracted much attention. In this paper, a V-shape-pole hybrid-PM interior-PMSM with six-phase fractional-slot concentrated winding (FSCW) is investigated. To improve the effects of the hybrid-PM, Some magnetic barriers are introduced in the V-shape interior-PMSM. Then, the comparison studies of the hybrid-PM V-shape interior-PMSMs with or without the barriers are performed. The effective condition of the improved method is established.

Variable flux machine is a promising candidate in high-speed field. The rotor flux of variable flux machine is an important performance index, and it need to be detected accurately in real time. An adaptive rotor flux observer is investigated in this paper. The mathematical model of the observer is established, and the simulation result verifies the good accuracy and following characteristic of it. The influences of parameter fluctuation on the accuracy of adaptive rotor flux observer are analyzed, and the disturbance compensation is introduced to reduce the error rate of rotor flux. The experiment is carried out, and the adaptive rotor flux observer is proved having good precision.

Aiming at extending the operating speed range and increasing the machine efficiency, three series-configuration hybrid-permanent-magnet variable-flux machines (HPM-VFMs) with both low and high coercive-force magnets are proposed. The magnetization characteristics of the machine with different dimensions of the high coercive-force (HCF) magnet are investigated. Then, in order to improve the contribution rate of the HCF magnet, two improved topologies are presented. The electromagnetic characteristics of the two proposed machines, including back electromotive force (EMF), maximum torque characteristics, magnetization state (MS) variation range and magnetic field distribution, are comprehensively analyzed and compared. The influence of different types of windings on the performance of the machine is also investigated. Finally, the torque-speed curves of the machine under different MSs are given by finite element method (FEM). The results show that the HPM-VFM can operate over a wide-speed range with high efficiency.

A tubular flux-switching permanent-magnet linear machine (PMLM) is proposed and designed for free-piston energy converter. The influences of several main structure parameters on the machine performances are investigated. The power, power density and efficiency are improved by optimizing the structure parameters. Further, characteristic of the detent force is studied and the detent force is reduced by choosing proper combinations of the structure parameters. Finally, with poor heat dissipating condition considered, thermal field distribution of the proposed machine is evaluated by 3D finite element analysis (FEA), which ensures safe operation of the machine.

Stirling power generating system, which has the advantages of multiple energies applicable and high efficiency, is promising for aerospace applications. As the main part of Stirling power generating system, single-phase oscillating permanent-magnet linear machine (PMLM) is investigated in this paper. Firstly, the electromagnetic performances, such as no-load back electromotive force (EMF) and thrust, are analyzed by finite element method. The influences of main parameters, including PM thickness, inner and outer diameter of mover iron core and tooth width, on performance are further investigated to obtain the optimal scheme. The proposed scheme can reach the power density of 0.177kW/kg. To ensure safe operation, the thermal field distribution law of the single-phase oscillating PMLM is investigated.