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This article analyzes the factors causing the precision error of the robot joint module, such as gear meshing disturbance, output elastic deformation, and load mutation. An improved active disturbance rejection control (ADRC) algorithm is proposed to overcome the uncertainty of nonlinear factors and variables of this research topic. The output precision loss of the joint module is introduced as a new input variable of ADRC, combined with the input variable of torque current of the joint module. The extended state observer is redesigned, and the online estimation of disturbance is realized. According to the disturbance estimation results, the current loop algorithm of permanent magnet synchronous motors is improved to compensate the torque disturbance of the robot joint module. The experimental results show that the improved ADRC algorithm can obviously suppress the disturbance of the joint module, weaken the meshing error and torque output deformation of the harmonic reducer gear, and improve the control accuracy of the joint module. [ABSTRACT FROM AUTHOR]

The arc permanent magnet motor (arc motor) is widely used in large telescope for its high efficiency and high power density. Due to the unique structure, the periodic end torque, cogging torque and flux harmonics will cause certain speed ripples which can affect the performance of the drive system. To solve these problems, the paper proposes a novel model predictive control (MPC) based on extended state observer and iterative learning control, where the MPC is equipped in speed loop and the disturbances estimated by the conventional extended state observer (ESO) are fed forward to the controller to improve the ability of disturbance rejection. A position dependent iterative learning control (ILC) is used to estimate the periodic disturbances at different speeds. The MPC calculates the q axis current reference with the compensation of ESO and ILC, which can have a fast response and disturbance rejection ability for periodic and nonperiodic disturbances. The stability of the proposed method is demonstrated by theoretical analysis. The experimental results validate the effectiveness of the proposed method at different speeds. [ABSTRACT FROM AUTHOR]

This article proposes a new hybrid-excited partitioned stator flux modulated machine with a dual-permanent magnet (HE-PSFMDPMM). The HE-PSFMDPMM employs consequent-pole (CP) permanent magnets (PMs) on the inner stator and Halbach array CP PMs on the rotor, which can yield abundant air-gap flux density working harmonics to increase the torque capability. Meanwhile, the field windings are housed in the inner stator to achieve flux weakening. The topology, working principle, and design optimization of HE-PSFMDPMM are investigated, respectively. The electromagnetic performances of HE-PSFMDPMM are analyzed and compared with that of a contrast model with conventional CP PMs on the rotor. The results indicate that by using dual-PM excitation, HE-PSFMDPMM can provide large flux linkage, high torque production with low torque ripple, and high efficiency. Meanwhile, a good flux weakening capability is obtained with the aid of direct current (dc) excitation. Moreover, compared with the contrast model, the proposed HE-PSFMDPMM with Halbach array CP PMs on the rotor can offer the merits of lower cogging torque and torque ripple, higher power factor, and better flux weakening capability. [ABSTRACT FROM AUTHOR]

This article proposes a new partitioned stator hybrid-excited flux reversal machine with dual-PM (PS-HEFRDPMM), in which field windings are placed in the inner stator and permanent magnets (PMs) are employed on both the rotor and outer stator. By utilizing dual-PM excitation, the proposed PS-HEFRDPMM is able to introduce the bidirectional flux modulation effect to transmit high torque production. In addition, a good flux weakening capability can be obtained by using dc current to regulate air-gap magnetic field, which is beneficial to expand the speed range of machine. The machine topology, operating principle, and design considerations of PS-HEFRDPMM are described, respectively. The electromagnetic characteristics of PS-HEFRDPMM under different excitation states are comprehensively analyzed using finite element method. The results show that the proposed PS-HEFRDPMM can provide the merits of high toque capability with low torque ripple, good over-load torque capability, high power factor and efficiency, as well as good flux weakening capability. [ABSTRACT FROM AUTHOR]

In this article, we present a two-step strategy for the torque performance improvement of a dual-stator permanent magnet arc motor (DS-PMAM), which is used in some industrial applications, such as robot joint. The proposed strategy can achieve high average torque, low torque ripple, and, eventually, improve the quality of manufactured products. In the first step, the no-load torque model caused by the end effect is analytically established. In order to suppress the inductance unbalance and the torque ripple, two DS-PMAM models with different winding connection methods are investigated and compared in terms of inductances, backelectromotive force, and torque characteristics. In the second step, a new sensitivity analysis method based on the shapley additive explanations value is first proposed to evaluate the sensitivity of each structural parameter to different optimization objectives. Then, an efficient optimization design method is proposed by combining the machine learning algorithm named eXtreme gradient boosting (XGBoost) and the intelligent optimization algorithm called nondominated sorting genetic algorithm-II (NSGA-II). The XGBoost is innovatively introduced to efficiently approximate the function relationship between the optimization objectives and the structural parameters. The NSGA-II is adopted to determine the optimal combination of the structural parameters and motor performances. Finally, based on the optimal results obtained by the two-step strategy, a prototype of DS-PMAM is manufactured and tested to validate the proposed strategy. [ABSTRACT FROM AUTHOR]

Arc permanent magnet (PM) motors show good prospects in large telescope application. To explore an appropriate arc PM motor (APMM) used in the large telescope drive, this article investigates a variable flux APMM (VFAPMM) with dual-PM excitation (DPM-VFAPMM). The DPM-VFAPMM incorporates the merits of the APMM, the hybrid excited motor, and the DPM excited motor. The motor structure and working principle of the DPM-VFAPMM are described. Then, a special winding cross-connection method is adopted to mitigate the torque ripple caused by the end effect. Finally, the electromagnetic performances of the DPM-VFAPMM, the rotor-PM VFAPMM, the stator-PM VFAPMM, and the surface-mounted-PM VFAPMM are investigated and compared. The comparison results show that compared with the other three motors, the DPM-VFAPMM shows the highest flux linkage, the highest back electromotive force, the highest average torque, the highest efficiency, and the second lowest torque ripple. Simultaneously, the DPM-VFAPMM shows high torque/effective PM usage. The advantages of high average torque and low torque ripple show that the DPM-VFAPMM is suitable for the potential application of the large telescope drive. [ABSTRACT FROM AUTHOR]

This article proposes a new dual-stator consequent-pole (CP) flux reversal machine with triple-PM excitation (T-DSCPFRPMM), in which the two stators and rotor are all incorporated with CP permanent magnet (PM) arrangement. The employment of triple-PM excitation is beneficial to enhance the flux densities in the inner and outer air gaps. In addition, the ferromagnetic poles of rotor and stators are, respectively, used to modulate the magnetic field excited by stator-PM and rotor-PM, which introduces the bidirectional flux modulation effect into the proposed machine to enhance the torque production. The topology, operation principle, and design consideration of the proposed T-DSCPFRPMM are analyzed, respectively. The electromagnetic performances of the proposed machine under stator-PM excitation only, rotor-PM excitation only, and triple-PM excitation are evaluated and compared by finite-element analysis. The predicted results show that by using triple-PM excitation, the proposed machine can offer the superior torque production with low torque ripple, excellent overload torque capability, high efficiency and high-power factor, which are desirable for direct-drive applications. [ABSTRACT FROM AUTHOR]

This study proposes an improved power density permanent magnet synchronous motor (PMSM) for more electric aircraft (MEA) and conducts a design study on aerospace motors. To improve the power density of PMSM, a dual permanent magnet structure using high‐temperature resistant high‐performance permanent magnets and high‐performance soft magnetic alloy material is creatively designed. Methods of lightweight structure designed in both stator and rotor meanwhile are combined as another mean to increase power density. The optimisation models for 6‐slot/8‐pole and 12‐slot/10‐pole configurations are first established based on finite element analysis. Methods of improving the power density of PMSM are then given, including minimum core back yoke thickness and lightweight structure design. The electromagnetic characteristics of the optimised machine are analysed by finite element analysis software, including back electromotive force (back‐EMF), inductance, and power loss. The configuration of 12‐slot/10‐pole is selected as the best design scheme for MEA, based on which a prototype is manufactured and tested. The experiment results of cogging torque and line back‐EMF are in good agreement with the simulation results, which shows the rationality of the designed new machine. The design proves to be effective for improving the power density of aerospace motors. [ABSTRACT FROM AUTHOR]

This article proposes a general design method for dual-stator field modulation machines (DSFMMs) that can be separated into two field modulation machine (FMM) portions sharing the key components with each other. The existing permanent-magnet synchronous machines and FMMs can be categorized into R/S types, where R denotes the part that can generate the rotating magnetic field, and S represents the stationary modulator. R and S can be used to derive various DSFMM topologies that take advantage of the high toque density. The combined machines employ the multilayer topology that provides space for multi-PM-excitation and multimodulation. The general design principle, simplest R/S-type machine, and the coupled armature winding configuration are discussed, and the modulated air-gap working harmonic components are investigated. Four representative dual-stator machines are developed based on the proposed method. The proposed hybrid-magnet DSFMM (HM-DSFMM) has the merits of high power factor, low cogging torque, and low torque ripple. The prototype of the HM-DSFMM is manufactured and tested. The result comparisons of the finite-element-analysis prediction and measurement verify the electromagnetic design. [ABSTRACT FROM AUTHOR]

This paper proposes a new hybrid-excited (HE) flux reversal arc permanent magnet (PM) machine (PS-HE-FRAPMM) having partitioned stators which could be applied on large telescope application. The proposed PS-HE-FRAPMM combines the arc PM machine, the stator-PM machine, and the HE machine, which incorporates the merits of high torque, low cogging torque, and wide flux adjustment capability. The machine topology, operation principle, and rotor mechanical analysis of the proposed PS-HE-FRAPMM are first addressed. Then, the different slot-rotor pole combinations are comprehensively investigated. Moreover, the main structural parameters of the proposed machine are optimized for maximizing the torque and minimizing the torque ripple. Finally, the electromagnetic performances of both the proposed PS-HE-FRAPMM and single-stator HE-FRAPMM (SS-HE-FRAPMM) are comprehensively evaluated and compared. The comparison results show that compared with the SS-HE-FRAPMM, the proposed PS-HE-FRAPMM exhibits higher torque capability, lower torque ripple, and relatively wider flux adjustment capability. [ABSTRACT FROM AUTHOR]

This paper proposes a new double-sided (DS) flux reversal arc permanent magnet (PM) machine (DS-FRAPMM), which could be applied on large-diameter telescope drive. The proposed DS-FRAPMM incorporates the merits of the APMM, the stator-PM machine, and the DS machine. The machine topology and operation principle of the DS-FRAPMM are first proposed. Then, different slot/rotor pole combinations and main structural parameters of the proposed machine are investigated and optimized for maximizing the torque and minimizing the torque ripple based on the response surface method. Finally, finite-element analysis (FEA) is used to comprehensively analyze and compare the electromagnetic performance of the proposed DS-FRAPMM, single-sided FRAPMM (SS-FRAPMM), DS surface-mounted PMs APMM (DS-SPMAPMM), and DS flux-switching APMM (DS-FSAPMM). Compared with DS-SPMAPMM, DS-FRAPMM has lower PM usage and higher torque in per unit PM usage, while compared with SS-FRAPMM, DS-FRAPMM shows higher flux linkage and higher output torque. In addition, compared with DS-FSAPMM, DS-FRAPMM has a lower torque ripple with a slightly lower output torque, which is suitable for large telescope drive. [ABSTRACT FROM AUTHOR]

This paper proposes an adjustable-speed permanent magnet eddy-current coupling with a non-rotary mechanical flux adjuster (MFA) to regulate the speeds of large pump and fan for energy saving. The slip speed of the proposed coupling can be adjusted by shifting MFA along the axial direction. The structural feature and operation principle of the coupling are illustrated and addressed. A magnetic equivalent circuit model is established for analyzing the electromagnetic characteristics of the coupling efficiently. The air-gap magnetic fields, eddy-current densities, and torque–slip characteristics are investigated under different shifting distances of MFA, which reveals the fairly good torque regulation effects. The torque regulation range reaches to about 90% of the maximum torque, which indicates that the coupling can achieve a large speed regulation range by using the relatively simple approach. [ABSTRACT FROM AUTHOR]

A memory machine (MM) equipped with hybrid permanent magnets (PMs), i.e., NdFeB and low coercive force PMs, exhibits acceptable torque capability at low speeds and high efficiency at high speeds. Previous literatures have addressed that the constant power speed range (CPSR) of MMs can be further extended by online PM flux control and the requirement of the flux-weakening (FW) inverter current can be reduced as well. Nevertheless, how to coordinate the d-axis vector FW and PM magnetization control over a whole operating range in a reasonable manner remains unreported. Therefore, this paper proposes and implements a stepwise magnetization control strategy on a dc-magnetized MM based on the operating characteristics under various PM magnetization states and speed ranges. The configuration, principle, and mathematical model of the investigated machine are introduced first. Then, the proposed control strategy is established by dividing the operating envelop into several FW regions and an appropriate FW control scheme is utilized at each stage. It demonstrates that the CPSR can be effectively extended by simply applying the demagnetizing current pulses in several steps. This simplifies the control efforts considerably without resorting to continuous PM flux control and frequent actions of the switching devices. The effectiveness of the proposed control strategy is verified by experimental results. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous motors (PMSMs) are increasingly used in the field of aerospace due to their high efficiency and high power density. High electromagnetic load and lightweight structure have been employed in motor design to improve power density. However, the saturation performance of iron-core material limits the application of high magnetic load in motors and lightweight structure is only used in rotor design. In this paper, four models are used to investigate that lightweight structure applied in stator and high-performance soft magnetic alloy core adoption can improve the power density of PMSM. The electromagnetic performances of four models are compared to verify that the proposed method can effectively improve the power density of PMSMs. [ABSTRACT FROM AUTHOR]

This paper proposes a new hybrid magnet (HM) dual-stator vernier machine (DSVM) with flux-reversal (FR) magnet arrangement, in which NdFeB and ferrite magnets are reversely mounted on tooth tips of outer and inner stators, respectively. The hybrid dual excitation topology enhances the magnetic fields of inner and outer air-gaps, which are modulated by the rotor composed of iron poles. The proposed topology, operating principle, and design consideration are described. The merits of the proposed HM-FRDSVM are verified when compared to the same FRDSVMs with dual NdFeB magnet excitation and with dual ferrite magnet excitation and the conventional dual stator synchronous permanent magnet machine. The two-dimensional finite element analysis results show that the proposed machine has high torque cost performance with low torque ripple and low cogging torque that are desirable for large telescope drive application. [ABSTRACT FROM AUTHOR]

This paper proposes high-torque-density dual-stator permanent magnet machines with biased permanent magnet (PM) excitation in the inner stator. The developed machine can be geometrically considered as an outer-rotor stator PM machine plus a separate outer stator similar to the conventional fractional-slot machines. Consequently, the proposed designs feature two different stator structures. Meanwhile, two sets of armature windings are employed to improve the space utilization ratio and torque density. The machine topologies and operating principles are first described. In addition, the analytical models of the machine are introduced, which are utilized to optimize the stator/rotor pole combination as well as the power splitting ratio between two stators. This design optimization is performed in order to maximize the torque capability with the constraint of copper loss. The electromagnetic characteristics of the proposed machine with different inner stator structures are evaluated and compared by the finite-element (FE) method. Finally, an optimized dual-stator biased PM machines prototype is manufactured and tested to verify the FE analyses. [ABSTRACT FROM AUTHOR]

In this paper, novel dual-stator switched-flux hybrid magnet machines (DS-SF-HMMMs) are proposed. Two sets of armature winding are employed so as to improve the space utilization and torque density. Meanwhile, two kinds of permanent magnets (PMs), i.e., neodymium–iron–boron and low-coercive-force magnets, are placed on either a common stator or separate stators. The proposed machines can provide the merits of high torque density in DS machines, and excellent flux adjusting capability in memory machines. The topologies and operating principle of the DS-SF-HMMMs having different PM arrangements are introduced and highlighted, respectively. In order to overcome the drawbacks of the original “U”-shaped PM type, two alternate designs are presented to increase the copper area in the inner stator and facilitate the manufacturability. In addition, the equivalent magnetic circuits for various machine models are formulated to reveal the field regulation principle. Then, the electromagnetic characteristics of various available DS-SF-HMMMs are evaluated and compared by the finite-element (FE) method. The stator/rotor pole combinations of the selected machine are analytically optimized in order to maximize the torque density. Finally, two prototypes are manufactured and tested to verify the FE analyses. [ABSTRACT FROM PUBLISHER]

This paper proposes two novel partitioned stator (PS) memory machines based on flux-reversal and switched-flux topologies, respectively. The proposed machines geometrically feature two separate stators with armature winding and hybrid PM excitations, i.e., NdFeB and low coercive force PMs. The proposed PS machines can offer increased available inner stator space for hybrid PM, which is beneficial to the torque improvement. The machine topologies are introduced first in terms of possible PM types with parallel magnetic circuits. The design considerations for hybrid PM are analytically analyzed. Then, the electromagnetic characteristics of the two proposed machines are comprehensively compared by using finite element (FE) method. The commercially available Toyota Prius 2010 machine is referenced as a benchmark for comparison with the optimal PS machine having identical overall dimension in potential context of traction applications. Finally, The FE analyses are validated by experiments on a small-scaled demonstration machine. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel consequent-pole hybrid excited vernier machine (CPHEVM) by combining hybrid excited concept and vernier structure, and the consequent-pole magnet arrangement is employed on outer rotor. The proposed machine can achieve high torque density at low speed and excellent flux-weakening capability at high speed, which are highly desirable for electric vehicle applications. The direct current field windings are embedded between modulating poles, which increase the space utilization ratio to enable flux regulation without decreasing torque capability. The configuration, operation principle, and design consideration of the proposed CPHEVM are described, respectively. Finite-element method is employed to analyze the electromagnetic performance of the selected CPHEVMs with various slot/pole combinations, including flux regulation capability, back-electromagnetic force, and torque characteristics with and without flux-weakening control. [ABSTRACT FROM AUTHOR]

The on-load magnetization characteristics of a newly developed partitioned stator switched flux hybrid magnet memory machine are comprehensively analyzed in this paper. First, the open-circuit and on-load permanent magnet magnetization performances are evaluated and compared. The mismatch of the required demagnetizing currents between open-circuit and on-load cases is identified. Then, the on-load demagnetization behavior of low coercive force (LCF) magnet is disclosed by the frozen permeability method. Besides, a numerical solution for the refinement of LCF magnet sizing is presented by a proposed virtual linear hysteresis model so as to effectively prevent the undesired on-load demagnetization. Finally, an optimized prototype is tested to verify the theoretical analyses. [ABSTRACT FROM AUTHOR]

This paper develops a design methodology for switched flux (SF) hybrid permanent magnet memory machines (HPMMMs). The memorable flux is achieved due to the variable magnetization level of low coercive force (LCF) permanent magnets (PMs) Thus, the associated excitation loss is negligible, resulting in high efficiency operation over a wide speed range. A general hybrid PM magnetic circuit is modeled, which is characterized by spoke-array NdFeB PMs and LCF PMs sandwiched between an outer stator ring and an inner stator pole. Based on the magnetic circuit, the design conflicts within the stationary side are unveiled. Thereafter, the machine configuration is introduced, followed by a description of the design procedure. First, the optimal stator pole number is determined based on one-phase machine models. In addition, a simplified permeance function is utilized to analytically optimize the rotor number, accounting for different ratios of the slot opening to NdFeB PM thickness. The electromagnetic performance of the machines with alternate stator/rotor pole combinations are compared. The design guidelines for LCF PMs are presented. Finally, the theoretical analysis is verified experimentally on the prototype machine. [ABSTRACT FROM AUTHOR]

This paper proposes two high-performance switched flux hybrid magnet memory machines (SF-HMMMs) based on the design concepts of E-core and C-core SF permanent magnet (PM) machine topologies. Since two kinds of PMs (i.e., NdFeB and low coercive force magnets) are employed, the proposed machines can offer the merits of high torque capability, excellent flux adjustability, and high efficiency across a wide speed range. In this paper, the PM arrangement and dimensions, stator/rotor pole number combination, as well as the major design parameters are optimized first. Then, the electromagnetic characteristics of the proposed machines are investigated and compared with their conventional 12-stator pole SF-HMMM. It is found that compared with their conventional 12-stator pole counterpart, the proposed machines offer improved torque density and flux adjustability, even with the reduced PM usage. Finally, two machine prototypes are manufactured and tested to validate the analyses. [ABSTRACT FROM PUBLISHER]

This paper presents a partitioned stator switched flux memory machine (PS-SFMM) with triple magnets to enable expedient flux control with reduced converter power rating. Meanwhile, the torque/magnet cost ratio of the machine has been significantly improved without much compromise of the torque capability. Three kinds of permanent magnets (PMs), NdFeB, SmCo, and AlNiCo, are hybridized, and hence the irreversible demagnetization of vulnerable AlNiCo PMs can be well prevented by SmCo magnets. The machine configurations with dual PM (DPM) and triple PM (TPM) are described first. Thereafter, the performance improvement mechanism is unveiled and addressed in the perspective of hysteresis curves as well as simplified magnetic circuits. In addition, the electromagnetic characteristics of the proposed machine with triple-magnet design are investigated and compared with those having DPMs. Finally, two PS-SFMM prototypes with DPM and TPM are manufactured and tested to verify the theoretical analyses. [ABSTRACT FROM PUBLISHER]

A generic analytical frame for evaluating the torque performance of eddy current coupling equipped with a quasi-Halbach permanent magnet (PM) array is given, where the motional eddy current problem is represented by a four-layer boundary value problem. The effective magnetic characteristics and the field equation associated with the quasi-Halbach array are described in detail. To effectively predict the actual electromagnetic force at any slip speed, the eddy current distributions in the low-speed and high-speed cases are, respectively, investigated, and a modified 3-D correction factor is subsequently developed. A verification process is implemented by a 3-D finite-element analysis using the fixed computational grid method. The effects of the thickness of PM back iron on the degree of saturation and then on the variation of torque are investigated, and the impact of the eddy currents induced in the conductor back iron on the overall torque in the whole slip-speed range is also assessed. [ABSTRACT FROM AUTHOR]

The memory machine concept is recently extended to switched-flux (SF) machines, forming a series of SF hybrid magnet memory machines (SF-HMMMs). They exhibit the merits of good demagnetization withstand capability and effective flux adjustability. Nevertheless, the torque density is inevitably compromised due to the geometric conflict within the stationary part. Meanwhile, the inactivated dc coil, excluding online magnetization transients, results in system redundancy. Hence, in this paper, a new hybrid-excited (HE) concept is developed and implemented in a partitioned-stator SF-HPMM (PS-SF-HMMM). Thereby, the distinct synergies of a dual-magnet memory machine and an HE machine are achieved. With slight compensated field excitation, the torque can be improved at low-speed operation. Meanwhile, the high-speed constant-power region can be further extended without sacrificing high efficiency. The stator/rotor pole numbers are optimized first. The operating mechanism and optimal stepwise HE implementation over a whole operating envelop are then addressed. In addition, a comparison between PS-SF-HMMM with hybrid-excitation and its pure HE counterpart is established. Finally, both the finite-element simulation and experiments are carried out to verify the utility of the proposed HE concept. [ABSTRACT FROM AUTHOR]

In this paper, a novel topology of hybrid-permanent-magnet switched-flux memory machine (HPM-SFMM) is proposed, which is characterized by a conventional SFPM machine with embedded “V”-shaped Al-Ni-Co magnet poles. The proposed machine combines the distinct synergies of torque enhancement in neodymium–iron–boron (NdFeB) PM and flux variability in aluminum–nickel–cobalt (AlNiCo) PM. By changing the magnetization directions of Al–Ni–Co magnets, the wide-speed-range high-efficiency operation can be readily achieved, which is highly favorable for automotive applications. The configuration and operating principle of the machine are first described, and the combination of stator/rotor pole numbers is optimized. In addition, the torque density/flux adjusting capability as the functions of dual-magnet dimensions are analytically derived. The magnet hybridizing proportion is optimized in order to achieve a favorite tradeoff between flux adjusting range and torque density improvement. Then, the electromagnetic performance of the proposed HPM-SFMM is investigated. Finally, a 12/14-stator/rotor pole prototype is fabricated to experimentally verify the analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a novel linear–rotary permanent-magnet actuator (LRPMA) with interlaced poles, which has the merit of using only 50% of the neodymium–iron–boron permanent magnets when compared with those used in traditional Halbach structure. By assuming the stator is slotless, the magnetic field distribution of the LRPMA is initially analyzed using the magnetic scalar potential in the Cartesian coordinate system. A method for calculating the relative permeance by Schwarz–Christoffel transformation (SCT) is subsequently deduced to analyze the magnetic field in detail and predict the cogging force/torque of LRPMA very accurately. The analytical linear cogging force and rotary cogging torque are derived and verified for the design optimization of the actuator. The 3-D finite-element method is used to verify the correctness and effectiveness of the proposed SCT. [ABSTRACT FROM AUTHOR]

This paper deals with a sizing optimization approach to reducing the cogging torque and maximizing the flux linkage of a transverse flux permanent magnet generator with double C-hoop stator and flux-concentrated rotor. The previous investigations demonstrated that the cogging torque is significantly influenced by ks and kr , which denote the ratios of circumferential widths of stator hoop and rotor core to pole pitch, respectively. The 3-D finite-element method (FEM) is employed to investigate the relationship between the abovementioned ratios and the cogging torques of both single-phase and three-phase prototypes. The optimal ratios of ks and kr , which comply with the equation, i.e., $(k_{{ r}} >1-k_{{ s}} )\cap (k_{{ r}} >1-0.788~*~k_{{ s}} )=k_{r} >1-0.788~*~ k_{{ s}} $ , are selected, and the procedures are described. The FEM results show that the amplitude of the cogging torque can be reduced significantly due to the reshaped rotor core. Besides, two additional zero-crossing points can be observed with the increase in kr and the decrease in ks . The cogging torque can be decreased by 20% with a skewed rotor core. A three-phase prototype is optimally designed and manufactured to verify the optimization approach. [ABSTRACT FROM AUTHOR]

Transverse flux permanent magnet (TFPM) machine possesses the characteristic feature of decoupled electric load and magnetic load to obtain high power density. A novel TFPM generator (TFPMG) with double C-hoop stator and flux-concentrated rotor is proposed for low-speed applications, such as direct-drive power generation, which has larger torque capability and more poles than traditional double-side TFPMGs. The structure and operation principles of the generator are described in detail. The 3-D finite-element method (3-D FEM) is employed to compute the no-load magnetic field distributions. The analytical results, including flux density waveform, electromotive force (EMF) waveform, and inductance waveform of the armature winding, are obtained to verify the principle and feasibility of the proposed generator. The cogging torque is also analyzed and optimized by the 3-D FEM. A prototype is fabricated, and some experiments are conducted. The experimental results of back EMF and waveforms of current and voltage with different loads verify the FEM analysis previews well. [ABSTRACT FROM AUTHOR]

This paper presents a quantitative comparative study on the two novel memory machines (MMs) with two sets of different magnets on the stator, which are derived from the switched flux (SF) and the variable reluctance (VR) topologies, respectively. The machine topologies, the operating principles, and the design considerations are described. The hybrid magnet sizing is analytically optimized with the aid from a simplified magnetic circuit. Then, the major parametric optimization is conducted on the two machines sharing identical outer diameter and stack length, as well as the copper loss constraint. The electromagnetic performance of the two optimally designed models is analyzed and comprehensively compared, which confirms the advantage of the SF topology for MMs. [ABSTRACT FROM AUTHOR]

This paper presents a 3-D analytical magnetic field analysis of an air-cored axial-flux Halbach permanent-magnet machine (AFPMM with Halbach). The 3-D analytical magnetic distribution is established using the magnetic scalar potential and modified BESSEL functions in the cylindrical coordinate system. The analytical magnetic field distributions and the electromagnetic force are derived and verified by the computation results using the finite-element method. [ABSTRACT FROM AUTHOR]

In this paper, a consequent magnet pole switched flux memory machine (CMP-SFMM) is developed to improve the torque density and simplify the mechanical manufacturing with less magnet usage compared with its hybrid magnet counterparts. Nevertheless, owing to the significant magnetic saturation, the flux-adjustable range appears to be relatively limited, which will deteriorate the flux-weakening performance. Therefore, a novel winding-switching concept is introduced to deal with its limited flux-weakening capability, i.e., the magnetizing coils will alternatively serve as the secondary armature winding after the reversal of magnetization directions of low-coercive force magnets, thus resulting in the flux-linkage cancellation within the same phase. The machine topology, flux-weakening principle, and integrated circuit design are addressed. Then, the electromagnetic characteristics of CMP-SFMM with or without winding-switching are investigated and compared, which confirms the feasibility of the flux-weakening method. [ABSTRACT FROM AUTHOR]

A combined analytical and FEM technique is proposed for predicting the air-gap magnetic field distribution of a PM embedded salient pole wind generator. The influence of slotting on both radial and circumferential components of air-gap flux density is taken into account. By employing the proposed combination technique, the magnetic field distributions when the stator and rotor are at different relative positions can be calculated much faster than that by FEM. Based on the magnetic field distributions, the cogging torques are predicted and verified by the FEM, while the relationship between cogging torque and design parameters are further investigated. The proposed combination technique provides an efficient and accurate prediction method for the air-gap magnetic field distribution of large electrical machines with a complex PM pole structure. [ABSTRACT FROM AUTHOR]

This paper presents a 3-D analytical study of the linear electromagnetic force and rotary electromagnetic torque of a novel linear and rotary permanent magnet actuator (LRPMA). The 3-D analytical magnetic distribution of the LRPMA is established using the magnetic scalar potential and modified BESSEL functions in the cylindrical coordinate system. Linear electromagnetic force and rotary electromagnetic torque, respectively, are derived and verified using finite element method (FEM) for the characterization and optimization design of the LRPMA being examined by experiments in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a study on decoupling control of a linear and rotary permanent magnet actuator (LRPMA) with linear, rotary and helical movements. Since both linear and rotary motions of the actuator are dependent on both current and voltage, a novel two-directional d\-q transformation is proposed to decouple the inter-relationship between the current and voltage in each coil. The expressions of input power, magnetic field energy, rotary torque, linear force and copper loss are all derived. A MATLAB/Simulink model for helical movement is then setup with hysteresis current control. A practical LRPMA prototype is manufactured and its control system is implemented with a dual digital signal processor. Simulations and experimental measures on the LRPMA prototype are reported to showcase the effectiveness of the control strategy. [ABSTRACT FROM PUBLISHER]

This paper presents a method for analytically analyzing the magnetic field and predicting the cogging force and torque of a linear and rotary permanent magnet actuator (LRPMA). The tubular mover of the LRPMA is transferred into a planar one by using a proposed magnetic field curvature factor and a relative permeance function for the stator slotting so as to simplify the magnetic field calculation. Magnetic field distributions of the LRPMA when the stator slotting is neglected are analytically analyzed using the magnetic scalar potential, and validated by 3-D finite-element method. The linear cogging force and rotary cogging torque of slotted LRPMA are subsequently predicted by the Maxwell stress tensor method and verified by the experimental results on the prototype. [ABSTRACT FROM AUTHOR]

This paper proposes a novel magnet-axis-shifted hybrid permanent magnet (MAS-HPM) machine, which features an asymmetrical magnet arrangement, i.e., low-cost ferrite and high-performance NdFeB magnets, are placed in the two sides of a "▽"-shaped rotor pole. The proposed magnet-axis-shift (MAS) effect can effectively reduce the difference between the optimum current angles for maximizing permanent magnet (PM) and reluctance torques, and hence the torque capability of the machine can be further improved. The topology and operating principle of the proposed MAS-HPM machine are introduced and are compared with the BMW i3 interior permanent magnet (IPM) machine as a benchmark. The electromagnetic characteristics of the two machines are investigated and compared by finite element analysis (FEA), which confirms the effectiveness of the proposed MAS design concept for torque improvement. [ABSTRACT FROM AUTHOR]

This paper proposes the use of a novel cylindrical arc permanent magnet synchronous motor (CAPMSM) in a large telescope, which requires high positioning accuracy and low torque ripple. A 2D finite element method was used to analyze the cogging torque of the CAPMSM. The CAPMSM can be an alternative for a rotating motor to realize direct drive. A new method is proposed to separate the cogging torque, Tcog, into the torque, Tslot, generated by the slotted effect and the end torque, Tend, generated by the end effect. The average torque and the torque ripple are optimized considering stator center angle, the angle between two adjacent stators and the unequal thickness of a Halbach permanent magnet. The torque ripple decreased from 31.73% to 1.17%, which can satisfy the requirement of tracking accuracy for large telescopes. [ABSTRACT FROM AUTHOR]