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By measuring the open-circuit radial stray magnetic flux density (RSMFD) of three spatial points, a novel diagnostic method for the eccentricity of interior permanent magnetic motors (IPMSMs) in electric vehicles is proposed. Outperforming traditional methods, the proposed method can noninvasively diagnose not only the severities of static eccentricity (SE), dynamic eccentricity (DE), and mixed eccentricity (ME), but also the eccentricity location. In this article, diagnosis results are described through three eccentricity parameters: SE ratio, DE ratio, and SE angle. First, an analytical model of the open-circuit RSMFD of the IPMSM is proposed, with its accuracy validated by experiments. The pattern of the impact of the eccentricity parameters on the open-circuit RSMFD is analyzed to form the basis of the proposed method. Then, an eccentricity prototype motor, which can continuously emulate the eccentricity according to any listed eccentricity parameters, is developed. A test rig is built to collect the open-circuit RSMFD and validate the analytical calculation results. Finally, an eccentricity diagnostic model based on the open-circuit RSMFD is established. The diagnosis results proved the noninvasiveness, effectiveness, and viability of the proposed method. [ABSTRACT FROM AUTHOR]

In an interior permanent magnet synchronous motor (IPMSM) with segmented skewed poles, the armature reaction magnetic field (AR-MF) changes nonlinearly due to the saturation of the rotor magnetic barrier. Meanwhile, this varies under different excitation currents. As a result, it is difficult to be calculated by means of analytical methods. In this paper, the calculation model of AR-MF of IPMSM is first established by vector superposition method, without considering the saturation effect of rotor and the slotting effect of stator. In the second step, the virtual magnetic field of the rotor is introduced to quantitatively calculate the influence of local inhomogeneous saturation on the AR-MF. The latter is derived by combining both the subdomain method and equivalent magnetic circuit method. The complex relative permeance is also introduced to establish the AR-MF accounting for the stator slotting effect. To validate the AR-MF calculation method proposed, an 8-pole 48-slot IPMSM with segmented skewed poles is considered as a case study, showing a comparison by both with finite element (FE) results and the electromagnetic torque measured on a test bench. The model proposed in this paper shows high accuracy and fast computation with respect to FE analysis. [ABSTRACT FROM AUTHOR]

The forward computational modal analysis (CMA) of the motor stator assembly is gaining attention as a technical challenge in the area of motor noise. There is still no effective method to obtain accurate anisotropic material parameters (AMPs) required for CMA without prototype motors. In this paper, a novel forward calculation method (FCM) for calculating AMPs of the motor stator assembly is proposed, in considering structural discontinuities and composite material properties due to core lamination and winding stacking. The method is based on multi-scale theory. Firstly, the multi-scale equations coupling the macroscopic model and the mesoscopic model of the stator core and winding are established. By decoupling the multi-scale equations, the equivalence and equivalence preconditions of AMPs of the two scale models are described. Accordingly, the finite element method (FEM) for calculating AMPs of the stator core and winding based on the mesoscopic model is proposed. Then, the AMPs of the stator core and winding are calculated by the FCM, and the influencing factors are further studied, respectively. Finally, the effectiveness of this method is verified by modal experiments. Compared with experimental results, the maximum relative error of natural frequencies of the stator assembly is within 1.5%. This method can achieve accurate CMA without prototype motors and modal experiments, which contributes to the accurate prediction and control of electromagnetic noise in the initial motor design stage. [ABSTRACT FROM AUTHOR]

Due to the local inhomogeneous magnetic saturation of the core of the interior permanent magnet synchronous motor (IPMSM), the magnetic field changes nonlinearly, which makes the analytical calculation of the magnetic field difficult. Therefore, the calculation of the magnetic field mostly relies on the finite element method (FEM). However, the high computation cost of FEM restricts the efficiency of the design and analysis of IPMSM. In this article, an analytical model (AM) of slotless open-circuit air-gap magnetic field (OC-AG-MF) of IPMSM with V-shaped segmented skewed poles is derived by combining the subdomain method (SDM) and the magnetic equivalent circuit (MEC) method, and then, the AM of slotted OC-AG-MF of IPMSM with V-shaped segmented skewed poles is obtained by introducing the complex relative permeance. To show the effectiveness of the novel AM, the OC-AG-MF and cogging torque of an IPMSM with V-shaped segmented skewed poles for electric vehicles are calculated by the AM and FEM, respectively. The spatial order, amplitude–frequency characteristics, and the 3-D spatial distribution of the OC-AG-MF are analyzed. Finally, the accuracy of the AM is experimentally verified by direct measurement of OC-AG-MF and no-load back electromotive force (EMF) of the motor. The AM proposed in this article is shown to accurately calculate the radial and tangential components of OC-AG-MF of IPMSM with V-shaped segmented skewed poles considering rotor magnetic bridge saturation effect and stator slotting effect. Meanwhile, the efficiency of the design and analysis of the motor is expected to be improved due to the reduced computational effort compared to the prevalent FEM. [ABSTRACT FROM AUTHOR]

To accurately and quickly predict the open-circuit air-gap magnetic field in interior permanent magnet synchronous machines (IPMSMs), an analytical model based on magnetic equivalent circuit (MEC) method is proposed. The analytical model can provide radial and tangential components of open-circuit magnetic field in the slotless air gap. The radial component is obtained from the MEC model, and the tangential component is obtained from boundary conditions of macroscopic equations. Then, a complex relative air-gap permeance is applied to take the effect of slots into account. As a result, an accurate solution of both radial and tangential components of the flux density in the slotted air gap is obtained. Additionally, the no-load back electromotive force (EMF) and cogging torque are calculated based on the open-circuit air-gap magnetic field. All the analytical results are verified by the finite element (FE) analysis and they are well matched. In the end, a direct measurement experiment of open-circuit air-gap magnetic field is proposed to verify the validity of both radial and tangential open-circuit air-gap magnetic fields. [ABSTRACT FROM AUTHOR]

An eccentric position diagnosis method of static eccentricity (SE) fault of external rotor permanent magnet synchronous motor (ER‐PMSM) is presented. Firstly, an analytical model of no‐load radial magnetic field of ER‐PMSM is established. Analytical models of no‐load Back‐EMF of both unit motors and the whole motor are carried out and are verified by finite element method (FEM) and experimental measurements. Then, the influences of SE ratio, SE circumferential angle, winding distribution mode and number of parallel branches on no‐load radial magnetic field and no‐load Back‐EMF are analyzed based on these analytical models. The results show that SE does not affect the frequency characteristics of no‐load radial magnetic field, but changes space order characteristics. On one hand, for ER‐PMSM, of which the number of unit motors is equal to 1, SE causes no‐load Back‐EMF distortion. On the other hand, for ER‐PMSM, of which the number of unit motors is greater than 1, SE does not affect no‐load Back‐EMF of the whole motor, but it still leads to no‐load Back‐EMF distortion of unit motors. Therefore, based on total harmonic distortion (THD) of no‐load Back‐EMF of unit motor, a projection method of intersection lines for SE fault diagnosis of ER‐PMSM is proposed finally. [ABSTRACT FROM AUTHOR]

In this study, the air gap magnetic field characteristics of external rotor permanent magnet synchronous motors (PMSMs) under both the stator and rotor coordinate systems considering low‐order current harmonics and high‐order sideband current harmonics are analysed. A direct measurement technique (DMT) for air‐gap magnetic field is proposed. First, an analytical model of air gap magnetic field of external rotor PMSMs is established. The spatial order and frequency characteristics of stator/rotor air gap magnetic field are revealed. Then, a 24‐pole 27‐slot external rotor PMSM is taken as an example. The analytical and finite element (FE) results are compared and analysed. The difference of the spatial order and frequency characteristics between the stator and rotor air gap magnetic field are verified. Next, a new DMT is proposed, which can detect the precise distribution and local microscopic characteristics on the order of 10−1 mm with high resolution. The accuracy of analytical and FE model are verified by the DMT and an indirect experimental test of no‐load back electromotive force. Finally, the mechanical challenges of in‐wheel motors and the practicablility of DMT for eccentricity detection are further discussed. [ABSTRACT FROM AUTHOR]

3-D analytical model and direct measurement method (DMM) of ultra-thin open-circuit air-gap field (OCAGF) of interior permanent magnet synchronous motor (IPMSM) with multi-segmented skew poles (MSP) and multi-layered flat wire windings (MFWW) for electric vehicles (EV) are proposed. Basis functions of slotless OCAGF are derived through field reconstruction method (FRM). In order to consider MSP and slotting effects, a complex relative permeance function is extended from 2-D to 3-D. Based on the magnetic potential and permeance method, 3-D analytical model of OCAGF is obtained. Then the back electromotive force (BEF) is calculated through Faraday's Law and the cogging torque is obtained through Maxwell stress tensor method. Furthermore, spatial order and amplitude-frequency characteristics of OCAGF are revealed. Additionally, influence of local inhomogeneous saturation caused by PM materials on analytical accuracy is discussed. Finally, the proposed analytical model is verified through both the traditional indirect measurement methods (BEF measurement and cogging torque measurement) and a novel direct measurement method, in which ultra-thin OCAGF of 10−1 mm order of magnitude can be measured directly. Local microscopic characteristics of OCAGF in some important locations, such as tooth top and magnetic bridge, can be accurately detected by using of the direct measurement method. [ABSTRACT FROM AUTHOR]

The no‐load radial magnetic field and no‐load back electromotive force (EMF) of external rotor permanent magnet brushless DC motor (PMBLDCM) are calculated by applying the correction coefficient of magnetic conductance here, taking into account the stator slotting and static eccentricity effects. An external rotor PMBLDCM with 51‐slot/46‐pole, used as in‐wheel motor, is taken as an example, the analytical calculation results of the no‐load back EMF are validated by the finite‐element method and experiment. The influences of static eccentricity ratio on the no‐load radial magnetic field and no‐load back EMF are investigated based on the analytical model. The investigation shows that static eccentricity does not change the harmonic contents of no‐load radial magnetic field, so it does not change the harmonic contents of three‐phase no‐load back EMFs. However, static eccentricity changes the space order of no‐load radial magnetic field, resulting in the different total harmonic distortions of three‐phase no‐load back EMFs; in other words, the asymmetric distortions of three‐phase no‐load back EMFs are generated. The asymmetric distortions of three‐phase no‐load back EMFs are intensified with the increase in static eccentricity ratio. [ABSTRACT FROM AUTHOR]

Here, analytical expressions of the unbalanced magnetic force (UMF）of the stator and the rotor under static eccentricity (SE) are deduced by using complex relative magnetic conductivity method and Maxwell stress tensor method. The frequency characteristics of the UMF are obtained. Further the influence of different eccentricity ratio on the UMF is researched. Then, an external rotor permanent magnet brushless direct current motor (PMBLDCM) with 46 poles and 51 slots used as an in‐wheel motor is taken as an example to verify the frequency characteristics by finite element analysis (FEA). The research shows that the frequency characteristics of the UMF of the stator s related to electric frequency. The frequency characteristics of the UMF of the rotor are related to the power source frequency and the rotation frequency of the wheel. It does not introduce new frequency components when the motor SE occurs. As the SE ratio increases, the amplitude of the UMF increases. The UMF without eccentricity exists in all directions with the change of the time. However, as the eccentricity ratio increases, the direction of the UMF is closer to the eccentric direction. [ABSTRACT FROM AUTHOR]

This study presents an analytical model for calculating the armature reaction magnetic field of outer rotor permanent magnet brushless DC motor (PMBLDCM) in stator stationary coordinate system (SSCS) and rotor rotation coordinate system (RRCS). Firstly, an expression of armature reaction magnetic field of single‐phase winding is deduced, without considering slotting effect. Afterwards, analytical expressions of armature reaction magnetic field in both SSCS and RRCS regardless of slotting effect are obtained using vector addition method. Then complex relative permeances of outer rotor BLPMDCM in SSCS and RRCS are analysed, respectively. Finally, analytical solutions of the armature reaction magnetic field in both SSCS and RRCS are derived, respectively, by multiplying the slotless armature reaction magnetic field and the complex relative magnetic permeance, the self‐ and mutual inductance are calculated by the armature reaction magnetic field. A 46‐ploes‐51‐slots outer rotor BLPMDCM is set as an example, the accuracy of proposed analytical model is verified by the Finite Element Method. Based on this analytical model, the pattern of slotting effect on armature reaction of both outer rotor and internal stator are analysed, respectively, as well as spatial order characteristics and frequency characteristics of armature reaction for outer rotor PMBLDCM in SSCS and in RRCS. [ABSTRACT FROM AUTHOR]

An analytical method for calculating the no-load magnetic field of external rotor permanent magnet brushless direct current motor (PMBLDCM) used as in-wheel motor of electric vehicle in the stator static coordinate and the rotor motion coordinate is presented in this paper. First, the analytic formulas of slotless permanent magnetic field in both coordinate systems are derived, respectively. Then, the complex relative permeance of external rotor PMBLDCM in both coordinate systems is calculated. Finally, the analytical solution of the no-load magnetic field in both coordinate systems is derived by applying the magnetic potential multiplied by the complex relative permeance. In this paper, a 46-pole-51-slot external rotor PMBLDCM is taken as an example, and the accuracy of the proposed analytical model is verified by the finite-element results. Based on the analytical model, the influences of the stator slotting effect on the no-load magnetic field of the external rotor and the inner stator are analyzed. The spatial order characteristics and frequency characteristics of the no-load magnetic field of the external rotor PMBLDCM in both coordinate systems are revealed, respectively. [ABSTRACT FROM AUTHOR]

Based on neural network model, a method for quantitative sound quality (SQ) evaluation of the interior noise of a pure electric vehicle (PEV) is presented in this paper. The method can be divided into four steps. First, the interior noises under different speeds of a PEV are collected through the interior noise test of the PEV. Subsequently, one physical acoustic parameter (A-weighted sound pressure level) and six psychoacoustic parameters (loudness, fluctuation strength, tonality, roughness, articulation index, and sharpness) are applied to describe the noise samples for objective evaluation of SQ. In the third step, five semantic evaluation indexes, namely, “annoying or pleasing,” “harsh or sweet,” “weak or powerful,” “promiscuous and pure,” and “unobservable or perceptible,” are proposed based on semantic differential method, which are used for subjective evaluation of SQ by jury tests. Finally, the neural network model for SQ evaluation of the interior noise of the PEV is established, the SQ characteristics of the interior noise of the PEV are evaluated, as well as revealing the coefficient weight of influencing factors. This model can be used for SQ prediction and evaluation of the interior noise of the PEV considering that the average error is 9%. [ABSTRACT FROM AUTHOR]

A novel sound quality (SQ) evaluation method is developed to diagnose abnormal noise of interior permanent-magnet synchronous motors (IPMSM) for electric vehicle (EV). A-weighted sound pressure level (A-W SPL) of noise in IPMSM and six psychoacoustic characteristics, which include sharpness, roughness, loudness, articulation index, tonality, and fluctuation strength, are described through the objective evaluation of SQ. The paired comparison method (PCM) and the grade evaluation method (GEM) are respectively applied in subjective evaluation on relative annoyance and absolute annoyance of IPMSM for EV, and the combined application of these two methods is proposed originally. Finally, the BP neural network model for SQ evaluation of abnormal noise in IPMSM is established, the characteristics, conditions, and influencing factors of abnormal noise are effectively diagnosed. This novel evaluation method effectively solves the problem that the annoyance level is unable to be evaluated through the PCM, and the GEM relies on rich audition experience of evaluation subject. It also improves the accuracy of diagnosis of abnormal noise in IPMSM for EV. [ABSTRACT FROM PUBLISHER]

The existing evaluation methods and indexes of noise of electric motors cannot comprehensively reflect all the physical characteristics of noise of hub permanent-magnet synchronous motors (HPMSM) and human subjective sensations. In this paper, a method of the sound quality (SQ) evaluation of HPMSM for electric vehicles is proposed. The method is divided into three steps. In the first step, a noise objective evaluation of HPMSM with seven acoustical objective indexes, including loudness, roughness, A-weighted sound pressure level (A-W SPL), tonality, sharpness, articulation index (AI), and fluctuation strength, is made. In the second step, a noise subjective evaluation of HPMSM by using the grade evaluation method is made. The subjective annoyances (SA) of noise samples of HPMSM are obtained. In the last step, the SQ evaluation model of HPMSM by using the BP neural network theory is established. The average error rate of the proposed model is only 3.97%. By means of weight analysis, a comparison between the relative importance of acoustical objective parameters is found out. The main original contribution of this paper is that the proposed method can comprehensively reflect all the physical sound characteristics of HPMSM as well as their influence on human subjective sensations. [ABSTRACT FROM PUBLISHER]

This paper presents a novel black and white box method for diagnosis and reduction of abnormal noise of the hub permanent-magnet synchronous motors (HPMSMs). The black and white box method is divided into three steps. In the first step, a black-box method is used to identify and diagnose all of the abnormal noise sources and corresponding working conditions including rotational speeds and loading moments of the HPMSM. The proposed black method is independent of the detailed internal parameters of the HPMSM. In the second step, considering the abnormal noise sources and the corresponding working conditions diagnosed by the black-box method, a white-box method is used to propose and verify the electromagnetic field model, the structure vibration model, and the acoustic computation model of the HPMSM. Then, the components of the HPMSM whose vibrations and/or acoustic emissions are the most important are predicted. In the third step, the noise reduction method, which is aimed at the diagnosed abnormal noise source under the corresponding working conditions and the diagnosed components, is proposed. The proposed method in this paper observably raises the efficiency of diagnosis and optimization for abnormal noise of the HPMSM. [ABSTRACT FROM PUBLISHER]

This paper presents a quick and effective black-box method for identification and diagnosis of abnormal noise sources of permanent magnet synchronous machines (PMSMs) for electric vehicles. The black-box method is divided into three steps. In the first step, a black-box testing theory model with the rotational speed as the input signal and the noise frequency as the output signal is proposed. The main abnormal noise sources of PMSM for electric vehicles are taken into account in this model, such as harmonic currents, switching frequency of pulsewidth modulation, eccentricity, sliding bearing, and resonance. In the second step, a black-box testing experiment of noise of PMSM is applied under acceleration conditions and the sound quality of PMSM is analyzed with objective acoustic indicators, and psychoacoustic indicators as well. In the third step, abnormal noise sources are identified and diagnosed by means of the black-box testing theory and the black-box testing experiment. Noise contribution to psychoacoustic indicators is further analyzed. The proposed method is independent of detailed internal parameters of PMSM, such as structural parameters and electromagnetic parameters, and observably raises analyzing efficiency. [ABSTRACT FROM PUBLISHER]

Traditional membrane electrode assembly, prepared by catalyst coated electrodes (CCE) and catalyst coated membrane (CCM), has a huge interface between electrodes and membranes, which affects the mechanical adhesion, proton/electron transfer and gas/liquid transport in proton exchange membrane fuel cells (PEMFCs). In this study, an integrated membrane electrode assembly (I - MEA) was fabricated by the casting and doctor blade methods for low- and high-temperature PEMFCs, respectively. The results show that the maximum power density of I - MEA LT is improved around 18% and its stripping force increased from 6.091 N to 7.387 N. I-MEA HT reached 0.418 W/cm2, which is 1.5 times higher than that of traditional MEA HT. Meanwhile, it achieved the maximum stripping force of 9.374 N. • I-MEA LT fabricated by the casting method achieves 18% improvement of the power density. • I-MEA HT fabricated by the doctor blade method improves 1.5 time in the power density. • Integration membrane electrode assembly significantly enhance the mechanical strength. [ABSTRACT FROM AUTHOR]

The application of electric motor emulators (EME) has been prosperous in recent years along with the advancement in power hardware-in-the-loop technology. However, EME design methods based on a typical modeling approach and control structure tend to be invalid in promising a clear, dynamic accuracy objective and a robust dynamic accuracy performance over wide working points, especially at high operating speed. Hence, a new EME design method based on multi-input multioutput (MIMO) modeling and a MIMO closed-loop current control (MCLCC) structure is proposed in this article. Singular values of the MIMO motor model are analyzed to clarify the influence of the rotor speed on the dynamic accuracy objective of EME for the first time, based on which an unknown input observer is designed in the MCLCC structure to compensate for disturbance voltages caused by modeling errors. The transient tracking errors of both current and torque responses can thus be remarkably reduced at 300-Hz electrical speed in the experiment even if 35% modeling errors exist, verifying the superiority of the proposed EME design method in dynamic accuracy. [ABSTRACT FROM AUTHOR]

In order to better address the problem of many high-order harmonics’ concentration in the output voltage, a novel five-phase piecewise-random-switching-frequency space vector pulse width modulation (PRSF-SVPWM) strategy is proposed for a five-phase voltage source inverter. Compared to the conventional random switching frequency SVPWM (RSF-SVPWM), the entire fundamental period of this method is divided into two half-fundamental periods, so the original switching frequency in a single fundamental period is randomized in segments respectively. During this process, parameters named the offset frequency and random frequency are defined and assigned reasonably. In this way, high-frequency harmonics in one period are spread into a wider range. Subsequent simulation and experimental results verify that the proposed random modulation strategy can further reduce amplitudes of harmonics near switching frequency and its integer multiples, even though within a narrow switching frequency range, and a satisfactory effect of high-order harmonic dispersion is finally obtained, which contributes to the application and popularization of random pulse width modulation strategies. [ABSTRACT FROM AUTHOR]

• Phase field modelling for fracture of elasto-plastic solids is implemented in Abaqus. • The proposed implementation is verified analytically in the one element example. • The simulated fracture behaviour agrees with the results in literature. Phase field modelling for fracture has been extended from elastic solids to elasto-plastic solids. In this study, we present the implementation procedures of a staggered scheme for phase field fracture of elasto-plastic solids in commercial finite element software Abaqus using subroutines UEL and UMAT. The UMAT is written for the constitutive behaviour of elasto-plastic solids, while the UEL is written for the phase field fracture. The phase field and displacement field are solved separately using the Newton-Raphson iteration method. In each iteration, one field is computed by freezing the other field at the last loading increment. A number of benchmark examples are tested from one single element up to 3D problems. The correctness of the staggered scheme is verified analytically in terms of the stress-strain curve and the evolution of the phase field in the one single element example. In the 2D and 3D problems, the fracture behaviour of elasto-plastic solids can be reproduced in terms of reaction force curve and crack propagation, which exhibit good agreement with the experimental observations and numerical results in literature. Not only can the proposed implementation help attract more academic researchers, but also engineering practitioners to take the advantages of phase field modelling for fracture in elasto-plastic solids. The Abaqus subroutine codes can be downloaded online from Mendeley data repository linked to this work (The link is provided in Supplementary material). [ABSTRACT FROM AUTHOR]

State of charge (SOC) estimation of lithium batteries is one of the most important unresolved problems in the field of electric vehicles. Due to the changeable working environment and numerous interference sources on vehicles, it is more difficult to estimate the SOC of batteries. Particle filter is not restricted by the Gaussian distribution of process noise and observation noise, so it is more suitable for the application of SOC estimation. Three main works are completed in this paper by taken LFP (lithium iron phosphate) battery as the research object. Firstly, the first-order equivalent circuit model is adapted in order to reduce the computational complexity of the algorithm. The accuracy of the model is improved by identifying the parameters of the models under different SOC and minimum quadratic fitting of the identification results. The simulation on MATLAB/Simulink shows that the average voltage error between the model simulation and test data was less than 24.3 mV. Secondly, the standard particle filter algorithm based on SIR (sequential importance resampling) is combined with the battery model on the MATLAB platform, and the estimating formula in recursive form is deduced. The test data show that the error of the standard particle filter algorithm is less than 4% and RMSE (root mean square error) is 0.0254. Thirdly, in order to improve estimation accuracy, the auxiliary particle filter algorithm is developed by redesigning the importance density function. The comparative experimental results of the same condition show that the maximum error can be reduced to less than 3.5% and RMSE is decreased to 0.0163, which shows that the auxiliary particle filter algorithm has higher estimation accuracy. [ABSTRACT FROM AUTHOR]