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Accurate calculation of magnetic field distribution is a prerequisite for motor design and optimization. This paper develops an analytical subdomain model of external rotor in-wheel motor with surface-inset magnets (ERIWMSIM). Besides, to weaken its torque ripple, an improved topology by integrating magnetic flux modulation slots (MFMS) into tooth...
Context in source publication
Context 1
... L a is the axial length of the stator lamination, a 1 is the number of parallel branches of the windings, C is the connection matrices between the stator slots and the three-phase current, which stand for the distribution of the double-layer windings in the slots and given by the following equations, and Fig. 4 shows the connection diagram of the armature windings of the ERIWMSIM: ...
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Citations
... Outer rotor machines are particularly favored for in-wheel applications. Unlike the utilization of PM-based electrical machines for in-wheel electric vehicle applications [248], the investigation of the outer rotor VFRM has not been completely addressed in the literature. The inner and outer rotor topologies of the VFRM intended for heavy-duty applications are compared in [40], where an initial design study is conducted on both structures to maximize torque density and efficiency at the nominal speed while minimizing torque ripple. ...
... The main source of torsional in-wheel drivetrain dynamics is the tire, and although in practical EV implementations no specific controller is strictly required to attenuate the associated vibrations, the study in [5] presents a dedicated fuzzy logic algorithm. The torque ripple of in-wheel machines, which is directly transmitted to the wheel, can also affect comfort on smooth road surfaces [6], [7], and is attenuated through appropriate motor design or control [8]- [10]. Moreover, given the absence or the significantly reduced volume of the powertrain components installed on the EV sprung mass, in-wheel powertrains allow enhanced freedom in the design of the vehicle interiors. ...
Road irregularities induce vertical and longitudinal vibrations of the sprung and unsprung masses, which affect vehicle comfort. While the vertical dynamics and related compensation techniques are extensively covered by the suspension control literature, the longitudinal dynamics on uneven road surfaces are less frequently addressed, and are significantly influenced by the tires and suspension systems. The relatively slow response of internal combustion engines does not allow any form of active compensation of the effect of road irregularities. However, in-wheel electric powertrains, in conjunction with pre-emptive control based on the information on the road profile ahead, have some potential for effective compensation, which, however, has not been explored yet. This paper presents a proof-of-concept nonlinear model predictive control (NMPC) implementation based on road preview, which is preliminarily assessed with a simulation model of an all-wheel drive electric vehicle with in-wheel motors, including a realistic tire model for ride comfort simulation. The major improvement brought by the proposed road preview controller is evaluated through objective performance indicators along multiple maneuvers, and is confirmed by the comparison with two benchmarking feedback controllers from the literature.
... The cogging torque is caused by the tangential component of the interaction force between the permanent magnet and the armature teeth. The main methods to reduce cogging torque and torque ripple include optimizing the slot opening width and pole-slot combination [3][4][5], optimizing the pole-arc coefficient [3,6], notching the auxiliary slot on top of the stator teeth [3,7], skewing slot and skewing pole [8], magnetic pole shifting [9], magnetic pole segmentation [10], optimizing magnetic pole shape [11][12][13][14], etc. Y. Park applied the halbach magnet array to reduce the leakage flux and improve the efficiency by reducing the iron loss of the motor. In addition, the design for reducing the weight of the motor was carried out in [15].M. Fazil proposed a new air-gap profile for the single-phase permanent-magnet BLDC (SP PM BLDC) motor to improve the starting torque and to reduce the cogging torque [16]. ...
... Cogging torque is a periodic fluctuant force that is caused by the interaction between PMs and slots, and adversely affects the smoothness of motion, particularly in low speed. Reference [31] theoretically analysed the coefficient of the lowest harmonic of cogging torque in the BLDC motor, which can be expressed as (5). ...
The mass production of the motors causes tolerance of shape and dimension, deviation of permanent magnet remanence and rotor eccentricity error, which affect the cogging torque and torque ripple amplitude and performance consistency. In order to reduce the torque ripple of the motor in the actual condition, the robustness optimization is performed in the paper. Firstly, an improving convex arc type permanent magnet structure is adopted to improve air gap flux density and suppress the cogging torque. Secondly, the structure parameters of the magnetic pole are selected as optimization variables, and the magnetization angle, remanence and position of the permanent magnet, static and dynamic rotor eccentricity are considered as noise factors. To improve the overall robustness of the motor under different operating conditions, the dynamic Taguchi method is used to optimize the robustness of the motor, and the test data is processed through the relation analysis method to obtain the optimal combination of control factors. Finally, the prototype is manufactured for the experiment. Compared with the single‐operating conditions robust optimization results, the robust optimization method improves the robustness of the motor. The cogging torque amplitude is reduced by 39.2%. The torque ripple is 38.4% lower than that before optimization.
... Subsequently, combined with some iterative algorithms, the nonlinearity of iron (i.e. B-H curve) can be considered (Djelloul-Khedda et al., 2017;Zhang et al., 2021aZhang et al., , 2021b. Setting a more significant maximum harmonic order (MHO) in the air-gap region can increase the accuracy of torque prediction. ...
... Each subdomain's governing equations are established in 2-D polar coordinates according to the type of excitation sources. Namely, the PM and stator slot regions satisfy Poisson's equation, while the air-gap and slot opening regions satisfy Laplace's equation (Zhang et al., 2021a(Zhang et al., , 2021b: ...
Purpose
This study aims to accurately calculate the magnetic field distribution, which is a prerequisite for pre-design and optimization of electromagnetic performance. Accurate calculation of magnetic field distribution is a prerequisite for pre-design and optimization.
Design/methodology/approach
This paper proposes an analytical model of permanent magnet machines with segmented Halbach array (SHA-PMMs) to predict the magnetic field distribution and electromagnetic performance. The field problem is divided into four subdomains, i.e. permanent magnet, air-gap, stator slot and slot opening. The Poisson’s equation or Laplace’s equation of magnetic vector potential for each subdomain is solved. The field’s solution is obtained by applying the boundary conditions. The electromagnetic performances, such as magnetic flux density, unbalanced magnetic force, cogging torque and electromagnetic torque, are analytically predicted. Then, the influence of design parameters on the torque is explored by using the analytical model.
Findings
The finite element analysis and prototype experiments verify the analytical model’s accuracy. Adjusting the design parameters, e.g. segments per pole and air-gap length, can effectively increase the electromagnetic torque and simultaneously reduce the torque ripple.
Originality/value
The main contribution of this paper is to develop an accurate magnetic field analytical model of the SHA-PMMs. It can precisely describe complex topology, e.g. arbitrary segmented Halbach array and semi-closed slots, etc., and can quickly predict the magnetic field distribution and electromagnetic performance simultaneously.
... Shin et al. [27] obtained optimal slot opening and pole arc ratio to minimize the cogging torque of SPM machine by using the subdomain analysis. The torque ripple change due to the flux modulation slot of SPM machine was also well predicted [28]. However, the cores are assumed to be infinitely permeable in most subdomain analysis. ...
... According to (28), the phase difference α rl − α θl of the field harmonics determines the lth order torque component along with the magnitude, T l . In the machine under consideration, the 11th and 13th harmonic components are dominant. ...
Since the slot opening is large in the uniform slot machine, the torque ripple generated by overlapping or misaligning with the rotor cavity is remarkably large in the case of interior permanent magnet (IPM) machine. In this work, it is observed that the magnitude of torque ripple depends strongly on the phase difference between air-gap field harmonics: The ripple is minimized when the two dominant harmonic components cancel each other. Based on this fact, a condition is developed to minimize torque ripple by adjusting the q-flux channel width and d-flux barrier width. The torque ripple minimizing solution is found from a level chart made by subdomain time-stepping analysis. Finite element analysis (FEA) also gives a very similar minimizing solution. A prototype machine is manufactured, and its performances are validated through experiments.
The magnetic lead screw (MLS) applied to the point-absorbing wave energy converter (WEC) can convert the low-speed linear motion of the buoy into a high-speed rotational motion that can drive a rotating motor to generate electrical power. Aiming at the high permanent magnet (PM) consumption of the traditional MLS, a novel type of consequent-pole MLS is proposed in this paper, a consequent-pole type is adopted on the translator to save the PM consumption. At the same time, the traditional bipolar type is adopted on the rotor to increase the maximum thrust force. To analysis the performance of the proposed MLS, a three-dimensional (3-D) analytical method (AM) model is proposed. Two different materials that are non-ferromagnetic and ferromagnetic, for teeth between the helical PMs on the translator can be considered in the proposed model. To verify the model, a prototype of the proposed MLS and its test platform is developed. To ensure that the manufactured prototype is closer to the design one, a new helical PM installation method through the bolts is introduced in this paper. And a corresponding improved thrust force and torque equations are proposed for the prototypes which the installation method used. Finally, the comparative results of 3-D AM, 3-D finite element method (FEM) model and experiment are given.
As the demand for drive quality in automotive hub motors is increasing, the need for reduced cogging torque is also increasing. In this paper, the cogging torque of a soft magnetic composite (SMC) based yokeless and Segmented Armature (YASA) Axial Field Permanent Magnet Motor is investigated. Three models of YASA motor with skewed stator slot, segmented shift and unequal stator slot width are developed and the cogging torque waveforms of the three stator topologies are analyzed and compared. The output performance of the motor with the three topologies was analyzed by 3D finite element simulation, including no-load back EMF, electromagnetic torque and torque ripple, and axial magnetic force. The results show that all three stator topologies can effectively reduce the cogging torque and torque ripple in the YASA motor. Compared with the pre-optimization structure, the output torque of the skewed stator slot and segmented shift stator structure decreases more, while the output torque of the unequal stator slot width structure remains almost the same. Meanwhile, the axial magnetic force is almost constant before and after the optimization of the three stator topologies.KeywordsCogging torqueYASA structureSkewed stator slotSegmented shift statorUnequal stator slot width
The hybrid subdomain method (HSDM) combining conventional SDM with equivalent magnetic network has been proved to be a qualified approach to field prediction. However, this method still suffers two issues: first, the saturation effect of stator core is considered but that of rotor core is ignored, thus causing no-accuracy calculation; second, the mathematical complexity is inevitable due to adoption of virtual line-current density as extra interface conditions. This work is to develop an improved HSDM (IHSDM) for accurately and efficiently predicting the electromagnetic performance of a field-modulated permanent-magnet motor. The key of the proposed IHSDM is to fully consider magnetic saturation inside both stator and rotor cores. More importantly, the replacement of virtual-line current density by virtual-surface magnetization and current density makes interface conditions as simple as the SDM. The quantitative comparisons with conventional HSDM and FEA are conducted and the prototyping tests are also performed. It shows that the proposed IHSDM has lower time consumption and occupied memory, and electromagnetic quantities have about two times more accuracy than conventional HSDM. Additionally, a dynamic calculation is achieved by the IHSDM and verified by FEA.
The 2-D subdomain method (SDM) has proven to be a time-efficient approach suited for determining the magnetic field of permanent magnet synchronous motor (PMSM). However, further application of this method into the field analysis for the line-start PMSM (LSPMSM) is limited by its natural defects including (a) inability to consider the saturation effect of iron material and (b) failure to deal with the rotor eddy currents allowing self-start. In this work, the step-by-step or iterative numerical calculation using the finite difference method (FDM) is embedded into the execution of conventional 2-D SDM, through which an enhanced version addressing all issues as stated above is obtained. The improved SDM avoids limitations of pure analytical method and possesses higher calculation efficiency than that of pure numerical method. Reliability of the presented method is validated by the finite element analysis (FEA) and tests.
