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This paper applied the finite-element method (FEM) with topological data structures to the optimization of electrical devices. A generic modifiable graph data structure is built according to the graph-theoretic foundation for these data structures. The employed topological FEM avoids rebuilding of the mesh in traditional FEM method while geometrical variations happen. It is an effective algorithm which can save computer storage and working time when applied to successive optimization. The effectiveness is verified by numerical example and comparison of the topological FEM with traditional FEM on storage load and working time is shown in this paper. [ABSTRACT FROM AUTHOR]

This paper proposes the multi-material topology optimization for the simultaneous design of segmented permanent magnet (PM) arrays, coil, and iron materials in magnetic actuators. Specifically, the proposed approach can find the optimal layout and shape of PM, coil, and iron materials, as well as the optimal border and magnetization direction of segmented PM arrays. For designing the layout and shape of actuator components, the discrete material optimization-type material interpolation scheme is employed in this paper. To attain the design of segmented PM arrays, an orientation design variable in Cartesian coordinate is utilized with the penalization scheme for the discrete PM magnetization directions. To validate the effectiveness of the proposed actuator design approach, two numerical examples are presented. In the examples, the actuator components (i.e., segmented PM arrays, coil winding, and back iron) are designed aiming for maximizing the magnetic force magnitude acting on the actuator plunger. [ABSTRACT FROM AUTHOR]

The near-field communication (NFC) technique finds wide applications in many aspects of modern life, e.g., contactless payment systems or authentication. Regardless of the application, typically, the requirements on the antenna structure are manifold. Frequently, limitations in the available space make the antenna design quite challenging. Beside geometrical limitations, also the matching of the antenna structure to the analog front end of the NFC transponder IC has to be taken into account. Furthermore, the NFC antenna together with the connected IC has to fulfill specific standardized values. In this paper, the optimization of an NFC antenna structure including the needed matching circuit in the multi-objective sense is proposed. Due to its simplicity and the consequently reduced computational effort, the partial-element electric circuit (PEEC) method is applied to carry out the needed field computation in the so-called NFC operating volume. Furthermore, the PEEC method offers the possibility of simply connecting lumped components to the antenna structure within the numerical analyses, which enables the optimization of the matching circuit parallel to the optimization of the antenna structure. The optimization relies on a stochastic optimization strategy, namely, the firefly algorithm (FFA). In this paper, an extended version of the general FFA is applied. [ABSTRACT FROM AUTHOR]

In this paper, we propose a design process for a plasmonic grating structure to induce the resonance at a target wavelength. In a specific condition, surface gratings may induce the surface plasmon propagation due to the diffraction and the resonance wavelength of the surface plasmon propagation is dependent on the grating shape. The grating configuration was designed by the topology optimization scheme based on the reaction-diffusion equation. To shift the resonance wavelength to the target wavelength, this paper maps the frequency response function to a probability distribution function (PDF). The mean value from the PDF becomes a part of the objective function and the design objective is set to minimize the distance between the present resonance wavelength and the target wavelength while keeping the energy intensity. The process of simulation and optimization was performed using the commercial package COMSOL combined with MATLAB programming. [ABSTRACT FROM AUTHOR]

Electromagnetic devices containing permanent magnet (PM) are common and typical electromagnetic devices that have advantages of low-power consumption, small size, high sensitivity, and its optimization problem has aroused widespread concern. Calculation accuracy of electromagnetic properties and efficiency of optimization processes are two important factors that affect the optimization effect of electromagnetic devices. A fast calculation method was proposed in this paper that aimed at electromagnetic devices with PM characteristics of strong non-linearity and low solving precision. The response surface method was used to derive the basis function, and the error between actual measured values and calculated values was modified by the Kriging method. On the basis of the calculation model, the distributed collaborative strategy was adopted to fulfill the parallel execution of the fast computation. Simultaneously, the updating strategy of particles was improved, and the robustness of the multi-objective particle swarm optimization algorithm in solving the optimization problem of electromagnetic devices with PM was enhanced. Effectiveness of the method proposed in this paper was verified by the case study of a specific type of electromagnetic relay with PM. [ABSTRACT FROM AUTHOR]

Recently, electric power consumption has increased rapidly owing to the development of electric devices, and thus environmental problems such as global warming have come to the fore. Therefore, developed and developing countries are preparing various measures to prevent global warming. Minimum energy performance standards (MEPS) are one of the representative measures. MEPS is an efficiency regulation for induction motors that limits the minimum efficiency with regard to the power of the induction motors, in order to save energy. Studies have been conducted on induction motors to improve the efficiency and to satisfy MEPS. However, It is very difficult to satisfy the efficiency of induction motor for MEPS. Therefore, synchronous reluctance motors (SynRMs) are actively being studied to replace induction motors. In this paper, a SynRM is designed using a Kw-map. Moreover, to improve the output characteristics, the rib thickness of the SynRM is optimized using the response surface method. Finally, the validity of the design method, proposed in this paper is verified with a real test using the prototype. [ABSTRACT FROM AUTHOR]

The magnetic recording industry is perennially trying to grow the areal density by optimizing the head/media, the coding/signal processing, and the bit length (BL) and track pitch (TP) of the data written on the medium. Writing data at smaller BL or TP on the medium lead to loss of SNR during readback, which can be corrected by the coding and signal processing subsystem at the cost of the code rate $R$ . The optimization of the BL, TP, and code rate for a given head and media is the task of the system integrator. In this paper, we make use of an advanced channel model: the grain-flipping probability model, to perform an equivalent optimization together with a software recording channel that is able to include the impact of the generalized partial response equalizer, soft-output Viterbi algorithm detector, and low density parity check decoder on the final performance. In this paper, we vary the BL, TP, and code rate $R$ in the simulations to search for the highest user areal density achievable for a given head/medium setup. We investigate the effect of having a constant reader width (RW) as well as with RW proportionate to TP in our channel model. We also investigate the effect of more advanced 2-D coding and detection schemes on the final system performance. [ABSTRACT FROM PUBLISHER]

In this paper, we present systematic micromagnetic modeling investigation on recording process of segmented thin-film media with circularly polarized magnetic field at microwave frequencies. This paper provides insightful understanding about the segmented medium stack design in microwave-assisted magnetic recording (MAMR) by exploring the impact of signal-to-noise (SNR) ratio and recording track width. By utilizing segmentation of grains with exchange breaking layers, the ac magnetic field generated from spin torque oscillator can be best exploited. Via optimized medium stack design, MAMR is able to achieve both high SNR and areal density gain with the proposed notched-structure medium (top and bottom segments have the strongest crystalline anisotropy) compared with conventional graded medium (with gradually increasing anisotropy from top to bottom). By tuning crystalline anisotropy strength in top and bottom segment, we studied the MAMR behavior of SNR and track width under different ac frequencies. This provides a novel view for future segmented media design. [ABSTRACT FROM AUTHOR]

For the purpose of saving energy resources, it is extremely expected to develop highly efficient electric motors. Different types of permanent magnet (PM) arrangement can significantly affect the performance of the motors. Conventionally, the arrangement of the PMs is determined by designer’s experience. This paper focuses on the optimal design of PM arrangement in PM synchronous motors (PMSMs). We present a general pattern of the PM arrangement in PMSM. By varying the parameters of the general pattern, it can produce different types of PM arrangement in the rotor. The employed approach combines the global optimization method with the finite-element method for solving the optimization of the PM structures. Based on the proposed general pattern and optimization methods, the best PM arrangement in the motor can be automatically determined. In order to reduce computing loading, this paper employs the response surface models for reducing the computing time of objective functions. In the end, numerical tests are designed to showcase the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Recent expansion of emerging wireless power transfer technology has not been followed by an adequate systematic approach to the magnetic couplers design. The relation between design parameters (mutual inductance, coupling coefficient, leakage field flux density, coil quality factor, and so on) and structural parameters (coils and ferrite shape, size, thickness, and so on) has not been thoroughly explored, and practical designs often depend on trial-and-error methods supported by the finite-element modeling simulation to verify a final design. In order to fill that gap, this paper describes the adoption of multi-objective hybrid particle swarm optimization (MOHPSO) and multi-objective real-numbered particle swarm optimization (MORPSO) algorithms for a circular coupler design to increase performances and automate the design process. Objectives of this paper are threefold: 1) apply MOHPSO and investigate if there are some unconventional structures of circular couplers capable of outperforming traditional designs; 2) identify a minimum set of key optimization parameters for a circular magnetic coupler; and 3) demonstrate the operation of an MORPSO algorithm to optimize a circular magnetic coupler. The Pareto front concept is applied to provide multi-objective optimization. Two different multi-objective function pairs are considered, the first pair being the coil coupling coefficient ( k ) and maximum leakage field magnetic flux density ( B\max ); for the second pair, the product between quality factor ( Q ) and k is combined with ( B\max ). To validate the optimization algorithm effectiveness and accuracy, a selected magnetic coupler is fabricated and tested. Due to superior execution time, and satisfactory optimization capabilities, the MORPSO algorithm is employed to generate a final optimum design. Collected measurements demonstrate a very good agreement between the experimental and simulation results. [ABSTRACT FROM PUBLISHER]

This paper investigates material interpolation schemes in multi-material topology optimization (MMTO) for magnetic device design. Different interpolations of material properties lead to a non-unique layout and differences in performance, thereby affecting the initial design dependence. However, there is a lack of research on material interpolation in MMTO for the magnetic design problem. In this research, two types of material interpolation schemes are compared: recursive multiphase (RM) and discrete material optimization (DMO). To compare only the effects of material interpolations, the non-convex feasible set of material constraints in RM interpolation schemes were transformed into the convex feasible set by a linear form. The performance profile was employed to obtain the global performance of each interpolation scheme. Examples of the C-core actuator and the permanent magnet actuator (PMA) were applied for performance comparison, and the performance profile indicated that the DMO interpolation scheme is robust to initial material distributions and different material constraints compared to the RM interpolation scheme. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to optimize the design of a dual-structure permanent magnet (PM) machine for the low-speed application. Multi-objective optimization using nondominated sorting genetic algorithm II (NSGA-II) is used to maximize the torque and efficiency while reducing the torque ripple of the machine. The torque, torque ripple, and efficiency of the optimized machine have significant improvement by optimizing the machine parameters within a fixed outer axial and radial length. This optimization process can be used to select the best machine design in different aspects’ requirement. [ABSTRACT FROM AUTHOR]

This paper investigates different spatial filtering techniques used with ON/OFF based topology optimization and compares their performances for optimizing a C-core electromagnetic actuator. The filters’ efficacy in dealing with checkerboard patterns, perforations, and floating material pieces and their impact on the armature force and the topology’s smoothness are evaluated and discussed. [ABSTRACT FROM AUTHOR]

Microwave-assisted magnetic recording (MAMR) is an advanced magnetic recording scheme that is expected to extend the areal density beyond that achieved by conventional perpendicular magnetic recording (PMR). This is done by introducing a high-frequency (HF) oscillating magnetic field during the writing, reducing the write field from the head needed to switch the grains. Grains with larger anisotropy, greater thermal stability, and reduced grain size can thereby be used in the media. 3-D-MAMR uses this same principle not only to assist the writing but also to select a particular layer in a multi-layer medium stack for writing, thereby realizing 3-D magnetic recording. Optimization of a 3-D-MAMR system is complicated by the large number of variables involved and interactions between the recording layers. It is generally difficult to write on a target layer without some degree of unwanted writing on a different layer in a multi-layer stack. In this paper, we perform an optimization of a 3-D-MAMR media stack using the response-surface methodology (RSM), a method used in the design of experiments (DoEs). This results in a media design in which the signal-to-noise ratio (SNR) performance in the target layer and the number of written errors in the other layer are jointly optimized. [ABSTRACT FROM AUTHOR]

Electric machine design optimization is a popular topic in electrical engineering. Thanks to major accomplishments in Mathematics and Computer Science, nowadays the investigation of thousands of designs for particular optimization tasks is possible. Huge effort is made for developing evermore complex multi-physics simulation models including, e.g., thermal or mechanical aspects besides electromagnetic performance investigation. The impact of tolerances is often disregarded. This paper gives an overview of recent activities in machine design optimization. Consequently, the implementation of tolerance analyses for machine designs is explained. A categorization based on mathematical tolerance representations, typical tolerance-affected parameters and their respective modeling effort, as well as measures for evaluating the impact of tolerances, i.e., the design’s robustness, are discussed. An exemplary sensitivity analysis featuring an interior permanent magnet synchronous machine with spoke-type rotor structure is introduced. The performance of two different designs in the presence of uncertainties is investigated. Results reveal the importance of incorporating tolerance analyses to electric machine design optimization. [ABSTRACT FROM AUTHOR]

Proton precession magnetometer (PPM) is a potential device to measure the low-frequency geomagnetic field in the time domain. Nevertheless, the uncontrollable noise such as power frequency noise, random noise, etc., severely affects the detection results. In this paper, aimed to boost the performance of the PPM, a novel real-time processing algorithm for the optimization of PPM output strategy based on the low-rank constraint (LRC) is proposed, and a new efficient framework, dubbed LRC-based geomagnetic data readout optimizer (LRC-GDRO), is implemented. This method aims to extract the dominant principal components of the pure magnetic signal and identify the singular values of noise. Thereby, the relative ideal signal without external noise, which still contains the ambient field information is yielded. Moreover, we develop a prototype device and compare the test results before and after using the proposed method. Consequently, compared with traditional PPM, the performance of the PPM using the proposed method has been significantly improved with a measurement accuracy of ± 0.2 nT. Furthermore, the experimental results reveal that the LRC-optimized PPM is comparable to a very high-accuracy Overhauser magnetometer in terms of 12 h geomagnetic field observation. [ABSTRACT FROM AUTHOR]

Linear antenna arrays consisting of dipole antennas find wide applications in wireless communication systems. Typically, arrangements with uniform spacing between the array elements are applied to gain highly directive radiation patterns while controlling the radiation intensity in the side lobes. To describe such arrangements, the so-called pattern multiplication (PM) technique is frequently applied, which inherently neglects the inter-element coupling. In this paper, an antenna array arrangement with non-uniformly spacing between the array elements is synthesized in the multi-objective sense. Therefore, the PM technique is deficient. Hence, numerical techniques have to be applied to compute the electromagnetic field during the optimization process. Due to its simplicity and the consequently reduced computational costs, the partial element equivalent circuit method is applied within the field computation process. The optimization relies on a stochastic particle swarm optimization strategy, namely the firefly algorithm. In this paper, an extended version of the general algorithm with additional hierarchical clustering is applied. Special attention is drawn to the development of a suitable objective function. [ABSTRACT FROM AUTHOR]

Recently, the layout optimization of the secondary coils for wireless power transfer systems has been developed using the fixed grid (FG) representation. Although this method can effectively and efficiently determine the optimized coil design under the given conditions, a distinct discrepancy exists between the evaluated coil mass (i.e., simulation data) and the physical coil mass (i.e., experiment data). In this paper, the FG-based coil layout optimization is revisited based on the smooth boundary (SB) representation in order to resolve the inherent drawbacks of the FG representation. Induced voltage, electromagnetic field strength, and coil mass, which have been previously derived in the FG representation, are reformulated in terms of design variables (i.e., a reference turn and relative turns in this paper) in the SB representation. Through the layout optimization, the optimized layouts of the secondary coil are determined in order to minimize the coil mass while satisfying the constraints for induced voltage and magnetic field strength; then, they are postprocessed in order to obtain a smooth, elaborate boundary. The experimental validation demonstrates that the proposed SB-based approach outperforms the previous FG-based method in terms of coil mass and boundary representation. [ABSTRACT FROM AUTHOR]

This paper focuses on the computation time and precision of a linear 2-D magnetic gear analytical model. Two main models of magnetic gears are studied: 1) the first with an infinite relative permeability of yokes and 2) the second with a finite relative permeability of yokes. These models are based on the subdomain resolution of Laplace and Poisson equations. To accurately compute the magnetic field distribution, it is necessary to take into account certain harmonics of the various rings and other system harmonics due to modulation. Global system harmonics, which increase the value of computation time, must also be taken into account. If the magnetic gear has a high pole number, then computation time increases even more and no longer allows for system optimization. This paper proposes to compute magnetic field distribution using different harmonic selection methods in order to significantly reduce the computation time for the magnetic torque without any loss of accuracy. [ABSTRACT FROM AUTHOR]

This paper presents a multi-objective optimized design for a 75 kW, 24 000 r/min high-speed surface-mounted permanent magnet synchronous motor (SMPSM) for a magnetically levitated flywheel energy storage system. The main goal of the optimization process is to determine the optimal motor geometry, and thus obtain maximum efficiency, minimum weight, and minimum torque ripple in the SMPSM. To achieve this goal, three objective functions are used. The first function is used to obtain maximal output torque, and thus produce highest efficiency; the second function is used to minimize materials utilization to realize the lowest possible production cost; and the third function is used to achieve minimal torque ripple, and thus constrain the motor’s vibration and noise. The optimization process uses an ant colony algorithm with continuous domains. The optimized motor parameters can be selected from the Pareto solution set obtained. A comparison of the results calculated using the optimization algorithm with the results obtained using finite-element analysis software shows a good agreement. [ABSTRACT FROM AUTHOR]

This paper proposes the design and multi-mode operation of a new double-stator toroidal-winding permanent-magnet vernier (DSTW-PMV) machine, which is for the wind-photovoltaic (W-PV) hybrid generation system. In the W-PV system, the wind and PV power are complementary with each other for power variation reduction. Through the multi-mode operation, the output voltage of the machine can be stabilized with high continuity under different rotational speeds to solve the inherently indeterminate wind speed problem and further improve the power smoothness of the whole W-PV system. First, the machine optimization is carried out to obtain the optimal pole-pair combination and geometrical topology for the proposed machine. Second, based on the optimal topology, the multi-mode operation principle of the output voltage adjustment is illustrated. By utilizing the diversities of the toroidal winding configurations and terminal connection strategies, the proposed machine accommodates 54 operating modes with different output voltages under rated speed. Accordingly, under the rated output voltage, the machine speed can be extended to three rated speed with high continuity. Furthermore, some modes generate the rated output voltage with identical speed, which contributes to the high redundancy and high operating efficiency. Hence, with the multi-mode operation and the auxiliary of the PV power, the whole power generation system accommodates the higher flexibility, stability, reliability, and efficiency. [ABSTRACT FROM AUTHOR]

In this paper, a new asymmetric planar V-shaped magnet arrangement for a linear PM synchronous motor is proposed. Several magnet arrangements for the track of the proposed linear permanent magnet (PM) synchronous motor such as un-skewed magnets, conventional magnet skew, and V-shaped planar magnets have been investigated. The performance results of the linear motor with skewed magnets are compared to those of previously designed PM linear synchronous motor with conventional un-skewed rectangular-shaped (CuSRS) magnets. The forcer is kept the same for all track structures and a thorough comparison is provided for low detent force and low force ripple with the CuSRS and proposed planar V-shaped magnet skew approaches. [ABSTRACT FROM AUTHOR]

This paper presents the design and optimization procedure of a novel mechanical-offset complementary-stator flux-reversal (MOCS-FRPM) machine. First, based on the original topologies, the pole-pair and flux modulation pole optimizations contribute to the high power density, efficiency, and larger torque capacity for the machine design. Second, based on the 2-D optimization results, the 3-D mechanical-offset structures are adopted for the torque ripple suppression. In fact, compared with the 3-D non-offset machine, the rotor mechanical-offset topology possesses the better torque performance, which can decrease the torque ripple by 34.6%, and with a slight 6.4% reduction of the torque average. Thus, through the proposed optimization procedure, the new complementary-stator machine accommodates the merits of the large torque capacity, low torque ripple, high efficiency, and high reliability. Also, the artful incorporation of the 2-D and 3-D optimizations leads to the reduced computation time and higher optimization efficiency. [ABSTRACT FROM AUTHOR]

Selective recording on multiple structures may be possible with microwave-assisted magnetic recording. The number of parameters in even a dual-structure system is such that optimization is difficult. In this paper, the response surface methodology is used to systematically optimize a dual-structure system. Optimized structures are presented for three different recording configurations, allowing random writes to either structure or writing in a predetermined order. The addition of a second structure could allow areal densities of over 3 Tbit/in2 to be achieved. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive particle swarm optimization (APSO) based on a kernel support vector machine (KSVM). The proposed algorithm improves the convergence speed and exploration capability of the APSO by employing an individual adaptive parameter control based on the KSVM. To verify the algorithm’s effectiveness, it was compared with both the conventional PSO and APSO based on test functions. Finally, we applied the proposed algorithm to the optimal design of a synchronous reluctance motor (Syn-RM). [ABSTRACT FROM AUTHOR]

The optimal performance of 3-D planar metamaterial wideband devices is attained by maximizing their frequency bandgap. This, in turn, requires a design optimization procedure and iterative calculations of dispersion diagram points. To this aim, an efficient technique, blending a new mixed-order prism macroelement with an adjustable genetic algorithm (GA), is introduced in this paper for the rapid computation of dispersion diagrams. The developed scheme can launch diverse alternation orders along possible directions, whereas it is significantly more enhanced than existing approximations. In this way, the reduced degrees of freedom (DoF) facilitate the treatment of the derived eigenvalue problem and lead to a rigorous tool for the dispersion diagram of electromagnetic bandgap (EBG) structures, whose performance is intuitively optimized via the GA. For its validation, the featured method is thoroughly applied to diverse metamaterial multilayered setups with demanding geometric details and hard-to-model regions. [ABSTRACT FROM AUTHOR]

A novel electrodynamic suspension device using an asymmetrical double-sided Halbach array is proposed in this paper. A 3-D analytical model describing the eddy current field and the electromagnetic force is established via the second-order vector potential formulation. The validity of the analytical model is verified by both finite-element simulations and an experiment. The configuration of the proposed suspension device is optimized exploiting a dynamic kriging surrogate model assisted by a multi-objective genetic algorithm. The multi-objective optimization is performed utilizing the 3-D analytical model. [ABSTRACT FROM AUTHOR]

In this paper, a novel control method is proposed for superconducting-hybrid magnetic levitation systems applied in conveyor manufacturing facilities. Recently, magnetic levitation systems are variously researched not only for high-speed transportation but also manufacturing process requiring the dust-free condition. The proposed controller consists of the inner feedback compensator and set-point error controller. The structure of the controller with convex set between conventional proportional–derivative–integral controllers guarantees the performances and robustness of the conventional controller and makes it possible to consider the additional properties that can be converted into linear matrix inequality constraints. The control factors are determined by solving the optimization problem with linear matrix inequalities to be expressed for time-domain specifications such as overshoot, rise time, and settling time and control input bound. The effectiveness of the proposed controller is verified by the simulation and finite-element analysis. [ABSTRACT FROM AUTHOR]

In this paper, two novel double-sided hybrid-excitation flux-reversal linear motors (DSHEFRLM) with the surface (S-) and interior (I-) permanent-magnet(PM) arrangements are proposed and comparatively investigated. The proposed motors feature an asymmetrical double-sided primary configuration which enables the armature and field excitations to be placed separately. Through 2-D finite-element method (FEM), two motor structures with different slot/pole combinations are optimized, and then, the magnetic fields and electromagnetic performances are calculated, including inductances, no-load flux linkage, thrust characteristics, and PM demagnetization capability. By comparison, it is found that S-DSHEFRLMs show larger thrust density while I-DSHEFRLMs exhibit superior flux-adjusting capability. Finally, these predicted results are validated by 3-D FEM. [ABSTRACT FROM AUTHOR]

This paper proposes a multi-objective optimization method using an adaptive weight determination scheme and tunneling method. To find the optimum designs that are evenly distributed on the Pareto front, the weights of different objective functions are adaptively determined by using the concept of a hyperplane so that new solutions can be gradually found in the objective space. In addition, to avoid locally optimized solutions that are dominated by other Pareto optimum designs, a tunneling method is employed in the optimization process. To confirm the effectiveness of the proposed method, topology optimization of the magnetic actuator is performed. The magnetic force and volume of the actuator are considered as two conflicting objective functions in the optimization problem, and Pareto optimum solutions that are evenly distributed in the objective space could be obtained. [ABSTRACT FROM AUTHOR]

This paper presents the fast topology optimization methods for rotating machines based on deep learning. The cross-sectional image of electric motors and their performances obtained during a multi-objective topology optimization based on the finite-element method and genetic algorithm (GA) is used for training of the convolutional neural network (CNN). Two different approaches are proposed: 1) CNN trained by preliminary optimization with a small population for GA is used for the main optimization with a large population and 2) CNN is used for screening of torque performances in the optimization with respect to the motor efficiency. [ABSTRACT FROM AUTHOR]

This paper proposes dot sensitivity analysis of a current region for topology optimization. A continuum shape sensitivity formula is employed to derive a dot sensitivity formula in a simple closed form. The derived dot sensitivity formula provides the information on where the current dots should be created for topology optimization. This is necessary to generate the current dots in a vacant region of the design domain. Because this dot sensitivity analysis can obtain various topologies of material distribution, the possibility of local optimum convergence is reduced. Furthermore, because this dot sensitivity analysis does not require a specific initial design, its numerical implementation is simple. This dot sensitivity method is combined with the level set method to perform topology optimization. To demonstrate the usefulness of the proposed method, it is applied to two optimization problems of magnetic resonance imaging. [ABSTRACT FROM AUTHOR]

In this paper, a new permanent magnet (PM) linear motor is proposed. This motor has a special structure with complementary stator flux, which helps to reduce the flux leakage and improve the utilization of the PM. The PMs are installed in a leaning manner, which increases the effective area of the PMs and enhances the field excitation. Hence, the force density of the motor can be improved and it will be, especially suitable for applications within a limited space. The motor structure and working principle are first explained. The design of the motor is then comprehensively investigated. An electromagnetic optimization method based on tabu search algorithm and finite-element method is proposed for the motor to improve its force density. [ABSTRACT FROM AUTHOR]

The original fuzzy-based Taguchi method is restricted with the number of objective functions. Aiming to solve this problem, this paper describes an improved fuzzy-based Taguchi method (IFBTM) coupled with finite-element analysis (FEA) for the multi-objective optimization of direct-drive permanent magnet synchronous motors (DDPMSMs). To reduce the number of dimensions in the fuzzy rule base, the IFBTM uses a factor stratification method to establish multilayer fuzzy rule base. The fuzzy inference system with multilayer fuzzy rule base is introduced to translate the multiple optimization objectives to a single objective. After optimal selection analysis, the best combination of motor structure factors is obtained with small FEA computation. Finally, the performances of DDPMSM are analyzed and compared with those of IFBTM. The results certify the superiority and validity of IFBTM. [ABSTRACT FROM AUTHOR]

In this paper, we propose a hybrid genetic algorithm (GA) for the optimal shape design of an axially symmetric dual-reflector antenna by combining the GA with the moving least square (MLS), which enhances the convergence rate and the global search performance. The MLS is used to construct local interpolation functions from non-uniform sample data and to estimate new superior positions. By combining these superior positions in the next generation, the MLS-GA shows better search performance for the global optimum and a faster convergence rate than those of the conventional GA. To verify the proposed MLS-GA, we applied it to the optimal shape design of the DRA at the W-band. [ABSTRACT FROM AUTHOR]

Antenna array has been extensively applied to wireless communication systems. Optimal design of antenna array is very useful to attain desired spatial beam and reduce signal degradation. Potential search directions in artificial bee colony (ABC) algorithm are mixed with both large step size and small step size. This could lead to the malfunction of employed bee stage and onlooker bee stage of ABC algorithm. This paper proposes to improve the effectiveness of ABC by a similarity induced search method. This method adaptively adjusts search step size. Employed bees perform large step size search, while onlooker bees do small step size search. Scout bees could probe potential high-quality solutions in neighborhoods. The proposed algorithm is tested on antenna array design problem. Compared with four other algorithms, the results verify the effectiveness of the proposed algorithm. Furthermore, the scalability of the proposed algorithm is also analyzed in terms of array element and computational time. Scalability analysis also shows that the proposed algorithm is suitable for solving antenna array design problems. [ABSTRACT FROM AUTHOR]

Contactors are typical electromagnetic devices whose optimization is multi-objective optimization problems. Contactors’ static and dynamic characteristics obtained by the finite-element method (FEM) are typical objectives. Due to the low efficiency of FEM, the intelligent optimization algorithms that require multiple computations cannot be applied well here. In this paper, a fast algorithm for characteristics of contactors based on radial basis function neural network approximate model is proposed. The orthogonal least squares, data pre-processing and subsection modeling methods are adopted here to make the model more accurate. Meanwhile, a hybrid multi-objective optimization algorithm which combines the differential evolution and the particle swarm optimization is also proposed to speed up convergence and obtain the limit optimal solutions. The feasibility of the above-mentioned methods has been verified by solving a multi-objective optimization problem of the contactor with solenoid structure. [ABSTRACT FROM AUTHOR]

Multi-phase topology optimization (TO) is able to determine the optimal distribution of two or more different materials in combination under some volume or weight constraints and is a very common problem in the engineering design area. To perform multi-phase TO, a new methodology based on the multi-label graph cut theorem is proposed in this paper. More specifically, the multi-label expansion move included in the theorem is able to solve the multi-phase TO problem without requiring a large amount of memory and time. According to the numerical results as reported, the proposed methodology can find the optimal topology of a multi-phase materials distribution with a significant improvement in the performance parameter. [ABSTRACT FROM AUTHOR]

A new type of three-phase stator hybrid excited machine with permanent magnets (PMs) located at the slot openings of field winding slots is presented in this paper. It has the advantage of good flux regulation capability due to the field excitation. The machines with different stator/rotor pole combinations, i.e., 6-stator pole and 7-/8-/10-/11-/13-/14-rotor poles, have been comparatively investigated in terms of the open-circuit and on-load characteristics, as well as the influence of dc current and the unbalanced magnetic forces. The 2-D finite element analysis (FEA) has been employed for analysis and optimization of the machines together with experimental validation. [ABSTRACT FROM AUTHOR]

In this paper, we present the design and optimization of a ring-pair permanent magnet array for head imaging in a low-field portable magnetic resonance imaging (MRI) system. The proposed array generates a longitudinal main static magnetic field (${B}_{0}$ field) with an average field strength of 169.7 mT and a homogeneity of 24 786 ppm in a field of view with a diameter of 200 mm and a thickness of 50 mm. It is a significant increase in field homogeneity by 79.7% compared to a traditional ring-pair structure of the same dimension and mass while still maintaining a similar field strength. The optimization was implemented by applying a genetic algorithm and by proposing an efficient current model for the forward calculation of the magnetic field. The effectiveness of the optimization is validated by realistic simulations using COMSOL Multiphysics. Compared to a Halbach array, where the field is transversal and the existing coil designs cannot be applied directly, the proposed array generates stronger fields. Its magnetic field is longitudinal, which allows the direct application of the advancements in RF coil designs in a conventional MRI system to the imaging system using the proposed magnet array. [ABSTRACT FROM AUTHOR]

This paper presents a fast design optimization method in surface-mounted permanent magnet (PM) machines using an efficient analytical model. To predict the open-circuit magnetic field, an analytical model named Schwarz–Christoffel subdomain (SCSD) is proposed by applying the virtual rotor magnets and combining two elegant models, i.e., subdomain model and complex permeance model derived from Schwarz–Christoffel conformal mapping. Based on the developed SCSD model, electromagnetic (EM) performances such as cogging torque, back-electromotive force, EM torque, unbalanced magnetic force, and machine losses can be quickly obtained by reducing the computational complexity. Subsequently, the heuristic optimization is applied for selecting the best compromise between the conflicting objectives. Since the systematic optimization methodology is proposed by isolating the optimal shape and coil design procedures, the proposed optimization model combined with SCSD is significantly fast, robust, and efficient compared with existing models. The finite-element analysis is carried out to verify analytical results, and several Pareto fronts are provided along with the comparison of the time required by each model. [ABSTRACT FROM AUTHOR]

In this paper, a Halbach array-based nuclear magnetic resonance device for multiphase flow measurement is suggested. The design approach used simultaneously a 3-D finite-element method (FEM)-based software combined with particle swarm optimization algorithm. The goal of the design is to generate a relatively intense and highly homogenous magnetic field inside the target sensing area using a compact and lightweight magnet array. Simulation results on a device consisting of 12 Halbach arrays, each consisting of 12 cuboid permanent magnet elements of size 20 mm $\times20$ mm $\times46.5$ mm size, indicate that a highly homogenous magnetic field distribution of 0.890 T maximal intensity and 606 ppm homogeneity could be achieved within a probe cross section of 40 mm diameter when the Halbach arrays are distant from each other by a distance of 4 mm. This is adequate for the desired application while it leads to a light and compact overall Halbach array of 21.6 kg weight and 600 mm length. Experimental validation which was done using newly constructed two Halbach arrays of cuboid and trapezoid magnet elements, respectively, indicates a good match with FEM simulations. Furthermore, sensitivity analyses were performed to identify significant design variables for further optimization. [ABSTRACT FROM AUTHOR]

This paper deals with the optimization design process of an interior-type permanent magnet synchronous motor (IPMSM) for electric compressors of air conditioners applied to electric cars and hybrid vehicles. Based on a prototype IPMSM, we identified the current level for efficiency and cogging torque using finite-element analysis (FEA). The IPMSM’s main design variables are optimized to primarily satisfy the target of efficiency and cogging torque. A second optimization design is carried out using the response surface method (RSM) for the main design variables obtained from the Taguchi method analysis. As a result, the optimization design is carried out through a two-step optimization design process using the Taguchi method and RSM. The IPMSMs are analyzed using FEA, and their validity is confirmed by comparing the test results against each step-by-step model. We validate an effective optimization design process using a two-stage design process. We conclude that the proposed approach provides an effective design method for engineers. [ABSTRACT FROM AUTHOR]

Switched reluctance (SR) machines are attractive because they present relatively high efficiency and torque density in spite of lacking permanent magnets. This paper focuses on a two-objective optimization of an external rotor SR motor with a stator that has concentrated coils and a rotor with magnetically isolated modules. The objectives are minimum loss and mass, and 11 independent dimensionless geometric variables are considered as inputs that affect them. A combined design of experiments (DOE) and differential evolution (DE) approach is proposed. The DOE methodology is used to reduce the search space by eliminating from consideration input variable values, leading to poor-performing designs. Following this initial DOE study, an optimization study based on DE is run over the reduced search space, which leads to significant savings in computation time. Furthermore, a directed graph-based method for comparing different designs on the Pareto front to rank the best compromise designs is proposed. [ABSTRACT FROM AUTHOR]

Optimal design of electric machines using finite-element analysis (FEA) necessitates too much computation time to maintain high accuracy. To reduce the computation time and obtain a global optimum in multi-modal problems, this paper presents differing extent mesh adaptive direct search (DEMADS). The proposed algorithm is classified into three groups according to the poll searching frame and mesh size for assigning a global and local searching. In particular, DEMADS shares information among solutions based on a parallel multi-start strategy for earlier stopping by deviation and checking revisits. The effectiveness of DEMADS has been validated and evaluated as the function call number and the convergence number at a global optimum using benchmarking function. Finally, it is applied to an optimization problem that minimize torque ripple of a spoke-type permanent magnet synchronous machine via FEA. [ABSTRACT FROM AUTHOR]

A new flux-assisted consequent pole spoke-type permanent magnet (PM) synchronous torque motor is proposed in this paper. The proposed motor has fractional slot structure with a spoke-type rotor geometry and flux-assisted magnets. Initial design, rotor design optimization, detailed 2-D and 3-D finite-element analyses (FEAs), and structural and thermal simulations are all carried out. A prototype motor is built and tested. The optimized design is validated by 2-D/3-D FEA and experiments and compared with the reference conventional surface PM (SPM)-type torque motor. The results indicate that the proposed new motor has higher torque-to-magnet-weight ratio and wider constant power region than the conventional SPM synchronous torque motor. [ABSTRACT FROM AUTHOR]

In this paper, the optimization for the reduction of copper loss, iron loss, and permanent magnet (PM) eddy current loss considering harmonics is carried out to improve thermal performance. The effect in terms of thermal performance is confirmed through thermal analysis using a lumped-parameter thermal network (LPTN). First, the optimal shape is determined using an automatic optimization method that combines the explorative particle swarm optimization algorithm and finite element analysis. Then, the iron loss and PM eddy current loss considering carrier harmonics are recalculated by inputting the actual pulsewidth modulation current. Finally, an LPTN-based thermal analysis is performed with the calculated loss as the input. In particular, the thermal parameter is confirmed through an experimental method to validate the accuracy of the thermal analysis. The advantages over the conventional motor are clarified. [ABSTRACT FROM AUTHOR]

This paper presents an effective design method for inductors which is based on the multi-objective optimization accelerated by the artificial neural network (ANN). In the learning phase prior to the optimization phase, ANN is trained for 1000 input–output data sets obtained from the finite-element analysis for randomly generated dimensional parameters. The magnetic hysteresis of the ferrite core is modeled by the play model to evaluate the hysteresis losses. The multi-objective optimization problems are solved by the genetic algorithm in which the magnetic loss is effectively computed by the trained ANN to reduce the core volume as well as magnetic loss. The Pareto solutions for an EI-shaped ferrite core are obtained for different inductances. It is shown that the proposed method works much faster than the conventional optimization, and the magnetic loss and the inductance of the optimized inductor agree well with the experimental results. [ABSTRACT FROM AUTHOR]

High-speed permanent magnet synchronous machine (PMSM) can provide high power density and high efficiency, which is often highly desirable in high performance applications. A multi-physics optimization program based on the multi-objective genetic algorithm was developed in this paper, to achieve a tradeoff solution between the electromagnetic, mechanical, and thermal aspects. First, the parametric electromagnetic model was modeled based on the finite-element method, and then a thermal network model and an analytical mechanical model to determine the thickness of the magnet and the sleeve were developed and merged within a design cycle of the machine, in an effort to attain the target performances of 20 kW/kg at 20 000 r/min for a 2 MW PMSM. Optimization results indicated that a final design with eight poles and 48 slots could obtain a comprehensive performance between power density and efficiency, and the performance satisfied all the requirements. [ABSTRACT FROM AUTHOR]

This paper proposes a new double-stator magnetless vernier (DSMV) machine for direct-drive robotics. By artfully incorporating the double-stator structure, vernier configuration and dc excitation together, this DSMV machine yields the merits of the flux control capability, low-speed operation, high torque output, free maintenance, and high cost-effectiveness. Also, the optimizations of the rotor-teeth arc angle, stator-teeth arc angle, and current phase angle are carried out for the improvement of torque performance. In this way, the torque ripple of the machine is significantly reduced up to a tiny value of 3.67%. Moreover, the rational dc current range and the rotational speed range are obtained through the performance analysis with flux regulation. In addition, the comparison is performed with the conventional surface-mounted permanent-magnet machine. Therefore, the proposed machine shows the distinct features and is fit for the special application. Finally, both theoretical derivation and simulation are given for the validation of the machine design. [ABSTRACT FROM AUTHOR]