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Millimeter wave components, such as circulators and isolators, frequently use magnetic fields to break symmetry of the signal propagation and provide unidirectional signal transmission. While effective, these components have not seen the level of miniaturization of other millimeter wave components, primarily due to the discrete nature of the magnets used in the components. Using circulators in the 40-50 GHz range as a motivating application, requirements arise for the deposited films, namely immunity to eddy currents, sufficient magnetization to act as self-biasing magnets, and out-of-plane orientation of the self-biasing field. Based on these required properties, hexaferrite materials are selected for their strong magnetocrystalline anisotropy (MCA) and low conductance. The difficulty of integrating these components monolithically with monolithic microwave integrated circuits (MMIC) originates from the incompatibility of crystal structure with standard semiconductor materials and process conditions. Additive manufacturing using a composite of strontium hexaferrite (SrFe12O19) particles and photoresist has been chosen as a method to overcome the difficulties of integrating hexaferrite material to semiconductor substrates. Due to their large internal anisotropy field, the particles of strontium hexaferrite tend to rotate to the field direction instead of changing magnetization direction under application of an external magnetic field (less than the anisotropy field). We have developed a method for 3D printing composites of high strontium hexaferrite concentration (up to 20% by volume) in a liquid photoresist, SU8. Rotation of hexaferrite particles in polymer matrix and thus magnetic anisotropy has been demonstrated in the composite, which is subsequently cured to hold the physical position and orientation of the particles. The anisotropy of the self-biasing field provided by the films has been experimentally characterized, and a ferromagnetic resonance (FMR) frequency ~43 GHz has been observed. We have also characterized the viscosity of the particle-laden polymer at different particle concentrations. 3D printing of this composite with poling will make it possible to directly print magnetic components that require out-of-plane anisotropic magnetization.

With the continuous development of artillery, the disadvantages of hydraulic recoil brakes gradually appear. At the same time, the appearance of high-performance NdFeB permanent magnet makes it possible to apply electromagnetic braking technology to recoil mechanism. In this paper, prototype tests of a certain artillery were carried out to verify the feasibility of the electromagnetic brake (EMB) and obtain the electromagnetic braking force. Due to the brittleness of NdFeB, in order to eliminate the worry about the safety of EMB, SHPB experiments of NdFeB were carried out. Then, based on the assumption of uniform crack distribution, the law of crack propagation and damage accumulation was described theoretically, and the damage constitutive model suitable for brittle materials was proposed by combining the Zhu-Wang-Tang (ZWT) equation. Finally, the numerical simulation model of the artillery prototype was established and through calculation, the dynamic mechanical characteristics of NdFeB in the prototype were analyzed. The calculation results show that the strength of NdFeB can meet the requirements of the use in the working process. From the perspective of damage factor, the damage value of the permanent magnet on the far right is larger, and the damage value of the inner ring gradually decreases to the outer ring.

To improve the coercivity and temperature stability of Nd-Fe-B sintered magnets for high-temperature applications, the eutectic Tb80Fe20 (wt%) alloy powders were intergranular added into the Nd-Fe-B sintered magnets to enhance the coercivity (Hcj) and thermal stability. The microstructure, magnetic properties and thermal stability of the Nd-Fe-B magnets with different Tb80Fe20 contents were studied. The experimental results demonstrate that the coercivity (Hcj) of the sintered Nd-Fe-B magnet is significantly enhanced to 27.78 kOe from 14.12 kOe, and the remanence (Br) decreases not obviously by introducing 4 wt% Tb80Fe20 alloy. Meanwhile, the reversible temperature coefficients of coercivity (β) and remanence (α) of the Nd-Fe-B magnets are increased from −0.5634%/°C to −0.4506%/°C and −0.1276%/°C to −0.1199%/°C at 20–170 °C, respectively. The Curie temperature (TC) of the Nd-Fe-B magnet is slightly enhanced with the increase of Tb80Fe20 content. Moreover, the irreversible flux magnetic loss (hirr) is obviously reduced as Tb80Fe20 addition. Further analysis of the microstructure revealed that a modified microstructure, i.e. clear and continuous RE-rich grain boundary layer, is acquired in the sintered magnets by introducing Tb80Fe20 alloy. The associated mechanisms on improved coercivity and thermal stability are comprehensively researched.

In this paper a novel Radial-Axial (RA) Flux Switching Permanent Magnet Generator (FSPMG) is introduced. In contrast to other RA flux machines, a major advantage of this generator is its implementation only by the use of conventional Non-Oriented Electrical Steel Sheets (NOESSs), even though the flux linkage of the novel RA-FSPMG has a three-dimensional (3D) path. Besides that, it benefits from the flux concentration strategy and a passive rotor. A concrete foundation of the novel RA-FSPMG is provided, in which, the 3D-Flux path is described, working principles are discussed, and power-sizing equation is derived. No-load (NL) characteristics and the Full Load (FL) performance of an optimized RA-FSPMG are investigated in contrast to an optimized Double Stator Radial (DSR) FSPMG and an optimized Double Stator Axial (DSA) FSPMG with similar volume, number of Permanent Magnets (PMs), and electrical loading. The results show the competitiveness of the novel RA-FSPMG, in particular, in the output power and the required copper mass. Furthermore, the PM demagnetization possibility and the rotor axial pull force of the optimized RA-FSPMG are investigated, in detail. All discussions are supported by the 3D Finite Element Analysis (3D-FEA) and experimental results.

In this study, the influence of the content of Al and Co in the diffusion source on the magnetic performance and microstructure of the diffused magnet was discussed by grain boundary diffusion treatment with Pr70Al30–xCox (x=0 at%, 10 at%, 15 at%, 20 at%, 30 at%) alloys. When the Co content in the diffusion source increases from 0 at% to 10 at%, the coercivity enhancement in the Pr70Al20Co10 diffused magnet is the highest, increased from 1.62 to 2.24 T, higher than 2.01 T of the Pr70Al30 diffused magnet. With the further increase of Co content in the diffused source, the coercivity of the diffused magnet decreases gradually, the coercivity of Pr70Al15Co15, Pr70Al20Co10 and Pr70Co30 diffused magnet is 2.15, 1.99 and 1.81 T, respectively. Microstructural analysis shows that plenty of continuous grain boundary phases (CGBPs) can be formed in the Pr70Al20Co10 diffused magnet under the synergistic effect of Al and Co, which leads to the enhancement of magnetic isolation between more adjacent grains. However, the amount of CGBP in the diffused magnets gradually decreases with the further increase of Co content in the diffusion source.

This paper presents a new interior permanent magnet (IPM) rotor structure/ assembly which inherits from the Halbach magnet configuration and spoke-type IPM rotor to achieve a high saliency ratio and high torque/power density. A higher air-gap flux density and a higher saliency ratio are expected to improve torque density, while the rotor inner diameter can be maximized as much as possible to reduce core material consumption and increase internal space of the rotor. Accordingly, the electromagnetic performance of three motors consists of a unified stator but three different rotors, namely flux-concentrating rotor, Halbach array PM rotor and spoke-type IPM rotor is compared by finite element analysis (FEA). Due to the segmented structure of flux-concentrating PM rotor without magnetic bridges, the mechanical challenges are analyzed in detail for electric vehicle application. The stress analysis on the prototype design with fixing pins to hold the pole pieces validates the structural feasibility at 7200 r/min. Finally, a 72-slot/ 16-pole fractional-slot PM motor with new flux-concentrating rotor is manufactured and tested to verify its performance and feasibility. It can be concluded that the new rotor is superior to the spoke-type IPM and Halbach array PM rotor in terms of torque density and PM utilization.

To explore the feasibility of deep grain-size refinement in overcoming the problem of traditional Br-Hci trade-off in bulk permanent magnets, the effect of deformation temperature on the texture strength, grain refining, and magnetic properties of slow-deformed Nd-Fe-B magnets were systematically studied. As a result, strong textures with gradual grain refining from conventionally large size of DL=650 nm to small nanoscale size of DL=53 nm (DL denotes the lateral size of the aligned plate-like grains) are observed as the temperature reduces from Td=650 oC to Td=450 oC. Moreover, magnetic observations show a simultaneous increase in remanence and coercivity as the grain refines from DL=650 nm to DL=127 nm. The increase in coercivity results from the grain size refinement as well as the smaller aspect ratio of the plate-like grains, and the increase in remanence results from the improved texture homogeneity. As compared with the DL=650 nm magnets, the simultaneous increase in remanence and coercivity leads to optimum enhancements of 57% in coercivity, 10% in remanence, and 25% in energy product, which demonstrate the feasibility of near-nanoscale grain refinement in overcoming the traditional Br-Hci trade-off for improved (BH)max values. The failure of higher coercivities in the DL≤80 nm magnets is closely related with the defect effects of the grain boundaries. Mechanisms explaining the grain refining and texture changing behavior were also discussed.

Traditional multi-point hybrid maglev systems cannot realize the zero-power horizontal levitation state under eccentric load, which means the steady-state current is zero, and the air gap of each magnet is equal. This paper proposes a new maglev system with two rotary magnets to solve this problem. The two magnets can move on an annular guideway to counteract the moment caused by the eccentric load. At first, we established the linear parameter varying model of this maglev system. Then the control strategy is designed, which consists of a zero-power horizontal levitation controller and rotation controller. The levitation control is realized by introducing feedback of integral current and deviation of air gap in the proportional-derivative control system. The rotation controller employs a centroid observer and centroid Jacobian. It outputs the rotating angle at the demand of the zero-power and horizontal levitation. Experimental results demonstrate that the proposed maglev system has a better zero power and horizontal levitation performance than without rotary magnets. The direction of the air gap variation is opposite to that of the loading direction. The variation size of air gap length depends on the load weight, while rotation angle is related to the load weight and loading position.

This paper presents design studies on a rotor for the high-speed homopolar type permanent magnet motor that can be applied to super chargers for automobiles, cordless stick vacuum cleaners and so forth. A stator consists of a core and a permanent magnet. The rotor is composed of only a core, thus allowing removal of a retaining ring on the surface. In order to realize the maximum torque and power required from a target application under a constraint of core stack length, design studies based on three-dimensional finite element analysis are conducted. The design validation is confirmed through experimental tests using a prototype.

This paper presents and evaluates a dual rotor axial flux permanent magnet motor for electric aircraft applications. Several features, including grain oriented electrical steel (GOES), magnet segmentation, and wires with rectangular cross-sections, are used to improve torque density and efficiency. Rather than simply optimizing the motor by itself, this paper evaluates the tradeoffs between motor performance and its interfaces with the drive, thermal management system (TMS), and mechanical structure. This information can be used along with similar analyses of the drive, TMS, and structure to select a design that achieves the system-level optimal performance. The paper uses finite element simulations to characterize tradeoffs between active mass, efficiency, fundamental frequency, power factor, axial forces on the rotors, and cooling surface area. Several designs exceed 95% efficiency at takeoff with less than 8 kg of active mass. While high pole counts, a large outer radius, and short stator teeth tend to optimize the magnetic performance at takeoff, this can reduce cruise efficiency, reduce the surface area through which the TMS can extract heat, increase the fundamental frequency the drive must supply, and increase the structural mass required to support the rotors. Additionally, designs with 20 °C cooler magnets were simulated to evaluate the impact of a more effective TMS, but the improvements in magnetic performance were relatively small.

Magnetic positioning approach (MPA) is a reliable solution for automated guided vehicles (AGVs) under relatively fixed route conditions. Ferrite magnets are usually buried in the ground and employed as magnetic nails (MNs) for the parking and steering of AGVs. Our previous studies implemented a novel MPA based on super-strong NdFeB magnets and the minimize iterations between magnetometer data and predicted values via the magnetic dipole model, with the advantage of more exceptional positioning performance than traditional MPAs. Nevertheless, the iterative optimization algorithms depend on the initial guess setting; besides, the complicated calculation based on multiple magnetometer data makes it difficult to be executed on a microcontroller in real-time. In this article, we propose a simplified MPA based on the analytical method. The analytical expression for calculating the two-dimensional position of an MN is derived from the magnetic dipole model. Even a single tri-axis magnetometer can localize the MN, whereas multiple magnetometers tend to achieve higher positioning performance. Thus, positioning results of multiple magnetometers are fused based on the confidence criterion. Comparing with the MPA based on the Levenberg–Marquardt algorithm, the proposed MPA could achieve comparable positioning accuracy but with far lower computational complexity and greater robustness. Thereby, this article introduces a new concept of high-precision MPA for AGV applications without the complicated visual perception.

Microstructure and magnetic properties were studied for the commercial Sm(CoFeCuZr)z magnets before and after post annealing treatment. The results show that the phases composition and orientation of the magnet do not change after post annealing treatment, but the substantial redistribution of Cu element within multiscale (the microscale crystal grain and the nanoscale cellular structure) had been observed simultaneously. In detail, as the Cu redistribution, the thickness of the Cu-rich Sm(Co,Cu)5 cell boundary becomes thinner, and the Cu concentration in the boundary increases sharply. The pinning field of domain walls and corresponding coercivity increases remarkably with slight remanence and maximum energy product loss, and the overall magnetic performance of (BH)max (MGOe)+Hcj (kOe) increases by 54.3% as a result. Moreover, the thermal stability of the magnet improves as well. On the other hand, Cu-lean phenomenon was observed along the grain boundary region, triggering to magnetic domain reversal process and slightly undermining the squareness of the demagnetization curve of the magnet.

The as-solution-treated Sm2Co17-type magnets exhibiting a single 1:7H phase with different average grain sizes (D) are designed. Anisotropy of bending strength (Rbb) and compressive strength (Rmc) of the magnets was investigated. Moreover, the Rbb increases from 86 to 173 MPa with D decreasing from ∼52 to ∼18 μm for group c//h samples. The Hall-Petch correlation was employed to reveal the effect of grain size on mechanical properties of the magnets, giving deep understand the mechanical anisotropy characteristics. The relatively high Hall-Petch coefficient KRbb (0.79 MPa·m1/2) gives rise to the largest Rbb (173MPa) for group c//h samples. The mechanical anisotropy of the samples is well explained based on crystal structure and grain size features (grain boundaries). Grain refinement is an effective way to enhance the mechanical properties of Sm2Co17-type sintered magnets.

An increasing interest for permanent magnet synchronous machines with low torque ripple and low vibration is observed. The purpose of this paper is to investigate the topology of non-uniformly distributed teeth and its influence of on cogging torque, tooth ripple harmonics and torque ripple of permanent magnet synchronous machines. The topologies with different number of non-uniformly distributed teeth are investigated. Analytical procedure is developed to illustrate the impacts of non-uniformly distributed teeth on cogging torque and unbalanced magnetic pull (UMP), and then identify the appropriate non-uniformly distributed teeth. A commercial 10kW 8-pole 48-slot V-shaped IPM machine is taken as the reference base machine. The machines with 2- and 6 non-uniformly distributed teeth are chosen to make an overall comparison to that with the well-known skewing slots. The machine with 2 non-uniformly distributed teeth is finally chosen to be fabricated. Intensive experiments including cogging torque, back-EMF, load current, efficiency and instantaneous torque are done.

Permanent magnet synchronous motors (PMSMs) with non-concentric magnetic poles (NCMP) structure are widely used as high-precision servo motors. The current subdomain method mainly equates the NCMP to a rectangular magnet to make each subdomain boundaries of magnet parallel when calculating the magnet eddy current loss (ECL), which results in a lower accuracy of the calculation. This paper divides the NCMP into non-concentric region and concentric region along the radial direction. The non-concentric region is further divided along the circumferential direction, and each divided region has a single thickness. Based on the subdomain method, a novel analytical method of magnet ECL in PMSMs with NCMPs is proposed. Moreover, the 3-D distribution coefficient of ECL in the NCMP is derived by the equivalent impedance method. The effects of eddy current reaction and stator slotting are taken into account to improve the calculation accuracy. Then, through theoretical derivation, the relationship between the minimum magnet loss and the pole parameters is obtained, which provides a reference for the design of NCMPs. Finally, the loss separation experiment is performed on four prototypes with NCMPs. The experimental results, finite element method results and analytical results are compared to verify the correctness of the model.

Low cost and high abundance rare earth elements Y and Ce have attracted tremendous interests of the industrial and scientific societies for fabricating the highly cost-performance efficient rare earth permanent magnets. However, the effect of separate replacement of Nd by Y or Ce on the performances of NdFeB-type magnet under the same atomic ratio and preparation conditions is still unclear. In this work, we systematically investigated the magnetic properties, thermal stabilities and service performances of (Nd0.8Y0.2)13.80FebalAl0.24Cu0.1B6.04 (at%, 20Y) and (Nd0.8Ce0.2)13.80FebalAl0.24Cu0.1B6.04 (at%, 20Ce) magnets. The results demonstrate that the μ0Mr, μ0Hc and (BH)max of 20Y magnet are respectively 1.325 T, 1.173 T and 343.467 kJ/m3, which are comprehensively higher than those of 20Ce magnet (μ0Mr = 1.310 T, μ0Hc = 0.948 T, (BH)max = 321.105 kJ/m3). Moreover, the 20Y magnet has higher thermal stability compared with 20Ce magnet which is favorable for the magnetic performances at elevated temperatures. The investigation of microstructure and elemental distribution indicates that the excellent magnetic performances of NdY-Fe-B magnet can be attributed not only to the preferable intrinsic properties 4πMs, Ha and Tc of Y2Fe14B, but also to the in-situ core-shell structure of the 2:14:1 matrix phase grain with Y-rich core and Nd-rich shell, along with the thicker grain boundary layer between the adjacent matrix phase grains in NdY-Fe-B magnet. Furthermore, the 20Y magnet exhibits better mechanical property and higher corrosion resistance than 20Ce magnet, which are helpful for prolonging the service life of the magnet in practical application.

This paper reveals the flux leakage design and modeling principle of a flux leakage controllable permanent magnet (FLC-PM) machine by considering driving cycles. The key is to obtain the relationship between flux leakage characteristics and multiple operating conditions. Based on the flux leakage controllable concept, an FLC-PM machine with an artfully designed flux leakage region is proposed. The design principle of the machine is investigated by analyzing the magnetic circuit of the machine in multiple operating conditions. The flux leakage factor is introduced to characterize the variable magnetic field in multiple operating conditions. On this basis, the mathematical model of the FLC-PM machine is deduced, and the driving characteristics of the machine are studied in detail. In order to evaluate the presented principle of the FLC-PM machine, a prototype is manufactured for experiments. Through the theoretical analysis and experimental testing, it is verified that the proposed principle is feasible and effective.

The hollow-cup Permanent Magnet (PM) motors have the characteristics of low power consumption, and are widely used in the aerospace field. At present, the tile-shaped PMs used by hollow-cup PM motors have poor sinusoidal characteristics of the air gap magnetic flux density waveform, which will cause torque ripple. The existing method for improving the air gap magnetic flux density waveform is not very effective when applied to hollow cup, a special motor with no stator core and large air gap. A bow-shaped PMs structure is designed for the hollow-cup motor in this paper. First, the equivalent surface current method is used to calculate the analytical formula of the static magnetic field of the model. Then, the Finite Element (FE) method is used to calculate the static air gap flux density waveform of conventional tile-shaped PMs and bow-shaped PMs with different bow heights, and the corresponding harmonics and sine distortion are obtained by Fourier decomposition. The simulation results show that the bow-shaped PMs can effectively improve the sinusoidal characteristics of the static air gap flux density waveform. And the suitable bow height is determined. Finally, a prototype is made based on the suitable bow height for experiments, and compared with the analytical result and the FE result, and the accuracy and effectiveness of the bow-shaped PMs with the suitable bow height are verified.

In this paper, a method of simultaneous sensorless rotor position and torque estimation is proposed for interior permanent magnet synchronous machines at standstill and low speed. The proposed method estimates the torque using high frequency inductances identified from the current variations due to high frequency square wave voltage injections in the estimated dq-axeswhich are simultaneously used for sensorless rotor position estimation. The proposed method is not dependent on the fundamental model and has taken the cross-coupling effect into consideration, allowing for low cost and fast torque estimation at standstill and low speed. Both simulations and experiments are carried out to verify the effectiveness of the proposed method.

The Shortening of the Right hemibody (SRH) is a phenomenon that occurs in Medicinal Biomagnetism (MB), a technique developed by Isaac Goiz Durán from the 80’s. This method makes use of the static magnetic field (SMF) generated by a negative magnet applied to the skin in a dysfunctional anatomical region, out of its physiological balance, tending to alkalinity, which leads to the consequent contraction of the muscles of the right hemibody (RH). The elongation of the hemibody or muscle relaxation occurs when the point that receives the influence of the SMF is dysfunctional towards acidity caused by physiological imbalance. The shortening or elongation of the RH is a reflex called magnet-foot reflex, magnet-sympathetic-foot reflex or Goiz Reflex (GR). The objective of this study was to carry out a narrative review in order to demonstrate the importance of RH for the technique, identifying the neuromuscular response mechanism that leads to the contraction or relaxation of the musculature. It was concluded that the GR is the main tool for energy diagnosis, confirmation and treatment of Biomagnetic Pairs (BMP). Its neuromuscular mechanism, similar to strength tests (a form of applied kinesiology), possibly results from the activation of different brain regions: cerebral amygdala, frontal and parietal lobes and areas corresponding to those stimulated with the SMF, promoting a reflex that, like the withdrawal reflex, is unconscious and qualifies the response in a binary way (stimulated area positively or negatively polarized). Its accuracy may be subject to interference from the information or semantic field of the therapist and the patient. The RH is more susceptible to manifest the GR which could occur on both sides.The GR concept was revisited over the years of MB development, a new science in constant evolution, and despite being a tool whose use and effectiveness have practical evidence, it is necessary to produce scientific evidence that proves its neuromuscular mechanism.

U okviru diplomskog rada povedena je optimizacija dizajna sinkronog motora s izmjenjivim magnetskim tokom u aksijalnoj izvedbi. Opisan je princip rada motora te su definirani zahtjevi kako bi se motor mogao koristiti za pogon električnog bicikla. Definiran je pojednostavljeni dvodimenzionalni model ekvivalentnog linearnog motora te je provedena parametrizacija. Za provedbu optimizacije dizajna motora definirani su ulazi, ciljevi i ograničenja na ulazne parametre. Pomoću elektromagnetskog izračuna dvodimenzionalnom metodom konačnih elemenata provedena je optimizacija gustoće snage stroja. Napravljena je verifikacija dobivenih parametara i karakteristika optimalnog motora pomoću trodimenzionalne metode konačnih elemenata. Kratko je analizirana upotreba feritniih magneta umjesto neodimijskih u optimalnom dizajnu stroja. Dane su preporuke za izradu prototipa motora. As part of the thesis, the design optimization of the axial flux variant of the flux switching synchronous motor was presented. The principle operation of the motor is described and the requirements are defined so that the motor can drive an electric bicycle. A simplified two-dimensional model of an equivalent linear motor was defined and parameterization was elaborated. To implement motor design optimization, inputs, goals and constraints on input parameters are defined. Using electromagnetic two-dimensional finite element method power density of the motor was optimized. The obtained parameters and characteristics of the optimal engine were verified using the three-dimensional finite element method. The use of ferrite magnets instead of neodymium magnets in the optimal design of the machine is briefly analyzed. Recommendations are given for the prototype motor.

A prototype of a type A quadrupole magnet has been designed and manufactured for the 3 GeV storage ring of Siam Photon Source II, the second synchrotron light source in Thailand. The required quadrupole gradient is 51 T/m with the magnet effective length being 162 mm. Magnet modeling and magnetic field calculation were performed using Radia and Opera-3D. The bore radius of the magnet is 16 mm. The magnet will be operated at the excitation of 5544 A-turns. A mechanical analysis of the magnet structure was performed in SOLIDWORKS and ANSYS, where the maximum deformation of 0.003 mm was found at the magnet poles, and the first-mode natural frequency was higher than 100 Hz. The magnet yoke is made of AISI 1006 low-carbon steel with a fabrication tolerance of ±0.020 mm. Magnet coils are water-cooled and made of high-purity copper. The temperature rise of the coils was below 3.0 °C at the maximum excitation of 6664 A-turns, which is 20% above the operating point. Magnetic field measurement was carried out using the Hall probe technique. The measured magnetic field and coil temperature of the prototype show good agreement with the calculations.

Halbach arrays are the most efficient closed structures for generating directed magnetic fields and gradients, and are widely used in various electric machines. We utilized fused deposition modelin...

In this work, a reverse saliency (RS) spoke-type permanent magnet (PM) synchronous motor (PMSM) besides its hybrid adaptive notch filter (HANF) based self-sensing for driving a solar photovoltaic water pump system (WPS) is presented. The conventional spoke-PMSM driven WPS experiences two types of problems. Firstly, the motor is operated with a flux-weakening current to produce positive reluctance torque, thereby increasing the PM demagnetization risk. Secondly, an encoder is used to sense the rotor angle, which in turn affects the cost and reliability. To solve the first problem, the RS-PMSM is presented, which operates with a flux-intensifying current to produce positive reluctance torque. While second issue is resolved by using the HANF based rotor angle estimation. Although conventional methods give an estimate of rotor angle, they do not eliminate both the DC-offset and dominant harmonics. The superiority of both the RS-PMSM and HANF over existing solutions, is shown respectively by using finite-element methods and MATLAB/ Simulink based performances. Besides, a prototype motor is also manufactured. The performance of RS-PMSM prototype along with its HANF based self-sensing is obtained in the laboratory and various test results are reported. Meanwhile, a comparison of the HANF with available self-sensing techniques, is also performed.

This paper has proposed a novel design of dual PM vernier machine with T-shape consequent pole rotor. The analytical model of T-shape magnet rotor based on differential magnetic network method are firstly derived. Given the additional optimizing parameter, edge arc difference, T-shape consequent pole (TCP) rotor has the potential to produce 6% higher fundamental airgap flux density or 30% higher PM utilization ratio than regular fan-shape consequent pole rotor. The influence of magnet size parameters including magnet thickness, pole pitch ratio and arc difference angle on airgap flux density of TCP rotor is then analyzed. The torque performance of TCP in regular consequent pole and dual PM consequent pole vernier machines are also studied. The comparison shows that T-shape consequent pole can produce higher torque than fan-shape magnet in vernier machines. At last, a prototype of dual-PM vernier machine with TCP rotor is built and tested, which has achieved 28 Nm/L measured torque density.

Homopolar inductor machine (HIM) has caught much attention in the field of flywheel energy storage system (FESS) due to its merits of robust rotor, brushless exciting, high reliability, etc. Compared with permanent magnet HIM (HIM-PM), the HIM with field winding (HIM-FW) can effectively eliminate the idling loss caused by the no-load magnetic field by cutting off the excitation current, while the charge/discharge efficiency of HIM would be decreased due to the copper loss of field winding. To address this contradiction, a novel PM HIM with mechanical flux modulator (HIM-MFM) is proposed to achieve low idling loss and high charge/discharge efficiency. Firstly, the special structure and operation principle of the HIM-MFM are investigated. Afterwards, the characteristic of equivalent magnetic circuit of the HIM-MFM is analyzed and several key structure parameters of it are optimized. Moreover, the electromagnetic performance indexes of the HIM-MFM, including back-EMF, flux weakening ability, losses, etc. are fully analyzed. Finally, a prototype of the HIM-MFM is designed, manufactured, and tested. Experiment results confirm those obtained by simulations. Results show that the proposed HIM-MFM inherits the merits of high charge/discharge efficiency of HIM-PM and almost no idling electromagnetic loss of HIM-FW.

A generalized fault-tolerant control (FTC) strategy for the field-oriented control (FOC) and direct torque control (DTC) of five-phase fault-tolerant permanent magnet (FPFTPM) motors under various open-circuit faults is presented in this paper. Most previous studies regarding FTC target a specific primary control algorithm and involve different reduced-order transformation matrices and additional current controllers, which increase the complexity of the entire drive system. In this study, a solution to the aforementioned problems is devised by developing optimal fault-tolerant voltages, which are derived from fault-tolerant mechanism analysis and steady-healthy design. Because the coordinate transformation need not be changed and additional voltage compensation is not required, a minimal control drive system reconfiguration under various open-circuit faults can be achieved to avoid accommodating the change of the primary control algorithm. The proposed control strategy not only improves the torque performance and dynamic response under healthy and fault conditions but also adapts to both FOC and DTC. Experimental results for a 2 kW FPFTPM motor prototype are provided to evaluate the proposed strategy.

This paper investigates the eddy current loss mechanism of a dual permanent-magnet-excited machines (DPMM). Based on the flux modulation effect, abundant harmonics are induced in the air gap of DPMM. The harmonics of air-gap flux density due to rotor PMs, stator PMs, and armature reaction are investigated qualitatively and separately. Then, the orders, frequency, and rotation speed of the harmonics are deduced theoretically. The harmonics that contribute to the eddy current losses are deduced accordingly. Finally, the loss distribution of the proposed DPMM is estimated through simulation and the thermal field of the proposed motor is analyzed. A prototype is fabricated to validate the analysis. Temperature rise of both stator and rotor PMs under rated load condition is measured through experiment.

コロナ禍で，子どもの家庭内での生活時間が長くなるに伴い，子どもの誤嚥・誤飲のリスクが増加している．異物を飲んでしまった場合に，異物確認のためレントゲン撮影を行う．その際，医療者は異物や素材ごとにレントゲンで描出されるか否か，背景知識として持っておく必要がある．本研究では，子どもの誤嚥・誤飲のハイリスクとなる43 種類の物品についてレントゲン透過性を確認した．また透過性の可否により放射線画像で判読可能なもの，判読しにくいもの，判読不可能なものに分類した．本研究の限界としては，生体内に取り込まれた物品のレントゲンとは撮影条件が異なるため，物品個体の画像と必ずしも同じ読影結果が得られるとは限らない．時に，内視鏡的摘出術や開腹手術など侵襲性の高い処置を与する場合や死亡例もある．そのような事故を防ぐためにも，乳幼児の近くに小さなものを置かないことが第一の予防である．, With the global outbreak of coronaviruses, children are spending more time in the home. As a result, the number of accidents in which children swallow foreign objects has been increasing. When a child swallows a foreign body, the pediatrician performs an x-ray to check for the presence of a foreign body in the body. We investigated X-rays of items that are frequently swallowed by children. In this study, radiographic permeability was confirmed for 43 types of items that are at high risk for aspiration and accidental ingestion by children. According to permeability, the items were classified into three groups：radiographically legible, illegible, and illegible. The limitation of this study is that it is an x-ray image of an object only. Therefore, the x-ray images do not match those of an object swallowed by a child’s body. In some cases, endoscopic or laparotomy surgery is required to remove the foreign object. There have also been deaths caused by foreign objects. To prevent sad accidents, the primary prevention is to avoid placing small objects near infants.

This study presents a computationally efficient model predictive torque control (MPTC) method for permanent magnet synchronous machines (PMSMs). The existing MPTC methods require solving complex optimization problems in iterations; this approach is computationally demanding. In contrast, the proposed MPTC transforms the optimization problem into two subproblems and derives the corresponding solutions explicitly using numerical techniques, which entail linearization of the torque function and current constraint; the proposed approach can significantly reduce the computational burden. Additionally, the proposed MPTC does not involve any control gains and weighting factors; hence, gain tuning is not required for the proposed MPTC. These features are advantageous when implementing torque control. Using a 4-kW PMSM drive, the effectiveness of the proposed MPTC is demonstrated both numerically and experimentally in terms of dynamic performance and computational efficiency. This is realized by comparing the proposed method with the existing methods.

The recent development of tough tissue adhesives has stimulated intense interests among material scientists and medical doctors. However, these adhesives have seldom been tested in clinically demanding surgeries. Here we demonstrate adhesive anastomosis in organ transplantation. Anastomosis is commonly conducted by dense sutures and takes a long time, during which all the vessels are occluded. Prolonged occlusion may damage organs and even cause death. We formulate a tough, biocompatible, bioabsorbable adhesive that can sustain tissue tension and pressurized flow. We expose the endothelial surface of vessels onto a gasket, press two endothelial surfaces to the adhesive using a pair of magnetic rings, and reopen the bloodstream immediately. The time for adhesive anastomosis is shortened compared to the time for sutured anastomosis. We have achieved adhesive anastomosis of a great vein in transplanting the liver of a pig. After the surgery, the adhesive is absorbed, the vein heals, and the pig lives for over one month.

A novel cage-secondary permanent magnet linear eddy current brake (ECB) with wide speed range and its analytical model are presented in this paper. Differ from the existed permanent magnet ECB, the proposed ECB owns the variable parameters cage-secondary structure. This unique secondary structure can keep braking force at a large constant value from high speed to low speed by changing the secondary parameters in different speed ranges. First, both the structure and working principle of the proposed ECB are given. Then, a new analytical model combined with multilayer theory is proposed, where the saturation of secondary iron teeth and the end effect are considered. Based on the magnetic field distribution result, the characteristics of proposed eddy current brake are analyzed. Third, the accuracy and validity of the analysis results are verified by the finite element method and prototype experiments. Moreover, based on the genetic algorithm, the optimal secondary parameters are obtained with the objective of maximum braking force at each speed.

This paper presents the design and control of a new Halbach-array-based two-phase motor (HTM) with a 3-D printed coil mount and magnet housing for precision motion control applications. The motor is based on a 2-pole Halbach cylinder that generates a uniform magnetic field within its inner diameter. Each pole has 10 magnet segments. This uniform field simplifies the Lorentz force calculation based on the volume integration. In addition, it allows for the real-time measurement of the rotor position based on Hall-effect sensors. Compared with conventional stepper motors and iron-core DC motors, this motor design can produce a continuous torque and precise positioning at any angular position without a cogging torque. In this paper the design of the motor together with its dynamics and control are presented. The design uses only one type of square-cross-section magnets that are readily available, making it easy to scale the design to a variety of sizes and torque capabilities. The 3-D printed stator and rotor housings allow for the motor to be constructed at a low cost in a short time. With a total magnet volume of only 30.7 cm3, a total effective coil volume of only 10.4 cm3, and a maximum current of 4 A, the maximum torque generated is 0.044 Nm. Experimental results with closed-loop control on a simple empirically-identified plant model are provided to validate the magnetic design of the motor. The feedback signals are from two Hall-effect sensors connected to a microcontroller, offering a theoretical angular resolution of 0.16. A minimum step size of 0.32 is demonstrated in positioning with closed-loop control. The motor has the capacity to track the commanded motion and speed with an error less than 0.64.

this paper proposes a ferrofluid soft capsule robot (FSCR) with magnetic actuation for diagnostic and therapeutic medical applications inside the human stomach. A composite shell consisted of ferrofluid, permanent magnet rings and soft elastomer is developed for the FSCR, which is actuated remotely by an external permanent magnet. The proposed FSCR presents two novel characteristics. First, the composite shell not only has soft outer surface that reduces damage to contact tissue, but also an improved magnetic circuit with a combination of the ferrofluid and permanent magnet rings makes the locomotion of the device more controllable and security. Second, the FSCR is equipped with a specific oscillation module that enables advanced functions such as drug releasing. Detailed structure design and fabrication of the FSCR are presented in this study. The surface rolling locomotion of the FSCR is modeled and evaluated by numerical simulations, as well as the drug releasing function. In order to verify the simulation result, a FSCR prototype is manufactured to perform experimental validation. The analysis result demonstrates the feasibility and efficiency of the proposed FSCR for drug releasing inside a printed human stomach model.

It is known that permanent magnet vernier machine has multiple flux field harmonics which can produce stable torque. However, some flux field harmonics would create torque that undermines the torque output. Such as the 6slots26poles split-tooth PMVM here, of which modulated flux field outputs torque while fundamental flux field undermines torque output. In this paper, a 26poles PMVM with coding-shaped tooth is proposed. The coding-shaped tooth can introduce permeance harmonics with specific phase and amplitude, thus modulating flux fields that all output torque. Air-gap permeance harmonics of the proposed and the regular split-tooth PMVM are obtained via FEA. Based on MMF-permeance model, flux fields of two machines and their contributions to average torque are investigated, proving that the proposed machine has multiple flux fields that all output torque. By optimizing geometry of coding-shaped tooth, the proposed machine obtains largest average torque and smallest torque ripple simultaneously. Electromagnetic performances of the optimized machines are studied in semi-analytical way and FEA. It is proved that with same overall size, PM usage and copper loss, the proposed machine achieves 30% larger torque density, 86% smaller cogging torque and 62% lower torque ripple than its counterpart. Finally, a 16Nm (rated)prototype is built and tested.

A modified configuration for Permanent Magnet Assisted Synchronous Reluctance Motors (PMaSyRM) is studied in this paper. Conventionally, the PM materials are inserted in the flux barriers region of the rotor. Consequently, the PMs sizing parameters will be restricted to the available space that may limit the efficient use of PMs benefits. In this study, a portion of the rotor structure is replaced with an Interior PM (IPM) rotor so that an axially segmented integration of IPM and SyRM is obtained. Thus, the PMs design is performed specifically in the IPM segment independent of the SyRM scheme, while the SyRM segment remains PM-less. The main motivation of this concept is to improve the contribution of the PM material in the total torque as well as utilizing the special property of the proposed rotor configuration for pulsating torque reduction. A computationally cost-effective algorithm is proposed for the optimal design of IPM-SyRM motor by which a low-power design is carried out for a lightweight electric vehicle. The results for torque profile characteristics, PM volume, power-factor, and efficiency are compared with a conventional PMaSyRM that has been optimally designed as the reference case. Finally, a prototype is constructed to verify the theoretical analysis.

In this article, the fault-tolerant control (FTC) strategy based on current redistribution is compared for three types of triple redundant 3×3-phase motor: surface-mounted permanent magnet synchronous motor (SPMSM), synchronous reluctance motor (SynRM), and permanent magnet assisted synchronous reluctance motor (PMa-SynRM), under a single-phase open-circuit fault. The output torque of SPMSM and SynRM is produced by permanent magnet (PM) torque and reluctance torque, respectively. Nevertheless, for PMa-SynRM, it is necessary to determine the distribution ratio of PM torque and reluctance torque in the proposed FTC strategy. By comparing the FTC performance of motors, the conclusions are as follows: (1) Torque ripple of the SPMSM can be completely suppressed. (2) Torque ripple minimization for the SynRM and PMa-SynRM can be realized. (3) Optimal solution obtained in SynRM can also be applied to the PMa-SynRM when the load is heavy. In addition, to reduce the complexity and improve the reliability of the control system, a mono-inverter driven triple paralleled control system is constructed in healthy and postfault operations. The comparison results of the FTC strategy for three types of motor are obtained by simulation. And the experimental results based on a 3×3-phase PMa-SynRM are accomplished to verify the feasibility of the theory.

This paper investigates the air-gap field distribution of the permanent-magnet vernier machine (PMVM) using nonlinear exact conformal model (NECM) to account for slotting effect, flux modulation effect and iron nonlinearity. The exact conformal model based on the region of one-slot and one-flux-modulation-pole (OSECM) are introduced to show the effectiveness of linear analytical model for PMVM. It can keep high calculation accuracy and significantly reduce the computational burden. Then, the NECM is developed from OSECM by introducing the equivalent saturation current into the air region and coil region. The lumped parameter magnetic circuit model (LPMCM) model is used to obtain the magnetic potential of iron region and therefore calculate the equivalent saturation current. The NECM which combines LPMCM and OSECM can essentially improve the accuracy of linear analytical model. The harmonic analysis of air-gap field is performed to theoretically explain the component of electromagnetic torque. Both finite element model (FEM) simulation and test results are presented to validate the NECM.

A fault-tolerant hybrid current control is proposed for dual 3-phase permanent magnet synchronous machines (PMSMs) with one phase open in this paper. The maximum torque control, minimum copper loss control, and single 3-phase mode control are unified in the proposed method, which is a combination of single 3-phase mode control and maximum torque control with different percentages. When the percentage of single 3-phase mode control (k) varies from 0% to 100%, the hybrid current control transitions from maximum torque control (k=0%), to minimum copper loss control (k=50%), and then to single 3-phase mode (k=100%). Therefore, the hybrid current control can be switched among the aforementioned three control methods easily and smoothly. Meanwhile, it can be a mixed-mode with a tradeoff between the maximum torque control and minimum copper loss control, such as the minimum copper loss control for a given torque within the full torque range, which can be achieved by changing k. The smoothness of transition among the maximum torque control, minimum copper loss control, and single 3-phase mode control is verified by experimental results on a prototype machine.

This paper proposes an improved analytical model for fractional-slot concentrated-winding (FSCW) spoke-type permanent magnet (STPM) machines, where the impact of slotting on magnetomotive force (MMF) is elaborately considered. Firstly, the deficiency of the existing MMF-permeance model using Carters coefficient is discussed. It is found that adopting Carters coefficient will cause considerable prediction errors in flux density, especially for machines with a small equivalent airgap and considerable PM-MMF fluctuation. Secondly, an improved analytical model is proposed based on the relative permeance function and a simplified magnetic circuit model (MCM). The proposed model enables to predict common electromagnetic performance, such as PM flux density and back electromotive force (EMF) with more accuracy. Moreover, the radial forces exerted on the stator teeth can be predicted precisely as well, which is conducive to further vibration analysis. Both the experimental and finite element analysis (FEA) results indicate that the proposed model can enhance the characterization capability of slotting effect and improve performance prediction accuracy.

This paper proposes a novel approach to the modelling of HTS transformer-rectifier flux pumps that can charge HTS magnet-ic loads without the need for bulky current leads or expensive cryogenic requirements. The model was built in MATLAB/Simulink for a flux pump with 2 HTS switches, an HTS transformer with a primary inductance of 15 mH, second-ary inductance of 50 H and an HTS magnetic load with an in-ductance of 2 mH. With a 5 A pk-pk triangular current wave-form at 2 Hz the system can load the HTS load to 34.63 A in 5 s. This incremental addition of flux to the load demonstrates the advantage of flux pumps as they can charge high-field magnets without the need for large power sources. The speed of flux pumping is improved by increasing the system frequency, the magnitude of the dynamic voltage developed in the HTS switches and by increasing the primary inductance of the trans-former. This has widespread industrial applicability in fields such as the charging of high-field magnets for MRI systems.

The three-dimensional (3-D) finite element (FE) analysis is an extremely time-consuming task in the design and optimization of axial flux permanent magnet (AFPM) machines. The aim of this paper is to present a fast and accurate design model of slotless AFPM machines. Thanks to the separation of active- and end-winding parts, the overhang structure, which has widely been used in the air gap winding, can be handled by the proposed method. The winding eddy current loss, a primary source of losses in the air core structure, is incorporated into the analytical model. In addition to the high accuracy, this approach makes it possible to evaluate machine performances only once without needing to rotate the rotor position. As a result, the proposed analytical model can significantly reduce the computational time, preferred in applying an optimization algorithm. Finally, the accuracy of the proposed method is verified by both FE and experimental results.

in order to enhance motor torque performance of existing two-phase 8/10 E-Core SRM, an improved modular permanent magnet (PM)-assisted Switched Reluctance Motor (SRM) structure is presented. Firstly, basic structure and operation principle of the proposed structure are introduced. To further evaluate performance improvement, effects of various parameters on the design such as inductance, flux-linkage, average torque and cogging torque are compressively investigated by finite element method (FEM) software subsequently. In the meantime, comparisons with other two-phase SRM structures are also performed including average torque, torque/PM volume, torque/ motor volume, torque/current, etc. Finally, a prototype is fabricated, and simulation and experimental results verify that the proposed design has high torque performance.

This paper presents a novel magnetic-geared direct-drive machine (MGDM) with V-shaped permanent magnets (PMs) installed on its rotor. By extending the inner rotor shaft and connecting it to a prime motor, the torque and power density of the proposed MGDM is boosted. Additionally, compared with the conventional MGDM with surface-mounted PMs, the proposed MGDM with V-shaped PMs has a more robust rotor structure to cope with extreme operating conditions. The operating principle and structure requirement of this MGDM are first derived. Then, the geometrical parameters are optimized via a three-stage multi-objective optimization method to maximize output torque and efficiency and minimize torque ripple via the genetic algorithm and finite element analysis (FEA) combined optimization strategy. Furthermore, the proposed MGDM is artfully integrated into hybrid electric ships (HESs) to construct an onboard integrated power system (OB-IPS). Since the proposed system possesses various operating modes to cope with practical operating conditions, it enjoys a high systematic efficiency and good dynamic performance. Finally, a prototype is fabricated and tested with various operating modes by referring to the practical navigation cycle of a HES. The experimental results validate the feasibility of the proposed MGDM for being applied in HESs.

As a new type of flux modulation machine, line-start permanent magnet vernier machine (LSPMVM) has drawn more and more attention. Thanks to the rotor starting winding, the self-starting capability of which can be acquired without applying the inverters. As a result, the system reliability has been improved and cost can be decreased, which is promising for industrial applications, such as pumps and fans. In order to extend the family of LSPMVMs and select the preferable topologies meeting the different requirements, four LSPMVMs, including V-shaped LSPMVM, consequent-pole U-shaped LSPMVM, dual-stator spoke LSPMVM and consequent-pole surface-mounted permanent magnet (SPM) LSPMVM, have been proposed in this paper. And the steady state performance, starting and synchronization capability are comprehensively analyzed and compared, where the regular commercial line-start permanent magnet synchronous machine (LSPMSM) is used as a counterpart. It is found that all the proposed LSPMVMs can acquire the higher torque density. Especially, the V-shaped LSPMVM and consequent-pole U-shaped LSPMVM have the highest torque density, while the consequent-pole SPM LSPMVM can be a better candidate where the low cost is desirable. Finally, the prototype of V-shaped LSPMVM has been manufactured, where experimental results match well with finite element analysis (FEA).