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The presented experimental method enables the study of the dynamics of a domain wall (DW) moving in bistable microwire in a region of rapidly changing magnetic field. DW velocity versus DW position dependence is obtained in this experiment. Measurements were carried out on Fe77.5Si15B7.5 microwire with strong unidirectional effect in DW propagation. The propagating DW is forced to change its parameters in a very short time, which results in the velocity increasing above its equilibrium value after the DW passes the region of rapid increase in magnetic field. In order to interpret the observed experimental behavior, a simple theoretical model was proposed. Comparison of experimental and model dependences produced a high value of DW inertial mass, indicating that the DW area was much larger than the cross-sectional area of the microwire. Another interesting conclusion was that a DW with stronger damping (shorter wall) does not have a lower value of inertial mass. [ABSTRACT FROM AUTHOR]

This article presents a novel displacement detection method with sensing coils weakly coupled with a conventional eight-pole active magnetic bearing. To improve integration, the sensing coils are completely wound on the magnetic poles of the active magnetic bearing. The proposed method is different from others since each sensing coil is wound around two teeth of an active magnetic bearing, reducing the mutual inductance coefficient between sensing and excitation coils. Thus, the influence of excitation coils on displacement detection can be reduced. A core multiplexing and frequency discrimination method is proposed to detect displacements along ${x}$ - and ${y}$ -directions, simultaneously. Experiment results show that sensitivity along the ${x}$ - and ${y}$ -axes are 8.98 and 5.61 mV/ $\mu \text{m}$ , respectively, showing the feasibility of displacement detection without being affected by displacement variation of the orthogonal axis. Finally, the displacement detected by sensing coils is used for close loop control in an active magnetic bearing system at 2500 rpm, validating the feasibility of sensing coils in active magnetic bearing control. [ABSTRACT FROM AUTHOR]

In this study, a novel design of multiperiod bipolar inductive absolute angle sensor is proposed. The sensor structure is composed of stator and rotor. An inner and outer fan-shaped bipolar pattern is designed and fabricated on the rotor. The receiving coils and signal processing circuits are on the stator. When alternating current is applied to the excitation coil, the eddy current is generated in the rotor. The induced voltage of two adjacent receiving coils is in the form of cosine, when the rotor rotates above the receiving coil. There are two groups of receiving coils in the sensor. One group is composed of eight loops, corresponding to the 45° fan-shaped pattern at the outer edge, and the other group is composed of two loops, corresponding to the 180° fan-shaped (semicircular) pattern at the center. The coil with more loops provides high measurement accuracy and the coil with a small number of loops provides the identification of the number of cycles. The results show that the measurement error is 0.04° and the resolution is better than 0.005° in the range of 0°–360°. Through the multiperiod bipolar pattern proposed in this article, a high accuracy absolute position measurement can be realized. [ABSTRACT FROM AUTHOR]

This article presents a decentralized formation control strategy for electromagnetic formation flight (EMFF). A primary control challenge of EMFF is the coupling that occurs between the electromagnetic fields generated by all satellites. Alternating magnetic field forces (AMFF) are used to address these coupling challenges. Each satellite’s electromagnetic actuation system is driven by a sum of amplitude-modulated sinusoids, where the amplitudes are optimally designed to prescribe the average intersatellite force between each satellite pair while minimizing control effort. The communication structure is a connected undirected graph, where each satellite relies on relative-position and relative-velocity feedback of neighboring satellites. The controller is designed based on an average dynamic model, which is used to provide necessary and sufficient conditions for formation control. [ABSTRACT FROM AUTHOR]

Electric Vehicles are increasingly common, with inductive chargepads being considered a convenient and efficient means of charging electric vehicles. However, drivers are typically poor at aligning the vehicle to the necessary accuracy for efficient inductive charging, making the automated alignment of the two charging plates desirable. In parallel to the electrification of the vehicular fleet, automated parking systems that make use of surround-view camera systems are becoming increasingly popular. In this work, we propose a system based on the surround-view camera architecture to detect, localize, and automatically align the vehicle with the inductive chargepad. The visual design of the chargepads is not standardized and not necessarily known beforehand. Therefore, a system that relies on offline training will fail in some situations. Thus, we propose a self-supervised online learning method that leverages the driver’s actions when manually aligning the vehicle with the chargepad and combine it with weak supervision from semantic segmentation and depth to learn a classifier to auto-annotate the chargepad in the video for further training. In this way, when faced with a previously unseen chargepad, the driver needs only manually align the vehicle a single time. As the chargepad is flat on the ground, it is not easy to detect it from a distance. Thus, we propose using a Visual SLAM pipeline to learn landmarks relative to the chargepad to enable alignment from a greater range. We demonstrate the working system on an automated vehicle as illustrated in the video https://youtu.be/%5fcLCmkW4UYo. To encourage further research, we will share a chargepad dataset used in this work (an initial version of the dataset is shared https://drive.google.com/drive/folders/1KeLFIqOnhU2CGsD0vbiN9UqKmBSyHERd here). [ABSTRACT FROM AUTHOR]

Wireless Power Transfer (WPT) is a promising technology applied in the intelligent transportation infrastructure. This technology can charge electric vehicles dynamically through resonant inductive coupling. The application of WPT is of significance to vehicle-road collaboration. This paper focused on the impact of pavement infrastructure material magnetization on resonant inductive coupling. Here, the experimental analysis was conducted with a Series-Series topological WPT system. Six kinds of pavement materials, including AC-5, AC-13, SMA-5, SMA-13, OGFC-13, and Portland Cement Concrete, were employed as the transfer medium in the shape of rutting plate specimens. The active power and efficiency were recorded by monitoring the voltages and currents on both primary and secondary sides. The experimental analysis revealed the pavement materials changed the active power and efficiency by inductance enhancement and coupling reduction in resonant inductive coupling whose formulae were modified by two influencing factors: the inductance enhancement factor and coupling reduction factor. The influencing factors were varied by pavement materials’ magnetization properties. The influencing factors are useful for adjusting the WPT system’s component parameters to offset the magnetization impact. Moreover, water immersing was considered an environmental impact in the experiments, showing a reduction in the active power and efficiency. The waterproof between pavement layers is also necessary. [ABSTRACT FROM AUTHOR]

The saving and re-use of energy has acquired great relevance in recent years, being of great importance in the automotive sector. In the literature, it is possible to find different proposals for energy-harvesting damper systems (EHSA)—the electromagnetic damper being a highly recurrent but still poorly defined proposal. This article specifically focuses on studying the concept and feasibility of an electromagnetic suspension system that is capable of recovering energy, using a damper formed by permanent magnets and a system of coils that collect the electromotive force generated by the variation of the magnetic field. To study the feasibility of the system, it is necessary to know the maximum energy that can be recovered through the winding system; however, the difficulties in obtaining the derivative of the magnetic flux and its derivative for each position make the analytical method very tedious. This paper presents an experimental method with which to maximize energy recovery by defining the optimum relative position between magnet and coil. [ABSTRACT FROM AUTHOR]

A high-density symmetrical transformer based on through-silicon via (TSV) is proposed in this article. The primary winding and secondary winding have strong symmetry, and the inductance mismatch is less than 0.1%, so the transformer structure is suitable for differential circuit. Compared with transformers in other literatures, the proposed transformer has advantages in area and efficiency, which is reflected in that the on-chip area is greatly reduced by 58% to 89%, and the coupling coefficient can reach more than 0.92. [ABSTRACT FROM AUTHOR]

This article proposes an asymmetric magnetic coupler using the horizontal magnetic field to realize the conformal and lightweight unmanned aerial vehicle (UAV) side pickup mechanism and solve the problems of rotation misalignment and horizontal offset of UAVs. The novel structure uses multiple groups of series circular coils as the transmitting coil to construct a uniform near harness horizontal magnetic field. The solenoid structure covered with flexible magnetic material is used as the receiver, which is attached to the UAV landing gear. A 200-W prototype is produced to validate the proposed structure. The system can maintain smooth mutual inductance with a dc–dc efficiency of 90% under a ±20 mm offset and free-rotation. [ABSTRACT FROM AUTHOR]

This article proposes an absolute-type inductive angle sensor for detecting the position of the YRT turntable bearing. The sensor comprises a multispeed incremental measuring unit and a single-speed absolute measuring unit sharing the same stator, rotor, and excitation circuit. The stator is composed of a ferromagnetic gear groove, two groups of excitation coils, and one group of induction coils arranged according to certain rules. The end cover of the YRT turntable bearing is machined as rotor and it rotated eccentrically relative to the rotation of the stator. A bridge circuit is used to acquire and process the sensor signal from the single-speed measuring unit. Compared with the traditional dual-channel absolute measurement, the proposed measurement method avoids the effects of different magnetic circuit disturbances on signal quality and measurement accuracy, and has more advantages in the volume and weight of the sensor. The structure and working principles of the sensor are presented in detail, the feasibility of sensing scheme is verified via simulation, and a sensor prototype is designed for the final experiment. Experimental results show that the accuracy of the sensor prototype is –0.06758° to 0.1203° before compensation and –0.001139° to 0.0015° after compensation in the range of [0°, 360°], respectively. [ABSTRACT FROM AUTHOR]

The article proposes an adaptive robust controller with synchronization compensation for the Maglev wind turbine yaw system to achieve stable nacelle suspension and pitching suppression. First, two-degree-of-freedom suspension model is constructed with consideration of magnetic coupling and pitching interference, and then deduces a two-terminal suspension control model based on the inverse system. Second, a nominal suspension controller is designed based on the composite error; and then an adaptive synchronization controller is proposed to adjust coupling parameters based on reconstructed synchronous function; an adaptive tracking controller is used to online update dominant control input parameters. The robust controller is to compensate for the influence of the approximation errors during the parameters convergence process. It is proved that the proposed strategy can guarantee the globally uniformly ultimately bounded of all signals, and suspension tracking error and synchronization error can converge to the desired smaller neighborhood of zero. Finally, simulation and experimental results show that the system with the proposed strategy has the faster dynamic response, smaller steady error and synchronization error, and stronger robustness than other two strategies. [ABSTRACT FROM AUTHOR]

Background Pelvic congestion syndrome is defined as intermittent or constant pain that persists for at least 3–6 months, is localized in the abdomen or pelvis, is not associated with pregnancy, is not limited to any period of menstrual cycle or intercourse, and is severe enough to cause functional disability or require treatment. This condition has been recognized as a potential cause of chronic pelvic pain (CPP) in women of childbearing age. The aim of this study was to detect the efficacy of embolization of ovarian veins by assessing the adequacy of closure of incompetent pelvic veins and abolishment of venous reflux in the addressed ovarian veins. Patients and methods A single-center prospective study was conducted on 14 women of childbearing age complaining of CPP associated with dysmenorrhea, dyspareunia, and\or vulvar varicosity, lower limb pain. All patients underwent lower limb venous duplex as well as pelvis duplex to assess the presence of dilated and refluxing ovarian vein more than 6 mm in diameter. Gynecological causes of pelvic pain were excluded; all patients underwent venography in an angiosuite to confirm the diagnosis of dilated ovarian vein and presence of parametrial varicosities. Embolization of ovarian vein and associated pelvic veins was done using foam sclerotherapy with polidocanol and coiling of the ovarian vein with coils ranging from 8 to 12 mm in diameter. Results In our study, there was a statistically significant improvement in symptoms in our patients after coiling during the follow-up compared with before coiling, including CPP (P=0.002), lower limb pain (P=0.003), dyspareunia (P=0.003), and dysmenorrhea (P=0.002). Conclusion The embolization of ovarian vein is feasible, safe, and effective with high rates of success and clinical improvement in the treatment of pelvic congestion syndrome. [ABSTRACT FROM AUTHOR]

The additional complexity of Class EF and Class $\boldsymbol{\Phi }$ inverters compared with their Class E counterparts, combined with parasitic effects becoming more prevalent as frequency and power levels increase, results in poor accuracy from traditional design methods, and usually additional iterations of manual retuning are required. Furthermore, after making these additional iterations, it is practically impossible to ensure that all the desired design conditions are met in hardware, due to the number of degrees of freedom in these circuits. In this work, we propose an approach to simulating and tuning Class EF/ $\boldsymbol{\Phi }$ inverters, with various levels of accuracy depending on the level of knowledge of the system parasitics. Our method is composed of a combination of analytic and numerical solving methods, thus providing both insight on the progression of the algorithm and computational robustness. The aim of our algorithm formulation is to enable solutions to be found in an automated and fast way. The novelty in our work lies in the design method’s concurrent capability to provide a generalized set of design inputs (e.g., dc to ac current gain, arbitrary drain voltage slope at turn on, $\boldsymbol{\Phi }$ -branch resonance, etc.), inclusion of board and device nonlinear parasitics, and the ability to design within the set of preferred component values. An example is shown for the design of a 50-W, 13.56-MHz inverter where the experimental setup approaches the theoretical efficiency of 97%, whilst maintaining all of the other design requirements. The algorithm changes the values of the components over 5%–50% and improves the simulated waveform accuracy by 2–12 times compared with the design method based on first-order approximations. [ABSTRACT FROM AUTHOR]

This article proposes and implements an optimized omnidirectional wireless power transfer (WPT) system using distributed transmitter coils. Under the consideration of practical WPT applications which involve human safety concerns, such as daily home apparatus or wireless rechargeable medical implants, the proposed system can achieve the shortest charging time within the safe limits of human exposure to radiofrequency electromagnetic energy. Based on the calculation of the magnetic intensity generated by multicoupling WPT systems, a more processable magnetic threshold model is presented and analyzed based on the common standard. A newly developed optimization model of the transmitter currents and accordant control strategy is designed and presented to realize both maximum power tracking and flux suppression at target positions. The double-resonant circuit topology with LCC compensation is adopted to reach the stable and synchronized transmitter currents. The cross-coupling problem in multiinput WPT systems will be solved as well. Full-range magnitude control is realized with a single controller and direct current (dc) power supply. The hybrid frequency pacing technique is adopted for lower switching frequency and higher system efficiency under weak coupling operations. Taking practical wireless rechargeable medical implant as the research object, both simulation and experimental results validate the feasibility and the prospect of the proposed system. [ABSTRACT FROM AUTHOR]

State-of-the-art capacitor online monitoring methods are designed for the whole dc bank. The capacitance or equivalent series resistance of the dc bank, as an aging indicator, is obtained by the sensors installed at the dc terminal, or derived from the state equation of the system. The difference of capacitor parameters from manufacturing and the arrangement of the dc bank will result in uneven thermal stress for the capacitors. Due to the restriction of the low stray inductance specification and high power density requirement, the traditional online monitoring circuits are hard to be designed for the single capacitor in the dc bank. In this article, a Rogowski coil based online monitoring circuit has been designed for the single capacitor in the dc bank. A new aging criterion has been established for aluminum electrolytic capacitors based on the accelerated aging test. To achieve a compact integration design, a six-layer printed-circuit-board-type Rogowski coil is designed under an optimized frequency. A 2-kW single-phase inverter is built to verify the theoretical analysis and practical performance of the monitoring circuit. [ABSTRACT FROM AUTHOR]

The flexible induction cooktop, which can provide an unlimited cooking area, utilizes a cost-effective method in which one inverter shares multiple working coils. However, this method has resulted in consumer needs such as reducing both the initial pot detection time and the noise caused by the relay operation. This article presents a hardware implementation and control method for a flexible induction cooktop with multiple GaN-HEMT-based inverter systems. As one way to meet consumer needs, this implementation method does not require a relay and offers the advantage of real-time pot detection and noise minimization. However, the inverter design should include the magnetic coupling effect while maintaining high performance and high power density. This article proposes an inverter design method considering the limited space and an implementation method that minimizes the effect of magnetic coupling without an additional power stage. The feasibility of the proposed implementation method is evaluated based on the results of a heating test with a 3.3 kW prototype. [ABSTRACT FROM AUTHOR]

The double-sided inductor capacitor capacitor topology has been proposed in some national standards for wireless charging systems. However, misalignment between the transmitting and receiving coils usually leads to detuning and weak coupling, resulting in low output power and inefficiency. To improve power output under weak coupling, this article proposes a control method based on the variable inductor and capacitor (VLC). First, it is deduced that the zero phase angle input and full output power can be achieved by VLC regulation under certain misalignment. Second, the variable inductor using an EE-shaped core and pulsewidth modulation controlled capacitor are applied to achieve VLC regulation, and the principles and implementation of VLC are analyzed. Third, as the coupling coefficient k can be identified through the primary electrical parameters, a convenient and accurate coupling coefficient identification method is utilized to help VLC regulation. Finally, a prototype with a 3.3 kW output power and an 87.5% maximum system efficiency (dc–dc) is built to validate the proposed method. The experimental results are consistent with the theoretical analysis, proving that the output power is almost constant when k varies from 0.08 to 0.18. [ABSTRACT FROM AUTHOR]

The single-switch topologies, e.g., the Class E topology, have the advantages of low component count, no shoot-through problem, simple driving circuit, which make it more suitable for high frequency low/medium-power wireless power transfer (WPT) applications. However, due to the high switch voltage stress, narrow soft switching range, bulky input choke, or ac inductor, its power delivery capability and applications are limited. In order to solve these problems, this article proposed a novel active clamp topology for high cost-performance medium-power WPT systems. The proposed topology offers low component count with no bulky inductor and low switch voltage stress, leading to high power-density, low cost, and compact size, i.e., high cost-performance for WPT applications. And the switch peak voltage can be adjusted and the soft switching operation can be achieved in a wide load range by designing the compensation capacitor and clamp capacitor. In this article, the detailed theoretical analysis and parameter design are discussed and the proposed topology is compared with the existing single-switch topology in terms of voltage stress, cost, and component count. A 120 W and 1 MHz active clamp WPT system is built and a 92.4% system efficiency is achieved with high cost-performance, which validate the feasibility of the proposed topology and the theoretical analysis. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) is a promising way of charging electric vehicles (EVs) for its convenience, safety, physical and electric isolation. For satisfying the high-power application or rapid charging, WPT systems based on multiple coils are usually used. Nowadays, LCC compensation is a commonly used topology. However, the conflict between the installation space limitation and the large volume induced by compensated inductors and multiple coils brings the critical challenge for EVs charging electric vehicles' charging. In this article, a method of integrating multiple decoupled coils is put forward. All the main coils and compensated inductors are integrated together for compacting the WPT system. Characteristics of the coupler are analyzed when it exists a misalignment both in x- direction and y-direction. Besides, an antimisalignment strategy based on optimizing the phase difference of current in main coils is proposed. Finally, a 3kW laboratory prototype is built to verify the proposed compact coupler and antimisalignment control strategy. The system output power only drops 3.2% and 9.2% respectively with a −200 mm and +200 mm misalignment in the x-direction compared with full alignment by adopting the proposed antimisalignment method. When it is fully aligned, the system can achieve 94%peak efficiency. [ABSTRACT FROM AUTHOR]

In-pipeline inspection is an important precontrol method to ensure the safety of oil and gas pipeline transportation. This article proposes an electromagnetic in-pipe detector based on passive resonance-enhanced differential planar coils to detect defects on the inner surface of pipes. Both qualitative and quantitative analyses of pipeline defects and damage are developed. The introduction of passive resonant coils is shown to significantly improve the detection capability of the sensor. This is coupled with the establishment of a theoretical derivation model of the proposed structure. The hardware platform of the laboratory system has been built, and an eddy current internal detector suitable for 8-in-diameter pipes is developed and integrated into the system. Numerical simulations and experimental verifications on flat defects and pipe defects have been undertaken. The obtained results have shown that the real defects have been correctly detected, and the system is effective, reliable, and efficient. [ABSTRACT FROM AUTHOR]

Magnetic tracking is useful in many motion tracking applications and free from the line-of-sight (occlusion) limitations that is the drawback of many popular optical tracking systems. Previously, multiaxis magnetic markers relied on time multiplex or frequency multiplex methods to separately sense inductor–capacitor (LC) coils in different axes, which introduce bandwidth or speed limitations. In this article, we propose a novel data-driven magnetic tracking approach whose markers are based on multiple LC coils in the same resonance frequency. Our approach utilizes deep learning to determine the complex flux distribution of monofrequency multiaxis magnetic markers where simulation results are the training data. Classic numerical methods struggle to achieve the same process. With this approach, we build a new magnetic tracking system that pursues multiaxis passive markers and overcomes the original tracking principle’s dead-angle limitation. With the flexibility of deep learning, we can design markers with more than three axes. Our experimental result also shows that compared to classic three-axis markers, more LC coils in different axes actually improve the tracking accuracy. Our approach not only helps build a new tracking system based on a wireless magnetic tracking principle, but can also be applied in any multiaxis magnetic tracking system. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging requires spatial uniformity of the radiofrequency (RF) field inside the subject for maximum signal-to-noise ratio and image contrast. Bulky high permittivity dielectric pads (HPDPs) focus magnetic fields into the region of interest (ROI) and increase RF field uniformity when placed between the patient and RF coils in the MR scanner. Metamaterials could replace HPDPs and reduce system bulkiness, but those in the literature often require a complicated fabrication process and cannot conform to patient body shape. Proposed is a flexible metamaterial for brain imaging made with a scalable fabrication process using conductive paint and a plastic laminate substrate. The effects of single and double-sided placement of the metamaterial around a human head phantom were investigated in a 3 T scanner. When two metamaterial sheets were wrapped around a head phantom (double-sided placement), the total average signal in the resulting image increased by 10.14% compared to placing a single metamaterial sheet underneath the phantom (single-sided placement). The difference between the maximum and minimum signal intensity values decreased by 57% in six different ROIs with double-sided placement compared to single-sided placement. [ABSTRACT FROM AUTHOR]

Minimally invasive thermal ablation procedures of tumors with implanted devices are very promising, especially for the repetitive treatment of deep-seated tumors. The implanted devices are heated without contact by an alternating magnetic field from outside the patient’s body. In this paper, the heating power of millimeter-sized implanted coils is analyzed and optimized with a numerical-analytic analysis and the dependencies on spatial, electrical, and magnetic parameters are evaluated and presented for being able to choose the optimum implanted coil for a specific set of parameters. The analysis is done with focus on the implanted coils based on a homogeneous alternating magnetic field. A heating power of 1.5 W required for achieving an adequate rise of tissue temperature is determined in a thermal analysis and the corresponding specific absorption rate (SAR) is evaluated along with the power transfer efficiency (PTE) and the coupling coefficient for different types of implanted coils. For uncompensated implanted coils, a SAR of 306 mW/kg, a PTE of $\mathrm {4.62\cdot 10^{-3}}$ and a coupling coefficient of $\mathrm {2.49\cdot 10^{-3}}$ is achieved by a magnetic field strength of 1727 A/m, whereas a SAR of 1.84 mW/kg, a PTE of $\mathrm {436\cdot 10^{-3}}$ and a coupling coefficient of $\mathrm {2.3\cdot 10^{-3}}$ is achieved by a magnetic field strength of 134 A/m for serial compensated implanted coils. With this, the ratio of heating power to required magnetic field strength is maximized, which reduces the risk of unwanted heating of healthy tissue and other implanted devices and therefore enhances the safety as well as the well-being of the patients.

Despite an increasing interest in wearable wireless power transmission (WPT), until now, wearable antennas have been unable to simultaneously harvest from near-field resonant and far-field radiative WPT. Here, a dual-port antenna is proposed, integrating an inductive coil with a broadband monopole for near- and far-field wearable WPT. The coil acts simultaneously as a High Frequency (HF) near-field power receiver and an Ultra-High Frequency (UHF) resonator, enabling the miniaturization of the enclosed broadband monopole, both fabricated using all-textile conductors. On-body, the antenna maintains a 10 dB return loss over a measured 135% fractional bandwidth while maintaining compactness ( $0.312\times 0.312\lambda ^{2}$ ). The antenna is substrate-independent and is demonstrated on two textile substrates with different dielectric properties and thicknesses. In far-field mode, the rectenna maintains over 40% efficiency from sub-1 $\mu \text{W}$ /cm2 power densities. In the near-field, a WPT efficiency up to 80% can be achieved. The simulated Specific Absorption Rate (SAR) shows up to 40 and 20 dBm power reception for HF and UHF operation, respectively, without exceeding the 1.7 W/kg limit. The far-field wearable rectenna is demonstrated powering a Bluetooth Low Energy node using a BQ25504 DC-DC converter from a best-in-class low power density of 0.88 and $0.55~\mu \text{W}$ /cm2 on-body and in-space, respectively.

Nowadays, MRI is focused on using ultra-high static magnetic fields (>7 T) to increase the signal-to-noise ratio. The use of high fields, on the other hand, requires novel technical solutions as well as more stringent design criteria for specific absorption rate levels, reducing radiative effect and coil resistance. In this paper, two flexible RF coils for 7 T human magnetic resonance, and 298 MHz ultra-high frequency operations were analyzed and characterized. Imaging of lower human limbs is regarded as a case study. The lumped element theory and subsequent numerical simulations were used to fine-tune the single-coil element and the dual-coil array design, respectively. Here, we demonstrate how the shape, size, configuration, and presence of the sample influence the coil performance. The penetration depth of the $B_{1}$ -field and the specific absorption rate values have been determined numerically using two numerical surface phantoms: saline and a multilayer human tissue. A preliminary study in the presence of a saline solution phantom has been carried out to develop and validate the dual-coil system. The frequency response of the dual-coil array was measured to assess its robustness when coupled to twelve human volunteers. We found that our design is robust to variations in the anatomical properties of the human thighs, and hence to coil bending. The presented approach can be useful for the implementation of flexible devices with high sensitivity levels and low specific absorption rate.

Magnetic resonance guided focused ultrasound (MRgFUS) is a non-invasive therapeutic modality for neurodegenerative diseases that employs real-time imaging and thermometry monitoring of targeted regions. MRI is used in guidance of ultrasound treatment; however, the MR image quality in current clinical applications is poor when using the vendor built-in body coil. We present an 8-channel, ultra-thin, flexible, and acoustically transparent receive-only head coil design (FUS-Flex) to improve the signal-to-noise ratio (SNR) and thus the quality of MR images during MRgFUS procedures. Acoustic simulations/experiments exhibit transparency of the FUS-Flex coil as high as 97% at 650 kHz. Electromagnetic simulations show a SNR increase of $13\times $ over the body coil. In vivo results show an increase of the SNR over the body coil by a factor of 7.3 with $2\times $ acceleration (equivalent to $11\times $ without acceleration) in the brain of a healthy volunteer, which agrees well with simulation. These preliminary results show that the use of a FUS-Flex coil in MRgFUS surgery can increase MR image quality, which could yield improved focal precision, real-time intraprocedural anatomical imaging, and real-time 3D thermometry mapping.

Missiles mounted on maritime vessels have two types of loads. One is the operating load consumed just before launch, and the other is the safety sensors load that must always be activated for safety. Because the operating load consumes a large power capacity, the power generated by the vessel’s own power generators must be supplied. Meanwhile, the loads for safety sensors are supplied through an energy storage system (ESS) because the safety sensors must be supplied with power even when the generators stop. However, the voltage difference between the generated power and the ESS power reaches ten times or more. Therefore, there is a problem in that the input of the two power sources with a large input difference must be transferred to two loads through only a pair of coils. To solve this problem, a WPT system is proposed to overcome the voltage difference between the generated power and the ESS power. The design method of the proposed system is analyzed mathematically, and it is verified through simulations and experiments. The proposed system has a maximum dc to dc power transfer efficiency of 76.8% with a capacity of 550 W and has the advantage that power is continuously supplied to the sensor loads even if the input voltage source is changed. In addition, by operating the proposed WPT system under a wide load range of 200 W to 1000 W, the effectiveness of the proposed WPT system is proved.

Pulmonary artery pseudoaneurysms are rare causes of massive hemoptysis, even less common in setting of COVID-19 pneumonia. We describe and discuss an index case of cavitating COVID-19 pneumonia complicated by a pulmonary artery pseudoaneurysm without concomitant pulmonary thromboembolism. The patient presented with severe hemoptysis and was managed by endovascular coil embolization. Good technical and clinical success was achieved with complete resolution of hemoptysis.

Abstract Background The safety controls in Resonance Magnetic Imaging (MRI) diagnostic site are numerous and complex. Some of these are contained in international directives and regularly conducted by medical physics expert after acceptance tests, consisting of a series of checks, measurements, evaluations called quality controls (QCs) and made to guarantee the image quality of the equipment. In this context, ensuring that the coils are in proper operating conditions is important to prevent and reduce errors in use and to preserve patient safety. Results A study by thermography was conducted to evaluate temperature changes of MRI coils during Quality Control (QC), in order to prevent any problems for the patient due to Radio Frequency waves. This experiment involves use of a thermal camera to detect temperature variations during MRI scans using head and body coils of two different tomography 1.5 T and 3.0 T static magnetic field. Thermal camera was positioned inside the MRI room to acquire images every 15 s for all the scansions duration. The observations have shown a temperature increase only for body coil of 1.5 MRI tomography, whereas no significative temperature variation has occurred for the other coils under observation. This temperature increase was later related to a fault of such coil. Conclusions The authors believe this simple method useful as first approach, during routinely QCs, to verify coils functioning and so to avoid patient hazards and are preparing a methodological study about functioning of the coils with respect to their temperature variation.

Ureteral embolisation has been described in the use of complete occlusion of the ureter to manage urinary leaks, haematuria, and fistulas. This is usually a management option of last resort in patients who have many co-morbidities, poor surgical candidates, or previous pelvic surgery. We report the use of vascular coils and glue to manage a uretero-ileal anastomotic leak following radical cystoprostatectomy.

PurposeThe aim of this study was to describe the treatment technique, outcomes, and complications of Schobinger stage IV head and neck arteriovenous malformations (HNAVMs) with associated high-output cardiac failure (HOCF) using ethanol and coils with the percutaneous suture technique.MethodsFrom January 2015 to December 2019, 19 patients who had HNAVMs with associated HOCF were treated first with a percutaneous suture of the remarkably dilated dominant drainage vein (RDDOV) and subsequent embolization with coils and ethanol. The percutaneous suture of RDDOV was preferred to be performed, followed by the deployment of coils and the injection of absolute ethanol via transarterial approach, direct puncture approach, or both of them. Treatment outcomes and complication rates were evaluated at follow-up.ResultsA total of 19 patients who experienced HNAVMs with HOCF received 19 percutaneous suture procedures and 84 embolization procedures with ethanol and coils. Complete or >90% shunt reduction of the AVM was achieved in 16 patients. Notably, 19 patients with New York Heart Association (NYHA) stage II improved to stage I, and the symptom of dyspnea disappeared after embolization. The symptoms of five patients with bleeding disappeared. All patients presented with cosmetic concerns; Four were cured, and eight had a clearly recognizable improvement. Of note, 19 (100%) patients presented with impairment of daily life, which was resolved. The minor complications were encountered and recovered by the self. No major complications occurred.ConclusionThis study provides evidence that ethanol and coil embolotherapy is effective and safe in treating HOCF caused by HNAVMs with acceptable complications in these cases. The percutaneous suture technique for RDDOV management can act as an adjunct for embolotherapy.

Background: Embolisation of the parenchymal tract is a key step after any other transhepatic or transplenic percutaneous portal vein catheterization since eventual venous bleeding is difficult to control and may require surgical management. Different techniques have been proposed to perform tract embolisation. The aim of this study is to compare the safety and efficacy of different techniques of haemostasis of the parenchymal tract. Materials and methods: All the interventional procedures with percutaneous transhepatic or transplenic access to the portal vein (excluding ipsilateral portal vein embolisation) from January 2010 to July 2020, in two tertiary hospitals, were retrospectively analyzed. The following data were evaluated: access site, the technique of embolisation, technical success in terms of immediate thrombosis of the tract, safety and clinical efficacy in terms of the absence of hemorrhagic and thrombotic complications. Results: One-hundred-sixty-one patients underwent 220 percutaneous transhepatic or transplenic portal vein catheterization procedures. The main indications were pancreatic islet transplantation, portal anastomotic stenosis after liver transplantation, and portal vein thrombosis recanalization. As embolic materials gelfoam was used in 105 cases, metallic micro-coils in 54 cases, and cyanoacrylic glue in 44 cases; in 17 cases the parenchymal tract was not embolized. Technical success was 98% without significant difference among groups (p-value = 0.22). Eighteen post-procedural abdominal bleedings occurred, all grade 3 and were managed conservatively; difference among groups was not significant (p-value = 0.25). We detected 12 intrahepatic portal branch thromboses not related to the embolisation technique; only one case of non-target embolisation was documented after liver tract embolisation with glue, without clinical consequences. Conclusion: Embolisation of the parenchymal tract after percutaneous portal vein catheterization is technically safe and effective. No significant differences were found between coils, glue, and gelfoam in effectiveness and complications rate. Level of evidence: Level 3, Cohort study. [ABSTRACT FROM AUTHOR]

Axis coincidence consideration is necessary in the design of gyrotron solenoids; besides, radial field component strongly affects the performance of gyrodevices owing to the transverse particle–wave interaction mechanism in it, especially for high-frequency operation. In this article, the theory of multiple eccentric coils is derived. It is capable of calculating the off-axis field inside the solenoid with specified displacement and tilt. Numerical calculations are validated by 3-D electromagnetic simulation methods. Based on the measured magnet field, the displacement and tilt of a three-coil magnet system are successfully predicted with a global optimization algorithm, and then, the magnet system is well calibrated using a pair of flanges. [ABSTRACT FROM AUTHOR]

In an inductive power transfer (IPT) system, the magnetic core is usually used to improve the coefficient between the primary and secondary coils. However, considering the iron losses on magnetic materials, the addition of magnetic core may affect the system efficiency and, at the same time, increase the weight of the IPT system significantly. Therefore, in this study, the aggregate influence of thickness, permeability, and iron losses of magnetic core on IPT system performance is comprehensively investigated. First, the equivalent circuit model of IPT system is established, and the formulas for different types of losses are analyzed. Then, the three-dimensional models of the IPT system with magnetic core in different shapes are established to simulate the aggregate influence of core thickness, permeability, and iron losses. The simulation results reveal that reducing the core thickness requires a larger saturation flux density of magnetic materials. In addition, only if the material losses below a certain value and an appropriate core shape are adopted, the addition of magnetic material can improve the system efficiency. Finally, experimental validation on a 3-kW IPT system is performed under the conditions of no magnetic core, using ferrite core in radial pattern and hollow square shapes, and using nanocrystalline core with the thickness of 22 μm and 16 μm in radial pattern and hollow square shapes, respectively. The results show that the high efficiency and lower overall weight of the IPT system can be achieved when nanocrystalline core with suitable permeability and shape is used. [ABSTRACT FROM AUTHOR]

The air-cored resonant induction machine removes the magnetic core, so the fields produced by the windings are truly 3-D in nature. The end-windings normally regarded as a nonactive and leakage source in conventional iron-cored machines now become an active part and contribute to the torque production. Therefore, the electromagnetic modeling can no longer be reduced to a 2-D analysis, and the 3-D inductance calculation becomes a key problem. The 3-D finite element analysis (FEA) can solve the 3-D magnetic field, but, first, the validity of its solution depends on the precision in geometry modeling. In particular, representing the end-winding region avoiding conductor clashing can be very complicated. Second, 3-D FEA solutions are computationally slow, and therefore inefficient as an “internal routine” of an optimization procedure. This article proposes a fast analytic 3-D winding inductance estimation method for air-cored resonant induction machines. The approach breaks down the real coils into straight conductors and represents them by single filaments located at their centers, then uses closed-form expressions derived from Neumann integrals to calculate the coil self and coil-to-coil mutual inductances, which are then collected into winding phase self and mutual inductances. All the independent coil-pair contributions are isolated, so as to eliminate redundant calculations. Good accuracy of the calculated results is confirmed by validation against both 3-D FEA and experimental results, including winding inductance breakdown and overall machine tested performance. [ABSTRACT FROM AUTHOR]

This article studies magnetic forces between transmitter (Tx) and receiver (Rx) coils in an inductive power transfer (IPT) system aiming to use those forces to align the coils and, consequently, improve power transfer. Due to its popularity, the analysis is conducted on a series–series compensated IPT system with planar spiral coils. The proposed method utilizes the bifurcation operation mode of the system and unloaded resonating receiver to maximize attractive force between magnetic couplers. Three-dimensional finite-element method simulations indicate that high-power IPT systems can develop enough attractive force to align coils even under nominal current. Regardless of the coil shape, e.g., spiral or Double-D (DD), the attractive forces tend to align the coils. Hence, a smart charging station can be devised based on self-aligning capability. Furthermore, this article proposes a mechanical structure to facilitate the attractive lateral force for the alignment of high power applications, i.e., wireless fast-charging stations. The forces are analyzed, modeled, and simulated for a 100-kW IPT system with an operating frequency of 20 kHz, while the self-aligning capability is experimentally verified on a downscale 11-kW prototype. [ABSTRACT FROM AUTHOR]

Endovascular therapy is the first-line treatment for the cavernous sinus dural arteriovenous fistulas, particularly transvenous embolization. This study aimed to assess the trans-superior ophthalmic vein approach to embolization for its safety, efficacy, and viability as a first-line treatment in selected patients, with a description of the microsurgical and endovascular techniques. We retrospectively reviewed patients with cavernous sinus dural arteriovenous fistulas treated using the direct superior ophthalmic vein approach with n-butyl cyanoacrylate and coils as the main embolic materials from 2015 to 2021. The safety and efficacy of the treatment were evaluated based on ocular and neurological improvement, angiographic obliteration, and recurrence. Of the 16 patients, all cases were diagnosed with cavernous sinus dural arteriovenous fistulas. The n-butyl cyanoacrylate was used as the sole embolic material in 12 cases, and coils were used in 4 cases. A direct superior ophthalmic vein approach was selected as the first option in 11 patients. All the patients achieved complete fistula obliteration and good recovery from ocular symptoms, accompanied by excellent cosmetic results. No recurrence was observed at a mean follow-up period of 26 months. Microsurgical dissection for exposure and direct cannulation of the superior ophthalmic vein as a route for fistula obliteration delivers excellent clinical outcomes, with a low rate of complications. Not only is it safe and effective as an alternative approach but it can also serve as first-line treatment in selected patients. [ABSTRACT FROM AUTHOR]

DC-Excited vernier reluctance machine (DC-VRM) using a 12-slot/10-pole-pair design, exhibits the advantages of small torque ripple and low cogging torque due to the inherent commentary characteristic. However, the inherent saliency is canceled out by a 12/10 pole combination of machine design driven by a traditional three-phase inverter. As a result, the sensorless operation in zero/low-speed regions becomes difficult because the position estimation methods using self-inductance detection cannot be applied. To tackle this problem, we first analyzed the saliency annihilation phenomenon through Fourier analysis that the odd-order harmonics in self-inductance are canceled. Moreover, reconstructing saliency method is proposed by splitting a phase winding into two sub-phase coils and using parallel H-bridge converters to supply sub-phase coils and achieve sensorless drive. Through this method, the saliency effect is recovered in self-inductance, thereby pulse injection sensorless drive can be applied. The constructed 12/10 DC-VRM sensorless drive shows good fault-tolerant ability and can be applied in safety-critical industry applications such as aerospace propulsion. Analysis and experiments are performed in the initial position detection, start-up and free-running stages to verify the feasibility of the proposed solution. A sector estimation accurate to 6° can be achieved. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of stator/rotor pole number combinations and permanent magnet (PM) numbers on electromagnetic performance of consequent-pole hybrid excited flux reversal machines (CP-HEFRMs), which have different numbers of PM poles and iron poles and concentrated AC and DC windings on the stator and a salient pole rotor. PMs in the slots of one stator pole are magnetized radially in the same direction, while opposite on adjacent stator poles. Magnetic field paths of DC, PM, and hybrid excitations are investigated. The phenomenon of flux cancellation, i.e., PM and DC MMFs in CP-HEFRMs are of opposite polarities in the flux-enhancing operating mode, is revealed and verified, for the first time, as the key feature that makes CP-HEFRMs different from other hybrid excited machines. Consequently, the saturation in stator pole and yoke can be mitigated and hence the overload capability of DC excitation is enhanced, which is verified by finite element analysis (FEA). Global optimizations are utilized to obtain the optimal rotor and stator pole number combinations and PM numbers for each stator pole. Torque, torque ripple, inductance, unbalanced magnetic force, and flux regulation capability are compared for different PM numbers and rotor pole numbers. Comparisons are made on consequent-pole and non-consequent-pole topologies in terms of torque capacity, flux regulation capability, and PM consumption to further illustrate the advantages of consequent-pole topology. A prototype machine is built and tested to validate the analyses. [ABSTRACT FROM AUTHOR]

Numerous research efforts are devoted to attain high performance and strong fault tolerance for the machine drives in safety critical applications, though the two aspects are conflicted in most cases. In this paper, a novel triple 3-phase PMA-SynRM with star-delta connected windings is proposed. The star-delta winding could produce a higher fundamental magneto-motive force and lower spatial harmonics than the conventional star winding. Therefore, it exhibits higher torque, lower torque ripple and lower iron loss, enhancing the healthy performance. In addition, the coils whose turn fault current is the highest are arranged in the inner delta part which provides circulating current path. It is demonstrated that the proposed winding solution reduces the fault current by 55% and the fault turn copper loss by 65%. Hence, the machine's fault tolerance is significantly improved. The machines with the star winding and star-delta winding are studied by detailed finite element calculation and experimental tests under various operation modes. Both the simulation and test results confirm that the proposed star-delta winding machine owns higher performance and stronger fault tolerance than the conventional star winding machine. Thus, it becomes a more competitive candidate for the high reliability drives. [ABSTRACT FROM AUTHOR]

In this paper, a dual-rotor slotless axial-flux permanent magnet (AFPM) motor with equidirectional toroidal winding (ED-TW) is proposed and compared with the AFPM motor with traditional toroidal winding (T-TW) with the same dimensions, number of coils and poles. Different from the T-TW, only the positive sides of coils of the ED-TW are left on one side of the stator core, the return sides of the coils are all removed to the other side of the stator core. Firstly, the structure and operation principle of the two motors are introduced and analyzed. To clarify the features of the ED-TW, the synthetic electromotive force (EMF) vector and armature reaction field of the ED-TW and T-TW are studied. Secondly, the main size equations of the AFPM motors with toroidal windings are presented. Subsequently, the electromagnetic characteristics of the AFPM motors with ED-TW and T-TW are analyzed and compared based on the three-dimensional finite element method (3D-FEM). The comparison results indicate that the AFPM motor with ED-TW has superiority in torque density and efficiency. Finally, a prototype of the AFPM motor with ED-TW is manufactured and tested, which validates the feasibility of the proposed motor and the correctness of the analysis of the 3D-FEM. [ABSTRACT FROM AUTHOR]

Objective: Wireless capsule endoscopy has been well used for gastrointestinal (GI) tract diagnosis. However, it can only obtain images and cannot take samples of GI tract tissues. In this study, we designed a magnetically-actuated biopsy capsule (MABC) robot for GI tract diagnosis. Methods: The proposed robot can achieve locomotion and biopsy functions under the control of external electromagnetic actuation (EMA) system. Two types of active locomotion can be achieved, plane motion refers to the robot rolling on the surface of the GI tract with a rotating uniform magnetic field. 3D motion refers to the robot moving in 3D space under the control of the EMA system. After reaching the target position, the biopsy needle can be sprung out for sampling and then retracted under a gradient magnetic field. Results: A pill-shaped robot prototype ($\phi$ 15 mm×32 mm) has been fabricated and tested with phantom experiments. The average motion control error is 0.32 mm in vertical direction, 3.3 mm in horizontal direction, and the maximum sampling error is about 5.0 mm. The average volume of the sampled tissue is about 0.35 mm $^{3}$. Conclusion: We designed a MABC robot and proposed a control framework which enables planar and 3D spatial locomotion and biopsy sampling. Significance: The untethered MABC robot can be remotely controlled to achieve accurate sampling in multiple directions without internal power sources, paving the way towards precision sampling techniques for GI diseases in clinical procedures. [ABSTRACT FROM AUTHOR]

Wireless charging of automated guided vehicles (AGVs) has been widely used because of its high security and convenience. However, due to the inevitable misalignment between the coupling coils, the charging system cannot maintain the constant current (CC) or constant voltage (CV) output. Therefore, this article proposes a misalignment-tolerant fractional-order wireless power transfer (FOWPT) system with CC or CV output. According to the principle of the fractional-order autonomous circuit, the natural resonant frequency and operating frequency can be adjusted adaptively with the change of transfer distance and load. Benefiting from the frequency characteristics and the new implementation method of the FOWPT, the system maintains CC and CV output, and the horizontal and vertical misalignment tolerances are within 44.4% and 22.2%, respectively. Therefore, the proposed system improves the freedom and convenience of charging, and provides a new wireless charging solution for AGVs. Future article will focus on more concise modeling and implementation methods of fractional-order systems, and improving the performance of the FOWPT. [ABSTRACT FROM AUTHOR]

Uniform magnetic fields are desired in a wide range of applications. The most known device achieving such a purpose is the pair of Helmholtz coils. It consists of two identical circular coils, with their main axis aligned and placed at a distance equal to their common radius from each other. The goal of this research is to find another arrangement of the coils in space so as to achieve the largest region possible with a uniform magnetic field. A topology optimization framework is developed for this purpose. It investigates the ideal distribution of current densities in an axisymmetric 2-D domain. The designed topology provides a significant improvement of the volume with a uniform field, which is 6.37 times larger than the reference one obtained with Helmholtz coils. [ABSTRACT FROM AUTHOR]

With the emergence of electric vehicles and electric aircraft technologies, lightweight motors have become a requirement. Conventional motors are generally made up of coils, permanent magnets, heavy iron stators, and rotor cores. This article presents complete analytical modeling and design of a novel coreless multi-phase magnetic resonant motor (MMRM), conceptualized through the approach of magnetic resonance coupling. The removal of magnetic iron cores drastically reduces the weight of the resulting motor. The stator and rotor cores of the motor are made of reinforced plastic fibers and can be 3-D printed. Unrelated to the general operating principle of the existing conventional electric motors, resonant wireless power transfer (WPT) is the key feature of these motors. All the essential machine characteristics, such as self-inductance, mutual inductance, torque, and frequency domains, are fully developed. The mathematical modeling of the machine’s physical phenomena is linked to its operation by simulation. This article shows the design concept and discusses the simulation procedure used to verify the developed analytical model through a finite-element analysis (FEA) from the established modeling topology equivalent to the proposed configuration motor model. Although the design is straightforward, an accurate analytical modeling and analysis are significant challenges to consider. [ABSTRACT FROM AUTHOR]

This article proposes an adaptive equivalent $RL$ -circuit model for eddy-current devices with a single electrical port (one terminal voltage and current) and translational movement. The device is first characterized by means of frequency-domain finite-element computations in the relevant frequency and position intervals, for subsequently fitting constant-coefficient $RL$ -ladder circuits of adjustable size (i.e., variable number of branches and loops). The accuracy of the ladder-circuit model is assessed in both the frequency and time domains. The time-varying position involves the force computation from the circuit and the coupling with the mechanical equation. By way of validation, we study the axisymmetric magnetic-levitation device of TEAM Workshop problem 28. Results exhibit good convergence to reference finite-element ones with increasing number of branches. [ABSTRACT FROM AUTHOR]

In this article, the inductance variation with the current in high-temperature superconducting (HTS) pancake coils is investigated numerically and experimentally. Both dc and ac modeling approaches are developed. The results show that the dc modeling approach, even though it considers the non-uniformity of the current density distribution using a power minimization criterion, is not sufficient to characterize the inductance variation, which is affected by the dynamic behavior of HTS coils. The ac modeling approach reproduces a variation of the inductance similar to the experimental results. [ABSTRACT FROM AUTHOR]

In this article, an optimization of an ironless permanent magnet tubular linear synchronous motor (PMTLSM) for applications in human support systems is presented. For this application, a bendable and light-weighted motor design is desired. For the computation of the motor force, an analytical method is established. The method is validated by the finite element (FE) analysis and utilized for the optimization of the motor geometry regarding the force-to-weight ratio. [ABSTRACT FROM AUTHOR]