Single Coil Research Articles

A dual coil induction heating machine for jewelry factories developed by electromagnetic analysis

An induction heating machine (IHM) generates magnetic flux density (B) and high temperature for combining precious metals as products in a jewelry factory. Since factories require new generation IHMs for increased productivity and cost savings, a dual coil IHM development approach is presented here to replace conventional, single-coil IHM using electromagnetic analysis (EMA). First, the experiments and the EMA investigated B generated by a conventional one using the factory operating condition. Both agreed, confirming the methodology and reliability of the EMA, which was analyzed to determine Bp. The Bp represents a B property for the new dual coil IHM to be expected to generate a comparable signal to the single coil. Then, in development, two novel designs of dual coil IHM (series and parallel) were investigated based on current flow circuits. For these designs, Bp was investigated using the EMA. As expected, the EMA results showed that both coils generated a different Bp, which was unfortunately incompatible with the conventional IHM and thus was inappropriate in actual use. However, the series dual coil showed better applicability since it generated B higher than the parallel coil under the same operating conditions. Next, the EMA was applied to determine the Bp of the series dual coil by varying the applied current (I), frequency (f), number of coil turns (N), and distance between coils (d). Finally, the EMA results revealed two options of the series dual coil with the optimum I, f, N, and d generating Bp comparable to the conventional IHM, as intended, achieving the factory's need with two times the productivity.

Dual Coil Patterned Ultra‐Thin Silicon Film Enable by Double‐Sided Process

AbstractDouble‐sided microfabrication process on an ultra‐thin silicon film has rarely been attempted due to the challenges in terms of the preparation and handling of a thin film in spite of its promising fabrication potentials. Such a process allows for doubling the thin film device density or providing dual functionalities for a thin film depending on whether the front and back sides of a thin film are processed identically or distinctively. Here, a novel double‐sided thin film processing strategy is introduced by realizing a dual coil patterned ultra‐thin silicon film that is working as an actuating or energy harvesting system. Experimentally, a dual coil patterned thin film enabled using the introduced approach shows remarkably enhanced device performance when compared with a single coil patterned counterpart. Furthermore, a multiphysics simulation model is developed and the resultant modeling data validate the experimentally measured performance enhancement. Finally, the structural durability of the thin film upon cyclic loading is tested and its diverse vibration modes are investigated.

Novel multi-helical coil heat exchanger-based small-scale organic Rankine cycle: A detailed heat transfer analysis

This paper discusses a prototype of the ORC, which is developed utilizing a novel multi-coil evaporator and condenser for the waste heat source with a temperature below 100 °C. R123 acts as a working fluid for the ORC. The thermal performance of a multi-helical coil is evaluated experimentally and compared to the single-helical coil heat exchanger available in the literature.The performance of a novel multi-coil heat exchanger depicts that when the Reynolds Number varies from 60000 to 120000, the heat transfer coefficient varies from 1560 W/(m2K) to 2900 W/(m2K) for a single coil heat exchanger and 3014 W/(m2K) to 4531 W/(m2K) for multi helical coil evaporator. The Nusselt Number varies from 300 to 570 for single-coil heat exchangers and 715 to 1076 for multi-helical coil heat exchangers. The results show that the expander's power output is around 2.14 kW and proportional to the evaporator temperature and pressure increase. The high condensing temperature decreases the expander power output. The main contribution of the present work is developing a small ORC system with novel multi-helical coil heat exchangers and testing them on a lab scale for the most probable application to fulfill the electricity requirement in remote areas in the future.

Miniaturized Wirelessly Powered and Controlled Implants for Multisite Stimulation.

This paper presents a miniaturized implant with a diameter of only 14 mm, which houses a novel System on Chip (SoC) enabling two voltage level stimulation of up to 16 implants using a single Tx coil. Each implant can operate at a distance of 80 mm in the air through the inductive resonant link. The SoC consumes only 27 μW static power and enables two channels with stimulation amplitudes of 1.8 V and 3.3 V and timing resolution of 100 μs. The SoC is implemented in the standard 180 nm complementary metal oxide semiconductor (CMOS) technology and has an area of 0.75 mm × 1.6 mm. The SoC comprises an RF rectifier, low drop-out regulator (LDO), error detection block, clock data recovery, finite state machine (FSM), and output stage. Each implant has a PCB-defined passcode, which enables the individual addressability of the implants for synchronized therapies. The implantable device weighs only 80 mg and sizes 20.1 mm3. Tolerance of up to 70° to angular misalignment was measured at a distance of 50 mm. The efficacy of bilateral stimulation was further verified by implanting two devices on two sides of a pig's neck and performing bilateral vagus nerve stimulation (VNS), while monitoring the heart rate.

First non-invasive magnetic phrenic nerve and diaphragm stimulation in anaesthetized patients: a proof-of-concept study

BackgroundMechanical ventilation has side effects such as ventilator-induced diaphragm dysfunction, resulting in prolonged intensive care unit length of stays. Artificially evoked diaphragmatic muscle contraction may potentially maintain diaphragmatic muscle function and thereby ameliorate or counteract ventilator-induced diaphragm dysfunction. We hypothesized that bilateral non-invasive electromagnetic phrenic nerve stimulation (NEPNS) results in adequate diaphragm contractions and consecutively in effective tidal volumes.ResultsThis single-centre proof-of-concept study was performed in five patients who were 30 [IQR 21–33] years old, 60% (n = 3) females and undergoing elective surgery with general anaesthesia. Following anaesthesia and reversal of muscle relaxation, patients received bilateral NEPNS with different magnetic field intensities (10%, 20%, 30%, 40%); the stimulation was performed bilaterally with dual coils (connected to one standard clinical magnetic stimulator), specifically designed for bilateral non-invasive electromagnetic nerve stimulation. The stimulator with a maximal output of 2400 Volt, 160 Joule, pulse length 160 µs at 100% intensity was limited to 50% intensity, i.e. each single coil had a maximal output of 0.55 Tesla and 1200 Volt. There was a linear relationship between dosage (magnetic field intensity) and effect (tidal volume, primary endpoint, p < 0.001). Mean tidal volume was 0.00, 1.81 ± 0.99, 4.55 ± 2.23 and 7.43 ± 3.06 ml/kg ideal body weight applying 10%, 20%, 30% and 40% stimulation intensity, respectively. Mean time to find an initial adequate stimulation point was 89 (range 15–441) seconds.ConclusionsBilateral non-invasive electromagnetic phrenic nerve stimulation generated a tidal volume of 3–6 ml/kg ideal body weight due to diaphragmatic contraction in lung-healthy anaesthetized patients. Further perspectives in critically ill patients should include assessment of clinical outcomes to confirm whether diaphragm contraction through non-invasive electromagnetic phrenic nerve stimulation potentially ameliorates or prevents diaphragm atrophy.

Dual-frequency resonant coil design for low-γ X-nuclear and proton magnetic resonance imaging at ultrahigh fields.

Low-γ X-nuclear MRS and imaging have played a key role in studying metabolism and physiopathology, especially at ultrahigh fields. We design and demonstrate a novel and simple dual-frequency RF resonant coil that can operate at both low-γ X-nuclear and proton frequencies. The dual-frequency resonant coil comprises an LC coil loop and a tuning-matching circuit bridged by two short wires of the desired length to generate two resonant modes: one for proton MRI and the other for low-γ X-nuclear MRS imaging with a large difference in their Larmor frequencies at ultrahigh fields. The coil parameters for the desired coil size and resonant frequencies can be determined via numerical simulations based on LC circuit theory. We designed, constructed, and evaluated several prototype surface coils and quadrature array coils for 1 H and 2 H or 17 O imaging, with small-sized (diameter ≤ 5cm) coils evaluated using a 16.4 T animal scanner, and a large-sized (15 cm diameter) coil on a 7 T human scanner. All coils could be tuned/matched and driven in the single coil or array coil mode to the resonant frequencies of 1 H (698 and 298 MHz), 2 H (107 and 45.8MHz), or 17 O (94.7 and 40.4MHz) for imaging measurements and evaluation at 16.4and 7 T, respectively. The dual-frequency resonant coil or array provides adequate detection sensitivity for 1 H MRI and excellent performance for low-γ X-nuclear MRS imaging applications, and excellent coil decoupling efficiency between the array coils at both resonant frequencies with an optimal geometric overlap. It provides a simple, cost-effective dual-frequency RF coil solution to perform low-γ X-nuclear MRS imaging for preclinical and human applications, especially at ultrahigh fields.

Multi-Objective Optimization Design and Performance Comparison of Magnetorheological Torsional Vibration Absorbers of Different Configurations.

The purpose of this study is to provide a convenient optimization design method for magnetorheological torsional vibration absorbers (MR-TVA) suitable for automotive engines, which is a damper matching design method that takes into account the needs of the engine operating conditions. In this study, three kinds of MR-TVA with certain characteristics and applicability are proposed: axial single-coil configuration, axial multi-coil configuration and circumferential configuration. The magnetic circuit model, damping torque model and response time model of MR-TVA are established. Then, under the constraints of weight, size and inertia ratio, according to different torsional vibration conditions, the MR-TVA mass, damping torque and response time are multi-objective optimized in two directions. The optimal configurations of the three configurations are obtained from the intersection of the two optimal solutions, and the performance of the optimized MR-TVA is compared and analyzed. The results show that the axial multi-coil structure has large damping torque and the shortest response time (140 ms), which is suitable for complex working conditions. The damping torque of the axial single coil structure is generally large (207.05 N.m), which is suitable for heavy load conditions. The circumferential structure has a minimum mass (11.03 kg) and is suitable for light load conditions.

Pulsed Eddy Current Sensor for Cascade Electrical Conductivity and Thickness Estimation in Nonferrous Metal Plates

This paper presents a pulsed eddy current (PEC) sensor design for cascade electrical conductivity and thickness estimation in non-ferrous metal plates. With a single excitation coil design, the combined change in magnetic flux density caused by the excitation coil and the induced eddy current (EC) in the test plate is detected by a compact anisotropic magneto-resistive (AMR) sensor. The effects of the varying input pulse width are discussed with both numerical simulations in commercial finite element analysis (FEA) software and experimental results, and the time-domain characteristics of the responses are analyzed in relation to the properties of the test plates. It is revealed that the electrical conductivity can be gauged based on the peak value of the short pulse response, and with a known electrical conductivity value, plate thickness can be subsequently derived with the rise time of the long pulse response. A cascade estimation process is therefore proposed to calculate the parameters sequentially by adopting hybrid input signals with both short and long input pulses. Verified by the FEA results, this cascade estimation process was then experimentally validated with a prototype of the PEC sensor.

Chain Sliding versus β-Sheet Formation upon Shearing Single α-Helical Coiled Coils

Chain Sliding versus β-Sheet Formation upon Shearing Single α-Helical Coiled Coils

Chain Sliding versus β-Sheet Formation upon Shearing Single α-Helical Coiled Coils

Chain Sliding versus β-Sheet Formation upon Shearing Single α-Helical Coiled Coils

Transmitter Coils Selection Method for Wireless Power Transfer System With Multiple Transmitter Coils and Single Receiver Coil

This article proposes transmitter coils selection method for maximum power transfer efficiency in the wireless power transfer (WPT) system with multiple transmitter coils and a single receiver coil (MTSR). The proposed method is divided into two main steps. First, transmitter coil selection criteria that can achieve maximum efficiency are derived by analyzing the relative magnitude of the coupling coefficient between each coil. Next, a method for calculating the relative coupling coefficients used for the criteria only with the input current value is presented. This method differs from previous studies in that it can be applied when some transmission coils are deactivated. Therefore, it is possible to select the optimal transmitter coil combination in consideration of the characteristics of the receiver coil using the proposed method without information on the receiver coil. By the proposed transmitter coils selection criteria, the power transfer efficiency has an average of 96.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 0.5% when the output power is 300 W, even with the position change of the receiver coil. In addition, it is confirmed that the proposed coupling coefficient extraction method has a slight error of 2.5% compared to the measured value by a vector network analyzer.

First performance test of FeSe0.5Te0.5-coated conductor coil under high magnetic fields

Iron-based superconductors have attracted intense interest from scientists around the world. The first FeSe0.5Te0.5 hybrid coil, including one FeSe0.5Te0.5 single pancake coil (SPC) and eight YBCO double pancake coils (DPCs), was successfully fabricated and tested in this study. The FeSe0.5Te0.5 tape used in the hybrid coil is encapsulated to strengthen the tape, and has a thickness of 0.15 mm and a width of 10.5 mm to withstand the high stress during the cold test. The FeSe0.5Te0.5 encapsulated tape exhibits good performance in the 4.2 K cold test. YBCO DPCs were divided into two groups connected to both sides of the FeSe0.5Te0.5 SPC. The critical current of the FeSe0.5Te0.5 coil was measured as the background field increased from 0 T to 10 T. The transport critical current of the FeSe0.5Te0.5 SPC was 108.1 A at self-field and 17.4 A at 10 T, which had almost the same performance as the FeSe0.5Te0.5 tape. The results of this study showed that the FeSe0.5Te0.5-coated conductor coil has good performance in high magnetic fields.

Self-Docking Characteristics and Sliding Mode Control on Space Electromagnetic Docking Mechanism

Electromagnetic docking technology can realize the flexible docking and safe separation of spacecraft, and presents broad application prospects. However, an electromagnetic force with nonlinearity and uncertainty properties increases the difficulties of the electromagnetic docking control. In this work, the magnetic dipole far-field model of a single coil has been established by simplifying the electromagnetic docking device. Afterward, the electromagnetic force and electromagnetic torque models were obtained during space electromagnetic docking. The space electromagnetic docking dynamics model was established by analyzing the influences of disturbance force and disturbance torque caused by a geomagnetic field. According to the one-dimensional docking reference trajectory, the sliding mode variable structure controllers based on exponential reaching law were proposed and verified. The quasi-sliding mode control method has been adopted to solve the chattering problem in sliding mode variable structure control. The simulation results show that it is necessary to design and add an electromagnetic controller to achieve flexible docking. The sliding mode variable structure controller based on quasi sliding mode can realize one-dimensional electromagnetic flexible docking, and have made good tracking effect on the reference trajectory. Compared with the control method based on exponential reaching law, it can reduce the chattering phenomenon in the control process. The sliding mode variable structure control strategy based on quasi sliding mode presented good robustness. Therefore, it can provide theoretical guidance and control reference for the flexible docking process between electromagnetic satellites.

Torque modeling of reluctance spherical motors using the virtual work method

Compared to traditional single-axis motors, reluctance spherical motors (RSMs) can generate rotational torque in three spatial latitudes on a single motor, thus enabling three degrees-of-freedom (DOF) motion. Due to the complexity of their structure, the finite element method (FEM) is usually used to calculate the torque, but this method has the problem of consuming huge computational resources and long computation time. To address the problem that the FEM for calculating the torque of RSM consumes a lot of computation time, the torque model of RSM is developed by using the virtual work method considering the nonlinear cases of the magnetic circuit in this paper. Firstly, the inductance simulation of a single stator coil of a RSMs is carried out using finite element simulation software to obtain its inductance model. When the magnetic circuit is linear, the torque is obtained by partial differential calculation of the inductance surface. When the magnetic circuit is nonlinear, the distribution of flux linkage is first solved. Then, the electromagnetic torque is obtained by partial differential calculation of the magnetic co-energy. The calculated results are then projected to the global coordinate system to convert the two-DOF torque to the three-DOF torque. Finally, the experimental torque measurement platform is built, and the torque is measured and compared with the analytical calculation results. The results show that this method greatly reduces the amount of computing and simulation work with accurate modeling and provides a theoretical basis for the study of energization strategies and real-time control of the reluctance spherical motors.

The Presence of a Single Nuchal Cord in the Third Trimester May Not Affect Tei Index in LGA Fetuses

(1) Background: The aim of this study was to assess the RV (right ventricle) and LV (left ventricle) Tei index in large for gestational age (LGA) fetuses with a single 360-degree umbilical coil of the umbilical cord around the fetal neck identified by ultrasound in the third trimester of gestation. (2) Methods: The RV and LV Tei index for the cardiac function were measured in 297 singleton pregnancies, and we identified 25 LGA fetuses. There were 48% of LGA fetuses with a nuchal umbilical cord-LGA/NC-larger for gestational age fetuses with a nuchal cord. NC was detected with a color Doppler during a transverse scan of the fetal neck, when the umbilical cord formed a U shape. All fetuses had normal anatomy and normal uterine, placental, umbilical, intracardiac and cerebral Doppler waveforms values for their gestational age. (3) Results: The RV Tei index was significantly higher in the LGA subgroup vs. AGA (0.6 ± 0.2 vs. 0.50 ± 0.2; p value = 0.01), but in LGA fetuses with a single coil of the nuchal cord, there were not any significant changes in the Tei indexes. (4) Conclusions: The Tei index might not be impacted by the presence of the nuchal cord in LGA fetuses.

Computational analysis of multichannel magnetothermal neural stimulation using magnetic resonator array.

Heating nanoparticles with a magnetic field could facilitate selective remote control of neural activity in deep tissue. However, current magnetothermal stimulation approaches are limited to single-channel stimulation. Here, we investigated various designs for multichannel magnetothermal stimulation based on an array of resonant coils that are driven by a single loop coil. Using a tuning capacitor that allows resonant coils to resonate at the operating frequency, each coil's ON and OFF resonance can be controlled, enabling us to select stimulation channels. We found that smaller inner diameters of resonant coils produce more localized magnetic fields while larger coils produce magnetic fields over a longer distance. The constructed multichannel resonant coil arrays can provide a high enough magnetic field intensity to raise the temperature of nanoparticles by 8°C when we apply 35.2W into the loop coil that is spaced 1mm from the target neurons. This multichannel stimulation using a simple resonant circuit approach would be useful for clinical applications of magnetothermal neural stimulation.

Numerical simulation of intracerebral hemorrhage detection using magnetic induction spectroscopy

Magnetic Induction Spectroscopy (MIS) is an emerging technique for contactless measurement of bioimpedance with promising application in intracerebral hemorrhage (ICH) detection. Here, we report numerical simulations of ICH detection based on the MIS. A novel MIS sensor using two planar rectangular spiral coils (TPRSC) as the exciter with frequency range 120 kHz-9 MHz is proposed for the first time. The exciter can generate an antisymmetric normal magnetic field at the detection sensor, and hence the primary voltage can be canceled theoretically. We construct symmetry-based and asymmetry-based ICH models with realistic anatomic structure and hexahedral discretization feature for numerical simulations. The numerical simulations based on the finite integration technique are conducted in the three-dimensional electromagnetic analysis software CST. The voltage phase spectrum, the phase change spectrum and the relative conductivity change spectrum at different hemorrhage volumes are calculated. We compare sensitivities between the TPRSC-based MIS sensor and the conventional type (CC MIS sensor) which uses the single planar rectangular spiral coil as the exciter. Using the constructed ICH models, the specific absorption rate (SAR) and the internal electric field strength are computed to evaluate the electromagnetic safety of the TPRSC-based MIS sensor. Results show that compared with the CC MIS sensor, the sensitivity of the TPRSC-based MIS sensor for measuring the voltage phase is improved by two orders of magnitude, and for measuring the phase change is improved by more than ten times. The phase change and relative conductivity change spectra for the TPRSC-based MIS sensor demonstrate good separability between different small-volume hemorrhages. In addition, the electromagnetic safety of the TPRSC-based MIS is also superior to that of the CC MIS sensor, which conforms to the IEEE standard and the ICNRP guidelines over a wide range of the amplitude of the excitation current.

Power-Spilt-Based Wireless Charging System With Communication-Free Coordination Control

In this article, a power-split-based wireless charging system (WCS) with communication-free coordination control is proposed to combat wide load and coupling variations. By using a magnetic integrated inductor, two power delivery channels are created from a single receiver coil. Large portion of received energy is directly delivered to the load. Small amount of energy is converted by using a low-voltage low-power dc–dc converter to regulate the output voltage or current achieving constant voltage (CV) or constant current (CC) charging operation. This proposal achieves higher power conversion efficiency than the traditional two-stage cascaded converter WCS. Since the dc–dc converter only processes partial power of the WCS system, this proposal reduces the voltage stress of the devices and design difficulty. A communication-free coordination control is applied, which is established by sensing the input current drop caused by the burst operation of the partial-power dc–dc converter. Thus, the CC-CV charging is realized by PWM control at the receiver (Rx) side, and the inverter is regulated with subharmonics control scheme to maintain nearly constant Rx coil current. Simulation results for both high-voltage high-power scenarios and low-voltage low-power (LVLP) scenarios are provided to investigate the operation of the proposed WCS. Finally, experimental results are captured from a 250 W/60–84 V LVLP prototype to validate the feasibility and practicability of proposed concept.

Temporal interference for dual site transcranial magnetic stimulation

Dual-site Transcranial Magnetic Stimulation (ds-TMS) is a TMS protocol that involves stimulating two areas of the brain in close succession. This method is useful for studying the connections between two physical parts of the brain. TMS coils are generally designed for use on a single target area in the brain. When ds-TMS targets are in close proximity to one another, using traditional coils in a limited space increases the possibility of errors associated with positioning, resulting in inconsistent pulse strength and trajectory. We developed a single TMS coil that uses temporal interference (TI) to stimulate multiple targets within close proximity without compromising the ideal positioning of either location. TI TMS operates based on the frequency difference of two magnetic fields delivered simultaneously. The frequency difference between the two fields results in an envelope which can be steered to target a different location without moving the coil. We designed a TI-TMS coil and show that the peak induced electric field can be steered 4 cm in either direction (8 cm range) from the center point of the coil while delivering a peak field of 120 V/m, which is above the minimum 100 V/m needed to activate neurons. An experimental model was built using the same dimensions as the simulation model and validated that the physical model is able to steer the magnetic pulse using TI.

Wireless Measurement of the Degradation Rates of Thin Film Bioresorbable Metals Using Reflected Impedance

A method using reflected impedance to determine the electrical degradation rates of bioresorbable metals for physically transient electronic devices is outlined. This approach uses known mutual inductor interactions with simple single turn disk coil geometries and a frequency measurement system to track the reduction of the mean thickness of a thin film metal ring as it degrades. Experiments using <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {500~ \text {n} \text {m} }$ </tex-math></inline-formula> thick zinc rings, fabricated by photolithography, thermal evaporation and lift-off, found a mean degradation rate of 278 nm h−1 in 37 °C de-ionised water. Experiments in 37 °C 1 mM hydrochloric acid found two distinct periods of degradation and a total degradation rate of 632 nm h−1 that closely matched the degradation rate measured using profilometry of 608 nm h−1.