Coil Parameters Research Articles

Wireless Power and Data Transfer System Using Multidirectional Magnetic Coupler for Swarm AUVs

In this letter, a simultaneous wireless power and data transfer system based on a novel multidirectional magnetic coupler is presented for the application of swarm AUVs. The transmitting coil consisting of two reversely wound helix loops can generate a multidirectional magnetic field in space, which supplies power to multiple arc-shaped receiving coils placed in different directions. Aiming at high coupling strength and low core volume, a multiobjective genetic algorithm is used to optimize coil parameters. In addition, a hybrid injection communication method based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC-S</i> compensation topology is proposed and analyzed. An experiment platform is built and the results show that the system can achieve 92.25% efficiency at a power level of 200 W when four AUVs are powered. Meanwhile, the transferred data are successfully recovered at the data rate of 30 kbps.

Simulation and Experiment of Electromagnet for High-Speed On-off Valve for Vehicle Shifting System

The high-speed on-off valve is the core component for adjusting the oil pressure of the pressure reducing valve in the clutch shifting system of engineering vehicles, and its response speed is one of the important indicators to measure its performance. In order to improve the dynamic performance of high-speed on-off valve, the electromagnet with solid magnetic isolation structure was designed and simulated by considering the eddy current loss factor. A high-speed on-off valve electromagnetic actuator with high response speed was obtained. Firstly, the theoretical calculation and verification of the theory were carried out by using the electromagnet design theory, and the theoretical model of the electromagnet was built. Secondly, the electromagnet parameter model was brought into the finite element simulation software ANSYS Electronics to simulate and optimize the static magnetic field and the transient magnetic field respectively. The different structural parameters (guide bush thickness, outer magnetic pole thickness, magnetic isolation structure, armature length) were analyzed. And the effect of the coil parameters (number of strands) on the steady-state electromagnetic force and the dynamic displacement of the armature was analyzed. The values of the structural parameters of the electromagnet were subsequently determined. Finally, the static and dynamic characteristics experiment of the magnetically separated solid electromagnet is designed and processed. The experiment and simulation results are in good agreement. The feasibility of the high-resistance electromagnet structure design and the correctness of the simulation are verified. Reasonable optimization of structural parameters and coil parameters has obvious significance for improving the dynamic characteristics of high-speed on-off valve electromagnets.

Development of liquid helium-free cryostat for a superconducting undulator

The superconducting undulator (SCU) is a type of insertion device with great development potential. SCU can generate higher peak field than permanent magnet undulator at the same period length and vacuum gap. In the early stage of SCU development, it is necessary to test various winding schemes and coil parameters. A reliable cryogenic system is the precondition for superconductivity. To test SCU short prototypes in a compatible way, a convenient low-temperature platform is in high demand. In addition, due to the high cost and unpredictable availability of liquid helium, a helium-free platform is beneficial. In this paper, a successful low-temperature platform for the SCU short module test is introduced. It is compatible with different coil structures. Comprehensive design ingredients, such as the current leads, cold mass, thermal shield, etc., are described in detail. The platform performances in the module test are recorded and analyzed as well. The cold mass was cooled to about 2.9 K, and the maximum current of the superconductor was approximately 500 A.

Targeting the pathological network: Feasibility of network-based optimization of transcranial magnetic stimulation coil placement for treatment of psychiatric disorders.

It has been recognized that the efficacy of TMS-based modulation may depend on the network profile of the stimulated regions throughout the brain. However, what profile of this stimulation network optimally benefits treatment outcomes is yet to be addressed. The answer to the question is crucial for informing network-based optimization of stimulation parameters, such as coil placement, in TMS treatments. In this study, we aimed to investigate the feasibility of taking a disease-specific network as the target of stimulation network for guiding individualized coil placement in TMS treatments. We present here a novel network-based model for TMS targeting of the pathological network. First, combining E-field modeling and resting-state functional connectivity, stimulation networks were modeled from locations and orientations of the TMS coil. Second, the spatial anti-correlation between the stimulation network and the pathological network of a given disease was hypothesized to predict the treatment outcome. The proposed model was validated to predict treatment efficacy from the position and orientation of TMS coils in two depression cohorts and one schizophrenia cohort with auditory verbal hallucinations. We further demonstrate the utility of the proposed model in guiding individualized TMS treatment for psychiatric disorders. In this proof-of-concept study, we demonstrated the feasibility of the novel network-based targeting strategy that uses the whole-brain, system-level abnormity of a specific psychiatric disease as a target. Results based on empirical data suggest that the strategy may potentially be utilized to identify individualized coil parameters for maximal therapeutic effects.

Conductivity Measurement of Solid Metal Rods Using High-Frequency Eddy Current Method

Conductivity is an essential parameter for solid metal rods, which can be applied to assess quality. In this paper, an eddy current testing(ECT) method is investigate to measure the conductivity of solid metal rods. Above all, the simplified theoretical model is derived for a coil encircling a cylindrical sample. According to the proposed model, the real part of the coil impedance variation at high frequency (~ MHz) is closely related with the reciprocal of root of the rod conductivity. Therefore, a simple and effective conductivity measurement method for solid rod conductivity measurement is investigated based on the relationship between the impedance variation and the solid rod conductivity. Moreover, the effect of metal rods and coils parameters on the proposed method are also analyzed. Finally, the proposed method is verified with measurements of conductive materials. The results demonstrate the investigated simplified theoretical model is accurate and reasonable, and the relative error of the solid rod conductivity measurement is 2.2%.

Theorizing a Simple Ferrite Cored Coil Using Image Coils in Wireless Power Transfer

The technology of wireless power transfer, which wirelessly transmits power to any device, has been widely studied. Wireless power transfer using magnetic field resonance involves the use of coils and a material called ferrite, which improves the transmission characteristics. Until now, electromagnetic field analysis has been used to design ferrite cored coils, but electromagnetic field analysis requires a long analysis time and a computer with a large amount of memory. In this study, the ferrite shield and coil are represented as a image coil under the condition that the positional relationship between the ferrite shield and the coil does not change. This enabled the derivation of mutual inductance only by numerical analysis, which had been difficult up to now. In addition, experiments have shown that when the coil size does not change, mutual inductance can be derived only by numerical analysis using arbitrary coil parameters, regardless of the number of turns and pitch. The average error in deriving the design value was 5.2%. This facilitated the design of ferrite cored coils at 85 kHz and contributed greatly to the design of the system.

Improvement of Moving RFID Microtag Detection in Different Angular Orientations Using Multiple Tubular Coils

Directionality problem caused by the rolling of microtag with flowing fluid seriously affects the reliability of oilwell downhole radio frequency identification (RFID) system. In this paper, we propose a novel RFID reader antenna structure using multiple tubular coils for reduced orientation sensitivity. The conventional solenoid coil and saddle-coil pairs are combined to overcome the respective defects of the two coils and develop their advantages to form a complementary structure at the same time. Then, a series of coil parameters are designed in detailed to provide strong magnetic field distribution both in the x-axis, y-axis and z-axis directions. To verify the design, the proposed multiple tubular coils have been fabricated and measured. Experimental results demonstrate more potential than the conventional solenoid coil for microtag detection in different angular orientations, which is very important to improve the reliability and applicability of current oilwell downhole RFID system.

Coil Parameter Analysis in Wireless Electric Vehicle Charging

The hassle of using plug-in charging for electric vehicles (EVs) such as connecting charger to the port of vehicles, risk of getting electrocuted during rain, dirty and oily charging cable etc. can be eliminated using wireless/induction power transfer (IPT). It can be made smart and automated. Hence, IPT can be considered the future of EV charging. However, the technology is just emerging and there are a lot of limitations at present. The major problems are less efficiency caused by coil misalignment and air gap, and the electro-magnetic field generated around the coils which possesses greater risk for human health. These can be improved by selecting the types of coils and shields which produce maximum magnetic flux between the coils whereas reduce the flux outside the coils. In this research, the strength of magnetic fields produced by various types of coils (circular, square and hexagonal) were simulated in Ansys Maxwell 3D to understand their features and to know which coil is the best for high power transfer efficiency. Similarly, the effects of using ferrite and aluminum shields for leakage reduction, by varying their thickness, were studied. Finally, the leakage flux values were simulated at very high currents to understand their behavior in such conditions.

Crack Growth Monitoring with Structure-Bonded Thin and Flexible Coils.

Structural health monitoring with thin and flexible eddy-current coils is proposed for in situ detection and monitoring of fatigue cracks in metallic aircraft structures, providing a promising means of crack sizing. This approach is seen as an efficient replacement to periodic inspections, as it brings economic and safety benefits. As such, printed-circuit-board eddy-current coils are viable for in situ crack monitoring for multi-layer, electrically conductive structures. They are minimally invasive and could be attached to or embedded into the evaluated structure. This work focuses on the monitoring of fatigue crack growth from a fastener hole with structure-bonded, thin, and flexible spiral coils. Numerical simulations were used for optimization of the driving frequency and selection of crack-sensitive coil parameters. The article also demonstrates the fatigue crack detection capabilities using spiral coils attached to a 7075-T6 aluminum coupon.

Research on Current Drive System of Magnetorheological Damper Based on Fuzzy PI Control.

Magnetorheological dampers (MRD) are increasingly used in smart structural damping systems due to their good damping properties. In practical applications, as a nonlinear device, the parameters of the internal excitation coil of the magnetorheological damper will change during operation under the influence of the temperature and external environment, deteriorating the dynamic performance of the output current of the driver and reducing the damping effect of the system. Therefore, the current driver needs to be optimized for this phenomenon in order to ensure accurate current output. In this paper, a mathematical model of the buck circuit combined with the MRD equivalent circuit is established, and after analyzing the model, the parameters of the PI controller are rectified to lay the foundation for the design of the adaptive law. Then, with the help of the fuzzy control method, a fuzzy PI control strategy for MRD current driver is established, which enables the current driving system to adjust the control parameters adaptively when the MRD parameters change and ensure the accurate driving current output. The experimental results demonstrate that the fuzzy PI control strategy has a stronger robustness in the face of parameter changes of the control object compared with the traditional PI control at a system parameter change rate of 40%.

RANCANGAN PERALATAN ALTERNATOR PADA SISTEM PENGAPIAN BUSI ELEKTRONIK CDI SEPEDA MOTOR

In automotive spark plug ignition, gasoline-fueled vehicles require spark ignition system equipment. One of the electronic cdi spark plug ignition systems uses electronic equipment and components that replace conventional spark plug ignition systems. In this study, the design of the electronic cdi spark plug ignition system using the main equipment of the alternator produces an ac output voltage source on the exiter coil winding. The results of the design of the equipment are generated by a timer signal from the pulser component related to the rpm speed of the alternator permanent magnet rotor shaft which is driven by the rotation of the ac electric motor shaft. The ignition timing process of the spark plug is controlled by the charge/discharge condition of the electronic capacitor charge in the cdi device to produce an ac power supply voltage, the output time function to the primary input of the coil is expressed as the Vprimer(t) parameter in volts. The result of the primary voltage Vprimer(t) at the primary input of the induced coil generates a high voltage at the secondary output of the ignition coil, which is expressed as the Vo(coil) parameter. The result of a high voltage Vo(coil) momentarily connected to the spark plug produces spark ignition which indicates that there is a spark in the spark plug gap.

Efficiency Improvement of Magnetic Coupler with Nanocrystalline Alloy Film for UAV Wireless Charging System with a Carbon Fiber Fuselage

Existing research on the magnetic coupler of unmanned aerial vehicle (UAV) wireless charging systems usually ignores the UAV fuselage, but the fuselage causes eddy current loss and reduces a system’s efficiency. Therefore, aiming at the above problems, this paper proposes a design for a magnetic coupler using nanocrystalline cores to reduce the loss caused by the UAV fuselage. First, the parameters of the asymmetric circular coils were designed for higher mutual inductance. The losses caused by the windings and cores were also calculated. Second, for the loss effect of the carbon fiber fuselage, the fuselage was modeled as an additional coil coupled with both the transmitting and receiving coils. The fact that the eddy current induced by the fuselage leads to efficiency reduction is revealed, which has been generally ignored by previous research. Then, the effect of the nanocrystalline alloy was analyzed based on the magnetic circuit model. An optimized nanocrystalline alloy film was applied to reduce eddy current loss and improve coupler efficiency. Finally, an experimental prototype with a 500 W output, 90.3% efficiency, and a 300 mm air gap were fabricated. When compared to the design without UAV material considerations, the coupler efficiency was improved by 7.9%.

Detachable electromagnetic actuation system for inverted microscope and its function in motion control of microrobots

In recent years, magnetic microrobots have shown unique advantages and exciting prospects in many application fields. However, the motion mechanism, driving force and imaging effect of magnetic microrobots still need to be further studied and improved. These factors are related to the design of magnetic actuation systems and the manufacturing of microrobots. This paper presents a new structural design involving detachable electromagnetic coils for developing a combinable magnetic actuation system that can be integrated with inverted microscopes for microrobot research. A maximum magnetic field intensity of 20 mT and uniform working space of 10 mm × 10 mm are achieved by applying coil parameter optimization and the yoke design. Furthermore, a dumbbell microrobot, which is symmetrical along its length axis, and a moon microrobot, which is asymmetric along its length axis, are fabricated and their motion characteristics are compared. The dumbbell microrobot exhibits reversible switching of three motion modes, whereas the motion of the moon microrobot exhibits the obvious drift. These dumbbell and moon microrobots are successfully controlled to move along a square path and a labyrinth path respectively, thus verifying the control performance of the magnetic actuation system.

Design of Uniform Magnetic Field Coil by Quasi-Elliptic Function Fitting Method With Multiple Optimizations in Miniature Atomic Sensors

This article presents a design method of cylindrical uniform field coil based on quasi-elliptic function fitting (EFF) method with multiple optimizations. The EFF method is a type of discrete wire techniques aiming at simplifying the coil structure. Combing with particle swarm optimization (PSO) algorithm, the optimized parameters of EFF coil are obtained for highly uniform magnetic field. To further improve the uniformity of magnetic field in the central space, a new regional points selection optimization method is proposed. The calculation results show that after PSO optimization, the absolute maximum relative error in the target region is optimized to 0.098% by EFF coil comparing with modified single saddle coil (3.08%), nest coil (2.4%), and target field method (TFM) coil (0.11%). After regional points selection optimization, the volume proportion of absolute magnetic field relative error less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1\times 10^{-4}$</tex-math></inline-formula> increases from 35.24% to 54.38% by EFF coil comparing with TFM coil. In addition, the simple EFF coil structure is verified to be easy to process and keep high performance through experiments. As the EFF coil’s high uniformity and simple structure, the new method has important significance for the miniaturization of atomic sensors.

Comprehensive Weldability Criterion for Magnetic Pulse Welding of Dissimilar Materials

Despite its exceptional ability to join dissimilar materials and environmental friendliness, several challenges must be addressed in magnetic pulse welding (MPW). The conventional weldability criterion (i.e., minimum impact velocity) is analytically calculated as a function of material properties without considering the geometry of electromagnetic coil, electrical and physical parameters, making the minimum impact velocity a necessary but not sufficient condition for a sound MPW joint. A new weldability criterion, namely effective impact velocity, is proposed, which overcomes the conventional weldability criterion’s limitations. The effective impact velocity can be inversely modelled to identify shop-floor relevant process parameters and it eliminates the need to fabricate several coils in the process and product proving stages. The proposed approach is demonstrated by a case study on tubular welding of Aluminium and SS304. The weld’s soundness produced with computed process parameters was corroborated by experimental observations on lap shear tests, hardness measurements, optical and scanning electron microscopy, and surface energy dispersive spectroscopy mapping. This investigation is expected to pave the way for developing the process window for MPW of several material combinations, with high cost and time savings.

Dynamic Induction Heating Temperature Field Analysis of Spiral Bevel Gears

Combining tooth surface induction heating and shot peening is an efficient method to improve tooth surface performance. Reasonable designs of the induction coil structure and parameters are essential for achieving uniform and efficient tooth surface heating. In this work, to precisely control the tooth surface temperature field and improve the heat uniformity across the tooth surface, a transverse coil (TC) and a longitudinal coil (LC) were designed, and the gear was set to rotate at a constant speed of 20 r/min, dividing the tooth surface is into a shot-peening area and heating area. Further, dynamic numerical simulations were performed using COMSOL Multiphysics in combination with the uniform rotation of gears to investigate the effect of the coil structure on the temperature field of the outer surface of gears. The results of the analyses combining the effects of different electrical parameters revealed that the gear surface temperature under LC heating was more uniformly distributed in the axial and circumferential directions, the tooth surface temperature fluctuations were smaller, the temperature difference between the root and top of the tooth was smaller, an coil heating was more efficient. Thus, the LC was deemed suitable for use as the spiral bevel gear induction heating coil. Finally, heating experiments were conducted using the LC to validate the simulation model. The results show that the use of LC heating can achieve the research goals of uniform temperature field distribution on the tooth surface and efficient temperature rise, providing the prerequisite for shot peening.

Design of Rogowski Switch-Current Sensor With Offset Compensation for Three-Phase SiC Inverter

This article proposes a Rogowski switch-current sensor (RSCS) with the offset compensation for the current control of the three-phase SiC inverter. The RSCS is built into the four-layer print circuit board (PCB) gate drive board. The coil parameters are analyzed with the Ansys software (Maxwell and Q3D) and then compared with the measurement results. The analog signal processing circuits are implemented with the operational amplifier (op amp) to reconstruct the switch current and the phase current. Unfortunately, the RSCS suffers from the op amp offset voltage and bias current integration, which varies according to the duty cycle and switching frequency. This article proposes an offset compensation software (S/W) to address this issue. Moreover, an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> discharge factor is proposed to make up for the discharging phenomenon of the capacitor in the integrator feedback path. A three-phase SiC inverter prototype is built and tested with the three-phase inductor load to verify the feasibility of the method. Experimental results at 10–30 kHz, 600 V, 150 A show the proposed method to have less than 2% sensing error.

Design and optimization of large-scale single-crystal furnaces asymmetric hooked magnetic fields

The solar photovoltaic power generation industry and large-scale integrated circuit industry put forward higher requirements for the size and quality of monocrystalline silicon. However, there are some problems in the production of large-diameter and high-quality monocrystalline silicon, such as uneven crucible thermal field and strong melt convection, which affect the quality of monocrystalline silicon. Therefore, by adopting the finite element 2D modeling method, this paper established the asymmetric hook magnetic field model of the 40-inch crucible. Hence the key magnetic field parameters affecting the growth of a single crystal were determined by controlling the melt convection in the crucible. Meanwhile, through finite element static magnetic field simulations, the effect of the magnetic field at the crucible wall was analyzed by adding the upper and lower guide rings of the magnetic shield structure, the magnetic shield structure with intermediate permeability ring, and the coil parameters. In addition, the parameters of the asymmetric hooked magnetic field structure were also optimized based on the simulation data. On the above basis, a numerical simulation analysis of the key parameters of the magnetic field was carried out. The simulation results show that the optimized asymmetric hook magnetic field structure can effectively control the melt convection in the crucible. In addition, the magnetic field strength at the crucible wall can meet the target of restraining convection by a magnetic field. Hence, it provides a certain reference value for the design of a large-scale single crystal furnace magnetic field.

Sensing Model for Detecting Ferromagnetic Debris Based on a High-Gradient Magnetostatic Field

Wear debris sensing is an important approach for machine condition monitoring. To date, different types of debris sensors have been developed, among which the magnetostatic inductive debris sensor is preferable for monitoring ferromagnetic debris, but the existing induced voltage model cannot be used to quantify wear debris in lube oil. Accordingly, a modeling method was proposed for the debris sensor based on a high-gradient magnetostatic field. First, a Gaussian curve is used to fit the magnetic field along the axis of the sensor. Then, time-harmonic electromagnetic field analysis and Fourier series decomposition are combined to establish an induced voltage model. Furthermore, the influence of the relative permeability, size, and velocity of wear debris and induction coil parameters on the output voltage is analyzed. The results show a linear relationship between the theoretical calculations and experimental results. Therefore, the proposed model can be used to realize quantitative analysis of wear debris, laying a foundation for optimizing the sensor structure, and extracting features from output voltage signals.

The efficiency of linear electromagnetic vibration-based energy harvester at resistive, capacitive and inductive loads

Abstract Energy harvesters and almost all energy generation devices receive the motivation for design from their efficiency and efficiency play an important role in the feasibility and practicability of the design. In this paper, we investigate the efficiency of electromagnetic vibration-based energy harvesters at various electrical loads. In our problem the efficiency depends on excitation frequency, coil and load parameters as well as electromagnetic coupling coefficient. The author first proves that the input power that the harvester receives from its environment at constant base acceleration and constant excitation frequency is always equal to the power that consumes in electrical and mechanical dampers, then the author defines the resonance frequency and plot three efficiency diagrams i.e. plot of efficiency versus (excitation) frequency, plot of maximum efficiency at a constant frequency versus load and in the end plot of the efficiency versus output power at varying load capacitance and resistance. The author observes that maximum efficiency not only does not occur at resonance (i.e. at maximum power) but also is very low (less than 1e−10%) for typical parameters at resonance. Also the maximum efficiency for typical optimum parameters is around 17.45%.