Magnetic Coupling Model Research Articles

Research on charging monitoring method for lithium-ion batteries based on magnetic field sensing

With the rapid and continuous development of new energy vehicles, safety issues during charging have become increasingly prominent. Thus, there is an urgent need to strengthen charging safety management. However, current charging detection methods have limitations, such as difficulty in monitoring local battery pack currents, and indirect monitoring through temperature and gas sensors lead to lag. To address these limitations, this article proposes a safety monitoring method based on an improved lithium-ion battery magnetic field sensing model that covers the entire charging process. Specifically, thermal field analysis was introduced to the existing electric magnetic coupling model, resulting in an electric thermal magnetic multi-physical field coupling model. By conducting experiments, the study verified that the accuracy of the improved model has increased by 15.5 %. Based on this model, the study proposed a method for predicting and warning of abnormal currents using BP neural network and mathematical statistical laws. The results showed that the current prediction accuracy of this method reached 96.4 %. Such high accuracy ensures real-time comprehensive monitoring of the current information of lithium-ion battery packs, thereby eliminating the hidden dangers of charging safety accidents caused by the lack of local current detection.

Method for improving accurate measurement of the magnetic field of wireless passive micro-magnetic stimulator micro-coil

In recent years, the wireless passive micro-magnetic stimulator (WP-μMS) has emerged as a focal for implantable neuromagnetism modulation research. However, accurately measuring the magnetic field strength of the micro-coil presents a significant challenge due to its small size and low mutual inductance (M). Firstly, this paper establishes a theoretical model of magnetic coupling with a three-stage structure of transmitting coil-micro-coil-detecting coil. The calculation method of detecting the coil to measure the magnetic field is determined by calculating the M between each pair of coils. Secondly, the magnetic coupling resonance method enhances the measured value M to the nH-scale. This approach also eliminates the influence of the M between the transmitting coil-detecting coil on the measurement of the transmitting coil-micro-coil M, thereby achieving accurate measurement of the mT-scale magnetic field strength of the WP-μMS micro-coil. Finally, the effectiveness of the measured mT-scale magnitude magnetic stimulation is validated biologically.

Structure optimization design and magneto-mechanical characteristics analysis of amorphous alloy with oriented silicon steel composite wound core

Three-dimensional wound cores are widely used in three-phase distribution transformer due to the symmetrical magnetic circuit structure. Amorphous alloy and oriented silicon steel are two kinds of ferromagnetic materials commonly used to make distribution transformer cores, each has own advantages and disadvantages in magnetic and mechanical characteristics. The amorphous alloy and oriented silicon steel composite core can synthesize the advantages of both. In this paper, a double-layer composite wound core (DCWC) structure is proposed and the corresponding dual nonlinear electric circuit and magnetic circuit coupling model is established. A structure optimization design method for the DCWC based on the free parameter scanning method is proposed by taking the percentage of oriented silicon steel in the composite core and the structure parameters as free variables. Based on the proposed optimization design method, a DCWC is designed and the experimental prototypes are manufactured. Further, the flux density distribution, core loss and mechanical vibration displacement of the DCWC are analyzed, and the effectiveness of the proposed method is verified by comparing with the measured results.

Magnetic coupling properties of multiple metal wear particles for high-precision electromagnetic debris detection applications

The electromagnetic wear particle detector is one of effective method to monitor wear debris in lubricating oil for assessing the wear condition of mechanical equipment. However, the motion of wear particles, especially the aggregation behavior in both fluid field and magnetic field, may make the particle detector generate false wear signals. Therefore, to estimate the impact on the detection accuracy of wear debris by the particle aggregation effect, the magnetic coupling model of multiple wear particles is established for studying the magnetic coupling effect between adjacent metal particles. The research results show that the effect changes the total magnetic energy variation induced by the particles and then affects the amplitude of particle signal. Meanwhile, the variation degree is closely associated with the frequency of magnetic field of particle detectors. Overall, the aggregation of wear particles with the same magnetic properties (both ferromagnetic or non-ferromagnetic) leads to false alarms of particle detectors; and the aggregation of wear particles with different magnetic properties causes missing alarms of particle detectors. Meanwhile, increasing the field frequency may increases the probability of missing alarm failure of particle detectors.

Precise Modeling and Design of Self-Resonant for High-Efficiency Mid-Range Wireless Power Transfer System

Transfer power and efficiency of wireless power transfer (WPT) systems are limited by the quality factor and coupling coefficient of the transmitting (Tx) coil and receiving (Rx) coil. Getting rid of compensation circuits, self-resonant coils have simple structure, high system reliability, high quality factor and high power level, making it a promising candidate for WPT applications. In modeling and computation of self-resonant coils, the results derived from the transmission line theory have obvious errors, and the finite element simulation takes a long computing time. For obtaining accurate results and achieving fast computation, a partial-element equivalent circuit (PEEC) method is applied to calculate the self-resonant frequency (SRF) and the current distribution of helical coils. To validate the accuracy of the proposed model, some prototypes were simulated and measured. The theoretical calculation predications are in great agreements with the simulation and measurement results. The magnetic coupling model between Tx and Rx is also established using PEEC method and a novel design guideline of self-resonant helical coils is proposed. Furthermore, a WPT system with 6.78MHz selfresonant helical coils was designed, fabricated and tested for a high-efficiency mid-range energy transfer. It was used to drive a 5W load wirelessly as a demonstration to validate the feasibility of the proposed system in practical applications.

MFA-MTJ Model: Magnetic-Field-Aware Compact Model of pMTJ for Robust STT-MRAM Design

The popularity of perpendicular magnetic tunnel junction (pMTJ)-based spin-transfer torque magnetic random access memories (STT-MRAMs) is growing very fast. The performance of such memories is very sensitive to magnetic fields, including both internal and external ones. This article presents a magnetic-field-aware compact model of pMTJ, named the MFA-magnetic tunnel junction (MTJ) model, for magnetic/electrical co-simulation of MTJ/CMOS circuits. Magnetic measurement data of MTJ devices, with diameters ranging from 35 to 175 nm, are used to calibrate an in-house magnetic coupling model. This model is subsequently integrated into our developed compact pMTJ model, which is implemented in Verilog-A. The superiority of the proposed MFA-MTJ model for device/circuit co-design of STT-MRAM is demonstrated by simulating a single pMTJ as well as STT-MRAM full circuits. The design space is explored under PVT variations and various configurations of magnetic fields.

Multi-Crack Dynamic Interaction Effect on Oil and Gas Pipeline Weld Joints Based on VCCT

In pipelines for transporting oil and gas, multiple cracks often exist in weld joints. The interaction among the cracks should be considered as it directly affects the life span of the pipeline structures. In the current investigation, based on the fluid–solid magnetic coupling model, the virtual crack-closure technique (VCCT) is applied to systematically study the multi-crack dynamic interaction effect on pipeline welds during the crack propagation process. The results show that the existence of an auxiliary crack accelerates the main crack’s propagation. When the auxiliary crack is nearer to the main crack tip, the enhancement effect of the auxiliary crack on the main crack increases. Further, when the initial length of the auxiliary crack increases, the main crack becomes easier to propagate. Two important parameters, the distance between the two interacting crack tips and the initial size of the auxiliary crack, are studied in detail. Their interference effect on the main crack has been quantified, which is very user-friendly for engineers to conduct failure assessment and prevention for oil and gas pipes with multiple cracks at weld joints.

Design of Highly Uniform Field Coils Based on the Magnetic Field Coupling Model and Improved PSO Algorithm in Atomic Sensors

The coupling between the coil and the cylindrical magnetic shield (CMS) in atomic sensors not only results in the inconsistency of the coil constant with the theory but also deteriorates the uniformity, which affects the sensor performance. To solve the above deficiencies, a design method of highly uniform field coils inside the CMS based on the coupling model with finite permeability and thickness and particle swarm optimization (PSO) with dynamic inertia weights is proposed for the first time. The coupling model of the coil inside the CMS is established by Green’s function method (GFM). Then it is combined with the nonlinear optimization method, and the coil configuration is optimized by the dynamic inertia weight PSO to obtain the optimal parameters. It not only reduces the calculation error of the model, but also improves the uniformity. Comparing this work with the Lee-Whiting coil inside a CMS, the theoretical uniformity is further improved by 2 orders of magnitude, and measured uniformity errors in the target region reach 1.404×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , and 2.317×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , respectively. The correctness and effectiveness are proved by finite element simulation and experimental results. The accuracy and uniformity of coils can be considerably improved, which is beneficial to further improve the measurement sensitivity of instruments related to magnetic field uniformity.

Calculation and experimental verification of force-magnetic coupling model of magnetised rail based on density functional theory

Metal magnetic memory (MMM) is a widely used non-destructive electromagnetic detection technology. However, the analysis of its underlying principle is still insufficient. The mechanical and magnetic coupling model is a reasonable standpoint from which to study the principle of MMM. In this paper, a mechanical and magnetic coupling model of steel material is established based on density functional theory (DFT) using the CASTEP first-principles analysis software. In order to simulate the practical working environment, the residual magnetism in the rail is assumed to change with the stress on the rail. By applying different stresses to the model, the relationship between the atomic magnetic moment, the lattice constant and stress is explored, as well as the causes of magnetic signals in the stress concentration zone. It is revealed that the atomic magnetic moment and the crystal volume decrease with the increase in compressive stress. The magnetic signal on the surface of the magnetised metal component decreases with the increase in compressive stress, while the tensile stress shows the opposite tendency. Generally speaking, the change in atomic magnetic moment and crystal volume caused by lattice distortion under stress can be seen as the fundamental reason for the change in magnetic signal on the surface of the magnetised metal. The bending experiment of the rail shows that the normal magnetic field decreases with the increase in compressive stress in the stress concentration zone. The conclusion is verified by experiments.

Spacer layer thickness and temperature dependence of interlayer exchange coupling in Co/Ru/Co trilayer structures

In this paper, we measure the bilinear interlayer magnetic coupling ${J}_{1}$ between two Co layers coupled across a Ru spacer layer over a wide range of spacer layer thicknesses from 0.4 to 3.4 nm and temperatures from 5 to 300 K. These measurements are fit using the interface-reflection interlayer magnetic coupling model in order to determine coupling strengths and electron Fermi velocities within the spacer layer in the direction perpendicular to the film interface for each of the critical spanning vectors. We find that there is a significant contribution to ${J}_{1}$ from several different critical spanning vectors, all with different periods of oscillation with respect to the spacer layer thickness. The results indicate that there is likely no exponential superexchangelike contribution to coupling in our samples. The nonoscillatory antiferromagnetic coupling bias of ${J}_{1}$ seen in thinner Ru spacer layers can be explained solely by a linear combination of oscillatory Ruderman-Kittel-Kasuya-Yosida-like coupling from several different critical spanning vectors, all with different periods of oscillation. The experimentally determined electron Fermi velocities are found to be within the range expected from theoretical calculations. The results also indicate that the interface-reflection model is capable of describing the bilinear interlayer exchange coupling in our samples over the entire range of spacer layer thicknesses and temperatures measured in this paper.

State-of-the-art of magnetic memory testing technique

Magnetic memory testing is a new nondestructive testing technique. It has the incomparable advantages of traditional nondestructive testing technique, and can find the stress concentration of ferromagnetic materials. In this paper, the development of magnetic memory testing is analysed, and the problems encountered in the development of magnetic memory is studied. The research on magnetic memory mainly focuses on the following three aspects, study on the mechanism of mechanical magnetic coupling, analysis of external influence factors of signal and extraction of damage evaluation parameters. Finally, in the paper, the development direction of magnetic memory testing in the future is summarized. That is, to strengthen the research on the micro mechanism of magnetic memory and to establish the correct mechanical magnetic coupling model.

A new mechanical and magnetic coupling model of magnetic memory

Magnetic memory testing is a new nondestructive testing technology, which can detect the early damage of ferromagnetic components such as stress concentration. In this paper, the coupling model between the stress of ferromagnetic material and its magnetic leakage field is established. In this model, the relative change rate of permeability of ferromagnetic material is proportional to the stress, the change of permeability and the saturation magnetic induction. The experimental results show that the model can well describe the relationship between stress and leakage magnetic field.

Effect of series/parallel circuits of eccentric switched reluctance motor on vehicle ride comfort

The switched reluctance motor (SRM) drives are emerging as an attractive solution for electric vehicle (EV) applications due to its favorable driving capacity. However, the inherent net radial force of SRM has an important effect on the vehicle ride comfort. This paper investigates the influences of net radial force induced by eccentric SRM with series/parallel circuits on vehicle ride comfort. The mechanical–electrical–magnetic coupling model of SRM is established by combing the numerical simulation and analytical method, in which the series and parallel circuits are structured, respectively. Then, quarter vibration vehicle models coupled with SRM are established. The net radial force of the two SRMs and ride comfort of the corresponding vehicles are simulated and discussed at different conditions. It is concluded that the SRM with parallel circuits generates smaller net radial forces, and the vehicle driven by SRM with parallel circuits will achieve better ride comfort due to the difference of branch currents.

Equivalent circuit method for Mu‐Negative‐Magnetic and Mu‐Near‐Zero metamaterials in wireless power transfer system

The application of the metamaterial (MM) in wireless power transfer (WPT) system has received a great deal of attention in improving the transfer efficiency and reducing the leakage of electromagnetic field (EMF) in recent years. However, most of the analytical methods for MM-inspired WPT system are based on microwave technologies, such as negative refraction effect, magnetic dipole coupling model and magneto-inductive wave theory. In this study, the equivalent circuit model of the MM in the WPT system is analysed in detail. Two different types of MMs, Mu-Negative-Magnetic (MNM) and Mu-Near-Zero (MNZ), are constructed to verify this method. In particular, a tuning strategy by changing the distances between the drive (load) loop and internal coils is established to improve the power transfer efficiency for the WPT system with the MNM-MM. In addition, the MNZ-MM is described to cancel EMF leakage in the WPT systems by this method. Moreover, a series of practical experiments are carried out to prove the numerical analysis, which are well consistent with the theoretical solution employed by the Advanced Design System software. Finally, the combination of two types of MMs applied in the WPT system is also discussed.

Internal magnetic field tests and magnetic field coupling model of a three-coil magnetorheological damper

Magnetorheological damper is a typical semi-active control device. Its output damping force varies with the internal magnetic field, which is a key factor affecting the dynamic performance of the magnetorheological dampers. Existing studies about the magnetic field of magnetorheological dampers are limited to theoretical analysis; thus, this study aims to experimentally explore the complicated magnetic field distribution inside the magnetorheological dampers with multiple coils. First, the magnetic circuit of a three-coil magnetorheological damper was theoretically analyzed and designed, and the finite element model of the three-coil magnetorheological damper was set up to calculate the magnetic induction intensities of the damping gaps in different currents and numbers of coil turns. A three-coil magnetorheological damper embedded with a Hall sensor was then manufactured based on the theoretical and finite element analysis, and internal magnetic field tests under different conditions were carried out to obtain the actual magnetic induction intensities. At last, the magnetic field coupling model of the three-coil magnetorheological damper was proposed by introducing a coupling coefficient to describe the complex magnetic field distribution due to the strong coupling effect of the three coils, and the results calculated by the proposed model agreed well with the finite element analysis and magnetic field test data. The proposed model lays a foundation for the optimal design of the magnetic circuit and the mathematical model of multi-coil magnetorheological dampers.

Modeling the Resonance Shifts Due to Coupling Between HTS Coils in NMR Probes

Nuclear magnetic resonance (NMR) probes using thin-film HTS coils offer high sensitivity and are particularly suitable for small-sample applications. Typically, HTS probes are optimized for the detection of multiple nuclei and require several coils to be located within a small volume near the sample. Coupling between the coils shifts coil resonances and complicates coil trimming when tuning HTS probes. We have modeled the magnetic coupling between the coils of a 1.5-mm all-HTS NMR probe with 13C, 1H, and 2H channels. By measuring the magnetic coupling coefficients between individual coils, we solve the general coupling matrix given by KVL for six coupled resonators. Our results indicate that required trims can be accurately predicted by applying single coil trimming simulations to this magnetic coupling model. Use of the magnetic coupling model significantly improves the efficiency of tuning HTS probes.

S = 3 Ground State for a Tetranuclear MnIV4O4 Complex Mimicking the S3 State of the Oxygen-Evolving Complex.

The S3 state is currently the last observable intermediate prior to O-O bond formation at the oxygen-evolving complex (OEC) of Photosystem II, and its electronic structure has been assigned to a homovalent MnIV4 core with an S = 3 ground state. While structural interpretations based on the EPR spectroscopic features of the S3 state provide valuable mechanistic insight, corresponding synthetic and spectroscopic studies on tetranuclear complexes mirroring the Mn oxidation states of the S3 state remain rare. Herein, we report the synthesis and characterization by XAS and multifrequency EPR spectroscopy of a MnIV4O4 cuboidal complex as a spectroscopic model of the S3 state. Results show that this MnIV4O4 complex has an S = 3 ground state with isotropic 55Mn hyperfine coupling constants of -75, -88, -91, and 66 MHz. These parameters are consistent with an αααβ spin topology approaching the trimer-monomer magnetic coupling model of pseudo-octahedral MnIV centers. Importantly, the spin ground state changes from S = 1/2 to S = 3 as the OEC is oxidized from the S2 state to the S3 state. This same spin state change is observed following oxidation of the previously reported MnIIIMnIV3O4 cuboidal complex to the MnIV4O4 complex described here. This sets a synthetic precedent for the observed low-spin to high-spin conversion in the OEC.

Application Research on Magnetic Coupling Stress Testing Technique for In-service Steel Bridge

Magnetic effect of ferromagnetic materials was discussed, the magneto-mechanical properties of ferromagnetic materials were studied, as well, Jiles Atherton constitutive mode was studied. Through the establishment of concrete filled steel tubular arch bridge structure calculation model, analysis the boom in tension and compression of the magnetic coupling. Results show that the resultant magnetic coupling model of Q345 steel derrick, the boom and load changes, the change of the magnetic parameters is more sensitive, can be better applied to the stress testing of such components.

Non-invasive pressure measurement based on magneto-mechanical effects

This paper proposes and experimentally demonstrates a non-invasive pressure measurement method based on magneto-mechanical effects. The relative permeability–stress curve is obtained using the J–A force magnetic coupling model, then imported into a finite element simulation model based on the coupled multiphysics of mechanical mechanics and static magnetics. The magnetic variations versus the pressure changes at the periphery of a pressure vessel are obtained through simulations and multi-channel magnetic measurement experiments. The proposed method shows good linearity in the range of 0–3 MPa, and is more sensitive for smaller, thinner vessels. Overrange measurement can lead to saturation. Measurement points need to be carefully chosen in order to achieve the highest sensitivity and precision. The highest sensitivity achieved is 1.314 , and the readily available sensitivity is about 5.0 . The precision in many cases is better than 0.1 MPa. The repeatability errors for the three components are about 2.7% of the full scale when referred to the most sensitive component. The measurement fluctuation over 48 h is 0.1 MPa when referred to the readily available sensitivity.

The characteristics of studying high speed motorized spindle dynamic magnetic coupled

The vibration of high speed motorized spindle directly influences the processing quality; through the finite element method, the dynamic magnetic coupling model of high speed motorized spindle rotor system is established. The coupling relationship between the field parameters of electromagnetic and the characteristics of dynamic are considered. At the same time, the influence of electromagnetic coupled on the dynamic vibration characteristics of the rotor system is analysed and the experimental verification is carried out. The results indicate the stator and rotor magnetic density, the magnetic field energy distribution about motorized spindle are also periodic. The skin effect of magnetic field and air gap eccentricity have great influence on radial vibration. With the increase of speed, the centrifugal force of the bearing is increasing; the softening effect of bearing stiffness is obvious; the natural frequency is decreasing; the amplitude of vibration is increasing. The experimental results are in good agreement with the simulation results. The accuracy of the dynamic magnetic coupling model is illustrated.