Magnetic Noise Research Articles

A Progressive Loss Decomposition Method for Low-Frequency Shielding of Soft Magnetic Materials

Energy loss in shielding soft magnetic materials at low frequencies (1–100 Hz) can cause fluctuations in the material’s magnetic field, and the resulting magnetic noise can interfere with the measurement accuracy and basic precision physics of biomagnetic signals. This places higher demands on the credibility and accuracy of loss separation predictions. The current statistical loss theory (STL) method tends to ignore the high impact of the excitation dependence of quasi-static loss in the low-frequency band on the prediction accuracy. STL simultaneously fits and predicts multiple unknown quantities, causing its results to occasionally fall into the value boundary, and the credibility is low in the low-frequency band and with less data. This paper proposes a progressive loss decomposition (PLD) method. Through multi-step progressive predictions, the hysteresis loss simulation coefficients are first determined. The experimental data of the test ring verifies the credibility of PLD’s prediction of the two hysteresis coefficients, improving the inapplicability of the STL method. In addition, we use the proposed method to obtain the prediction results of the low-frequency characteristics of the loss of a variety of typical soft magnetic materials, providing a reference for analyzing the loss characteristics of materials.

Acoustic analysis of a three-dimensional cylindrical shell model under electromagnetic vibration

This paper presents the acoustic analysis of a three-dimensional cylindrical shell model under electromagnetic vibration, a critical factor affecting the performance of electric motors in various applications such as automotive, aerospace, and industrial systems. The study provides a multidisciplinary approach that integrates electromagnetics, structural vibration, and acoustics, solved using the fast multipole boundary element method (FMBEM). The results summarize the validation of the analytical models and numerical simulations, offering insights into effective vibration reduction methods. The conclusions indicate that the 3-D numerical analysis using FMBEM aligns well with the analytical solution for the sound pressure in the exterior acoustic domain of the cylindrical shell model. The paper contributes valuable insights for the design of low-noise motors and the control of electromagnetic vibration and noise in electric motors.

Research on the Sensing Properties and Vibration Reduction Performance of Self-Sensing Self-Tuning Magnetic Fluid Damper

Abstract The semi-active control damping system has gained popularity due to its quick response time and versatility. However, external sensors are susceptible to environmental interference, affecting system reliability and increasing complexity and maintenance costs, restricting their use. To address this, a self-sensing self-tuning magnetic fluid damper is proposed. The vibration-measuring induction coil is wound on the damper to sense the magnetic fluid vibration information in real time, and the vibration signal is communicated to the self-tuning control circuit. The control circuit calculates and determines the dominant frequency of structural vibration, then outputs the relevant current signal to set the damper's natural frequency to track the excitation frequency, resulting in self-tuning vibration reduction. First, the self-sensing unit's output induced electromotive force model is created, followed by an expression of the damper's natural frequency, indicating that the self-sensing unit can achieve self-tuning vibration reduction by tracking the excitation frequency. The multi-field coupling simulation model of the magnetic fluid damper is generated, and the induction coil coupling mode and damper excitation angle are defined to obtain the maximum induced voltage.
Finally, an experimental platform was developed to assess the damper's self-sensing and self-tuning vibration reduction performance. The experimental results demonstrate that the suggested self-tuning magnetic fluid damper exhibits excellent self-sensing capabilities and effectively reduces vibrations. This offers an innovative research concept for using magnetic fluid in self-sensing technology and vibration reduction domains.

Research on Radial Vibration Model and Low-Frequency Vibration Suppression Method in PMSM by Injecting Multiple Symmetric Harmonic Currents

Driven by frequency conversion, the windings of a three-phase permanent magnet synchronous motor (PMSM) contain both odd and even harmonic currents. Due to the motor’s pole–slot conductance modulation, the interaction between the magnetic fields generated by these harmonic currents and the permanent magnet field results in harmonic radial vibrations of the motor. This paper analyzes the three-phase currents of the prototype and derives the radial magnetomotive force (MMF) spatiotemporal models for symmetric harmonic currents. By integrating Maxwell’s magnetic force formula and vibration response formula, the radial vibration models for symmetric harmonic currents are developed. The characteristics of vibrations caused by odd and even harmonic currents, as well as positive sequence and negative sequence harmonic currents, are analyzed separately. A cyclic sequence, low-frequency vibration suppression control method incorporating multiple harmonic current injections was designed. Experimental results of this method are compared with those obtained using an ideal sinusoidal current. Except for the second harmonic vibration, all other vibrations are significantly suppressed, with a maximum suppression rate of 92.28%. The total vibration level is reduced by 12.7619 dB, and the average torque is reduced by 0.67% with the total harmonic distortion of the current at 2.89%. The experimental results show that the vibration method in this paper has little influence on the average torque of the motor, the current distortion rate is small, and the vibration suppression effect is good.

Enhancement of Magnetic Shielding Based on Low-Noise Materials, Magnetization Control, and Active Compensation: A Review

Magnetic-shielding technologies play a crucial role in the field of ultra-sensitive physical measurement, medical imaging, quantum sensing, etc. With the increasing demand for the accuracy of magnetic measurement, the performance requirements of magnetic-shielding devices are also higher, such as the extremely weak magnetic field, gradient, and low-frequency noise. However, the conventional method to improve the shielding performance by adding layers of materials is restricted by complex construction and inherent materials noise. This paper provides a comprehensive review about the enhancement of magnetic shielding in three aspects, including low-noise materials, magnetization control, and active compensation. The generation theorem and theoretical calculation of materials magnetic noise is summarized first, focusing on the development of spinel ferrites, amorphous, and nanocrystalline. Next, the principles and applications of two magnetization control methods, degaussing and magnetic shaking, are introduced. In the review of the active magnetic compensation system, the forward and inverse design methods of coil and the calculation method of the coupling effect under the ferromagnetic boundary of magnetic shield are explained in detail, and their applications, especially in magnetocardiography (MCG) and magnetoencephalogram (MEG), are also mainly described. In conclusion, the unresolved challenges of different enhancement methods in materials preparation, optimization of practical implementation, and future applications are proposed, which provide comprehensive and instructive references for corresponding research.

Comparative investigation and nonlinear characterization of multi-stable electromagnetic vibration energy harvesters

Comparative investigation and nonlinear characterization of multi-stable electromagnetic vibration energy harvesters

Research on Electromagnetic Vibration and Noise of PMSM with Unconventional Stator

Research on Electromagnetic Vibration and Noise of PMSM with Unconventional Stator

Characterization of Heat-treated Bearing Rings via Measurement of Electromagnetic Properties for Pulsed Eddy Current Evaluation

Nondestructive evaluation of heat-treated bearing rings is a critical technique for quality control in industries. However, there are few reports addressing the complex mapping between hardness and electromagnetic properties due to the intricate changes in the microstructure. This paper proposes a dual-method approach, combining magnetic saturation eddy current techniques and Barkhausen noise reconstruction hysteresis loop techniques, to independently establish the relationship between hardness and electromagnetic properties. The results show that the electrical properties of unqualified specimens are significantly higher than those of other specimens, with qualified specimens have slightly higher properties than untreated ones. Additionally, an inverse relationship between hardness and magnetic properties is observed. Based on the obtained electromagnetic parameters, a pulsed eddy current hardness detection simulation model is established, which has the potential to improve purely data-driven methods for hardness detection in deep learning.

An Improved Conformal Mapping Method for Electromagnetic Vibration Analysis in PMSMs With Rotor Eccentricity

An Improved Conformal Mapping Method for Electromagnetic Vibration Analysis in PMSMs With Rotor Eccentricity

Enhanced detection performance based on a differential ME sensor with strong suppression of vibration interference

Magnetoelectric (ME) sensors have enormous potential for detecting weak magnetic fields because of their high sensitivity, low power consumption, compact size and, low cost. However, inevitable vibration interference limits their application in practical environments, especially in the case of mobile platform mounting. Here, we propose a differential ME sensor, consisting of PZT macro-fiber composites (MFCs) and Metglas laminates. The differential ME sensor has two output terminals with weak mutual mechanical coupling and works in longitudinal vibration mode. MFC cores are polarized in parallel mode to guarantee their consistency of electric characteristics and reversed bias field is provided by attached magnets. Experimental results show that the differential-mode response amplitudes have a gain of −17.6 dB for low-frequency vibration at 2 Hz and ∼6.2 dB for an applied magnetic field at 3 Hz, in comparison with the single-ended mode. In addition, our proposed ME sensor also has a low inherent equivalent magnetic noise of 18.3 pT/√Hz at 1 Hz. Finally, a target detection experiment in the presence of heavy lab noise and strong vibration interference is conducted and the improved detection performance of the proposed differential ME sensor is proved.

Methods in fluctuation (noise) spectroscopy and continuous analysis for high-throughput measurements

Abstract Fluctuation (noise) spectroscopy is widely used to investigate the low-frequency dynamics of charge carriers in condensed-matter systems, aiming to (i) improve the performance of micro- and nanoscale electronic devices and sensors, and (ii) use ‘noise as a signal’ in order to fundamentally investigate the microscopic motion and transitions of charge carriers coupled to the low-lying excitations in solids. Here, we focus on measurements of the ubiquitous 1 / f -type fluctuations, often composed by a superposition of (independent or correlated) two-level systems each giving rise to a Lorentzian spectrum, denoted random telegraph noise in the time domain. We briefly review the basic concepts of noise and fluctuations and give a comprehensive overview of state-of-the-art measuring techniques, using both commercially available signal analyzers and custom software in order to perform the spectral analysis of the recorded time signals, and critically evaluate their advantages and drawbacks. We describe how to use fast data acquisition devices in a cross-correlation setup providing additional quantitative information on the magnitude of uncorrelated instrument noise, and demonstrate the mathematical intricacies of extracting the noise spectra. We introduce a new method for high-throughput measurements by automated spectral analysis based on the concept of Continuous Analysis. We demonstrate the potential of this technique, working towards a FAIR data workflow, by measurements of magnetic flux noise within the hysteresis loop of ferromagnetic nanostructures.

Stress Evaluation of Ferromagnetic Materials Based on a New Barkhausen Noise Sensor Composed by High Entropy Alloy Magnetic Core

Abstract During the service of ferromagnetic structural steel materials, stress should be evaluated accurately. Although the magnetic Barkhausen noise (MBN) testing has the ability to sense stress, it can be easily interfered with by environment. In this paper, a new MBN sensor is fabricated by selecting FeCoNi(AlMn)0.25 high entropy alloy (HEA) as the case of magnetic core to improve the accuracy of stress evaluation. The process optimization results show that the stability of MBN signal characteristics is the largest when the excitation frequency is 4 Hz and the voltage is 6 V. The signal-to-noise ratio of MBN indicates that the HEA and Ni-Zn ferrite probes have better anti-interference capability. The MBN signal characteristic values peak voltage and root mean square measured by the HEA probe can linearly quantify the stress level with higher efficiency, stability, and accuracy. The underlying reason of high sensitivity of HEA probe to the variation of MBN signals is revealed based on the magnetic properties. The microstructure and the thermodynamic parameters are analyzed to clarify whether the additions of Al and Mn atoms can affect the short-ranged magnetic exchange interaction and lattice distortion, which affects the magnetization behavior of HEA. Finally, the availability of MBN sensor with HEA magnetic core to the stress evaluation on the retired slide rails of car seats is conducted, which demonstrates its great application value.

Disparities in screening and risk stratification for hispanic adults with metabolic dysfunction-associated steatotic liver disease.

Cut-points for non-invasive tests (NITs) for risk stratification in metabolic dysfunction-associated steatotic liver disease (MASLD) were derived from predominantly non-Hispanic populations. It is unknown if these cut-points perform adequately in Hispanic individuals. We assessed the performance characteristics of current NIT cut-points among Hispanic patients and determined whether they could be further optimized. We prospectively enrolled 244 adults with biopsy-proven MASLD. Participants underwent a research visit with magnetic resonance elastography (MRE) and vibration controlled transient elastography (VCTE). Histology and imaging assessments were conducted centrally. Diagnostic performance was evaluated by area under the receiver-operating curve (AUROC) and optimal cut-points were identified by Youden J analysis. The mean (±SD) age and body mass index were 52.6 (±13) and 31.6 (±4.6) kg/m2. Overall, 40% had diabetes, 31% (N=75) were Hispanic. 40% of Hispanic and 28.4% of non-Hispanic patients had significant fibrosis. To detect significant fibrosis, MRE and VCTE exhibited significantly lower accuracy in Hispanic versus non-Hispanic participants (AUROC: MRE, 0.87 vs. 0.98, p=0.01; VCTE, 0.78 vs. 0.92, p=0.02). Clinical care algorithms yielded high false-negative rates among Hispanic participants (14% with low-risk FIB-4 and 21% with low-risk VCTE had advanced fibrosis on biopsy). Cut-points of 2.73kPa for MRE and 6.9kPa for VCTE were optimal to detect significant fibrosis in Hispanic individuals. Findings were validated in a Latin American cohort. Lower NIT cut-points may be needed to optimize surveillance for significant fibrosis due to MASLD in Hispanic populations commensurate with their higher burden and severity of disease.

Analysis and measurement of magnetic noise for tesla shielding based on superconducting coils applied to SERF magnetometer

Tesla Shielding (TS) is closed superconducting coils composed of superconducting tape, designed to resist changing magnetic fields, thereby achieving magnetic shielding. TS, optically transparent, is suitable for integration with spin exchange relaxation-Free (SERF) magnetometers, thereby improving the sensitivity of SERF magnetometers. However, no prior research has been conducted on the magnetic noise of TS. Noise source identification was conducted on the superconducting tapes used in the TS. We modeled the magnetic noise of superconducting coils, analyzed the the relationship between geometric parameters and magnetic noise of coils, and proposed methods to suppress magnetic noise. Finally, we established a measurement system to measure the magnetic noise of superconducting coils. The results confirm the feasibility of the magnetic noise calculation model and the effectiveness of the methods for suppressing magnetic noise. This study can guide the design of TS, which is important for improving the sensitivity of SERF magnetometers.

Assessing the Temperature-Dependent Characteristics of Warm-Rolled EN8 Steel through Magnetic Barkhausen Noise Technique and Predictive Modeling with Voting Regression Technique

Assessing the Temperature-Dependent Characteristics of Warm-Rolled EN8 Steel through Magnetic Barkhausen Noise Technique and Predictive Modeling with Voting Regression Technique

Hyperfine-Enhanced Gyroscope Based on Solid-State Spins.

Solid-state platforms based on electronuclear spin systems are attractive candidates for rotation sensing due to their excellent sensitivity, stability, and compact size, compatible with industrial applications. Conventional spin-based gyroscopes measure the accumulated phase of a nuclear spin superposition state to extract the rotation rate and thus suffer from spin dephasing. Here, we propose a gyroscope protocol based on a two-spin system that includes a spin intrinsically tied to the host material, while the other spin is isolated. The rotation rate is then extracted by measuring the relative rotation angle between the two spins starting from their population states, robust against spin dephasing. In particular, the relative rotation rate between the two spins can be enhanced by their hyperfine coupling by more than an order of magnitude, further boosting the achievable sensitivity. The ultimate sensitivity of the gyroscope is limited by the lifetime of the spin system and compatible with a broad dynamic range, even in the presence of magnetic noise or control errors due to initialization and qubit manipulations. Our result enables precise measurement of slow rotations and exploration of fundamental physics.

Enhancing Mechanical Characteristics of LM9 Aluminum Alloy by Optimization of Electromagnetic Vibration Analysis

Enhancing Mechanical Characteristics of LM9 Aluminum Alloy by Optimization of Electromagnetic Vibration Analysis

Concept of Electromagnetic inerter-based vibration absorbers

Inerter is a device that generates a force proportional to the relative acceleration between its two terminals. It has recently been shown that this unusual property can offer interesting advancements and performance in the realm of vibration isolation or dynamic absorbers. However, the main developments have encountered difficulties in mechanical implementation (utilizing rotating discs and gears) or achieving high-frequency efficiency. The present study proposes to synthesize actively the dynamical behavior of an inerter in order to overcome these constraints. To address the stability issue, collocated voice coils are employed as sensors and actuators at the interface of the moving masses of the device. In a case study of a hybrid tuned vibration absorber, a first experimental demonstration illustrates the feasibility of such a concept.

Torque Ripple and Electromagnetic Vibration Suppression of Fractional Slot Distributed Winding ISG Motors by Rotor Notching and Skewing

Torque Ripple and Electromagnetic Vibration Suppression of Fractional Slot Distributed Winding ISG Motors by Rotor Notching and Skewing

Simulation of pulse width modulation strategies: validation based on sound quality evaluations

Though the noise emitted by an electrical machine is less loud than the one from a combustion engine, the existing literature shows it is not always more pleasant. This is because of its strong tonal content, due to deterministic excitations (e.g. electromagnetic slotting and switching effects, mechanical gear mesh effects). The main source of magnetic noise is the radiation of the stator submitted to electromagnetic forces, which are harmonic by nature. Their highest frequency components are generated by the Pulse Width Modulation (PWM) technique designed to vary the supply frequency and operating speed of the electric machine. Several PWM strategies exist, leading to specific harmonic spectra. A temporal simulation model has been developed to auralize the corresponding electromagnetic noise emitted by the machine, considering its mechanical and electrical parameters. A testbench has been adapted to test the relevance of the model, both from an electrical and acoustic point of view. The simulation model and the testbench can be used to generate virtual and real sound stimuli to be assessed in a jury testing. The subjective evaluations allow to assess the relevance of the auralization model, but also to identify the least annoying strategies.