Electromagnetic Excitation Research Articles

Analysis and suppression of in-wheel motor electromagnetic excitation of IWM-EV

The in-wheel motor (IWM) driving system has potential applications in electric vehicles (EV) due to its high integration and controllability. However, the IWM electromagnetic excitation, which acts on the wheels, can produce negative vibration and noise issues. This paper investigates the influence of electromagnetic excitation and suppression methods. An integrated model considering the electromagnetic excitation, including the suspension system, the driving system, and the IWM system, is established and developed. A motor speed control system, which includes the acceleration and the motor braking conditions, is designed, and the characteristics of the electromagnetic excitation on the integrated model are analyzed. An active suspension model with uncertain parameters is established, and a controller based on the [Formula: see text] synthesis algorithm is developed to improve the dynamic performance of the electric vehicle. Simulation results show that the [Formula: see text] synthesis controller can significantly reduce the electromagnetic excitation of the motor by suppressing the air gap eccentricity of the IWM. Simultaneously, the [Formula: see text] synthesis controller can also improve the vehicle comfort and the road holding of the electric vehicle. For IWM-EV, the proposed modeling method can accurately describe the dynamic characteristics of IWM, and the designed controller can effectively suppress the vibration problem of IWM-EV.

Nonintrusive honey fraud detection and quantification based on differential radiofrequency absorbance analysis

Features reflecting the dielectric properties of matter are used as proxies during chemical and physical analysis, including food fraud detection and quantification. Typically, these are computed from responses to high-energy electromagnetic excitations traversing samples under test. In this work, differential absorbance levels were measured on pure and adulterated honey samples, from low-power radio-frequency waves. Systematic patterns found are reported along with a novel method and index, devised to address honey fraud detection and quantification. Method and setup were designed to serve as a proof of concept for a novel, rapid, non-destructive, portable family of devices. Performance was evaluated on samples prepared on 4 honey types and 5 adulterants, the most referred for this task, operating in the 1.85–3.25 GHz range. Results validated the proposed method and setup. AUROC>0.99 was achieved by the single-target adulterant detector, adjusted R2 >0.8 by the two-target concentration estimator.

Experimental Investigation of a Nonlinear Energy Storage Effect due to High Power Electromagnetic Excitation

Abstract. The susceptibility of interference victims can significantly be influenced by the presence of nonlinear circuit elements. In addition to the well known occurrence of intermodulation-frequencies, other effects can be observed as well. Recently, a nonlinear energy storage effect has been discovered which is due to the presence of nonlinearly loaded loop antennas if excited by an HPEM-excitation. In this contribution, this effect is further studied by experiment. It is seen that the nonlinear energy storage effect can be reproduced by means of a rather simple experimental setup. This allows to straighforwardly study parameter variations in order to attain an improved understanding of the considered effect.

Experimental and Comparative Study of Rotor Vibrations of Permanent Magnet Machines with Two Different Fractional Pole/Slot Combinations

This study deals with the noise, vibration, and harshness (NVH) characteristic analysis of permanent magnet synchronous motors (PMSMs) for electrical machines, such as electrically driven tools that are used in industries. An improved NVH design is needed for application to industrial tools. In general, the electromagnetic NVH characteristics of PMSMs are classified into electromagnetic excitation sources, such as total harmonic distortion of EMF, torque pulsation, magnetic pull force, and unbalanced magnetic force (UMF). This study compares the vibration and noise generated by fractional pole/slot combinations. In PMSMs with fractional pole/slot combinations, UMF is an important NVH source. PMSMs generate UMF because of armature reaction fields based on the pole/slot combinations and harmonics of magnetic flux density. UMF was derived using the finite element method, and the rotor vibration analysis was performed using electromagnetic mechanical coupling analysis. The analysis results and the effect of electromagnetic excitation characteristics on the rotor vibration of the PMSMs were compared and analyzed.

Space-time nonseparable pulses: Constructing isodiffracting donut pulses from plane waves and single-cycle pulses

Maxwell's equations can be satisfied not only by plane electromagnetic waves, but also by more exotic space-time nonseparable electromagnetic pulses which cannot be represented as a product of time- and space-dependent functions. A family of such pulses with finite energy was identified by Ziolkowski [Phys. Rev. A 39, 2005 (1989)]. Later, Hellwarth and Nouchi [Phys. Rev. E 54, 889 (1996)] highlighted a subset of Ziolkowski's pulses, now known as flying donuts, a formation of polarization singularities of toroidal topology traveling at the speed of light. Spurred by recent advances in ultrafast and topological optics, space-time nonseparable electromagnetic excitations are now becoming the focus of growing experimental efforts as they hold promise for topological information transfer, probing and inducing transient excitations in matter such as anapole and toroidal modes. Here we demonstrate that the flying donut can be constructed from an ensemble of monochromatic plane waves with continuous spatial and frequency spectrum and hence can be generated by converting broadband conventional transverse electromagnetic pulses.

Design and characterisation of frequency selective conductive materials for electromagnetic fields control

To prevent the electromagnetic (EM) wakefields excitation, protect detectors from damage at a range of installations and facilities including particle accelerators the EM field control is required. Conductive foils or wires providing EM protection and required thermal and mechanical properties are normally used. We suggest novel composite materials with uniquely designed frequency selective conductivity enabling them to overcome the properties of the conventional materials, protect from EM fields and supress undesirable phenomena. Theoretical and experimental investigations are carried out and the conductivity of designed and composite (dual-layer) aluminium/graphene metamaterials as well as graphene and aluminium foils is studied. The EM properties of these materials are compared, and conditions of full and partial electromagnetic transparency are discussed. Results observed allow engineering materials capable of EM field control, instability suppression including those observed in high-intensity particle accelerators and enabling control of an EM field generating media including relativistic charge particle beams.

Mathematical model of the technological vibratory unit with electromagnetic excitation

The mathematical model of the technological vibratory unit with electromagnetic excitation is considered to its features that are important for the dynamic design problems. The model is based on the differential equations of electrical balance and mechanical balance, taking into account the mobility degree of inertial masses with spring linkages. The vibratory unit vibration properties are analyzed concerning the power voltage and frequency coupling, interacting inertia masses mobility degree, spring linkages properties, magnetic core steel magnetizing characteristic non-linearity, leakage fluxes, electric, magnetic and mechanical energy losses. The research performed for dynamical design problem solution is distinguished by a novel approach to the estimation of the capability of changing vibration properties of the movable operating element of the technological vibratory unit with an additional mass attached to it. The model design technology based on the structural modelling method supported by Matlab Simulink is proposed. The research results can be useful for specialists in vibration engineering, machines and devices durability dynamics and vibroprotection.

Experimental and Numerical Analyses for Auto-Parametric Internal Resonance of a Framed Structure

The auto-parametric internal resonance experiment of a [Formula: see text]-shaped frame is first conducted in this research. A non-contact electromagnetic vibration exciter is used to exert a periodic force on the vertical beam of the frame. The phenomena of internal resonance and non-internal resonance are observed and measured in this test. A common resonance of the vertical beam is excited by the external electromagnetic force, and the auto-parametric internal resonance of the horizontal beam is subsequently induced by the common resonance. The numerical method is also used to simulate the internal resonance and non-internal resonance. The stability boundaries of internal resonance and non-internal resonance are numerically and experimentally determined and compared. The numerical stability boundaries are in agreement with the experimental results. The results indicate that a small external excitation can excite a strong internal resonance response of a framed structure. The unstable domain of the internal resonance is much bigger than that of the non-internal resonance. The auto-parametric internal resonance is much more dangerous than the non-internal resonance. The risk of auto-parametric internal resonance should be emphasized and avoided in the designs of engineering structures.

Analytical study of air-gap surface force – application to electrical machines

AbstractThe Maxwell stress tensor (MST) method is commonly used to accurately compute the global efforts, such as electromagnetic torque ripple and unbalanced electromagnetic forces in electrical machines. The MST has been extended to the estimation of local magnetic surface force for the vibroacoustic design of electrical machines under electromagnetic excitation. In particular, one common air-gap surface force (AGSF) method based on MST is to compute magnetic surface forces on a cylindrical shell in the air gap. However, the AGSF distribution depends on the radius of the cylindrical shell. The main contribution of this study is to demonstrate an analytic transfer law of the AGSF between the air gap and the stator bore radius. It allows us to quantify the error between the magnetic surface force calculated in the middle of the air gap and the magnetic force computed on the stator teeth. This study shows the strong influence of the transfer law on the computed tangential surface force distribution through numerical applications with induction and synchronous electrical machines. Finally, the surface force density at stator bore radius is more accurately estimated when applying the new transfer law on the AGSF.

Robust Development of Electric Powertrain NVH for Compact Electric SUV

<div class="section abstract"><div class="htmlview paragraph">Electric vehicles (EV’s) present new challenges to achieving the required noise, vibration & harshness performance (NVH) compared with conventional vehicles. Specifically, high-frequency noise and unexpected noise phenomenon, previously masked by the internal combustion engine can cause annoyance in an EV. Electric motor (E-motor) whine noise caused by electromagnetic excitation during E-motor operation is caused by torque ripple and radial excitation. Under high speed and high load operating conditions, the overall sound level may be low, however high frequency whine noise can impair the vehicle level NVH performance. An example of a previously masked unexpected noise phenomenon is a droning noise that can be caused by manufacturing quality variation of the spline coupling between the rotor shaft of the E-motor and the input shaft of the reducer. It is dominated by multiple higher orders of the E-motor rotation frequency.</div><div class="htmlview paragraph">In this study, the high speed and high load condition whine noise problem was reproduced through electromagnetic and structural analysis. The countermeasures (E-motor geometry refinements to reduce the excitations and mechanical system transfer path modifications to reduce the vibration response) were defined and the effects investigated. Mechanical system modification to improve NVH performance without increasing the mass is challenging. However, E-motor air-gap geometry optimization, such as slot opening modulation and rotor notch modifications achieved significant noise reduction without critical trade-off of other performance.</div><div class="htmlview paragraph">This paper also describes the basic improvement plan proposed through the simulation of the droning noise behavior. The main two manufacturing errors (pitch error in the spline coupling and the alignment error between the rotor and the gearbox shafts) that are responsible for the unexpected droning noise were identified. Using simulation it was shown that the droning noise can be reduced through improved quality control and tolerance design optimization of factors such as axis self-alignment and spline gear tooth quality.</div></div>

Radiative Toroidal Dipole and Anapole Excitations in Collectively Responding Arrays of Atoms

A toroidal dipole represents an often overlooked electromagnetic excitation distinct from the standard electric and magnetic multipole expansion. We show how a simple arrangement of strongly radiatively coupled atoms can be used to synthesize a toroidal dipole where the toroidal topology is generated by radiative transitions forming an effective poloidal electric current wound around a torus. We extend the protocol for methods to prepare a delocalized collective excitation mode consisting of a synthetic lattice of such toroidal dipoles and a nonradiating, yet oscillating charge-current configuration, dynamic anapole, for which the far-field radiation of a toroidal dipole is identically canceled by an electric dipole.

In Situ Experiment and Analysis of the Attenuation Characteristics of Environmental Vibrations Based on Frequency Sweep Method

Analysis of the attenuation characteristics of environmental vibrations with different frequencies is of great benefit for preventing many vibration-related problems. This study carried out an in situ experimental study on the attenuation characteristics of a series of single frequency ground vibrations caused by harmonic excitations. An electromagnetic vibration excitation system was adopted to generate harmonic excitations at frequencies varying from 10 Hz to 80 Hz with steps 5 Hz. 5 low frequency, 1 component, 991B vibration sensors fastened on the ground surface were used for the measurement of the vertical velocity time histories of ground vibrations at 5 test points with different distances from the vibration source. The vibration level in terms of the vertical peak particle velocity of single frequency ground vibrations in general decayed monotonically but nonlinearly with distance, however, the attenuations of 15 Hz, 45 Hz, 65 Hz and 75 Hz ground vibrations were oscillatory due to vibration interference on the ground surface. The attenuation of single frequency ground vibrations was more rapid in the zone close to the vibration source than that in the zone far away. This study demonstrates that comparison of the attenuation characteristics of high and low frequency ground vibrations should take into account the difference in the amplitudes of the corresponding ground vibrations.

Torque distribution method based on vibration instability of PS-HEV transmission system

The power-split hybrid electric vehicle has multiple working modes, which can be switched to different working mode according to different working conditions. The main switching process involved in the vehicle driving is the switch from the pure electric mode to the hybrid driving mode. This paper studies the mode switching process involved in the power-split hybrid electric vehicle driving process, and a nonlinear dynamic equation of the electromechanical coupling of the corresponding transmission system is established. Then the multi-scale method is employed to solve the dynamic equation, and the amplitude-frequency response curve is drawn. According to the curve, the effects of load, mechanical input excitation of the engine and motor electromagnetic excitation on the electromechanical coupling torsional vibration of the transmission system are studied. The engine and motor torque distribution schemes are obtained by analyzing the amplitude-frequency response curve of the torsional vibration characteristics of the system. The analysis results show that the vibration instability phenomenon of the transmission system can be avoided by establishing the nonlinear dynamic equation of the transmission system, analyzing the vibration characteristics of the vibration system, and optimizing the torque distribution of a PS-HEV at different working modes.

INVESTIGATION OF AN ELECTROMAGNETIC TWO-STROKE VIBRATING ACTIVATOR IN OSCILLATORY MODE

The article considers the results of the study of electromagnetic vibration exciter with sequentially included capacitor in the electrical circuit, consisting of mechanical and electrical subsystems. It is shown that by means of the Lagrangian-Maxwell equation the interconnection between mechanical and electric subsystems can be realized. The relations describing processes of establishment of amplitudes and phases of oscillations both in mechanical and in electric subsystems are deduced. The equations connecting the output (amplitude) of vibration of the vibrating exciter with its input (voltage) of the network are presented. As a result, the formulas allowing making corrections at the solution of the system describing operation of the electromagnetic vibrating exciter in two-stroke mode are presented.

Vibration Reduction by Magnetic Slot Wedge for Rotating Armature Permanent Magnet Motors

There is only slot frequency electromagnetic vibration and no pole frequency vibration in rotating armature permanent magnet motor (RAPMM), which is the advantage of this motor. The open of slot makes the air-gap magnetic field distorted and causes the harmonic of electromagnetic excitation force. In order to reduce the slot frequency vibration of the RAPMM, the method of placing magnetic slot wedge (MSW) at the slot opening is put forward accordingly. Through the finite-element simulation, it is finally shown that the MSW is capable of weakening the harmonic of the air-gap flux density, as well as decreasing the high-frequency component of the electromagnetic excitation force. Therefore, it is acknowledged that MSW can suppress the cogging torque and the vibration of corresponding frequency on the stator significantly. Finally, it is confirmed by the experiments that the built-in MSW is an effective measure for reducing the vibration of the RAPMM.

Precision measurement of the E2 transition strength to the 21+ state of C12

The form factor of the electromagnetic excitation of $^{12}$C to its 2$^+_1$ state was measured at extremely low momentum transfers in an electron scattering experiment at the S-DALINAC. A combined analysis with the world form factor data results in a reduced transition strength $B(E2; 2^+_1\rightarrow 0^+_1) =7.63(19)$ e$^2$fm$^4$ with an accuracy improved to 2.5\%. In-Medium-No Core Shell Model results with interactions derived from chiral effective field theory are capable to reproduce the result. A quadrupole moment $Q(2^+_1) = 5.97(30)$ efm$^2$ can be extracted from the strict correlation with the $B((E2)$ strength emerging in the calculations.

Comparative Study of Light Guiding by Freestanding Linear Chains of Spherical Au and Si Nanoparticles

Electromagnetic energy guiding by free‐standing straight finite chains of Au and Si spherical nanoparticles is comparatively studied on the basis of a system of integral equations for self‐consistent currents excited inside particles. Self‐consistent currents are given in terms of an electric field T‐scattering tensor (dyadic) operator of a single particle of any shape. Simplifying the T‐scattering operator, the equations system is resolved analytically in the nearest‐neighbor coupling approximation. Interactions beyond the nearest neighbors are accounted for by the perturbative theory. It is shown that electromagnetic excitation propagates along a chain of coupled particles without radiation losses in the form of a dark mode. The resonant conditions for the coupling parameter yield the frequency of the dark mode and the corresponding radius of the particles. As a result, unlike Au chains, no long‐range electromagnetic energy transfer was revealed along the Si chains. Physically, in both cases of Au and Si spheres, the resonant frequencies fall within the bands of the corresponding electric dipole Mie resonances. However, the positive value of the real part of the Si refraction index at the resonant frequency causes exponential excitation currents decreasing with the particle number.

Analytical Correlation Between Time and Frequency Domain Shielding Effectiveness of Metallic Enclosures With Apertures

Time domain shielding effectiveness (SE) of metallic enclosures with apertures against electromagnetic pulse excitation has been analytically estimated and correlated to the frequency domain characteristics. The method is based on the analysis of the transient process at the aperture and an equivalent magnetic current source, to derive the initial peak amplitude appearing at the very beginning of the coupled field waveforms. The equivalent circuit model is utilized to analytically describe the frequency domain SE data. Then, a simple correlation formula has been derived, which relates the peak value reduction of the E-field and H-field to the specified spectral data minus a specially defined factor. Especially, the correlation for the E-field is shown to link the spectral SE data near the fundamental resonant frequency of TE101 mode with the peak amplitudes in time domain. A series of numerical and experimental cases have been checked to confirm the applicability of the analytical formulas. Comparisons between the data and the analysis exhibit reasonable agreements.

Collective excitations and universal broadening of cyclotron absorption in Dirac semimetals in a quantizing magnetic field

The spectrum of electromagnetic collective excitations in Dirac semimetals placed in a quantizing magnetic field is considered. We have found the Landau damping regions using the energy and momentum conservation law for allowed transitions between one-particle states of electron excitations. Analysis of dispersion equations for longitudinal and transverse waves near the window boundaries in the Landau damping regions reveals different types of collective excitations. We also indicate the features of universal broadening of cyclotron absorption for a magnetic field variation in systems with linear dispersion of the electron spectrum. The use of the obtained spectrum also allows us to predict a number of oscillation and resonance effects in the field of magneto-optical phenomena.

Global apparent resistivity definition for a high-performance TEM excitation source

AbstractThe high-performance transient electromagnetic method (TEM) excitation source is a new type of source that has been proposed for urban underground space exploration. This source is composed of two trapezoid plates. To ensure that the radiation field was focused in a certain direction, the two trapezoid plate-shaped antennas were arranged into a horn shape. This new source is characterised by high power, directional excitation and high resolution. The corresponding multi-component global apparent resistivity definition method is established for a high-performance transient electromagnetic excitation source. This method is studied using the inverse function theorem. Then, the monotonic relationship between components of the electromagnetic field and resistivity is analysed. For the fields that satisfy the monotonic relationship with half-space resistivity, the apparent resistivity can be calculated correctly to ignore the time period and location in the space. This means that this definition method can eliminate the limitation of early and late times, and the near and far zones. The apparent resistivity calculation results of the theoretical layered model reveal that global apparent resistivity curves show a regular change, which smoothly and comprehensively reflects the change of electrical information in the model. The experimental results of the 3D model show that the five-layer low-resistivity anomaly contained in the urban underground space designed in this paper exhibits an obvious response in the global apparent resistivity profile. It is concluded that a high-performance TEM excitation source possesses a high resolution, clearly reflecting all of the anomalies of a complex urban underground space model.