Estimation of the Dynamic Parameters of the Bearings in a Flexible Rotor System Utilizing Electromagnetic Excitation by a Built-In Motor

Estimation of the dynamic parameters of bearings is essential in order to be able to interpret the performance of rotating machinery. In this paper, we propose a method to estimate the dynamic parameters of the bearings in a flexible rotor system. By utilizing the electromagnetic excitation generated by a built-in PM motor and finite element (FE) modeling of the rotor, safe, low-cost, and real-time monitoring of the bearing dynamics can be achieved. The radial excitation force is generated by injecting an alternating d-axis current into the motor windings. The FE model of the rotor and the measured frequency responses at the motor and bearing locations are used to estimate the dynamic parameters of the bearings. To evaluate the feasibility of the proposed method, numerical simulation and experiments were carried out on a flexible rotor system combined with a bearingless motor (BELM) having both motor windings and suspension windings. The numerical simulation results show that the proposed algorithm can accurately estimate the dynamic parameters of the bearings. In the experiment, the estimates made when utilizing the excitation force generated by the motor windings are compared with the estimates made when utilizing the excitation force generated by the suspension windings. The results show that most of the stiffness and damping coefficients for the two experiments are in good agreement, within a maximum error of 8.92%. The errors for some coefficients are large because the base values of these coefficients are small in our test rig, so these coefficients are sensitive to deviations. The natural frequencies calculated from the dynamic parameters estimated from the two experiments are also in good agreement, within a maximum relative error of 3.04%. The proposed method is effective and feasible for turbomachines directly connected to motors, which is highly significant for field tests.

The experimental study of the influence of the string length and the position of the electromagnetic excitation coil on the metrological characteristics of the strain sensors of the intelligent monitoring system

The article is devoted to the study of the influence of changes in the string length of string converters and the position of the electromagnetic excitation coil relative to the points of attachment of the string on the amplitude of its vibrations. The re-search was carried out on a prototype of a string converter made under the patent for the invention of the Russian Federation No. 2685803 and having a constant string tension force. The results of theoretical and experimental studies showing the influence of the highest harmonics on the amplitude of string vibrations are presented. The factors determining the composition of harmonics are considered. The contribution of the harmonics to the resulting string oscillation amplitude and the measurement error of the controlled parameter of the stress-strain state is considered. The ranges of the measurements with the help of string converters with a constant string tension force and the ways of their expansion are justified.

The study on the inverse problem of applied current thermoacoustic imaging based on generative adversarial network

Applied Current Thermoacoustic Imaging (ACTAI) is a new imaging method which combines electromagnetic excitation with ultrasound imaging, and takes ultrasonic signal as medium and biological tissue conductivity as detection target. Taking the high contrast advantage of Electrical Impedance Tomography (EIT) and high resolution advantage of ultrasound imaging, ACTAI has broad application prospects in the field of biomedical imaging. Although ACTAI has high excitation efficiency and strong detectable Signal-to-Noise Ratio, yet while under low frequency electromagnetic excitation, it is still a big challenge to reconstruct a high-resolution image of target conductivity. This paper proposes a new method for reconstructing conductivity based on Generative Adversarial Network, and it consists of three main steps: firstly, use Wiener filtering deconvolution to restore the electrical signal output by the ultrasonic probe to a real acoustic signal. Then obtain the initial acoustic source image with filtered backprojection technology. Finally, match the conductivity image with the initial sound source image, which are used as training samples for generating the adversarial network to establish a deep learning model for conductivity reconstruction. After theoretical analysis and simulation research, it is found that by introducing machine learning, the new method can dig out the inverse problem solving model contained in the data, which further reconstruct a high-resolution conductivity image and has strong anti-interference characteristics. The new method provides a new way to solve the problem of conductivity reconstruction in Applied Current Thermoacoustic Imaging.

Specifics of turbo-alternator design with a high rotational speed of 6000 rpm

Object and purpose of research. The object under study is a 36 МW turbo-alternator (TA) with electromagnetic excitation and a high rotational speed of 6000 rpm, which can be used as an option for ac electric power source of 100 Hz in ship electric power systems with a turbo-alternator plant. The purpose is to perform electromagnetic calculations to determine TA main data and technical characteristics, including the stator and rotor pack, their design, mass of active materials, etc. for comparison with a TA of the same power but 3000 rpm. Materials and methods. The studies are based on research and engineering data about investigations and design of double-pole industrial TA of 50 Hz as well as TA with a high current frequency (100 Hz and higher). For this purpose, the known formulas were used to estimate the size of TA active elements, excitation forces of stator and rotor windings, as well as methods for calculation of main TA parameters and technical characteristics. Main results. Design specifics of TA with a high rotational speed of 6000 rpm is identified, and results of electromagnetic estimations are obtained for a specific 36 MW turbo-alternator of 100 Hz with a forced close cycle cooling and better mass and size characteristics. Conclusions. The obtained results are of practical value, showing feasibility of developing a version of 36.0 МW TA with a rotational speed of 6000 rpm and significantly reduced specific mass and size characteristics – tentatively by 35–40 % as compared to the existing TA of the same power but with a speed of 3000 rpm.

Acoustic Simulation of the Electric Vehicle Motor

People pay more and more attention to NVH (N-noise, V-vibration, and H-harshness) characteristics of electric vehicles and motors. The vibration and noise of the electric vehicle motor is a complex multi physical field problem, related to electromagnetic, mechanical, structural and sound fields. In this paper, firstly, the Maxwell electromagnetic field analysis software is used to build the electromagnetic simulation model of PMSM(Permanent magnet synchronous motor) motor, and then the electromagnetic excitation is calculated. Then, the magnetic solid coupling analysis is carried out by using the Maxwell module and harmonic response module of ANSYS Workbench, and the harmonic response of the motor structure under the action of electromagnetic excitation is simulated. After the simulation of magnetic solid coupling is completed, the BEM(Boundary element method) simulation of the permanent magnet synchronous motor is carried out with the acoustic simulation software LMS Virtual Lab. The acoustic simulation of the permanent magnet synchronous motor shows that the sound pressure level at three measurement points have obvious peak value at 3700Hz, 4500Hz, 5400Hz and 6400Hz respectively. The acoustic simulation results lay the foundation for the vibration and noise reduction of the motor.

Polaritonic crystal formed of a tunnel-coupled microcavity array and an ensemble of quantum dots

Propagation of polariton excitations in a defect-containing one-dimensional lattice of microcavities with embedded ultracold atomic nanoclusters (quantum dots) is being considered. The virtual crystal approximation is used to study the properties of electromagnetic excitation spectrum resulting from random variations of the atomic subsystem composition and positions of micropores, as well as from a homogeneous elastic deformation of the considered one-dimensional structure. The group velocity dependence of polariton excitations on structural defect concentration and on deformation parameter is being numerically modeled.

Electromagnetic Analysis and Experimental Study to Optimize Force Characteristics of Permanent Magnet Synchronous Generator for Wave Energy Converter Using Subdomain Method

This paper presents an electromagnetic analysis and experimental verification to optimize the noise, vibration, and harshness (NVH) characteristics of a permanent magnet synchronous generator (PMSG) for wave energy converters (WECs). WECs applicable to breakwater installed in island areas require a wider operating range and a robust design for maintenance compared with wind-turbine systems. Owing to the use of a permanent magnet with a high energy density, the PMSG has a higher power density than other types of generators; however, strong electromagnetic excitation forces that affect the NVH characteristics are generated. Therefore, in this study, the electromagnetic forces are analyzed through an electromagnetic-field analysis using a subdomain analytical method. Based on the analytical solution, electromagnetic forces were determined. Four electromagnetic excitation forces were classified, and the methods for reducing electromagnetic excitation forces are presented here. Finally, a method for evaluating the system resonance through electromechanical analysis is presented. The proposed analysis, optimization, and experimental study are validated through comparison with finite-element analysis and experimental results.

Supertoroidal light pulses as electromagnetic skyrmions propagating in free space

Topological complex transient electromagnetic fields give access to nontrivial light-matter interactions and provide additional degrees of freedom for information transfer. An important example of such electromagnetic excitations are space-time non-separable single-cycle pulses of toroidal topology, the exact solutions of Maxwell’s equations described by Hellwarth and Nouchi in 1996 and recently observed experimentally. Here we introduce an extended family of electromagnetic excitation, the supertoroidal electromagnetic pulses, in which the Hellwarth-Nouchi pulse is just the simplest member. The supertoroidal pulses exhibit skyrmionic structure of the electromagnetic fields, multiple singularities in the Poynting vector maps and fractal-like distributions of energy backflow. They are of interest for transient light-matter interactions, ultrafast optics, spectroscopy, and toroidal electrodynamics.

Design of a direct current motor with a windingless rotor for electric vehicles

Modern electric vehicles typically exploit synchronous motors with magnetoelectric excitation as traction engines. While possessing a series of undeniable advantages, the synchronous motor has one significant drawback ‒ the high cost predetermined by the high price of permanent magnets. In addition, the impossibility to disable a magnetic field in case of engine malfunction can lead to an emergency on the road. Given this, there is a need to design new structures of electrical machines with electromagnetic excitation. The structure of a DC traction motor with electromagnetic excitation involving the rotor or stator segmentation makes it possible to considerably weaken the field of the armature transverse reaction by decreasing magnetic conductivity of the magnetic circuit in the transverse direction. Therefore, such a structure lacks commutating poles and a compensation winding. There are no permanent magnets in the structure, all windings are stationary, an electronic switch is used instead of a collector, and a windingless low-inertia rotor does not require additional measures to remove heat. That all has made it possible to significantly reduce the cost of active materials for the traction engine and improve its reliability. To test the performance of the new design, a full-size model of the engine and a working experimental prototype were fabricated. Applying a synchronous jet engine with magnetization for the BMW i3 electric car as an analog, the engine calculations were performed and its simulation was carried out. The results of the analysis show that the mass of the new engine is 35 % greater than the mass of the analog but the cost of active materials is less than that of the analog by 63 %. The results testify to the possibility of implementing a given structure industrially