scholarly journals Research on Permanent Magnet-Type Super-Low-Frequency Mechanical Antenna Communication

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Xiaoyu Wang ◽  
Wenhou Zhang ◽  
Xin Zhou ◽  
Zhenxin Cao ◽  
Xin Quan
Keyword(s):  
Permanent Magnet ◽  
Permanent Magnets ◽  
Radiation Power ◽  
Near Field ◽  
Low Frequency ◽  
Induced Voltage ◽  
Analysis Model ◽  
Large Area ◽  
Communication Structure ◽  
Radiated Power

In the super-low-frequency ( 30 ∼ 300  Hz ) band communication, the traditional antenna covers a large area and has low radiation efficiency. The excitation of electromagnetic waves by the mechanical motion of permanent magnets enables miniaturized technology for super-low-frequency communication. For this miniaturization technique, this paper proposes a super-low-frequency communication architecture framework. Theoretical analysis and experimental verification of each unit module in the structural framework are carried out to achieve high-quality communication. For the radiation unit, permanent magnet parameters and communication distances are introduced to establish a rotating permanent magnet radiation power analysis model and to study the radiation characteristics of rotating permanent magnets. For the receiver unit, a sensitivity normalization characterization method based on the ratio of the coil thermal noise voltage to the induced voltage is proposed. Based on the sensitivity analysis model, a square coil was developed that meets the communication requirements of a mechanical antenna and an experimental platform was built. Experiments are conducted on the factors affecting radiated power and coil sensitivity, and 2FSK signal modulation communication experiments are conducted to verify the feasibility of the communication structure framework. The volume of the mechanical antenna permanent magnets in the experiment is all below 10 cm3, and the operating frequency is continuously adjustable from 0 to 250 Hz. The experimental results show that the near-field radiated power of a rotating permanent magnet is proportional to square of the volume of the rotating permanent magnet; the sensitivity of the coil is proportional to the number of turns and the area of the coil. By controlling the speed in real time, you can control the frequency of the signal and modulate it.

Pre-Strained Piezoelectric PVDF Nanofiber Array Fabricated by Near-Field Electrospining on Cylindrical Process for Flexible Energy Conversion

2012 ◽  
Vol 566 ◽  
pp. 462-465 ◽  
Author(s):  
Zong Hsin Liu ◽  
Li Wei Lin ◽  
Cheng Teng Pan ◽  
Zong Yu Ou
Keyword(s):  
Electric Field ◽  
Energy Conversion ◽  
Polyvinylidene Fluoride ◽  
Near Field ◽  
Low Frequency ◽  
Glass Tube ◽  
Copper Electrode ◽  
Ambient Vibration ◽  
Induced Voltage ◽  
Β Phase

In this study, near-field electrospining on hollow cylindrical (NFES) process was used to fabricate permanent piezoelectricity of polyvinylidene fluoride (PVDF) piezoelectric nanofibers. With in situ electric poling, mechanical stretching and heating during NFES process, the pre-strained piezoelectric PVDF nanofibers with high stretchability and energy conversion efficiency can be applied at low-frequency ambient vibration to convert mechanical energies into electrical signals. By adjusting rotating velocity of the hollow cylindrical glass tube on X-Y stage, electric field, baking temperature and carbon nanotube (CNT) concentration in PVDF solution, the crystalline of β phase, polarization intensity and morphology of piezoelectric fiber can be controlled. XRD (X-ray diffraction) observation of PVDF fibers was characterized. With electric field 0.5×107 V/m (needle-to-tube distance 2 mm and DC voltage 5 kV), rotating velocity 400 r.p.m, baking temperature 80 °C and 0.03 wt% CNT in NFES process, it reveals a high diffraction peak at 2θ=20.8° of piezoelectric crystal β-phase structure. Then the array nanofibers were transferred onto a parallel copper electrode by using flexible insulation epoxy/PI film to provide packaging protection. When the sensor was tested under 5 Hz vibration frequency, the maximum induced voltage was 29.4 mVp-p.

A Low Frequency Permanent Magnet Passive Vibration Isolator

2012 ◽  
Vol 586 ◽  
pp. 328-336
Author(s):  
Qiang Li ◽  
Deng Feng Xu ◽  
Jin Chun Hu ◽  
Liu Hao
Keyword(s):  
Permanent Magnet ◽  
Permanent Magnets ◽  
Load Capacity ◽  
Semiconductor Industry ◽  
Low Frequency ◽  
Magnetic Suspension ◽  
Experimental Results ◽  
Vibration Isolator ◽  
Rubber Membrane ◽  
Guide Device

Magnetic suspension vibration isolators have attracted significant attention in the field of semiconductor industry and high precision equipments. However, it is impossible to levitate an object by only permanent magnet due to instability of permanent magnets. It needs a guide device or active control to hold the magnetic suspension passive vibration isolator (MSPVI) at equilibrium position. In order to overcome the instability of the permanent magnets, the linear bearing, rubber O-ring and rubber membrane are applied in the MSPVI. The transmissibility of the MSPVI was calculated and subsequently measured. The experimental results show that the MSPVI can achieve low natural frequency with the help of the rubber membrane which is superior to the linear bearing and o-ring. Beside, the vibration isolating performance of the MSPVI is measured. The experimental results reveal that the MSPVI achieves the lowest resonant frequency when the load capacity of the MSPVI reaches maximum value.

An electromagnetic energy harvester using ferrofluid as a lubricant

2018 ◽  
Vol 32 (34n36) ◽  
pp. 1840084
Author(s):  
Siqi Wang ◽  
Yongkai Liu ◽  
Decai Li ◽  
Hujun Wang
Keyword(s):  
Permanent Magnet ◽  
Human Body ◽  
Permanent Magnets ◽  
Average Power ◽  
Low Frequency ◽  
Human Motion ◽  
Body Motion ◽  
Plastic Tube ◽  
Magnetic Spring ◽  
Electromagnetic Generator

An electromagnetic generator with magnetic spring and ferrofluid is proposed and designed to harvest low-frequency vibration energy from human body motion. The magnetic spring is formed by gravity and magnetic repulsive force between the fixed and the moving permanent magnets. The ferrofluid is aggregated at both ends of the moving permanent magnet, and the ferrofluid layer between the plastic tube wall and permanent magnet can remove the solid-friction as a fluid lubricant. The electromagnetic generator is used to harvest human motion energy. The measured average load powers of electromagnetic generator with ferrofluid 1.5 g from human body motion are 1.3 mW and 7.5 mW during walking and low running, respectively, which is 30 times more than the measured average power of generator without ferrofluid.

scholarly journals A Positioning System Based on Low-Frequency Magnetic Fields

2021 ◽  
Author(s):  
Paolo Carbone ◽  
Valter Pasku ◽  
Alessio De Angelis ◽  
Marco Dionigi ◽  
Guido De Angelis ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Low Frequency ◽  
Outdoor Environment ◽  
Positioning System ◽  
Induced Voltage ◽  
Quality Factors ◽  
Large Area ◽  
Key Factor ◽  
Loop Antennas ◽  
Transmitting Antenna

This paper describes the design and the realization of a low-frequency ac magnetic-field-based indoor positioning system (PS). The system operation is based on the principle of inductive coupling between wire loop antennas. Specifically, due to the characteristics of the ac artificially generated magnetic fields, the relation between the induced voltage and the distance is modeled with a linear behavior in a bilogarithmic scale when a configuration with coplanar, thus equally oriented, antennas is used. In this case, the distance between a transmitting antenna and a receiving one is estimated using measurements of the induced voltage in the latter. For a high operational range, the system makes use of resonant antennas tuned at the same nominal resonant frequency. The quality factors act as antenna gain increasing the amplitude of the induced voltage. The low-operating frequency is the key factor for improving robustness against nonline-of-sight (NLOS) conditions and environment influences with respect to other existing solutions. The realized prototype, which is implemented using off-the-shelf components, exhibits an average and maximum positioning error, respectively, lower than 0.3 and 0.9 m in an indoor environment over a large area of 15 m × 12 m in NLOS conditions. Similar performance is obtained in an outdoor environment over an area of 30 m × 14 m. Furthermore, the system does not require any type of synchronization between the nodes and can accommodate an arbitrary number of users without additional infrastructure.

scholarly journals A physical model for low-frequency electromagnetic induction in the near field based on direct interaction between transmitter and receiver electrons

2016 ◽  
Vol 472 (2191) ◽  
pp. 20160338 ◽  
Author(s):  
Ray T. Smith ◽  
Fred P. M. Jjunju ◽  
Iain S. Young ◽  
Stephen Taylor ◽  
Simon Maher
Keyword(s):  
Physical Model ◽  
Electromagnetic Induction ◽  
Near Field ◽  
Low Frequency ◽  
Direct Interaction ◽  
Induced Voltage ◽  
Principle Of Superposition ◽  
Sensor Applications ◽  
Direct Explanation ◽  
Uniform Current

A physical model of electromagnetic induction is developed which relates directly the forces between electrons in the transmitter and receiver windings of concentric coaxial finite coils in the near-field region. By applying the principle of superposition, the contributions from accelerating electrons in successive current loops are summed, allowing the peak-induced voltage in the receiver to be accurately predicted. Results show good agreement between theory and experiment for various receivers of different radii up to five times that of the transmitter. The limitations of the linear theory of electromagnetic induction are discussed in terms of the non-uniform current distribution caused by the skin effect. In particular, the explanation in terms of electromagnetic energy and Poynting’s theorem is contrasted with a more direct explanation based on variable filament induction across the conductor cross section. As the direct physical model developed herein deals only with forces between discrete current elements, it can be readily adapted to suit different coil geometries and is widely applicable in various fields of research such as near-field communications, antenna design, wireless power transfer, sensor applications and beyond.

scholarly journals A Positioning System Based on Low-Frequency Magnetic Fields

2021 ◽  
Author(s):  
Paolo Carbone ◽  
Valter Pasku ◽  
Alessio De Angelis ◽  
Marco Dionigi ◽  
Guido De Angelis ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Low Frequency ◽  
Outdoor Environment ◽  
Positioning System ◽  
Induced Voltage ◽  
Quality Factors ◽  
Large Area ◽  
Key Factor ◽  
Loop Antennas ◽  
Transmitting Antenna

This paper describes the design and the realization of a low-frequency ac magnetic-field-based indoor positioning system (PS). The system operation is based on the principle of inductive coupling between wire loop antennas. Specifically, due to the characteristics of the ac artificially generated magnetic fields, the relation between the induced voltage and the distance is modeled with a linear behavior in a bilogarithmic scale when a configuration with coplanar, thus equally oriented, antennas is used. In this case, the distance between a transmitting antenna and a receiving one is estimated using measurements of the induced voltage in the latter. For a high operational range, the system makes use of resonant antennas tuned at the same nominal resonant frequency. The quality factors act as antenna gain increasing the amplitude of the induced voltage. The low-operating frequency is the key factor for improving robustness against nonline-of-sight (NLOS) conditions and environment influences with respect to other existing solutions. The realized prototype, which is implemented using off-the-shelf components, exhibits an average and maximum positioning error, respectively, lower than 0.3 and 0.9 m in an indoor environment over a large area of 15 m × 12 m in NLOS conditions. Similar performance is obtained in an outdoor environment over an area of 30 m × 14 m. Furthermore, the system does not require any type of synchronization between the nodes and can accommodate an arbitrary number of users without additional infrastructure.

scholarly journals Failure Diagnosis for Demagnetization in Interior Permanent Magnet Synchronous Motors

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Takeo Ishikawa ◽  
Naoto Igarashi ◽  
Nobuyuki Kurita
Keyword(s):  
Vector Control ◽  
Permanent Magnet ◽  
Permanent Magnets ◽  
Low Frequency ◽  
Axial Direction ◽  
Permanent Magnet Synchronous Motors ◽  
Element Analysis ◽  
Synchronous Motors ◽  
Interior Permanent Magnet ◽  
Axis Position

Since a high degree of reliability is necessary for permanent magnet synchronous motors, the detection of a precursor for the demagnetization of permanent magnets is very important. This paper investigates the diagnosis of very slight PM demagnetization. The permanent magnet volume is altered so as to mimic the effect of demagnetization. This paper investigates the influence of demagnetization by using several methods: the 3D finite element analysis (FEA) of the motor, the measurement of high-frequency impedance, and the measurement and FEA of the stator voltage and current under vector control. We have obtained the following results. The back-EMF is proportional to permanent magnet volume, and there is no difference in the demagnetization in the radial direction and in the axial direction. Even harmonics and subharmonics of flux density at the teeth tip could be useful for diagnosis if a search coil is installed there. The relatively low frequency resistance at the d-axis position is useful for diagnosis. Under vector control, the stator voltage is useful except in an intermediate torque range, and the intermediate torque is expressed by a simple equation.

Study and design of dual stator permanent magnet machine with spoke-type configurations using phase-group concentrated-coil windings

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1381-1389
Author(s):  
Dezhi Chen ◽  
Chengwu Diao ◽  
Zhiyu Feng ◽  
Shichong Zhang ◽  
Wenliang Zhao
Keyword(s):  
Permanent Magnet ◽  
Permanent Magnets ◽  
Low Cost ◽  
Dynamic Performance ◽  
Torque Ripple ◽  
Permanent Magnet Machine ◽  
Torque Density ◽  
Phase Group ◽  
High Torque ◽  
Simulation Results

In this paper, a novel dual-stator permanent magnet machine (DsPmSynM) with low cost and high torque density is designed. The winding part of the DsPmSynM adopts phase-group concentrated-coil windings, and the permanent magnets are arranged by spoke-type. Firstly, the winding structure reduces the amount of copper at the end of the winding. Secondly, the electromagnetic torque ripple of DsPmSynM is suppressed by reducing the cogging torque. Furthermore, the dynamic performance of DsPmSynM is studied. Finally, the experimental results are compared with the simulation results.

scholarly journals Occluded Grape Cluster Detection and Vine Canopy Visualisation Using an Ultrasonic Phased Array

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2182
Author(s):  
Baden Parr ◽  
Mathew Legg ◽  
Stuart Bradley ◽  
Fakhrul Alam
Keyword(s):  
Near Field ◽  
Low Frequency ◽  
Volume Estimation ◽  
Yield Estimation ◽  
3D Scan ◽  
Management Processes ◽  
Canopy Volume ◽  
Ultrasonic Phased Array ◽  
Added Benefit ◽  
Grape Yield

Grape yield estimation has traditionally been performed using manual techniques. However, these tend to be labour intensive and can be inaccurate. Computer vision techniques have therefore been developed for automated grape yield estimation. However, errors occur when grapes are occluded by leaves, other bunches, etc. Synthetic aperture radar has been investigated to allow imaging through leaves to detect occluded grapes. However, such equipment can be expensive. This paper investigates the potential for using ultrasound to image through leaves and identify occluded grapes. A highly directional low frequency ultrasonic array composed of ultrasonic air-coupled transducers and microphones is used to image grapes through leaves. A fan is used to help differentiate between ultrasonic reflections from grapes and leaves. Improved resolution and detail are achieved with chirp excitation waveforms and near-field focusing of the array. The overestimation in grape volume estimation using ultrasound reduced from 222% to 112% compared to the 3D scan obtained using photogrammetry or from 56% to 2.5% compared to a convex hull of this 3D scan. This also has the added benefit of producing more accurate canopy volume estimations which are important for common precision viticulture management processes such as variable rate applications.

scholarly journals Research on the Non-Magnetic Conductor of a PMSM Based on the Principle of Variable Exciting Magnetic Reluctance

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 318
Author(s):  
Chunyan Li ◽  
Fei Guo ◽  
Baoquan Kou ◽  
Tao Meng
Keyword(s):  
Permanent Magnet ◽  
Electromagnetic Force ◽  
Electromotive Force ◽  
Permanent Magnets ◽  
Permanent Magnet Synchronous Motor ◽  
Synchronous Motor ◽  
Magnetic Conductor ◽  
Critical Speeds ◽  
Motor Structure ◽  
Test Result

A permanent magnet synchronous motor (PMSM) based on the principle of variable exciting magnetic reluctance (VMRPMSM) is presented. The motor is equipped with symmetrical non-magnetic conductors on both sides of the tangential magnetized permanent magnets (PMs). By placing the non-magnetic conductor (NMC), the magnetic reluctance in the exciting circuit is adjusted, and the flux weakening (FW) of the motor is realized. Hence, the NMC is studied comprehensively. On the basis of introducing the motor structure, the FW principle of this PMSM is described. The shape of the NMC is determined by analyzing and calculating the electromagnetic force (EF) acting on the PMs. We calculate the magnetic reluctance of the NMC and research on the effects of the NMC on electromagnetic force, d-axis and q-axis inductance and FW performance. The critical speeds from the test of the no-load back electromotive force (EMF) verify the correctness of the NMC design. The analysis is corresponding to the test result which lays the foundation of design for this kind of new PMSM.

Sign in / Sign up

Export Citation Format

Share Document