Anti-electromagnetic Interference Research Articles

Low frequency vibration monitoring of wind turbine tower based on optical fiber sensor and its potential for internet of things

Among all renewable energy sources, wind energy is a cost-effective alternative energy source. The majority of wind turbines are built in harsh environments due to their power generation characteristics, which is one of the prime reasons resulting in frequent failures of wind turbine. Among various failures, the vibration of wind turbine tower cannot be ignored because it is a precursor of the failure of the wind turbine. The electrical vibration sensors have the problems of power supply and electromagnetic interference for the condition assessment of wind turbine tower. A vibration sensor based on optical Fabry-Perot (F-P) interference principle with high sensitivity is designed, fabricated and characterized to further meet the requirements of vibration detection of wind turbine tower. The mechanical simulation model of the diaphragm and optical vibration platform is constructed to verify the sensing characteristic of the F-P optical fiber vibration sensor (OFVS). The experiment results indicate a resonant frequency of the F-P OFVS of 223 Hz, an output sensitivity of 122.22 mV/m·s−2 at 10 Hz, and a horizontal output of less than 6 %. In addition, the designed F-P OFVS possesses the superiorities of compact structure, passive and excellent anti-electromagnetic interference, and has a wide application prospect in the vibration detection of the wind turbine tower.

Anti-electromagnetic interference encapsulation method for resonance-enhanced magnetoelastic sensors inside prestressed concrete structures

Prestress, which is critical to prestressed concrete (PC) structures, can be monitored using resonance-enhanced magnetoelastic (REME) sensors. REME sensors inside the PC structure are influenced by adjacent sensors and adjacent rebars. However, the sensor’s anti-electromagnetic interference (EMI) encapsulation is lacking. After clarifying the principle of the REME method, a finite element model was established. The influence of the encapsulation’s electrical conductivity and magnetic permeability on the sensor’s electromagnetic compatibility was analyzed. Prestress monitoring experiments were conducted. The results showed that the sensor encapsulated with brass can resist low-frequency EMI and high-frequency EMI. After encapsulating, the sensitivity of the induced voltage-prestress relationship to adjacent sensors was reduced by 52.07%, and that to adjacent rebars was increased by 14.54%. The corresponding prestress monitoring accuracy was increased by 20.86% and 24.49%, respectively. The higher monitoring accuracy verified the feasibility of the proposed encapsulation method, which can resist both low-frequency EMI and high-frequency EMI.

Optical signals measurement of discharge plasma in air switch cabinet using a fluorescent optical fiber as the sensor

Air switch cabinets are widely employed in the power industry, there is, however, no reliable methods for detecting partial discharges (PDs). Because fiber optic-based sensors are easy to install and have anti-electromagnetic interference capabilities, they are well suited for PDs detection in switch cabinets with their many components and metal shell structure. In this work, corona discharge in an air switch cabinet was detected using fluorescent fiber, and the characteristics of PDs were analyzed. Furthermore, experimental investigations were conducted to explore the impact of gas pressure and fiber length on the PDs detection. The results exhibit a correlation between the aforementioned factors and the PDs’ total amplitude, maximum amplitude, number of pulses and detection limit of PD quantity. The results can provide references for the application of fluorescent optical fiber on the PD detection in air switch cabinet.

A Review of Wearable Optical Fiber Sensors for Rehabilitation Monitoring.

As the global aging population increases, the demand for rehabilitation of elderly hand conditions has attracted increased attention in the field of wearable sensors. Owing to their distinctive anti-electromagnetic interference properties, high sensitivity, and excellent biocompatibility, optical fiber sensors exhibit substantial potential for applications in monitoring finger movements, physiological parameters, and tactile responses during rehabilitation. This review provides a brief introduction to the principles and technologies of various fiber sensors, including the Fiber Bragg Grating sensor, self-luminescent stretchable optical fiber sensor, and optic fiber Fabry-Perot sensor. In addition, specific applications are discussed within the rehabilitation field. Furthermore, challenges inherent to current optical fiber sensing technology, such as enhancing the sensitivity and flexibility of the sensors, reducing their cost, and refining system integration, are also addressed. Due to technological developments and greater efforts by researchers, it is likely that wearable optical fiber sensors will become commercially available and extensively utilized for rehabilitation.

Hardware and Software Design of Programmable Medium and High-Speed Data Acquisition (DAQ) Board of Fiber Optic Signal for Partial Discharge Acquisition

The anti-electromagnetic interference capability of partial discharge (PD) acoustic signal conversion and collection circuits severely restrict the sensitivity of PD detection. The data acquisition (DAQ) systems available in the current market are costly and have limited functionality, making it difficult to satisfy the acquisition requirements for PD detection. This paper proposes a medium to high-speed fiber optic signal acquisition board with an adjustably controlled sampling rate and filter cutoff frequency. The circuit achieves a higher signal-to-noise (SNR) ratio by distributing the noise in each part of the signal acquisition chain reasonably. The temperature characteristics of the acquisition module are improved by utilizing the programmable T-type structure for transimpedance amplification of photocurrent. The DAQ card performs data acquisition and processing using STM32H743 internal ADC and caches data in bulk with an SRAM and SD card. A data uploading method based on time reference has been proposed, which enables full, effective information signal upload through a low-cost transmission interface. The research ultimately achieves a stable sampling of three channels at 1 MSps, SNR of 63 dB, and programmable gain amplification of the photocurrent with 0–60 dB. Finally, the system is used for PD acoustic signal acquisition in the frequency range of 20 Hz to 100 kHz.

Enhanced microwave absorption and corrosion resistance of carbonyl iron encapsulated by silicone modified epoxy resin

The novel silicone modified epoxy resin (ER) was synthesized and used to encapsulate the carbonyl iron powders (CIP) with core–shell structure by in-situ polymerization method. The silicone modified epoxy resin coating was introduced to enhance both microwave absorption and corrosion resistance of carbonyl iron. Microstructure analysis demonstrated that CIP were densely covered with ER shell. Hydroxyl (–OH) and amino group (–NH2) present in silicone-modified epoxy resin, and chemically interact with the metal oxide layer on carbonyl iron to form covalent bonds or hydrogen bonds, improving interfacial adhesion and uniform dispersion of CIP. The ER shell effectively strengthens the microwave absorption ability and corrosion resistance of CIP. The reflection loss peak reached − 52.1 dB and effective absorption bandwidth achieved 7.8 GHz (10.2 GHz − 18 GHz). The epoxy resin coating significantly reduced the charge transfer resistance (Rct) and corrosion current density (Jcorr), indicating improved corrosion protection. Polarization resistance (Rp) and corrosion rate (CR) analysis further verified corrosion resistance. The epoxy resin-coated CIP exhibit excellent microwave absorption and corrosion resistance, indicating widespread application in anti-electromagnetic interference field.

A dual‐resonance enhanced photoacoustic spectroscopy gas sensor based on a fiber optic cantilever beam microphone and a spherical photoacoustic cell

AbstractWe propose a novel high‐performance dual‐resonance enhanced photoacoustic spectroscopy (DRE‐PAS) gas sensor based on a highly sensitive fiber optic cantilever beam microphone and a high‐Q spherical photoacoustic cell (PAC). The first‐order resonant frequency (FORF) of the spherical PAC is analyzed by finite element analysis to match the FORF of the cantilever microphone for the double resonance enhancement of the photoacoustic signal. The photoacoustic spectroscopy (PAS) system, including the DRE‐PAS sensor, a 1532.8 nm distributed feedback laser, and a high‐speed spectrometer, has been successfully exploited for trace acetylene (C2H2) detection. The experimental results show that the limit of detection (LOD) is 106.8 parts‐per‐billion (ppb) with an integral time of 1 s, and the LOD can be further reduced to 11.03 ppb by Allan‐Werle deviation for 100 s integral time. The normalized noise equivalent absorption coefficient can be obtained as 2.44 × 10−8 cm−1 WHz−1/2. The reported DRE‐PAS gas sensor has the superior characteristics of photoacoustic signal enhancement, high sensitivity, and strong antielectromagnetic interference capability, which can provide a new solution for PAS development.

Recent progress of optical tactile sensors: A review

Over the past decade, flexible electronics has become a cutting-edge technology owing to its broad applications in robotics, health monitoring, and human-machine interface. The recent development of flexible electrical tactile sensor triggers the research of optical tactile sensors due to their potentials in high-sensitivity, high-precision, low power consumption, and anti-electromagnetic interference. Here, this review mainly discusses the advances and applications of silica fiber, polymer fiber, hydrogel, and micro/nanofiber based tactile sensors, specifically, focusing on the latest research results and on the necessary technologies to enable the health monitoring, robotics, and human-machine interface applications. Furthermore, future outlooks in developing skin-like optical tactile sensors are also presented.

Fiber-Optic Photoacoustic CO Sensor for Gas Insulation Equipment Monitoring Based on Cantilever Differential Lock-In Amplification and Optical Excitation Enhancement.

A fiber-optic photoacoustic CO sensor for gas insulation equipment is proposed, which relies on F-P interferometric cantilever-based differential lock-in amplification and optical multipass excitation enhancement. The sensor has excellent characteristics of high sensitivity, antielectromagnetic interference, fast response, and long-distance detection. The photoacoustic pressure waves in the two resonators of the differential photoacoustic cell (DPAC) are simultaneously detected by two fiber-optic interferometric cantilevers and processed differentially; thereby, the gas flow noise is effectively suppressed. Based on the comprehensive analysis of the superposition of photoacoustic excitation and multipass absorption, the diameter of the resonator is determined to be 6 mm. The optical power emitted by the 1566.6 nm distributed feedback laser is increased to 500 mW by an erbium-doped fiber amplifier. The near-infrared light is reflected 30 times in the multipass cell, which improves the order of magnitude of optical effective excitation. Due to the low sound velocity of SF6 gas, the resonant frequency of the DPAC with a resonator length of 80 mm is 760 Hz. The response time to CO/SF6 gas is 93 s with a flow rate of 500 sccm. The detection limit of the CO sensor is 53 ppb, which realizes the accurate and timely perception of the SF6 decomposition derivative CO and provides technical support for trouble-free operation of gas insulation equipment.

A Self-Healing Optoacoustic Patch with High Damage Threshold and Conversion Efficiency for Biomedical Applications.

Compared with traditional piezoelectric ultrasonic devices, optoacoustic devices have unique advantages such as a simple preparation process, anti-electromagnetic interference, and wireless long-distance power supply. However, current optoacoustic devices remain limited due to a low damage threshold and energy conversion efficiency, which seriously hinder their widespread applications. In this study, using a self-healing polydimethylsiloxane (PDMS, Fe-Hpdca-PDMS) and carbon nanotube composite, a flexible optoacoustic patch is developed, which possesses the self-healing capability at room temperature, and can even recover from damage induced by cutting or laser irradiation. Moreover, this patch can generate high-intensity ultrasound (> 25MPa) without the focusing structure. The laser damage threshold is greater than 183.44mJcm-2, and the optoacoustic energy conversion efficiency reaches a major achievement at 10.66 × 10-3, compared with other carbon-based nanomaterials and PDMS composites. This patch is also been successfully examined in the application of acoustic flow, thrombolysis, and wireless energy harvesting. All findings in this study provides new insight into designing and fabricating of novel ultrasound devices for biomedical applications.

Belt conveyor speed detection based on fiber-optic Sagnac interferometer vibration sensor

With their long transportation distance and high productivity, belt conveyors are characterized as the main equipment for bulk material transportation in coal mines and other key industries. However, its speed detection method has always been an engineering challenge under harsh working conditions. In this work, the elastic-optical effect of the polarization-maintaining fiber is used to design a fiber ring laser vibration sensing system based on a fiber-optic Sagnac interferometer vibration sensor and its packaging structure. The vibration detection is achieved by detecting the change in optical power at the working wavelength, and the belt conveyor speed measurement is completed by detecting the vibration frequency. With such a method, the belt conveyor speed measurement obtained a relative error of less than 1.88%. The proposed method bears the characteristics of anti-electromagnetic interference, intrinsic explosion-proof, and adapts to the harsh smoke and dust working environment, which has a wide range of application prospects in the fields of engineering, machinery, security, etc.

Cantilever enhanced fiber-optic photoacoustic microprobe for diffusion detection of sulfur dioxide

A cantilever enhanced fiber-optic photoacoustic microprobe with the cavity volume of only 119 μL is designed to detect SO2, which has the obvious advantages of passive sensing, anti-electromagnetic interference and low cost. A UV multi-mode fiber and a single-mode fiber are applied to transmit excitation light emitted by UV-LED and probe light, respectively. The lens assembly based on a collimating lens and a focusing lens is added to improve the light energy of UV-LED coupling into UV-fiber. Based on theoretical analysis and finite element method, a photoacoustic cavity with a radius of 1.5 mm and a length of 15 mm is designed, which is conducive to the realization of photoacoustic enhancement and rapid response at high frequencies. SO2 gas diffuses into the PA cavity through a hole with the diameter of 0.5 mm and a gap of the cantilever with the width of 0.5 µm. A fiber-optic cantilever based on F-P interference is adopted to detect sound pressure. The frequency characteristic and response time of the sensor in different backgrounds of SF6 and N2 are analyzed experimentally. Compared with N2, the photoacoustic microprobe operates in SF6 background with lower resonance frequency and longer response time, which is due to the high density and low thermal diffusivity of SF6 gas. With the flow rate of 250 SCCM in the external cavity, the response time of the photoacoustic microprobe to SO2/SF6 and SO2/N2 are 96 s and 40 s, respectively. The detection limits of SO2 in SF6 and N2 background are 35 ppb and 5 ppb, respectively.

Optical fiber high-temperature pressure sensor with weak temperature sensitivity

In aerospace, petrochemical, gas turbines and other high-temperature environments, pressure measurement of equipment has always been a challenge to be solved. The electrical high temperature pressure sensor has the problem of component failure in high temperature environment, and it is difficult to use in the high temperature environment for a long time. The detection device of the optical fiber sensor does not include electrical components, so it has the advantages of high working temperature, high measurement accuracy, anti-electromagnetic interference and so on. In order to use a sensor to measure pressure in high temperature environment, a temperature-weakly sensitive optical fiber micro-electro-mechanical system (MEMS) pressure sensing technology is proposed. The technique uses extrisic Fabry-Pérot interference (EFPI) model. It uses the MEMS pressure chip to passively modulate the optical signal of the interference, and then realizes the pressure signal measurement. Among them, MEMS pressure sensitive chip is the core component of the sensor. The MEMS pressure sensitive chip adopts the design method of all solid state vacuum absolute pressure. Change in environmental pressure will deform the membrane. This phenomenon can cause change in the cavity of the EFPI cavity. Therefore, stress information can be obtained by measuring changes in EFPI cavity. The thermal stress and temperature parasitical response introduced by thermal expansion of the material are calculated by simulation. The influence of temperature signal on chip displacement is analyzed by the above results. On this basis, a prototype of high temperature pressure sensor is developed by combining the sub-micron white light interference response technology and low thermal stress packaging technology. In order to test the ability of the sensor to implement actual measurement, this paper carry out the pressure test and high temperature test respectively. When the pressure changes from 0 kPa to 100 kPa, the spectral intensity of the sensor output has a linear relationship with the pressure. During the temperature changing from 20–400 ℃, the spectral intensity of the sensor output does not change significantly. The experimental test results show that the pressure measurement of 0–100 kPa can be satisfied in the range of 20–400 ℃, and the measurement error introduced by temperature change is less than 4%. Therefore, the fiber pressure sensor can be used to measure the pressure in high temperature environment.

Multifunctional Ni/PDMS-coated magnesium plates with highly efficient anti-electromagnetic interference design

Multifunctional Ni/PDMS-coated magnesium plates with highly efficient anti-electromagnetic interference design

Multifunctional Ni/PDMS-coated Magnesium Plates with Highly Efficient Anti-Electromagnetic Interference Design

Multifunctional Ni/PDMS-coated Magnesium Plates with Highly Efficient Anti-Electromagnetic Interference Design

Experimental research on signal sensing of distributed acoustic sensing optical fiber based on Φ-OTDR in shallow water

The distributed acoustic sensing (DAS) technology based on phase-sensitive optical time domain reflectometry (Φ-OTDR) has been widely and well applied on land. Meanwhile, the distributed acoustic sensing optical fiber (DASF) based on Φ-OTDR, as a new type of sensor, is still in the initial stage of research, gets much attention in recent years because of its long-distance monitoring, high sensitivity, anti-electromagnetic interference, good concealment and so on. Performances of DASF in sensing different kinds of acoustic source signals were given by experiments in shallow water, which included single frequency pulse signal in the fixed position, the moving single frequency continuous pulse signal, the moving broadband signal, and the signal generated by the sailing surface target. Depth of the active sound source was changed to examine the performance of DASF in sensing signals in different depths. The specific experimental process was given, and the experimental results were processed and analyzed. Additionally, wave components of data generated from of the sailing surface vessel were explored with the time delay difference between the equivalent array elements of DASF. Results show that DASF can sense the above varieties of underwater acoustic signals well, and the physical field generated by the sailing surface vessel in shallow water include acoustic field and flow field, in which the propagation velocity of the former is faster than that of the latter.

Research Status and Trend of Axis-torsion Two-Component Force Senso

Axis-torsion two-component force sensor can simultaneously detect axial force and torque component information. With the progress of modern engineering technology and the improvement of the requirements for measurement accuracy and dynamic response ability, the sensor is widely used in many fields such as industry, national defense science and technology, and medical treatment. The axis-torsion twocomponent force sensor based on the measurement principles of resistance strain type, capacitance type and magnetostrictive effect is introduced. Because the resistance strain type axis-torsion two-component force sensor has a high degree of accuracy, good stability, simple structure and strong anti-electromagnetic interference ability, the resistance strain type axis-torsion two-component force sensor is the most widely used and the most technologically mature class of sensor. The structural characteristics of the elastic body of the combined and integral axis-torsion two-component force sensor are summarized. At present, the elastic body structure of the axis-torsion two-component force sensor is mainly studied and improved. The purpose is to improve the sensor’s measurement accuracyand reduce the inter-dimensional coupling error, so as to achieve accurate measurement in practical applications. The application status of the axis-torsion two-component force sensor in the cutting force detection, torque coefficient detection of high-strength bolted joints, and quantitative analysis of traditional Chinese medicine acupuncture techniques were analyzed. Finally, combined with the research and application status of the axis-torsion two-component force sensor, the development trend of the axis-torsion two-component force sensor is prospected.

All-optical photoacoustic detection of SF6 decomposition component SO2 based on fiber-coupled UV-LED

An all-optical photoacoustic sensor for measuring the concentration of SF6 decomposition derivative SO2 was designed, whose detection limit was in the order of ppb-level. An UV-fiber and a single-mode fiber were utilized to transmit excitation light and probe light, respectively. The technical scheme of all-optical gas sensing has realized the competitive advantages of long-distance detection and anti-electromagnetic interference. As an UV-LED was the excitation light, the challenge of designing all-optical SO2 sensor was to effectively couple UV-LED with large divergence angle into an UV- fiber. Theoretical calculation and experiment have proved that the lens assembly as an effective strategy to realize the efficient coupling and beam collimation, which can achieve high excitation power and low solid photoacoustic background interference. The lens assembly with high focusing property was the key to improve the signal-to-noise ratio (SNR) by 5.2 times. To detect photoacoustic pressure with high sensitivity, a fiber optic cantilever acoustic sensor based on F-P interference was designed. Based on the demodulation algorithm of white light interference, dynamic cavity length of F-P was demodulated with high-resolution. Allan-Werle analysis result indicate that the detection limit of SO2 gas was 48 ppb with an averaging time of 100 s

Functional near-infrared spectroscopy in non-invasive neuromodulation.

Non-invasive cerebral neuromodulation technologies are essential for the reorganization of cerebral neural networks, which have been widely applied in the field of central neurological diseases, such as stroke, Parkinson's disease, and mental disorders. Although significant advances have been made in neuromodulation technologies, the identification of optimal neurostimulation parameters including the cortical target, duration, and inhibition or excitation pattern is still limited due to the lack of guidance for neural circuits. Moreover, the neural mechanism underlying neuromodulation for improved behavioral performance remains poorly understood. Recently, advancements in neuroimaging have provided insight into neuromodulation techniques. Functional near-infrared spectroscopy, as a novel non-invasive optical brain imaging method, can detect brain activity by measuring cerebral hemodynamics with the advantages of portability, high motion tolerance, and anti-electromagnetic interference. Coupling functional near-infrared spectroscopy with neuromodulation technologies offers an opportunity to monitor the cortical response, provide real-time feedback, and establish a closed-loop strategy integrating evaluation, feedback, and intervention for neurostimulation, which provides a theoretical basis for development of individualized precise neurorehabilitation. We aimed to summarize the advantages of functional near-infrared spectroscopy and provide an overview of the current research on functional near-infrared spectroscopy in transcranial magnetic stimulation, transcranial electrical stimulation, neurofeedback, and brain-computer interfaces. Furthermore, the future perspectives and directions for the application of functional near-infrared spectroscopy in neuromodulation are summarized. In conclusion, functional near-infrared spectroscopy combined with neuromodulation may promote the optimization of central neural reorganization to achieve better functional recovery from central nervous system diseases.

UAV-assisted FSO communication system with amplify-and-forward protocol under AOA fluctuations: A performance analysis

Free space optical (FSO) communication has recently aroused great interest in academia due to its unique features, such as large transmission band, high data rates, and strong anti-electromagnetic interference. With the aim of evaluating the performance of an FSO communication system and extending the line-of-sight transmission distance, we propose an unmanned aerial vehicle (UAV)-assisted dual-hop FSO communication system equipped with amplify-and-forward protocol at the relay node. Specifically, we consider impairments of atmospheric absorption, pointing errors, atmospheric turbulence, and link interruptions due to angle-of-arrival fluctuations in the relay system. The Gamma-Gamma and Malaga distributions are used to model the influence of atmospheric turbulence on the source-to-UAV and UAV-to-destination links, respectively. We derive closed-form expressions of the probability density function (PDF) and cumulative distribution function (CDF) for the proposed communication system, in terms of the Meijer-G function. Based on the precise PDF and CDF, analytical expressions for the outage probability, average bit error rate, and ergodic capacity are proposed with the aid of the extended generalized bivariate Fox's H function. Finally, we show that there is a match between the analytical results and numerical results, and we analyze the influence of the system and channel parameters on the performance.