Showing papers in "Sensor Review in 2022"

Smart knife: technological advances towards smart cutting tools in meat industry automation

Abstract: Purpose Modern meat processing requires automation and robotisation to remain sustainable and adapt to future challenges, including those brought by global infection events. Automation of all or many processes is seen as the way forward, with robots performing various tasks instead of people. Meat cutting is one of these tasks. Smart novel solutions, including smart knives, are required, with the smart knife being able to analyse and predict the meat it cuts. This paper aims to review technologies with the potential to be used as a so-called “smart knife” The criteria for a smart knife are also defined. Design/methodology/approach This paper reviews various technologies that can be used, either alone or in combination, for developing a future smart knife for robotic meat cutting, with possibilities for their integration into automatic meat processing. Optical methods, Near Infra-Red spectroscopy, electrical impedance spectroscopy, force sensing and electromagnetic wave-based sensing approaches are assessed against the defined criteria for a smart knife. Findings Optical methods are well established for meat quality and composition characterisation but lack speed and robustness for real-time use as part of a cutting tool. Combining these methods with artificial intelligence (AI) could improve the performance. Methods, such as electrical impedance measurements and rapid evaporative ionisation mass spectrometry, are invasive and not suitable in meat processing since they damage the meat. One attractive option is using athermal electromagnetic waves, although no commercially developed solutions exist that are readily adaptable to produce a smart knife with proven functionality, robustness or reliability. Originality/value This paper critically reviews and assesses a range of sensing technologies with very specific requirements: to be compatible with robotic assisted cutting in the meat industry. The concept of a smart knife that can benefit from these technologies to provide a real-time “feeling feedback” to the robot is at the centre of the discussion.

A review: electrical and gas sensing properties of polyaniline/ferrite nanocomposites

Abstract: Purpose This paper aims to study the various developments taking place in the field of gas sensors made from polyaniline (PANI) nanocomposites, which leads to the development of high-performance electrical and gas sensing materials operating at room temperature. Design/methodology/approach PANI/ferrite nanocomposites exhibit good electrical properties with lower dielectric losses. There are numerous reports on PANI and ferrite nanomaterial-based gas sensors which have good sensing response, feasible to operate at room temperature, requires less power and cost-effective. Findings This paper provides an overview of electrical and gas sensing properties of PANI/ferrite nanocomposites having improved selectivity, long-term stability and other sensing performance of sensors at room temperature. Originality/value The main purpose of this review paper is to focus on PANI/ferrite nanocomposite-based gas sensors operating at room temperature.

Integrated solid-state wearable sweat sensor system for sodium and potassium ion concentration detection

Abstract: Purpose Design, fabricate and evaluate all-solid-state wearable sensor systems that can monitor ion concentrations in human sweat to provide real time health analysis and disease diagnosis capabilities. Design/methodology/approach A human health monitoring system includes disposable customized flexible electrode array and a compact signal transmission-processing electronic unit. Findings Patterned rGO (reduced-graphene oxide) layers can replace traditional metal electrodes for the fabrication of free-standing all solid film sensors to provide improved flexibility, sensitivity, selectivity, and stability in ion concentration monitoring. Electrochemical measurements show the open circuit potential of current selective electrodes exhibit near Nernst responses versus Na+ and K+ ion concentration in sweat. These signals show great stability during a typical measurement period of 3 weeks. Sensor performances evaluated through real time measurements on human subjects show strong correlations between subject activity and sweating levels, confirming high degree of robustness, sensitivity, reliability and practicality of current sensor systems. Originality/value In improving flexibility, stability and interfacial coherency of chemical sensor arrays, rGO films have been the developed as a high-performance alternative to conventional electrode with significant cost and processing complexity reduction. rGO supported solid state electrode arrays have been found to have linear potential response versus ion concentration, suitable for electrochemical sensing applications. Current sweat sensor system has a high degree of integration, including electrode arrays, signal processing circuits, and data visualization interfaces.

Design and evaluation of a micro resonator structure as a biosensor for droplet analysis with a standard fabrication method

Abstract: Purpose In this work, the sensing and actuating elements are designed with interdigitated capacitors away from the sensitive element on which the droplet is placed. This pattern helps to prevent interference of electrical elements with the droplet. Choosing shear resonance mode at this proposed structure minimizes the damping effect of droplet touch by the resonator structure. The glass-based standard fabrication method of the proposed biosensor is presented exactly. Design/methodology/approach Mechanical resonator sensors are extremely limited because of the high damping factor and the high electrical conductivity in the aqueous environment. In this work, a molecule detector biosensor is proposed for droplet analysis, which is possible to fabricate using micro-electro-mechanical systems (MEMS) technology. By electromechanical coupling of resonators as a mechanical resonator structure, a standing mechanical wave is formed at this structure by electrostatic actuating elements. Findings In this paper, a mechanical resonator structure as a biosensor is proposed for micro-droplet analysis that can be fabricated by MEMS technology. It is designed at a lower cost fabrication method using electrostatic technology and interdigitated capacitors. The response of the biosensor displacement frequency at the resonance frequency of the desired mode is reasonable for measuring the capacitive changes of its output. The mass sensitivity of the proposed biosensor is in the range of 1 ng, and it has a large sensitive area for capturing target molecules. Originality/value To evaluate the quality of the proposed design, the stimulated analysis is conducted by COMSOL and results are presented.

Ultrasonic diagnosis method for stainless steel weld defects based on multi-domain feature fusion

Abstract: Purpose This paper aims to propose a new ultrasonic diagnosis method for stainless steel weld defects based on multi-domain feature fusion to solve two problems in the ultrasonic diagnosis of austenitic stainless steel weld defects. These are insufficient feature extraction and subjective dependence of diagnosis model parameters. Design/methodology/approach To express the richness of the one-dimensional (1D) signal information, the 1D ultrasonic testing signal was derived to the two-dimensional (2D) time-frequency domain. Multi-scale depthwise separable convolution was also designed to optimize the MobileNetV3 network to obtain deep convolution feature information under different receptive fields. At the same time, the time/frequent-domain feature extraction of the defect signals was carried out based on statistical analysis. The defect sensitive features were screened out through visual analysis, and the defect feature set was constructed by cascading fusion with deep convolution feature information. To improve the adaptability and generalization of the diagnostic model, the authors designed and carried out research on the hyperparameter self-optimization of the diagnostic model based on the sparrow search strategy and constructed the optimal hyperparameter combination of the model. Finally, the performance of the ultrasonic diagnosis of stainless steel weld defects was improved comprehensively through the multi-domain feature characterization model of the defect data and diagnosis optimization model. Findings The experimental results show that the diagnostic accuracy of the lightweight diagnosis model constructed in this paper can reach 96.55% for the five types of stainless steel weld defects, including cracks, porosity, inclusion, lack of fusion and incomplete penetration. These can meet the needs of practical engineering applications. Originality/value This method provides a theoretical basis and technical reference for developing and applying intelligent, efficient and accurate ultrasonic defect diagnosis technology.

Fabrication and characterization of screen printed NiMn2O4 spinel based thermistors

Abstract: Purpose The purpose of this work was to characterize NiMn2O4 spinel-based thermistor powder, to use it in screen printing technology to fabricate temperature sensors, to study their performance for different sintering temperatures of thermistor layer, with and without insulative cover, as well as to investigate stability of the fabricated thermistors and their applicability in water quality monitoring. Design/methodology/approach After the characterization of starting NiMn2O4 spinel-based thermistor powder, it was converted to thick film paste which was screen printed on alumina substrate. Thermistor layers were sintered at four different sintering temperatures: 980°C, 1050°C, 1150°C and 1290°C. An interdigitated pattern of Ag-Pd conductive layer was used to reduce the resistance. Temperature-resistance characteristics were investigated in air and water, with and without insulative cover atop the thermistor layer. Stability of the fabricated thermistors after aging at 120°C for 300 h was also examined. Findings Thick film NiMn2O4 spinel thermistors, prepared by screen printing and sintering in the temperature range 980°C–1290°C, exhibited good negative temperature coefficient (NTC) characteristics in the temperature range −30°C to 145°C, including high temperature coefficient of resistance, good stability and applicability in water. Originality/value This study explores the range of sintering temperature that can be applied for NiMn2O4 thermistor thick films without compromising on the temperature sensing performance in air and water, as well as stability of the thermistors after aging at elevated temperatures.

Cantilever enhanced based photoacoustic detection of SF₆ decomposition component SO₂ using UV LED

Abstract: Purpose This paper aims to establish a photoacoustic detection system for SO 2 using UV-LED and testify its feasibility for sensitive measurement. The work in this paper can avoid potential crossover interference in infrared (IR) range and also balance the capability and cost of feasible excitation for photoacoustic detection system. Design/methodology/approach In this experimental work, a cantilever-enhanced–based photoacoustic SO 2 detection system using an ultraviolet (UV) LED light source with a light power of 4 mW as the excitation was established. Findings A feasible photoacoustic detection system for SO 2 using UV-LED was established. Experimental results demonstrate that the detection limit of the system can reach the level of 0.667 ppm, which can serve as a reference for the application of PAS in insulation fault diagnosis. Originality/value This work investigated the potential of using ultraviolet photoacoustic spectroscopy to detect trace SO 2 , which provided an ideal replacement of infrared-laser-based detection system. In this paper, a photoacoustic detection system using LED with a low light power was established. Low light power requirement can expand the options of light sources accordingly. In this paper, the absorption characteristics of SO 2 in the presented detection system and ultraviolet range were studied. And the detection limit of the presented system was given. Both of which can provide reference to SO 2 detection in ambient SF 6 .

Fabrication and testing of a Hall effect based pressure sensor

Abstract: Purpose This paper aims to present the fabrication and testing of a pressure sensor integrated with Hall effect sensors and permanent magnets arranged in two configurations to measure pressure in the range of 0–1 bar. The sensor is fabricated using stainless steel (SS) and can be used in high-temperature and highly corrosive environments. The fabricated sensor is of low cost, self-packaged and the differential arrangement helps in compensating for any ambient temperature variations. Design/methodology/approach The sensor deflects of a circular diaphragm with a simple rigid mechanical structure to convert the applied pressure to a Hall voltage output. Two sensor designs are proposed with a single pair of Hall sensors and magnets and a differential configuration with two Hall sensors and magnets. Two sensor designs are designed, fabricated and tested for their input–output characteristics and the results are compared. Findings The fabricated sensors are calibrated for 25 cycles of ascending and descending pressure in steps of 0.1 bar. Various static characteristics like nonlinearity, hysteresis and % error are estimated for both the sensor designs and compared with the existing Hall effect based pressure sensors. The differential arrangement design was found to have better characteristics as compared to the other design from the experimental data. Originality/value This paper focuses on fabricating and testing a novel differential Hall effect based pressure sensor. The differential arrangement of the sensor aids in the compensation of ambient temperature variations and the use of SS enables the sensor in high-temperature and highly corrosive applications. The proposed sensor is low cost, simple and self-packaged, and found to have high repeatability and good linearity compared to other similar Hall effect based pressure sensors available in the literature.

An active compliant docking method for large gear components based on distributed force sensor

Abstract: Purpose Large gear components widely exist in the transmission system of helicopters, ships, etc. Due to the small assembly clearance of large gear components, using an automatic docking system based on position control will lead to forced assembly. The purpose of this paper is to reduce the assembly stress of large gear components by an active compliant docking technology based on distributed force sensors. Design/methodology/approach Firstly, aiming at the noise interference in three-dimensional force sensor (TDFS), Kalman filter and Savitzky–Golay filter are used to process the sensor’s output signal. Secondly, the active compliant docking control model is constructed according to the principle of impedance control. Thirdly, the contact force is calculated based on the Euler equation, and the impedance control parameters are tuned by the particle swarm optimization algorithm. Finally, an active compliant docking system of a large gear structure based on distributed force sensor is built in the laboratory to verify the proposed method. Findings The experimental results show that the contact force and contact torque gradually decrease in all directions and are always in the safe range during the docking process. The feasibility of this method in practical application is preliminarily demonstrated. Originality/value The distributed TDFSs are used to replace the traditional six-dimensional force sensor in the active compliant docking system of gear components, which solves the problem of the small bearing capacity of the conventional active compliant docking system. This method can also be used for the docking of other large components.

A quantitative crack monitoring method based on crack disturbed voltage

Abstract: Purpose The flexible eddy current array sensor has the characteristics of lightweight and flexibility, which has a great application prospect in the field of fatigue crack monitoring. But the exciting layout and feature signal extraction have a great influence on the crack monitoring characteristics of the sensor. This paper aims to propose a method using crack disturbed voltage as sensitivity to characterize crack propagation. Design/methodology/approach Flexible eddy current array sensors with reverse and codirectional exciting layout are proposed, and the advantages and disadvantages of three characterization methods based on the change of trans-impedance amplitude, the change of the trans-impedance’s real and imaginary part and the crack disturbed voltage are compared and analyzed by finite element simulation. Finally, the fatigue crack monitoring experiment is carried out. Findings The crack disturbed voltage and the change of trans-impedance’s imaginary part can effectively characterize the crack propagation for sensors with different exciting layouts. The codirectional exciting layout sensor has better crack identification sensitivity than the reverse exciting layout sensor, especially the induction coil 2. When the distance between the exciting coil and the induction coil is 0.1, 0.2 and 0.3 mm, it is increased by 372.09%, 295.24% and 231.43%, respectively. Originality/value Crack disturbed voltage can effectively characterize the crack propagation for sensors with two different exciting layouts.

Plantar pressure measurement system based on piezoelectric sensor: a review

Abstract: Purpose Plantar force is the interface pressure existing between the foot plantar surface and the shoe sole during static or dynamic gait. Plantar force derived from gait and posture plays a critical role for rehabilitation, footwear design, clinical diagnostics and sports activities, and so on. This paper aims to review plantar force measurement technologies based on piezoelectric materials, which can make the reader understand preliminary works systematically and provide convenience for researchers to further study. Design/methodology/approach The review introduces working principle of piezoelectric sensor, structures and hardware design of plantar force measurement systems based on piezoelectric materials. The structures of sensors in plantar force measurement systems can be divided into four kinds, including monolayered sensor, multilayered sensor, tri-axial sensor and other sensor. The previous studies about plantar force measurement system based on piezoelectric technology are reviewed in detail, and their characteristics and performances are compared. Findings A good deal of measurement technologies have been studied by researchers to detect and analyze the plantar force. Among these measurement technologies, taking advantage of easy fabrication and high sensitivity, piezoelectric sensor is an ideal candidate sensing element. However, the number and arrangement of the sensors will influence the characteristics and performances of plantar force measurement systems. Therefore, it is necessary to further study plantar force measurement system for better performances. Originality/value So far, many plantar force measurement systems have been proposed, and several reviews already introduced plantar force measurement systems in the aspect of types of pressure sensors, experimental setups for foot pressure measurement analysis and the technologies used in plantar shear stress measurements. However, this paper reviews plantar force measurement systems based on piezoelectric materials. The structures of piezoelectric sensors in the measurement systems are discussed. Hardware design applied to measurement system is summarized. Moreover, the main point of further study is presented in this paper.

Development of an inkjet-printed electrochemical nanosensor for ascorbic acid detection

Abstract: Purpose Ascorbic acid (AA) is an essential vitamin for human health. Therefore, fast and cost-effective detecting of AA is essential, whether in human or food samples. The purpose of this paper is to develop an electrochemical nanosensor for AA detection. Design/methodology/approach The proposed nanosensor was developed by printing carbon nanoparticles ink and silver nanoparticles ink on a polydimethylsiloxane (PDMS) substrate. The surface of the PDMS substrate was first treated by corona plasma. Then, the nanomaterials printer was used to deposit both inks on the substrate. The working electrode surface was modified by drop-casting of carbon nanotubes. Morphological evaluation was applied using scanning electron microscopy and cyclic voltammetry. Also, a potentiostat was used to detect AA by differential pulse voltammetry. Findings It has been shown that the developed nanosensor linearly worked at a range of (0–5 mM), with a limit of detection lower than 0.8 mM and a relative standard deviation of 6.6%. Originality/value The developed nanosensor is characterized by a simple and cost-effective sensing tool for AA. In particular, the nanomaterials enhanced the nanosensor’s sensitivity due to the high catalytic activity.

Application of SCADA data in wind turbine fault detection – a review

Abstract: Purpose With the rapid increase in the number of installed wind turbines (WTs) worldwide, requirements and expenses of maintenance have also increased significantly. The condition monitoring (CM) of WT provides a strong “soft guarantee” for preventive maintenance. The supervisory control and data acquisition (SCADA) system records a huge amount of condition data, which has become an effective means of CM. The main objective of the present study is to summarize the application of SCADA data to fault detection in wind turbines, analyze its advantages and disadvantages and predict the potential of future investigations on the use of SCADA data for fault detection. Design/methodology/approach The authors first review the means of WT CM and summarize the characteristics of CM based on SCADA data. To ensure the quality of SCADA data, data preprocessing methods are analyzed and compared. Then, the failure modes of the key components are discussed and the SCADA data used for fault detection of each component are compared. Moreover, the fault detection methods for WT are classified and a general framework for fault detection is proposed. Finally, the issues in the WT fault detection method based on SCADA data are reviewed. Findings Based on the performed analyses, it is found that although the fault detection accuracy based on SCADA data is relatively poor, it has low capital expenses and low computational cost. More specifically, when there is scarce fault data, the normal SCADA data can be used to detect the fault time. However, the specific fault type cannot be identified in this way. When a large amount of fault data are accumulated in the SCADA system, it can not only detect the occurrence time of the fault but also identify the specific fault type. Originality/value The main contribution of the present study is to summarize the pre-processing methods for SCADA data, the data required for fault detection of key components and the characteristics of the fault detection model. Then we propose a general fault detection framework for wind turbines based on SCADA data, where the maintenance workers can choose the appropriate fault detection method according to different fault detection requirements and data resources. This article is expected to provide guidance for fault detection based on time-series sensor signals and be of interest to researchers, maintenance workers and managers.

A new type low-frequency FBG acceleration sensor based on cross reeds

Abstract: Purpose The purpose of this paper is to solve the problem of weak low-frequency vibration measurement capability of FBG accelerometer, and propose a FBG accelerometer based on cross reed. Design/methodology/approach This study proposed a new type FBG acceleration sensor based on cross reeds. When the sensor vibrates, the mass block in the new structure rotates around the center of the cross reeds, which could eliminate the impact of friction, reduce the natural frequency of the sensor and improve its sensitivity. This study theoretically analyzed the impact of several structural parameters on the sensitivity and natural frequency of the proposed sensor and used COMSOL to perform static stress analysis and modal simulation; in this study, a test system was built to test the performance of the proposed sensor. Findings The test results revealed that the proposed sensor had a natural frequency of 94 Hz; within a low-frequency range of 1–65 Hz, its sensitivity response was flat, the dynamic range was 81.89 dB, the sensitivity was 243.59 pm/g and the linearity was 99.97%. The cross reeds effectively strengthened the structural stability, the relative standard deviation of the repeatability of the sensor was 0.89% and the transverse crosstalk in the working frequency band was −26.97 dB. Originality/value This study innovatively proposes the structure of the two symmetrical cross reeds, which can improve sensitivity by eliminating the influence of friction, and the structure of cross reeds can effectively suppress the influence of lateral crosstalk. The proposed sensor can realize real-time accurate measurement of low-frequency weak vibration signals.

Simulation and experimental study of remote field current testing for hidden defects of aluminum alloy plate with damping coating

Abstract: Purpose Detection of hidden defects of aluminum alloy plate with damping coating is a challenging problem. At present, only a few non-destructive testing methods exist to address this engineering problem. Without the restriction of skin effect, remote field eddy current (RFEC) overcomes the interference caused by the damping coating. The RFEC, which has potential advantages for detecting the hidden defects of aluminum plate with damping coating, can penetrate the metal plate to detect buried depth defects. This study aims to test how thick the RFEC sensor can penetrate the metal plate to detect the buried defects. Design/methodology/approach The magnetic field distribution characteristics are analyzed, the magnetic field intensity distribution is calculated, and the structure and parameters of the coil, magnetic circuit and shielding damping are determined through the two- and three-dimensional finite element simulation methods. Optimal excitation frequency is obtained, and the distance between the excitation coil and detection coil is determined by analyzing the relationship between excitation frequency and remote field points. Findings Simulation and experimental results verify the feasibility of applying the RFEC detection technology in detecting the hidden defects of aluminum alloy plate with damping coating. Originality/value In this paper, the RFEC testing model of hidden defects in aluminum plate sample with damping coating is established by using the finite element method.

Series and interactive sensing coil layouts for reducing sensing channels of flexible eddy current array sensor

Abstract: Purpose Flexible eddy current array (FECA) sensor is flexible and light in weight, which has broad application prospects in structural health monitoring. But, the sensor’s sensing channel number is more, increasing the added mass of sensor networks. This paper aims to reduce the sensing channel number by changing the sensing coil layout. Design/methodology/approach In this paper, FECA sensors with series sensing coil (SSC) layout and interactive sensing coil (ISC) layout are proposed, which reduce the number of sensor’s channels by half. Then, the variation of the output signal of the sensor when the crack expands along both sides of the hole is analyzed by simulation model. Finally, the fatigue crack monitoring experiment is carried out. Findings For the SSC layout, the simulation results show that the amplitude of each SSC group of the sensor increases when the crack propagates to the left or right. For the ISC layout, when the crack propagates on the right side of bolt hole, the induced voltage of each ISC group decreases. When the crack propagates on the left side of bolt hole, the induced voltage of each ISC group increases. The experiment results are consistent with simulation results, which verifies the correctness of simulation model. Compared with SSC layout, the ISC layout can judge the crack propagation direction. And the crack monitoring accuracy is 1 mm. Originality/value The research results provide a certain reference for reducing the number of sensor’s sensing channels. Results of the simulation and experiment show that the ISC layout can judge the crack propagation direction, and the crack monitoring accuracy is 1 mm.

Preparation and performance of CNTs-Pt formaldehyde sensor and CNTs-Au glucose sensor

Abstract: Purpose Since carbon nanotubes (CNTs) were discovered by Iijima in 1991, they have gained more and more attention by people because of their unique physical and chemical properties. The CNTs have one-dimensional nanostructure, high surface adsorption capacity, good conductivity and electronic ballistic transmission characteristics and therefore have excellent mechanical, electrical, physical and chemical properties. CNTs are ideal basic materials to make nanometer gas sensors. Nanometallic materials function as to enhance electrode activity and promote the electron transfer, so if composite nanometallic materials M (such as Au, Pt, Cu and Pd) and CNTs are used, all kinds of their characters of components would have coeffect. Electrochemical sensors by use of such composite as electrode would have a higher detection sensitivity. Design/methodology/approach CNTs were synthesized via chemical vapor deposition technique and were purified afterward. CNTs-M(Pt,Au) suspension was prepared by chemical deposition using spinning disc processor (SDP) and was coated on gold electrode. The modified electrodes were constructed, based on immobilization of glucose oxidase on an Au electrode by electrostatic effect. CNTs-Pt/ glassy carbon electrodes (GCE) electrodes were made by electrochemically deposition of platinum particles on GCE modified by CNTs. The microstructures of the harvested CNTs, CNTs-M (M = Au, Pt) were analyzed under scanning electron microscopy and transmission electron microscopy. The application of the sensor in medical detection has been evaluated. Findings The results shown that CNTs-Au biosensors exhibit good reproducibility, stability and fast response to glucose detection, it can be used in the clinic detection of glucose concentration in human serum. Using CNTs-Pt/GCE for formaldehyde detection exhibited high sensitivity and good reproducibility. Originality/value This study modified CNTs by using self-assembled techniques through SDP with nano Pt and Au by electrodeposition for the first time. CNTs-Pt/GCE electrode was prepared by depositing platinum particles electrochemically on GCE modified by CNTs. CNTs-Au-modified electrode was prepared by immobilization of glucose oxidase on an Au electrode first by electrostatic effect. Electrochemical behaviors of glucose at CNTs-Au and formaldehyde at CNTs-Pt/GCE were investigated by cyclic voltammetry.

A study on the thermal responsive behavior of hydrogel-based materials and their potential use in medical applications

Abstract: Purpose The purpose of this paper is to present synthesis protocol of hydrogel composed of Chitosan (CS) and Poly(ethylene glycol) (PEG) and establish an understanding of its thermal responsive behavior. It aims to prove the basic temperature sensing ability of a novel CS-PEG-based hydrogel and define its sensing span. Design/methodology/approach This study includes synthesis of CS and PEG-based hydrogel samples by first performing dissolution of both constituents, respectively, and then adding Glutaraldehyde as the cross-linking agent. It further includes proposed hydrogel’s swelling studies and dynamic behavior testing, followed by hydrogel characterization by Fourier transform infrared spectroscopy, X-ray diffraction and SEM. The last section focuses on the use of proposed hydrogel as a temperature sensor. Findings Detailed experimental results show that a hydrogel comprising of CS and PEG presents a thermally responsive behavior. It offers potential to be used as a temperature responsive hydrogel-based sensor which could be used in medical applications. Originality/value This research study presents scope for future research in the field of thermally responsive bio-sensors. It provides basis for the fabrication of a thermal responsive sensor system based on hydrogels that can be used in specific medical applications.

Detection algorithm of rail surface defects based on multifeature saliency fusion method

Abstract: Purpose Effective rail surface defects detection method is the basic guarantee to manufacture high-quality rail. However, the existed visual inspection methods have disadvantages such as poor ability to locate the rail surface region and high sensitivity to uneven reflection. This study aims to propose a bionic rail surface defect detection method to obtain the high detection accuracy of rail surface defects under uneven reflection environments. Design/methodology/approach Through this bionic rail surface defect detection algorithm, the positioning and correction of the rail surface region can be computed from maximum run-length smearing (MRLS) and background difference. A saliency image can be generated to simulate the human visual system through some features including local grayscale, local contrast and edge corner effect. Finally, the meanshift algorithm and adaptive threshold are developed to cluster and segment the saliency image. Findings On the constructed rail defect data set, the bionic rail surface defect detection algorithm shows good recognition ability on the surface defects of the rail. Pixel- and defect-level index in the experimental results demonstrate that the detection algorithm is better than three advanced rail defect detection algorithms and five saliency models. Originality/value The bionic rail surface defect detection algorithm in the production process is proposed. Particularly, a method based on MRLS is introduced to extract the rail surface region and a multifeature saliency fusion model is presented to identify rail surface defects.

ZnO-based chemi-resistive sensors for CO2 detection: a review

Abstract: Purpose Carbon dioxide (CO2) has attracted special scientific interest over the last years mainly because of its relation to climate change and indoor air quality. Except for this, CO2 can be used as an indicator of food freshness, patients’ clinical state and fire detection. Therefore, the accurate monitoring and controlling of CO2 levels are imperative. The development of highly sensitive, selective and reliable sensors that can efficiently distinguish CO2 in various conditions of temperature, humidity and other gases’ interference is the subject of intensive research with chemi-resistive zinc oxide (ZnO)-based sensors holding a privileged position. Several ZnO nanostructures have been used in sensing applications because of their versatile features. However, the deficient selectivity and long-term stability remain major concerns, especially when operating at room temperature. This study aims to encompass an extensive study of CO2 chemi-resistive sensors based on ZnO, introducing the most significant advances of recent years and the best strategies for enhancing ZnO sensing properties. Design/methodology/approach An overview of the different ZnO nanostructures used for CO2 sensing and their synthesis methods is presented, focusing on the parameters that highly affect the sensing mechanism and, thus, the performance of CO2 sensors. Findings The selectivity and sensitivity of ZnO sensors can be enhanced by adjusting various parameters during their synthesis and by doping or treating ZnO with suitable materials. Originality/value This paper summarises the advances in the rapidly evolving field of CO2 sensing by ZnO sensors and provides research directions for optimised sensors in the future.

Efficiency of temporal sensor data compression methods to reduce LoRa-based sensor node energy consumption

Abstract: Purpose Minimizing the energy consumption in a wireless sensor node is important for lengthening the lifetime of a battery. Radio transmission is the most energy-consuming task in a wireless sensor node, and by compressing the sensor data in the online mode, it is possible to reduce the number of transmission periods. This study aims to demonstrate that temporal compression methods present an effective method for lengthening the lifetime of a battery-powered wireless sensor node. Design/methodology/approach In this study, the energy consumption of LoRa-based sensor node was evaluated and measured. The experiments were conducted with different LoRaWAN data rate parameters, with and without compression algorithms implemented to compress sensor data in the online mode. The effect of temporal compression algorithms on the overall energy consumption was measured. Findings Energy consumption was measured with different LoRaWAN spreading factors. The LoRaWAN transmission energy consumption significantly depends on the spreading factor used. The other significant factors affecting the LoRa-based sensor node energy consumption are the measurement interval and sleep mode current consumption. The results show that temporal compression algorithms are an effective method for reducing the energy consumption of a LoRa sensor node by reducing the number of LoRa transmission periods. Originality/value This paper presents with a practical case that it is possible to reduce the overall energy consumption of a wireless sensor node by compressing sensor data in online mode with simple temporal compression algorithms.

Design of an electro-optical sensor with high sensitivity for AC electric field measurement

Abstract: Purpose This study aims to address the issue of high-precision measurement of AC electric field. An electro-optical sensor with high sensitivity is proposed for this purpose. Design/methodology/approach The proposed sensor combines electromagnetic induction and fiber Bragg grating (FBG) sensing techniques. It is composed of a sensing probe, a piece or stack of piezoelectric ceramics (PZT) and an FBG. A signal processing circuit is designed to rectify and amplify the induced voltage. The processed signal is applied to the PZT and the deformation of PZT is detected by FBG. Theoretical calculation and simulation are conducted to verify the working principle of the probe. The sensor prototype is fabricated and its performance is tested. Findings The results of this study show that the sensor has good linearity and repeatability. The sensor sensitivity is 0.061 pm/Vm−1 in the range from 250 to 17,500 V/m, enabling a measurement resolution of electric field strength of 16.3 V/m. The PZT stack is used to enhance the sensor sensitivity and the resolution can be improved up to 3.15 V/m. Originality/value A flexure hinge lever mechanism is used to amplify the deformation of PZT for further enhancement of sensitivity. The results show that the proposed sensor has high sensitivity and can be used for the accurate measurement of an electric field. The proposed sensor could have potential use for electric field measurement in the power industry.

Study of transmission characteristics for a long-period grating on plastic optical fibers and its refractive index sensing

Abstract: Purpose This study aims to analyze the transmission characteristics of a long-period grating (LPG) fabricated on plastic optical fibers (POFs) and its refractive index (RI) sensing. Design/methodology/approach The geometric optic method is used to analyze the factors affecting the transmission characteristics of an LPG on POFs. The RI sensing performances of unbent LPGs and U-bent LPGs fabricated on POFs with different diameters are evaluated experimentally. Findings This study shows that the transmission loss caused by LPG strongly depends on the structural parameters of LPG and the environmental RI. For the unbent LPG, the highest RI sensitivity of 1,015%/RI unit (RIU) was obtained in the RI range of 1.33–1.45. For the U-bent LPG without cladding, the highest RI sensitivities of 1,007 and 559%/RIU are obtained in the RI ranges of 1.33–1.40 and 1.40–1.45, respectively. Originality/value A geometric optic method is used to analyze the transmission characteristics for an LPG on POFs, and the RI sensing of the LPGs are studied experimentally. The results show the LPG has a good RI sensing performances and is with the features of low-cost, simple structure and easy fabrication.

Formaldehyde gas sensing using metal oxide semiconductor: a brief review

Abstract: Purpose This review aims to give an overview about zinc oxide (ZnO) based gas sensors and the role of doping in enhancing the gas sensing properties. Gas sensors based on ZnO thin film are preferred for sensing applications because of their modifiable surface morphology, very large surface-to-volume ratio and superior stability due to better crystallinity. The gas detection mechanism involves surface reaction, in which the adsorption of gas molecules on the ZnO thin film affects its conductivity and reduces its electrical properties. One way to enhance the gas sensing properties is by doping ZnO with other elements. A few of the common and previously used dopants include tin (Sn), nickel (Ni) and gallium (Ga). Design/methodology/approach In this brief review, previous works on doped-ZnO formaldehyde sensing devices are presented and discussed. Findings Most devices provided good sensing performance with low detection limits. The reported operating temperatures were within the range of 200̊C –400̊C. The performance of the gas sensors can be improved by modifying their nanostructures and/or adding dopants. Originality/value As of yet, a specific review on formaldehyde gas sensors based on ZnO metal semiconductors has not been done.

Research on compensation method for registration error of large-scale measurement field based on multi-temperature sensors

Abstract: Purpose The size of the aircraft tooling structure is huge, and the ambient temperature is difficult to maintain a constant state. Aiming at the influence of current temperature, this paper aims to propose a compensation method for registration error of large-scale measurement fields based on multi-temperature sensors. Design/methodology/approach In this method, an enhanced reference points (ERS)–temperature regression model is constructed from ERS and temperature data. The ERS offsets compensation model is established by solving the offset through the regression model, and the ERS offset compensation analysis is carried out. Findings The experimental results show that the proposed registration error compensation algorithm has obvious advantages over traditional methods in reducing the influence of ambient temperature and improving the measurement accuracy by reducing the registration error. Originality/value This method reduces registration error caused by the influence of ambient temperature and is used for aircraft measurements in different temperature environments.

The underground explosion point high precision measurement method based on multidimensional information fusion of vibration sensors

Abstract: Purpose The purpose of this paper is to solve the problem that the location of the initiation point cannot be measured accurately in the shallow underground space, this paper proposes a method, which is based on fusion of multidimensional vibration sensor information, to locate single shallow underground sources. Design/methodology/approach First, in this paper, using the characteristics of low multipath interference and good P-wave polarization in the near field, the adaptive covariance matrix algorithm is used to extract the polarization angle information of the P-wave and the short term averaging/long term averaging algorithm is used to extract the first break travel time information. Second, a hybrid positioning model based on travel time and polarization angle is constructed. Third, the positioning model is taken as the particle update fitness function of quantum-behaved particle swarm optimization and calculation is performed in the hybrid positioning model. Finally, the experiment verification is carried out in the field. Findings The experimental results show that, with root mean square error, spherical error probable and fitness value as evaluation indicators, the positioning performance of this method is better than that without speed prediction. And the positioning accuracy of this method has been improved by nearly 30%, giving all of the three tests a positioning error within 0.5 m and a fitness less than 1. Originality/value This method provides a new idea for high-precision positioning of shallow underground single source. It has a certain engineering application value in the fields of directional demolition of engineering blasting, water inrush and burst mud prediction, fuze position measurement, underground initiation point positioning of ammunition, mine blasting monitoring and so on.

Sensor-based human activity recognition using fuzzified deep CNN architecture with λmax method

Abstract: Purpose This work aims to develop a novel fuzzy associator rule-based fuzzified deep convolutional neural network (FDCNN) architecture for the classification of smartphone sensor-based human activity recognition. This work mainly focuses on fusing the λ max method for weight initialization, as a data normalization technique, to achieve high accuracy of classification. Design/methodology/approach The major contributions of this work are modeled as FDCNN architecture, which is initially fused with a fuzzy logic based data aggregator. This work significantly focuses on normalizing the University of California, Irvine data set’s statistical parameters before feeding that to convolutional neural network layers. This FDCNN model with λ max method is instrumental in ensuring the faster convergence with improved performance accuracy in sensor based human activity recognition. Impact analysis is carried out to validate the appropriateness of the results with hyper-parameter tuning on the proposed FDCNN model with λ max method. Findings The effectiveness of the proposed FDCNN model with λ max method was outperformed than state-of-the-art models and attained with overall accuracy of 97.89% with overall F1 score as 0.9795. Practical implications The proposed fuzzy associate rule layer (FAL) layer is responsible for feature association based on fuzzy rules and regulates the uncertainty in the sensor data because of signal inferences and noises. Also, the normalized data is subjectively grouped based on the FAL kernel structure weights assigned with the λ max method. Social implications Contributed a novel FDCNN architecture that can support those who are keen in advancing human activity recognition (HAR) recognition. Originality/value A novel FDCNN architecture is implemented with appropriate FAL kernel structures.

Research on the reliable test range of four-point supported piezoelectric dynamometer

Abstract: Purpose The purpose of this paper is to improve the reliability of the force measurement system by determining the reliable test range of dynamometer. Design/methodology/approach Based on the principle of leverage and moment balance, a general force distribution model is applicable in where the test point is located either inside or outside the support region of four three-component force links of dynamometer is established. After corroborating the correctness of the model through verification experiments, the boundary conditions that each three-component force link should satisfy are analyzed by considering the characteristic of the dynamometer components comprehensively. Furthermore, the reliable test range of dynamometer is determined, followed by a calibration experiment to verify its rationality. Findings The relationships between the reliable test range and the tested force, the bolt pre-tightening force and the bearing capacity of quartz wafers are clarified. Further, the experimental calibration results show that when the test point is within the reliable test range, the three-directional output voltage of dynamometer has excellent linearity and repeatability. The nonlinearity and repeatability in X-, Y- and Z-directions are all less than 1.1%. Originality/value A general mathematical model of force distribution of four three-component force links is constructed, which provides a theoretical basic for the mechanical analysis of multi-sensors’ dynamometer. Comprehensively considering the performance of dynamometer components, the value of measured force and the pre-tightening force, the simultaneous equations of reliable test range are deduced, which limits the boundary of allowable test position of piezoelectric dynamometer.

Underwater target passive acoustic localization method based on Hanbury Brown–Twiss interference

Abstract: Purpose Acoustic signals of the underwater targets are susceptible to noise, reverberation, submarine topography and biology, therefore it is difficult to precisely locate underwater targets. This paper proposes a new underwater Hanbury Brown-Twiss (HBT) interference passive localization method. This study aims to achieve precise location of the underwater acoustic targets. Design/methodology/approach The principle of HBT interference with ultrasensitive detection characteristics in optical measurements was introduced in the field of hydroacoustics. The coherence of the underwater target signal was analyzed using the HBT interference measurement principle, and the corresponding relationship between the signal coherence and target position was obtained. Consequently, an HBT interference localization model was established, and its validity was verified through simulations and experiments. Findings The effects of different array structures on the localization performance were obtained by simulation analysis, and the simulations confirmed that the HBT method exhibited a higher positioning accuracy than conventional beamforming. In addition, the experimental analysis demonstrated the excellent positioning performance of the HBT method, which verified the feasibility of the proposed method. Originality/value This study provides a new method for the passive localization of underwater targets, which may be widely used in the field of oceanic explorations.

Can kinematic variables deduce functional scales among chronic stroke survivors? A proof of concept for inertial sensors

Abstract: Purpose This study aims to leverage inertial sensors via a walk test to associate kinematic variables with functional assessment results among walkable subjects with chronic stroke. Design/methodology/approach Adults with first-ever stroke survivors were recruited for this study. First, functional assessments were obtained by using Fugl–Meyer Assessment for lower extremity and Berg balance scales. A self-assembled inertial measurement system obtained walking variables from a walk test after being deployed on subjects’ affected limbs and lower back. The average walking speeds, average range of motion in the affected limbs and a new gait symmetry index were computed and correlated with the two functional assessment scales using Spearman’s rank correlation test. Findings The average walking speeds were moderately correlated with both Fugl–Meyer assessment scales (γ = 0.62, p < 0.01, n = 23) and Berg balance scales (γ = 0.68, p < 0.01, n = 23). After being modified by the subjects’ height, the new gait symmetry index revealed moderate negative correlations with the Fugl–Meyer assessment scales (γ = −0.51, p < 0.05) and Berg balance scales (γ = −0.52, p < 0.05). The other kinematics failed to correlate well with the functional scales. Practical implications Neuromotor and functional assessment results from inertial sensors can facilitate their application in telemonitoring and telerehabilitation. Originality/value The average walking speeds and modified gait symmetry index are valuable parameters for inertial sensors in clinical research to deduce neuromotor and functional assessment results. In addition, the lower back is the optimal location for the inertial sensors.