Search

Highlights Recognizing the critical demand for composite bolts and the damage‐mode complexity of composite bolt joints, this study introduces the concept of an intelligent carbon fiber reinforced polymer (CFRP) bolt, which achieves self‐monitoring of damage in small and complex CFRP bolted joints. The proposed eddy current sensor (ECS) is mainly composed of a coil made of carbon nanotube film and encapsulated with epoxy resin film. This achieves homogeneous embedding of the sensor by using the same material for both sensor and bolt. The CFRP bolt is fabricated by molding process, with the proposed ECS embedded in bolt shank. The numerical simulation results indicate that hole‐edge damages impact the distribution of induced current density and eddy current flow in CFRP plates. Additionally, the impedance amplitude of the ECS effectively monitors bearing damage propagation. Shear tests confirm that the integration method of the proposed ECS within the CFRP bolt introduces negligible intrusion to the host bolt's integrity. Experimental results demonstrate that the intelligent CFRP bolt can effectively monitor the damage propagation at the hole edge, with an accuracy for bearing damage exceeding 0.5 mm. At a working frequency of 10 MHz, the sensor's sensitivity in detecting a 0.5 mm bearing damage reaches 4.20%. An intelligent CFRP bolt was fabricated using the molding method. The embedding of the ECS did not cause adverse effects on the bolt. The proposed EC sensor is composed of carbon nanotube and epoxy resin adhesive films. The eddy current distribution at the hole edge of the CFRP bolted joints is analyzed. The ability of intelligent bolts to monitor hole edge damage is verified by experiments. [ABSTRACT FROM AUTHOR]

A displacement sensor with smaller volume and lower cost is needed for magnetic suspension control system. A transverse flux displacement sensor based on eddy current sensors is studied. The sensor analysis is based on its working principle. The parameters of excitation coil and induction coil are designed by particle swarm optimization, and the design process of the transverse flux sensor is simplified. The developed displacement sensor has a sensitivity of 7.2 V/mm, a linearity of 1.7%, and a detection range of ±0.5 mm. The sensor is applied in a magnetic levitation permanent magnet synchronous motor system. When the motor speed is 20 000 r/min, the high‑speed magnetic levitation rotor still maintains stable operation. The transverse flux displacement sensors developed in this paper can meet the requirements of magnetic suspension motor displacement detection and suspension control, and achieve the control effect of similar products. [ABSTRACT FROM AUTHOR]

Eddy current sensors are increasingly being used to measure the dynamic blade tip clearance in turbines due to their robust anti-interference capabilities and non-contact measurement advantages. However, the current research primarily focuses on enhancing the performance of eddy current sensors themselves, with few studies investigating the influence of turbine rotor parameters on the measurements taken by these sensors for dynamic blade tip clearance. Hence, this paper addresses this gap by using COMSOL Multiphysics 6.2 software to establish a finite model with circuit interfaces. Additionally, the model's validity was verified through experiments. This model is used to simulate the voltage output of the sensor and the measurement of dynamic blade tip clearance under various rotor parameters. The results indicate that the length and number of blades, as well as the hub radius, significantly affect the sensor voltage output in comparison to rotation speed. Furthermore, we show that traditional static calibration methods are inadequate for measuring dynamic blade tip clearance using eddy current sensors. Instead, it is demonstrated that incorporating rotor parameters into the calibration of eddy current sensors can enhance the accuracy of dynamic blade tip clearance measurements. [ABSTRACT FROM AUTHOR]

A new eddy current sensor with planar coils designed for noncontact distance measurement was applied in the inter electrode gap detection in the electrochemical machining (ECM). The sensor consists of two micro electroforming planar coils (driver coil and sensitive coil) stacked on the magnetic core. The magnetic model of the detection principle was built, and a new micro motion system was developed as a test and machining platform also. The size of the sensor was: Φ5 mm × 1.5 mm. The results show that the sensor is compact enough to nondestructively assess the electrode gap distance and could be easily integrated into a tool cathode for real-time electrolytic machining gap detection. [ABSTRACT FROM AUTHOR]

Bolt links and riveted joints, although widely used in aerospace and other mechanical systems, are susceptible to stress concentrations and fatigue cracks, which are undesirable. The flexible rosette eddy current sensor is typically used for the structural monitoring of bolt connections and riveted joints. This study proposes a method to improve the sensitivity of a flexible rosette eddy current sensor by reducing the cloud zenith angle of the pickup coil. First, the effect of the cloud zenith angle upon the sensitivity of the flexible rosette eddy current sensor is analyzed theoretically; the results show that a larger cloud zenith angle corresponds to a larger background signal. This diminishes the relative rate of change of the crack signal when the sensitivity of the sensor is evaluated based upon the maximum rate of change of the output. Therefore, the sensitivity is optimized by reducing the cloud zenith angle. Subsequently, through simulation and experimental methods, the relationship between sensor sensitivity and cloud zenith angle was studied. The results indicate that the cloud zenith angle significantly affects the sensitivity and that reducing the cloud zenith angle effectively reduces the background and improves the sensitivity. [ABSTRACT FROM AUTHOR]

The aim of this article is to determine a similar point to the Lift-Off intersection point (LOI) obtained from a geometric configuration of a Pulsed Eddy Current (PEC) sensor. This configuration enables easy determination of the LOI point through a single measurement, thus avoiding measurement noise. The sensor consists of an external excitation coil and two internal probes that overlap and have similar characteristics for reception. The similar point LOI is determined by the intersection of the signals from the transient response of the sensor's internal probes. Importantly, this point is independent of lift-off variation. Moreover, the amplitude and time measurement of this point vary with the variation of the physical and geometric properties of the sample. To assess the effectiveness of this similar point, a numerical code based on electromagnetic phenomena was developed. This code investigates the impact of thickness and electrical conductivity of metal sheets on the response of the PEC sensor, both with and without a ferrite core at this point. Additionally, a practical sensor prototype was constructed to validate the results obtained from the numerical model. The obtained results demonstrated a strong correlation between the numerical and experimental outcomes, thus confirming the effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]

It is shown that when performing surgical operations to remove foreign metal particles from the human body, it is advisable to use metal detectors of various types: flux-gate detectors for localizing ferromagnetic particles and eddy current detectors for localizing nonferromagnetic metal particles. The sensitivity of medical equipment must be sufficient to detect small ferromagnetic fragments and particles from a distance of at least 10 mm. The feasibility of preliminary magnetization of the search area with a strong permanent magnet is shown. Methods for setting up metal detectors are given. The need to minimize extraneous electromagnetic fields in the operating room is shown. [ABSTRACT FROM AUTHOR]

Conventional eddy-current sensors have the advantages of being contactless and having high bandwidth and high sensitivity. They are widely used in micro-displacement measurement, micro-angle measurement, and rotational speed measurement. However, they are based on the principle of impedance measurement, so the influence of temperature drift on sensor accuracy is difficult to overcome. A differential digital demodulation eddy current sensor system was designed to reduce the influence of temperature drift on the output accuracy of the eddy current sensor. The differential sensor probe was used to eliminate common-mode interference caused by temperature, and the differential analog carrier signal was digitized by a high-speed ADC. In the FPGA, the amplitude information is resolved using the double correlation demodulation method. The main sources of system errors were determined, and a test device was designed using a laser autocollimator. Tests were conducted to measure various aspects of sensor performance. Testing showed the following metrics for the differential digital demodulation eddy current sensor: nonlinearity 0.68% in the range of ±2.5 mm, resolution 760 nm, maximum bandwidth 25 kHz, and significant suppression in the temperature drift compared to analog demodulation methods. The tests show that the sensor has high precision, low temperature drift and great flexibility, and it can instead of conventional sensors in applications with large temperature variability. [ABSTRACT FROM AUTHOR]

Nowadays, 3D eddy current nondestructive characterization of crack and corrosion defects while using ECA remains an industrial challenge because the obtained image permits to determine only the 2D defect shape. Consequently, this article is devoted to determine directly the crack length and width by eddy current images through sensor array. Afterwards, we extract the maximal impedance amplitude to estimate the crack depth while using the deterministic algorithm that we have recently developed. In fact, the obtained results have demonstrated the effectiveness and the reliability of the proposed method. [ABSTRACT FROM AUTHOR]

End-point detection (EPD) is important for controlling the chemical mechanical polishing process to prevent underpolishing and overpolishing. One EPD method using the relative current density on a Cu wafer involves an eddy current, which has advantages of noncontact and a fast response speed. However, the eddy current method has a large mean error at a low relative current density. To overcome the disadvantage, composition signal filtration uses a high mean error and long delay time using a moving average and 1-D Kalman filtration. After applying composition filtration, the mean error improved by approximately 94.7 %. Still, it is difficult to measure a thickness of 4000 Å or less with existing systems. A digital potentiometer was developed that changed the resistance in real time and improved the detection range. The step number for changing the resistance was 120 steps in the resistance range of 100–5000 Ω at approximately 40 Ω/step. When a digital potentiometer was applied, the EPD detection range improved by 85.8 % over the existing system. In other words, the developed system could measure a Cu wafer thickness of 586 Å. [ABSTRACT FROM AUTHOR]

In the radial displacement measurement of a small-sized cylindrical target, coupling interference between eddy current sensors reduces the accuracy of the measurement. In this study, finite element method (FEM) simulation based on ANSYS Maxwell was adopted to investigate the relationships between the coupling coefficient of the sensors and different parameters including the lift-off, cylinder diameter, axis angle, material, and excitation frequency. The experimental results were consistent with the simulation results. The coupling interference between the sensors increased with the decrease in the lift-off and cylinder diameter. The coupling effect decreased significantly when the probe axis angle increased to 120°, and the decrease in the sensor sensitivity was acceptable. A polynomial fitting function fitted the output signal well. A compensation method was given based on the compensation necessity evaluation. The results showed that the error of the rotor motion track was significantly decreased after compensation. [ABSTRACT FROM AUTHOR]

Force plates have been widely used in various scientific fields to measure ground reaction forces experienced by animals and humans. A force plate that incorporates mechanical springs and non-contact displacement sensors offers the advantages of facilely modifying its shape and performance. However, the design protocol was limited to adjusting the plate size and spring constants of the springs supporting the plate at the four corners. Herein, we propose an optimization method for determining the spring constant distribution of a force plate. The proposed design enables the use of simulations to optimize the mechanical properties of the force plate, such as resonant frequency and error due to position. The experimental results demonstrated that the resonant frequency of the fabricated force plate was 133 Hz and the error due to position was within ±5 %. These results confirm that the proposed force plate can be effectively adjusted through optimization. [Display omitted] • Optimization method for spring constant distribution is proposed for a force plate. • The fabricated force plate realizes a resonant frequency of 133 Hz, error due to position within ±5%. • The ground reaction force measured by the fabricated force plate matches that of a commercially available force plate. [ABSTRACT FROM AUTHOR]

In this research, the design of non-destructive eddy current evaluation systems was improved using Harris Hawks optimization (HHO). To determine the orientation of cracks from eddy current data, a numerical approach was developed based finit elements methode FEM and on an iterative inversion technique that minimizes a non-linear least squares objective function that evaluates the overall difference between forecasts and observationsin axisymmetric model. In this paper the HHO optimization and steepest descent methods were compared and studied in order to minimize the objective function. To measure the precision of the estimated crack orientation, the lower bounds of the HHO optimization on crack orientation were obtained. This work explores the concept of an HHO algorithm that searches for the optimal solution within a large solution space for a specific crack orientation problem.The algorithm starts its search at any point in the solution space and looks for better solutions by searching in the "local" area surrounding the start point. The algorithm ends when it finds what it believes to be the best solution or when predetermined stopping criteria are met. • The damage (micro-cracks) is detected by NDT-EC using 2D-Axisymmetric FEM. • The effect of micro-crack orientation was studied using an eddy current test. • The proposed HHO algorithm is tested for crack-orientation detection. • The performance of HHO is also examined on several parametric problems. [ABSTRACT FROM AUTHOR]

Lift-off can cause significant errors in the measurement of metallic ball thickness using the eddy current method. In this paper, a triple-coil sensor, which is composed of two receiving coils and one excitation coil, is applied to address the problem of lift-off variation. There exists a peak frequency feature, which is the frequency where the peak value of the imaginary part of the inductance change occurs. The difference in peak frequencies of two receiving coils is linearly proportional to the thickness of the metal balls, with the advantage of reducing the effect of the lift-off during the measurements. The simulation results agree well with the experimental results and therefore a look-up table can be built for different thicknesses by simulation and the actual thickness can be found through comparing the measured results with the look-up table. This thickness measurement approach is effective and the error of the measurement is within 6.1% based on the experimental results. [ABSTRACT FROM AUTHOR]

The reliable classification of coin sets from different countries and counterfeit coins is an essential means of securing cash circulation. Especially bimetallic coins, such as 2-Euro coins, are often subjected to counterfeit by mixing them with coins of other countries or by imitations. In this article, a real-time embedded sensor system is proposed, based on inductance spectroscopy to characterize and identify bimetallic coins having similar geometric properties and looking similar at a first view. The system is based on inductance spectroscopy varying the penetration depth of the magnetic field in the bimetallic structure of the coin, which generally contains buried layers of other metals. The experimental evaluation shows that the bimetallic coins from different countries can be identified and classified by the use of the support vector machine, a machine learning algorithm. Experimental results showed that the system reached a classification accuracy up to 100% within a response rate of 36.62 ms per five bimetallic coins. [ABSTRACT FROM AUTHOR]

The study of 3D eddy current non destructive testing system for cracks characterization using finite element method requires a great amount of computing time and memory space. In this article, we have validated the developed model and then determined directly the crack length by analyzing the complete signal. Afterwards, we have extracted from the complete sensor sweep signal the maximal amplitude that we have exploited to estimate the crack depth. [ABSTRACT FROM AUTHOR]

This paper presents the design and development of a novel, linear, eddy current-based noncontact angle sensor with 360° range. Although the eddy current proximity sensors are known for high reliability, resolution, and insensitivity to moisture and oil, the approach has not been exploited to develop full-circle range angle sensors with such features. The proposed sensor consists of a rotary conducive hollow tube (e.g., made of aluminum) part and a stationary part with four identical flexible coils. The tube has a simple but special groove. The position of the groove modifies the value of the inductance of the stationary coil as a function of the sensing angle. The design is such that the inductance of each coil varies linearly for a specified range of the angle. From this piecewise linear characteristic, an output that is linear for the full-circle range is obtained using a simple yet effective algorithm. A suitable signal conditioning circuit is developed to obtain an output that is proportional to the change in the inductance of the coil. In order to optimize the design, first, the sensor structure was studied using finite-element analysis. Then, a prototype of the sensor was built and tested in the laboratory. The prototype sensor has a resolution of 0.08° and a maximum nonlinearity of 0.25%. The possible sources of error of the sensor have been analyzed and quantified. The sensor has no electrical contact to the rotary part and its output is immune to moisture, dust, and oil. [ABSTRACT FROM AUTHOR]

This paper presents an axial flux eddy current sensor with a compact and simple structure for measuring the rotating speed of iron shafts. The sensor structure is optimized for high sensitivity with a novel configuration of the coils positioned perpendicularly to each other. The sensor comprises two D-shaped excitation coils and two D-shaped pick-up coils in a double-layer structure. A disc-shaped magnetic shield or core shields the coils. Two iron shafts with different material properties are considered. A new cup-shaped configuration of nonmagnetic copper and aluminum caps mounted on iron shafts improves sensitivity and suppresses susceptibility to shaft material properties and airgap variation. 2D and 3D finite element methods are utilized for the performance analysis of the sensor. The measurements are performed at speeds up to ± 3000 rpm and different excitation frequencies from 400 Hz to 4 kHz. The eddy current speed sensor has excellent linearity characteristics with a nonlinearity error of 0.15%. The geometry of the coils is further optimized and improved for maximum sensitivity and compactness. The fault-tolerant capability of the sensor is also evaluated. [Display omitted] • Axial flux eddy current speed sensor for rotating speed measurement. • Novel configuration of perpendicular coils. • Optimization of the eddy current speed sensor. • 2D and 3D finite element method analysis. [ABSTRACT FROM AUTHOR]

With the wide application of the high-speed electrical machine with the active magnetic bearings (AMBs), improving the dynamic response and the resolution of the displacement sensor for AMBs becomes an actual challenge for industrial development. This paper proposes a self-differential eddy current displacement sensor (ECDS) for radial AMBs system. The phase advance network method was utilized to improve the dynamic characteristic for the sensor based on the equivalent transfer function model. The reason of the sensor-to-sensor crosstalk was analyzed in detail to provide a theoretical basis for improving the resolution of the sensor. First, the operating principle of the ECDS was analyzed in detail. Second, the miniaturization design was presented: the two symmetrical probe coils were used as the working inductors in the Hartley oscillation circuit to form a self-differential structure to simplify the measuring circuit observably, and suppress the common mode interference. Third, the dynamic characteristic of the sensor and the sensor-to-sensor crosstalk was described and compensated. Finally, a series of experiments was carried out to test the sensor performance. The experimental results showed that the ECDS with the features of the minimum circuit, the wide bandwidth, and the high resolution can greatly improve the controllability of the AMBs system. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to investigate the process of rapid prototyping eddy current sensors using 3D printing technology. Making full use of the advantages of 3D printing, the authors study on a new method for fabrication of an eddy current sensor.Design/methodology/approach In this paper, the authors establish a 3D model using SolidWorks. And the eddy current sensor is printed by the fused deposition modeling method.Findings Measurement results show that the 3D printing eddy current sensor has a wider linear measurement range and better linearity than the traditional manufacturing sensor. Compared to traditional eddy current sensor fabrication method, this 3D printed sensor can be fabricated at a lower cost, and the fabrication process is more convenient and faster.Practical implications This demonstrated 3D printing process can be applied to the 3D printing of sensors of more sophisticated structures that are difficult to fabricate using conventional techniques.Originality/value In this work, the process of rapid prototyping eddy current sensors using 3D printing is presented. Sensors fabricated with the 3D printing possess lots of merits than traditional manufactures. 3D printed sensors can be customized according to the configuration of the overall system, thus reducing the demand of sensor's rigid mounting interfaces. The 3D printing also reduce design costs as well as shortens the development cycle. This allows for quick translation of a design from concept to a useful device. [ABSTRACT FROM AUTHOR]

Forced structural vibration and cutting tool inaccuracy have been identified to be the primary causes of surface defects in rotary wood planing. This paper presents the development of a control strategy used to compensate for the effects of both vibration and cutting tool inaccuracy on planed wood surface finish. The solution is based on active vibration control and real-time modification of the cutting tool trajectory using an optimal Linear Quadratic Gaussian tracking controller. A small-scale mechatronic wood planing machine, which has an actively controlled spindle unit, has been designed for practical investigation of the proposed technique. Experimental results show that the applied compensation increased the dynamic performance of the machine and the quality of the surface finish produced. [ABSTRACT FROM AUTHOR]

Manufacturing a high-pressure sensitive diaphragm type sensor is a complex task. Due to it's complex shape, several parts are designed individually. It involves welding of several parts. As welding involves several parameters it's difficult to control the welding geometry where it is being fused. So it is likely that the physical boundary condition of the welded region will be different from the theoretical boundary conditions. So the change in boundary condition will make the deflection of the diaphragm different. For a precision device, any effect of a change in boundary condition can affect the deflection of the diaphragm largely. Thus, any effect of imperfect welding in a high precision measuring device can hamper the sensitivity of the particular device. A welded diaphragm of steel for a pressure sensor using eddy current sensor to detect it's deflection due to pressure can lose it's effectivity, due to the unpredictable boundary conditions created after the welding. In this paper, we will be trying to find the cause of deviation between the theoretical and experimental results due to the effect of a change in boundary conditions at the welded region. [ABSTRACT FROM AUTHOR]

Purpose Magnetic permeability variations of ferromagnetic materials under elastic stress offer the potential to monitor tension based on the inverse magnetostrictive effect. The purpose of this paper is to propose an innovative self-inductance tension eddy current sensor to detect tension.Design/methodology/approach The effectiveness of conventional elasto-magnetic (EM) sensor is limited during signal detection, due to its complex sensor structure, which includes excitation and induction coils. In this paper, a novel self-inductance tension eddy current sensor using a single coil is presented.Findings The output signal was analyzed through oscilloscope in the frequency domain and via self-developed data logger in the time domain. Experimental results show the existence of a linear relationship between voltage across the sensor and tension. The sensor sensitivity is dependent on operating conditions, such as current and frequency of the input signal.Practical implications The self-inductance sensor has great potential for replacing conventional EM sensor due to its low cost, simple structure, high precision and good repeatability in tension detection.Originality/value A spilt sleeve structure provides a higher permeability path to magnetic field lines than a non-sleeve structure, thus reducing the loss of magnetic field. The self-developed data logger improves sensitivity and signal-to-noise ratio of sensor. The novel sensor, as a replacement of the EM sensor, can easily and accurately monitor the tension force. [ABSTRACT FROM AUTHOR]

The thickness of anti-corrosive layer coated in the inner surface of steel oil containers is very important to prevent the containers from corrosion. To make the measurement accurate, some effective means are needed, especially for the eddy current sensor inclining or deviating over the curved inner surface of the containers. By using an electromagnetic field simulation method with high accuracy, the distorted signals and the measure precision of lift-off were analyzed. Then, some correction measures were proposed according to the characteristics of testing signals due to the sensor's inclination or deviation. Simulation results confirmed their effectiveness for enhancing the measure precision. The conclusions can give an effective theoretical guide to the centering and verticality controlling of the sensor in practice. [ABSTRACT FROM AUTHOR]

In Japan, deteriorated water pipes are increasing more and more now. Therefore, the setting of the priority to update these pipes effectively is required. As a solution of this problem, we proposed a new sensor using the principle of SLOFEC [1] and the structure of a focusing eddy current sensor [2]. In this paper, we verify the performances of the proposed sensor by 3D-FEM analysis. The effectiveness of the proposed sensor is also verified through measurements on a prototype. [ABSTRACT FROM AUTHOR]

The present paper investigates monitoring of fatigue cracks of a metal structure using an eddy current micro sensor. Fatigue cracks tend to occur at bolt-jointed structures on an aircraft. In order to detect the damage quantitatively, a kind of change-prone micro eddy current sensor is designed and fabricated with flexible printed circuit board (FPCB) technology. A forward semi-analytical model is built by extracting a material's conductivity as the damage feature parameter, and characteristics analysis is conducted based on the model. The research focuses on setting up and utilizing the eddy current fields to analyze interaction of adjoining coils when the damage occurs, and investigating optimization on the working parameters of the sensor. In the experimental section, several common connection structures are applied to explore the sensor's monitoring ability both in air and in a corrosive environment. The result shows that the optimal working frequency is about 1 MHz. The eddy current micro sensor is capable of monitoring the crack growth with an accuracy of 1 mm, the average error being 4.6 % compared to fracture analysis. The sensor keeps high resolution of damage in aqueous corrosion. Due to the fretting fatigue, wear appears on the polyimide foil, leading to the decreases of the monitoring signal. [ABSTRACT FROM AUTHOR]

Disc cutter is the main rock breaking tool of TBM. It is angled worn frequently because of locked-rotor; as a result, monitoring relevant operating parameters of TBM disc cutter has become an urgent technical problem. This paper studies nondestructive and non-contact online detection disc cutter rotational speed method of based on eddy current sensor: applies eddy current sensor to detecting six 2 mm-high metal bumps setting on the disc cutter, so as to detect the rotational speed of disc cutter. K60 MCU is applied as the main control core. The experimental results show that the on-line rotational speed monitor system of disc cutter features high anti-jamming ability and is reliable. [ABSTRACT FROM AUTHOR]

Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances. [ABSTRACT FROM AUTHOR]

The precise localisation of rail vehicles is fundamental to the development and employment of more efficient train control systems in security, logistics and disposition applications. A key element of this is the exact and reliable velocity and distance estimation. The popular satellite navigation (global navigation satellite systems) and visual odometry, based on optical systems, tend to fail in the rough environment of rail application scenarios. This study describes an approach to making a precise distance estimate using an innovative eddy current sensor system. This is achieved through the combination of an augmented cross‐correlation approach to highly accurate velocity estimation. That is subsequently employed to determine the travelled distance based on counting rail clamps in a spatial transformed space. This approach relies on recursive state estimation of the dynamic states and a statistical assessment of the counted rail clamps for the purpose of outlier rejection. The proposed methods are compared and evaluated in a quantitative way on the basis of experimental data. The results prove that the proposed approach can improve the accuracy and reliability of velocity measurement and relative position detection. [ABSTRACT FROM AUTHOR]

Aiming at the vibration on the drive shaft side of wax oil hydrogenation turbine was too large to run normally when the steam turbine was in commissioning process in a refinery project and the shaft electrical run-out was also too large. The vibration spectrum and axis orbit of the turbine shaft were analyzed, and the shaft magnetism was test by using pin to approach rotor slowly, the pin was attracted, it was indicate that the rotor was magnetized. The principle of eddy current sensor, the eddy current sensor signal were influenced by the magnetic flux, and the relationship between eddy current sensor and the measured metal body were further investigated by magnetoresistance effect theory, then the experimental model was established and simulated, and combined with engineering applications. The result indicates that the magnetic flux of rotor is over ANSI/API Std 612 standers and the vibration interference is influenced by the excessive magnetic flux of rotor through theory analysis and experiment test. Then adopting degaussing and rolling countermeasures and solving this problem, it is reference for other similar problems. [ABSTRACT FROM AUTHOR]

Aiming at the Petrochemical Industries Co GB201 compressor unit, the shaft displacement and shaft vibration signal of the turbine side appeared mutation phenomenon, the grounding brush for steam turbine, the BENTLY 3500 grounding system and the static electricity causes were researched. The unit could not be stopped, only to analyse related factors which could lead to malfunction. Exclude factors could be excluded, the steam turbine grounding brush was inspected and replaced on-line, the BENTLY 3500 grounding system was inspected and the influence of rotor electric or magnetic was analysised. Finally, it was determined that the static electricity from the lube oil by high speed rotor and bearing extrusion friction, and the bearing house was too larger to the joint of the TSI probe in the bearing house, the joint was soaked in the lube oil which temperature is 50° for a long time, the insulation may become worse, the electrostatic was accumulated to the joint, resulted electric charge accumulation and mutation phenomenon.After the unit was overhaul, the bearing house was opend and inspected, the prode joints were isolated afresh, when the unit was running again it was back to normal. The results indicate that the signal mutation is because of the static electricity from the lube oil by high speed rotor and bearing extrusion friction and the insulation of the TSI probe's joint is failure. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents a new complete approach for Tool Condition Monitoring (TCM) in milling. The aim is the early detection of small damages so that catastrophic tool failures are prevented. A versatile in-process monitoring system is introduced for reliability concerns. The tool condition is determined by estimates of the radial eccentricity of the teeth. An adequate criterion is proposed combining mechanical model of milling and angular approach. Then, a new solution is proposed for the estimate of cutting force using eddy current sensors implemented close to spindle nose. Signals are analysed in the angular domain, notably by synchronous averaging technique. Phase shifts induced by changes of machining direction are compensated. Results are compared with cutting forces measured with a dynamometer table. The proposed method is implemented in an industrial case of pocket machining operation. One of the cutting edges has been slightly damaged during the machining, as shown by a direct measurement of the tool. A control chart is established with the estimates of cutter eccentricity obtained during the machining from the eddy current sensors signals. Efficiency and reliability of the method is demonstrated by a successful detection of the damage. [Copyright &y& Elsevier]

Abstract: Measurement of nano-scale copper film thickness is of great importance in the semiconductor industry. The eddy current method is used for the purpose due to its non-destructive and fast dynamic response features. In this paper, an equivalent circuit model is used to get the relationship between the measurement sensitivity and sensor parameters. It is found that the internal resistance of an eddy current sensor plays a primary role in the improvement of the measurement sensitivity beside of the Q factor of the sensor. A simple experimental setup is established and a series of Cu films with the thicknesses ranging from 20nm to 350nm are prepared as test samples. Test results indicate that the sensitivity of an optimized sensor made of a lower resistant multi-wire Cu line has better sensitivity than that wound with a higher resistant single Cu wire under large lift-off. [Copyright &y& Elsevier]

In order to make an effective on-line thickness measurement of thick coating in hemispherical steel shells, a strategy using combined laser and eddy current (EC) sensors based on displacement differential method was proposed. To enhance the measuring precision, an EC displacement sensor with large test range was adopted and the effect of shell curvature on its output was reduced by applying the polynomial curve fitting. Its feasibility was verified by experimental results. [ABSTRACT FROM AUTHOR]

The anti-corrosive coating in pipeline and oil tanker is taken as a crucial component in petroleum industry and needs a robust NDE tool to evaluate its thickness. For the thick coating on the curved steel bases of various sizes, the eddy current sensor's evaluation capability for thick coating and the influence of the test-piece sizes on the evaluation precision are two key problems had to be solved. Taking into account the dimension effect of the sensor on signals, a wide-range sensor was designed and applied to the coating evaluation. The relationship between coil responses and liftoff was investigated and a NDE strategy based on a polynomial coefficient database was proposed to cope with the influence of test-piece sizes. Its applicability was verified by simulation results. [ABSTRACT FROM AUTHOR]

Abstract: Analytical solutions for the inductance can be easily obtained for coils with rectangular cross sections having multiple turns realizing a homogeneous current distribution. These models have at least six parameters and do not consider the self-capacitance of the coil. The inner magnetic field is partially included, so that the accuracy of the static impedance is limited especially at higher frequencies. Even at lower frequencies, reference measurements without target are generally needed for self-calibration. By direct evaluation of the magnetic vector potential at the contour of the coil wire, a coil inductance model with a simpler mathematical structure can be obtained, which allows a consideration of the self-capacitance and the inner inductance. This avoids the need for reference measurements and the influence of distance, conductivity and permeability can be easier quantified. Inductance calculation requires 250ms on a standard personal computer for 100 frequencies resulting in a deviation of at most 5% for the static inductance. This is a good result with respect to the low impedances in the μΩ range, which are generally hard to measure. The proposed model represents a good basis for models of multiple turns with a precisely defined geometry including the self-capacitance effects. [Copyright &y& Elsevier]

Abstract: The 500MWe sodium cooled prototype fast breeder reactor (PFBR) presently under advanced stage of construction has two diverse and independent shut-down systems. Each shutdown system comprises of independent sensing systems, control logic and drive mechanisms. The drive mechanism belonging to the first shutdown system is used for controlling reactor power and also for shutting down the reactor. It is known as control and safety drive rod mechanism (CSRDM). The mechanism belonging to the second shutdown system is used only for shutting down the reactor and is called diverse safety rod drive mechanism (DSRDM). CSRDM has potentiometer which is used to determine the position of the control and safety rod (CSR). The free fall time of control and safety rod can also be measured with the help of the potentiometer. Constraint of putting similar type of instrument in DSRDM has prohibited position detection of DSR as well as measurement of free fall time of diverse safety rod (DSR). However center has embarked on development of three different techniques to detect the position and free fall time of DSR. These techniques are Kalman filtering technique using neutronic signal to detect position of DSR, measurement of acoustic signal which is produced when DSR hits the dashpot and the eddy current based technique. Description of development of eddy current based sensor to detect position and free fall time of DSR is the main aim of this paper. The sensor consists of five coils which are inductively coupled. The change in position of DSR causes change in inductance of the coil and hence voltage induced in the coil. The measurement of coil voltage reveals the position of the DSR. Sodium testing of the sensor has been carried out on a 1:1 model of the sensor. The performance of the sensor at various temperatures and frequencies has been studied and found satisfactory. The sodium testing has shown encouraging results and have proven the feasibility of using such a sensor for the reactor application. The piston of the DSR is made of modified 9Cr–1Mo magnetic steel. A sensor winding is placed around the dashpot, the inductance of the winding changes when the DSR is deposited in the dashpot. Transformer coupling between two windings is then used to measure the inductance change of the sensor winding to facilitate non-contact measurement. The winding configuration has been chosen such that the signal can be picked-up even when there is misalignment between the coils due to thermal and radiation induced dimensional changes. [Copyright &y& Elsevier]

In order to provide a contactless measurement technique to examine products during the fabrication process, a modular design of an eddy current micro sensor was developed and fabricated in thin-film technology. The sensor consists of two parts, a single-turn excitation coil and an anisotropic magneto-resistance (AMR) sensor. The AMR sensor detects the change of the magnetic field induced in a sample by the excitation coil. Initial investigations were conducted to prove the capability of the completed eddy current micro sensor. A defect was created on the surface of a Cu probe. The electrical output signal of the AMR sensor was subsequently compared to optical measurements of the surface profile of the crack. There is a high correlation between the optical measurements and to those of the eddy current micro sensor. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new method for measuring 3D rotation angle of spherical joint is proposed. • The method is based on 3D spherical encoding and eddy current sensors. • The structure of the measurement system is optimized through experiments. • The mean squared error of the measurement system is approximately 25′. A new method for measuring 3D rotation angle of precision spherical joint based on eddy current sensors is proposed in this study. A pseudorandom code is used to generate a 2D plane absolute code and then mapped to the sphere. The 3D absolute code is formed on the ball head through precision cutting, and an eddy current sensor array is arranged in the ball socket to identify the code. The experimental tests were conducted on the parameter-optimized prototype, and the experimental results showed that the mean squared error of the 3D rotation angle measurement was approximately 25′ in the range. The proposed new measurement principle provides a new approach to the precision measurement of spherical rotary motion, which is expected to produce a breakthrough in the theory and technology of spherical-angle sensor measurement. The proposed new principle also provides a theoretical basis and technical experience for the integration and development of intelligent devices. [ABSTRACT FROM AUTHOR]

A suitable framework for the development of artificial neural networks is important because it decides the level of accuracy, which can be reached for a certain dataset and increases the certainty about the reached classification results. In this paper, we conduct a comparative study for the performance of four frameworks, Keras with TensorFlow, Pytorch, TensorFlow, and Cognitive Toolkit (CNTK), for the elaboration of neural networks. The number of neurons in the hidden layer of the neural networks is varied from 8 to 64 to understand its effect on the performance metrics of the frameworks. A test dataset is synthesized using an analytical model and real measured impedance spectra by an eddy current sensor coil on EUR 2 and TRY 1 coins. The dataset has been extended by using a novel method based on interpolation technique to create datasets with different difficulty levels to replicate the scenario with a good imitation of EUR 2 coins and to investigate the limit of the prediction accuracy. It was observed that the compared frameworks have high accuracy performance for a lower level of difficulty in the dataset. As the difficulty in the dataset is raised, there was a drop in the accuracy of CNTK and Keras with TensorFlow depending upon the number of neurons in the hidden layers. It was observed that CNTK has the overall worst accuracy performance with an increase in the difficulty level of the datasets. Therefore, the major comparison was confined to Pytorch and TensorFlow. It was observed for Pytorch and TensorFlow with 32 and 64 neurons in hidden layers that there is a minor drop in the accuracy with an increase in the difficulty level of the dataset and was above 90% until both the coins were 80% closer to each other in terms of electrical and magnetic properties. However, Pytorch with 32 neurons in the hidden layer has a reduction in model size by 70% and 16.3% and predicts the class, 73.6% and 15.6% faster in comparison to TensorFlow and Pytorch with 64 neurons. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new flexible eddy current sensor array and its measurement system that used for conformable proximity sensing, for instance, the gap between curved surfaces. The sensor probe, designed to consist of a forked coils array and a long flat cable, is manufactured on a thin flexible substrate by the flexible printed circuit board (FPCB) technology. The probe is very thin and flexible, so that it can conform to the surface geometries of the measured objects. Time division multiplexing (TDM) technology has been introduced to scan and sample all the sensing elements. Some reforms are also implemented to the conventional LC oscillator to solve the problem of the coils having a low Q-factor. Experimental results show that, to a steel target, the measurement accuracy of the sensor system can reach ±0.5% for a 2mm full scale. The practice for real-time inspection of the small gaps between large curved surfaces is also considered. [Copyright &y& Elsevier]

Abstract: Today the knowledge of a process is very important for engineers to find optimal combination of control parameters warranting productivity, quality and functioning without defects and failures. In our laboratory, we carry out research in the field of high speed machining with modelling, simulation and experimental approaches. The aim of our investigation is to develop a software allowing the cutting conditions optimisation to limit the number of predictive tests, and the process monitoring to prevent any trouble during machining operations. This software is based on models and experimental data sets which constitute the knowledge of the process. In this paper, we deal with the problem of vibrations occurring during a machining operation. These vibrations may cause some failures and defects to the process, like workpiece surface alteration and rapid tool wear. To measure on line the tool micro-movements, we equipped a lathe with a specific instrumentation using eddy current sensors. Obtained signals were correlated with surface finish and a signal processing algorithm was used to determine if a test is stable or unstable. Then, a fuzzy classification method was proposed to classify the tests in a space defined by the width of cut and the cutting speed. Finally, it was shown that the fuzzy classification takes into account of the measurements incertitude to compute the stability limit or stability lobes of the process. [Copyright &y& Elsevier]

Abstract: Increasing demands on re-enforced concrete constructions (e.g. bridges) require long-term multi-sensor monitoring techniques. For failure prediction of components the continuous monitoring of force and stress in reinforced concrete components is required. Coils can detect very small stress variations in ferromagnetic steels due to the magneto-elastic effect. Their main advantage over strain gauges is the ability of a medium-free measurement. Environmental and real construction conditions led to a sensor arrangement with six individual eddy current coils. These coils were arranged around a strand wire and are also in direct contact with the material under testing. Due to changing magnetostriction coefficients of different structural steels an impedance calibration is necessary [D. Jiles, Introduction to Magnetism and Magnetic Materials, Chapman and Hall, London, 1991]. [Copyright &y& Elsevier]

[Display omitted] • The feasibility of eddy current sensors for underwater acoustic signal measurement is analyzed. • A theoretical model is proposed to calculate the transduction constants of the eddy current sensors. • The influence of the axial offset of eddy current sensors on the transduction constant is analyzed. This paper provides insights into the principle of eddy current sensors applied to displacement-based vector hydrophones by both theoretical and experimental analyses. These displacement-based vector hydrophones provide excellent performances at the Ultra-Low Frequency. First, theoretical calculations are presented to demonstrate the feasibility of the eddy current sensors for measurements of underwater acoustic signals. Theoretical models are then established to calculate the transduction constants of eddy current sensors with the flat, spherical, and cylindrical conductive materials, respectively. The influence of the axial offset of eddy current sensors on the transduction constant is analyzed by finite element models lastly. The theoretical models are further validated by comparison with experimental results. The experiment results show that, when the radii of the spherical and cylindrical conductive materials are greater than eight times the coil radius, the spherical and cylindrical conductive materials are equivalent to the flat conductive material. Moreover, the axial tolerable offset between the conductive material and the coil is proportional to the radius of the spherical or cylindrical conductive material. [ABSTRACT FROM AUTHOR]

• The peak frequency is linear to the lift-offs between the centre of coil and ball. • The slope of peak frequencies versus lift-offs is linked to the radius of ball. • The radius of the metallic ball can be deduced by using the measured slope. • The radius of the metallic ball is retrieved with an error of less than 2%. This paper proposes a linear eddy-current feature to determine the radius of a metallic ball in a non-contact manner. An electromagnetic eddy-current sensor with two coils is placed co-axially to the metal ball during measurement. It is well known that the distance between the sensor and test piece (i.e. lift-off) affects eddy-current signals. In this paper, it is found that the peak frequency feature of inductance spectrum is linear to the lift-off spacing between the centre of coil and ball. Besides, the slope of peak frequencies versus lift-offs is linked to the radius of ball. The radius of metallic balls is retrieved from the experimental and embedded analytical result of the slope. Measurements have been carried out on 6 metallic balls with different radii. The radius of the metallic ball can be retrieved with an error of less than 2%. [ABSTRACT FROM AUTHOR]

The relevance of the eddy current sensing technique to monitor the ageing state of electronic power modules has been experimentally studied. To do so, a commercial eddy current sensor was implemented for the evaluation of COOLMOSTM transistor chips soldered on a direct copper bonded ceramic substrate of a power module. The measurement data obtained over a large frequency bandwidth were analysed in the normalised complex impedance plane. The analysis shows that the sensor enables the chip and the substrate to be separately sensed. Furthermore, the ageing state of artificially aged chips can be clearly monitored. These preliminary results allow the design of eddy current micro‐sensors dedicated to power module in‐service monitoring purposes to be envisaged. [ABSTRACT FROM AUTHOR]