scholarly journals Inversion of Distance and Magnetic Permeability Based on Material-Independent and Lift-off Insensitive Algorithms Using Eddy Current Sensor

2020 ◽  
Author(s):  
Mingyang Lu ◽  
Xiaobai Meng ◽  
Ruochen Huang ◽  
Liming Chen ◽  
Anthony Peyton ◽  
...  
Keyword(s):  
Eddy Current ◽  
Magnetic Permeability ◽  
Skin Effect ◽  
Maximum Error ◽  
Current Sensor ◽  
Dual Frequency ◽  
Eddy Current Sensor ◽  
Thin Skin ◽  
Lift Off ◽  
Effect Experiment

Eddy current sensors can be used to test the characteristics and measure the parameters of the conductive samples. As the main obstacle of the multi-frequency eddy current sensor, the lift-off distance affects the effectiveness and accuracy of the measurement. In this paper, a material-independent algorithm has been proposed for the restoration of the lift-off distance when using the multi-frequency eddy current sensor, which is based on the approximation under the thin-skin effect. Experiment testing on the performance of the proposed method is presented. Results show that from the dual-frequency inductance, the lift-off distance could be restored with a maximum error of 0.24 mm for the distance up to 12 mm. Besides, the derived lift-off distance is used for the inversion of the magnetic permeability. Based on a lift-off insensitive inductance (LII) feature, the magnetic permeability of steels can be inversed in an iterative manner, with an error of less than 0.6 % for the lift-off distance up to 12 mm.

Study on extraction of electrical runout in eddy current measurement using finite element method

2013 ◽  
Vol 228 (6) ◽  
pp. 1077-1086 ◽  
Author(s):  
Xiaolong Chen ◽  
Yanlong Cao ◽  
Zaiyu Lin ◽  
Jiangxin Yang ◽  
Xiaoqi Hu
Keyword(s):  
Finite Element ◽  
Relative Permeability ◽  
Imaginary Part ◽  
Eddy Current ◽  
Material Properties ◽  
Ferromagnetic Material ◽  
Current Sensor ◽  
The Real ◽  
Eddy Current Sensor ◽  
Lift Off

Electrical runout is a bottleneck problem of eddy current sensor, which is caused by the maldistribution/variation of material electromagnetic properties of measurement target. However, extraction methods of electrical runout in eddy current displacement measurement remain ambiguous. Here, a 2D finite element model for the influence analysis of conductivity and permeability of ferromagnetic material on coil impedance of eddy current sensor is reported, which will be beneficial for detecting material properties and guiding manufacturing process. The relationships between the real and imaginary part of coil impedance with the varied material conductivity, relative permeability and the lift-off, which indicates the detecting distance, are investigated. When the conductivity, relative permeability of ferromagnetic material and the lift-off vary within a certain range, the relationships between the real and imaginary part of coil impedance are all nearly linear. This paper further shows that the character of distribution of resistance and reactance in diagram under different material properties and same measuring distance is linear. Furthermore, these lines under different measuring distances are parallel. Also the character under different measuring distances and same material property is linear, but these lines under different material properties are diffuse with same intercept. Altogether, the study shows that this method based on redesign of signal processing and its circuit is feasible and instructive in separating electrical runout from the output of eddy current sensor.

An Investigation of Eddy-Current Effects on Parameter Monitoring for Duplex Lathe Machining of Thin-Wall Components

2014 ◽  
Author(s):  
Kok-Meng Lee ◽  
Min Li ◽  
Kun Bai
Keyword(s):  
Eddy Current ◽  
Magnetic Sensors ◽  
Design Parameters ◽  
Current Sensor ◽  
Magnetic Flux Density ◽  
Thin Wall ◽  
Dual Frequency ◽  
Current Sensing ◽  
Sensing System ◽  
Eddy Current Sensor

This paper presents a novel design of an eddy-current sensing system with an array of high-accuracy solid magnetic sensors for duplex lathe machining of thin-wall compressor disks. By controlling the penetration depth of the eddy current, the dual-frequency sensing system based on measured magnetic flux density simultaneously measures the in-feed cutting depth and workpiece thickness in real-time. Specifically, this paper provides the design concept and operational principle of the eddy-current sensing system along with the theory for designing the sensor and analyzing its performance. As eddy current cannot be measured directly, results of a numerical investigation based on finite-element analyses are presented with illustrative examples offering new physical insights into the effects of optimal design parameters on the magnetic and electric field distributions of the induced eddy-current. The effectiveness of a dual-frequency eddy-current sensor has been numerically evaluated and compared against experimental data of a commercial eddy-current sensor operated at 1MHz.

scholarly journals Lift-off tolerant pancake eddy-current sensor for the thickness and spacing measurement of non- magnetic plates

2020 ◽  
Author(s):  
Mingyang Lu ◽  
Xiaobai Meng ◽  
Ruochen Huang ◽  
Liming Chen ◽  
anthony peyton ◽  
...  
Keyword(s):  
Eddy Current ◽  
Test Piece ◽  
Triple Helix ◽  
Outer Radius ◽  
Small Error ◽  
Current Sensor ◽  
Magnetic Vector Potential ◽  
Eddy Current Sensor ◽  
Spacing Distance ◽  
Lift Off

<p>The lift-off spacing distance between the eddy current sensor and test piece will influence the detected signals and accuracy of the measurement. <a>Various techniques including novel sensor designs, features (lift-off point of intersection, lift-off invariance phenomenon), and algorithms have been proposed for the compensation of error caused by the lift-off effect using the eddy current sensor. However, few of these have directly measured the lift-off spacing distance, particularly for the distance up to 15 mm. </a>In this paper, a lift-off tolerant pancake sensor has been designed. By analysing the sensitive region of the magnetic vector potential change (due to the test piece), the receiver of the sensor is designed as a circular spiral pancake coil with a large mean radius and span length (the difference between inner and outer radius). Experiments on the inductance measurement of three different non-magnetic samples have been carried out using both the designed pancake sensor and the previous triple-helix sensor. From the experiment result, the detected signal of the designed sensor has been proved much larger than that of the triple-helix sensor. Besides, simplified algorithms have been proposed for the measurement of the lift-off spacing and thickness of non-magnetic samples when using the proposed pancake sensor. Results show that the lift-off spacing and thickness can be measured with a small error of 0.14 mm (absolute error under 209.66 kHz), and 1.35 % (relative error, under low working frequencies of 142, 238, and 338 Hz) for the lift-off spacing from 1 to 15 mm.</p>

scholarly journals Analysis of Tilt Effect on Notch Depth Profiling Using Thin-Skin Regime of Driver-Pickup Eddy-Current Sensor

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5536
Author(s):  
Mingyang Lu ◽  
Xiaobai Meng ◽  
Ruochen Huang ◽  
Anthony Peyton ◽  
Wuliang Yin
Keyword(s):  
Eddy Current ◽  
Tilt Angle ◽  
Depth Profiling ◽  
Current Sensor ◽  
Notch Depth ◽  
Measured Voltage ◽  
Eddy Current Sensor ◽  
Thin Skin ◽  
Different Depths ◽  
Current Sensors

Electromagnetic eddy current sensors are commonly used to identify and quantify the surface notches of metals. However, the unintentional tilt of eddy current sensors affects results of size profiling, particularly for the depth profiling. In this paper, based on the eddy current thin-skin regime, a revised algorithm has been proposed for the analytical voltage or impedance of a tilted driver–pickup eddy current sensor scanning across a long ideal notch. Considering the resolution of the measurement, the bespoke driver–pickup, also termed as transmitter–receiver (T-R) sensor is designed with a small mean radius of 1 mm. In addition, the T-R sensor is connected to the electromagnetic instrument and controlled by a scanning stage with high spatial travel resolution, with a limit of 0.2 μm and selected as 0.25 mm. Experiments were conducted for imaging of an aluminium sheet with seven machined long notches of different depths using T-R sensor under different tilt angles. By fitting the measured voltage (both real and imaginary part) with proposed analytical algorithms, the depth profiling of notches is less affected by the tilt angle of sensors. From the results, the depth of notches can be retrieved within a deviation of 10% for tilt angles up to 60 degrees.

scholarly journals Model of Magnetically Shielded Ferrite-Cored Eddy Current Sensor

Sensors ◽  
2022 ◽  
Vol 22 (1) ◽  
pp. 326
Author(s):  
Darko Vasić ◽  
Ivan Rep ◽  
Dorijan Špikić ◽  
Matija Kekelj
Keyword(s):  
Eddy Current ◽  
Impedance Measurement ◽  
Magnetic Potential ◽  
Current Sensor ◽  
Ferrite Core ◽  
Resistance Change ◽  
Eddy Current Sensor ◽  
Transmitter Coil ◽  
Electromagnetic Models ◽  
Lift Off

Computationally fast electromagnetic models of eddy current sensors are required in model-based measurements, machine interpretation approaches or in the sensor design phase. If a sensor geometry allows it, the analytical approach to the modeling has significant advantages in comparison to numerical methods, most notably less demanding implementation and faster computation. In this paper, we studied an eddy current sensor consisting of a transmitter coil with a finitely long I ferrite core, which was screened with a finitely thick magnetic shield. The sensor was placed above a conductive and magnetic half-layer. We used vector magnetic potential formulation of the problem with a truncated region eigenfunction expansion, and obtained expressions for the transmitter coil impedance and magnetic potential in all subdomains. The modeling results are in excellent agreement with the results using the finite element method. The model was also compared with the impedance measurement in the frequency range from 5 kHz to 100 kHz and the agreement is within 3% for the resistance change due to the presence of the half-layer and 1% for the inductance change. The presented model can be used for measurement of properties of metallic objects, sensor lift-off or nonconductive coating thickness.

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