Matrix Capture Approach for Eddy Current (EC) Inspection

Abstract

The machine implementation techniques described herein may include constructing eddy current sensor measurements using a matrix capture acquisition approach applied to data acquired using an eddy current array (ECA) probe. Such measurements may be established or selected to provide EC inspection results for different defect orientations, such as providing firmware or software configurability for detection orientation. The use of the matrix capture approach may be employed to perform lift-off sensing and associated compensation without requiring the use of a separate lift-off sensing element. The matrix capture approach enables inspection and lift-off sensing modalities different from the physical arrangement of the sensor used to perform the acquisition, such as providing inspection results corresponding to novel sensor structures.

Description

[Technical Field]

[0001] [Claiming priority] This patent application claims priority to Lepage's U.S. Provisional Patent Application No. 63 / 493308 (Agent Reference No. 6409.246PRV), filed on 30 March 2023, entitled "EDDY CURRENT SENSOR CONSTRUCTION USING FULL MATRIX CAPTURE (FMC) APPROACH," which is incorporated herein by reference in its entirety.

[0002] This specification, but not limited thereto, relates in general to apparatus and techniques for non-destructive testing, such as facilitating eddy current testing, and more specifically to apparatus and techniques for constructing eddy current sensor representations using a matrix capture acquisition approach applied to data obtained using eddy current array (ECA) probes. [Background technology]

[0003] Non-destructive testing (NDT) can refer to the use of one or more different techniques for inspecting areas on or within an object, for example, to determine whether a scratch or defect exists in the object under test, or to otherwise characterize the object under test. Certain types of NDT may include the use of an eddy current testing approach, in which electromagnetic energy is applied to an object, and the resulting induced current on or within the object is detected, and the value of the detected current (or associated impedance) provides indication of the structure of the object under test, such that it indicates the presence of cracks, scratches, voids, porosity, or other heterogeneity (e.g., corrosion or pitting). Generally, an eddy current (EC) sensor includes one or more sensor elements, such as induction coils that can be excited using an alternating current (AC) source. Such coils (or other electromagnetic sensing elements such as Hall sensors) can be used to receive signals indicating induced eddy currents on or within a structure in response to such excitation, using the same coil (e.g., connected via a bridge circuit) for both excitation and pickup, or one coil for transmission and another coil for pickup. Generally, whether a single-sensor eddy current test (ECT) or multi-sensor eddy current array (ECA) configuration is used, the sensor configuration is physically defined and fixed at the time of fabrication, not only by the physical geometric shape and arrangement of the coil elements, but also by the available interconnections between the coil elements and the instrument drive (e.g., transmitter) and pickup (e.g., receiver) channels. Therefore, the measurement modes and characteristics of commonly available sensors may be limited in terms of sensitivity to specific defect orientations or in terms of available modes for excitation and pickup. [Overview of the project]

[0004] In existing approaches, the physical configuration and orientation of eddy current sensors, such as coils or arrays of coils, generally determine performance characteristics such as sensitivity to defect orientation or lift-off. The inventors recognize, among other things, that such limitations may prevent a particular sensor configuration from being more effective in detecting certain types of defects, such as when the structure being inspected has an irregular surface or an unknown defect orientation. Because a particular sensor configuration may result in the inability to detect a particular defect orientation, the use of existing approaches may require multiple campuses with EC sensors or arrays of such sensors mounted in different orientations to ensure that the desired coverage is achieved.

[0005] For example, a differential sensor may be formed using two coils connected to the inputs of a differential amplifier in such a way that residual output is neutralized to indicate a defect-free component state. However, differential signal indices may be synthesized in other ways. Assuming the behavior of a linear sensor, two complex-valued measurements corresponding to each sensor in a differential pair can be made individually, and the difference can be determined later during analysis, providing results equivalent to direct analog difference measurement. The inventors recognize, among other things, that the concept of linearly combining measurements corresponding to different transmit / receive pairs can be extended beyond synthetically forming a differential sensor. Linearly combining measurements from three or more sensors can generate a very wide range of synthetic sensor configurations, such as providing configurable selectivity for sensing different defect orientations without requiring the physical reorientation of the sensor assembly during inspection, and can be used for eddy current testing. The inventors also recognize that lift-off sensing (LOS) and corresponding lift-off compensation (LOC) can also be performed using such an approach.

[0006] The desired composite sensor configuration does not need to be specified in advance. For example, the acquisition of measurements can be performed using some or all different permutations of the sensor transmit / receive pairs. Such an acquisition approach may also be referred to as a matrix capture approach, with full matrix capture referring to the acquisition of all different permutations of the sensor transmit / receive pairs. Parallel acquisition can increase acquisition efficiency when multiple receiver channels are available (e.g., simultaneously supporting transmission from one sensor while receiving signals from several other sensors simultaneously, or supporting even the same sensor as the transmitter using an impedance measurement mode, such as one implemented using a bridge circuit). After matrix capture, subsequent analysis can be performed by adjusting one or more sensor weights (referred to herein as gain values ​​(gain coefficients)) or other parameters and performing a sum (e.g., a linear combination) of different acquired measurements to achieve a specified composite sensor configuration. For example, an angular skew parameter can be selected to form a composite sensor that is sensitive to longitudinal or transverse (LT) orientation defects relative to the physical sensor array, or sensitive to a specified oblique angle. Such a series of summaries can provide coverage during post-acquisition analysis for various different potential defect orientations without requiring physical rescanning in different sensor orientations. [Means for solving the problem]

[0007] In one embodiment, a machine implementation for performing eddy current measurements using matrix capture may include generating excitation signals for elements in an eddy current array (ECA) sensor, routing the excitation signals to selected transmitting elements among the elements, and receiving and digitizing eddy current measurements from each receiving element among the elements in response to the excitation signals. The machine implementation may also include constructing a composite measurement by aggregating the eddy current measurements received for different transmit / receive pairs of elements, including applying gain coefficients based on the transmitting element index and the receiving element index. Each gain coefficient may include the product of a gain coefficient corresponding to the transmitting element index and a gain coefficient corresponding to the receiving element index. In another approach (e.g., for lift-off sensing), each gain coefficient may be uniquely defined based on both the transmitting element index and the receiving element index.

[0008] A system for performing eddy current measurements using matrix capture may include a transmitter circuit configured to generate excitation signals, a receiver circuit configured to receive eddy current measurements, a multiplexer configured to selectively route excitation signals to selected sensors in an eddy current array (ECA) sensor, a processor circuit communicatively coupled to the transmitter circuit, the receiver circuit, and the multiplexer circuit, and a memory circuit communicatively coupled to the processor circuit, the memory circuit having instructions, when executed by the processor circuit, that cause the system to perform machine implementations described in the embodiments described above or elsewhere in this specification.

[0009] This summary is intended to provide an overview of the subject matter of this patent application. It is not intended to provide an exclusive or exhaustive description of the invention. A more detailed description is included to provide further information relating to this patent application. [Brief explanation of the drawing]

[0010] [Figure 1]A figure including a non-destructive inspection system that can be used to implement at least some of one or more technologies as shown and described in this specification. [Figure 2] A figure showing an example of a planar crossed-wire sensor (CWS) eddy current array that can be fabricated using a rigid or flexible printed circuit assembly having two metallization layers. [Figure 3] A figure showing an example of a bridge circuit that can be used to acquire eddy current measurements when the same coil element is used as both a transmitter and a receiver. [Figure 4A] A figure showing an example of the sum of the imaginary parts of measured eddy current signals acquired using a matrix capture approach, and using different normalization factors to weight the sum of measurements acquired using a bridge configuration with respect to separate transmit and receive sensors, for purposes of illustration. [Figure 4B] A figure showing an example of the sum of the imaginary parts of measured eddy current signals acquired using a matrix capture approach, and using different normalization factors to weight the sum of measurements acquired using a bridge configuration with respect to separate transmit and receive sensors, for purposes of illustration. [Figure 5] A figure showing an example of two different measurement sensor orientations, associated steel with notches extending to four different depths, and a test specimen. [Figure 6] A figure and photograph showing an example of a graphical representation of vertical (e.g., imaginary part) amplitude versus time for different angular skew parameter (e.g., β) values, where a scan is being performed on a steel test specimen as shown in FIG. 5 for different physical measurement sensor orientation (e.g., θ) values. [Figure 7A] A figure showing designations for different elements within a CWS array configuration. [Figure 7B] A figure showing the gain values used to establish a lift-off sensing channel from eddy current matrix capture (ECMC) acquisitions. [Figure 7C]An example of a total value parametrically plotted in an impedance plan view where addition is performed using the fact that the total is the gain value of FIG. 7B, and a diagram for explaining that the lifted acquisition trace still shows a defect in a direction orthogonal to the remaining part of the scan trace in the impedance plane. [Figure 8A] A diagram showing an example of normalized vertical amplitude values without lift-off compensation for different lift-off heights used to scan a notch in a test sample. [Figure 8B] As described above, a diagram showing an example of normalized vertical amplitude values to which lift-off compensation is applied using a composite lift-off sensor established using the gain value shown in FIG. 7B. [Figure 8A] A diagram showing an example of normalized vertical amplitude values without lift-off compensation for different lift-off heights used to scan a notch in a test sample. [Figure 8B] As described above, a diagram showing an example of normalized vertical amplitude values to which lift-off compensation is applied using a composite lift-off sensor established using the gain value shown in FIG. 7B. [Figure 9] A diagram generally exemplifying technologies such as a machine implementation method. [Figure 10] A diagram of an example including a machine in which any one or more of the technologies (e.g., methodologies) considered in this specification can be implemented.

Mode for Carrying Out the Invention

[0011] In drawings not necessarily drawn to an exact scale, like numbers can identify like components in different views. Like numbers with different letter suffixes can represent different instances of similar components. The drawings, while not limiting, generally illustrate various embodiments considered in this document as examples.

[0012] The machine implementation techniques described herein may include constructing eddy current sensor measurements using a matrix capture acquisition approach applied to data acquired using an eddy current array (ECA) probe. Such measurements can be used to synthesize EC inspection results for different defect orientations, such as providing firmware or software configurability of detection orientation, including changing such configurations during post-analysis of previously acquired eddy current matrix capture (ECMC) measurement data. The use of the matrix capture approach can also be used to perform lift-off sensing and associated compensation without requiring physically separate lift-off sensors (or instead). The matrix capture approach enables inspection and lift-off sensing modalities different from the physical arrangement of sensors used to perform acquisitions, using a synthetic sensor configuration that can be operated without requiring reacquisition of measurement data. The approaches described herein may also provide measurement or lift-off sensing modalities corresponding to new sensor structures, including digitally aggregating measurements from matrix capture acquisitions in a manner not achieved using analog aggregation of physical sensors and acquired signals.

[0013] Figure 1 is a schematic diagram outlining an example including a non-destructive testing system (system) 100 that can be used to implement at least one or more of the techniques shown and described herein. The non-destructive testing system 100 may include a test instrument 140, such as a handheld or portable assembly. The test instrument 140 can be electrically coupled to a probe assembly 150, such as using a multi-conductor interconnect 130. The probe assembly 150 may include one or more sensors, such as an eddy current coil array (ECA) 154. The EC coils are electromagnetically coupled to a target 158 ​​(e.g., a test specimen or "object under test"), and the non-destructive testing system 100 can be used to detect defects 160 using one or more techniques shown and described herein. The ECA 154 can be a four-coil planar cross-winding sensor (CWS), as shown in Figure 2 and shown and described in relation to various embodiments herein, such as: The use of the CWS in Figure 2 is illustrative only, and other sensor configurations (having more than four or fewer coil elements) can be used. The ECA154 can follow a linear or curved contour, or otherwise include an array of elements extending along multiple axes. The size and pitch of the elements can be varied depending on the inspection application.

[0014] A modular probe assembly 150 configuration can be used, which allows the test apparatus 140 to be used with various different probe assemblies. The test apparatus 140 may include one or more digital and analog circuit configurations, such as a front-end circuit 122, which includes a transmit signal chain (forming a transmitter circuit), a receive signal chain (forming a receiver circuit), or a switching circuit configuration (e.g., a multiplexer circuit 123). The transmit signal chain may include amplifier and filter circuit configurations that provide alternating current (AC) excitation signals for delivery to the probe assembly 150 through the interconnect 130. The front-end circuit 122 can be controlled to implement a matrix capture acquisition approach, as shown and described elsewhere in this specification.

[0015] Figure 1 shows a single probe assembly 150 and a single ECA 154, but other configurations may be used, such as multiple probe assemblies connected to a single test instrument 140, or multiple ECA 154s used with a single probe assembly 150. Similarly, the test protocol may be implemented using coordination between multiple test instruments 140, for example, in response to an overall test scheme established from each test instrument 140, or by another remote system such as a computing facility 108 or a general-purpose computing device such as a laptop 132, tablet, smartphone, or desktop computer. The test scheme may be established in accordance with published standards or regulatory requirements and may be implemented, as an exemplary example, at the time of initial fabrication or repeatedly for ongoing monitoring.

[0016] The front-end circuit 122 may be coupled to and controlled by one or more processor circuits, such as the processor circuit 102 which is included as part of the test apparatus 140. The processor circuit may be coupled to the memory circuit 104 to, for example, cause the test apparatus 140 to execute instructions to perform one or more of the following: EC acquisition (e.g., matrix capture acquisition), processing, or storage of data related to EC inspection, or otherwise to perform techniques as shown and described herein. The test apparatus 140 may be communicably coupled to other parts of the non-destructive testing system 100, for example, by using a wired or wireless communication interface 120. In general, as described elsewhere in this specification, EC inspection may include establishing a composite sensor configuration from acquired matrix capture data.

[0017] The performance of one or more techniques as shown and described herein may be achieved on the test apparatus 140 or using other processing or storage equipment, such as a computing device 108 or a laptop 132, tablet, smartphone, or desktop computer. For example, processing tasks that would be unnecessarily slow if performed on the test apparatus 140 or beyond the capabilities of the test apparatus 140 may be performed remotely (e.g., on a separate system), such as in response to a request from the test apparatus 140. The test apparatus 140 may include a display 110 for presenting configuration information or results, and an input device 112 including one or more of the following for receiving operator commands, configuration information, or responses to queries: a keyboard, trackball, function keys or soft keys, mouse interface, touchscreen, stylus, etc.

[0018] As shown and described herein, eddy current measurement signals acquired from different transmit / receive combinations of sensors (e.g., complex-valued time-series measurements, or complex-valued measurements including received signal values ​​associated with encoded position or other synchronization information) can be linearly combined, for example, by using sums, taking into account the assumptions of linearity and superposition. A matrix capture approach may be used, which can acquire some or all possible permutations of different transmit / receive combinations to provide a dataset in a manner similar to full matrix capture (FMC) in the context of acoustic inspection. The use of eddy current matrix capture (ECMC) as shown and described herein does not require knowledge of propagation path time delay, unlike acoustic inspection beamforming approaches such as total focusing methods. Instead, as shown and described herein, the inventors recognize that gain values ​​can be assigned to individual elements or individual pairs of elements, and the resulting composite sensor can be formed after acquisition by selecting such gain values ​​or other parameters. Gain values, while not required, can be established in a physically informed manner based on the geometric shape of the physical sensor, enabling the synthesis of a composite sensor during post-analysis corresponding to either a physical sensor configuration or a non-physical sensor configuration (such as those considered below in relation to the synthesis of lift-off sensing approaches). Complex-valued impedance plane measurements for such a composite sensor involve aggregating (e.g., summing) the values ​​from each individual transmit / receive pair, as can be represented as shown below.

[0019]

number

[0020] In equation (1) above, the complex-valued impedance plane measurement S S This refers to individual measurement values ​​S for a group of sensor elements (for example, having a count of M transmitting elements and a count of N receiving elements). mnThis represents the sum of the gain values ​​(gain coefficients) for each corresponding element. m , G n The gain is applied according to the index {m, n} corresponding to a specific transmit / receive pair of sensor elements. For example, the transmit element index may be represented by m, and the receive element index may be represented by n. As considered below, such gain values ​​may be established based on an analysis of the physical configuration of the sensor array used for acquisition, or the gain values ​​applied in such sums may be determined using other criteria (such as a base empirical evaluation for use as a synthetic lift-off sensor, as described elsewhere herein). In practice, matrix capture acquisition may involve selecting a specific transmit / receive pair in an eddy current array using a multiplexer (e.g., multiplexer circuit 123) to acquire impedance plane or other measurements. The state of the multiplexer can then be changed to perform measurements in a serial manner using another transmit / receive pair, etc. If multiple receiver amplifier channels are available, some or all of the other elements may be sampled simultaneously with (e.g., in parallel with) the transmission from a given transmitter element. As considered below, impedance measurement modes such as a bridge configuration may be used so that even the sensor used for transmission can be used as a receiver and sampled simultaneously with other receiver channels. The individual transmit / receive acquisition rates can be made sufficiently short in duration so that changes in the ECA's position during scanning do not introduce unacceptable errors. In this way, each measurement of different transmit / receive combinations used for the sum of the matrix captures can be treated as if they were obtained simultaneously from the same spatial position of the ECA assembly, even if they are not all sampled literally at the same time.

[0021] FIG. 2 is a schematic diagram showing an example of a planar crossed-wire sensor (CWS) eddy current array (ECA) 254 that can be fabricated using a rigid or flexible printed circuit assembly having two metallization layers. The use of a four-coil configuration for the ECA 254 is merely illustrative, and the approach described herein is believed to be applicable to other array configurations. The ECA 254 of FIG. 2 can be fabricated such that two coil elements (e.g., EL.1 and EL.2) are located on one metallization layer and the other two elements (e.g., EL.3 and EL.4) are located on another metallization layer. Each coil element can include a port having two conductors such that the coil element can be driven therethrough or connected to a receiver (or both simultaneously if a bridge configuration is used). The arrangement of the four coil elements shown in FIG. 2 is illustrative but non-limiting. For example, the coil elements can be selected from among more elements in an array having a number of elements greater than four. For example, as an example of an ECA configuration that can include more than four sensor coils and can select four coils in a manner similar to the example of FIG. 2, see U.S. Patent No. 8,816,680 (Lepage).

[0022] For the CWS ECA 254 shown in FIG. 2, in relation to the skew angle parameter (β), considering the measurement contributions from each coil for controlling the sensing axes (“+” and “-”), the corresponding sets G m , G n can be established. The term “sensing axis” refers to the orientation of the long dimension of an elongated defect such as a crack that can be detected by the sensor. Generally, for the CWS ECA 254, the sensing axes are offset by +45° or -45° from β, as shown in FIG. 2. As an example, in a measurement configuration where EL.2 and EL.4 are driven differentially and EL.1 and EL.3 are used differentially as pickups, β = 45° and the sensitivity axes are aligned at 90° and 0°. The following relationships can be applied to establish G m and G n , and the terms on the left side of the following equation (2) are, respectively, the currents I A , IB This represents the equivalent current vector from the linear superposition of orthogonal coils A and B that carry current.

[0023]

number

[0024]

number

[0025]

number

[0026] Generally, equation (2) assumes that the magnitude of the term on the left side is constant, and equations (3) and (4) assume the respective current I A ,I B We show that each of these is set based on the projection of their contributions to the angular skew parameter β. Since reciprocity assumptions can be made in relation to the coils used for transmitting or receiving, and the simplest CWS configuration has coils oriented orthogonally to each other, other constraints may also apply.

[0027]

number

[0028] The additional constraints are that the respective element gain values ​​G must be observed, provided that the transmitters, which are opposite to each other, have the same magnitude but opposite signs of gain coefficients, and similarly, the receivers, which are opposite to each other, have the same magnitude but opposite signs of gain coefficients. m and G n This can be applied to establish the following constraints. In the case of a CWS consisting of four elements, such as the ECA254 in Figure 2, such constraints can be expressed as shown in equations (6) and (7) below, respectively.

[0029]

number

[0030]

number

[0031] Transmit gain value (G m ) and the received gain value (G n The following table can be used for a given angular skew parameter β value (e.g., -90° to +90°). These values ​​are derived through equation (7), in accordance with the above relationship in relation to equation (2). In this way, a composite sensor complex impedance plane measurement can be obtained by performing different summations using equation (1) above for different angular skew parameter β values. A series of such summations can be performed for matrix acquisitions corresponding to different time steps, as shown and explained below in relation to the example shown in Figure 6. Table 1 shows the transmit coil gain (G) for summation. m Table 2 shows the value of the receiving coil gain (G) for the total. n Table 3 shows the vertical / horizontal (L / T) gain product (G) for the total. m G n ) indicates.

[0032] [Table 1]

[0033] [Table 2]

[0034] [Table 3]

[0035] "Full" matrix acquisition is (for example, complex values ​​(measurements) S mnThe impedance plane measurement (corresponding to) can be defined as the case where it is obtained for all gain product in Table 3. Generally, as considered above, when n <> m (where <> above means inequality), each selected transmitting coil is driven independently of each receiving coil for the corresponding measurement. Since the same coil is both driven and used for measurement, there may be challenges with respect to diagonal elements in the matrix in Table 3 where n = m. A bridge configuration can be used for both driving and receiving signals from the same coil. For example, Figure 3 is a schematic diagram showing an example of a simplified bridge circuit 300 configuration for the purposes of consideration. Generally, each sensor coil 354 is selected (for example, one of EL.1, EL.2, EL.3, EL.4 when a 4-element CWS is used as shown in Figure 2). A signal source 325 (e.g., "TX") can drive two nodes in the bridge circuit 300. An amplifier circuit 327 (e.g., a differential amplifier) ​​can be used to measure the other two nodes to detect any imbalance. A lock-in amplifier or other phase-coherent measurement technique (e.g., high-speed digitization and comparison of TX and RX signals using a common time base) may be used to measure both amplitude and phase information. Before obtaining the measurement, the bridge circuit 300 may be balanced, for example, by disabling any indicator. One approach to balancing may include varying the reference impedance Z1 so that the Z1 to Z3 ratio matches the Z2 to ZL ratio in the absence of defects or lift-off.

[0036] One or more reference impedances within the bridge circuit 300 (such as those generated by the test coil or other structures) may affect the sensitivity of the bridge circuit 300, and the bridge circuit 300 would generally not be used for measurements where the transmitting coil and receiving coil are different. Therefore, the inventors also recognize that the measurement sensitivity differs between measurements when n=m (depending on the bridge sensitivity) and measurements when n<>m. This variation can be explained by applying a scaling ratio k, which is the gain value G for terms in the sum in the case of n=m (e.g., the diagonal elements in Table 3). m ,G n Separately, the measured value S in the sum of equation (1) mn It can be multiplied by . As an example of the measurement configuration used in the experimental data described herein, Figures 4A and 4B are graphs showing an example of the sum of the imaginary parts of measured eddy current signals acquired using a matrix capture approach. As shown in Figure 4, different scaling factors (k values) are used to weight the sum measurements acquired using a bridge configuration for separate transmitting and receiving sensors. The nominal value of k gives the sensitivity of the bridge configuration measurement (n=m), which is equivalent to the sensitivity of the measurement when the transmitting and receiving sensors are different (n<>m).

[0037] The plots shown in Figures 4A and 4B are vertical amplitude channel strip chart representations, obtained by summing measurements acquired by scanning a second sensor 554B, which is a CWS ECA sensor, across an aluminum sample with a scribed notch, as shown in Figure 5, with a sensor skew angle (e.g., the tilt as shown in the orientation of the second sensor 554B in Figure 5) of θ=45°. For the purpose of summing, the skew angle parameter was also set to β=45°. The summing was performed for each sample in the strip chart (e.g., each point in the strip chart plot representing the imaginary part of the sum result corresponding to the vertical direction in the impedance plane). Aluminum is used because it generally produces strong lift-off variations. For k-value extremes (e.g., k=0 or k=1), a strong lift-off index occurs due to a sensitivity mismatch between the bridge configuration and the other receiving channels. In an idealized scenario, a perfect CWS configuration does not exhibit any lift-off artifacts, so empirically, k=0.1 appears to produce a sum when the sensitivity of the bridge measurement configuration and the other channels are at least approximately equivalent. Figure 4A was obtained using a measurement frequency of 500 kHz, and Figure 4B was obtained using a measurement frequency of 1 MHz. Similar results were obtained using steel samples, indicating that the k value is likely governed by the sensor and bridge circuit configuration, rather than by the material or the test frequency (at least within the range of frequencies used for evaluation).

[0038] The inventors recognize that another cause of variation in the output from the total can be caused by destructive interference effects in the physical sensor configuration. Therefore, a global compensation coefficient can be determined and applied to the total result. Such a compensation coefficient may depend on parameters such as the angular skew parameter (β). For example, the transmitter gain compensation coefficient can be derived assuming the superposition of flux contributions from each coil element and is expressed by equation (8) below.

[0039]

number

[0040] As with other embodiments herein, reciprocity assumptions can be made, and the same compensation coefficients can be assumed for the behavior of the receivers. Thus, the modified sum with the compensation coefficients can be expressed as shown in equation (9) below.

[0041]

number

[0042] Figure 5 is a schematic diagram showing an example of two different measurement sensor orientations (showing a tilt θ=0° for the first sensor 554A orientation and θ=45° for the second sensor 554B orientation) and an associated steel specimen (object under test) 558 having four different depths of notches 560A, 560B, 560C, and 560D. For the experimentally obtained results shown in Figure 6 below, the CWS sensor shown in Figure 5 was mechanically scanned across the steel specimen 558 using the dashed line and aligned centerline axis C of the sensor assembly, as shown superimposed on the steel specimen 558, scanned in the direction indicated by the arrow. Several scans were performed for different tilt angles, θ=0°, 90°, 45°, -45°, and 22.5°. Such tilt angles are different from the angular skew value (angular skew parameter) (β) used when performing the summation, as discussed above. Figure 6 shows an example of a graphical representation of vertical (e.g., imaginary part) amplitude versus time for different angular skew parameter (e.g., β) values. In Figure 6, scans are performed on a steel test specimen for the different physical measurement sensor orientation (e.g., θ) values ​​described above, as shown in Figure 5.

[0043] The image shown in Figure 6 is defined by a horizontal axis representing time and is divided into different scan segments labeled for different physical tilt (θ) values, while the vertical axis is defined by different angular skew parameter (β) values ​​(in 2° increments) used for summing, corresponding to the combined CWS sensor orientation independent of the θ value. Each point in Figure 6 represents the summation result corresponding to its respective time index, and the row of pixels in Figure 6 corresponds to a specific β value. The brightness of each pixel corresponds to the magnitude of the vertical signal component (e.g., the imaginary part) of the summation result. The results in Figure 6 correspond to the expected behavior of a 4-coil CWS configuration, as a negative signal appears when β=θ (represented as a dark area of ​​vertical stripes corresponding to notches in the sample) and a positive signal appears when β is offset by +90° or -90° from θ. The summation in Figure 6 does not include the global compensation coefficient of equation (8), and therefore some degree of sensitivity reduction is evident around β=45°, regardless of the physical sensor orientation. Nevertheless, the results shown in Figure 6 verify that the matrix capture approach and summation reliably detect all four test sample notches for various physical sensor scan orientations, and that the notch orientation relative to the scan orientation can be confirmed through the synthesis of groups of summations calculated using either the magnitude of the vertical signal or different angular skew parameters. This indicates that all defect orientations can be reliably detected with just a single scan canvas having any sensor orientation.

[0044] The embodiments discussed above generally do not involve lift-off compensation or detection of the lift-off state. In one approach, lift-off compensation (LOC) may be used in combination with a CWS coil configuration, for example, by establishing a lift-off dependent gain compensation coefficient. The dynamic gain coefficient can be established using a separate coil that senses lift-off, but in such an approach, the lift-off sensing coil is generally physically separated from the CWS coils and spatially offset from the center of the CWS coil array. In contrast, the inventors recognize that, among other things, using the matrix capture approach described herein, a lift-off sensing (LOS) channel for use in lift-off detection or compensation can be synthesized without requiring a physically separate lift-off sensing coil.

[0045] The LOS channel can be synthesized from the same matrix capture acquisition used for other measurement sums, using a different gain matrix. The gain matrix used to synthesize the LOS can be established based on various criteria. Such criteria may include, in the impedance plane view, that the defect indices of the lift-off sensor signal are orthogonal or produce a slight change in the length of the vector from an index generated by a sensor position far from an arbitrary surface (e.g., air) to an index generated by a sensor position on the object under test. The behavior of such a vector is considered suitable for use as a lift-off sensor index when the vector behavior corresponds to the relationship shown below in equation (10), and the suitability for use as a lift-off sensing marker can be evaluated by evaluating the candidate lift-off sensor gain matrix and comparing it with the relationship in equation (10).

[0046]

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[0047] In equation (10), the total size used to determine the size of the lift-off sensor depends on the lift-off height z. The damping parameter b lift This can be fitted. The inventors also recognize that, among other things, they can define the gain matrix discussed above, derived from the physical principles associated with the transmitting or receiving coil, and then, instead of calculating the gain product for the combination of transmitting and receiving coils, they can use specific transmit / receive pair gain values ​​that are unique to each transmit / receive pair. The summation form of equation (1) can be modified to provide a more generalized formula.

[0048]

number

[0049] Using this approach, we obtain individual gain values ​​(G) corresponding to each combination of {m,n}. mn ) can be used. Gain matrices for use in LOS can be formed based on empirical exploration and taking into account the criteria described above. Another consideration may include reducing or minimizing temperature-dependent variations in the lift-off signal. One approach to establishing a gain matrix for use in LOS may include excluding (e.g., zeroing out or not including) contributions from diagonal elements in the matrix in the combined sensor measurement sum that correspond to measurements when the same sensor is used for both transmission and reception (for example, when impedance measurements are performed by using a bridge circuit). As an example, by omitting diagonal elements, drift (e.g., temperature drift) associated with bridge-based measurements corresponding to those diagonal elements can be removed.

[0050] Figure 7A shows the specifications for different elements in the CWS array configuration, and Figure 7B shows the corresponding gain values ​​used to establish a lift-off sensing channel from the eddy current matrix capture (ECMC) acquisition. Figure 7C shows an example of the summation parameterized in the impedance plane, where the summation is performed using the gain values ​​in Figure 7B, showing that the lift-off acquisition trace still exhibits defects in a direction orthogonal to the rest of the scan trace in the impedance plane.

[0051] As an example, Figure 7A shows a 4-coil CWS having coil elements labeled EL.1, EL.2, EL.3, and EL.4. Figure 7B shows a G that can be used in total having the form shown in equation (11). mn The corresponding matrix is ​​shown. As shown in Figure 7C, the balanced combination of near and far coil sensors used in the gain matrix of Figure 7B provides a defect signal orthogonal to the lift-off signal, as indicated by the trace corresponding to the 0mm lift-off condition and the horizontally overlapping 1mm lift-off condition, and the defect index extends outward as a “leg” extending upward from both the 1mm and 0mm traces. The signal values ​​shown in Figure 7C in the impedance plane take the ratio of the CWS measurements (determined using equation (9) with the corresponding gain value from Table 3 for the desired angular skew parameter value β), and the dynamically lift-off compensated (DLOC) measured value S defined by equation (12). DLOC In this, as shown below, the damping rate compensation term (where the argument is -b corr Along with the exponential function, other S can be calculated by dividing by the total size of the lift-off sensor (LOS) channels. s It can be used to scale the total value.

[0052]

number

[0053] b corrA suitable value for γ can be determined by observing the relationship between the lift-off vector length in the impedance plane and the defect amplitude attenuation rate with respect to the lift-off height. For example, Figure 8A shows an example of normalized vertical amplitude values ​​without lift-off compensation for different lift-off heights used to scan a notch in a test specimen using the matrix capture and summation approach discussed above, and Figure 8B shows an example of normalized vertical amplitude values ​​to which lift-off compensation is applied using a composite lift-off sensor established using the gain values ​​shown in Figure 7B, as discussed above. The measurement conditions for obtaining the vertical amplitude in Figure 8A and the lift-off compensation values ​​in Figure 8B included measuring notch 4 in the specimen shown in Figure 5, with β=θ=0°, and the lift-off values ​​were in the range of 0mm to 1.5mm at a test frequency of 500kHz. By normalizing the amplitude using a suitable γ value, an absolute amplitude of 1.0 was obtained on notch 4 at a lift-off of 0mm. To optimize the sensor operation in the lift-off range of 0-1mm, an attenuation rate adjustment coefficient b was determined based on empirical observations. corr I set it to 1.43.

[0054] In Figure 8A, an amplitude loss of approximately -27 dB occurs due to lift-off relative to the 0 mm reference condition. By applying the dynamic lift-off compensation described above, such amplitude fluctuations were reduced to within 2.6 dB. Other LOS gain matrices can be defined, such as those evaluated across different frequencies, materials, or surface conditions.

[0055] Figure 9 is a diagram illustrating a general technical flow 900, including a machine implementation method, which includes the following: In process 905, an excitation signal is generated and routed to a selected transmitting element, such as an eddy current array (ECA) sensor. In process 910, eddy current measurements are obtained by receiving and digitizing the signals detected by each receiving element (or multiple elements if multiple receiver channels are available). The measurements may include amplitude and phase data for the excitation signal. The operations in processes 905 and 910 may be repeated for all available transmit / receive permutations of elements in the ECA sensor, which may be referred to as performing a “full” matrix capture acquisition (looping through all possible {m,n} permutations). This may include permutations where the same element is used as both a transmit and receive element, as discussed elsewhere in this specification. In process 915, a composite sensor measurement (such as complex-valued measurement data) may be constructed by using the sum of each received eddy current measurement with corresponding gain coefficients applied, as discussed elsewhere in this specification. In process 951, determining the composite sensor measurements may include determining a series of measurements using various skew angle parameters (for example, to provide sensitivity to different defect orientations as discussed above).

[0056] Optionally, in process 920, a composite lift-off sensor measurement can be constructed. The same matrix capture acquisition may be used for both the construction of the composite measurement in process 915 and the construction of the composite lift-off sensor measurement in process 920. In process 925, the composite measurement (or measurement) constructed in process 915 may be adjusted, for example, to perform lift-off compensation (LOC) in a dynamic manner, as shown and described elsewhere in this specification. Other corrections may be performed. For example, optionally, global compensation may be applied to the composite measurement constructed in process 915, for example, based on angular skew parameter dependence, as considered elsewhere in this specification. The resulting composite measurement (either lift-off compensated or uncompensated) constructed in process 915 may be presented in an impedance plane or in a strip chart view of scalar values ​​(for example, corresponding to vertical amplitude values ​​from the impedance plane). Alternatively or additionally, matrix capture acquisition data, such as time-series data, may be recorded or archived, and the composite measurement may be constructed later based on specified analysis parameters.

[0057] Figure 10 is an example block diagram of a machine 1000 in which one or more of the techniques (e.g., methodologies) discussed herein may be implemented. The machine 1000 (e.g., a computer system) may include a hardware processor 1002 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), main memory 1004, and static memory 1006, which are connected via an interlink 1030 (e.g., a link or bus), and some or all of these components may constitute the hardware for the systems and associated implementations discussed above.

[0058] Generally, a hardware processor 1002 may include, for example, a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a composite instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP), a tensor processing unit (TPU), a neural processing unit (NPU), a vision processing unit (VPU), a machine learning accelerator, an artificial intelligence accelerator, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a radio frequency integrated circuit (RFIC), a neuromorphic processor, a quantum processor, or at least one of any combination thereof. The processor circuit may further be a multicore processor having two or more independent processors (sometimes referred to as "cores") capable of executing instructions simultaneously. A multicore processor includes multiple computing cores on a single integrated circuit die, each of which can independently execute program instructions in parallel. Parallel processing on a multicore processor may be implemented through architectures such as superscalar, VLIW, vector processing, or SIMD, which allow each core to execute separate instruction streams simultaneously. Processor circuits can be emulated as virtual processors or virtual circuits by software running on a physical processor. Virtual processors can behave like independent processors, but are implemented in software rather than hardware.

[0059] Specific examples of main memory 1004 include semiconductor memory devices that may include random access memory (RAM) and storage locations within semiconductors such as registers. Specific examples of static memory 1006 include non-volatile memory such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)) and flash memory devices, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, RAM, or optical media such as CD-ROM disks and DVD-ROM disks.

[0060] Machine 1000 may further include a display device 1010, an input device 1012 (e.g., a keyboard), and a user interface (UI) navigation device 1014 (e.g., a mouse). In one embodiment, the display device 1010, the input device 1012, and the UI navigation device 1014 may be touchscreen displays. Machine 1000 may further include a mass storage device (e.g., a drive unit) 1008, a signal generation device 1018 (e.g., a speaker), a network interface device 1020, and one or more sensors 1016 such as a global positioning system (GPS) sensor, a compass, an accelerometer, or other sensors. Machine 1000 may include an output controller 1028 for communicating with or controlling one or more peripheral devices (e.g., a printer, a card reader, etc.) via a serial (e.g., Universal Serial Bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near-field communication (NFC), etc.) connection).

[0061] The mass storage device 1008 may include a machine-readable medium 1022 that stores one or more sets of data structures or instructions 1024 (e.g., software) that embody or utilize any of the technologies or functions described herein. The instructions 1024 may also reside entirely or at least partially in the main memory 1004, the static memory 1006, or the hardware processor 1002 during their execution by the machine 1000. In one embodiment, one or any combination of the hardware processor 1002, the main memory 1004, the static memory 1006, or the mass storage device 1008 includes the machine-readable medium.

[0062] Specific examples of machine-readable media include one or more non-volatile memory such as semiconductor memory devices (e.g., EPROM or EEPROM) and flash memory devices, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, RAM, or optical media such as CD-ROM disks and DVD-ROM disks. Although machine-readable media are illustrated as a single medium, the term “machine-readable media” may include a single or multiple mediums configured to store one or more instructions 1024 (e.g., a centralized or distributed database, or associated caches and servers).

[0063] The apparatus of machine 1000 includes one or more of the following: a hardware processor 1002 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), main memory 1004 and static memory 1006, a sensor 1016, a network interface device 1020, an antenna, a display device 1010, an input device 1012, a UI navigation device 1014, a mass storage device 1008, an instruction 1024, a signal generation device 1018, or an output controller 1028. The apparatus may be configured to perform one or more of the methods or operations disclosed herein.

[0064] The term “machine-readable medium” includes any medium capable of storing, encoding, or carrying instructions for execution by machine 1000, causing machine 1000 to implement one or more of the technologies of this disclosure, or causing another device or system to implement one or more of the technologies, or storing, encoding, or carrying data structures used by or associated with such instructions. Non-limiting examples of machine-readable mediums include solid-state memory and optical or magnetic media. Specific examples of machine-readable mediums include non-volatile memory such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)) and flash memory devices, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, random access memory (RAM), or optical media such as CD-ROM and DVD-ROM disks. In some embodiments, machine-readable medium includes non-temporary machine-readable medium. In some embodiments, machine-readable medium includes machine-readable medium that is not a temporary propagating signal.

[0065] Instruction 1024 may be transmitted or received via a communication network 1026 using a transmission medium via a network interface device 1020, for example, using one of several transmission protocols (e.g., Frame Relay, Internet Protocol (IP), Transmission Control Protocol (TCP), User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), etc.). Illustrative communication networks include, among others, local area networks (LANs), wide area networks (WANs), packet data networks (e.g., the Internet), mobile telephone networks (e.g., cellular networks), conventional telephone service (POTS) networks, and wireless data networks (e.g., the IEEE 802.11 family of standards known as Wi-Fi®), the IEEE 802.15.4 standard family, the Long-Term Evolution (LTE) 4G or 5G standard family, the Universal Mobile Communications System (UMTS) standard family, peer-to-peer (P2P) networks, and satellite communication networks.

[0066] In one embodiment, the network interface device 1020 includes one or more physical jacks (e.g., Ethernet, coaxial, or interconnect) or one or more antennas for accessing the communication network 1026. In one embodiment, the network interface device 1020 includes one or more antennas for wireless communication using at least one of the following technologies: single input multiple output (SIMO), multiple input multiple output (MIMO), or multiple input single output (MISO). In some embodiments, the network interface device 1020 wirelessly communicates using multi-user MIMO technology. The term “transmission medium” should be understood to include any intangible medium capable of storing, encoding, or holding instructions for execution by machine 1000, and including digital or analog communication signals or other intangible mediums for facilitating communication of such software.

[0067] [Various notes] Each of the non-limiting embodiments described herein may stand alone or may be combined in various permutations or combinations with one or more of the other embodiments or subjects described herein.

[0068] The above detailed description includes references to the accompanying drawings, which form part of the detailed description. The drawings illustrate, for illustrative purposes, specific embodiments in which the present invention can be carried out. These embodiments are also commonly referred to as “Examples.” Such Examples may include elements in addition to those illustrated or described. However, the inventors also intend to include Examples in which only the illustrated or described elements are provided. Furthermore, the inventors also conceive of Examples using any combination or permutation of those elements (or one or more of their aspects) illustrated or described in relation to any specific embodiment (or one or more aspects thereof) shown or described herein, or in relation to any other embodiment (or one or more aspects thereof).

[0069] In the event of any conflict between the usage described herein and any document incorporated in such manner by reference, the usage described herein shall prevail.

[0070] In this specification, the term “or” is used to refer to a non-exclusive OR, such that “A or B” includes “A but not B,” “B but not A,” and “A and B.” In this specification, the terms “including” and “therefore” are used as plain English equivalents of the terms “equipped with” and “therefore.” Furthermore, in the following claims, the terms “including” and “equipped with” are not limiting; that is, any system, device, article, composition, formulation, or process that includes elements in addition to those listed after such terms in a claim is still considered to be within the scope of that claim. Moreover, in the following claims, terms such as “first,” “second,” and “third” are used merely as labels and are not intended to impose numerical requirements on their objects.

[0071] Examples of methods described herein may be at least partially machine or computer implements. Some embodiments may include computer-readable or machine-readable media encoded with instructions that can be operated to configure an electronic device to implement the methods described in the embodiments described above. Implementations of such methods may include code such as microcode, assembly language code, or higher-level language code. Such code may include computer-readable instructions for implementing various methods. The code may form part of a computer program product. Such instructions may be read and executed by one or more processors to enable the implementation of operations, for example, a method. The instructions may be in any preferred form, but are not limited to, source code, compiled code, interpreted code, executable code, static code, dynamic code, and so on. Furthermore, in one embodiment, the code may be tangibly stored in one or more volatile, non-temporary, or non-volatile tangible computer-readable media during execution or at other times. Examples of these tangible computer-readable media include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact discs and digital video discs), magnetic cassettes, memory cards or sticks, random access memory (RAM), and read-only memory (ROM).

[0072] The above description is intended to be illustrative and not restrictive. For example, the embodiments (or one or more aspects thereof) described above may be used in combination with one another. Other embodiments may be used, for example, by those skilled in the art when reviewing the above description. The abstract is provided to enable readers to quickly confirm the nature of the technical disclosure. The abstract is submitted with the understanding that it is not to be used to interpret or limit the scope or meaning of the claims. Also, in the above detailed description, various features may be grouped together to streamline the disclosure. This should not be interpreted as meaning that any disclosed features not claimed are essential to any patent claim. Rather, the subject matter of the invention may lie in fewer features than all the features of a particular disclosed embodiment. Accordingly, the following claims are incorporated into the detailed description as examples or embodiments, and each claim exists independently as a separate embodiment, and such embodiments are intended to be able to be combined with one another in various combinations or permutations. The scope of the invention should be determined by referring to the appended claims, together with the entire scope of equivalents to which such claims are entitled.

Claims

1. A machine method for performing eddy current measurements using matrix capture, Regarding the elements within an eddy current array (ECA) sensor, The process involves generating an excitation signal and routing the excitation signal to a transmitting element selected from among the elements, In response to the excitation signal, the system receives eddy current measurement values ​​from each of the receiving elements and digitizes them. A machine implementation method comprising constructing a composite measurement value by aggregating eddy current measurements received for different transmit / receive pairs of elements, including applying a gain coefficient based on a transmit element index and a receive element index.

2. The machine implementation method according to claim 1, wherein each gain coefficient is the product of a gain coefficient corresponding to the transmitting element index and a gain coefficient corresponding to the receiving element index.

3. The machine implementation method according to claim 1, wherein the gain coefficient is uniquely defined based on both the transmitting element index and the receiving element index.

4. The machine implementation method according to any one of claims 1 to 3, wherein the gain coefficient is parameterized using at least one parameter.

5. The machine implementation method according to claim 4, comprising applying global gain compensation to the composite measurement using the at least one parameter.

6. The machine implementation method according to claim 4 or 5, wherein at least one parameter used to parameterize the gain coefficient has an angular skew parameter corresponding to the composite sensor orientation.

7. The machine implementation method according to any one of claims 1 to 6, comprising applying lift-off compensation to the composite measurement value.

8. The machine implementation of claim 7, wherein applying the lift-off compensation comprises aggregating the received eddy current measurements for detections of the different transmit / receive pairs and applying a different gain coefficient than the one used to construct the composite measurement, thereby constructing a composite lift-off measurement.

9. The machine implementation method according to any one of claims 1 to 8, wherein the aggregation of the received eddy current measurements comprises performing a summation, the terms in the summation corresponding to different received eddy current measurements scaled by a corresponding gain coefficient.

10. The machine implementation method according to any one of claims 1 to 9, wherein the eddy current measurement value is converted to a complex value.

11. The machine implementation method according to any one of claims 1 to 10, wherein the different transmit / receive pairs include permutations in which the same element in the ECA sensor is used simultaneously as both a transmit element and a receive element.

12. The machine implementation method according to claim 11, wherein the same element in the ECA sensor is used as both the transmitting element and the receiving element to receive the eddy current measurement, and the use of an impedance measurement is performed.

13. A machine implementation method according to any one of claims 1 to 12, comprising establishing a series of composite measurements corresponding to different times.

14. The machine implementation method according to claim 13, comprising generating a presentation that plots the series of composite measurements on an impedance plane view with parameters.

15. The machine implementation method according to claim 13, comprising generating a presentation that plots scalar values ​​derived from the series of composite measurements as a time-series strip chart.

16. The machine implementation method according to any one of claims 1 to 15, wherein constructing the composite measurement value comprises aggregating the eddy current measurement values ​​received for all available transmit-receive pair permutations.

17. A system for performing eddy current measurements using matrix capture, A transmitter circuit configured to generate an excitation signal, A receiver circuit configured to receive eddy current measurements, A multiplexer configured to selectively route the excitation signal to a selected sensor within an eddy current array (ECA) sensor, A processor circuit that is communicatively coupled to the transmitter circuit, the receiver circuit, and the multiplexer circuit, A system comprising: a memory circuit communicably coupled to the processor circuit, wherein, when executed by the processor circuit, the memory circuit causes the system to carry out the method according to any one of claims 1 to 16.

18. The system according to claim 17, further comprising a bridge circuit configured to perform impedance measurement.

19. The system according to claim 17 or 18, further comprising the ECA sensor.

20. The system according to any one of claims 17 to 19, wherein the ECA sensor has a flexible planar sensor comprising at least four sensor coil elements.

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