Measurement of the inclination and curvature of a metal plate in a rolling mill

Abstract

To provide a measurement device for measuring properties of a metal sheet processed in a rolling mill.SOLUTION: The measurement device includes an inspection coil set, which includes a transmitter coil (108) and a receiver coil (110), the transmitter coil being configured to apply a time-varying magnetic field to the metal sheet, and the receiver coil being configured to detect a magnetic field transient produced from the metal sheet. The properties of the metal sheet are derivable from the magnetic field transient. A set of correction coils (116, 118, 122, 124) is for detecting a spatial deviation of the metal sheet from a reference plane, each correction coil being connectable to a capacitor to form a respective resonance circuit having a resonance frequency. The correction coils are resonated at the respective resonance frequencies. A shift in the resonance frequency in the presence of the metal sheet is detectable and the spatial deviation is derivable from the shifts.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a measuring device for measuring the properties of a metal sheet processed in a rolling mill. The present invention further relates to a rolling mill and a method for detecting a spatial displacement from a reference plane of a metal sheet processed in the rolling mill.

Background Art

[0002] The rolling of metals generally relates to producing a metal workpiece having a thin and uniform thickness by rolling a metal workpiece between two rotating work rolls.

[0003] To ensure high product quality, the thickness of the workpiece is accurately monitored and controlled.

[0004] The conventionally used pulsed eddy current measurement technique is based on measuring the eddy current induced in a metal sheet by a rapidly changing magnetic field applied to the metal sheet. Based on the measured eddy current, for example, the resistivity and thickness of the extracted metal sheet are determined.

[0005] When the metal sheet is completely parallel to the sensor, only two coils are required to accurately measure the properties of the metal sheet. However, in practice, since the metal sheet is not necessarily parallel to the sensor, the curvature and inclination of the metal sheet with respect to the sensor affect the measurement, and the estimation of the properties of the metal sheet becomes inaccurate.

[0006] Therefore, it is desired to improve the accuracy of metal sheet measurement in a rolling mill.

Summary of the Invention

Problems to be Solved by the Invention

[0007] In view of the above and other drawbacks of the prior art, an object of the present invention is to provide a measuring device that at least partially alleviates the drawbacks of the prior art. The proposed embodiments provide an improved method for detecting spatial displacements such as the curvature and inclination of a metal sheet processed in a rolling mill. **Means for Solving the Problems**

[0008] According to a first aspect of the present invention, there is provided a measuring device for measuring the characteristics of a metal sheet processed in a rolling mill.

[0009] The measuring device includes an inspection coil set including a transmitting coil and a receiving coil. The transmitting coil is configured to apply a time-varying magnetic field to the metal sheet, and the receiving coil is configured to detect a transient magnetic field generated from the metal sheet in response to the applied time-varying magnetic field. At least one characteristic of the metal sheet is derivable from the transient magnetic field.

[0010] The measuring device includes a correction coil set for detecting the spatial displacement of the metal sheet from a reference plane. Each correction coil is connectable to a capacitor and forms a respective resonant circuit having a resonant frequency. The correction coils are configured to resonate at their respective resonant frequencies, and a shift in the resonant frequency in the presence of the metal sheet is detectable. The spatial displacement is derivable from the shift in the resonant frequency.

[0011] The present invention is based at least in part on the realization that spatial displacement is measured by correction coils resonating at a resonant frequency and that the resonant frequency is shifted in the presence of the metal sheet.

[0012] The frequency shift is a shift in the resonant frequency of the resonant circuit including the correction coil, and this shift is caused by the inductive contribution from a metal sheet disposed in the vicinity of the correction coil. Thus, the nominal resonant frequency of the resonant circuit can be first measured or estimated in the absence of the metal sheet, and the frequency shift is the deviation of the resonant frequency from the nominal resonant frequency.

[0013] For example, when the metal plate is not parallel to the reference plane provided by, for example, the plane of the sensor head or the correction coil, the inductive components of the resonant circuits of the two correction coils will be different from each other due to the different inductive contributions of the metal plate. Therefore, the frequency shifts of the correction coils are different from each other, and thereby the inclination of the metal plate can be detected.

[0014] In the proposed measuring device, it is possible to avoid adding additional polarities and parasitic capacitances to the inspection coil system.

[0015] The reference plane can be arbitrarily selected, but it is preferably parallel to the plane of the correction coil. The main axis of the magnetic field generated by the correction coil can be perpendicular to the reference plane.

[0016] Preferably, the correction coils are arranged so as to minimize the coupling and crosstalk with the inspection coils. This can be achieved by various conceivable methods. One method is to arrange the correction coils far from the inspection coils. For example, when the correction coils and the inspection coils share a common support, the correction coils may be arranged near the edge or corner of the support, and the inspection coils may be arranged near the center of the support. Such a support may be, for example, a carrier substrate that can be flat.

[0017] The characteristics of the metal plate measured by the inspection coil can be at least one of the distance to the sensor head, the resistivity of the metal plate, and the thickness of the metal plate.

[0018] The spatial displacement of the metal plate can be at least one of the curvature of the metal plate and the inclination of the metal plate. The curvature can be, for example, the local curvature of the metal plate.

[0019] The inspection coil operates by a measurement technique that depends on eddy currents in the metal plate. The transmitting coil generates a time-varying magnetic field applied to the metal plate. In response, eddy currents are generated in the metal plate as a result of the applied time-varying magnetic field. The eddy currents can be detected by a receiving coil disposed at a predetermined distance from the metal plate. A voltage signal is induced in the receiving coil by the time derivative of the magnetic field generated by the eddy currents in the workpiece. The voltage signal is amplified, for example, as is often the case in a data acquisition system, and processed to generate an acquisition signal used to determine the characteristics of the metal plate.

[0020] The time-varying magnetic field applied is preferably generated by interrupting a bias DC current in the transmitting coil. Thus, a pulsed magnetic field is applied, and the receiving coil measures the magnetic field generated by the eddy currents in response to the pulse, preferably in response to the negative edge of the pulse when the magnetic field is removed.

[0021] Determining the characteristics may be performed, for example, by a theoretical model or by using an empirically determined model that correlates the time dependence of eddy current decay with the metal plate characteristics. There are various methods known per se for extracting such characteristics from the metal plate based on induction measurements, such as magnetic transient measurements.

[0022] Advantageously, the resonance frequency of the correction coil may be higher than the frequency of the transient magnetic field measured from the metal plate in response to the applied magnetic field. Thereby, interference between the measurement by the inspection coil and the measurement by the correction coil can be reduced. The resonance frequency of the correction coil having respective capacitors may be higher than the maximum frequency transiently present measured from the metal plate.

[0023] Preferably, the resonance frequency of the resonance circuit including the correction coil can be at least twice the frequency of the transient magnetic field measured from the metal plate in response to the applied magnetic field.

[0024] Furthermore, the resonance frequency of the resonance circuit including the correction coil can be at least three times the frequency of the transient magnetic field measured from the metal plate in response to the applied magnetic field.

[0025] Furthermore, the resonance frequency of the resonance circuit including the correction coil can be at least four times the frequency of the transient magnetic field measured from the metal plate in response to the applied magnetic field.

[0026] Furthermore, the resonance frequency of the resonance circuit including the correction coil can be at least five times the frequency of the transient magnetic field measured from the metal plate in response to the applied magnetic field.

[0027] The frequency of the transient magnetic field measured from the metal plate depends on the frequency of the time-varying magnetic field applied. Therefore, the resonance circuit can be adapted with respect to the frequency of the time-varying magnetic field applied in order to ensure a desired relationship between the resonance frequency of the resonance circuit including the correction coil and the frequency of the transient magnetic field.

[0028] In order to further reduce coupling and crosstalk, in an embodiment, the correction coil can be spatially separated from the transmission coil and the reception coil and disposed outside the windings of the transmission coil and the reception coil. In other words, the correction coil is disposed outside the inner region surrounded by the windings of the inspection coil.

[0029] The correction coil is disposed in a region that does not substantially shield the magnetic field generated and captured by the inspection coil, thereby minimizing the interaction between the inspection coil and the correction coil.

[0030] In an embodiment, the correction coil can be substantially smaller than the transmission coil and the reception coil. Thereby, the coupling and crosstalk between the correction coil and the inspection coil can be further reduced. Furthermore, the resolution of the measurement of the spatial displacement can be improved by enabling more local measurements using a smaller correction coil.

[0031] Furthermore, the correction coil can resonate only when the transmission coil is in the excitation phase of applying a magnetic field to the metal plate. Thereby, interference between the measurement performed by the inspection coil and the measurement performed by the correction coil is advantageously avoided.

[0032] In an embodiment, the spatial displacement of the metal plate from the reference plane can be detected by comparing frequency shifts with each other. For example, by comparing the relative shifts between two or more correction coils, the degree of inclination of the metal plate can be detected. By analyzing the frequency shifts of three or more resonance correction coils, the curvature of the metal plate can be detected. The frequency shifts are preferably acquired at the same time point in order to provide an instantaneous image of the degree of inclination and / or curvature of the metal plate.

[0033] In an embodiment, the transmission coil and the reception coil can be planar coils. The planar inspection coils can share the same plane.

[0034] In an embodiment, the correction coil can be a planar coil. The planar correction coils can share the same plane.

[0035] The planar correction coil and the planar inspection coil can share the same plane.

[0036] The planar coil provides a cost-effective measuring device that enables, for example, planar design on a printed circuit board.

[0037] In an embodiment, the measuring device can include a carrier substrate for supporting the inspection coil and the carrier coil. The carrier substrate can be a printed circuit board.

[0038] In an embodiment, the measuring device can be connectable to a control unit configured to control the supply of an electrical signal to the correction coil at the resonance frequency, detect a shift in the resonance frequency in the presence of the metal plate, and derive a spatial displacement based on the detected shift.

[0039] According to a second aspect of the present invention, there is provided a rolling mill comprising at least two work rolls configured to process a metal sheet therebetween and a measuring device according to the embodiments discussed herein.

[0040] Further effects and features of the second aspect of the present invention are substantially the same as those described above in relation to the first aspect of the present invention.

[0041] According to a third aspect of the present invention, there is provided a method for detecting a spatial displacement of a metal sheet processed in a rolling mill from a reference plane, the metal sheet being subjected to measurements by a transmitting coil and a receiving coil configured to perform a transient magnetic field measurement for determining at least one characteristic of the metal sheet, the method comprising resonating each of a set of correction coils connected to respective capacitors at respective resonance frequencies and detecting a shift in the resonance frequency of each correction coil in the presence of the metal sheet, whereby a spatial displacement can be derived from the shift in the resonance frequency.

[0042] In an embodiment, the method may include resonating the correction coils only when the transmitting coil is not applying a time-varying magnetic field to the metal sheet in order to perform the transient magnetic field measurement. In other words, the correction coils resonate only in the absence of the time-varying magnetic field applied by the transmitting coil. Thus, the correction coils are advantageously resonated within a time window to perform a correction measurement when the transmitting coil is not applying a time-varying magnetic field and the receiving coil is not measuring the eddy current response from the metal sheet. The correction coils may be resonated, for example, before triggering a metal sheet inspection measurement performed by an inspection coil or after a modified magnetic field has been removed. This can reduce or avoid interference between the measurements performed by the transmitting and receiving coils and the measurement of the spatial displacement performed by the correction coils.

[0043] Further effects and features of the third aspect of the present invention are substantially the same as those described above in relation to the first and second aspects of the present invention.

[0044] A control unit is further provided, and the control unit controls the supply of an electrical signal to a correction coil at a resonance frequency. The correction coil is arranged to detect a spatial displacement of a metal plate from a reference plane. Each correction coil can be connected to a capacitor, forms a respective resonance circuit having a resonance frequency, and the correction coil is configured to resonate at each resonance frequency. A shift in the resonance frequency in the presence of the metal plate can be detected, and a spatial displacement can be derived from the shift in the resonance frequency. The control unit is configured to detect a shift in the resonance frequency in the presence of the metal plate and derive a spatial displacement based on the detected shift.

[0045] Further features and advantages of the present invention will become apparent upon consideration of the appended claims and the following description. Those skilled in the art will understand that, without departing from the scope of the present invention, different features of the present invention can be combined to create embodiments other than those described below.

[0046] These and other aspects of the present invention will be described in more detail with reference to the accompanying drawings that illustrate exemplary embodiments of the present invention.

Brief Description of the Drawings

[0047]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Figure 5

Embodiments for Carrying Out the Invention

[0048] In the detailed description of the present invention, various embodiments of the present invention are described herein with reference to specific implementation forms. When describing the embodiments, specific terms are used for clarification. However, the present invention is not intended to be limited to such specific terms selected. Specific exemplary embodiments are described, but it should be understood that this is done only for illustrative purposes. Those skilled in the art will recognize that other components and configurations can be used without departing from the scope of the present invention.

[0049] FIG. 1 conceptually shows a rolling mill 100 equipped with a set of work rolls 102a and 102b adapted to process a metal plate 104. The work rolls 102a - b rotate while the metal plate 104 is being fed between the work rolls 102a - b. As will be understood by those skilled in the art, the work rolls 102a - b reduce the thickness of the workpiece. A cross - section of the metal plate 104 is shown in FIG. 1.

[0050] When the metal plate 104 is being processed in the rolling mill 100, it is desirable to accurately measure the characteristics of the moving metal plate 104. For this purpose, a measuring device 106 is provided. The measuring device 106 includes an inspection coil set including a transmitting coil 108 and a receiving coil 110. The transmitting coil 108 is configured to apply a time - varying magnetic field to the metal plate 104. The receiving coil 110 is configured to detect a transient magnetic field generated by eddy currents in the metal plate 104 that occur in response to the applied magnetic field. The characteristics of the metal plate are derivable from the transient magnetic field. Such characteristics can be the distance d to the sensor head 112, the resistivity of the metal plate 104, and the thickness t of the metal plate 104.

[0051] The metal plate 104 moves on the production line from the left to the right in FIG. 1, that is, it turns from the left to the right, so it is not necessarily parallel to the sensor head 112. The curvature and inclination of the metal plate with respect to the sensor head affect the reading values, resulting in incorrect estimated values of distance, resistivity, and thickness. To address this problem, the measuring device 106 includes a set of correction coils including correction coils 116 and 118 in this exemplary embodiment. The correction coils 116 and 118 are configured to detect the spatial displacement of the metal plate 104 from the reference plane. Each of the correction coils 116, 118 can be connected to a capacitor, forming respective resonant circuits having resonant frequencies. The measuring device 106 may include more than two correction coils, such as, for example, three or more correction coils, as will become apparent with reference to subsequent drawings. Only two correction coils 116, 118 are shown in FIG. 1.

[0052] As will be further explained, the correction coils 116, 118 are configured to resonate at their respective resonant frequencies, the shift of the resonant frequency in the presence of the metal plate 104 can be detected, and the spatial displacement can be derived from the shift of the resonant frequency. Preferably, the measuring device 106 includes at least three correction coils.

[0053] Generally, the measuring device 106 is adapted to measure the characteristics of the metal plate by eddy current technology. Thus, the transmitting coil 108 is controlled, for example, by the control unit 120 to receive current from a current source or a voltage source and generate and apply a time-varying magnetic field, i.e., a pulsed magnetic field, into the metal plate 104. The receiving coil 110 detects the magnetic field generated by the eddy current in the metal plate 104. The control unit 120 can receive a signal indicating the detected magnetic field and derive the characteristics of the metal plate 104 from the signal.

[0054] The measuring device 106 is arranged here downstream of the work rolls 102a - b. However, of course, the measuring device 106 may be arranged at other locations, such as upstream of the work rolls 102a - b.

[0055] The control unit 120 is connected to the measuring device 106 in a wireless or wired communication-capable manner so as to be able to receive data signals from the measuring device 106. In some embodiments, the control unit 120 is configured to control the supply of an electrical signal to a correction coil at a resonance frequency, detect a shift in the resonance frequency in the presence of a metal plate, and derive a spatial displacement based on the detected shift.

[0056] FIG. 2 conceptually shows a measuring device 106 according to an exemplary embodiment. The measuring device 106 includes a transmitting coil 108 and a receiving coil 110, which are concentrically arranged here on a carrier substrate 126 that supports the coils 108, 110. Further, a set of correction coils 116, 118, 122, 124 is also arranged on the substrate 126. In other words, this embodiment includes a carrier substrate 126 for supporting the inspection coils 108, 110 and the correction coils 116, 118, 122, 124. Further, the carrier substrate 126 can support an on-chip capacitor (not shown) that forms a resonance circuit together with the correction coils 116, 118, 122, 124. A capacitor that forms a resonance circuit together with the correction coils may be included in the measuring device 106.

[0057] Also, in this embodiment, the transmitting coil 108 and the receiving coil 110 are planar coils. Further, the correction coils 116, 118, 122, 124 are also planar coils. A planar coil generally has windings on a plane, and its height is a relatively "flat" coil consisting of a single layer or several layers of wires.

[0058] Preferably, the correction coils are arranged so as to be substantially separated from the inspection coils. In the embodiment shown in FIG. 2, this is achieved by arranging the correction coils 116, 118, 122, 124 as far as possible from the inspection coils 108 and 110. The inspection coils 108 and 110 are arranged at the center of the carrier substrate 126, and the correction coils 116, 118, 122, 124 are arranged on the end side of the substrate, here near the corners of the substrate 126.

[0059] Furthermore, the correction coils 116, 118, 122, 124 are spatially separated from the transmission coil 108 and the reception coil 110, and are disposed outside the windings of the transmission coil and the reception coil. In other words, the correction coils 116, 118, 122, 124 are not disposed inside the core surrounded by the windings of the transmission coil 108 and the reception coil 110. In some possible embodiments, the correction coils 116, 118, 122, 124 may be disposed in the same plane that can be parallel to or function as a reference plane. In this exemplary embodiment, the correction coils 116, 118, 122, 124, the transmission coil 108, and the reception coil 110 are disposed in the same plane. This plane can be parallel to the reference plane in which the spatial displacement of the metal plate is detected. The transmission coil generates a time-varying magnetic field along the main axis that is the normal to the plane of the substrate 126 and the normal to the reference plane.

[0060] It should be understood that other configurations for separating the correction coil from the inspection coil are also conceivable. For example, the correction coil may be disposed on a separate carrier substrate, which enables the correction coil to be disposed further away from the inspection coil with greater freedom compared to the case where the correction coil is provided on the same carrier substrate. However, by using a single carrier substrate as shown in FIG. 2, an integrated measuring device is obtained that is provided as a single component that can be easily installed.

[0061] Referring further to FIG. 2, the correction coils 116, 118, 122, 124 are substantially smaller than the transmission coil 108 and the reception coil 110. Here, the size refers to the outer diameter of the coil.

[0062] The measurement method of the correction coil depends on measuring the shift of the resonance frequency. FIG. 3 schematically shows an equivalent circuit of such a resonance circuit 300.

[0063] The circuit 300 is connected to a voltage / current source 302 for driving the circuit 300 at its resonant frequency, and a voltage sensor measures the voltage V across both ends of the circuit 300. The power source 302 can be an AC power source. The circuit 300 is represented by an inductor Lc, which is the inductance of the correction coil when there is no metal plate near the correction coil, and a capacitor having a capacitance C connected in parallel thereto. In this case, the resonant frequency is proportional to 1 / √(C×Lc). Therefore, during operation, the resonant circuit 300 provided with the correction coil Lc connected to the capacitor C is driven at its resonant frequency 1 / √(C×Lc). The capacitor may be provided on a carrier substrate in the form of a chip capacitor, such as an NP0 chip capacitor.

[0064] The correction coil and / or the capacitor are designed such that the resonant frequency of the resonant circuit is higher than the frequency of the transient magnetic field measured from the metal plate in response to the applied magnetic field generated by the transmission coil. The resonant frequency of the resonant circuit is at least twice the frequency of the transient magnetic field measured from the metal plate in response to the applied magnetic field.

[0065] When a metal plate is present near the correction coil, an additional inductance Lm (not shown) contributes to the inductance in the circuit. This is the inductance contribution of the metal plate, for example, the metal plate 104 shown in FIG. 1. When the metal plate is completely flat, i.e., when both the curvature and the inclination are zero, the contribution inductance Lm is equal for all correction coils, and thus the frequency shift of each correction coil is also substantially equal. However, since the metal plate often has a certain degree of curvature or inclination, the contribution inductance Lm is not equal for all correction coils. The overall difference in inductance causes a shift in the resonant frequency of each correction coil, which is generally proportional to 1 / √(C×Lc’). Here, Lc’ is the combined contribution inductance from the metal plate Lm and the correction coil Lc. Generally, Lc’ < Lc.

[0066] As conceptually described with reference to FIGS. 4A to 4D, the spatial displacement of the metal plate from the reference plane can be detected by comparing the resonance frequency shifts with each other.

[0067] FIG. 4A conceptually shows a side view of the metal plate 104 inclined with respect to the reference plane 400. The metal plate 104 is shown here without curvature for clarity in FIG. 4A. The correction coils 116 and 118 are shown as being disposed within the reference plane 400, although the reference plane may be elsewhere. The inclined metal plate 104 is closer to the reference plane 400 at one end 104a than at the other end 104b. When the resonance frequency shift of coil 118 is compared with the resonance frequency shift of coil 116, the relative shift therebetween, for example, the ratio of the shift of coil 116 to the shift of coil 118 or the difference between the shifts, provides an indication of the degree of inclination of the metal plate 104.

[0068] FIG. 4A shows a side view in which the coils 116 and 118 of FIG. 2 are represented. It should be noted that a similar explanation applies when another side view is considered, for example, when a side view showing the correction coils 118 and 124 instead is presented as shown in FIG. 4B. Here, the inclined metal plate 104 is closer to the reference plane 400 at one end 104c than at the other end 104d. When the resonance frequency shift of coil 118 is compared with the resonance frequency shift of coil 124, the relative shift therebetween provides an indication of the degree of inclination of the metal plate 104.

[0069] FIG. 4C conceptually shows a cross-sectional side view of the metal plate 104 having a curvature. In FIG. 4C, three correction coils 116, 118, 122 are conceptually shown to be within the reference plane 400. To determine the curvature of the metal plate, the resonance shift of each of the three coils 116, 122, and 118 is determined. The curvature can be calculated from the three resonance shifts. For example, each of the resonance shifts indicates the respective spatial displacements d1, d2, d3 between the plate and the reference plane 400 at the positions of the correction coils. The three spatial displacements d1, d2, d3 or the resonance shifts indicating them can be used to determine the local curvature of the metal plate. This is similar to determining the curvature of a path, and to determine the curvature, at least three points on the path need to be known.

[0070] FIG. 4D conceptually shows another cross-sectional side view of the metal plate 104 having a curvature, considering four correction coils 116, 118, 122, 124 here conceptually shown. As described above, the curvature of the metal plate 104 can be determined from the resonance shift of each of the correction coils 116, 118, 122, and 118. Each of the resonance shifts indicates the respective spatial displacements d3, d4, d5, and d6 between the metal plate 104 and the reference plane 400 at the positions of the respective correction coils. The four spatial displacements d3, d4, d5, and d6 or the resonance shifts indicating them can be used to determine the local curvature of the metal plate.

[0071] As described above, the spatial displacement of the metal plate is at least one of the curvature of the metal plate and the inclination of the metal plate 104.

[0072] The relative shift of the resonance frequencies between two or more resonance circuits each including a correction coil can be compared with pre-stored data associating curvature data and inclination data with the resonance frequency shift. For example, a look-up table can include a number of resonance frequency shift data pairs with curvature data and inclination data, whereby the control unit can find matching or at least approximately matching curvature data and inclination data based on the measured frequency shift.

[0073] Another possible approach for obtaining curvature data and gradient data is to use an empirical model that builds a model using a large amount of resonance frequency shift data as well as corresponding curvature data and gradient data.

[0074] Another possible approach for obtaining curvature data and gradient data is by means of a machine learning model instructed with respect to pre-learned data, resonance frequency shift data, as well as corresponding curvature data and gradient data.

[0075] A theoretical model for obtaining curvature data and gradient data is also conceivable.

[0076] Furthermore, it is understood that the curvature and gradient can be determined by a combination of two or more of the above-described methods including a look-up table, an empirical model, a theoretical model, and a machine learning method.

[0077] When the curvature and / or gradient of the metal plate is determined, these can be used to correct the characteristics of the metal plate measured by an inspection coil by a method known per se.

[0078] FIG. 5 is a flowchart of method steps according to an embodiment of the present invention. The method is a method for detecting a spatial displacement from a reference plane of a metal plate processed in a rolling mill. The metal plate is subjected to measurements by a transmitting coil and a receiving coil configured to perform a transient magnetic field measurement for determining at least one characteristic of the metal plate.

[0079] The method includes, in step S102, resonating each of a set of correction coils connected to respective capacitors at respective resonance frequencies.

[0080] This method further includes step S104 which includes detecting the shift of the resonance frequency in the presence of the metal plate for each correction coil, whereby in step S106, the spatial displacement can be derived from the shift of the resonance frequency.

[0081] Preferably, step S102 of resonating the correction coil is only executed when the transmitting coil is not applying a time-varying magnetic field to the metal plate to perform the transient magnetic field measurement. Therefore, the correction coil is resonated before or after the magnetic field is changed.

[0082] The control unit may include a microprocessor, a microcontroller, a programmable digital signal processor, or another programmable device. In addition to or instead of this, the control unit may include an application-specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. When the control unit includes a programmable device such as the above-described microprocessor, microcontroller, or programmable digital signal processor, the processor may further include computer-executable code for controlling the operation of the programmable device.

[0083] The communication between the devices, control units, or other modules described herein may be wireless or wired so as to be appropriate and to implement an appropriate protocol in a particular case.

[0084] Although the present invention has been described with reference to its specific exemplary embodiments, many different variations, modifications, etc. will be apparent to those skilled in the art.

[0085] In addition, variations to the disclosed embodiments will be apparent and attainable by one skilled in the art from a study of the drawings, the disclosure, and the appended claims. In the claims, the term "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be advantageously used.

Claims

1. A measuring device (106) for measuring the properties of a metal sheet (104) processed within a rolling mill (100), the measuring device comprising: An inspection coil set including a transmitting coil (108) and a receiving coil (110), the transmitting coil being configured to apply a time-varying magnetic field to the metal sheet, and the receiving coil being configured to detect a transient magnetic field generated from the metal sheet in response to the applied time-varying magnetic field, wherein at least one property of the metal sheet is derivable from the transient magnetic field; and an inspection coil set; A correction coil set (116, 118, 122, 124) for detecting a spatial displacement of the metal sheet from a reference plane, each correction coil being connected to a capacitor to form a respective resonant circuit having a resonant frequency; and a correction coil set (116, 118, 122, 124); comprising The correction coils are configured to resonate at their respective resonant frequencies, and a shift in the resonant frequency in the presence of the metal sheet is detectable, and the spatial displacement is derivable from the shift in the resonant frequency, measuring device.

2. The correction coils are arranged to be substantially separated from the inspection coil set, The measuring device according to claim 1.

3. The resonant frequency of the resonant circuit is higher than the frequency of the transient magnetic field measured from the metal sheet in response to the applied magnetic field, The measuring device according to claim 1 or 2.

4. The resonant frequency of the correction coil is at least twice the frequency of the transient magnetic field measured from the metal sheet in response to the applied magnetic field, The measuring device according to claim 3.

5. The correction coils are spatially separated from the transmitting coil and the receiving coil and are arranged outside the windings of the transmitting coil and the receiving coil, The measuring device according to any one of claims 1 to 4.

6. The correction coils are substantially smaller than the transmitting coil and the receiving coil, The measuring device according to any one of claims 1 to 5.

7. The spatial displacement of the metal sheet is at least one of the curvature of the metal sheet and the inclination of the metal sheet, The measuring device according to any one of claims 1 to 6.

8. The spatial displacement of the metal sheet from the reference plane is detected by comparing resonant frequency shifts with each other, The measuring device according to any one of claims 1 to 7.

9. The transmitting coil and the receiving coil are planar coils. The measuring device according to any one of claims 1 to 8.

10. The correction coil is a planar coil. The measuring device according to any one of claims 1 to 9.

11. The measuring device includes a carrier substrate (126) for supporting the inspection coil set and the correction coil set. The measuring device according to any one of claims 1 to 10.

12. The measuring device is connectable to a control unit (120), and the control unit (120) controls the supply of an electrical signal to the correction coil at the resonance frequency, detects the shift of the resonance frequency in the presence of the metal plate, derives a spatial displacement based on the detected shift. It is configured as follows. The measuring device according to any one of claims 1 to 11.

13. At least two work rolls (102a, 102b) configured to process a metal plate therebetween, The measuring device according to any one of claims 1 to 12, A rolling mill (100) provided with.

14. A method for detecting a spatial displacement from a reference plane of a metal plate processed in a rolling mill, the metal plate being subjected to measurement by a transmitting coil and a receiving coil configured to perform a transient magnetic field measurement for obtaining at least one characteristic of the metal plate, the method comprising: Resonating each of a set of correction coils connected to respective capacitors at respective resonance frequencies (S102); Detecting a shift in the resonance frequency in the presence of the metal plate for each correction coil, whereby a spatial displacement can be derived from the shift in the resonance frequency (S106); A method including.

15. The method includes resonating the correction coil only when the transmitting coil is not applying a time-varying magnetic field to the metal plate in order to perform the transient magnetic field measurement. The method according to claim 14.

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