Measuring roller

Abstract

The invention relates to a measuring roller having a contact roller for being brought into contact with a band (20), in particular a metal band. On the contact roller, at least one sensor element is arranged for detecting a physical measurement variable of the deflected band (20) in the contact region between the contact roller (12) and the band (20). In order to develop such a known measuring roller having at least one sensor, and a known method for generating and evaluating a measurement signal of the sensor element, such that the quality of the sensor signal is improved and the physical measurement variable of the deflected band it represents can be determined more accurately, the invention proposes that the sensor strip (14) is designed as a single sensor and is arranged helically on the surface of the contact roller (12).

Description

[0001] measuring roller

[0002] The invention relates to a measuring roller for contact with a strip, in particular a metal strip, comprising a contact roller and at least one sensor element arranged on the surface of the contact roller for detecting a measured value of the strip in the contact area between the contact roller and the strip. Furthermore, the invention relates to a method for generating and evaluating a measurement signal based on a sensor signal generated by the sensor element.

[0003] In the prior art, for example, German patent application DE 10 2018 218 300 A1 discloses a sensor layer system for detecting forces, temperatures, and strains on components. For this purpose, the layer system is applied, for example, to the surface of tools or machine elements. The sensor layer system generates at least one sensor signal, which is evaluated using an evaluation unit.

[0004] A similar sensor system is disclosed in the paper "Smart Factory - Sensor Technology for Production" by the Fraunhofer Institute for Surface Engineering and Thin Films IST, Bienroder Weg 54E, 38108 Braunschweig, Germany. This sensor system is also used for the local measurement of pressure and temperature distributions on the surface of tools, for example. The sensor system is a multifunctional thin-film system designed for direct contact with a workpiece to be formed. It allows for precise measurement of pressure and temperature distributions, so that the sheet metal behavior in a sheet metal bending and drawing process can be precisely determined. Furthermore, the German laid-open specifications DE 10 2021 002 661 A1 and DE 10 2021 005 558 B3 disclose a measuring roller for determining a property of a strip-shaped material guided over the measuring roller.For this purpose, force sensors are mounted on the circumferential surface of a measuring roller body, and the measuring roller body with the force sensors is partially or completely coated with a layer of coating. The measuring roller is also designed, in particular, to determine the strip edge position of a strip guided over the roller.

[0005] In addition, measuring systems in contact rollers for measuring the tensile stress distribution within a strip guided over the measuring roller are known. However, these measuring systems only have a low resolution across the circumference of the roller and thus across the length of the strip. Measuring rollers in their current design have sensors that are usually arranged at four positions around the circumference. Sometimes only one sensor is installed per position. A complete measurement across the width is only possible after a complete rotation. This leads to low temporal resolution, particularly at low speeds. Control systems that operate on the basis of these measurements encounter considerable problems in these cases. Determining the measured values ​​with partially covered sensors at the strip edges is not possible without knowing the position of the strip edges. Installing the sensors inside the contact roller results in an undefined sensitivity range on the surface.This effect leads to incorrect calculations of strip tensile stresses at the edges of the strip. Installing the sensors within the contact rollers requires significant machining effort. The sensor technology requires very high manufacturing quality in the production of the measuring rollers. These requirements limit the choice of materials for the manufacturing of the measuring rollers.

[0006] Finally, measuring rollers with temperature sensors for the strip guided over the measuring roller are known. Due to the only brief contact with the strip, an absolute measurement of the strip temperature cannot be achieved with these measuring rollers. Instead, additional measuring systems are required to measure the absolute temperature. Only with the help of this additional measurement can an absolute temperature profile be calculated. However, the separate temperature measurement systems require additional installation space and have several disadvantages. Contact thermometers are brought into contact with the moving strip to measure the temperature. This leads to a considerable risk of damage to the surface of the guided strip. Furthermore, the temperature sensor can be destroyed if the strip breaks. Infrared thermometers can be significantly affected by steam and dust in the beam path.Determining the emission coefficient correctly is very difficult, if not impossible, especially for metal strip surfaces. This makes temperature measurements inaccurate or even incorrect.

[0007] The invention is based on the object of developing a known measuring roller with at least one sensor element and a known method for generating and evaluating a measuring signal of the sensor element of the measuring roller in such a way that the quality of the sensor signal generated by the sensor element is improved and the physical quantity or property of the strip guided over the measuring roller represented thereby can be determined more precisely.

[0008] This object is achieved with respect to the measuring roller by the subject matter of patent claim 1. Accordingly, the measuring roller is characterized in that the sensor strip is designed as a single sensor and is arranged spirally on the surface of the contact roller.

[0009] This inventive design of the sensor elements using thin-film technology advantageously enables very close contact between the sensor element and the strip, in particular a metal strip. Contact can be established when the strip is deflected around the measuring roller or only when the measuring roller comes into tangential contact with the strip. This, in turn, enables or ensures precise measurement of the physical parameter detected by the sensor element with respect to the strip in the contact area between the measuring roller and the strip. Thin-film sensor technology with DiaForce® is preferably used for the measuring roller according to the invention. This technology advantageously enables flexible design of the sensor elements with regard to their geometry and arrangement on the surface of the measuring roller.The integration of the sensor elements into the coating of the measuring roller enables direct, high-resolution measurement of parameters related to the strip and, derived from this, the determination of other physical parameters or properties of the strip. Thin-film technology also simplifies the design and thus the production of the sensor elements on the surface of the measuring roller. Specifically, the use of thin-film technology can significantly reduce the number of channels required for signal transmission compared to the state of the art.

[0010] The claimed sensor strip comprises a single sensor per sensor strip. This means that the sensor strip according to the invention is not formed by several or a plurality of sensors.

[0011] The measurement results of the claimed spirally laid sensor strip advantageously enable a variety of possible conclusions to be drawn regarding the condition and quality of the strip guided over the measuring roller, as will become apparent from the exemplary embodiments described below. In particular, the measurement results allow a conclusion to be drawn regarding the flatness of the strip.

[0012] The stated object of the invention is achieved with respect to the method according to the invention by the method according to claim 18. The advantages of this method for generating and evaluating a measurement signal from a sensor element of the measuring roller correspond to the advantages previously mentioned with reference to the claimed measuring roller. Advantageous embodiments of the measuring roller according to the invention and of the method according to the invention are the subject of the dependent claims.

[0013] The description includes 18 figures, of which

[0014] Figure 1 shows the structure of a measuring roller according to the invention;

[0015] Figure 2 shows the layer structure of a sensor element in thin-film technology known from the prior art;

[0016] Figure 3 shows a first embodiment of the arrangement of a spiral-shaped sensor element on the surface of a contact roller as the base body of the measuring roller;

[0017] Figure 4 shows a second embodiment of the arrangement of spiral sensor elements on the surface of the contact roller;

[0018] Figure 5 shows a third embodiment of the arrangement of spiral sensor elements on the surface of the contact roller;

[0019] Figure 6 shows a fourth embodiment of the arrangement of spiral sensor elements on the surface of the contact roller;

[0020] Figure 7 shows a fifth embodiment of the arrangement of a

[0021] Sensor element on the surface of the contact roller;

[0022] Figure 8 shows a sixth embodiment of the arrangement of a

[0023] Sensor element on the surface of the contact roller;

[0024] Figure 9 shows the interconnection of the sensor elements according to Figure 8 in a Wheatstone bridge; Figure 10 shows a seventh embodiment of the arrangement of two spiral-shaped sensor elements on the surface of the contact roller, which are aligned along a common alignment line, and wherein one of the sensor elements serves as a reference or reference variable;

[0025] Figure 11 shows a rectangular measurement signal for determining the width positions of the edges of the strip;

[0026] Figure 12 shows the sequence of the method according to the invention for the more precise determination of the width positions of the edges of the strip;

[0027] Fig. 13 a normalized edge slope for an improved / more accurate determination of the width position of the edges of the strip;

[0028] Figure 14 shows an eighth embodiment of the arrangement of sensor elements on the surface of the contact roller;

[0029] Figure 15 shows a first embodiment of a preferably full-surface covering of the surface of the contact roller with sensor elements;

[0030] Figure 16 shows a second embodiment for the preferably full-surface coverage of the surface of the contact roller with sensor elements;

[0031] Figure 17 shows the arrangement of the sensor elements according to Fig. 16 with increased distances in the circumferential direction; and

[0032] Figure 18 shows the signal of a sensor element according to Figure 17 over one revolution. The invention is described in detail below with reference to the figures mentioned in the form of exemplary embodiments. In all figures, identical technical elements are designated by identical reference numerals. All Figures 3 to 10 and 14 to 17 each show a developed view of the surface of a barrel of a measuring roller.

[0033] Figure 1 shows the structure of the measuring roller 10 according to the invention. The measuring roller serves to contact a strip 20, in particular a metal strip, during a forming process, such as occurs in a rolling mill, or during a treatment process, such as occurs in a strip treatment plant. The measuring roller 10 essentially consists of a contact roller 12, which is mounted so as to be rotatable about a rotational axis. At least one sensor element 14 is arranged on the surface of the contact roller 12 for detecting at least one physical measurement variable of the strip in the contact area between the measuring roller 10 and the strip 20 and for generating a corresponding sensor signal. The sensor signal is typically initially time-dependent. According to the invention, the sensor element 14 is formed flatly using thin-film technology and is at least partially part of an outer coating on the surface of the contact roller 12.

[0034] In the invention, a distinction must be made between physical measured variables of the strip 20, which can actually be detected by the sensor element 14, and physical variables or properties of the strip 20 that can be derived therefrom and are determined with the aid of the evaluation device 19. The measured variables that can actually be detected by the sensor elements include, for example, the temperature of the strip 20 and / or the pressure or force with which the strip 20 is pressed onto the contact roller 12, in each case in the contact area between the strip and the measuring roller 10. The physical variables or properties of the strip 20 that can only be determined with the aid of the evaluation device by evaluating the at least one measurement signal include the strip tension in the strip 20, the distribution of the strip tension across the width of the strip, the width of the strip, the position of the strip orthe strip edges on the surface of the contact roller 12, in particular in the width direction of the contact roller, the surface quality of the strip, for example the surface roughness, the strength of the strip and / or the wrap angle of the strip 20 around the contact roller 12, in each case in the contact area between the strip 20 and the measuring roller 10.

[0035] Associated with the measuring roller 10 is an angle sensor 17 for detecting the respective current rotational position of the contact roller 12 or the measuring roller 10 and a conversion unit 18 for converting the rotational position, taking into account the respective arrangement and design of the sensor elements 14 on the contact roller, into a position in the width direction of the contact roller 12 or the belt 20. A value of the respective sensor signal can be assigned to this width position for generating a width-dependent measurement signal S(b).

[0036] Finally, an evaluation unit 19 is assigned to the measuring roller for evaluating the at least one measuring signal with regard to various measured variables or physical properties that the belt has in the contact area with the measuring roller 10.

[0037] Figure 2 shows an example structure for the sensor element 14 using thin-film technology, specifically according to the DiaForce® brand. This technology enables a highly flexible design of pressure-sensitive sensor elements, as shown in the following figures. Lithography is preferably used to create the geometric shape of the sensor elements.

[0038] The sensor element 14 is preferably designed in the form of a sensor strip and, as such, is preferably arranged spirally on the surface of the contact roller. In order to enable high-resolution measurement in the width direction in this exemplary embodiment, the sensor strip is designed with only a small spread in the width direction. The spread is preferably just wide enough to allow a sensor signal sufficiently clear for a measuring task to be generated and evaluated. A width of 1 to 5 mm perpendicular to the longitudinal extent of the sensor strip is preferably desirable. With the spiral arrangement of the sensor strip on the contact roller, the rotational position of the contact roller 12 or the measuring roller 10 can be detected at any time with the aid of the aforementioned angle sensor 17.The rotational position (angular position) can then be converted into a width position using the conversion unit 18, taking into account the spiral arrangement of the sensor strip on the contact roller. The value of the sensor signal measured by the sensor strip at this time can then be assigned to the width position using the conversion unit 18. This process is repeated several times, preferably continuously, to generate the width-dependent measurement signal S(b).

[0039] Figure 3 shows a developed view of the surface of the measuring roller 10 with a sensor area arranged on the surface, formed by the sensor element 14 in the form of a sensor strip. Additionally, Figure 3 shows the contact area between the measuring roller 10 and the belt 20 at two different rotational positions, each represented as a horizontal line. At rotational position 1, the currently measured value of the sensor signal is assigned to width position 1, and at rotational position 2, correspondingly to width position 2. If the measured values ​​and the associated width positions are continuously recorded, a high-resolution measurement across the width is obtained after completion of one rotation in the form of the width-dependent measurement signal S(b). The width resolution Ab is derived from the formula: where a is the wrap angle of the belt 20 upon contact with the measuring roller 12, specified in degrees; bz is the width in the direction of the roller's longitudinal axis that is scanned by the sensor element during one revolution; or: the width of the projection of the spiral sensor strip 14 onto the longitudinal axis of the contact roller 12; bsF is the width of the sensor element in the direction transverse to the longitudinal direction of the spiral.

[0040] Formula 1 and all other formulas of the present description apply only to the sensor element 14 designed as a spirally laid sensor strip.

[0041] For a wrap angle of 6°, a width b z of 2400mm and a width ÖSF of 5 mm perpendicular to the longitudinal axis of the spiral sensor strip, the width resolution Ab is:

[0042] If the spiral sensor element is designed as a pressure sensor, a high-resolution measurement of the specific belt tension across the width is obtained by calibrating the measuring signal to the belt tension according to the following formula: f B (b) = S(b) * k(b) (2) b: Bandwidth position f B (b): specific belt tension across width

[0043] S(b): Measurement signal over width k(b): Calibration factor over width

[0044] The specific strip tension is the strip tension relative to the width. By integrating the strip tension curve over the strip width, the process parameter strip tension FB, which is important in practice, is obtained.

[0045] FB = I f B (b) db

[0046] The measured specific belt tensile force FB across the width can be converted into an extension £ of the belt in the running direction at the width position b of the belt 20 for linear elastic belts 20 using the E-modulus and the thickness of the belt according to the following formula h: thickness of the strip

[0047] E: Young's modulus fß(b): specific strip tensile force across width

[0048] This measurement value corresponds to the process value “flatness”, which is important for a rolling process of metallic strips.

[0049] Figure 4 shows a second exemplary embodiment for the arrangement of the sensor strips 14 on the contact roller 12, wherein a further sensor strip 14-2 is arranged on the surface of the measuring roller, parallel to the first sensor strip 14-1, also in a spiral shape. This second sensor strip can shorten the evaluation of the sensor or measurement signals. In Figure 4, the second spiral-shaped sensor strip 14-2 is arranged on the circumference of the measuring roller 10, for example, offset by 180° from the first sensor strip, so that after just half a revolution the measurement signal is present across the entire width of the measuring roller or belt 20. This arrangement thus improves the dynamics of the measurement. Another possible application of such an arrangement is to improve the signal quality through further measurements and statistical evaluation, for example by averaging.In Figure 4, the two sensor strips each extend over the entire circumference of the contact roller 12 or the measuring roller 10. This is not mandatory, i.e., the sensor strip can also extend only over part of the circumference; however, in this case, the measurement signal is not present over the entire width of the contact roller or the belt 20.

[0050] Figure 5 shows a further advantageous embodiment of two sensor strips 14-1, 14-2, which here also each extend over the entire circumference of the contact roller 12, but which are limited to only half the roller width in the width direction of the contact roller. This means that their respective pitch is twice as great as in the embodiment according to Figure 4. As a result, with the same width of the sensor strip perpendicular to its longitudinal axis, twice the resolution in the width direction can be achieved. By arranging more than two sensor strips in the width direction, the resolution of the sensor or measurement signal in the width direction can be further improved.

[0051] Figure 6 shows a similar arrangement to Figure 5, but with a larger number of sensor strips 14-n, with n=1 to N, where n and N are each elements from the set of natural numbers, and with variable widths of the individual width ranges bi, over which one of the spiral-shaped sensor strips extends. These different width ranges bi allow the width resolution to be adjusted depending on the width position. Figure 6 shows an example of an arrangement of width ranges of different widths, as used for flatness measuring rollers to measure flatness, although not yet with sensor strips using thin-film technology. The embodiment according to Figure 6 is particularly characterized in that the widths of the width ranges in the area of ​​the edges of the strip are smaller than the widths of the width ranges in the area of ​​the center of the strip 20; this is particularly advantageous for the aforementioned flatness measurement.The necessary width bz of a width range for a desired width resolution can be determined by.

[0052] Converting the above formula (1 ) can be calculated as follows:

[0053] In order to achieve a resolution of the sensor signal in the width direction of 26 mm at a 42° wrap angle, a zone width or a width of a width range of 180 mm is necessary.

[0054] In Figure 7, the width of the contact roller 12 is also divided into a plurality of adjacent width ranges bi with i = 1-3. Specifically, Figure 7 shows a single sensor strip 14 that extends over a total of three width ranges bi with i = 1-3 and is formed with different pitches on the circumference of the contact roller 12 in the individual width ranges. The sensor strip extends once in the circumferential direction over the entire width of the contact roller. By changing the pitch of the spiral sensor strip in the width direction of the measuring roller, the width resolution of the sensor and measurement signal can be adjusted depending on the rotation position and thus the width position. In Figure 7, the width ranges bi are narrower at the edge than the middle width range, and the pitch of the spiral measuring strip is also greater in these edge areas than in the middle.Therefore, a higher resolution of the measurement signal or sensor signal can be achieved in the edge areas than in the center.

[0055] Figure 8 shows a sixth embodiment of the inventive arrangement of spiral sensor strips on the circumference of a contact roller 12 or a measuring roller 10. Here, several, four electrically separated sensor elements 14-1...4 shown as an example are arranged one behind the other in a straight line or along a spiral on the surface of the contact roller 12.

[0056] Figure 9 shows these individual sensor elements 14 connected as resistors in a Wheatstone bridge or a Thomson bridge. This connection advantageously allows a zero-referenced differential signal to be generated and tapped after applying a + / - supply voltage, thereby fundamentally improving the signal quality and the evaluation options. If the resistance of one of the four sensor strips in Figure 9 changes due to a partial load on this sensor strip, the bridge circuit is trimmed accordingly, and it then generates a corresponding sensor signal at its tapping points S1, S2.

[0057] Furthermore, unloaded sensor elements, in particular sensor strips, can be used as a reference value. For this purpose, Figure 10 shows an arrangement with two sensor strips as an example. In the loading case shown, represented by the horizontal black line as a pressure surface, the first sensor strip 14-1 functions as the active measuring sensor and the second sensor strip 14-2 as the unloaded reference. If the measuring roller continues to rotate, the deflected belt 20 no longer loads the first sensor strip 14-1, but rather the second sensor strip 14-2; thus, the function of the sensor strips then changes. In the latter case, the sensor strip 14-1 is the unloaded reference and the sensor strip 14-2 forms the active measuring sensor. Such arrangements of sensor strips are preferably used for temperature measurements or for temperature sensors.

[0058] For two sensor strips arranged side by side in the width direction and in the circumferential direction in a spiral on the circumference of the measuring roller 10, the following applies:

[0059] If the two sensor signals from the sensor strips 14-1, 14-2 are placed side by side in the width direction b, a rectangular signal waveform is visible across the width B of the contact roller 10; see Fig. 11. The flanks of this rectangle represent – ​​with a certain system-related blur (flank angle = t = 90°) – the position of the strip edges on the circumference of the contact roller. The width positions xb_i=0 of the strip edges are located where the signal waveform S(b) exceeds or falls below a specified threshold value SG. However, this type of width position determination is too imprecise in practice.

[0060] Figures 12 and 13 illustrate how the strip edge position can be determined with higher resolution and accuracy. To do so, in process step 1 in Figure 12, a signal rise or fall of the measurement signal is first simulated in the form of a standardized signal edge profile nS; see Fig. 13. This is determined taking into account the geometry, i.e., the width and length of the sensor strip 14 as well as the position of the sensor strip on the measuring roller 10. This standardized signal edge profile is subsequently scaled and subjected to an iterative or regressive width position adjustment:

[0061] In process step 2, the normalized signal edge profile nS is scaled with the maximum value of the measurement signal. This means: The normalized and scaled signal edge profile nS_i=0 before a first iteration step i, i.e., before an adjustment of the width position, is calculated by multiplying the unscaled normalized signal edge profile nS by a scaling factor k_i=0.

[0062] In method step 3, a starting value for the width position adjustment xb_i=0 of one of the band edges is first approximately determined, as previously described with reference to Fig. 12; ie, by analyzing the course of the measurement signal to determine at which width position the measurement signal course exceeds or falls below the predetermined threshold value SG.

[0063] In step 4: Determine the scaling factor k_i+1 for an i+1 regression step by regressing the squared deviations between the measured signal profile in the edge range and the scaled signal edge profile nS_i in the domain of nS_i such that the deviations from the measured signal are minimized. This results in a normalized scaled signal edge profile nS_i+1 according to the formula: nS_i+1 = k_i+1 * nS_i.

[0064] Subsequently, in step 5, the width position xb_i+1 with the smallest deviations between the signal edge profile nS_i+1 and the measurement signal profile is determined by iteratively shifting the width positions of the normalized and scaled signal edge profile nS_i+1.

[0065] Process steps 3 and 5 are merely optional. This means they can be omitted under certain conditions; see the description of Fig. 18 below.

[0066] Method steps 6 to 8 are self-explanatory in Fig. 12. Fig. 12 shows the inventive method for determining the optimized width position for either the rising or falling edge in the measurement signal, i.e., for the exact position of the left or right band edge. The method according to Fig. 12 must be repeated for the other edge or position of the band edge.

[0067] The width of the band 20 is calculated as the difference between the width positions of the edges of the rectangular width-dependent measurement signal S(b).

[0068] Figure 14 shows an arrangement of, for example, two sensor strips 14-1, 14-2, which are not arranged in a spiral shape, but extend in a straight line in the direction of the width b of the contact roller 12 and are limited to the respective width of their width regions b1, b2. Such an arrangement of sensor strips is preferably used for a capacitive measurement. The two sensor strips are, as shown in Figure 14, also arranged at the same height, i.e. at the same circumferential angular position. For a measurement described below with this arrangement of the sensor strips 14-1, 14-2, it is assumed that the strip 20 contacts the two sensor strips in a contact situation and at least partially covers them in the width direction b; see the hatched areas in Fig. 14. This means that the strip 20 - starting from the center of the barrel of the measuring roller 10, see the dash-dotted vertical line in Fig.14, - extends with a first width range toward a first bale edge and with a second width range toward a second bale edge of the measuring roller 10. The first width range contacts the first sensor strip 14-1, and the second width range contacts the second sensor strip 14-2. The first and second width ranges can be the same or different.

[0069] Each of the two sensor strips 14-1, 14-2 adjacent in the width direction b of the contact roller 12 generates a sensor or measurement signal across the circumferential angle with a peak at the circumferential angle position at which the strip 20 contacts the sensor elements. The heights of the peaks of the sensor signals are proportional to the coverage of the respective sensor element 14-1, 14-2 by the strip 20 in the width direction b of the measuring roller, i.e., in the longitudinal direction of the sensor elements. Provided that the two sensor strips are arranged symmetrically to the center of the measuring roller in the width direction and have the same measurement sensitivity, the following two cases can be distinguished when evaluating or comparing the two sensor signals:

[0070] - i. An equal height of the two peaks means that the belt 20 contacts the measuring roller 10 symmetrically to its bale center.

[0071] - ii. Alternatively, an unequal height of the peaks means that the belt 20 contacts the measuring roller asymmetrically relative to its bale center. The sensor strip with the smaller peak is then less covered by the belt than the sensor strip with the larger peak. Further evaluation of the peaks of the two sensor signals provided by the two sensor elements 14-1, 14-2 allows the belt width and / or the position of the belt on the measuring roller to be determined.

[0072] By adding additional straight sensor strips parallel to the sensor strips shown in Figure 14, the frequency of measurement and thus the resolution of the measurement during one revolution of the contact roller can be increased.

[0073] The sensor elements can be designed not only as thin sensor strips of uniform width, as previously shown and described in Figures 3-14, but also with different widths, as shown in Figures 15 and 16. These sensor strips of different widths are arranged, for example, next to one another in the width direction of the measuring roller 10, as shown in Figures 15 and 16.

[0074] In Fig. 15, each of the sensor strips 14-n extends in the circumferential direction of the contact roller over its entire circumference. Therefore, in this embodiment, the length of the sensor strips 14-n corresponds to the circumference of the measuring roller 10. This design and arrangement of the sensor elements avoids a wrap-angle-dependent width resolution of the surface of a sensor element.

[0075] To improve the signal quality or the resolution in the circumferential direction, the sensor strips 14-n can alternatively each be shorter than the circumference of the measuring roller 10. In this case, a plurality of sensor strips 14-n, for example four in Fig. 16, can be arranged one behind the other, distributed over the circumference of the measuring roller. The sensor strips are preferably each of the same length. A sensor strip is also referred to as a section or sensor tile in its planar extent. Interruptions are provided between the individual sensor strips or sensor tiles, in particular for electrical insulation. In the embodiments shown in Figs. 15 and 16, the sensor tiles - together with the interruptions between them - cover the entire surface of the contact roller.In the arrangements shown in Figures 15 and 16, the sensor strips 14-n are also preferably connected in a bridge circuit to generate a differential sensor signal. By adjusting the spacing between the sensor tiles, i.e., the width of the interruptions in the circumferential direction, a characteristic measurement signal is generated over the course of one revolution of the measuring roller. The spacing can then be increased so that the sensor element length is only 1 - 5 mm. The characteristic measurement signal is then evaluated to obtain further physical properties or measured variables of the belt deflected over the measuring roller. The wrap angle of the belt around the measuring roller can preferably be determined in this way.

[0076] If the pressure on the roller 10 is measured using the arrangement of the sensor elements 14 shown in Figures 5, 6, 15 and 16, the vibration of the belt 20 can be assessed by evaluating the mean value of the simultaneously measured sensor signals or measurement signals S(b). For this purpose, the mean value of the sensor or measurement signals of these sensor elements 14 is calculated at each point in time during a simultaneous measurement by sensors distributed across the belt width. The mean value can be converted into a belt tensile force using the method described above. If this belt tensile force is plotted against time, the result is the time-varying signal of the belt tensile force. In a more detailed analysis, significant frequencies, i.e. critical vibrations of the belt, can be determined from this signal using Fourier transformation, for example. With the help of this frequency analysis, damage to the system, e.g. bearing damage, can be detected.

[0077] Figures 15 and 16 show, by way of example, a full-surface configuration of the sensor elements 14 on the surface of the contact roller. Fig. 17 shows the arrangement of the sensor elements 14-n according to Fig. 16 with increased spacing in the circumferential direction.

[0078] Fig. 18 shows the signal curve of a sensor element according to Fig. 17 over one revolution. Calculating the difference between the rotational positions of the start of contact between the belt and roller and the end of contact results in a contact length Aß in angular degrees. Subtracting twice the length of the signal-generating sensor element from the contact length Aß in the circumferential direction in angular degrees yields the angle of wrap of the belt around the roller.

[0079] According to a further embodiment, a plurality of sensor elements, each realized using thin-film technology, can be arranged one above the other on the circumference of the contact roller 12 to detect different physical measurement variables with respect to the belt 20. The layers for the individual sensor elements 14 are then separated from each other by electrical insulation layers. In this way, different physical measurement variables can be determined simultaneously at a width position. By selecting suitable sensor element designs, a configuration optimized for a particular application of the measuring roller can be selected.

[0080] The sensor elements integrated in the different layers synchronously record different measured variables and also synchronously generate different sensor signals or measurement signals. These signals can be used to compensate for measurement disturbances. For example, one of the sensor elements can represent a temperature sensor, while another sensor element implemented in a sensor layer below or above represents a pressure sensor. Using the measurement signal generated by the pressure sensor, for example, the tensile stress distribution across the width can be determined. Using the synchronously determined temperature profile in the strip, the measurement of the tensile stress distribution can be freed from the influence of temperature expansion. Another preferred compensation using additional sensors consists in determining the strip edge position, for example using inductive sensors as shown in Fig.14 and thereby simplify and improve the procedure according to Fig. 12 by omitting steps 3 and 5.

[0081] By combining different synchronous sensor or measurement signals, additional measured variables or physical properties of the strip 20 can be determined indirectly. This approach is also referred to as a "soft sensor" because the sensor signal is generated by software.

[0082] The invention offers the advantage that the measurement of the measured variables and / or their evaluation with regard to the physical properties of the strip 20 can be carried out continuously during contact with the measuring roller 10. The measurement can advantageously also be carried out at slow speeds down to standstill. By integrating several sensor elements in superimposed sensor layers, as mentioned above, different measured variables or physical properties of the strip can be recorded synchronously. The integration of the sensor elements into the coating of the contact roller 12 enables direct, high-resolution measurement. By appropriately designing the sensor elements, the dependence on, for example, the strip edge position can be minimized.

[0083] List of reference symbols

[0084] 10 measuring roller

[0085] 12 Contact roller

[0086] 14 Sensor element

[0087] 14-n sensor strips n with n=1-N

[0088] 17 angle sensors

[0089] 18 Conversion unit

[0090] 19 Evaluation device

[0091] 20 Band b Width direction bi Width range

[0092] B Width of the band bz Width of the projection of the spiral sensor strip onto the

[0093] Longitudinal axis of the contact roller k_i Scaling factor i Regression step with i=1-l

[0094] SG threshold xb_i latitude position after the i-th regression step

Claims

Patent claims:

1. A measuring roller (10) for contact with a strip (20), in particular a metal strip, comprising: a contact roller (12); at least one sensor element (14) arranged on the surface of the contact roller (12) for detecting at least one physical measurement variable of the strip in the contact area between the measuring roller (10) and the strip (20) and for generating a corresponding sensor signal; an outer coating on at least part of the surface of the contact roller (12); wherein the at least one sensor element (14) is formed flatly using thin-film technology; wherein the outer coating is at least partially formed by the sensor element (14); and wherein the sensor element (14) is in the form of a sensor strip; characterized in that the sensor strip (14) is designed as a single sensor and is arranged spirally on the surface of the contact roller (12).

2. Measuring roller (10) according to claim 1, characterized in that a plurality of the spiral-shaped sensor strips (14-1, 14-2) are arranged at a predetermined circumferential angular distance, e.g. 180°, offset parallel to one another on the surface of the contact roller (12).

3. Measuring roller (10) according to one of claims 1 or 2, characterized in that the spiral sensor strip (14) has a strip width of 1 to 5 mm perpendicular to its longitudinal extent in the width direction of the contact roller (12).

4. Measuring roller (10) according to claim 1, characterized in that the sensor strip (14) is arranged on the surface of the measuring roller (10) extending in the circumferential direction or in the width direction of the measuring roller (10).

5. Measuring roller (10) according to one of the preceding claims, characterized in that the sensor strip is designed such that it extends at least over part of the circumference, preferably over the entire circumference of the contact roller (12).

6. Measuring roller (10) according to one of claims 1 to 5, characterized in that at least two, preferably 4 electrically separated sensor elements (14) are arranged one behind the other in a straight line or along a spiral on the surface of the contact roller and are connected as resistors in a Wheatstone bridge or a Thomson measuring bridge.

7. Measuring roller (10) according to one of the preceding claims, characterized in that the contact roller (12) is divided in the width direction into a plurality of adjacent width regions (bi); and that at least one of the sensor elements (14) is arranged in at least one of the width regions (bi).

8. Measuring roller according to claim 7, characterized in that the sensor element is limited in its extension in the width direction of the contact roller (12) to the width of a width range.

9. Measuring roller according to claim 7 or 8, characterized in that in at least two of the width regions the sensor elements are arranged in the circumferential direction preferably at the same height.

10. Measuring roller according to one of claims 7 to 9, characterized in that a plurality of the sensor elements are arranged distributed over the circumference of the contact roller per width range.

11. Measuring roller according to claim 7, characterized in that the at least one spiral-shaped sensor strip extends over several of the width regions (bi) and is formed in individual of these width regions with different pitches on the circumference of the contact roller (12).

12. Measuring roller (10) according to one of claims 7 to 11, characterized in that the width of the width regions (bi) is at least partially different in the width direction of the measuring roller (10).

13. Measuring roller (10) according to one of the preceding claims, characterized in that the surface of the contact roller (12) is covered by a plurality of Sensor strip (14-n) is completely covered.

14. Measuring roller (10) according to one of the preceding claims, characterized in that a plurality of the sensor elements are arranged one above the other using thin-film technology to detect preferably different physical measurement variables with respect to the strip; and that the individual sensor elements are each separated from one another by electrical insulation layers.

15. Measuring roller (10) according to one of the preceding claims, characterized in that the at least one physical measurement variable that can be detected by the sensor element is, for example, the temperature of the belt and / or the pressure or the force with which the belt presses onto the contact roller, in each case in the contact area between the belt (20) and the measuring roller (10).

16. Measuring roller (10) according to one of the preceding claims, characterized by an angle sensor (17) for detecting the respective current rotational position of the contact roller (12); and a conversion unit (18) for converting the rotational position, taking into account the arrangement and design of the sensor elements (14) on the surface of the contact roller (12), into a position in the width direction of the contact roller (12) or of the belt, wherein a value of the respective sensor signal can be assigned to this width position to generate a width-dependent measurement signal S(b).

17. Measuring roller (10) according to claim 16, characterized by an evaluation device (19) assigned to the measuring roller (10) for evaluating the at least one measuring signal with regard to the strip tension in the strip (20), the distribution of the strip tension over the width of the strip, the width of the strip, the position of the strip on the surface of the contact roller, in particular in the width direction of the contact roller (12), the surface quality, for example the surface roughness, the strength of the strip and / or the wrap angle of the strip around the contact roller, in each case in the contact area between the strip (20) and the measuring roller (10).

18. Method for generating and evaluating a measurement signal of a sensor element (14) of the measuring roller (10) according to one of the preceding claims, comprising the following steps: - detecting the current rotational position of the contact roller (12) with the aid of an angle sensor (17); - converting the rotational position into a position in the width direction of the contact roller (12) or the belt, taking into account the spiral arrangement and the design of the at least one sensor strip (14) on the surface of the contact roller (12); and - Generating a measurement signal S(b) by assigning these width positions to values of the time-dependent sensor signal which the sensor signal currently has at the times of detection of the rotation position.

19. Method according to claim 18, characterized in that the resolution Ab of the measurement signal S(b) from the spirally laid sensor strip is calculated as follows: with au. Wrap angle of the belt when in contact with the contact roller (12) specified in degrees b zWidth in the direction of the longitudinal axis of the roller that is scanned by the sensor element during one revolution; or: width of the projection of the spiral sensor strip (14) onto the longitudinal axis of the contact roller (12) bsF. Width of the spiral sensor element in the direction transverse to its longitudinal extension.

20. Method according to claim 18 or 19, characterized in that the specific strip tensile force curve over the strip width is calculated from the measurement signal of the sensor element (14) designed as a pressure sensor as follows: f B (b) = S(b) * k(b) (2) b: Bandwidth position f B (b): specific belt tension across width S(b): Measurement signal over width k(b): Calibration factor over width 21 . Method according to one of claims 18 to 20, characterized in that the flatness £ (b) of the strip is calculated as follows: e( 'b 7 ) =^ h * E ( v 3 ') with h: thickness of the strip s: Young's modulus fß(b): specific strip tensile force over width 22. Method according to one of claims 18 to 21, characterized in that the position of the edges of the strip on the measuring roller (10) is represented by the width positions of the flanks of the rectangular measuring signal, preferably taking into account the geometry of the sensor element.

23. Method according to claim 22, characterized in that the position of one of the band edges corresponds to the width position where the rectangular measurement signal exceeds or falls below a predetermined threshold value (SG).

24. Method according to claim 23, characterized in that the resolution of the width position of the strip edge is further optimized by performing the following steps: 1 ) Simulating a signal rise or fall of the measuring signal in the form of a normalized signal edge curve nS; 2) Scaling the normalized signal edge profile nS_i=0 before a first iteration step i, by multiplying the unscaled normalized signal edge profile nS with a scaling factor k_i=0; 3) First, approximately determine a starting value for a width position adjustment xb_i=0 of one of the band edges by Analyzing the course of the measurement signal to determine where the measurement signal course exceeds or falls below the specified threshold value SG; 4) Determining a scaling factor k_i+ 1 for an i+1 regression step by regressing the squared deviations between the curve of the measurement signal in the edge range and the scaled signal edge curve nS_i in the definition domain of nS_i in such a way that the deviations from the measurement signal are minimized to generate a normalized and scaled signal edge curve nS_i+1 according to the formula: nS_i+1 = k_i+1 * nS_i; 5) Determining the width position xb_i+1 with the smallest deviations between the signal edge profile nS_i+1 and the measurement signal profile by iteratively shifting the width positions of the normalized and scaled signal edge profile nS_i+1 ; 6) Calculate the magnitudes of the differences: d_nS = lnS_i - nS_i+ 11 d_xb = lxb_i - xb_i+11 7) Check the following two conditions: d_nS < threshold d_xb < threshold. 8) If both conditions according to step 7) are met: Determine the optimized band edge position as: x_B = xb_i+1 ; or if both conditions according to step 7) are not met: Return to step 4) with i = i+1 25. Method according to one of claims 18 to 24, characterized in that the width of the band is calculated as the difference between Width positions of the edges of the rectangular width-dependent measurement signal S(b).

26. Method according to one of claims 18 to 25, characterized in that the necessary width (b z ) of a width range for a predetermined width resolution Ab for a certain wrap angle aU at a width b S F of the sensor element is calculated as follows:

27. Method according to one of claims 18 to 26, characterized in that the following steps are carried out to convert the measurement signal into a zero-related difference signal: - Dividing the sensor strip, which generates the measurement signal, into 4 separate sections, each of which preferably has the same electrical resistance; - Connecting the 4 sections as resistors in a Wheatstone bridge circuit; - Applying a supply voltage to the Wheatstone bridge; and - Tapping the zero-referenced difference signal also from the Wheatstone bridge.

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