Method and device for determining at least one physical characteristic of a belt and computer program

Abstract

The invention relates to a method for determining at least one physical characteristic of a belt drive and / or a belt in the belt drive in a static and / or dynamic operating state. The invention also relates to a computer program for implementing such a method. Furthermore, the invention relates to a device for determining at least one physical characteristic of a belt drive and / or a belt in a belt drive in a static and / or dynamic operating state.

Description

[0001] The invention relates to a method for determining at least one physical characteristic of a belt drive and / or a belt in the belt drive in a static and / or dynamic operating state. The invention also relates to a computer program for implementing such a method. Furthermore, the invention relates to a device for determining at least one physical characteristic of a belt drive and / or a belt in a belt drive in a static and / or dynamic operating state.

[0002] DE 10 2011 055 576 A1 proposes using a mobile computer to determine mechanical stress states on a drive belt. Acoustic vibrations of the drive belt are recorded using a microphone and evaluated, for example, using Fourier analysis. Determining such a belt parameter by recording acoustic parameters has many disadvantages, such as high susceptibility to ambient noise and problems in the lower frequency range (infrasound). Furthermore, determining the belt parameter during dynamic operation, i.e., while the belt drive is running, is not possible.

[0003] The invention is based on the object of providing improved possibilities for determining at least one physical characteristic of a belt in a belt drive in the static and / or dynamic operating state, which can be implemented simply and cost-effectively.

[0004] This object is achieved in a method of the type mentioned at the outset in that vibrations of the belt are recorded as an image sequence consisting of a large number of individual images using a camera. The vibration frequency of the belt is determined by evaluating the individual images. Using the determined vibration frequency and characteristics of the belt and / or the belt drive and, if appropriate, adding at least one further measured variable, at least one further physical characteristic of the belt drive and / or belt is determined. The further physical characteristic of the belt drive and / or belt is thus a different (additional) characteristic than the determined vibration frequency. Such recording and evaluation of an image sequence can be achieved with considerably less interference than the aforementioned acoustic signal evaluation. The required camera does not place particularly high demands on it.

[0005] In particular, the method can be carried out using a commercially available mobile device, e.g. a smartphone or other mobile phone or a tablet. For example, a software application in the form of an app can be installed on the mobile device, which contains the corresponding commands for carrying out the method according to the invention. The results of the evaluation can, for example, be shown directly on the display of the mobile device. In this way, the user is able to record physical parameters of the belt in a belt drive at any time using their mobile device, which is particularly easy to carry in a pocket in the case of a mobile phone or smartphone. Advantageously, the desired physical parameter can be recorded either in static and / or dynamic operating conditions, i.e. when the belt drive is at a standstill or when the belt drive is running.

[0006] Determining such belt parameters in the simple manner described using a mobile device offers significant advantages over conventional methods. Compared to static tests, which are often based on frequency measuring devices, the camera-based method according to the invention enables simpler and more accessible recording. Sufficiently precise results can be achieved using the camera of the mobile device. In dynamic testing, i.e., when the belt is running, complex measuring system components such as sensors and magnetic elements are often used. The invention can significantly simplify the testing process. The camera used can be used effectively to measure vibration without having to resort to complex sensors.This simple approach, accessible to virtually everyone, can be implemented not only more cost-effectively but also more user-friendly and flexible in various application scenarios. In many situations, occupational safety can also be improved compared to previous measurement methods.

[0007] According to an advantageous embodiment of the invention, the determination of the vibration frequency and / or the other physical characteristic of the belt drive and / or belt is carried out without detecting acoustic signals from the belt. This further improves the method's immunity to interference. Furthermore, the method can also be carried out with devices that do not have a microphone.

[0008] According to an advantageous embodiment of the invention, at least one of the following parameters is determined as a further physical characteristic of the belt: dynamic belt force, belt power, and belt slip. Accordingly, particularly important parameters of the belt in practice can be easily recorded.

[0009] According to an advantageous embodiment of the invention, it is provided that one or more of the following characteristics are used as characteristics of the belt and / or the belt drive: specific belt mass, statistical target strand force, one or both strand lengths.

[0010] The belt characteristics required for carrying out the method according to the invention can, for example, be stored in advance on the device executing the method. It is also possible for the device executing the method to determine the required characteristics from at least one external database during the runtime of the method, e.g., in the case of a mobile device with a radio interface, via wireless communication with the database, e.g., via the Internet.

[0011] According to an advantageous embodiment of the invention, by evaluating the individual images, a belt identification of the belt used is automatically recorded in the sense of an article number, and on the basis of the recorded belt identification, characteristics of the belt are automatically determined. This is a further advantageous possibility for determining at least one characteristic of the belt, such as belt length. The belt identification in the sense of an article number can be an EAN, for example. The device used to carry out the method can then either automatically determine the characteristics of the belt in a database stored in the device based on the belt identification. Alternatively, the device can, as explained above, determine the required characteristics of the belt from a remote database via a radio interface.

[0012] According to an advantageous embodiment of the invention, the image sequence is captured as a high-speed image sequence. This allows the measurement accuracy of the method to be further improved. It is advantageous, for example, if the image sequence is recorded at a frame rate of more than 30 frames per second, e.g. at least 50, at least 75 or at least 100 frames per second. In an advantageous embodiment, the camera used can be designed as a high-speed camera. If a commercially available mobile device is used to carry out the method, many devices such as smartphones already have the option of operating the built-in camera in slow-motion mode. This also allows the image sequence to be captured as a high-speed image sequence with a sufficient frame rate.

[0013] According to an advantageous embodiment of the invention, position markers arranged on the belt are detected by evaluating the individual images, and at least the belt speed is determined using the detected position markers. This allows another important and frequently required characteristic of the belt to be determined automatically without the need for additional sensors. The individual images used to determine the vibration frequency can be used directly, i.e., no separate image sequence recording is required. Of course, it is also possible to record an additional image sequence.

[0014] According to an advantageous embodiment of the invention, the belt span lengths and / or pulley diameters of a drive pulley and / or a driven pulley of the belt drive are automatically determined by evaluating the individual images, in particular using an augmented reality app. This allows one or more other important and frequently required belt parameters to be determined automatically without the need for additional sensors. The individual images used to determine the vibration frequency can be used directly, i.e., no separate image sequence recording is required. Of course, it is also possible to record an additional image sequence.

[0015] According to an advantageous embodiment of the invention, vibrations of the belt are generated in the static operating state by randomly mechanically exciting the belt. In this way, at least one characteristic of the belt drive and / or belt can be determined particularly easily and without risk in the static operating state, e.g., by simply manually plucking the belt, similar to the string of a musical instrument.

[0016] The aforementioned object is also achieved by a computer program with program code means configured to carry out a method of the type described above when the computer program is executed on a computer. This also allows the previously described advantages to be realized. In an advantageous embodiment, the computer program can be designed as an app for a mobile device. Of course, if something other than a mobile device is used as the device for carrying out the method, it is also possible to design the computer program as a software program suitable for such a device.

[0017] The object mentioned at the outset is also achieved by a device for determining at least one physical characteristic of a belt drive and / or a belt in a belt drive in the static and / or dynamic operating state, wherein the device is configured to capture vibrations of the belt as an image sequence comprising a plurality of individual images by means of a camera and to determine the vibration frequency of the belt by evaluating the individual images and to determine at least one further physical characteristic of the belt drive and / or the belt using the determined vibration frequency and characteristic data of the belt and / or the belt drive and, if appropriate, adding at least one further measured variable. The advantages explained above can also be realized in this way.

[0018] Such a device can also perform the additional method steps explained above. The device can be configured as a mobile terminal with at least one camera, in particular as a smartphone, other mobile phone, or tablet. Alternatively, the device can also be configured as any other computer device, e.g., a PC or laptop. The device can also implement the explained functions and / or method steps without the use of software or with only partial use of software, e.g., if the device has an FPGA.

[0019] By determining at least one physical characteristic of the belt drive and / or the belt according to the invention, the belt drive can be operated more reliably and safely. For example, regular checks on the belt drive can be easily performed to identify, for example, a need to adjust the belt tension and implement the appropriate correction.

[0020] Without a minimum belt pre-tension (ie load-free belt force F 10 =F 20 ), no V-belt or timing belt can operate, i.e., transmit power. Excessive belt pretensions or loads (i.e., belt power P = belt force difference (F1-F2) · belt speed v) significantly impair belt service life. Therefore, measuring and carefully adjusting the belt forces F1, F2, and the belt speed v are fundamental to the operation of a belt drive.

[0021] To date, belt force has only been measured statically, i.e., at standstill. For simplification, the belt load is equated with the rated motor power, and possible partial load operation or load peaks are only rudimentarily taken into account (i.e., using c-factors). A more precise measurement of axle force and pulley torque is generally far too complex. Dynamic belt force measurement is even more complex.

[0022] The static strand force is usually determined by "tapping" and measuring the frequency between 10 and 600 Hz of a distance, for example, measured optically from the sensor to the back of the belt. To do this, the tester needs a suitable measuring device, space in the application for the measuring head, and additional data (static target strand force, strand length, and specific belt mass) for the application-specific target frequency. The belt manufacturer must develop, certify, produce, distribute, and maintain the devices, as well as provide the tester with the target frequency.

[0023] The invention now allows the determination of belt pretension and load, as well as the aforementioned additional data, using only a standard mobile phone with a camera, for example. The belt is recorded, for example, in slow motion using a mobile phone camera, and the belt vibration frequency and speed are then determined from the individual images. The belt marking may contain a unique article number, which the app uses to query the target belt tension and belt mass via a barcode and an internet query. A standard mobile phone camera-based augmented reality app can be used to measure the belt length and pulley diameter.

[0024] Belt drives transmit power P = (F1-F2)*v, in that - in addition to the belt rotation at speed v - the (positive) tensile force in the tight side F1 exceeds that in the slack side F2, thus creating a tangential force Ft = F1-F2. In the case of force-locking V-belt and flat belt drives, due to F1 / F2 ≤ e µ'.ß enough residual slack force F 2,minremain so that the belt does not slip. Therefore, belts must always be pre-tensioned, in the simplest and most common case by adjusting the belt elasticity and then setting a fixed center distance.

[0025] If the tight side force F1 increases excessively or the slack side force F2 decreases unacceptably, the belt will fail prematurely due to excessive loading or excessive temperature caused by slippage. During installation and, if necessary, during regular maintenance, the belt must be pre-tensioned or re-tensioned while at rest. However, excessive loading and slippage only become truly apparent during operation under load, which is why a simple measurement of the static side forces provides a basis, but a measurement of the dynamic side forces and belt speed under load is even more useful.

[0026] However, simply determining the belt tension and belt speed is far from sufficient; the installer or service technician must also know the target values, which requires a lengthy calculation. Given the large number of machine elements to be installed or serviced, they can neither memorize the target values ​​nor calculate them in the field. As a workaround, an electronic link, such as an RFID tag, can be placed near the belt to determine the required target values ​​by evaluating this electronic link.

[0027] The strand forces can be determined very precisely by measuring the forces and torques on the pulleys, but this is extremely complex due to the price of the sensors, their electrical connection and their integration into the force flow.

[0028] Therefore, the determination of the strand force via the strand vibration frequency has become established - a strand is manually plucked while stationary and its vibration frequency is measured via a measuring head, which usually works using laser triangulation. From the vibration frequencies f 1,2 Then, using the string vibration formula, the strand forces are calculated to F 1,2 = 1 / 4 · f 1,2 · L 1,2 / k with span lengths L 1,2 and specific belt mass k = m / L.

[0029] For running belts, the following must be taken into account regarding force measurement via belt vibration: • The vibration frequency decreases predictably with increasing belt speed • External excitations can cause the predominance of a harmonic (n>1) • For reflection-based measurement systems, third-party protection rights exist until 2030 • Manually positioning the measuring head close to the belt is dangerous

[0030] To measure the strand lengths and disc diameters, sufficiently accurate mobile phone apps can be used, which determine object lengths in the cm to m range via mobile phone camera and augmented reality.

[0031] The invention enables, for example, the following: - Determination of the static belt force via plucking and belt vibration measurement using, for example, optical distance or acoustic noise - Measurement of dynamic belt strand forces using belt vibration measurement - Use of a mobile app to store or web query the belt target strand force and specific belt mass for the belt type to be entered - Measuring strand length and diameter via mobile phone camera and app - Recording the belt vibration using a high-speed camera, e.g., a mobile phone camera in slow motion mode, preferably with a view of the belt flank (belt force) or back (belt speed) in the center of the belt. Today's top-of-the-line models, such as the Samsung Galaxy S23 or Motorola Edge 40 Pro, allow image sequences of b = 960 fps (single frames per second), while good models (e.g., the Apple iPhone 15 Pro Series) allow a minimum of 240 fps, and this for at least a few tenths of a second. The flashlight function commonly found in mobile phones ensures sufficient illumination, and the standard camera phone zoom ensures a sufficiently safe distance, even when the belt is traveling. - By viewing the individual images of the video of the temporal length T, count the complete oscillation processes z and determine the oscillation frequency f = z / T. The observation can be performed by image recognition software, e.g., by determining the center of gravity perpendicular to the direction of travel of the belt, which differs from the background, for example, in terms of brightness or color. The temporal image center of gravity course then yields the oscillation frequency, e.g., via simple approximation of a sine function or Fast Fourier analysis. By manual viewing or strip-by-strip image recognition, the fundamental oscillation is differentiated from harmonics and other vibration modes such as torsion. To detect at least one oscillation with f min = 10 Hz are sufficient T= 0.1 s video length, for oscillations up to f max< 480 Hz according to b ≥ 960 fps. Since belt vibration frequencies are generally below 240 Hz, and for top-of-the-line timing belts below 480 Hz, today's "good" mobile phones generally deliver sufficiently high-resolution and long image sequences. - If the position shift s of markers, preferably on the back of the belt, is observed in the individual images in the running direction, the belt speed v = s / t results from s in time t (1 / b ≤ t ≤ T). If the marker of length a is completely visible over ap pixels in an individual image, s only follows from its "pixel shift" sp using s = a sp / ap. The entire belt marking or prominent parts of it are advantageously used as a marker. With s ≥ 50 mm and t ≤ 0.1 s, v ≥ 0.5 m / s can be measured, and with s ≤ 210 mm and t ≥ 1 / b := 1 s / 240 v ≤ 50.4 m / s, which covers the belt load-relevant range. - Especially for shorter belts of length L, the time tz for a full belt revolution can also be used to measure the speed. If z belt revolutions, i.e. markers at the same image position, are detected in individual images over the period tz, the belt speed is v = L · z / tz. Accordingly, the pulley speeds of the pulleys can be determined as n = z / tz with the number of pulley marker revolutions in the time tz. Thus, with L = 1.2 m, z = 1 and tz = 0.1 s, speeds v ≥ 12 m / s and pulley speeds n ≥ 600 min can be achieved. -1 determine. - Instead of manually typing the belt type indicated alphanumerically on the belt label into the mobile phone, a machine-readable belt type specification, e.g., a barcode with the article EAN number, can enable faster and error-free determination of the belt type. If the app retrieves the specific mass and static target belt force associated with the article number via the web, for example, the app or operator only needs to determine the belt lengths before the app can determine the target vibration frequencies and compare them with the measured values. Conversely, the dynamic vibration frequencies, the belt lengths, the specific belt mass, and the belt speed can be used to determine the dynamic belt forces F1 and F2 and thus the belt power P = (F1-F2) · v. With the pulley speeds n and the pulley diameters d determined manually or via the app, as well as the nominal belt power P retrieved from the app, e.g., via the app N= f (belt type, belt length, n, d) you can check whether the belt is overloaded, ie P > P N is. - The slip s = 1 - (n2 · d2) / (n1 · d1) can be determined from the pulley diameters and the pulley speeds. If it is above a critical value (usually 2%), the ratio of the determined dynamic strand forces F1 / F2 can be used to estimate whether this is due to insufficient belt pretension, i.e., F1 / F2 > ≤ e µ·ß This requires knowledge of the belt-specific friction coefficient µ' (e.g., via web query) and the application-specific pulley wrap b (e.g., estimation on-site). While belt friction coefficients can currently be measured, they are not yet known universally for all belts. However, there are already angle-measuring mobile apps whose accuracy appears sufficient for wrap angle measurement. - The provision of a wide range of belt-specific data, e.g. via the web, as well as the measurement of application-specific values, enables comprehensive installation and maintenance support, even for "unskilled" persons without prior or additional information, e.g. with step-by-step instructions. They also allow qualified maintenance and replacement decisions, e.g. for belt retensioning or ordering information for the replacement belt. The performance and slippage test provides information for proper use and possible redesign. The tracking of strand forces, power outputs and slippage gives machine and component owners and manufacturers information on intended use and proper maintenance, which can be used, for example, for warranty or goodwill decisions. Based on this type of tracking data, belt and machine manufacturers can offer their customers discounts such as extended warranties or longer belt replacement intervals.Last but not least, tracking data can also provide machine and component manufacturers with field data that would otherwise be difficult to access and valuable for further development.

[0032] In summary, the invention offers the following benefits even with today’s technology: • Replacement of separate devices for belt pretension measurement with everyday technology generally available to every operator. This means that belt manufacturers can replace the development, certification, manufacture, distribution, and maintenance of such separate devices with the development and maintenance of mobile apps. • In addition to pure pre-tension measurement on the stationary belt, also safe strand force measurement on the running belt, speed measurement of belt and pushing and thus determination of belt power and slip. • Target values ​​for belt pretension and power as well as all additional calculation information can be made available online, application- and belt-specifically, using the same app instead of in various ways and usually offline as before. • Application-specific, comprehensive support for commissioning, maintenance, repair and redesign of belt drives, e.g. through specific operating instructions, maintenance reminders and real operating data. • Information and proof of proper commissioning and maintenance by operators to operators, owners, machine and component manufacturers. Conversely, this forms the basis for additional services such as an extended warranty for operators. • Field data for belt and machine developers and users (troubleshooting).

[0033] The invention will be explained below using an embodiment using the Fig. 1 explained in more detail. The Fig. Figure 1 shows a belt drive 1 with a belt 2. The belt drive 1 has a first pulley 3 and a second pulley 4. For example, the first pulley 3 can be configured as the drive pulley, and the second pulley 4 as the driven pulley. However, the arrangement can also be reversed. The belt 2 is tensioned over the first pulley 3 and the second pulley 4.

[0034] In belt drives, the term "strand" refers to a free section of the belt 2 that is not resting on a pulley 3, 4. The "load strand" is the strand of the belt 2 that carries the transmitted load, ie, the strand that is pulled tight by the transfer of the load. The "slack strand" is the loose, not pulled, and slightly sagging strand. As can be seen in the Fig. 1, the belt drive 1 has an upper run 5 and a lower run 6.

[0035] The Fig.1 further shows a device 7, e.g., a mobile device, having a camera 8. Using the camera 8, the device 7 captures a section 9 of the belt 2, e.g., on the lower run 6. The device 7 has a computer and a computer program 10. The computer program 10 is executed on the computer. The camera 8 is controlled by the computer program 10, e.g., by first setting the camera 8 to a high-speed mode (slow-motion operating mode) and then capturing an image sequence with a plurality of individual images of the section 9 of the belt 2 using the camera 8.

[0036] The individual images are evaluated by the computer program 10, e.g., by determining the vibration frequency of the belt 2 through the evaluation of the individual images. Using the determined vibration frequency and further characteristic data of the belt 2 and / or belt drive 1, and optionally adding at least one further measured variable, the computer program 10 then determines at least one further physical characteristic of the belt drive 1 and / or the belt 2. The at least one determined physical characteristic can then be displayed, e.g., on a display of the device 7 or used for further processing, e.g., transmitted to other devices.

[0037] The device 7 has an interface, e.g., a radio interface, with which the device 7 can establish wireless communication with a remotely located computer or database 12 via the Internet 11. Through this communication, the device 7 can obtain the required characteristic data of the belt 2 and / or the belt drive 1 as needed. In this way, the device 7 does not need to store all the characteristic data for a large number of belts 2 or belt drives 1 internally. This saves storage space. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2011 055 576 A1

[0002]

Claims

[1] Method for determining at least one physical characteristic of a belt drive (1) and / or a belt (2) in the belt drive (1) in the static and / or dynamic operating state, characterized by that vibrations of the belt (2) are recorded as an image sequence from a plurality of individual images by means of a camera (8), and the vibration frequency of the belt (2) is determined by evaluating the individual images, and at least one further physical characteristic of the belt drive (1) and / or belt (2) is determined using the determined vibration frequency and characteristic data of the belt (2) and / or the belt drive (1) and optionally adding at least one further measured variable. [2] Method according to claim 1, characterized by that the camera (8) is a camera of a mobile terminal (7), in particular a smartphone, another mobile phone or a tablet. [3] Method according to one of the preceding claims, characterized by that the determination of the vibration frequency and / or the further physical characteristic of the belt drive (1) and / or belt (2) is carried out without detecting acoustic signals of the belt (2). [4] Method according to one of the preceding claims, characterized by that at least one of the following variables is determined as a further physical characteristic of the belt (2): dynamic belt force, belt power, belt slip. [5] Method according to one of the preceding claims, characterized by that one or more of the following characteristics are used as characteristics of the belt (2) and / or the belt drive (1): specific belt mass, statistical target strand force, one or both strand lengths. [6] Method according to one of the preceding claims, characterized bythat by evaluating the individual images, a belt identification in the sense of an article number is automatically recorded and, based on the recorded belt identification, characteristic data of the belt (2) are automatically determined. [7] Method according to one of the preceding claims, characterized by that the image sequence is captured as a high-speed image sequence. [8] Method according to one of the preceding claims, characterized by that position markers arranged on the belt (2) are detected by evaluating the individual images and at least the belt speed is determined using the detected position markers. [9] Method according to one of the preceding claims, characterized by that by evaluating the individual images, the strand lengths of the belt (2) and / or pulley diameters of a drive pulley (3) and / or a driven pulley (4) of the belt drive (1) are automatically determined, in particular by means of an augmented reality app. [10] Method according to one of the preceding claims, characterized by that in the static operating state vibrations of the belt (2) are generated by arbitrary mechanical excitation of the belt (2). [11] Computer program (10) with program code means arranged to carry out the method according to one of the preceding claims when the computer program (10) is executed on a computer. [12] Computer program according to claim 11, characterized by that the computer program is designed as an app for a mobile device (7). [13] Device for determining at least one physical characteristic of a belt drive (1) and / or a belt (2) in a belt drive (1) in the static and / or dynamic operating state, characterized byin that the device is designed to record vibrations of the belt (2) as an image sequence comprising a plurality of individual images by means of a camera (8) and to determine the vibration frequency of the belt (2) by evaluating the individual images and to determine at least one further physical characteristic of the belt drive (1) and / or the belt (2) using the determined vibration frequency and characteristic data of the belt (2) and / or the belt drive (1) and optionally adding at least one further measured variable. [14] Device according to claim 13, characterized by that the device is designed to carry out the method according to one of claims 1 to 10. [15] Device according to claim 13 or 14, characterized by that the device is designed as a mobile terminal (7) with at least one camera, in particular as a smartphone, other mobile phone or tablet.

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