Method and device for acoustic wear measurement of linear or rotary drives

Abstract

Methods for fault prevention in electric drives in industrial automation, preferably comprising the following steps: 1.1 Detection of sound level signals inside the electric drive during operation with known sound propagation geometry and known distance to the sound source, 1.2 Continuous comparison of the sound power with a reference sound power and monitoring of the exceedance of the maximum sound energy value, 1.3 Continuously adding up the sound power over time when the sound power exceeds the reference sound power, 1.4 Continuous subtraction of the sound power over time when the sound power falls below the reference sound power, with a minimum value of zero, 1.5 Generating a warning or alarm when the maximum sound energy value is exceeded

Description

[0001] The invention relates to a method and a device for the acoustic wear measurement of electrically driven linear or rotary drives according to the preamble of claim 1. Electric linear drives are known, for example, from EP1 732 197 B1, which is attributed to the same applicant. That document shows a magnetically driven linear motor slide that is movable longitudinally on a guide rail, wherein the linear motor slide contains a number of energized magnetic windings that interact with permanent magnets arranged in the guide rail.

[0002] The linear motor described in our own patent EP1 732 197 B1 has proven itself extensively and has a long service life. However, there is a need to monitor the service life of the bearing elements and, if necessary, issue a warning if the friction-prone bearing elements are wearing. Likewise, there is a need to identify and then perform the necessary lubrication of the bearing elements to extend their service life.

[0003] By capturing and analyzing sound energy, potential sources of error can be identified and diagnosed early, before they lead to major malfunctions. Continuous monitoring of sound energy helps to prevent failures and extend the operating time and service life of electric drives.

[0004] It is known to perform acoustic wear measurements, using sound pressure as an evaluation criterion, as can be seen, for example, in US20180115226A1. A disadvantage of this wear measurement method is that it requires complex evaluation of the sound signal, which involves significant electronic effort. Furthermore, the possibility of false alarms cannot be ruled out because external noise can distort the sound sensor's measurement results and lead to incorrect wear readings.

[0005] Typical failures in electric drives are due to mechanical wear of guide and bearing elements. Lack of maintenance (lubrication) can also cause premature mechanical wear and lead to the failure of the electric drive. Almost without exception, an increase in noise energy can be observed prior to a failure.

[0006] Experience shows that the sound energy steadily increases when a defect is imminent. Sound energy also increases when lubrication is lacking. If the sound energy exceeds a predefined limit, a warning or alarm can be triggered. To calculate the sound energy, the sound power must be known. The sound power of a noise source can be calculated using the distance to the sound pressure sensor (microphone) and the sound propagation geometry. These two parameters—distance to the sound pressure sensor and propagation geometry—are known when a sound pressure sensor is integrated into the electric drive.

[0007] Furthermore, the sound power can also be measured when the drive is stationary, i.e., the ambient sound power. This can then be subtracted from the sound power during operation to obtain the power of the wear-relevant sound source.

[0008] Simple sound pressure measurements are inadequate for detecting newly emerging noises that might indicate an impending defect. Furthermore, an external noise impulse could be misinterpreted and trigger an alarm.

[0009] Several such analytical methods are used today. These require various sophisticated algorithmic evaluations, which are now supported by AI. Such evaluations, like pattern recognition, wavelet transformation, statistical methods, or machine learning, are complex and only worthwhile for larger systems.

[0010] The invention is therefore based on the objective of designing a method and a device for the acoustic wear measurement of electric linear drives in such a way that cost-effective, simple and reliable wear measurement of electric linear drives is possible.

[0011] To solve the problem posed, the invention is characterized by a method and a device carrying out the method according to the independent patent claims.

[0012] Since the distance and propagation geometry of the sound within the electric drive are known, calculating the sound energy via the sound power is straightforward and requires minimal computing power. Therefore, measuring sound energy is a cost-effective method that can also be used for individual components such as electric drives in industrial automation.

[0013] First, a reference sound power level is defined that corresponds to normal operation. Second, a maximum sound energy value is defined, above which a warning or alarm can be triggered.

[0014] If the sound power remains the same as or less than the reference sound power value, no sound energy value is calculated. If the reference sound power value is exceeded, this excess value is integrated over time, and a sound energy value is continuously accumulated. If the reference sound power value is subsequently undershot, this undershot value is also integrated over time and continuously subtracted from the previously exceeded sound energy value. During normal operation, the maximum sound energy value is neither reached nor exceeded. However, the sound power may exceed the reference sound power value for a certain period. With increasing wear, the sound power will rise and exceed the reference value more and more frequently, thus reaching the maximum sound energy value. From this point onward, a warning or alarm must be issued to proactively address an anticipated failure.

[0015] A particularly preferred embodiment of the invention provides a method characterized by the following steps: 1. A method for fault prevention in electric drives in industrial automation, preferably comprising the following steps: • Detection of sound level signals inside the electric drive during operation with known sound propagation geometry and known distance to the sound source • Continuous comparison of the sound power with the reference sound power and monitoring for exceedance of the maximum sound energy value. • Continuously adding up the sound power over time if the sound power exceeds the reference sound power. • Continuous subtraction of the sound power over time when the sound power falls below the reference sound power, with a minimum value of zero. • Generating a warning or alarm when the maximum sound energy value is exceeded 2. A system for carrying out the procedure according to point 1, comprising: • A sound level sensor to detect the sound level signals • Continuous calculation of sound power with level monitoring and integration to determine the exceeding sound energy • Monitoring of excessive sound energy and triggering a warning or alarm when the maximum sound energy is reached

[0016] The subdivision of this preferred method into individual process steps leads to the following technical teaching: Method for acoustic wear measurement of electrically driven linear or rotary drives for detecting wear-related damage to bearing elements, (1) wherein in a first process step the sound power is measured using at least one acoustic sound sensor, (2) wherein in a second process step a continuous comparison of the recorded sound power with a maximum permissible reference sound power is carried out, (3) wherein in a third procedural step a temporary exceedance of the reference sound power is detected, and (4) in a fourth process step, a continuous additive integration of the sound power recorded in the third process step is carried out over time, as long as the sound power exceeds the reference sound power, (5) wherein in a fifth process step a continuous subtractive integration of the sound power recorded in the third process step is carried out over time when the sound power falls below the reference sound power, (6) wherein in a sixth step the additive and subtractive integral surfaces determined in the fourth and fifth steps are summed to form a summation curve, and (7) wherein in a seventh procedure step a warning message and / or an alarm is triggered if the summation curve (38) determined in the sixth procedure step is greater than zero over a specified period of time.

[0017] The invention uses the following preferred definitions: 1. Sound level: This is the sound pressure, measurable via a microphone, that is generated by a sound source. 2. Sound power (of the source): Calculable via the sound level at a known distance and acoustic propagation geometry (These parameters are given by our in-house design of the direct drive) 3. Sound energy: Sound power x time, i.e., integration of sound power over time. 4. Reference sound power: Sound power threshold: If the sound power is above this threshold, it is added to the sound energy over time; if the sound power is below this threshold, it is subtracted from the sound energy over time. 5. Maximum sound energy value: During normal operation, the sound energy builds up and decreases continuously, depending on the speed and load of the drive according to the calculation above. Therefore, during normal operation, it is between 0 and less than the maximum value.

[0018] As wear becomes apparent, the sound energy exceeds the maximum value. An interesting aspect of this method is that this sound energy value can be calculated continuously, eliminating the need for backward calculations over a past period. Likewise, no analysis of the sound vibration (amplitude, frequency, pattern recognition, machine learning, etc.) is required, as demonstrated in US20180115226A1.

[0019] This novel method does not consider accumulated sound energy over a period of time. By comparing the sound power to a reference value before integration, the sound energy does not continuously increase, but rather is constantly added and subtracted. There are no time periods; the process runs continuously. Only when wear occurs does the integrated sound energy drift upwards, triggering an alarm or warning.

[0020] The sound pressure (S1) of the guidance system of a direct drive (linear or rotary) is measured, and the sound power is calculated from this in the acoustic model (S2). The acoustic model (S2) takes into account the sound-relevant mechanical properties as well as the distances to the sound sources in order to determine the sound power from the sound pressure.

[0021] This calculated sound power is compared to the reference sound power using a comparator (C1). The resulting sum (positive or negative) is integrated over time and thus summed up and down as sound energy.

[0022] Our method does not consider an accumulated sound energy over a period of time. Instead, by comparing the sound power with a reference value before integration, the sound energy does not continuously increase, but is continuously added and subtracted.

[0023] In a preferred embodiment of the invention, wear measurement takes place on the moving linear motor carriage and not in or on the stationary guide rail. The arrangement of the acoustic sensor in the moving part, namely in the linear motor carriage or in the rotor of a rotary electric drive, is particularly advantageous. If the following description focuses solely on the advantages and measures applicable to linear drives, this should not be interpreted as a limitation. All features and properties apply analogously to rotary electric drives as well.

[0024] By arranging the sound sensor in the moving part of the drive, the advantage is that wear measurement takes place directly at the location of the bearing elements that are installed in the linear motor slide.

[0025] It has proven particularly advantageous that, in the case of a U-shaped profiled linear motor slide, it is beneficial to arrange at least one sound sensor on the inside of one leg of the U, directly adjacent to the opposite stationary linear rail.

[0026] One obvious option would be to position the sound sensor on the stationary linear rail, but this would have the disadvantage of direct exposure to disruptive ambient noise. Furthermore, it would then be separated from the bearing elements on the slide side by an air gap, which would impair the precision of the sound recording.

[0027] By positioning at least one sound sensor on the inside of the U-shaped leg of the linear slide, a special shielding against ambient noise is achieved. This is because the sound sensor is concealed on the inside of the U-shaped leg, sound-insulated from the outside by the stationary linear rail, and therefore not visible from the outside, making it difficult for disruptive ambient noise to reach it. This largely prevents the measurement of sound power from being affected by interfering ambient noise.

[0028] Furthermore, the arrangement of the sound sensor on the moving part – which accommodates the bearings – means that wear noises of the bearing elements are detected not only via airborne sound propagation, but also via structure-borne sound propagation.

[0029] It has proven advantageous to perform wear measurement in the space between two longitudinally spaced bearing elements on the moving part, with a preference being that a single sound sensor is arranged in this space in the area of ​​a side wall and simultaneously a microprocessor processing the sound event is located at a distance from it, so that the two components are arranged directly adjacent to each other and are only located on a side wall of the linear motor slide in the space between two bearing elements.This has the advantage that the two parts, namely the sound sensor and the microprocessor, are directly connected through the side wall to a connector housing located outside the side wall, in which a communication interface is located, which transmits a signal output via an associated protocol to an alarm device via a connected plug.

[0030] The given technical teaching results in a particularly simple construction, because it is sufficient to arrange such a sound sensor on a single (preferably inner) wall of the linear motor slide and to arrange a microprocessor in the vicinity on the same side, which evaluates the sound result.

[0031] Should the bearing elements of the linear motor carriage on the opposite side wear out, this is communicated to the sound sensor located on the other side via structure-borne noise from the linear motor carriage and via airborne noise. In the inventive method, it is sufficient if one of the four bearing elements shows wear, because an alarm is preferably triggered in this case. Therefore, no indication of the direction or location of the worn bearing element is required, because the sound trigger from a single bearing element is sufficient to consider the linear motor carriage as requiring maintenance and / or unusable and to recognize the end of its service life.

[0032] In this case, it is possible to replace individual bearing elements or to replace the entire linear motor slide with a new one that has new, unused bearing elements.

[0033] Of course, if a wear measurement exceeds a certain specified maximum value, it may also be necessary to replace the corresponding guide rail, because the raceways of the guide rail in the worn bearing elements are worn out and must also be replaced.

[0034] The technical teaching therefore offers the advantage that a simple wear measurement on a magnetically movable linear motor slide or an electromagnetically driven rotor allows for inexpensive and simple wear detection.

[0035] The preferred method involves a comparison with a reference power because, in a first step, a pressure sensor sends its signal to a sound power module, which adds up the sound power and sends it to a calculation module. There, the sum is compared with another value, namely a reference sound power provided by a reference module. The reference sound power is subtracted from the sum of the sound power readings from the pressure sensor, and the result of this addition and subtraction is continuously fed to an integrator. The value of this integrator changes in the positive or negative direction depending on the sound pressure level.When this sound energy determined in the integrator, which can be positive or negative, is fed to a comparator module that continuously compares the integral value with a defined maximum value, an alarm is triggered only when a certain comparison value is exceeded, indicating that the wear is unusually high and that the linear motor carriage or its bearing elements need to be replaced.

[0036] It is important that the system runs continuously and remains installed in its guide rail throughout the entire lifespan of the linear motor carriage, constantly taking measurements. This means that the measurement is continuous, not periodic as is known in current technology. Therefore, there is no comparison with a predefined pattern, and no frequency analysis is necessary; instead, the system simply adds up the sound power recorded by a sound sensor on a side wall of the linear motor carriage.

[0037] The subject matter of the present invention is not only derived from the subject matter of the individual patent claims, but also from the combination of the individual patent claims with one another.

[0038] All information and features disclosed in the documents, including the abstract, and in particular the spatial configuration shown in the drawings, could be claimed as essential to the invention, insofar as they are novel individually or in combination compared to the prior art. The use of the terms "essential," "inventive," or "essential to the invention" is subjective and does not imply that the features so designated must necessarily be part of one or more patent claims.

[0039] The invention is explained in more detail below with reference to a drawing that illustrates only one embodiment. Further essential features and advantages of the invention will become apparent from the drawing and its description.

[0040] They show: Fig. 1: Perspective view of a linear motor axis consisting of a linear motor slide which is driven to be slidable in the longitudinal direction on a fixed guide rail. Fig. 2: The inside of the linear motor carriage according to Fig. 1. Fig. 3: The top view of the Fig. 2 on the linear motor carriage. Fig. 4: Cut along line AA in Fig. Figure 3 shows one side wall of the linear motor slide. Fig. 5: A schematic block diagram of the evaluation of the signals from the sound sensor. Fig. 6a: The representation of sound power in comparison to a reference. Fig. 6b: The representation of the integration or summation of the integrated areas according to Fig. 6a.

[0041] In Fig. Figure 1 generally represents a linear motor axis consisting of a linear motor slide 1 which is driven displaceably in the directions of arrows 49, 50 on a fixed guide rail 47, wherein lateral raceways 48 are provided in the guide rail 47 which engage in associated bearing elements 7, 8 on the inside of the linear motor slide 1.

[0042] The Fig. 2 and Fig. Figure 3 shows further details of the inside of the linear motor carriage, wherein the linear motor carriage 1 consists of a metal part which essentially has a base plate 14 on which two side walls 2, 2 are arranged parallel to each other and spaced apart from each other. A winding housing 4 is arranged on the inside of the base plate 14, which forms an inner winding surface 3. A number of turns, preferably made of copper wires and electrically energized, are arranged in the winding housing 4.

[0043] Due to the electrical current, it is possible to implement a drive for the linear motor carriage 1 in the directions of arrows 49, 50 on the guide rail 47, because a number of permanent magnets 51 are arranged on the guide rail 47, which are in the Fig. 1 are concealed by an upper cover.

[0044] According to the Fig. 2 and Fig. 3. On the inside of the linear motor carriage 1, opposite and parallel guide tracks 5, 6 are arranged, each laterally bounded by bearing elements 7, 8. It is preferred that one opposing bearing element 7, 8 is arranged on each of the entry and exit sides of the linear motor carriage 1, so that a total of four bearing elements form the guide device for the linear motor carriage 1 on the guide tracks 48 of the guide rail 47.

[0045] Each bearing element 7, 8 consists of ball recirculation guides, meaning that a series of balls are arranged on a closed orbit and roll successively along the guide track 48 of the guide rail 47. This results in a particularly low-friction and quiet drive that runs with minimal jamming and exhibits low wear. Should the balls wear, this will be hardly noticeable because each ball only contacts the raceway 48 on the guide rail 47 once before the next ball immediately engages with the raceway 48. Over time, however, one or more balls may wear out, resulting in noise that is to be detected by the wear measurement according to the invention.

[0046] For this purpose, it is provided that an electronic circuit board 9 is installed in the guide track 6 on one side wall 2 of the linear motor slide, which works with a microprocessor 10 that is optically visible in order to visually distinguish the linear motor slide 1 from other linear motor slides in which no wear measurement takes place.

[0047] Preferably, a single sound sensor 11 is arranged in the area of ​​the electronic circuit board 9. A further sound sensor may also be arranged in the opposite housing 12.

[0048] However, it is sufficient to arrange such a sound transducer 11 in a single side wall of a U-shaped linear motor carriage 1, because when one of the bearing elements 7, 8 generates noise, the resulting structure-borne and airborne noise is sufficient to subject the sound transducer 11 to sufficient sound pressure. Since it is located on the inside of the U-shaped leg of the linear motor carriage and covered on the outside by parts of the linear motor carriage 1 and the guide rail 47, it is well shielded against disturbing ambient noise. The sound transducer 11 always moves with the linear motor carriage 1 and thus remains in its noise-protected installation position.

[0049] The signals from the microprocessor 10 and the sound sensor 11 are routed to a side connector housing 13 on the outside of the U-leg, in which a communication interface and an associated connector are arranged to enable a standardized interface for signal transmission.

[0050] It is preferred that the microprocessor 10 evaluates the signals from the sound sensor 11 and only transmits the signal to the communication interface in the connector housing 13 when an alarm is triggered. The microprocessor therefore has only one message or alarm output and can thus be designed to be particularly simple and reliable.

[0051] According to this, the Fig. 2, that all eight bearing elements 7, 8 can be used as sound sources 15 for the sound pressure reception of the sound sensor 11.

[0052] The Fig. 4 shows a section along line AA in Fig. 3, wherein in Fig. 3 the same parts as in Fig. 2 are designated. Fig. Figure 4 shows that a guide groove 16 is present, which interacts with the previously mentioned raceways 48 of the guide rail 47. From Fig. It follows from Figure 4 that the balls 52 run on ball tracks that are aligned longitudinally, i.e., in the direction of displacement of arrows 49 and 50. Single-row ball tracks or double-row tracks, in which the balls 52 are arranged one above the other and parallel to each other, can be provided. This is only shown schematically in Figure 4. Fig. 4 is marked.

[0053] The block diagram of the Fig. 5 will now be based on the Fig. 6a and Fig. 6b is explained in more detail, showing that a sound pressure sensor 17, preferably designed as a microphone, detects the airborne sound and / or structure-borne sound in the area of ​​the inner side wall 2 of the linear motor slide 1 and inputs it as an electrical signal into a sound power module 19 via the signal path 18. Only the sound power is measured in the sound power module 19 and input via path 20 to a computing module 21.

[0054] On the opposite side of the computing module 21 is a reference module 22, which feeds a specific electrical reference value into the computing module 21 via path 23, and the resulting value at path 24 corresponds to curve 24a in Fig. 6a.

[0055] The sum value determined by the calculation module 21 is entered via path 24 into an integrator 25, which, according to the curve Fig. 6a forms integrals 36, 39, 44 above or below the reference sound power 53. This means that starting from a zero position 34, curve 24a rises because the measured sound power increases and continues until it reaches a position 35 where the reference sound power 53 is exceeded. Integration in the form of the integral surface 36 begins when the reference sound power 53 is exceeded.

[0056] The integral surface 36 above the reference sound power 53 is considered an indicator of wear, while the integral surfaces 39 below the reference curve 53 do not represent wear. This allows for temporary overload due to noise generation, for example at very high speeds or if an external noise were to occur. To prevent this from directly triggering an alarm, the integral surfaces 39 are subtracted from the upper integral surfaces 36, 42, 44 and are calculated according to the Fig. 6b is summed, resulting in a summation curve 38. Thus, starting from position 35 in Fig. 6b the summation curve 38 rises and because the sound power decreases in the space between position 37 and position 40, the summation curve will decline and even approach zero at position 40.

[0057] This provides a significant advantage of the wear measurement according to the invention, because temporary increases in noise do not trigger the wear measurement, but on the contrary, lead to a decrease in the summation curve 38. It is a self-correcting system that only triggers an alarm in the event of continuous noise generation, as can be seen, for example, in the progressive curves in Fig. 6a and Fig. Figure 6b shows that when the external noise development at the integral surface 39 decreases, an integral surface 42 indicating overload is generated again at position 41, leading to a repeated summation in Fig. 6b of curve 38 leads, whereby of course integral area 39' is also subtracted and ultimately the integral area 44 leads to such a strong increase in the summation curve 38 that at position 45 an alarm is triggered 46 because the maximum value 54 has been exceeded.

[0058] The special analysis can be derived from Fig. 5 is taken from path 26 because the summation curve 38 is generated at the output of the integrator 25. The summation curve 38 is compared in the comparator module 27 with the maximum permissible sound energy via path 28 to the maximum value 54 in a reference module 29. If the maximum value 54 is exceeded, an alarm is triggered via path 30 in the warning module 31.

[0059] Overall, therefore, in Fig. 6 the sound power 32 is recorded over the time axis 33 and if the reference sound power 53 is exceeded, an integration takes place which is designed to count upwards and downwards, depending on whether the reference sound power 53 is exceeded or not reached.

[0060] This is a significant advantage over the state of the art, because it is a simple, continuously running system that compensates for external noise emissions and operates with exceptional reliability. Drawing legend 1 linear motor slide 2 side wall 3 winding area 4 winding housings 5 Guide track 6 Guide rail 7 Bearing element 8 bearing element 9 Electronic circuit board 10 microprocessor 11 sound transducers 12 Housings (end stop) 13 connector housings 14 Base plate 15 sound sources 16 guide groove 17 sound pressure meters 18 Signal path 19 Sound power module Path 20 21 Computing module 22 Reference module Path 23 24 Path (Result) 24a) Curve 25 Integrator Path 26 27 Comparison module 28 Path 29 Reference module (max) Path 30 31 Warning module 32 sound power 33 Timeline 34 Position 35 Position 36 Integral area (Pos.) 37 Position 38 Summation curve 39 Integral area (negative) 40 Position 41 Position 42 Integral area 43 Summation curve 44 Integral area 45 Position 46 Alarm trigger 47 Guide rail 48 lanes 49 arrow directions 50 arrow directions 51 permanent magnets 52 balls 53 Reference sound power 54 Maximum value

Claims

[1] Method for preventing malfunctions in electric drives in industrial automation, preferably comprising the steps: 1.1 Detection of sound level signals inside the electric drive during operation with known sound propagation geometry and known distance to the sound source, 1.2 Continuous comparison of the sound power with a reference sound power and monitoring of the exceedance of the maximum sound energy value, 1.3 Continuously adding up the sound power over time when the sound power exceeds the reference sound power, 1.4 Continuous subtraction of the sound power over time when the sound power falls below the reference sound power, with a minimum value of zero, 1.5 Generating a warning or alarm when the maximum sound energy value is exceeded [2] Method for acoustic wear measurement of electrically driven linear or rotary drives for detecting wear-related damage to bearing elements (7, 8), wherein (1.1) in a first process step the sound power (32) is recorded with at least one acoustic sound sensor (11), characterized by , that (1.2) in a second process step a continuous comparison of the recorded sound power (24a) with a maximum permissible reference sound power (53) is carried out, (1.3) in a third procedural step a temporary exceedance of the reference sound power (53) is detected, and (1.4) in a fourth process step, a continuous additive integration (36, 42, 44) of the sound power recorded in the third process step is carried out over time, as long as the sound power (24a) exceeds the reference sound power (53), (1.5) in a fifth process step, a continuous subtractive integration (39, 39') of the sound power recorded in the third process step is carried out over time when the sound power falls below the reference sound power (53), (1.6) in a sixth procedure step the additive and subtractive integral surfaces (36, 42, 44; 39, 39') determined in the fourth and fifth procedure steps are summed to form a summation curve (38), and (1.7) in a seventh procedure step a warning message and / or an alarm is triggered if the summation curve (38) determined in the sixth procedure step is greater than zero for a specified period of time. [3] Method according to claim 1 or 2, characterized by , that the alarm triggering in the seventh process step is used to indicate the need for maintenance of the bearing elements (7, 8). [4] Method according to any one of claims 1 to 3, characterized by, that if the alarm activation in the seventh process step persists for a defined period of time which exceeds the period for indicating the need for maintenance of the bearing elements (7, 8) according to claim 2, an indication for replacement of the bearing elements (7, 8) is generated. [5] Method according to any one of claims 1 to 4, characterized by , that to measure the ambient sound power, the sound power (24a) determined in the first process step is measured when the drive is at a standstill. [6] Method according to claim 5, characterized by , that the detected ambient sound power is continuously subtracted from the sound power (24a) during operation of the drive. [7] Method according to any one of claims 1 to 6, characterized by , that a reference sound power level is defined which corresponds to normal operation and that a maximum sound energy value (54) is defined which, if exceeded, triggers a warning or alarm. [8] Device for acoustic wear measurement of the bearing elements (7, 8) of electric linear drives, wherein an electrically energized linear motor slide (1) is slidably driven in guideways (5, 6) of a stationary guide rail (47), wherein the linear motor slide is designed as a U-profile and its side walls (2) overlap the guide rail (47) at least partially from the outside, characterized by , that the device is configured to perform a method according to one of claims 1 to 7, and that at least one acoustic sound sensor (11) is concealed on the inside of the side wall (2) of the linear motor slide (1). [9] Device for acoustic wear measurement of the bearing elements (7, 8) of rotary electric drives, wherein a rotor with bearing elements is driven to rotate on a shaft of a stator, characterized by, that the device is configured to perform a method according to one of claims 1 to 7, and that at least one acoustic sound sensor (11) is arranged on the rotor in the vicinity of the bearing elements. [10] Device according to claim 8 or 9, characterized by , that a microprocessor (10) which detects and evaluates the sound power is arranged in the immediate vicinity of the sound sensor (11). [11] Device according to claim 10, characterized by , that the microprocessor (10) only generates an output signal if the evaluated sound power leads to the result that the bearing elements (7, 8) need to be lubricated or replaced.

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