Abnormality diagnosis device and abnormality diagnosis method for ball screw

Abstract

Provided are an abnormality diagnosis device and an abnormality diagnosis method for a ball screw that allow for detection of abnormality such as damage or abrasion that has occurred in a screw shaft. This abnormality diagnosis device comprises: a vibration sensor (21) that detects vibration during operation of a ball screw; a filtering processing unit (23) that executes filtering processing for extracting a frequency band including at least a feature frequency corresponding to the natural vibration rate of the ball screw with respect to a vibration signal acquired using the vibration sensor (21); an envelope processing unit (241) that executes envelope processing of the vibration signal after the filtering processing; a frequency analysis processing unit (242) that executes fast Fourier transform processing on a time domain signal after the envelope processing; a peak hold and averaging processing unit (243) that executes peak hold and averaging processing of frequency domain data for each sampling period in the fast Fourier transform processing; and an abnormality determination unit (25) that determines abnormality of the ball screw on the basis of the frequency domain data after the peak hold and averaging processing.

Description

Ball screw abnormality diagnosis device and abnormality diagnosis method

[0001] The present invention relates to a ball screw abnormality diagnosis device and method.

[0002] Patent Literature 1 discloses an abnormality diagnosis device and method for mechanical equipment. In this patent Literature 1, vibration signals from the mechanical equipment are filtered to perform envelope processing, and abnormality diagnosis is performed based on the magnitude (signal intensity) of the frequency spectrum of characteristic frequency components corresponding to the natural frequencies of bearings and gears after Fast Fourier Transform (FFT) processing. In such vibration analysis processing using FFT, the signal-to-noise ratio is generally improved by performing arithmetic averaging of each piece of FFT-processed data acquired over multiple periods according to the required frequency resolution. Meanwhile, Patent Literature 2 discloses a ball screw abnormality detection method that uses frequency components below the natural frequency of a nut constituting the ball screw to determine abnormalities based on vibration during ball screw operation.

[0003] Patent No. 4581860 Patent No. 5217743

[0004] Damage and wear of the bearings and nuts of a ball screw can be determined by applying a vibration analysis process using FFT, as described in Patent Document 1, for example. However, to determine damage and wear of the screw shaft of a ball screw, the nut must be moved over the entire area of ​​the screw shaft. Therefore, when applying a vibration analysis process using FFT, the data obtained multiple times after FFT processing is each data from a different position on the screw shaft. For this reason, the natural frequency (characteristic frequency component) generated due to an abnormality in the screw shaft is attenuated by the arithmetic averaging process after FFT processing, and there is a possibility that an abnormality such as damage or wear occurring in a part of the screw shaft cannot be detected.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an abnormality diagnosis device and an abnormality diagnosis method for a ball screw that can detect abnormalities such as damage and wear that have occurred in the screw shaft.

[0006] In order to achieve the above object, a ball screw abnormality diagnosis device according to one embodiment of the present invention comprises a vibration sensor that detects vibrations during operation of the ball screw, a filter processing unit that performs filtering on the vibration signal acquired by the vibration sensor to extract a frequency band that includes at least a characteristic frequency corresponding to the natural frequency of the ball screw, an envelope processing unit that performs envelope processing on the vibration signal after the filtering processing, a frequency analysis processing unit that performs fast Fourier transform processing on the time domain signal after the envelope processing, a peak hold averaging processing unit that performs peak hold averaging of frequency domain data for each sampling period in the fast Fourier transform processing, and an abnormality judgment unit that judges whether there is an abnormality in the ball screw based on the frequency domain data after the peak hold averaging processing.

[0007] With the above configuration, it is possible to execute a ball screw abnormality determination process using the maximum signal strength for each frequency line of the frequency domain data acquired for each sampling period while the ball screw is in operation, thereby detecting abnormalities such as damage or wear occurring in the screw shaft of the ball screw.

[0008] As a desirable aspect of the ball screw abnormality diagnosis device, it is preferable that the abnormality determination unit extracts a signal strength corresponding to a damage frequency of the screw shaft based on the rotational frequency of the screw shaft of the ball screw, and outputs an abnormality determination result for the screw shaft when the signal strength exceeds a predetermined threshold value.

[0009] This makes it possible to output a diagnosis result indicating that an abnormality has occurred in the screw shaft of the ball screw due to damage or wear.

[0010] In a preferred embodiment of the ball screw abnormality diagnosis device, the abnormality determination unit extracts the maximum value of the signal strength within a predetermined range that includes the damage frequency of the screw shaft of the ball screw, and if the maximum value exceeds a predetermined threshold value, outputs an abnormality determination result for the screw shaft.

[0011] This makes it possible to output a diagnosis result indicating that an abnormality has occurred in the screw shaft of the ball screw due to damage or wear.

[0012] A method for diagnosing an abnormality in a ball screw according to one aspect of the present invention includes a first step of detecting vibrations during operation of the ball screw, a second step of performing a filtering process on the vibration signal acquired in the first step to extract a frequency band including at least a characteristic frequency corresponding to the natural frequency of the ball screw, a third step of performing envelope processing on the vibration signal after the filtering process, a fourth step of performing fast Fourier transform processing on the time domain signal after the envelope processing, a fifth step of performing peak hold averaging processing of frequency domain data for each sampling period in the fast Fourier transform processing, and a sixth step of determining an abnormality in the ball screw based on the frequency domain data after the peak hold averaging processing.

[0013] With the above configuration, it is possible to execute a ball screw abnormality determination process using the maximum signal strength for each frequency line of the frequency domain data acquired for each sampling period during ball screw operation, thereby detecting abnormalities such as damage and wear on the screw shaft.

[0014] As a desirable aspect of the method for diagnosing an abnormality in a ball screw, in the sixth step, it is preferable to extract a signal strength corresponding to a damage frequency of the screw shaft based on the rotational frequency of the screw shaft of the ball screw, and output an abnormality determination result for the screw shaft if the signal strength exceeds a predetermined threshold value.

[0015] This makes it possible to output a diagnosis result indicating that an abnormality has occurred in the screw shaft of the ball screw due to damage or wear.

[0016] As a desirable aspect of the method for diagnosing abnormalities in a ball screw, in the sixth step, it is preferable to extract a maximum value of signal strength within a predetermined range including a damage frequency of the screw shaft of the ball screw, and output an abnormality determination result for the screw shaft if the maximum value exceeds a predetermined threshold value.

[0017] This makes it possible to output a diagnosis result indicating that an abnormality has occurred in the screw shaft of the ball screw due to damage or wear.

[0018] According to the present invention, an abnormality diagnosis device and an abnormality diagnosis method for a ball screw are provided that can detect abnormalities such as damage and wear occurring in the screw shaft.

[0019] FIG. 1 is a diagram showing an example of a schematic configuration of a ball screw abnormality diagnosis system. FIG. 2 is a block diagram showing an example of a ball screw abnormality diagnosis device according to an embodiment. FIG. 3 is an image diagram schematically showing a vibration signal acquired in the abnormality diagnosis process according to the embodiment. FIG. 4 is a diagram showing a specific example of a vibration signal acquired in the abnormality diagnosis process according to the embodiment. FIG. 5A is a schematic diagram showing an example of frequency domain data acquired by FFT processing. FIG. 5B is a schematic diagram showing an example of frequency domain data acquired by FFT processing. FIG. 6 is a schematic diagram showing an example of frequency domain data after arithmetic averaging processing. FIG. 7 is a schematic diagram showing an example of frequency domain data after peak hold averaging processing. FIG. 8 is a flowchart showing an example of ball screw abnormality diagnosis processing according to an embodiment. FIG. 9 is a sub-flowchart showing an example of peak hold averaging processing.

[0020] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments. Furthermore, the components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

[0021] 1 is a diagram showing an example of the schematic configuration of a ball screw abnormality diagnosis system. The ball screw 1 has a screw shaft 11 and a nut 12 that is slidably fitted onto the screw shaft 11 via a plurality of rolling elements (not shown).

[0022] Both ends of the screw shaft 11 are rotatably supported by bearings 13, 14, and one end of the screw shaft 11 (the right side in FIG. 1) is connected to the output shaft of a drive motor 15. As the screw shaft 11 rotates, the nut 12 moves linearly in the axial direction of the screw shaft 11 (the direction of the arrow in FIG. 1) between ends A and B shown in FIG. 1.

[0023] In the present disclosure, an abnormality diagnosis device 2 for a ball screw 1 according to an embodiment executes a vibration analysis process while the ball screw 1 is in operation, and diagnoses damage and wear of the screw shaft 11. Specifically, when executing the abnormality diagnosis process for the ball screw 1 according to an embodiment, the abnormality diagnosis device 2 outputs a drive control command and a rotation control command for the motor 15 to the drive control device 3. Based on the control command from the abnormality diagnosis device 2, the drive control device 3 drives the motor 15 to operate the ball screw 1 and move the nut 12 over the entire range of the screw shaft 11. The drive control device 3 outputs the rotation frequency of the motor 15, in other words, the rotation frequency of the screw shaft 11 of the ball screw 1, to the abnormality diagnosis device 2.

[0024] 2 is a block diagram showing an example of a ball screw abnormality diagnosis device according to an embodiment. As shown in Fig. 2, the ball screw abnormality diagnosis device 2 according to the embodiment includes a vibration sensor 21, an AD conversion processing unit 22, a filter processing unit 23, a vibration analysis processing unit 24, and an abnormality determination unit 25.

[0025] The vibration sensor 21 is installed, for example, on the nut 12 of the ball screw 1 shown in FIG. 1 . In the present disclosure, the vibration sensor 21 is exemplified by an acceleration sensor such as an acceleration pickup. The direction of acceleration detection by the vibration sensor 21 may be the axial direction of the screw shaft 11 (the direction indicated by the arrow in FIG. 1 ), or may be a direction perpendicular to the axial direction of the screw shaft 11. Furthermore, the installation location of the vibration sensor 21 is not limited to the nut 12, as long as it is a position where vibrations occurring during operation of the ball screw 1 can be detected. Furthermore, the vibration sensor 21 is not limited to an acceleration sensor. The vibration sensor 21 may be, for example, a displacement sensor or a sound pressure sensor such as a microphone.

[0026] The AD conversion processing unit 22 converts the vibration signal detected by the vibration sensor 21 into digital data.

[0027] The filter processing unit 23 performs a predetermined filtering process on the vibration signal converted into digital data. Specifically, the filter processing unit 23 extracts a frequency band including characteristic frequencies corresponding to various natural frequencies of the ball screw 1. An example of the filter processing unit 23 is a low-pass filter, but the filter processing unit 23 is not limited to this. The filter processing unit 23 may be a high-pass filter, a band-pass filter, or a band-stop filter as long as it is capable of extracting a frequency band including characteristic frequencies corresponding to various natural frequencies of the ball screw 1.

[0028] In the present disclosure, the characteristic frequency is the frequency of the natural vibration that occurs due to damage or wear of the screw shaft 11 of the ball screw 1. Hereinafter, the frequency of the natural vibration that occurs due to damage or wear of the screw shaft 11 of the ball screw 1 is also referred to as the "damage frequency of the screw shaft 11."

[0029] The damage frequency of the screw shaft 11 can be expressed as a value (= Z × fi, hereinafter also simply referred to as "Zfi") obtained by multiplying the relative rotation frequency fi of the screw shaft 11 with respect to the revolution frequency of the rolling elements of the nut 12 by the rolling logarithm Z per lead. The damage frequency Zfi of the screw shaft 11 is given by the following formula (1), where fr is the axial rotation frequency of the screw shaft 11, Dw is the diameter of the rolling elements, Da is the central circle diameter of the rolling elements, α is the thread groove contact angle, and β is the lead angle. The axial rotation frequency fr of the screw shaft 11 can be calculated from the rotation frequency of the motor 15 (the rotation frequency of the screw shaft 11 of the ball screw 1).

[0030]

[0031] The rotation frequency of the motor 15 (the rotation frequency of the screw shaft 11 of the ball screw 1) corresponds to the moving speed of the nut 12 when the abnormality diagnosis process of the present disclosure is performed.

[0032] In the present disclosure, the abnormality determination unit 25 stores in advance a signal strength threshold value corresponding to the damage frequency Zfi of the screw shaft 11 shown in the above formula (1). The abnormality determination unit 25 executes threshold determination processing between the signal strength threshold value corresponding to the damage frequency Zfi of the screw shaft 11 stored in advance and the signal strength corresponding to the damage frequency Zfi acquired by the vibration analysis processing unit 24. The configuration and operation of the vibration analysis processing unit 24 according to the embodiment will be described below.

[0033] The vibration analysis processing unit 24 according to the embodiment includes an envelope processing unit 241, a frequency analysis processing unit 242, and a peak hold averaging processing unit 243. The envelope processing unit 241 performs envelope processing (envelope detection processing) on ​​the vibration signal that has been filtered by the filter processing unit 23. Specifically, the envelope processing unit 241 performs envelope processing on the vibration signal using, for example, a Hilbert transform. The envelope processing unit 241 may perform envelope processing on the vibration signal using, for example, absolute value detection.

[0034] The frequency analysis processing unit 242 performs frequency spectrum analysis processing on the time domain signal. Specifically, the frequency analysis processing unit 242 performs fast Fourier transform (FFT) processing on the time domain signal after envelope processing. Figure 3 is an image diagram that schematically shows a vibration signal acquired in the abnormality diagnosis processing according to the embodiment. In Figure 3, the horizontal axis represents time, and the vertical axis represents the magnitude (acceleration a) of the vibration signal.

[0035] 3, the period for acquiring data in the abnormality diagnosis process according to the embodiment is denoted as T. The frequency resolution in the FFT process is determined by the sampling rate (sampling frequency) and the block size (number of sampled data). The sampling period (time window length) D of the FFT process in the data acquisition period T is defined as the reciprocal of the frequency resolution in the FFT process.

[0036] In abnormality diagnosis processing for bearings, gears, etc., it is common to improve the signal-to-noise ratio by performing arithmetic averaging of frequency domain data (signals after FFT processing) acquired multiple times during a data acquisition period T. However, in order to determine damage or wear on the screw shaft 11 of the ball screw 1, which is the target of abnormality diagnosis in the present disclosure, it is necessary to move the nut 12 over the entire area of ​​the screw shaft 11. Therefore, the frequency domain data acquired multiple times during the data acquisition period T is vibration data acquired at different positions on the screw shaft 11. As a result, the signal strength corresponding to the damage frequency Zfi of the screw shaft 11 is attenuated by the arithmetic averaging processing, and there is a possibility that abnormalities such as damage or wear occurring in a part of the screw shaft 11 cannot be detected. The concept of vibration analysis processing according to the present disclosure will be described below.

[0037] 4 is a diagram showing a specific example of a vibration signal acquired in the abnormality diagnosis process according to the embodiment. In the example shown in Fig. 4, the nut 12 is reciprocated three times between the end A and the end B shown in Fig. 1 during a data acquisition period T.

[0038] 4, in periods T21 and T31, the magnitude of the vibration signal (acceleration a) is an abnormal value at point C near end A. At point C, there is a possibility that damage or wear has occurred to the screw shaft 11.

[0039] 5A and 5B are schematic diagrams showing an example of frequency domain data acquired by FFT processing. FIG. 6 is a schematic diagram showing an example of frequency domain data after arithmetic averaging processing. FIG. 7 is a schematic diagram showing an example of frequency domain data after peak hold averaging processing. In FIGS. 5A, 5B, 6, and 7, the horizontal axis represents frequency, and the vertical axis represents signal strength of the frequency domain data.

[0040] 5A illustrates frequency domain data acquired when the nut 12 passes through a damaged portion of the screw shaft 11. When the vibration signal passing through sections T11A, T21A, and T31A in FIG. 4 is subjected to FFT processing, frequency domain data such as that shown in FIG. 5A is acquired. As shown in FIG. 5A, in the frequency domain data acquired when the nut 12 passes through a damaged portion of the screw shaft 11, the signal strength of the damage frequency Zfi of the screw shaft 11 and the second harmonic component 2Zfi, the third harmonic component 3Zfi, and the fourth harmonic component 4Zfi of the damage frequency Zfi are high. However, in the frequency domain data acquired when the nut 12 passes through a portion with no damage or only slight wear, as shown in FIG. 5B, the signal strength of the frequency components corresponding to the damage frequency Zfi of the screw shaft 11 and its harmonic components 2Zfi, 3Zfi, and 4Zfi is low. 5B illustrates a plurality of frequency domain data sets obtained when the nut 12 passes through a plurality of locations with no damage or only slight wear. When the vibration signal passing through sections T11B, T21B, and T31B in FIG. 4 is subjected to FFT processing, the frequency domain data sets shown in FIG. 5B are obtained.

[0041] In a configuration for diagnosing abnormalities such as damage and wear of the screw shaft 11 of such a ball screw 1, if frequency domain data acquired multiple times is subjected to additive averaging processing as shown in Figure 6, the signal strength of the damage frequency Zfi of the screw shaft 11 and its harmonic components 2Zfi, 3Zfi, 4Zfi, etc. will be attenuated, and it may be impossible to detect abnormalities such as damage and wear that have occurred in part of the screw shaft 11.

[0042] When only a portion of the screw shaft of the ball screw 1 is damaged, if frequency domain data is acquired multiple times, most of the frequency domain data will be acquired when the nut 12 passes through an undamaged portion. In other words, most of the frequency domain data has low signal strength as shown in Fig. 5B , and when averaging is performed, the signal strength after averaging is attenuated due to the influence of the frequency domain data with low signal strength, so there is a possibility that an abnormality such as damage or wear that has occurred in a portion of the screw shaft 11 cannot be detected.

[0043] For this reason, in the present disclosure, a peak hold averaging processing unit 243 that performs peak hold averaging of frequency domain data after FFT processing is provided downstream of the frequency analysis processing unit 242 that performs frequency spectrum analysis of the time domain signal.

[0044] Specifically, the peak hold average processing unit 243 acquires the maximum value for each frequency (frequency line) for which spectral data, determined by the frequency resolution of the frequency domain data after FFT processing, should be generated, and generates the spectral data shown in Fig. 7. This makes it possible to detect the signal strength of the damage frequency Zfi and each harmonic component 2Zfi, 3Zfi, 4Zfi, etc., that occurs due to damage or wear that has occurred in a part of the screw shaft 11.

[0045] The abnormality diagnosis process for the ball screw 1 according to the embodiment will be described below. Fig. 8 is a flowchart showing an example of the abnormality diagnosis process for the ball screw according to the embodiment.

[0046] In the abnormality diagnosis system for the ball screw 1 shown in FIG. 1 , the abnormality diagnosis device 2 according to the embodiment executes a vibration analysis process during operation of the ball screw 1, as described above, to diagnose damage and wear on the screw shaft 11. Specifically, when executing the abnormality diagnosis process for the ball screw 1 according to the embodiment, the abnormality diagnosis device 2 outputs a drive control command and a rotation control command for the motor 15 to the drive control device 3. Based on the control command from the abnormality diagnosis device 2, the drive control device 3 drives the motor 15 to operate the ball screw 1, thereby moving the nut 12 over the entire length of the screw shaft 11 at a speed corresponding to the damage frequency Zfi of the screw shaft 11 expressed by the above equation (1). In other words, the drive control device 3 rotates the motor 15 (screw shaft 11) so that the shaft rotation frequency fr corresponds to the damage frequency Zfi of the screw shaft 11 expressed by the above equation (1) over the entire length of the screw shaft 11. Specifically, the drive control device 3 reciprocates the nut 12 multiple times between ends A and B shown in FIG. 1 , as shown in FIG. 4 , for example.

[0047] The vibration sensor 21 detects vibrations occurring during operation of the ball screw 1. The vibration signal detected by the vibration sensor 21 is converted into digital data and acquired by the AD conversion processing unit 22 (step S100).

[0048] The filter processing unit 23 performs a predetermined filtering process on the vibration signal acquired by the vibration sensor 21 (step S200). Specifically, the filter processing unit 23 extracts a frequency band including at least characteristic frequencies corresponding to various natural frequencies of the ball screw 1.

[0049] The envelope processing unit 241 performs envelope processing on the vibration signal after filtering (step S300). The frequency analysis processing unit 242 performs fast Fourier transform (FFT) processing on the time domain signal after envelope processing, thereby performing frequency spectrum analysis processing (step S400).

[0050] During a data acquisition period T (the operating period of the ball screw 1 in the abnormality diagnosis process) of the ball screw 1 according to the embodiment, the frequency domain data after the frequency spectrum analysis process is input sequentially to the peak hold averaging processing unit 243 for each sampling period (time window length) D defined by the reciprocal of the frequency resolution in the FFT process. The peak hold averaging processing unit 243 performs peak hold averaging of the frequency domain data acquired during each sampling period D (step S500). Fig. 9 is a sub-flowchart showing an example of the peak hold averaging process.

[0051] 9, n represents an integer up to the total number N of frequency domain data acquired during the data acquisition period T. Also, in FIG. 9, m represents an integer up to the total number M of frequency lines determined by the frequency resolution of the frequency domain data after FFT processing. Also, Sigfm represents the signal strength for each frequency line m.

[0052] The peak hold averaging processor 243 resets the number n of the frequency domain data acquired during the data acquisition period T (n=0, step S501), and determines whether n=N-1 (step S502). If n=N-1 is not true (step S502; No), the peak hold averaging processor 243 increments the number n of the frequency domain data (n=n+1, step S503).

[0053] Next, the peak hold averaging processor 243 resets the frequency line number m and the maximum value Sigfmmax of the signal strength Sigfm on the frequency line m (m=0, Sigfmmax=0, step S504), and determines whether m=M-1 (step S505). If m=M-1 is not true (step S505; No), the frequency line number m is incremented (m=m+1, step S506).

[0054] When the frequency domain data of the sampling period Dn corresponding to the number n is input, the peak hold averaging processor 243 determines whether the signal strength Sigfm on the frequency line m exceeds the maximum value Sigfmmax (step S507).

[0055] If the signal strength Sigfm exceeds the maximum value Sigfmmax (Sigfm>Sigfmmax, step S507; Yes), the signal strength Sigfm is set to the maximum value Sigfmmax on frequency line m (step S508), and the process returns to step S505, and the processes from step S505 onwards are repeatedly executed.

[0056] If the signal strength Sigfm is equal to or less than the maximum value Sigfmmax (Sigfm≦Sigfmmax, step S507; No), the process returns to step S505, and the processes from step S505 onwards are repeatedly executed.

[0057] If m=M-1 in the process of step S505 (step S505; Yes), the process returns to step S502, and the processes from step S502 onward are repeatedly executed. If n=N-1 in the process of step S502 (step S502; Yes), the process returns to the abnormality diagnosis process shown in Fig. 8. By the peak hold averaging process shown in Fig. 9 described above, it is possible to obtain the maximum value for each frequency line determined by the frequency resolution of the frequency domain data after FFT processing, and to generate the spectrum data shown in Fig. 7.

[0058] 8, the abnormality determination unit 25 calculates the shaft rotation frequency fr of the screw shaft 11 of the ball screw 1 based on the rotation frequency of the motor 15 (screw shaft 11), extracts the signal strength SigZfi corresponding to the damage frequency Zfi of the screw shaft 11 expressed by the above formula (1) (step S600), and performs a comparison process with the pre-stored signal strength threshold Sigth (step S700). Specifically, the abnormality determination unit 25 determines whether the signal strength SigZfi extracted in the process of step S600 is equal to or less than the signal strength threshold Sigth.

[0059] In the present disclosure, the signal strength SigZfi corresponding to the damage frequency Zfi of the screw shaft 11 may be a signal strength that becomes a maximum value within a predetermined range including the damage frequency Zfi of the screw shaft 11. Specifically, the signal strength SigZfi corresponding to the damage frequency Zfi of the screw shaft 11 is preferably a signal strength that becomes a maximum value within a range of, for example, 0.9 Zfi or more and Zfi or less.

[0060] If the signal strength SigZfi extracted in the processing of step S600 is equal to or less than the signal strength threshold value Sigth (SigZfi≦Sigth, step S700; Yes), it is determined that no abnormality due to damage or wear has occurred in the screw shaft 11 of the ball screw 1, which is the target of abnormality diagnosis in this disclosure, and the ball screw 1 is determined to be normal (step S800A), and the normal diagnosis result is output (step S900), and the abnormality diagnosis processing is terminated.

[0061] If the signal strength SigZfi extracted in the processing of step S600 exceeds the signal strength threshold Sigth (SigZfi > Sigth, step S700; No), an abnormality is determined to have occurred due to damage or wear of the screw shaft 11 of the ball screw 1 that is the target of abnormality diagnosis in this disclosure (step S800B), the diagnosis result of the abnormality determination is output (step S900), and the abnormality diagnosis processing is terminated.

[0062] In this way, the abnormality diagnosis device 2 and abnormality diagnosis method for a ball screw 1 according to an embodiment of the present disclosure can detect abnormalities such as damage and wear that have occurred in the screw shaft 11 of the ball screw 1.

[0063] REFERENCE SIGNS LIST 1 ball screw 2 abnormality diagnosis device 3 drive control device 11 screw shaft 12 nut 13, 14 bearing 15 motor 21 vibration sensor 22 AD conversion processing unit 23 filter processing unit 24 vibration analysis processing unit 25 abnormality determination unit 241 envelope processing unit 242 frequency analysis processing unit 243 peak hold average processing unit

Claims

1. a vibration sensor that detects vibration during operation of the ball screw; a filter processing unit that executes a filtering process on the vibration signal acquired by the vibration sensor to extract a frequency band including at least a characteristic frequency corresponding to a natural frequency of the ball screw; an envelope processing unit that performs envelope processing on the vibration signal after the filtering process; a frequency analysis processing unit that performs a fast Fourier transform process on the time domain signal after the envelope process; a peak hold averaging processing unit which sequentially receives frequency domain data after frequency analysis processing for each sampling period defined by the reciprocal of a frequency resolution in a fast Fourier transform processing, and performs peak hold averaging processing on the frequency domain data acquired in each sampling period; an abnormality determination unit that performs an abnormality determination for the ball screw based on the frequency domain data after peak hold averaging; Equipped with Ball screw abnormality diagnosis device.

2. The peak hold average processing unit is A maximum value of the signal strength acquired in each sampling period is acquired for each frequency line determined by the frequency resolution of the frequency domain data after the fast Fourier transform processing, and frequency domain data is generated based on the maximum value of the signal strength for each frequency line.

2. The ball screw abnormality diagnosis device according to claim 1.

3. The abnormality determination unit A signal strength corresponding to a damage frequency of the screw shaft is extracted based on a rotation frequency of the screw shaft of the ball screw, and when the signal strength exceeds a predetermined threshold, an abnormality determination result of the screw shaft is output.

3. The ball screw abnormality diagnosis device according to claim 2.

4. The abnormality determination unit extracting a maximum value of a signal strength within a predetermined range including a damage frequency of the screw shaft of the ball screw, and outputting an abnormality determination result of the screw shaft when the maximum value exceeds a predetermined threshold value; 3. The ball screw abnormality diagnosis device according to claim 2.

5. A first step of detecting vibration during operation of a ball screw; a second step of performing a filtering process on the vibration signal acquired in the first step to extract a frequency band including at least a characteristic frequency corresponding to a natural frequency of the ball screw; A third step of performing an envelope process on the filtered vibration signal; a fourth step of performing a fast Fourier transform on the enveloped time domain signal; a fifth step of sequentially inputting frequency domain data after frequency analysis processing for each sampling period defined by the reciprocal of a frequency resolution in the fast Fourier transform processing, and performing peak hold averaging processing of the frequency domain data acquired in each sampling period; A sixth step of determining whether or not the ball screw is abnormal based on the frequency domain data after the peak hold averaging process; having How to diagnose abnormalities in ball screws.

6. In the fifth step, A maximum value of the signal strength acquired in each sampling period is acquired for each frequency line determined by the frequency resolution of the frequency domain data after the fast Fourier transform processing, and frequency domain data is generated based on the maximum value of the signal strength for each frequency line. The method for diagnosing an abnormality in a ball screw according to claim 5.

7. In the sixth step, A signal strength corresponding to a damage frequency of the screw shaft is extracted based on a rotation frequency of the screw shaft of the ball screw, and when the signal strength exceeds a predetermined threshold, an abnormality determination result of the screw shaft is output. The method for diagnosing an abnormality in a ball screw according to claim 6.

8. In the sixth step, extracting a maximum value of a signal strength within a predetermined range including a damage frequency of the screw shaft of the ball screw, and outputting an abnormality determination result of the screw shaft when the maximum value exceeds a predetermined threshold value; The method for diagnosing an abnormality in a ball screw according to claim 6.