Ball screw state determination device and state determination method

Abstract

Provided are a state determination device and a state determination method for a ball screw capable of improving noise immunity. The device for determining the state of the ball screw is provided with: a vibration information generation unit (201) for generating vibration information indicating the relationship between the nut position of the ball screw and the frequency-vibration level characteristics that vary according to the nut position, on the basis of a vibration signal acquired by a vibration sensor (21) when the ball screw is operating; and a determination unit (202) that performs a state determination process of the ball screw on the basis of first vibration information, which is vibration information generated on the basis of a vibration signal acquired during a first period, and second vibration information, which is vibration information acquired during a second period that is later than the first period.

Description

Technical Field

[0001] The invention relates to a state determination device and a state determination method for a ball screw. Background Art

[0002] Patent document 1 states that: In a direct-acting rolling device such as a ball screw, when the preload decreases due to deformation of the track surface caused by the movement of the rolling element and wear of the rolling element, the vibration intensity decreases and the inspection accuracy of the working state decreases. In the past, a technology for monitoring the vibration value of a vibration signal in a specific frequency band to detect the decrease in the preload applied to the ball screw was disclosed (for example, Patent document 2).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-198398

[0006] Patent Document 2: International Publication No. 2020 / 090479 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] Patent Document 2 describes monitoring the vibration value of a vibration signal in a low frequency band from 10 Hz to 10 kHz. However, it is difficult to eliminate the influence of noise components generated in a production site where a ball screw is used in the low frequency band from 10 Hz to 10 kHz, and thus it is difficult to apply.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a state determination device and a state determination method of a ball screw capable of improving noise resistance.

[0010] Solutions for solving problems

[0011] In order to achieve the above-mentioned purpose, a state judgment device of a ball screw involved in one embodiment of the present invention comprises: a vibration information generating unit, which is generated based on a vibration signal acquired by a vibration sensor when the ball screw is working, and the vibration information represents the relationship between the nut position of the ball screw and the frequency-vibration level characteristic that changes according to the nut position; and a judgment unit, which performs state judgment processing of the ball screw based on first vibration information and second vibration information, wherein the first vibration information is vibration information generated based on the vibration signal acquired in a first period, and the second vibration information is vibration information acquired in a second period later than the first period.

[0012] In the above structure, the second vibration information generated based on the vibration signal acquired during the second period of implementing the state judgment of the ball screw is applied with the first vibration information generated based on the vibration signal acquired during the first period in the state assumed to be normally applied with preload, thereby improving the noise resistance.

[0013] As a desirable aspect of the ball screw state determination device, it is preferable that the vibration information generation unit performs averaging processing of a plurality of first vibration information acquired in the first period.

[0014] Thus, the first vibration information is obtained after the non-steady continuous spectrum is removed.

[0015] As an ideal aspect of the ball screw state determination device, it is preferable that the vibration information generation unit generates the first vibration information by removing a periodic vibration component of the vibration signal acquired in the first period.

[0016] Thus, the first vibration information is obtained after the discrete spectrum is removed.

[0017] As a desirable aspect of the ball screw state determination device, it is preferable that the vibration information generation unit performs averaging processing of a plurality of first vibration information acquired in the first period.

[0018] Thus, the first vibration information is obtained after the non-steady continuous spectrum is removed.

[0019] As a desirable aspect of the ball screw state determination device, it is preferable that the vibration information generation unit performs averaging processing of a plurality of pieces of second vibration information acquired in the second period.

[0020] Thus, the second vibration information is obtained after the non-steady continuous spectrum is removed.

[0021] As a desirable aspect of the ball screw state determination device, it is preferable that the vibration information generation unit generates the second vibration information by removing a periodic vibration component of the vibration signal acquired in the second period.

[0022] Thus, the second vibration information is obtained after the discrete spectrum is removed.

[0023] As a preferred embodiment of the ball screw state determination device, it is preferable to further include a processing unit that calculates third vibration information obtained by multiplying the second vibration information by the first vibration information.

[0024] As a result, the third vibration information is obtained in which the noise components that are uncorrelated between the first vibration information and the second vibration information are relatively reduced.

[0025] As a desirable aspect of the device for determining a state of a ball screw, it is preferable that the determination unit determines the degree of wear of the ball screw based on a statistical value of the third vibration information.

[0026] This can improve the noise resistance and increase the accuracy of determining the degree of wear of the ball screw.

[0027] As a preferred embodiment of the ball screw state determination device, it is preferable to further include a processing unit that calculates a degree of coincidence between the second vibration information and the first vibration information.

[0028] In addition, as a desirable aspect of the device for determining a state of a ball screw, it is preferable that the determination unit determines the degree of wear of the ball screw based on the degree of coincidence.

[0029] This can improve the noise resistance and increase the accuracy of determining the degree of wear of the ball screw.

[0030] A method for determining the state of a ball screw involved in one embodiment of the present invention includes the following steps: a first step, generating first vibration information based on a vibration signal obtained in a first period and when the ball screw is working, the first vibration information representing the relationship between the nut position of the ball screw and the frequency-vibration level characteristic that changes according to the nut position; a second step, generating second vibration information based on a vibration signal obtained in a second period that is later than the first period and when the ball screw is working, the second vibration information representing the relationship between the nut position of the ball screw and the frequency-vibration level characteristic that changes according to the nut position; and a third step, performing state determination processing of the ball screw based on the first vibration information and the second vibration information.

[0031] In the above structure, the second vibration information generated based on the vibration signal acquired during the second period for implementing the state judgment of the ball screw is applied with the first vibration information generated based on the vibration signal acquired during the first period in the state assumed to be normally applied preload, thereby improving the noise resistance.

[0032] As an ideal aspect of the method for determining the state of the ball screw, it is preferable that, in the first step, averaging processing of a plurality of first vibration information acquired in the first period is performed.

[0033] Thus, the first vibration information is obtained after the non-steady continuous spectrum is removed.

[0034] As an ideal aspect of the method for determining the state of the ball screw, it is preferred that, in the first step, first vibration information is generated by removing a periodic vibration component of the vibration signal acquired during the first period.

[0035] Thus, the first vibration information is obtained after the discrete spectrum is removed.

[0036] As an ideal aspect of the method for determining the state of the ball screw, it is preferable that, in the first step, averaging processing of a plurality of first vibration information acquired in the first period is performed.

[0037] Thus, the first vibration information is obtained after the non-steady continuous spectrum is removed.

[0038] As an ideal aspect of the method for determining the state of the ball screw, it is preferable that, in the second step, averaging processing of a plurality of pieces of second vibration information acquired in the second period is performed.

[0039] Thus, the second vibration information is obtained after the non-steady continuous spectrum is removed.

[0040] As an ideal aspect of the method for determining the state of the ball screw, it is preferred that, in the second step, second vibration information is generated by removing a periodic vibration component of the vibration signal acquired during the second period.

[0041] Thus, the second vibration information is obtained after the discrete spectrum is removed.

[0042] As an ideal aspect of the method for determining the state of the ball screw, it is preferable that, in the third step, third vibration information obtained by multiplying the second vibration information by the first vibration information is calculated.

[0043] As a result, the third vibration information is obtained in which the noise components that are uncorrelated between the first vibration information and the second vibration information are relatively reduced.

[0044] As an ideal aspect of the method for determining the state of a ball screw, it is preferred that, in the third step, the degree of wear of the ball screw is determined based on a statistical value of the third vibration information.

[0045] This can improve the noise resistance and increase the accuracy of determining the degree of wear of the ball screw.

[0046] As an ideal aspect of the method for determining the state of a ball screw, it is preferred that, in the third step, the degree of consistency between the second vibration information and the first vibration information is calculated.

[0047] In addition, as an ideal aspect of the method for determining the state of the ball screw, it is preferable that, in the third step, the degree of wear of the ball screw is determined based on the degree of coincidence.

[0048] This can improve the noise resistance and increase the accuracy of determining the degree of wear of the ball screw.

[0049] Effects of the Invention

[0050] According to the present invention, a state determination device and a state determination method of a ball screw capable of improving noise resistance are obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a diagram showing an example of a schematic configuration of a ball screw state determination system.

[0052] Figure 2 This is a block diagram showing an example of a state determination device for a ball screw according to an embodiment.

[0053] Figure 3A It is a schematic diagram showing an example of vibration information generated by the vibration information generating unit.

[0054] Figure 3B It is a schematic diagram showing an example of vibration information generated by the vibration information generating unit.

[0055] Figure 4 This is a flowchart showing an example of the first vibration information acquisition process according to the first embodiment.

[0056] Figure 5 This is a flowchart showing an example of the second vibration information acquisition process according to the first embodiment.

[0057] Figure 6 This is a flowchart showing an example of the state determination process according to the first embodiment.

[0058] Figure 7 This is a flowchart showing an example of the state determination process according to the modification of the first embodiment.

[0059] Fig. 8A It is a schematic diagram showing an example of vibration information generated by the vibration information generating unit.

[0060] Figure 8B It is a schematic diagram showing an example of vibration information generated by the vibration information generating unit.

[0061] Fig. 9 This is a flowchart showing an example of the first vibration information acquisition process according to the second embodiment.

[0062] Fig.10 This is a schematic diagram showing an example of first vibration information generated by the first vibration information acquisition process involved in the second embodiment.

[0063] Fig.11 This is a flowchart showing an example of the first vibration information acquisition process according to the third embodiment.

[0064] Fig.12 This is a schematic diagram showing an example of first vibration information generated by the first vibration information acquisition process involved in the third embodiment.

[0065] Fig.13 This is a flowchart showing an example of the first vibration information acquisition process according to the modification of the third embodiment.

[0066] Fig.14 This is a schematic diagram showing an example of first vibration information generated by the first vibration information acquisition process according to the modification of the third embodiment.

[0067] Fig.15 This is a flowchart showing an example of the second vibration information acquisition process according to the fourth embodiment.

[0068] Fig.16 This is a flowchart showing an example of the second vibration information acquisition process according to the modification of the fourth embodiment. DETAILED DESCRIPTION

[0069] Hereinafter, the mode for implementing the invention (hereinafter referred to as the embodiment) will be described in detail with reference to the accompanying drawings. In addition, the present invention is not limited by the following embodiments. In addition, the constituent elements of the following embodiments include elements that can be easily thought of by those skilled in the art, substantially the same elements, and elements of the so-called equivalent scope. Furthermore, the constituent elements disclosed in the following embodiments can be appropriately combined.

[0070] Figure 1 1 is a diagram showing an example of a schematic configuration of a state determination system of a ball screw. A ball screw 1 includes a screw shaft 11 and a nut 12 slidably fitted to the screw shaft 11 via a plurality of rolling elements (not shown).

[0071] Both ends of the screw shaft 11 are rotatably supported by bearings 13 and 14, and one end side ( Figure 1 The nut 12 is connected to the output shaft of the driving motor 15 as the screw shaft 11 rotates. Figure 1 The distance between the A end and the B end shown in the figure is along the axial direction of the screw shaft 11 ( Figure 1 Direction of the arrow shown).

[0072] In the present disclosure, the state determination device 2 of the ball screw 1 involved in the embodiment performs state determination of the ball screw 1 based on the vibration signal obtained during the operation of the ball screw 1. When performing the state determination of the ball screw 1 involved in the embodiment, the state determination device 2 outputs the drive control instruction and the rotation control instruction of the motor 15 to the drive control device 3. The drive control device 3 drives the motor 15 to operate the ball screw 1 based on the control instruction from the state determination device 2 so that the nut 12 moves over the entire area of ​​the screw shaft 11. The drive control device 3 outputs the rotation speed of the motor 15 to the state determination device 2, in other words, outputs the rotation speed of the screw shaft 11 of the ball screw 1.

[0073] Figure 2 1 is a block diagram showing an example of a state determination device for a ball screw according to an embodiment of the present invention. Figure 2 As shown, the state determination device 2 of the ball screw 1 according to the embodiment includes a vibration information generation unit 201, a determination unit 202, a storage unit 203, and a processing unit 204. The state determination device 2 receives a vibration signal acquired by the vibration sensor 21 during the operation of the ball screw 1.

[0074] The vibration sensor 21 is provided, for example, at Figure 1 The nut 12 of the ball screw 1 shown. In the present disclosure, regarding the vibration sensor 21, an acceleration sensor such as an acceleration collector is exemplified. The acceleration detection direction of the vibration sensor 21 can be the axial direction of the screw shaft 11 ( Figure 1 The vibration sensor 21 may be in the direction of the arrow shown in the figure, or in the direction orthogonal to the axial direction of the screw shaft 11. In addition, the vibration sensor 21 may be set at a position that can detect the vibration of the ball screw 1 when it is working, and is not limited to the nut 12. Furthermore, the vibration sensor 21 is not limited to an acceleration sensor. The vibration sensor 21 may also be, for example, a displacement sensor, a microphone or other sound pressure sensor.

[0075] The vibration information generating unit 201 generates vibration information indicating a relationship between a nut position of the ball screw and a frequency-vibration level characteristic that changes according to the nut position, based on a vibration signal detected by the vibration sensor 21 . Figure 3A and Figure 3B is a schematic diagram showing an example of vibration information generated by the vibration information generating unit. Figure 3A and Figure 3B In FIG. 1 , the horizontal axis represents the position P of the nut 12 (hereinafter, also simply referred to as “nut position”), and the vertical axis represents the frequency f. In the present disclosure, the frequency range of the vibration information is set to be within a predetermined range of, for example, 10 Hz to 10 kHz.

[0076] The natural vibration frequency of the spectrum of the vibration signal acquired during the operation of the ball screw 1 varies according to the nut position. Figure 3A and Figure 3B In the figure, there are illustrated frequency f1 corresponding to the first-order natural vibration frequency in the main natural mode between nut positions NA, frequency f2 corresponding to the second-order natural vibration frequency in the main natural mode between nut positions NA, frequency f1' corresponding to the first-order natural vibration frequency in the main natural mode between nut positions NB, and frequency f2' corresponding to the second-order natural vibration frequency in the main natural mode between nut positions NB.

[0077] Based on the vibration information generated by the vibration information generating unit 201 , the degree of wear of the ball screw 1 can be understood.

[0078] The vibration level of each frequency defined by the magnitude of the spectrum varies according to the magnitude of the preload applied to the ball screw 1. Specifically, Figure 3A For example, vibration information obtained in a state where a preload is normally applied immediately after the ball screw 1 is manufactured is illustrated. Figure 3B The vibration information acquired in a state where the preload of the ball screw 1 decreases due to deformation of the raceway surface caused by the movement of the rolling element and wear of the rolling element is exemplified.

[0079] exist Figure 3A and Figure 3B In the example, the vibration level of each frequency defined by the size of the spectrum is indicated by using the edge lines shown in the vibration information, in other words, by using the thickness of the line indicating the frequency change corresponding to each natural vibration frequency. Figure 3A and Figure 3B In FIG. 1 , the density of the shadow is used to indicate the amount and size of the noise component that is unrelated to each natural vibration shown in the vibration information. Figure 3B The vibration information shown represents the relative Figure 3A This is an example in which the vibration level of each natural vibration is relatively small with respect to the vibration information shown, and the vibration level of the noise component unrelated to each natural vibration is relatively large.

[0080] When the preload is normally applied, the vibration level of each natural vibration is high, and the frequency change corresponding to each natural vibration frequency is clearly shown (refer to Figure 3A ).

[0081] On the other hand, as the preload of the ball screw 1 decreases, the difference between the vibration level of each natural vibration and the noise component that is independent of each natural vibration becomes smaller, and the frequency change corresponding to each natural vibration frequency decreases (refer to Figure 3B If the vibration information in which the vibration level of each natural vibration is reduced is used to determine the degree of wear of the ball screw 1, the determination accuracy will decrease.

[0082] In the present disclosure, the state determination device 2 of the ball screw 1 determines the degree of wear of the ball screw 1 using first vibration information previously acquired in a state where preload is normally applied and second vibration information acquired during state determination.

[0083] Specifically, the state determination device 2 of the ball screw 1 first acquires the first vibration information during the first period in which the preload can be assumed to be normally applied (first vibration information acquisition process), and acquires the second vibration information during the second period in which the state determination of the ball screw 1 is implemented (second vibration information acquisition process). Furthermore, the state determination device 2 uses the first vibration information acquired during the first period and the second vibration information acquired during the second period to determine the degree of wear of the ball screw 1 (state determination process).

[0084] In addition, in the present disclosure, the state change caused by the damage and wear caused by the use of the ball screw 1 is used as the judgment object. As the first period for obtaining the first vibration information, the period from the start of the use of the ball screw 1 to the time of about 1 / 10 of the period assumed to be the use period of the ball screw 1 is set as the period in which the state of normal preload is assumed to be maintained. Specifically, for example, in the use of replacing the ball screw 1 every year, it is preferred to set the first period to about one month, and in the use of replacing the ball screw 1 every ten years, it is preferred to set the first period to about one year.

[0085] Next, a specific process that can improve the noise resistance and increase the accuracy of determining the degree of wear of the ball screw 1 will be described.

[0086] (Implementation Method 1)

[0087] Figure 4 This is a flowchart showing an example of the first vibration information acquisition process according to the first embodiment.

[0088] The state determination device 2 operates the ball screw 1 during a first period in which the preload is assumed to be normally applied, and acquires the first vibration information. Figure 1 In the state determination system of the ball screw 1 shown, the state determination device 2 outputs a drive control command and a rotation control command of the motor 15 to the drive control device 3. The drive control device 3 drives the motor 15 based on the control command from the state determination device 2 to operate the ball screw 1.

[0089] exist Figure 4In the first vibration information acquisition process involved in the illustrated embodiment 1, the vibration information generating unit 201 acquires the vibration signal obtained by digitizing the AD conversion processing unit (not shown) (step S110), and generates the first vibration information representing the relationship between the nut position of the ball screw 1 and the vibration level of each frequency based on the acquired vibration signal (step S120).

[0090] The vibration information generation unit 201 stores the first vibration information generated in step S120 in the storage unit 203 (step S130 ), and ends the first vibration information acquisition process.

[0091] Figure 5 This is a flowchart showing an example of the second vibration information acquisition process according to the first embodiment.

[0092] First, in a second period of performing state determination of the ball screw 1 after the first period in which the first vibration information is generated, the state determination device 2 operates the ball screw 1 and obtains the second vibration information. Figure 1 In the state determination system of the ball screw 1 shown, the state determination device 2 outputs a drive control command and a rotation control command of the motor 15 to the drive control device 3. The drive control device 3 drives the motor 15 based on the control command from the state determination device 2 to operate the ball screw 1.

[0093] The second vibration information acquisition process may be executed, for example, when the ball screw 1 is started, or may be executed every predetermined time or every predetermined time.

[0094] exist Figure 5 In the second vibration information acquisition process involved in the illustrated embodiment 1, the vibration information generating unit 201 acquires the vibration signal obtained by digitizing the AD conversion processing unit (not shown) (step S210), and generates the second vibration information representing the relationship between the nut position of the ball screw 1 and the vibration level of each frequency based on the acquired vibration signal (step S220).

[0095] The vibration information generation unit 201 stores the second vibration information generated in step S220 in the storage unit 203 (step S230 ), and ends the second vibration information acquisition process.

[0096] Next, the state determination device 2 uses the first vibration information acquisition process (see Figure 4 ) and the first vibration information generated by the second vibration information acquisition process (refer to Figure 5 ) to perform state determination processing of the ball screw 1. Figure 6 This is a flowchart showing an example of the state determination process according to the first embodiment.

[0097] exist Figure 6 In the state determination process according to the first embodiment shown, first, the processing unit 204 reads out the first vibration information and the second vibration information stored in the storage unit 203 (step S301 ).

[0098] like Figure 3A and Figure 3B As shown, the first vibration information and the second vibration information are information that holds the vibration value V(P, f) of each coordinate (P, f) defined by the nut position (P) and frequency (f) of the ball screw 1. Regarding the first vibration information generated based on the vibration signal acquired during the first period assumed to be in a state where the preload is normally applied, for example, Figure 3A As shown in FIG. 1 , the vibration level at each natural vibration frequency is high, and the frequency change corresponding to each natural vibration frequency is clearly shown. In contrast, regarding the second vibration information generated based on the vibration signal obtained during the second period of the state determination of the ball screw 1, for example, Figure 3B Assuming that the vibration level at each natural frequency is low as shown, the difference between the vibration level corresponding to each natural frequency and the noise component that appears regardless of each natural frequency becomes small.

[0099] In the present disclosure, the state determination device 2 determines the degree of wear of the ball screw 1 using the first vibration information acquired during the first period and the second vibration information acquired during the second period as described above.

[0100] Specifically, in Embodiment 1, the processing unit 204 generates third vibration information by applying the first vibration information to the second vibration information (step S302), and outputs it to the determination unit 202. More specifically, the processing unit 204 multiplies the second vibration information by the first vibration information to calculate the third vibration information.

[0101] More specifically, the processing unit 204 multiplies the vibration values ​​of the corresponding coordinates between the first vibration information and the second vibration information to set the vibration values ​​of the coordinates of the third vibration information. The vibration value at the coordinate (P, f) of the first vibration information is set to V1 (P, f), the vibration value at the coordinate (P, f) of the second vibration information is set to V2 (P, f), and the vibration value V3 (P, f) at the coordinate (P, f) of the third vibration information is expressed by the following formula (1).

[0102] V3(P, f)=V2(P, f)×V1(P, f)…(1)

[0103] Thus, the third vibration information is obtained in which the noise component that is uncorrelated between the first vibration information and the second vibration information is relatively reduced with respect to the vibration value of each natural vibration component.

[0104] The determination unit 202 determines the degree of wear of the ball screw 1 using the third vibration information generated by the processing unit 204 .

[0105] Specifically, in Embodiment 1, the determination unit 202 performs statistical value calculation processing (step S303) on the third vibration information generated by the processing unit 204. More specifically, for example, the effective value Vrms of the vibration value at each coordinate of the third vibration information is calculated.

[0106] The determination unit 202 performs threshold determination processing on the statistical value calculated in step S303 to determine the state of the ball screw 1. Specifically, the determination unit 202 determines, for example, whether the effective value Vrms calculated in step S303 is greater than a pre-held threshold value Vth (step S304). The threshold value Vth is set to a lower limit value of the effective value that can be assumed to be normal for the ball screw 1 through simulation.

[0107] When the effective value Vrms statistic is greater than or equal to the threshold value Vth (Vrms ≥ Vth, step S304; Yes), the determination unit 202 determines that the ball screw 1 is normal (step S305), outputs the determination result (step S307), and ends the state determination process.

[0108] When the effective value Vrms statistic is lower than the threshold value Vth (Vrms<Vth, step S304; No), the determination unit 202 determines that an abnormality has occurred in the ball screw 1 (step S306), outputs the determination result (step S307), and ends the state determination process.

[0109] In the processing involved in the above-mentioned embodiment 1, the first vibration information generated based on the vibration signal obtained during the first period in which the preload is assumed to be normally applied is maintained, and the third vibration information obtained by applying the first vibration information to the second vibration information generated based on the vibration signal obtained during the second period in which the state determination of the ball screw 1 is implemented is generated. More specifically, the processing unit 204 multiplies the second vibration information by the first vibration information to calculate the third vibration information. Then, a statistical value calculation process is performed on the generated third vibration information, and the calculated statistical value (for example, an effective value) is used as information indicating the degree of loss of the ball screw 1. As a result, the noise resistance can be improved, and the accuracy of determining the degree of loss of the ball screw 1 can be improved.

[0110] (Variation Example)

[0111] Figure 71 is a flowchart showing an example of a state determination process involved in a modified example of Implementation 1. In addition, the first vibration information acquisition process and the second vibration information acquisition process involved in the modified example of Implementation 1 are the same as those in Implementation 1 above, so the detailed description here is omitted. In addition, here, sometimes the process different from Implementation 1 is described in detail and the detailed description of the process the same as Implementation 1 is omitted.

[0112] In the state determination process according to the modification of the first embodiment, the processing unit 204 performs a calculation process (step S303a) of the degree of consistency S of the first vibration information and the second vibration information read out in step S301, instead of Figure 6 The third vibration information generation process (step S302) and the statistical value calculation process (step S303) are shown.

[0113] Specifically, the processing unit 204 uses a template matching method such as SSD (Sum of Squared Difference) or SAD (Sum of Absolute Difference) to calculate the consistency S between the first vibration information and the second vibration information. More specifically, the first vibration information is set as a template image, and the second vibration information is set as a search image to calculate the consistency (similarity) between the second vibration information and the first vibration information. In addition, it can be considered that when SSD or SAD is used as the template matching method, the smaller the value (consistency S) calculated by the processing unit 204 in step S303a, the higher the consistency (similarity) between the second vibration information and the first vibration information, and the larger the value (consistency S) calculated by the processing unit 204 in step S303a, the lower the consistency (similarity) between the second vibration information and the first vibration information.

[0114] In the state determination process according to the modification of the first embodiment, the determination unit 202 determines the degree of wear of the ball screw 1 using the degree of coincidence S calculated by the processing unit 204 .

[0115] Specifically, in the modified example of the first embodiment, the determination unit 202 performs a threshold determination process on the degree of coincidence S calculated by the processing unit 204 to determine the state of the ball screw 1 .

[0116] Fig. 8A and Figure 8B It is a schematic diagram showing an example of vibration information generated by the vibration information generating unit.

[0117] exist Fig. 8A, the second vibration information calculated by the processing unit 204 is exemplified when the degree of agreement S with the first vibration information acquired during the first period in which it can be assumed that the preload is normally applied is less than the threshold value Sth. Figure 8B , the second vibration information calculated by the processing unit 204 is illustrated when the consistency S with the first vibration information acquired during the first period in which the preload can be assumed to be normally applied exceeds the threshold value Sth. The threshold value Sth is set to the upper limit value of the consistency that can assume that the ball screw 1 is normal through simulation.

[0118] As described above, the vibration information includes not only the vibration spectrum corresponding to each natural vibration, but also the vibration spectrum unrelated to each natural vibration. Hereinafter, the vibration spectrum corresponding to each natural vibration is also referred to as the "steady-state continuous spectrum". Fig. 8A and Figure 8B The vibration spectrum component shown on the dotted line is also called "non-steady-state continuous spectrum". Fig. 8A and Figure 8B The point-like vibration spectrum components that appear discretely in the ball screw 1 are also called "discrete spectrum". Generally speaking, the non-steady-state continuous spectrum is a vibration component that appears regardless of the degree of loss of the ball screw 1. In addition to the periodic vibration components generated by the drive of the ball screw 1, the discrete spectrum also includes mechanical noise components generated at the production site, etc.

[0119] As the preload of the ball screw 1 decreases, the vibration spectrum caused by the loss of the ball screw 1 increases, and the degree of coincidence S calculated by the processing unit 204 in step S303a increases.

[0120] Specifically, in the modification of the first embodiment, the determination unit 202 determines whether the degree of match S calculated in step S303 a is equal to or less than a threshold value Sth stored in advance (step S304 a ), for example.

[0121] When the degree of coincidence S is equal to or less than the threshold value Sth (S≤Sth, step S304a; YES), the determination unit 202 determines that the ball screw 1 is normal (step S305), outputs the determination result (step S307), and ends the state determination process.

[0122] When the degree of coincidence S exceeds the threshold value Sth (S>Sth, step S304a; No), the determination unit 202 determines that an abnormality has occurred in the ball screw 1 (step S306), outputs the determination result (step S307), and ends the state determination process.

[0123] In addition, in the variation of the above-mentioned embodiment 1, SSD and SAD are exemplified as template matching methods, but are not limited to this. For example, the consistency can also be calculated by normalized cross-correlation (NCC: Normalized Cross-Correlation, ZNCC: Zero-mean Normalized Cross-Correlation) or the like. In addition, it can be considered that when NCC and ZNCC are used as template matching methods, the closer the value is to 1, the higher the consistency (similarity). As the determination processing of the determination unit 202, the best determination method can be adopted according to the template matching method of the processing unit 204 in step S303a.

[0124] In the processing involved in the modified example of the above-mentioned embodiment 1, the consistency (similarity) between the second vibration information and the first vibration information is used as information representing the degree of loss of the ball screw 1. In the modified example of this embodiment 1, the noise resistance can be improved in the same way as in embodiment 1, and the accuracy of determining the degree of loss of the ball screw 1 can be improved.

[0125] (Implementation Method 2)

[0126] Fig. 9 1 is a flowchart showing an example of the first vibration information acquisition process involved in Implementation 2. In addition, the second vibration information acquisition process and state determination process involved in Implementation 2 are the same as those in Implementation 1 above, so the detailed description is omitted here. Specifically, in Implementation 2, either the second vibration information acquisition process and state determination process described in Implementation 1 are adopted or the second vibration information acquisition process and state determination process are adopted. Figure 6 The state determination processing shown in the figure (using the statistical value of the third vibration information obtained by multiplying the first vibration information by the second vibration information to determine the degree of wear of the ball screw 1) can also be performed by using Figure 7 The state determination processing shown (processing for determining the degree of loss of the ball screw 1 using the consistency (similarity) between the second vibration information and the first vibration information). In addition, here, sometimes the processing different from the first embodiment is described in detail and the detailed description of the processing similar to the first embodiment is omitted.

[0127] exist Fig. 9 In the first vibration information acquisition process according to the second embodiment shown, the vibration information generation unit 201 performs a noise component removal process on the vibration signal acquired in step S110 (step S111 ).

[0128] Specifically, in step S111 , the vibration information generating unit 201 removes the periodic vibration components of the vibration signal as noise components using, for example, a Cepstrum Pre-Whitening (CPW) process or a Cepstrum Editing Process (CEP) process including CPW.

[0129] Then, the vibration information generation unit 201 generates first vibration information based on the vibration signal from which the noise component has been removed (step S120 a ), stores the first vibration information in the storage unit 203 (step S130 ), and ends the first vibration information acquisition process.

[0130] Fig.10 2 is a schematic diagram showing an example of first vibration information generated by the first vibration information acquisition process involved in Implementation 2. By performing noise component removal processing (step S111) on the first vibration information acquired during the first period assumed to be in a state where preload is normally applied, as shown in FIG. Fig.10 As shown in Fig. 8A and Figure 8B The first vibration information is obtained by removing the discrete spectrum described in the above. Thus, compared with the first embodiment, the noise resistance can be further improved, and the accuracy of determining the degree of wear of the ball screw 1 can be improved.

[0131] (Implementation method 3)

[0132] Fig.11 1 is a flowchart showing an example of the first vibration information acquisition process involved in Implementation 3. In addition, the second vibration information acquisition process and state determination process involved in Implementation 3 are the same as those in Implementation 1 above, so the detailed description here is omitted. Specifically, in Implementation 3, either the second vibration information acquisition process and state determination process described in Implementation 1 are used or the second vibration information acquisition process and state determination process are used. Figure 6 The state determination processing shown in the figure (using the statistical value of the third vibration information obtained by multiplying the first vibration information by the second vibration information to determine the degree of wear of the ball screw 1) can also be performed by using Figure 7 The state determination processing shown (processing for determining the degree of loss of the ball screw 1 using the consistency (similarity) between the second vibration information and the first vibration information). In addition, here, sometimes the processing different from the first embodiment is described in detail and the detailed description of the processing similar to the first embodiment is omitted.

[0133] exist Fig.11In the first vibration information acquisition process involved in the third embodiment shown, the state determination device 2 acquires a plurality of first vibration information in a first period in which a preload is assumed to be normally applied. Specifically, the state determination device 2 resets the number of acquisitions of the first vibration information n (n = 0, step S101), counts the number of acquisitions of the first vibration information n incrementally (n = n + 1, step S102), operates the ball screw 1, and acquires the first vibration information. In the third embodiment, the first vibration information is acquired more than ten times (N ≥ 10) in the first period until about 1 / 10 of the period assumed to be the operation period of the ball screw 1 has passed.

[0134] The vibration information generating unit 201 obtains the vibration signal digitized by the AD conversion processing unit (not shown) (step S110), and generates first vibration information representing the relationship between the nut position of the ball screw 1 and the vibration level of each frequency based on the obtained vibration signal (step S120).

[0135] Next, the vibration information generation unit 201 performs a normalization process on the first vibration information generated in step S120 (step S123 ).

[0136] Specifically, the vibration information generating unit 201 performs a standardization process on the first vibration information generated in step S120. More specifically, the vibration information generating unit 201 sets the average value of the first vibration information to "0" and the standard deviation (or variance) to "1".

[0137] Alternatively, the vibration information generating unit 201 may perform normalization processing on the first vibration information generated in step S120 instead of standardization processing. More specifically, the vibration information generating unit 201 may set the minimum value of the first vibration information to "-1" (or "0") and the maximum value to "1".

[0138] Then, the vibration information generating unit 201 stores the standardized first vibration signal in the storage unit 203 (step S130a), and determines whether the number of times n of obtaining the first vibration information is N (n=N, step S131). When the number of times n of obtaining the first vibration information is less than N (n<N, step S131; "No"), the process returns to step S102, the number of times n of obtaining the first vibration information is incremented (n=n+1, step S102), and the process after step S110 is repeated.

[0139] The processing after step S110 may be performed, for example, when the ball screw 1 is started, or may be performed, for example, every time a predetermined moment or a predetermined time has passed. It is preferred to set the execution interval of the processing after step S110 so that step S131 can be satisfied within the first period defined as the period for obtaining the first vibration information. Alternatively, when the first period has passed before step S131 is satisfied, it is preferred to extend the first period until the number of times n of obtaining the first vibration information reaches N.

[0140] After acquiring the N first vibration information, the vibration information generating unit 201 reads the N first vibration information stored in the storage unit 203 (step S132), and performs averaging processing on the read N first vibration information (step S133). More specifically, the vibration information generating unit 201 calculates the average value of the vibration value of each coordinate corresponding to the N first vibration information.

[0141] Fig.12 1 is a schematic diagram showing an example of first vibration information generated by the first vibration information acquisition process involved in Implementation Example 3. A plurality of first vibration information acquired during the first period assuming that the preload is normally applied is respectively standardized, and an averaging process is performed on the plurality of first vibration information after the standardization, thereby, as shown in FIG. Fig.12 As shown in Fig. 8A and Figure 8B The first vibration information is obtained by removing the non-steady continuous spectrum described in . Thus, compared with the first embodiment, the noise resistance can be further improved, and the accuracy of determining the degree of wear of the ball screw 1 can be improved.

[0142] (Variation Example)

[0143] Fig.13 This is a flowchart showing an example of the first vibration information acquisition process according to the modification of the third embodiment. Fig.14 Schematic diagram showing an example of first vibration information generated by the first vibration information acquisition process involved in the variant of Implementation Example 3. In addition, the second vibration information acquisition process and the state determination process involved in the variant of Implementation Example 3 are the same as those in Implementation Example 3, so the detailed description here is omitted. In addition, here, sometimes the process different from Implementation Example 3 is described in detail and the detailed description of the process the same as Implementation Example 3 is omitted.

[0144] In the first vibration information acquisition process according to the modification of the third embodiment, the noise component removal process (step S111) of the second embodiment is combined with the first vibration information acquisition process according to the third embodiment. Fig.14 As shown in Fig. 8A and Figure 8B The first vibration information is obtained by removing the discrete spectrum and the non-steady continuous spectrum described in the above. Thus, compared with the second and third embodiments, the noise resistance can be further improved, and the accuracy of determining the degree of wear of the ball screw 1 can be improved.

[0145] (Implementation 4)

[0146] Fig.15 1 is a flowchart showing an example of the second vibration information acquisition process involved in Implementation 4. In addition, the first vibration information acquisition process and state determination process involved in Implementation 4 are the same as those in Implementation 3, so the detailed description here is omitted. Specifically, in Implementation 4, it is possible to adopt the method described in Implementation 1. Figure 6 The state determination processing shown in the figure (using the statistical value of the third vibration information obtained by multiplying the first vibration information by the second vibration information to determine the degree of wear of the ball screw 1) can also be performed by using Figure 7 The state determination processing shown (processing for determining the degree of loss of the ball screw 1 using the consistency (similarity) between the second vibration information and the first vibration information). In addition, here, sometimes the processing different from the third embodiment is described in detail and the detailed description of the same processing as the third embodiment is omitted.

[0147] exist Fig.15 In the second vibration information acquisition process involved in the embodiment 4 shown, the state determination device 2 operates the ball screw 1 in the second period of implementing the state determination of the ball screw 1 after the first period of generating the first vibration information, and obtains a plurality of second vibration information. Specifically, the state determination device 2 resets the number of acquisitions m of the second vibration information (m=0, step S201), counts the number of acquisitions m of the second vibration information incrementally (m=m+1, step S202), and obtains the second vibration information. For example, the number of acquisitions M of the second vibration information in the second period is set to the same number as the number of acquisitions N of the first vibration information. Specifically, the second vibration information is obtained, for example, more than ten times (M≥10) in the second period.

[0148] The vibration information generating unit 201 obtains the vibration signal digitized by the AD conversion processing unit (not shown) (step S210), and generates second vibration information representing the relationship between the nut position of the ball screw 1 and the vibration level of each frequency based on the obtained vibration signal (step S220).

[0149] Next, the vibration information generation unit 201 performs normalization processing on the second vibration information generated in step S220 (step S223 ).

[0150] Specifically, the vibration information generating unit 201 performs a standardization process on the second vibration information generated in step S220. More specifically, the vibration information generating unit 201 sets the average value of the second vibration information to "0" and the standard deviation (or variance) to "1".

[0151] Alternatively, the vibration information generating unit 201 may perform normalization processing on the first vibration information generated in step S220 instead of standardization processing. More specifically, the vibration information generating unit 201 may set the minimum value of the second vibration information to "-1" (or "0") and the maximum value to "1".

[0152] Preferably, the standardization processing method of the second vibration information in the second vibration information acquisition process involved in the fourth embodiment is the same as the standardization processing method of the first vibration information. Fig.11 or Fig.13 In the case where the first vibration information is standardized in step S123 of the present invention, it is preferred that the second vibration information is standardized in the same manner in the second vibration information acquisition process (step S223). Fig.11 or Fig.13 In the case where the normalization processing of the first vibration information is performed in the step S123 of the acquisition process, it is preferred that the normalization processing of the second vibration information is also performed in the second vibration information acquisition process (step S223).

[0153] Then, the vibration information generating unit 201 stores the standardized second vibration signal in the storage unit 203 (step S230a), and determines whether the number of times m of obtaining the second vibration information is M (m=M, step S231). When the number of times m of obtaining the second vibration information is less than M (m<M, step S231; "No"), the process returns to step S202, counts the number of times m of obtaining the second vibration information incrementally (m=m+1, step S202), and repeats the process after step S210.

[0154] After acquiring the M second vibration information, the vibration information generating unit 201 reads the M second vibration information stored in the storage unit 203 (step S232), and performs averaging processing on the read M second vibration information (step S233). More specifically, the vibration information generating unit 201 calculates the average value of the vibration value of each coordinate corresponding to the M second vibration information.

[0155] In the processing involved in the above-mentioned embodiment 4, the plurality of second vibration information obtained by performing multiple acquisitions are respectively standardized, and the plurality of second vibration information after the standardization is averaged, thereby obtaining the first vibration information in the same manner. Fig. 8A and Figure 8B The highly accurate second vibration information is obtained by removing the non-steady continuous spectrum described in the above. Thus, compared with the third embodiment, the noise resistance can be further improved, and the accuracy of determining the degree of wear of the ball screw 1 can be further improved.

[0156] (Variation Example)

[0157] Fig.16 1 is a flowchart showing an example of the second vibration information acquisition process involved in the variant of Implementation Example 4. In addition, the first vibration information acquisition process and the state determination process involved in the variant of Implementation Example 4 are the same as those in Implementation Example 4, so the detailed description here is omitted. In addition, here, sometimes the process different from the second vibration information acquisition process involved in Implementation Example 4 is described in detail and the detailed description of the process same as Implementation Example 4 is omitted.

[0158] In the second vibration information acquisition process involved in the variant of the fourth embodiment, the second vibration information acquisition process involved in the fourth embodiment is combined with the noise component removal process (step S211) similar to the noise component removal process (step S111) for the first vibration information in the second embodiment. Thus, the noise component in the first vibration information is removed in the same manner as the first vibration information obtained by the first vibration information acquisition process involved in the variant of the third embodiment. Fig. 8A and Figure 8B The discrete spectrum and the non-steady continuous spectrum described in the above can be used to obtain the second vibration information with higher accuracy. Thus, compared with the fourth embodiment, the noise resistance can be further improved, and the accuracy of determining the degree of wear of the ball screw 1 can be further improved.

[0159] As described above, according to the state determination device 2 and the state determination method of the ball screw 1 according to each embodiment and its modified example of the present disclosure, it is possible to improve noise resistance and improve the accuracy of determining the degree of wear of the ball screw 1 .

[0160] Alternatively, as the vibration information, for example, a method may be adopted in which binary information is used in which a vibration value equal to or greater than a predetermined value is set to “1” and a vibration value less than the predetermined value is set to “0”.

[0161] Description of Reference Numerals

[0162] 1: ball screw; 2: state determination device; 3: drive control device; 11: screw shaft; 12: nut; 13, 14: bearings; 15: motor; 21: vibration sensor; 201: vibration information generating unit; 202: determination unit; 203: storage unit; 204: processing unit.

Claims

1. A ball screw state determination device, comprising: a vibration information generating unit that generates vibration information based on a vibration signal acquired by a vibration sensor when the ball screw is operating, the vibration information indicating a relationship between a nut position of the ball screw and a frequency-vibration level characteristic that varies according to the nut position; and A determination unit performs state determination processing of the ball screw based on the first vibration information and the second vibration information, wherein: The first vibration information is vibration information generated based on a vibration signal acquired in a first period, and the second vibration information is vibration information acquired in a second period later than the first period.

2. The ball screw state determination device according to claim 1, wherein: The vibration information generation unit performs averaging processing of a plurality of first vibration information acquired in the first period.

3. The state determination device of the ball screw according to claim 1, wherein: The vibration information generating unit generates first vibration information by removing a periodic vibration component of the vibration signal acquired in the first period.

4. The state determination device of the ball screw according to claim 3, wherein: The vibration information generation unit performs averaging processing of a plurality of first vibration information acquired in the first period.

5. The state determination device of the ball screw according to claim 4, wherein: The vibration information generation unit performs averaging processing of a plurality of second vibration information acquired in the second period.

6. The state determination device of the ball screw according to claim 5, wherein: The vibration information generating unit generates second vibration information by removing a periodic vibration component of the vibration signal acquired during the second period.

7. The state determination device for a ball screw according to any one of claims 1 to 6, wherein: The device further includes a processing unit that calculates third vibration information obtained by multiplying the second vibration information by the first vibration information.

8. The state determination device of the ball screw according to claim 7, wherein: The determination unit determines a degree of wear of the ball screw based on a statistical value of the third vibration information.

9. The state determination device for a ball screw according to any one of claims 1 to 6, wherein: The device further includes a processing unit that calculates a degree of consistency between the second vibration information and the first vibration information.

10. The state determination device of the ball screw according to claim 9, wherein: The determination unit determines a degree of wear of the ball screw based on the degree of coincidence.

11. A method for determining the state of a ball screw, comprising the following steps: A first step is to generate first vibration information based on a vibration signal acquired during a first period and when the ball screw is operating, wherein the first vibration information represents a relationship between a nut position of the ball screw and a frequency-vibration level characteristic that changes according to the nut position; A second step is to generate second vibration information based on a vibration signal acquired during a second period later than the first period and when the ball screw is operating, wherein the second vibration information represents a relationship between a nut position of the ball screw and a frequency-vibration level characteristic that changes according to the nut position; as well as In a third step, a state determination process of the ball screw is performed based on the first vibration information and the second vibration information.

12. The method for determining the state of a ball screw according to claim 11, wherein: In the first step, an averaging process is performed on a plurality of first vibration information acquired in the first period.

13. The method for determining the state of a ball screw according to claim 11, wherein: In the first step, first vibration information is generated by removing a periodic vibration component of the vibration signal acquired during the first period.

14. The method for determining the state of a ball screw according to claim 13, wherein: In the first step, an averaging process is performed on a plurality of first vibration information acquired in the first period.

15. The method for determining the state of a ball screw according to claim 14, wherein: In the second step, an averaging process is performed on a plurality of second vibration information acquired in the second period.

16. The method for determining the state of a ball screw according to claim 15, wherein: In the second step, second vibration information is generated by removing the periodic vibration component of the vibration signal acquired in the second period.

17. The method for determining the state of a ball screw according to any one of claims 11 to 16, wherein: In the third step, third vibration information obtained by multiplying the second vibration information by the first vibration information is calculated.

18. The method for determining the state of a ball screw according to claim 17, wherein: In the third step, the degree of wear of the ball screw is determined based on the statistical value of the third vibration information.

19. The method for determining the state of a ball screw according to any one of claims 11 to 16, wherein: In the third step, the consistency between the second vibration information and the first vibration information is calculated.

20. The method for determining the state of a ball screw according to claim 19, wherein: In the third step, the degree of wear of the ball screw is determined based on the degree of consistency.

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