Abnormality diagnosing device for feed shaft mechanism

Abstract

The present application provides an abnormality diagnosis device of a feed shaft mechanism, in which rotation of a servo motor is transmitted to a ball screw via a coupling to move a moving body in an axial direction, capable of quickly detecting generation of an abnormality and accurately determining a position of the abnormality. The abnormality diagnosis device determines that the feed shaft mechanism has an abnormality when a change amount of at least one of measured resonance frequencies with respect to a reference value exceeds an abnormality presence / absence determination threshold value. In addition, when it is thus determined that the feed shaft mechanism has an abnormality, a difference between a change amount of a resonance frequency measured at a stroke position on a coupling connection side with respect to a reference value and a change amount of a resonance frequency measured at a stroke position on a counter-coupling connection side with respect to a reference value is found, and in a case where the difference exceeds an abnormality position determination threshold value, it is diagnosed that the coupling is abnormal, and in other cases, it is diagnosed that the ball screw is abnormal.

Description

Technical Field

[0001] This invention relates to an anomaly diagnosis device for diagnosing anomalies and abnormal locations in the feed axis mechanism mounted on a machine tool. Background Technology

[0002] Machine tools equipped with a feed axis mechanism consisting of a servo motor, coupling, support bearing, and ball screw. In machine tools with such a feed axis mechanism, unexpected malfunctions can lead to unplanned losses; therefore, it is necessary to detect warning signs before malfunctions occur. Furthermore, when warning signs of malfunctions are detected, it is also necessary to identify the abnormal location that is causing the malfunction in order to eliminate it.

[0003] In the feed axis mechanisms of machine tools, many utilize a method where the rotational motion of a motor is transmitted to a ball screw, causing it to rotate and thus moving a moving part along a guide device. Furthermore, as a method for diagnosing whether the operation of such a feed axis mechanism is normal, the method of using resonant frequencies has been proposed.

[0004] For example, Patent Document 1 discloses an anomaly diagnosis method that detects the resonant frequency by controlling a control device for a servo motor used to drive a machine tool, calculates the stiffness based on the resonant frequency, and notifies the user that an inspection should be performed based on the calculation result. Additionally, Patent Document 2 discloses a fault diagnosis system that detects faults associated with a decrease in preload of the ball screw by combining the axial resonant frequency of a predetermined mechanical structure, including the ball screw unit and the motor, at a given time point when the motor rotates to drive the lead screw shaft, with the position of the nut component on the lead screw shaft corresponding to that resonant frequency.

[0005] Existing technical documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-34224

[0007] Patent Document 2: Japanese Patent Application Publication No. 2019-105317 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In a feed axis mechanism composed of components such as a servo motor, coupling, support bearing, and ball screw, the resonant frequency comprehensively reflects the overall composition of the feed axis system. Therefore, in addition to the preload reduction caused by ball screw wear, changes in rigidity caused by deformation of the coupling leaf spring can also be causes of feed axis malfunctions affecting the resonant frequency. Consequently, in conventional fault diagnosis methods such as those described in Patent Documents 1 and 2, it is difficult to determine the location of the fault (i.e., the cause of the fault) in cases of resonant frequency changes.

[0010] The purpose of this invention is to provide an anomaly diagnosis device that eliminates the problems in conventional feed axis mechanism fault diagnosis methods such as those in Patent Documents 1 and 2. In a feed axis mechanism that transmits the rotation of a servo motor to a ball screw via a coupling to move the moving body axially, the device can quickly detect the occurrence of an anomaly and accurately determine the location of the anomaly (i.e., the detailed cause of the anomaly).

[0011] Methods for solving problems

[0012] To achieve the above objectives, the invention described in technical solution 1 is a diagnostic device for diagnosing abnormalities and abnormal locations in a feed shaft mechanism that transmits the rotation of a motor to a ball screw connected via a coupling for rotational drive. The device is characterized by measuring resonant frequencies at multiple stroke positions within the stroke range of the feed shaft mechanism, and determining the abnormal location based on the relationship between these stroke positions and the changes in each measured resonant frequency relative to a reference value.

[0013] The invention described in technical solution 2 is characterized in that, in the invention described in technical solution 1, if the change of at least one of the resonant frequencies measured at two stroke positions relative to a reference value exceeds a preset threshold for determining whether an abnormality exists (if the change of the resonant frequency relative to the reference value is greater than the threshold, or if the change of the resonant frequency relative to the reference value is greater than the threshold), it is determined that there is an abnormality in the feed shaft mechanism. When an abnormality is determined to exist in the feed shaft mechanism, the difference between the change of the resonant frequency relative to the reference value measured at the stroke position on the coupling connection side and the change of the resonant frequency relative to the reference value measured at the stroke position on the anti-coupling connection side is calculated. If the difference exceeds a preset threshold for determining the abnormal location, it is diagnosed as a coupling abnormality; otherwise, it is diagnosed as a ball screw abnormality.

[0014] The invention described in technical solution 3 is characterized in that, in the invention described in technical solution 1, if the change of at least one of the resonant frequencies measured at multiple stroke positions relative to a reference value exceeds a pre-set threshold for determining whether an abnormality exists (the change of the resonant frequency relative to the reference value is greater than the threshold, or the change of the resonant frequency relative to the reference value is above the threshold), it is determined that there is an abnormality in the feed axis mechanism. The change of the resonant frequency at each stroke position measured is approximated by a mathematical formula, and the abnormal location is determined by the approximation formula.

[0015] The invention described in technical solution 4 is characterized in that, in the invention described in technical solution 3, a first-order linear approximation is used as the approximation. Based on the coefficients in the first-order linear approximation and the comparison result of the threshold value determined by the pre-set abnormal part, as well as the setting position of the coupling relative to the stroke position, the abnormality of the lead screw shaft, the coupling, or the nut part or rolling element of the ball screw is diagnosed.

[0016] That is, the invention described in technical solution 4 includes the following: when the coupling is in the positive side of the stroke position, if the coefficient exceeds the threshold for determining the abnormal part (the coefficient is larger than the threshold or the coefficient is above the threshold), it is diagnosed as a coupling abnormality; if the coefficient is lower than the threshold for determining the abnormal part (the coefficient is smaller than the threshold or the coefficient is below the threshold), it is diagnosed as a ball screw abnormality caused by the nut or rolling element of the ball screw; when the coupling is in the negative side of the stroke position, if the coefficient is lower than the threshold for determining the abnormal part (the coefficient is smaller than the threshold or the coefficient is below the threshold), it is diagnosed as a coupling abnormality; if the coefficient exceeds the threshold for determining the abnormal part (the coefficient is larger than the threshold or the coefficient is above the threshold), it is diagnosed as a ball screw abnormality caused by the nut or rolling element of the ball screw.

[0017] The invention described in technical solution 5 is characterized in that, in the invention described in technical solution 3, a second-order approximation is used as the approximation. When the coefficient in the second-order approximation is negative, the abnormality is diagnosed as being caused by local wear of the lead screw shaft. When the stroke position of the peak (highest point) of the second-order approximation is on the coupling side relative to the center of the stroke, the abnormality is diagnosed as being in the nut part or rolling element of the ball screw. When the stroke position of the peak (highest point) of the second-order approximation is on the opposite side of the coupling relative to the center of the stroke, the abnormality is diagnosed as being in the coupling.

[0018] Invention Effects

[0019] According to the abnormality diagnosis device of the feed axis mechanism described in technical solution 1 (hereinafter referred to as the abnormality diagnosis device), in the feed axis mechanism that transmits the rotation of the servo motor to the ball screw through the coupling to make the moving body move axially, the occurrence of abnormality can be detected quickly and the location of the cause of the abnormality can be determined with high precision.

[0020] According to the abnormality diagnosis device described in technical solution 2, it is possible to determine very accurately whether the abnormal part is the coupling or the ball screw.

[0021] According to the abnormality diagnosis device described in technical solutions 3 to 5, it is possible to determine with extreme accuracy whether the abnormal part is the coupling, the nut part or rolling element of the ball screw, or the screw shaft. Attached Figure Description

[0022] Figure 1 This is an explanatory diagram showing a structural example of a feed shaft mechanism using an abnormality diagnostic device.

[0023] Figure 2 This is an explanatory diagram showing the change in the resonant frequency of a faulty part of the feed axis mechanism (example).

[0024] Figure 3 This is a flowchart illustrating the abnormal diagnosis process of the abnormality diagnosis device.

[0025] Figure 4 This is an explanatory diagram illustrating a case where a linear approximation is made of the change in the resonant frequency of a fault location based on the feed axis mechanism (example).

[0026] Figure 5 This is an explanatory diagram illustrating an example of how the resonant frequency change of a fault location in a feed axis mechanism is approximated using a quadratic equation.

[0027] Label Explanation

[0028] 1: NC control device;

[0029] 2: Feed axis mechanism;

[0030] 10: Moving objects;

[0031] 11: Servo motor;

[0032] 12: Position detector;

[0033] 13: Coupling;

[0034] 14a, 14b: Support bearings;

[0035] 15: Ball screw;

[0036] 17: Nut section;

[0037] D, D', D”: Abnormal diagnostic device. Detailed Implementation

[0038] Hereinafter, an embodiment of the abnormality diagnosis device of the present invention will be described with reference to the accompanying drawings.

[0039] [First Implementation Method]

[0040] <Structure of feed axis mechanism and fault diagnosis device>

[0041] Figure 1 An example of a feed axis mechanism equipped with the fault diagnosis device of the present invention is shown. The feed axis mechanism 2 consists of the following parts: a feed axis body, which is composed of a ball screw 15, support bearings 14a and 14b, a servo motor 11, a coupling 13, a guide device 16, a moving body 10, and a nut part 17; and an NC (numerical control) device 1 (position control device) for controlling the movement of the feed axis body.

[0042] That is, in the feed axis mechanism 2, support bearings 14a and 14b are fixedly mounted on a base (not shown), and these support bearings 14a and 14b are used to keep the ball screw 15 rotatable. The ball screw 15 is connected to the shaft component of the servo motor 11, which is a drive device, via a coupling 13. In addition, a position detector 12 is provided on the servo motor 11 for detecting the position of the moving body 10 in the axial direction of the ball screw 15, and the servo motor 11 is connected to the NC device 1.

[0043] The NC device 1 is equipped with a resonant frequency measuring unit 21 for measuring the resonant frequency and a diagnostic unit 22 for diagnosing operational abnormalities. Furthermore, the NC device 1 includes a storage unit composed of RAM, ROM, etc., a timer, etc., and is connected to a display unit such as a monitor and an input unit such as a numeric keypad via an interface. Figure 1 (The description of each component of the NC device 1 is omitted here). Furthermore, the NC device 1, in cooperation with the servo motor 11 and the position detector 12, constitutes an anomaly diagnosis device D for diagnosing anomalies in the feed axis mechanism 2.

[0044] Furthermore, between the front and rear support bearings 14a and 14b of the ball screw 15, the nut portion 17 is movably screwed in, and a movable body 10 is fixedly mounted on the upper part of the nut portion 17. Also, above the ball screw 15, a guide device (rail, etc.) 16 is provided along the length of the ball screw 15, and the lower surface of the movable body 10 is slidably engaged with the guide device 16.

[0045] In the aforementioned feed axis mechanism 2, the servo motor 11 is activated by a command generated by the NC device 1, causing the ball screw 15 to rotate by a predetermined amount. This allows the moving body 10, fixedly mounted on the nut portion 17, to translate axially along the ball screw 15, guided by the guide device 16. Furthermore, the position detector 12 of the servo motor 11 detects the position of the moving body 10 based on the rotation amount of the ball screw 15 and feeds back the detection signal to the NC device 1, thereby controlling the translational operation.

[0046] <Methods for diagnosing anomalies in the feed axis mechanism using an anomaly diagnostic device>

[0047] Next, the abnormality diagnosis method of the abnormality diagnosis device D for the feed axis mechanism 2 will be explained. When diagnosing abnormalities in the feed axis mechanism 2 using the abnormality diagnosis device D, the resonant frequency measurement unit 21 measures the resonant frequency at multiple positions within the stroke range of the feed axis mechanism 2 (i.e., from the position where the moving body 10 is closest to the support bearing 14a to the position where the moving body 10 is furthest from the support bearing 14a). Specifically, when a control signal of a sine wave scanning within a specified frequency range is input to the servo motor 11 via an instruction from the NC device 1, the frequency response is calculated using the signal detected by the position detector 12 and the input waveform. Furthermore, the frequency at which the calculated frequency response gain is maximized is detected as the resonant frequency. When the resonant frequency is detected in this way, the abnormality diagnosis device D determines the abnormal location (fault location) using various methods based on the relationship between the measured stroke position and the amount of decrease in the resonant frequency relative to a reference value (described later) pre-stored in the storage unit of the NC device 1.

[0048] In such Figure 1 In the feed axis mechanism 2 shown, the resonant frequency of the feed axis system varies due to the influence of all elements constituting the feed axis system, including the connection between the moving body 10 and the nut portion 17 of the ball screw 15, the screw shaft of the ball screw 15, the support bearings 14a and 14b supporting both ends of the ball screw 15, and the coupling 13. Furthermore, in... Figure 1 In the feed axis mechanism 2 shown, due to the wear and damage of the ball screw 15, the rigidity of the nut part 17 of the ball screw 15 is reduced, and due to the deformation of the leaf spring of the coupling 13, the rigidity of the coupling 13 changes, which will cause abnormalities (malfunctions).

[0049] Figure 2 It shows that in having, as Figure 1 When the feed axis mechanism 2 of the shown configuration malfunctions, the resonant frequency changes at the stroke position (an example). The screw shaft of the ball screw 15 is divided into two sides (positive and negative sides) of the stroke according to the position of the nut portion 17. At the position of the nut portion 17 (i.e., the stroke position), the resonant frequency changes. Therefore, depending on the position of the nut portion 17, the degree of influence on the change of the resonant frequency of each element constituting the two sides of the stroke will vary.

[0050] Furthermore, when coupling 13 is located on the positive side of the stroke and there is an abnormality in coupling 13, the change on the positive side becomes extremely large. Figure 2 (Case A in the text). Additionally, in cases where the ball screw 15 malfunctions, primarily due to wear on the nut portion 17 (or rolling elements), the reduction in the resonant frequency relative to normal conditions becomes ball screw malfunction 1 (…). Figure 2The change is as shown in case B in the example. On the other hand, in the case of local wear on the ball screw shaft, the amount of reduction in the resonant frequency relative to the normal condition becomes ball screw abnormality 2 ( Figure 2 The abnormality diagnosis device D detects the abnormality in the feed axis mechanism 2 and determines the location of the abnormality based on the change in the amount of reduction of the resonant frequency at each stroke position as described above.

[0051] The following is based on Figure 3 The flowchart illustrates the specific process of abnormal diagnosis by the abnormality diagnosis device D.

[0052] When performing anomaly diagnosis using the anomaly diagnosis device D, firstly, in step 1 (hereinafter referred to only by "S"), the resonant frequency is measured at two points at both ends of the stroke by the resonant frequency measurement unit 21 (S1). Then, in the following S2, the amount of reduction relative to a preset (stored) reference value is calculated for each measured resonant frequency (S2). Furthermore, the resonant frequency measured immediately after the feed axis mechanism 2 is assembled is stored in the storage unit of the NC device 1 as a reference value (normal value) for the resonant frequency.

[0053] After calculating the decrease of each resonant frequency relative to the reference value in S2, in the following S3, it is determined whether any one of the decreases in the resonant frequencies on both sides of the stroke exceeds a pre-set threshold for determining whether an anomaly exists (pre-stored in the storage unit of NC device 1). Then, if the determination in S3 is "yes" (i.e., if any one of the decreases in the resonant frequencies exceeds the threshold for determining whether an anomaly exists), it is considered that there is an anomaly in the feed axis system, and S4 for determining the location of the anomaly is executed.

[0054] In S4, the decrease in resonant frequency on the coupling connection side (the side closer to coupling 13) is compared with the decrease in resonant frequency on the anti-coupling connection side (the side farther from coupling 13), and it is determined whether the decrease on the coupling connection side is above the threshold for determining an abnormal part compared to the decrease on the anti-coupling connection side. Furthermore, if the determination in S4 is "yes" (i.e., if the decrease on the coupling connection side is above the threshold for determining an abnormal part compared to the decrease on the anti-coupling connection side), in S5, it is considered that an abnormality has occurred due to the influence of coupling 13, and this indication is displayed on the display unit of the NC device 1.

[0055] On the other hand, in S3, if the judgment is "no" (i.e., if the decrease in each resonant frequency is less than the threshold for determining whether an anomaly exists), the feed axis mechanism 2 is determined to be normal, and this information is displayed on the display unit of the NC device 1. Furthermore, if the judgment is "no" in S4 (i.e., if the decrease on the reverse coupling side is greater than the decrease on the coupling side, or the difference between the decrease on the coupling side and the decrease on the reverse coupling side is less than the threshold for determining an abnormal location), in S6, it is considered that an anomaly has occurred due to the influence of the ball screw 15, and this information is displayed on the display unit of the NC device 1.

[0056] <Effects of the Abnormal Diagnostic Device>

[0057] As described above, the abnormality diagnosis device D measures the resonant frequency at two points within the stroke range of the feed axis mechanism 2. Based on the relationship between these stroke positions and the changes in each measured resonant frequency relative to the reference value, the abnormal location is determined. Therefore, the occurrence of abnormalities can be detected quickly, and the location of the cause of the abnormality can be determined.

[0058] Furthermore, as described above, if the change in either of the two measured resonant frequencies relative to a reference value exceeds a threshold for determining the presence or absence of an anomaly, the anomaly diagnosis device D determines that the feed shaft mechanism 2 is abnormal. In this case, it calculates the difference between the change in the resonant frequency relative to the reference value measured at the travel position on the coupling connection side and the change in the resonant frequency relative to the reference value measured at the travel position on the reverse coupling connection side. If this difference exceeds a threshold for determining the location of the anomaly, the coupling 13 is diagnosed as abnormal; otherwise, the ball screw 15 is diagnosed as abnormal. Therefore, according to the anomaly diagnosis device D, it is possible to very accurately determine whether the abnormal location is the coupling 13 or the ball screw 15.

[0059] [Second Implementation]

[0060] The anomaly diagnosis device D' of the second embodiment has the same structure as the anomaly diagnosis device D of the first embodiment, but the method (number of measurements) for measuring the resonant frequency and the method for processing the measured resonant frequency are different from those of the anomaly diagnosis device D of the first embodiment. That is, the anomaly diagnosis device D' of the second embodiment measures the resonant frequency at multiple positions (equally spaced positions) within its travel range using the resonant frequency measurement unit 21. Then, it processes the measured resonant frequency at each travel position relative to a reference value, such as... Figure 4 As shown, a first-order linear approximation (y = ax + b) is obtained by using methods such as the least squares method.

[0061] Furthermore, the coefficient 'a' in this first-order linear approximation falls within the range of a pre-set threshold for determining anomalies (stored in the memory cell of NC device 1) (i.e., when the absolute value of coefficient 'a' is below the threshold for determining anomalies, for example, ...). Figure 4 In the case of C', the diagnosis is an abnormality caused by local wear of the screw shaft of ball screw 15.

[0062] Furthermore, in the feed axis mechanism 2, the coupling 13 is located on the negative side of the stroke position. Therefore, when the coefficient a exceeds the threshold for determining the abnormal part (for example, when the coefficient a is larger than the threshold for determining the abnormal part), Figure 4 In the case of A', the diagnosis is that coupling 13 is abnormal. In other cases (where the coefficient a is negative and its absolute value is greater than the threshold used to determine the abnormality, for example...),... Figure 4 In case B', the diagnosis is that the main cause of the ball screw 15 is an abnormality in the nut part 17 (or the rolling element).

[0063] Furthermore, when the abnormality diagnosis device D' is mounted on the feed shaft mechanism 2 on the positive side of the coupling 13 at the stroke position, if the coefficient a exceeds the threshold for determining the abnormal part, it can be diagnosed that the main cause of the ball screw 15 is an abnormality of the nut part 17 (or rolling element), and otherwise, it can be diagnosed that the coupling 13 is abnormal.

[0064] As described above, the anomaly diagnosis device D' of the second embodiment approximates the change in resonant frequency (measured value) at each stroke position relative to a reference value using a mathematical formula. It uses a first-order linear approximation and determines the location of the anomaly based on the comparison result between the coefficients in this first-order linear approximation and a pre-set threshold for determining anomalies, as well as the setting position of the coupling 13 relative to the stroke position. Therefore, according to the anomaly diagnosis device D', it is possible to determine with extremely high accuracy whether the anomaly is in the coupling 13, the nut 17 of the ball screw 15, or the screw shaft.

[0065] [Third Implementation Method]

[0066] The anomaly diagnosis device D” of the third embodiment has the same structure as the anomaly diagnosis device D of the first embodiment, but the method (number of measurements) for measuring the resonant frequency and the method for processing the measured resonant frequency of the resonant frequency measurement unit 21 are different from those of the anomaly diagnosis device D of the first embodiment. That is, similar to the anomaly diagnosis device D’ of the second embodiment, the anomaly diagnosis device D” of the third embodiment measures the resonant frequency at multiple positions (equally spaced positions) within the stroke using the resonant frequency measurement unit 21. Then, as Figure 5As shown, the change in resonant frequency at each travel position relative to the reference value is approximated twice using methods such as the least squares method, resulting in the second approximation formula (y = px). 2 +qx+r).

[0067] Furthermore, in the case where the coefficient p in this second approximation is negative (for example, Figure 5 In the case of "C" in the formula, the diagnosis is that the abnormality is caused by local wear of the screw shaft of ball screw 15. On the other hand, in the case where the coefficient p in the second approximation is positive (e.g., Figure 5 In the case of "A" or "B" in the above, the diagnosis is that coupling 13 is abnormal.

[0068] Furthermore, if the coefficient p in the quadratic approximation is negative, and the stroke position of the quadratic equation's peak (highest point) is on the side where the coupling 13 is set relative to the center of the stroke, it is diagnosed that the main cause of the ball screw 15 is an abnormality of the nut portion 17 (or rolling element). If the stroke position of the quadratic equation's peak (highest point) is on the opposite side of the coupling (opposite to the setting position of the coupling 13) relative to the center of the stroke, it is diagnosed that the coupling 13 is abnormal.

[0069] As described above, the anomaly diagnosis device D” of the third embodiment approximates the change in resonant frequency (measured value) at each stroke position relative to a reference value using a mathematical formula. A second-order approximation is used. When the coefficient in this second-order approximation is negative, the anomaly is diagnosed as being caused by localized wear of the lead screw shaft. When the stroke position at the vertex of the second-order approximation is on the coupling side relative to the center of the stroke, the anomaly is diagnosed as being in the nut portion 17 (or rolling element) of the ball screw 15. When the stroke position at the vertex of the second-order approximation is on the opposite side of the coupling 13 relative to the center of the stroke, the anomaly is diagnosed as being in the coupling 13. Therefore, according to the anomaly diagnosis device D” of the third embodiment, it is possible to determine with extreme accuracy whether the anomaly is in the coupling 13, the nut portion 17 (or rolling element) of the ball screw 15, or the lead screw shaft.

[0070] <Example of Change to the Abnormal Diagnostic Device>

[0071] The anomaly diagnosis device of the present invention is not limited to the form described in the above embodiments, and the structure of the NC device (resonant frequency measurement unit, diagnosis unit), servo motor, position detector, etc., can be appropriately modified as needed without departing from the spirit of the present invention. Furthermore, the structure of the feed axis mechanism equipped with the anomaly diagnosis device of the present invention is not limited to the form described in the above embodiments, and the structure of the ball screw, support bearing, servo motor, coupling, guide device, moving body, nut, etc., can be appropriately modified as needed.

[0072] For example, the anomaly diagnosis device of the present invention is not limited to determining the resonant frequency by detecting the frequency response gain that is maximized when a sine wave control signal scanning within a specified frequency range is used to detect the signal detected by the position detector and the input waveform at the input, as described in the above embodiment. Other methods can also be used to determine the resonant frequency. Furthermore, the anomaly diagnosis device of the present invention is not limited to setting the resonant frequency measured immediately after assembly as the reference value (normal value) as described in the above embodiment. It can also be modified to set the average value of the resonant frequencies measured in multiple feed axis mechanisms of the same type as the reference value. Moreover, the anomaly diagnosis device of the present invention is not limited to approximating the change in the resonant frequency (measured value) at each stroke position relative to the reference value using the least squares method, or a first-order or second-order mathematical expression, as described in the above embodiment. Other mathematical methods can also be used to approximate the change in the resonant frequency at each stroke position relative to the reference value using first-order or second-order mathematical expressions.

Claims

1. A diagnostic device for an abnormality in a feed axis mechanism, used to diagnose the occurrence and location of abnormalities in the feed axis mechanism, wherein the feed axis mechanism is driven to rotate by transmitting the rotation of a motor to a ball screw connected via a coupling, thereby causing a movable body fixedly mounted on the nut portion of the screwed ball screw to move axially along the ball screw, characterized in that, The resonant frequencies are measured at two nut positions within the stroke range of the feed axis mechanism. If the change in at least one of the resonant frequencies measured at these nut positions relative to a reference value exceeds a pre-set threshold for determining the presence or absence of an anomaly, the feed axis mechanism is determined to be abnormal. When an abnormality is determined in the feed shaft mechanism, the difference between the change in resonant frequency relative to the reference value measured at the nut position on the coupling connection side and the change in resonant frequency relative to the reference value measured at the nut position on the reverse coupling connection side is calculated. If the difference exceeds a preset threshold for determining the abnormal location, the abnormality is diagnosed as a coupling abnormality; otherwise, the abnormality is diagnosed as a ball screw abnormality.

2. A diagnostic device for an abnormality in a feed axis mechanism, used to diagnose the occurrence and location of abnormalities in the feed axis mechanism, wherein the feed axis mechanism is driven to rotate by transmitting the rotation of a motor to a ball screw connected via a coupling, thereby causing a movable body fixedly mounted on the nut portion of the screwed ball screw to move axially along the ball screw, characterized in that, The resonant frequency is measured at multiple nut positions within the stroke range of the feed axis mechanism. If the change of at least one of the resonant frequencies measured at the multiple nut positions relative to a reference value exceeds a preset threshold for determining whether an anomaly exists, the feed axis mechanism is determined to have an anomaly. The change in resonant frequency at each nut location relative to a reference value is approximated using mathematical formulas. These approximations are then used to determine abnormal locations. A linear approximation of degree one is used as the approximation. Based on the coefficients in the first-order linear approximation and the comparison results of the pre-set abnormal part with the threshold value, as well as the set position of the coupling relative to the nut, the diagnosis is made as to whether the abnormality is in the ball screw shaft, the coupling, or the nut or rolling element of the ball screw.

3. A diagnostic device for an abnormality in a feed axis mechanism, used to diagnose the occurrence and location of abnormalities in the feed axis mechanism, wherein the feed axis mechanism is driven to rotate by transmitting the rotation of a motor to a ball screw connected via a coupling, thereby causing a movable body fixedly mounted on the nut portion of the screwed ball screw to move axially along the ball screw, characterized in that... The resonant frequency is measured at multiple nut positions within the stroke range of the feed axis mechanism. If the change of at least one of the resonant frequencies measured at the multiple nut positions relative to a reference value exceeds a preset threshold for determining whether an anomaly exists, the feed axis mechanism is determined to have an anomaly. The change in resonant frequency at each nut location relative to a reference value is approximated using mathematical formulas. These approximations are then used to determine abnormal locations. Using a quadratic approximation as the approximation, if the coefficient in this quadratic approximation is negative, the diagnosis is that the abnormality is caused by localized wear of the ball screw shaft. If the nut portion, which forms the vertex of the approximate second degree, is located on the coupling side relative to the center of the stroke, the diagnosis is an abnormality in the nut portion or rolling element of the ball screw. If the position of the nut portion, which is the vertex of the approximate second degree, is on the opposite side of the coupling relative to the center of the stroke, it is diagnosed as a coupling malfunction.

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