Method for quickly constructing a cluster of monitoring indicators of a feed axis based on multi-axis servo current

Abstract

The present application belongs to the technical field of intelligent manufacturing, and particularly relates to a kind of feeding shaft monitoring index cluster fast construction method based on multi-axis linkage servo current, and its steps include: compiling X-axis, Y-axis, Z-axis three-axis linkage program, obtaining each axis linkage current;Synchronous current sequence processing, extract X-axis, Y-axis, Z-axis monitoring index cluster;First, the current sequence is subjected to STFT transformation, and a time-frequency spectrum is drawn;Positioning X-axis current signal characteristic frequency;Based on significant frequency, non-significant frequency, motor frequency and screw frequency, X-axis index cluster is extracted;Similarly, the monitoring index cluster of Y-axis and Z-axis is extracted.The present application can quickly and stably extract the health status information in the servo current of the feeding system for monitoring the feeding shaft system;Through multi-axis linkage decoupling, "machine tool linkage once, multi-axis index synchronous construction" is realized, and the test evaluation efficiency is high;The method can greatly reduce human intervention through program solidification, and is convenient for automatic implementation.

Description

Technical Field

[0001] The present invention belongs to the field of intelligent manufacturing technology, and in particular relates to a method for quickly constructing a feed axis monitoring indicator cluster based on multi-axis linkage servo current. Background Art

[0002] The feed axis system of a machine tool usually uses a "motor with ball screw" method to achieve servo control of the feed platform. The power motor is connected to the ball screw through a direct connection or a pulley. This mechanical transmission solution has a compact structure, low energy consumption, and a transmission efficiency of up to 90%. However, the cost is that the operating space is greatly limited, and it is difficult to implement the health status assessment of the feed axis system based on high-precision external sensors. Against the background of the increasingly intelligent level of mechanical equipment, this has undoubtedly become a shortcoming that seriously restricts the upgrading of mechanical equipment.

[0003] Feed axis systems generate numerous current signals during the "position-speed-current" servo control process. These signals are correlated to varying degrees with the mechanical state of the controlled object. The feed motor torque current, in particular, is linearly correlated with the torque load of the entire feed system and accurately reflects the system's lubrication, friction, and component wear conditions. Therefore, using motor torque current, rather than external sensor signals, is the most economical solution for quantitatively assessing feed axis health. However, motor torque current is extremely sensitive and often exhibits non-stationary characteristics. Furthermore, as a control variable of the CNC system, the frequency of subscribing to this variable from the system interface rarely exceeds 200 Hz, making information extraction challenging. Consequently, the application of this variable has remained limited to simple numerical comparisons. Furthermore, machine tools are complex, highly integrated pieces of machinery with numerous auxiliary platforms such as tool magazines and rotary tables, and may have more than 10 feed axes. Sequentially operating each axis independently to collect motor torque current significantly reduces the machine's operating time and reduces efficiency. Excessive human intervention makes effective organization difficult, limiting the automation of assessment and monitoring. Summary of the Invention

[0004] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current, which can efficiently extract multiple feed axis system detection indicators of machine tool equipment and realize efficient and reliable monitoring of the machine tool feed axis system status.

[0005] To achieve the above technical effects, the technical solutions of this application are as follows:

[0006] A method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current, the steps of which include:

[0007] Step (1). Prepare the three-axis linkage program of X-axis, Y-axis and Z-axis, and obtain the linkage current of each axis;

[0008] Step (2). Synchronizing the current sequence i X (n), i Y (n), i Z (n) processing, extracting X-axis, Y-axis, Z-axis monitoring index cluster;

[0009] Step (2.1). First, the current sequence i X (n) is subjected to STFT transformation, calculating the amplitude matrix I X (p,q), drawing the time-frequency spectrum I X (t,f);

[0010] Step (2.2). Based on the time-frequency spectrum I X (t,f), positioning the X-axis current signal characteristic frequency f(ξ);

[0011] Step (2.3). Based on f(ξ), screening significant frequencies non-significant frequencies motor frequencies and lead screw frequencies

[0012] Step (2.4). Based on significant frequencies non-significant frequencies motor frequencies and lead screw frequencies extracting X-axis index cluster P X ;

[0013] Step (2.5). Similarly, repeating steps 2.1 to 2.4, Y-axis and Z-axis monitoring index clusters P Y and P Z can be quickly extracted based on the current sequence i Y (n), i Z (n).

[0014] Further, step (1) is specifically: the X-axis, Y-axis, Z-axis three-axis motion stroke of the machine tool is represented as s X , s Y , s Z , the feed speed is v, the servo control current of the X-axis, Y-axis, Z-axis in the linkage process is obtained from the numerical control system, and the current sequence is represented as i X (n), i Y (n), i Z (n), n=1,2,…,N, wherein n is the sequence number, N is the sequence length, and the sequence sampling frequency is uniform f s ;

[0015] Further, step (2.1) is specifically:

[0016] (2.1) first, the current sequence iX (n) performing STFT transform to calculate amplitude matrix I X (p,q), drawing time-frequency spectrum I X (t,f) according to the following mapping relationship:

[0017]

[0018] wherein t(p) represents a discrete time sequence, p is a time sequence number, f(q) represents a discrete frequency sequence, q is a frequency sequence number, f s is a current sampling frequency, L is a window width parameter of STFT transform, parameters f s and L determine the frequency resolution of the spectrum, f s In the implementation of current data acquisition, f s is artificially selected (according to the sampling theorem, f

[0019] Further, L is calculated by the following formula:

[0020]

[0021] wherein Δf E is a desired frequency resolution, Δf E is smaller, the more detailed frequency information that can be identified by the spectrum, but at the same time, the time span will increase, and the interference frequency introduced by the non-stationary factor will significantly increase, therefore, Δf E is near 0.01f s , and L is calculated as a computer number 2 k , k∈N * , N * is a set of positive integers, facilitating efficient operation.

[0022] Further, the step (2.2) is specifically:

[0023] Step (2.2.1). Calculate order statistics to eliminate the interference of the main non-stationary factor;

[0024] Step (2.2.2). Define a characteristic frequency based on

[0025] Further, the step (2.2.1) is specifically: along the time axis of the time-frequency spectrum I X (t,f), statistics are performed on the amplitudes to calculate the α-quantile α is a stationary time length ratio (remove the significant non-stationary time length of the feed shaft system start-stop, commutation, etc.), which is obtained by empirical observation, and the value interval is [0.6, 0.9];

[0026] ​Further, step (2.2.2) is specifically: the characteristic frequency is represented as f(ξ), ξ = 1, 2, 3…, wherein ξ is the characteristic frequency number, and f(ξ) needs to satisfy the following conditions:

[0027]

[0028] Further, step (2.3) specifically includes:

[0029] Step (2.3.1). Calculate the theoretical motor rotation frequency of the X-axis and the theoretical screw rotation frequency

[0030]

[0031]

[0032] Wherein, λ represents the lead of the X-axis screw, and n represents the transmission ratio between the X-axis screw and the motor shaft;

[0033] Step (2.3.2). Set all f(ξ) satisfying the condition to form the characteristic frequency set F of the X-axis servo current X , and on the basis of F X , the following four subsets are screened to form: and

[0034] ① If , then is called a significant frequency;

[0035] ② If I α (f(ξ)) < median(I α (f(ξ))), f(ξ) ∈ F X , then is called a non-significant frequency;

[0036] ③ If or ω ∈ N * , f(ξ) ∈ F X , then is called a screw frequency;

[0037] ④ If or ω ∈ N * , f(ξ) ∈ F X , then is called a motor frequency.

[0038] Further, the step (2.4) is specifically: based on and extract the index cluster P X = [PX1 ,P X2 ,P X3 ,P X4 ] is as follows, where P X1 is called a salient feature, P X2 is called a non-significant feature, P X3 It is called the motor characteristic, P X4 It is called the screw feature;

[0039]

[0040]

[0041]

[0042]

[0043] The advantages of this application are:

[0044] The present invention can quickly and stably extract health status information from the servo current of the feed system for feed axis system monitoring; through multi-axis linkage decoupling, it can achieve "machine tool linkage once, multi-axis indicators are constructed synchronously", and the test and evaluation efficiency is high; this method can greatly reduce human intervention through program solidification, facilitating automated implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A method flow is provided for quickly constructing a feed axis monitoring indicator cluster based on multi-axis linkage servo current.

[0046] Figure 2 Schematic diagram of the mechanical transmission structure of the feed shaft system.

[0047] Figure 3 is the X-axis servo current and displacement signal.

[0048] Figure 4 is the Y-axis servo current and displacement signal.

[0049] Figure 5 It is the time spectrum of the servo current on the X-axis.

[0050] Figure 6 It is the time spectrum of the servo current on the Y-axis.

[0051] Figure 7 is the 0.75 quantile of the X-axis servo current spectrum Spectrum.

[0052] Figure 8 is the characteristic frequency F of the X-axis servo current X and its subsets and.

[0053] Figure 9 It is the X-axis monitoring indicator cluster sequence. DETAILED DESCRIPTION

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0055] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0056] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0057] In the description of this application, it should be noted that the terms "upper," "vertical," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of the application is typically placed when in use, or are the orientations or positional relationships commonly understood by those skilled in the art. These terms are intended only to facilitate the description of this application and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0058] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "installed," and "connected" should be understood broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0059] Example 1

[0060] like Figure 1 As shown, a method for quickly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current includes the following steps:

[0061] Step (1). Prepare the three-axis linkage program of X-axis, Y-axis and Z-axis, and obtain the linkage current of each axis;

[0062] Step (2). Synchronize the current sequence i X (n), i Y (n), i Z (n) Processing, extracting X-axis, Y-axis, and Z-axis monitoring indicator clusters;

[0063] Step (2.1). First, the current sequence i X (n) Perform STFT transformation and calculate the amplitude matrix I X (p,q), plotting the time spectrum I X (t,f);

[0064] Step (2.2). Based on time-frequency spectrum I X (t,f) locates the characteristic frequency f(ξ) of the X-axis current signal;

[0065] Step (2.3). Screen significant frequencies based on f(ξ) Non-significant frequency Motor frequency and screw frequency

[0066] Step (2.4). Based on significant frequency Non-significant frequency Motor frequency and screw frequency Extract X-axis indicator cluster P X ;

[0067] Step (2.5). Repeat steps 2.1 to 2.4 in the same way, and the current sequence i Y (n), i Z (n) Quickly extract the monitoring indicator cluster P of the Y-axis and Z-axis Y and P Z .

[0068] The present invention can quickly and stably extract health status information from the servo current of the feed system for feed axis system monitoring; through multi-axis linkage decoupling, it can achieve "machine tool linkage once, multi-axis indicators are constructed synchronously", and the test and evaluation efficiency is high; this method can greatly reduce human intervention through program solidification, facilitating automated implementation.

[0069] Example 2

[0070] like Figure 1 As shown, a method for quickly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current includes the following steps:

[0071] Step (1). Write X-axis, Y-axis, Z-axis three-axis linkage program, get each axis linkage current;

[0072] Step (2). Synchronize the current sequence i X (n), i Y (n) processing, extract X-axis, Y-axis, Z-axis monitoring index cluster; Z

[0073] Step (2.1). First, the current sequence i X (n) is subjected to STFT transform, the amplitude matrix I X (p,q) is calculated, and the time-frequency spectrum I X (t,f) is drawn;

[0074] Step (2.2). Based on the time-frequency spectrum I X (t,f), the X-axis current signal characteristic frequency f(ξ) is located;

[0075] Step (2.3). Based on f(ξ), the significant frequency non-significant frequency motor frequency and screw frequency

[0076] Step (2.4). Based on the significant frequency non-significant frequency motor frequency and screw frequency X-axis index cluster P X is extracted;

[0077] Step (2.5). Similarly, repeat steps 2.1 to 2.4, and based on the current sequence i Y (n), i Z (n), the monitoring index clusters P Y and P Z of Y-axis and Z-axis can be quickly extracted.

[0078] Further, step (1) is specifically: the X-axis, Y-axis, Z-axis three-axis movement stroke of the machine tool is represented as s X , s Y , s Z , the feed speed is v, the servo control current of X-axis, Y-axis, Z-axis in the linkage process is obtained from the numerical control system (Siemens system obtains through Trace Service service, variable is Torque-prod.curr.act.val.i(q)), and the current sequence is represented as i X (n), i Y (n), i Z ​(n), n=1,2,…,N, where n is the sequence number, N is the sequence length, and the sequence sampling frequency is unified as f s ;

[0079] Furthermore, step (2.1) is specifically as follows:

[0080] (2.1) First, the current sequence i X (n) Perform STFT transformation, calculate the amplitude matrix I X (p,q), draw the time spectrum I according to the following mapping relationship X (t,f):

[0081]

[0082] Among them, t(p) represents a discrete time series, p is the time series number, f(q) represents a discrete frequency series, q is the frequency series number, f s is the current sampling frequency, L is the window width parameter of STFT transformation, and parameter f s and L determine the frequency resolution of the spectrum, f s When implementing current data acquisition, it is manually selected (according to the sampling theorem, f s It needs to be greater than 2 times the research frequency, and in actual operation it is usually 5 times the rotation frequency of the feed motor). L can be calculated by the following formula.

[0083] Furthermore, L is calculated by the following formula:

[0084]

[0085] Where Δf E is the desired frequency resolution, Δf E The smaller the value, the more detailed the frequency information that can be identified by the spectrum, but at the same time it will cause the time span to increase and the interference frequency introduced by non-stationary factors will increase significantly. Therefore, Δf E Usually taken at 0.01f s Nearby, while trying to make L the computer number 2 k ,k∈N * , N * It is a set of positive integers, which facilitates efficient calculations.

[0086] Furthermore, the step (2.2) is specifically as follows:

[0087] Step (2.2.1). Calculate the order statistics to eliminate the interference of non-stationary factors of the subject;

[0088] Step (2.2.2). The characteristic frequency is defined based on

[0089] Further, step (2.2.1) is specifically: along the time-frequency spectrum I X Statistical analysis of the amplitude in the time axis direction (t,f) to calculate the alpha quantile Alpha is the proportion of stationary time length (remove significant non-stationary time length such as start-stop and commutation of the feed shaft system), obtained by empirical observation, the value range is [0.6, 0.9];

[0090] Further, step (2.2.2) is specifically: the characteristic frequency is represented as f(ξ), ξ = 1, 2, 3…, wherein ξ is the characteristic frequency number, in order to further reduce the influence of non-stationary interference frequency, f(ξ) must satisfy the following conditions:

[0091]

[0092] Further, step (2.3) specifically includes:

[0093] Step (2.3.1). Calculate the theoretical motor rotation frequency of X-axis And the theoretical screw rotation frequency

[0094]

[0095]

[0096] Wherein, λ represents the lead of X-axis screw, n represents the transmission ratio between X-axis screw and motor shaft;

[0097] Step (2.3.2). Set all f(ξ) that meet the conditions to form the characteristic frequency set F of X-axis servo current X On the basis of F X Filter to form the following 4 subsets: And

[0098] ① If Then It is called significant frequency;

[0099] ② If I α (f(ξ))<median(I α (f(ξ))), f(ξ)∈F X Then It is called non-significant frequency;

[0100] ③ If Or ω∈N * , f(ξ)∈F X Then It is called screw frequency;

[0101] ④ If Or ω∈N * ,f(ξ)∈F X , then is called the motor frequency.

[0102] Further, the step (2.4) is specifically: based on and extracting the index cluster P X =[P X1 ,P X2 ,P X3 ,P X4 ] as follows, wherein P X1 is called the significant feature, P X2 is called the insignificant feature, P X3 is called the motor feature, and P X4 is called the screw feature.

[0103]

[0104]

[0105]

[0106]

[0107] The application can quickly and stably extract the health state information in the servo current of the feeding system for monitoring the feeding shaft system; through multi-axis linkage decoupling, the "machine tool linkage once and multi-axis index synchronous construction" is realized, and the test and evaluation efficiency is high; the method can greatly reduce human intervention through program solidification, and is convenient for automatic implementation.

[0108] Example 3

[0109] An aviation structural part production machining center is in a horizontal structure, and the X and Y direction feeding shafts adopt the transmission structure as shown in Figure 2 The synchronous belt transmission ratios of the two shafts are: η X = 30 / 60 = 1 / 2, η Y = 30 / 75 = 2 / 5, the lead of the two shaft screw rods is: λ X = 30 mm, and λ Y = 30 mm. The control system of the equipment is SIEMENS 840D pl, and in the embodiment, only the XY two-axis linkage is used to illustrate the problem, and the XYZ three-axis linkage is the same.

[0110] 1. An NC program is prepared to control the X and Y two-axis linkage, the linkage feeding speed is set to v = 12000 mm / min, the X axis stroke s X = 3000 mm, and the Y axis stroke s Y= 2000 mm. The current signals during the X, Y axis movement are obtained by calling the Trace Service service, as shown in Figures 3-4 . It can be seen from the figure that the X, Y axis control platform makes uniform speed reciprocating motion between (X-1500, Y-1000) and (X 1500, Y 1000), and the length of the pause during the commutation is about 3.2 s. The inflection point of the current and the movement trajectory is consistent, and it is divided into obvious "positive and negative two sections", the internal of each section is relatively stable (lubrication uneven, mechanical wear, etc. may cause local instability), and there is obvious unstable impact during the start and stop of the motor and the commutation. The sampling interval of the system is 27 ms, that is, the sampling frequency f s = 1 / 0.027 = 37 Hz.

[0111] 2. Process the X axis and Y axis current sequences i X and i Y respectively, and extract the X, Y axis monitoring index cluster.

[0112] 2.1 Perform STFT transformation on the current signals i X , i Y with a window width L = 256, and the time-frequency spectrum is shown in Figures 5-6 . In the figure, the frequency bright band that does not change with time, that is, the characteristic frequency, can be clearly identified, including 5.50 Hz, 11.14 Hz, 14.76 Hz in Figure 5 , and 3.76 Hz, 9.26 Hz in Figure 6 , etc.

[0113] 2.2 Quickly locate the characteristic frequency of the current signal based on the time-frequency spectrum (X axis as an example):

[0114] 2.2.1 Take α = 0.75, and statistically process the amplitude along the time axis of the time-frequency spectrum, calculate the 0.75 quantile , and draw the statistical spectrum as shown in Figure 7 . It can be seen that the frequency bright band in Figure 7 is highly consistent with Figure 5 , and can well reduce the interference of noise frequency and instability factors.

[0115] 2.2.2 According to the rules described in step 2.2, the characteristic frequency set F is constructed based on . The characteristic frequency set F contains 9 frequency elements: {4.63, 5.50, 7.38, 9.26, 9.84, 11.14, 14.76, 16.20, 17.36}.

[0116] 2.3 Build the X axis index cluster based on F:

[0117] 2.3.1 Calculate the X axis theoretical motor rotation frequency and theoretical screw rotation frequency according to the geometric parameters

[0118] 2.3.2F's base on the screening of significant frequency set, non-significant frequency set, screw frequency set, motor frequency set: and As Figure 8 shown, part of the frequency has multiple attributes, such as 5.50Hz is both a significant characteristic frequency and a motor characteristic frequency, a screw characteristic frequency.

[0119] 2.4 Based on and extract index cluster P X = [0.24, 0.02, 0.66, 0.43].

[0120] 2.5 Similarly, the index cluster P Y = [1.27, 2.54, 2.6, 4.72] can be obtained.

[0121] From January 1, 2020 to December 28, 2021, the machining center X-axis was continuously monitored by the monitoring index cluster described in the method. 40 monitoring current data were obtained, the monitoring index cluster was extracted, and the trend curve was drawn as shown in Figure 9 . As can be seen from the figure, the change rule of the four components of the index cluster is divided into two parts with August 24, 2020 as the boundary. According to the records, it was found that on that day, a strategy adjustment was made, and the feed speed and running track in the NC program were optimized. Before August 24, 2020, the four components of the index cluster had no obvious trend. After August 24, 2020, the four components of the index cluster showed a cumulative upward trend, among which the significant characteristic was the most sensitive, the non-significant characteristic had the best stability. The index cluster reached a peak on February 24, 2021, and subsequent maintenance found that the bearing on one side of the X-axis screw was severely worn. After repair, the components of the index cluster quickly decreased and returned to a certain range of smooth fluctuations.

[0122] In summary, the feed shaft monitoring index cluster construction method based on multi-axis linkage servo current described in the method can realize "machine tool linkage once, multi-axis index synchronous construction", greatly improving the evaluation and monitoring efficiency of the machine tool feed shaft system state. In addition, the index cluster has strong correlation with the equipment state, has obvious trend and strong indication.

Claims

1. A method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current, characterized by: The steps include: Step (1). Obtain the linkage current of the X-axis, Y-axis, and Z-axis; Step (2). Synchronize the current sequence 、 、 Processing, extracting X-axis, Y-axis, and Z-axis monitoring indicator clusters; Step (2.1). First, the current sequence Perform STFT transformation and calculate the amplitude matrix , plot the time-frequency spectrum ; Step (2.2). Based on time-frequency spectrum Locate the characteristic frequency of the X-axis current signal ; Step (2.3). Based on Screening for significant frequencies , non-significant frequency , motor frequency and screw frequency ; Step (2.4). Based on significant frequency , non-significant frequency , motor frequency and screw frequency , extract the X-axis indicator cluster ; Step (2.5). Repeat steps (2.1) to (2.4) in the same way, and the current sequence can be 、 Quickly extract monitoring indicator clusters of the Y-axis and Z-axis and .

2. The method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current according to claim 1 is characterized in that: Step (1) is as follows: the motion range of the three axes of the machine tool, X-axis, Y-axis and Z-axis, is expressed as 、 、 , the feed speed is v , obtain the servo control current of X-axis, Y-axis and Z-axis in the linkage process from the CNC system, and the current sequence is expressed as ,in n is the serial number, N is the sequence length, and the sequence sampling frequency is unified as .

3. The method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current according to claim 1, characterized in that: Step (2.1) is as follows: First, the current sequence Perform STFT transformation and calculate the amplitude matrix , draw the time spectrum according to the following mapping relationship : ； in, t ( p ) represents a discrete time series, p is the time series number, f ( q ) represents a discrete frequency sequence, q is the frequency sequence number, is the current sampling frequency, L is the window width parameter of STFT transformation, parameter and L Determines the frequency resolution of the spectrum. When implementing current data acquisition, it is manually selected. It must be greater than twice the study frequency.

4. The method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current according to claim 3 is characterized in that: L is calculated by the following formula: in, is the desired frequency resolution, The smaller it is, the more detailed the frequency information that can be identified in the spectrum.

5. The method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current according to claim 1, characterized in that: The step (2.2) is specifically as follows: Step (2.2.1). Calculate the order statistics and eliminate the interference of non-stationary factors of the subject; Step (2.2.2). The characteristic frequencies are defined based on .

6. The method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current according to claim 5, characterized in that: Step (2.2.1) is as follows: along the time spectrum Count the amplitude in the time axis direction and calculate the α quantile , α is the proportion of stable duration, and its value range is [0.6, 0.9].

7. The method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current according to claim 5, characterized in that: Step (2.2.2) is as follows: the characteristic frequency is expressed as ,in is the characteristic frequency number, The following conditions must be met: 。 8. The method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current according to claim 1, characterized in that: Step (2.3) specifically includes: Step (2.3.1). Calculate the theoretical motor speed on the X axis and theoretical screw speed : in, represents the X-axis screw lead, and n represents the transmission ratio between the X-axis screw and the motor shaft; Step (2.3.2). Assume that all The characteristic frequency set that constitutes the X-axis servo current ,exist The following 4 subsets are formed based on the screening: 、 、 and : ① If ,but , called significant frequency; ②If ,but , called non-significant frequency; ③If ,but , called the screw frequency; ④ If ,but , called the motor frequency.

9. The method for rapidly constructing a feed axis monitoring index cluster based on multi-axis linkage servo current according to claim 1, characterized in that: The step (2.4) is specifically as follows: based on 、 、 and , extract indicator clusters ,in called salient features, called non-salient features, is called the motor characteristic, It is called the screw feature; 。

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