TW201337233A - Method of monitoring the ball-screw preload variation in a ball-screw feed drive system - Google Patents

Abstract

The method of monitoring the ball-screw preload variation in a ball-screw feed drive system includes a feed drive system with the ball-screw module, proload-adjustable module, and signal processing module. The ball-screw feed drive system is modeled as a lumped system and the spectrum of the ball-screw and working platform can be found. A MEMS-based vibration sensing system is installed onto the feed drive system to acquire signals. Through the analysis of modeling and experimental results, the ball-screw preload variation can be on-line monitored.

Description

Method for monitoring pre-pressure change of a ball screw in a feed system

The invention relates to a feed system pre-pressure change monitoring method, in particular to a method for monitoring a pre-pressure change of a ball screw in a feed system.

In recent years, due to the increasing demand for quality and production rate of the manufacturing industry, the development of high-speed precision feed drive systems has also become a highly regarded technology. Among them, the ball screw system in the feed drive system is A technology that converts the rotary motion of a motor into a linear motion. It plays a very important role in the field of transmission. Therefore, the application of ball screw has spread throughout the high-tech industry to daily life, such as automation industry, semiconductor industry, logistics. Transportation even in the medical industry or other facilities that require precise positioning.

The movement mechanism of the existing ball screw is rolling in a point contact manner between the ball and the screw and the nut groove. Compared with the surface contact between the nut and the screw of the conventional sliding screw, the ball screw has a low friction transmission mode. With higher rigidity and lower axial backlash, it can also provide a smooth motion characteristic and long-term precision. The existing ball screw can change the ball by setting different preload modes during operation. The rigidity of the screw, in which the pre-stressing system is applied, can greatly reduce the axial clearance between the screw and the nut, so that the ball screw can achieve high-resolution positioning capability. On the other hand, avoiding excessive pre-pressure can also reduce the screw movement. The heat generated thereby maintains the service life of the screw. Existing ball screws can be preloaded in different ways to meet user requirements, such as a single nut ball screw that uses a larger ball to provide a proper amount of preload, or a double nut. The ball screw inserts a tip between the nuts to form a preloading effect. When the ball screw is actually operated, the ball wear and damage will reduce the screw at the beginning. Preload factory set value, so that the wear of the ball screw bearing is more than high, will affect the relative production quality during processing, have to be honest improvement.

In order to improve the actual operation of the existing ball screw, the ball wear and damage will reduce the preload value set by the screw at the time of initial shipment, so that the ball screw wears higher than the bearing, which will affect the lack of production quality during processing. Insufficient, the object of the present invention is to provide a method for monitoring the pre-pressure change of a ball screw in a feed system, which is to measure the vibration signal of the ball screw feed system and analyze the parameters of the mathematical model through a feed system. The data analysis of the captured signal not only allows the user to effectively monitor the change of the preload value of the screw, but also indirectly reflects the degree of wear of the ball by the rolling and sliding of the ball through the reduction of the preload, so that the ball screw The feed system provides a precise machining, feeding and positioning function.

Based on the above objects, the technical means utilized by the present invention is to provide a method for monitoring the pre-pressure change of a ball screw in a feed system, which comprises the following steps: instrument setting: preparing a single-axis driven ball screw into The system is provided with a ball screw module, an adjustable preloading module, a vibration sensing module and a signal processing module, the ball screw module is provided with a ball screw and a working stage, the working load A nut seat is coupled to the bottom surface of the table, and the nut seat is convexly disposed on the outer side surface. The adjustable pre-pressing module is disposed on the ball screw and is provided with a main screw a cap, a driven nut, a disc spring and a positioning nut, the main nut is disposed in the nut seat and combined with the ball screw, the driven nut is sleeved on the ball screw The disc spring is sleeved on the ball screw and interposed between the main nut and the driven nut, the positioning nut is screwed with the positioning nut and abuts against the disc spring, The vibration sensing module and the two are respectively disposed on the main screw And a vibration sensor on the driven nut, the signal processing module is connected to the vibration sensing module, thereby recording and analyzing the measured acceleration value; preload setting: selecting an appropriate ball size, When the ball screw die assembly is completed, the pre-pressure value is close to zero. After adjusting the pre-pressure value, the pre-pressure value is set by rotating the positioning nut to compress the disk spring; dynamic modeling: the ball screw The feed system is modeled as a centralized system, and the preload value is set to less than 10% of the rated dynamic load, so that the rigid performance of the main nut is expressed as a function of the preload value and the rated dynamic load of the ball screw; The above function calculates the vibration spectrum of the ball screw and the working stage, wherein the axial rigidity of the nut of the ball screw is used as a variable to check the effect of the change of the preload value of the ball screw, thereby finding the corresponding dynamic change. The trend of the simulation shows that the decrease of the preload value of the screw causes a decrease in the peak frequency. The preload change of the ball screw can be performed by monitoring the rigidity of the nut; The vibration sensing module performs vibration measurement on the main nut and the driven nut, and applies different preloading to the ball screw module by rotating the positioning nut to deform the disc spring. By setting a sampling frequency, the vibration signals of the main nut, the driven nut and the working stage under different preloading conditions can be obtained. For the short-time Fourier transform of the vibration signal, the peak frequency changes with time and has periodicity. The characteristics; and the result analysis: the simulation and measurement results are analyzed, wherein the spectrum change trend measured by the vibration sensing module and the peak frequency variation trend of the simulation result are consistent, and the monitoring is performed. The vibration signal of the ball screw module determines the preload change of the ball screw module.

Further, in the operation step of the instrument setting, the ball screw module is provided with a base and a servo motor, and the base is provided with two parallel sliding rails, and the servo motor is fixed at one end of the base, The ball screw system is connected to the servo motor and rotatably disposed above the base and between the two slide rails, and the ball screw is provided with two spaced support bearing seats on the base.

Further, in the operation step of the instrument setting, the adjustable pre-pressing module is provided on the ball screw with a support member coupled with the driven nut and abutting the working stage, thereby reducing the cause The weight of the working platform itself generates a slight deformation or bending effect, and the disc spring is sleeved on the ball screw and interposed between the main nut and the supporting member, and each vibration sensor is composed of one a printed circuit board and a capacitive accelerometer, the signal processing module is connected to the vibration sensing module and has a switching interface and a computer, wherein the switching interface is connected to each vibration sensor The computer is connected to the transfer interface, and a program for data display and analysis is provided in the computer for recording and analyzing the measured acceleration values.

Preferably, in the operation step of the instrument setting, each capacitive acceleration gauge is an acceleration gauge manufactured by Analog Device Co., Ltd. model ADXL321, which can simultaneously measure the acceleration of the two axes, and the maximum measurement range is 18G (G is The gravitational constant), and the size of the accelerometer is 4 mm × 4 mm × 1.45 mm.

Preferably, in the operation step of the instrument setting, the vibration sensor is encapsulated in an aluminum tube through a heat-resistant epoxy resin, and then placed in the hole processed by the nut seat, and The external lock is fixed by a metal piece, so that the acceleration gauge of the vibration sensor is disposed close to the surface of the main nut, and the vibration sensor mounted on the driven nut is directly adhered to the surface. The way to fix it.

Preferably, in the dynamic modeling operation step, the dynamic modeling of the ball screw feed system is expressed by the following mathematical equation:

Where M _t is the mass of the work stage, M _b is the mass of the ball screw, J _m is the servo motor inertia, J _b is the ball screw inertia, K _e is the equivalent axial rigidity of the ball screw and the support bearing, and K _n is the ball screw The nut is axially rigid, K _g is the torsional rigidity of the screw, B _t is the viscous damping coefficient of the axial direction of the working stage, B _b is the axial viscous damping coefficient of the ball screw support bearing seat, and Q _m is the servo motor Torque viscous damping coefficient, Q _b : Torque viscous damping coefficient of ball screw support bearing housing, d _r is ball screw shaft diameter, β is the axial displacement of the ball screw shaft caused by rotation, α is tangential to the ball screw shaft The equivalent friction coefficient of the direction of rotation, T is the motor torque, X _b is the axial displacement of the ball screw, X _t is the displacement of the working stage, θ _m is the motor rotation angle and θ _b is the rotation angle of the ball screw.

Preferably, in the operation step of the simulation result, wherein the first mode and the second mode are axial vibrations generated by the ball screw in the feeding direction, and the third mode is generated by the ball screw in the rotating motion. Torque vibration.

Preferably, in the operation step of the measurement result, the ball screw feed system has a working displacement of 400 mm, a feed rate of 5 m/min, a linear acceleration/deceleration time of 0.5 seconds, and a thousand Hertz is used as the sampling frequency, and the frequency range of the analysis is 0~500 Hz. The patterns of three different peaks can be classified into three different frequency block ranges: 100~300, 300~400 and more than 400 Hz.

Preferably, in the operation step of the result analysis, the two-parameter parameter resonance frequency and its corresponding power level are analyzed, wherein as the pre-pressure increases, the resonance frequency values exhibit frequency in the simulated and measured conditions. The similar trend of increase, while the power level of the resonant frequency and the magnitude of the preload value also show the same trend, and the relationship between the preload and the peak frequency and its frequency can be obtained by normalizing the peak frequency and the corresponding power level. Corresponding power level relationship, the pre-pressure change of the ball screw module can be judged by the power level corresponding to the peak frequency and the frequency thereof, and the ball screw module can be judged by monitoring the vibration signal of the ball screw module. Preload changes.

According to the above technical means, the method for monitoring the pre-pressure change of the ball screw in the feeding system mainly performs the actual measurement and simulation operation on the ball screw module through the instrument setting and dynamic modeling. The simulation result and the measurement result analysis can determine the pre-pressure change of the ball screw module through the relationship between the peak frequency and the power corresponding to the frequency. Therefore, when the ball screw is used for a period of time, the The invention monitors the method of preloading changes of the ball screw in the feeding system to evaluate the health state of the ball screw after using for a certain period of time, so as to avoid the ball screw being affected by factors such as abrasion, lubrication and mechanical condition, thereby reducing the preload value and affecting The accuracy of positioning and processing and shortening the service life, etc., constitute a convenient and practical method for monitoring the pre-pressure change of the ball screw in the feed system.

In order to understand the technical features and practical effects of the present invention in detail, and in accordance with the contents of the specification, the following is further illustrated in the preferred embodiment of the present invention (as shown in FIGS. 1 to 4).

The invention provides a method for monitoring a pre-pressure change of a ball screw in a feed system, and the operation flow thereof comprises:

A. Instrument setting: preparing a single-axis driven ball screw feeding system, the ball screw feeding system is provided with a ball screw module 10, an adjustable pre-pressing module 20, a vibration sensing module 30 and a The signal processing module 40, wherein the ball screw module 10 is provided with a base 11, a servo motor 12, a ball screw 13 and a working stage 14. The base 11 is provided with two slide rails 111 arranged in parallel. The servo motor 12 is fixed to one end of the base 11. The ball screw 13 is connected to the servo motor 12 and rotatably disposed above the base 11 between the two slide rails 111. Preferably, the ball motor 13 is disposed between the two slide rails 111. The ball screw 13 is provided with two spaced apart support bearing seats 131 on the base 11, and the working platform 14 is fixed on the bottom surface with a nut seat 15 coupled with the ball screw 13, and the nut seat 15 is The outer side surface is convexly provided with a high-precision positioning screw sleeve 151; the adjustable pre-pressing module 20 is disposed on the ball screw 13 and is provided with a main nut 21, a driven nut 22, a support frame 23, a disc spring 24 and a positioning nut 25, wherein the main nut 21 is disposed on the nut And in combination with the ball screw 13, the driven nut 22 is sleeved on the ball screw 13, wherein the ball screw 13 may have a slight deformation or bending effect due to the weight of the work stage 14 itself. Therefore, the adjustable preloading module 20 is provided with a support member 23 coupled with the driven nut 22 and abutting the working platform 14 on the ball screw 13 , thereby reducing the working stage 14 . A slight deformation or bending effect is generated by the weight of the disc spring 24, and the disc spring 24 is sleeved on the ball screw 13 and interposed between the main nut 21 and the support frame 23, and the positioning nut 25 is coupled with the positioning. The nut 151 is screwed and abuts against the disc spring 24, wherein the disc spring 24 is deformed by adjusting the rotation angle of the positioning nut 25, thereby the main nut 21 and the driven screw The distance of the cap 22 is increased, and at the same time, the ball gap in the main nut 21 is reduced, and a pre-pressure is applied to the ball screw 13; the vibration sensing module 30 is coupled to the adjustable pre-press module 21 Combined with two vibration sensors 31, wherein each vibration sensor 31 is printed by one The plate 32 and a capacitive accelerometer 33 are formed. Preferably, the capacitive accelerometer 33 is a comb structure made by an electrostatic force driven micro-process. When the comb structure is subjected to an acceleration effect, the comb structure is changed. The size of the capacitor, in turn, changes the output voltage to measure the acceleration signal. Further, each of the capacitive accelerometers 33 is an acceleration gauge manufactured by Analog Devices, Inc., model ADXL321, which can simultaneously measure the acceleration of the two axes, and the maximum amount. The measurement range is 18G (where G is the gravity constant), and the size of the acceleration gauge 33 is 4 mm (mm) × 4 mm (mm) × 1.45 mm (mm), and the two vibration sensors 31 are respectively Preferably, the vibration sensor 31 mounted on the driven nut 22 is fixed by directly adhering to the surface, and the main screw is fixed on the main nut 21 and the driven nut 22 Since the cap 21 is disposed in the nut holder 15, the vibration sensor 31 is embedded in the nut holder 15 to be engaged with the main nut 21, and further transmitted through a heat-resistant epoxy. The epoxy encapsulates the vibration sensor 31 all the way In an aluminum tube of 15 mm (mm) and height of 10 mm (mm), it is placed in a hole machined by the nut seat 15, and a metal piece is fixed on the outside to fix the vibration. The acceleration gauge 33 of the detector 31 is disposed at a surface that is relatively close to the main nut 21; and the signal processing module 40 is connected to the vibration sensing module 30 and is provided with a switching interface 41 and a computer 42. The switching interface 41 is connected to each of the vibration sensors 31, and the computer 42 is connected to the switching interface 41. The computer 42 is provided with a program 421 for data display and analysis. Record and analyze the measured acceleration values;

B. Pre-pressure setting: select the appropriate ball size so that the pre-pressure value of the ball screw 13 is close to zero when the die assembly is completed. Then, if the pre-pressure value needs to be adjusted, only the positioning nut 25 needs to be rotated to compress the disk shape. The spring 24 can obtain the preset pressure value to be set;

C. Dynamic Modeling: In order to analyze the dynamic characteristics of the ball screw module 10 under different preloads, the entire main nut 21 and the snail are provided through the manner in which the adjustable preloading module 20 is disposed on the ball screw module 10. The mechanism in which the cap 15, the driven nut 22, the working stage 14, the support frame 23, the disk spring 24, and the like are coupled to the ball screw module 10 is regarded as a rigid body, and the aforementioned component can be regarded as a rigid body. The vibration is neglected. Please refer to FIG. 5 to model the ball screw feeding system as a lumped system. The so-called centralized system refers to the ball screw feeding system shown in FIG. The relevant parameters in the whole are only regarded as a function of time. The rigidity of the entire ball screw feeding system is composed of the ball screw 13 itself, the bearing rigidity of the support member 23, and the rigidity between the work stage 14 and the screw 13, wherein the main The rigidity of the nut 21 is regarded as a variable, and the rigidity of the ball screw 13 can be determined by the diameter and length of the ball screw 13 itself. Further, when the preload value is less than 10% of the rated dynamic load, the main nut 21 is Just performance is expressed as preload And a function of the rated dynamic load of the ball screw 13; wherein the driven nut 22 has a mass, but the mass of the driven plate is smaller than that of the working stage 14 and the ball screw 13, and the related link is small. The quality of the fixture, since the work stage 14 is locked to the adjustable preload module 20, and the associated fixture is also locked to the driven nut 22, so that the combination of these components can be considered a rigid body , wherein the dynamic modeling of the ball screw feed system can be expressed by the following mathematical equation:

Where M _t is the mass of the working stage 14 , M _b is the mass of the ball screw 13 , J _m is the inertia of the servo motor 12 , J _b is the inertia of the ball screw 13 , and K _e is the equivalent axial rigidity of the ball screw 13 and the supporting bearing. K _n is the axial rigidity of the nut of the ball screw 13 , K _g is the torsional rigidity of the screw 13 , B _t is the viscous damping coefficient of the axial direction of the working stage 14 , and B _b is the axial direction of the bearing block 131 of the ball screw 13 Viscous damping coefficient, Q _m is the torque viscous damping coefficient of the servo motor 12, Q _b : the torque viscous damping coefficient of the ball screw support bearing seat, d _r is the diameter of the ball screw shaft 13 , and β is the ball screw shaft caused by the rotation The axial displacement of 13 is α, which is the equivalent friction coefficient of the direction of rotation of the ball screw shaft 13, T is the torque of the motor 12, X _b is the axial displacement of the ball screw 13, X _t is the displacement of the working stage 14, and θ _m is The rotation angle of the motor 12 and θ _b are the rotation angles of the ball screw 13;

D. Simulation result: The vibration spectrum of the ball screw 13 and the work stage 14 as shown in FIG. 6(a) is calculated by the above mathematical equation, wherein the first mode and the second mode are the ball screw 13 in the feed. The axial vibration generated by the direction, and the third mode is the torsional vibration caused by the rotational movement of the ball screw 13, wherein when the effect of the preload value change of the ball screw 13 is to be checked, the nut shaft of the ball screw 13 is used. The stiffness (K _n ) is used as a variable to find the corresponding dynamic change. Please refer to Figure 6(b)-(d) to apply a preload value of 0.5%~10%. During dynamic load, the first modal frequency of the vibration signal of the screw 13 ranges from 32 to 148 Hz, the second modal range is 312 to 360 Hz, and the third modal range is 735 to 750 Hz. Hz), it can be seen that the first mode has a larger frequency range of motion than the other two modes, wherein the resonance frequency in the second mode range is determined by the rigidity of the nuts 21, 22, and is simulated by The trend shows that the decrease in the preload value of the screw 13 causes a drop in the peak frequency, and therefore, the preload of the ball screw 13 Variable can be monitored via rigid nut 21, 22;

E. Measurement result: vibration measurement is performed on the main nut 21 and the driven nut 22 through the vibration sensing module 30, wherein the working displacement of the ball screw feeding system is 400 mm (mm), The feed speed is 5 meters/minute (m/min), the linear addition (deceleration) time is 0.5 seconds (s), and the ball screw 24 is deformed by rotating the positioning nut 25 to give the ball screw Different preloading of the module 10 (0, 18, 36 and 54 kg weight (kgf), set a sampling frequency (1 kHz), as shown in Figure 7 (a), (b), (c) The vibration signals of the main nut 21, the driven nut 22 and the working stage 14 (where the working stage 14 is provided with a sensor at a central position) under different preload conditions are short for the vibration signal. A short time Fourier transform (STFT) can be obtained as shown in Figures 8(a), (b), and (c), where the frequency range of the analysis is 0 to 500 Hertz (Hz), and three different peaks. The pattern can be categorized into three different frequency block ranges: 100~300, 300~400 and greater than 400 Hz. The figure shows that the peak frequency changes with time and has periodic characteristics. The results because the work stage 14 by the reciprocating motion caused by, in particular 300 to 400 Hertz (Hz) frequency range we can observe the energy intensity of the peak frequency variation greater phenomenon; and

F. Analysis of results: The results of the simulation and measurement are analyzed, wherein the spectrum change trend measured by the vibration sensing module 30 and the peak frequency change trend of the second mode of the simulation result are consistent. And further analyzing with two index parameter resonance frequencies and their corresponding power levels, as shown in Fig. 9(a), with the increase of the preload, the resonance frequency value under the condition of simulation and measurement Both show a similar trend of increasing frequency, and the power level and preload value of the resonant frequency also show the same trend. In addition, as shown in Fig. 9(b), the peak frequency is normalized and the corresponding power is obtained. The horizontal relationship can obtain the relationship between the pre-compression change and the power level corresponding to the peak frequency and its frequency, and the pre-pressure change of the ball screw module 10 can be judged by the power level corresponding to the peak frequency and the frequency thereof. The pre-pressure change of the ball screw module 10 is judged by monitoring the vibration signal of the ball screw module 10.

According to the above technical means, the method for monitoring the pre-pressure change of the ball screw in the feeding system mainly performs the actual measurement and simulation operation on the ball screw module 10 through the instrument setting and the dynamic modeling manner, and Through the analysis of the simulation result and the measurement result, the pre-pressure change of the ball screw module 10 can be judged by the magnitude relationship of the power corresponding to the peak frequency and the frequency thereof. Therefore, when the ball screw 13 is used for a period of time, The method for monitoring the pre-compression of the ball screw in the feed system by the present invention can be used to evaluate the health status of the ball screw 13 after a certain period of time, so as to avoid the pre-pressure value of the ball screw 13 due to factors such as wear, lubrication and mechanical conditions. The reduction affects the accuracy of positioning and processing and shortens the service life, and thus constitutes a convenient and practical method for monitoring the pre-pressure change of the ball screw in the feed system.

The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any one of ordinary skill in the art can use the present invention without departing from the scope of the present invention. Equivalent embodiments of the invention may be made without departing from the technical scope of the present invention.

10. . . Ball screw module

11. . . Base

111. . . Slide rail

12. . . Servo motor

13. . . Ball screw

131. . . Support bearing

14. . . Work stage

15. . . Nut seat

151. . . Positioning screw

20. . . Adjustable preloading module

twenty one. . . Main nut

twenty two. . . Driven nut

twenty three. . . Support frame

twenty four. . . Disc spring

25. . . Positioning nut

30. . . Vibration sensing module

31. . . Vibration sensor

32. . . A printed circuit board

33. . . Capacitive accelerometer

40. . . Signal processing module

41. . . Transfer interface

42. . . computer

421. . . Data display and analysis program

1 is a block diagram showing the operation of the method for monitoring the pre-pressure change of a ball screw in a feed system according to the present invention.

2 is a block diagram of a single-shaft driven ball screw feed system of the present invention.

Figure 3 is a top plan view of a single shaft driven ball screw feed system of the present invention.

Figure 4 is a partially enlarged cross-sectional side elevational view of the uniaxially driven ball screw feed system of the present invention.

Figure 5 is a schematic diagram of mathematical dynamic modeling of the ball screw feed system of the present invention.

Fig. 6(a) is a view showing the vibration spectrum of the ball screw and the working stage of the ball screw feeding system of the present invention.

6(b) to (d) are vibrational spectrum diagrams of the ball screw feeding system of the present invention for different preloading simulations of the ball screw and the working stage.

7(a) to (c) are acceleration signal diagrams of the main nut, the driven nut and the working stage of the ball screw feeding system of different preloadings according to the present invention.

8(a) to (c) are time-frequency analysis diagrams of the main nut, the driven nut, and the working stage of the present invention for performing short-time Fourier transform of FIGS. 7(a) to (c).

Fig. 9(a) is a graph showing the relationship between the peak frequency variation and the power corresponding to the frequency during the different preloading of the present invention.

Fig. 9(b) is a diagram showing the relationship between the peak frequency change and the power corresponding to the frequency of the different preloading voltages according to the present invention.

Claims (9)

A method for monitoring a pre-pressure change of a ball screw in a feed system, comprising the following steps: instrument setting: preparing a single-axis driven ball screw feeding system, which is provided with a ball screw module and an adjustable type a pre-pressing module, a vibration sensing module and a signal processing module, the ball screw module is provided with a ball screw and a working stage, the working stage is fixed on the bottom surface and combined with the ball screw a nut seat having a positioning nut protruding from the outer side surface, the adjustable pre-pressing module being disposed on the ball screw and provided with a main nut, a driven nut, a disc spring and a Positioning a nut, the main nut is disposed in the nut holder and combined with the ball screw, the driven nut is sleeved on the ball screw, and the disc spring is sleeved on the ball screw and interposed Between the main nut and the driven nut, the positioning nut is screwed with the positioning nut and abuts against the disc spring, and the vibration sensing module and the two are respectively disposed on the main a vibration sensor on the nut and the driven nut, the signal processing module and The vibration sensing module is connected to record and analyze the measured acceleration value; preload setting: select an appropriate ball size, so that the pre-pressure value of the ball screw die is close to zero when the ball screw die is assembled, and then adjust the pre-adjustment In the case of pressure value, the preload value is set by rotating the positioning nut to compress the disc spring; dynamic modeling: modeling the ball screw feed system into a centralized system, and setting the preload value to less than the rated dynamic 10% of the load, the rigidity of the main nut is expressed as a function of the preload value and the rated dynamic load of the ball screw; simulation results: the vibration spectrum of the ball screw and the work stage is calculated through the above function, wherein the screw of the ball screw The axial rigidity of the cap is used as a variable to check the effect of the preload value of the ball screw, so as to find the corresponding dynamic change. The trend of the simulation shows that the decrease of the preload value of the screw causes the peak frequency to drop. The ball screw The preload change can be performed by monitoring the rigidity of the nut; the measurement result: the main nut and the driven nut are vibrated through the vibration sensing module Measuring, and by rotating the positioning nut to deform the disc spring, giving the ball screw module different preloading, and setting a sampling frequency, the main nut, the driven nut and the working stage are obtained. The vibration signal under different pre-compression conditions, for the short-time Fourier transform of the vibration signal, shows that the peak frequency changes with time and has periodic characteristics; and the result analysis: the simulation and measurement results are analyzed, wherein The trend of the spectrum change measured by the vibration sensing module and the peak frequency variation trend of the simulation result are consistent, and the pre-pressure change of the ball screw module is determined by monitoring the vibration signal of the ball screw module. The method for monitoring a pre-pressure change of a ball screw in a feed system according to claim 1, wherein in the operating step of the instrument setting, the ball screw module is provided with a base and a servo motor, and the base is provided with two a slide rail disposed in parallel, the servo motor is fixed to one end of the base, the ball screw is connected to the servo motor and rotatably disposed above the base and between the two slide rails, and the ball screw is The base is provided with two spaced support bearing seats. The method for monitoring a pre-pressure change of a ball screw in a feed system according to claim 1 or 2, wherein in the operating step of the instrument setting, the adjustable pre-press module is provided with the slave on the ball screw a support member combined with the nut and abutting against the working stage, thereby reducing a slight deformation or bending effect caused by the weight of the working stage itself, and the disc spring is sleeved on the ball screw and Between the main nut and the support member, each of the vibration sensors is composed of a printed circuit board and a capacitive accelerometer. The signal processing module is connected to the vibration sensing module and is provided with a a switching interface and a computer, wherein the switching interface is connected to each of the vibration sensors, and the computer is connected to the switching interface, and a program for data display and analysis is provided in the computer, thereby The measured acceleration values are recorded and analyzed. The method for monitoring the pre-pressure change of the ball screw in the feed system according to claim 3, wherein in the operation step of the instrument setting, each of the capacitive acceleration gauges is an acceleration gauge manufactured by Analog Device Co., Ltd. model ADXL321, which can At the same time, the acceleration of the two axes is measured, and the maximum measurement range is 18G, G is the gravity constant, and the size of the acceleration gauge is 4 mm × 4 mm × 1.45 mm. The method for monitoring a pre-pressure change of a ball screw in a feed system according to claim 4, wherein in the operating step of the instrument setting, the vibration sensor is packaged in an aluminum tube through a heat-resistant epoxy resin. Then, it is placed in the hole of the nut seat processing, and a metal piece is fixed on the external lock, so that the acceleration gauge of the vibration sensor is disposed close to the surface of the main nut, and is installed on The vibration sensor on the driven nut is fixed by directly adhering to the surface. A method of monitoring a pre-pressure change of a ball screw in a feed system as described in claim 5, wherein in the dynamic modeling operation step, the dynamic modeling of the ball screw feed system is expressed by the following mathematical equation: Where M _t is the mass of the work stage, M _b is the mass of the ball screw, J _m is the servo motor inertia, J _b is the ball screw inertia, K _e is the equivalent axial rigidity of the ball screw and the support bearing, and K _n is the ball The screw nut of the screw is axially rigid, K _g is the torsional rigidity of the screw, B _t is the viscous damping coefficient of the axial direction of the working stage, B _b is the axial viscous damping coefficient of the ball screw support bearing seat, and Q _m is the servo Torque viscous damping coefficient of the motor, Q _b : Torque viscous damping coefficient of the ball screw support bearing housing, d _r is the diameter of the ball screw shaft, β is the axial displacement of the ball screw shaft caused by the rotation, α is tangential to the ball screw The equivalent friction coefficient of the direction of rotation of the shaft, T is the motor torque, X _b is the axial displacement of the ball screw, X _t is the displacement of the work stage, θ _m is the rotation angle of the motor, and θ _b is the rotation angle of the ball screw. A method for monitoring a pre-pressure change of a ball screw in a feed system according to claim 6, wherein in the operation step of the simulation result, wherein the first mode and the second mode are generated by the ball screw in the feed direction The axial vibration, and the third mode is the torsional vibration generated by the ball screw in the rotary motion. The method for monitoring a pre-pressure change of a ball screw in a feed system according to claim 7, wherein in the operation step of the measurement result, the ball screw feed system has a working displacement of 400 mm and a feed rate of 5 Metric/minute, linear acceleration/deceleration time is 0.5 second, and 1 kHz is used as sampling frequency, wherein the frequency range of analysis is 0~500 Hz, and the patterns of three different peaks can be classified into three different frequency blocks. Range: 100~300, 300~400 and greater than 400 Hz. The method for monitoring a pre-pressure change of a ball screw in a feed system according to claim 8, wherein in the operation step of the result analysis, the two-parameter parameter resonance frequency and its corresponding power level are analyzed, wherein with the pre-compression The increase, in the simulation and measurement conditions, the resonance frequency values all show a similar trend of increasing frequency, while the power level of the resonant frequency and the magnitude of the preloading value also show the same trend, and the peak frequency is normalized and phase Corresponding power level relationship can obtain the relationship between the preload variation and the power level corresponding to the peak frequency and its frequency. The preload variation of the ball screw module can be judged by the power level corresponding to the peak frequency and its frequency, that is, The preload change of the ball screw module can be judged by monitoring the vibration signal of the ball screw module.