Axial positioning control method and system for numerical control lathe

Abstract

The invention relates to the technical field of numerical control machine tool control, in particular to a numerical control machine tool axial positioning control method and system. The method comprises the following steps: driving a servo motor to execute reverse clearance compensation motion; the synchronous sampling period obtains a position signal and a load current signal; performing composite judgment based on the position signal and the load current signal: judging whether the variable quantity of the position signal along the instruction direction reaches a preset position threshold value or not, and judging whether the increment of the load current signal relative to the reference current value reaches a preset current threshold value or not; when all items are compositely judged to be met at the same time, it is judged that the mechanical clearance is eliminated, reverse clearance compensation motion is terminated, and a double-closed-loop axial positioning control mode is switched; and when any one item is not satisfied through composite judgment, keeping the reverse clearance compensation motion. The problems that when the numerical control lathe rotates reversely in the axial movement direction for clearance compensation, compensation is not accurate, a workbench continuously wriggles near the target position, and the machining precision is affected are solved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of numerical control machine tool control, in particular to a numerical control lathe axial positioning control method and system. BACKGROUND

[0002] In the field of modern precision manufacturing, numerical control lathes bear the task of machining high-precision parts, and the performance of their axial positioning control system directly determines the quality of the final product. Usually, to meet the stringent precision requirements, such systems will adopt an advanced control strategy, namely a double closed-loop axial positioning control method based on the data fusion of grating scales and encoders. This method uses the high-precision absolute position information provided by grating scales and the high-speed relative displacement information provided by encoders, integrates the advantages of both through a data fusion algorithm, and combines an inner-outer double closed-loop control structure, in order to achieve precise and stable control of the workbench position, especially to strike a balance between high-speed motion and precise positioning.

[0003] However, in actual industrial production environments, when a numerical control lathe continuously performs a precision part machining task for a long time, a large amount of fine metal chips will be continuously generated during the machining process. These chips, carried by the cutting fluid, may not be completely removed and gradually accumulate in the tiny gap between the grating scale body and the reading head, and mix with the oily components and trace impurities in the cutting fluid to form a thin, translucent mixture. This mixture will cause slight scattering and attenuation of the optical signal path inside the grating scale reading head, making the original position signal output by the grating scale no longer stable, but intermittent and small amplitude fluctuations. Such fluctuations are not continuous, but intermittent, and their amplitude usually hovers around the edge of the system's normal noise threshold, so their overall function has not been completely lost and it is difficult for conventional signal anomaly detection mechanisms to immediately identify them as faults.

[0004] In the axial positioning control of numerical control lathes, to ensure high precision, a compensation program for the reverse clearance of the ball screw transmission chain is usually preset. When the motion direction is reversed, the servo motor performs compensation motion at a small speed until the workbench overcomes the mechanical clearance and begins to move actually. This judgment process highly depends on the position signal of the grating scale. However, during the critical stage of fine positioning, the grating scale may produce intermittent fluctuations of small amplitude due to surface contamination or other interference. Such fluctuations are similar to actual small displacement signals and are easily misjudged by the control system as the clearance being eliminated.

[0005] After misjudgment, the compensation procedure can be terminated prematurely, resulting in residual clearance not being eliminated; or delayed due to signal uncertainty, continuing compensation after the clearance has been eliminated, causing excessive displacement. Whether premature or delayed, both will introduce inaccurate compensation, forming a new small position deviation. This deviation makes the double closed-loop control system unstable near the target position, and the position loop cannot obtain a reliable error signal due to the uncertainty of the grating feedback itself. The result is that the workbench continuously overshoots and swings near the target point, i.e., the "creeping" phenomenon.

[0006] This "creeping" causes the workbench to be unable to maintain within the expected static precision range, but to continuously oscillate within a small interval. For precision machining tasks that require high surface quality and dimensional consistency, this unstable state will significantly reduce the machining precision, and even cause the parts to be scrapped or not meet the quality standards.

[0007] In view of the above problems, the prior art needs to be improved. SUMMARY

[0008] The present application discloses a numerical control lathe axial positioning control method and system, aiming to solve the problem of misjudgment caused by intermittent fluctuations of the grating signal when the numerical control lathe reverses in the axial motion direction for gap compensation, which in turn leads to inaccurate compensation, continuous "creeping" of the workbench near the target position, and affects the machining precision.

[0009] The technical solution of the present application is as follows: In a first aspect, the present application discloses a numerical control lathe axial positioning control method, comprising: When reversing in the axial motion direction, driving the servo motor to perform reverse gap compensation motion at a preset small speed; During the reverse gap compensation motion, acquiring the position signal of the workbench and the load current signal of the servo motor at a synchronous sampling period; Based on the position signal and the load current signal, composite judgment is performed: within a preset duration window, it is judged whether the change amount of the position signal in the command direction reaches a preset position threshold, and whether the increase amount of the load current signal relative to the reference current value before the reverse gap compensation motion reaches a preset current threshold; When all items of the composite judgment are satisfied at the same time, it is determined that the mechanical clearance has been eliminated, the reverse gap compensation motion is terminated, and the normal double closed-loop axial positioning control mode is switched to; When any one of the composite judgment is not satisfied, the reverse gap compensation motion is maintained.

[0010] Further, the composite judgment further comprises: Superimposing a micro-amplitude high-frequency oscillation command on the servo motor, and synchronously acquiring the load current signal; The load current signal is high-pass filtered to obtain a filtered load current signal; The filtered load current signal is subjected to frequency spectrum analysis to extract a current oscillation amplitude corresponding to the frequency of the micro-amplitude high-frequency oscillation instruction; It is judged whether the current oscillation amplitude continuously exceeds a preset rigid contact oscillation amplitude threshold.

[0011] Further, the judgment of whether the current oscillation amplitude continuously exceeds the preset rigid contact oscillation amplitude threshold comprises: Before performing the reverse gap compensation motion, a micro-amplitude high-frequency oscillation instruction is superimposed on the servo motor, and the load current signal of the servo motor is synchronously acquired; The load current signal is high-pass filtered to obtain a filtered load current signal, and the filtered load current signal is subjected to frequency spectrum analysis to obtain a current oscillation amplitude corresponding to the frequency of the micro-amplitude high-frequency oscillation instruction; The current oscillation amplitude is calibrated according to the machine tool operating parameters, and the rigid contact oscillation amplitude threshold is adjusted to a threshold under the current working condition according to the calibration, for the composite judgment.

[0012] Further, the current oscillation amplitude is calibrated according to the machine tool operating parameters, and the rigid contact oscillation amplitude threshold is adjusted to a threshold under the current working condition according to the calibration, comprising: The machine tool operating parameters are monitored, and the machine tool operating parameters include at least one of the ambient temperature, the cumulative running time, the cumulative axial stroke, the spindle speed and the feed speed; Based on the machine tool operating parameters and a preset parameter influence weight set, a comprehensive rigidity correction factor is calculated; The rigid contact oscillation amplitude threshold is dynamically adjusted according to the current oscillation amplitude and the comprehensive rigidity correction factor.

[0013] Further, the method further comprises: Before performing the reverse gap compensation motion, the actual gap value and the friction torque parameter of the ball screw are measured through a micro-amplitude detection motion, and a gap crossing optimization trajectory is generated according to the actual gap value and the friction torque parameter, the reverse gap compensation motion is completed along the gap crossing optimization trajectory, and after the reverse gap compensation motion is completed, it is smoothly switched to a normal double-closed-loop axial positioning control mode.

[0014] Further, based on the machine tool operating parameters and a preset parameter influence weight set, a comprehensive rigidity correction factor is calculated, comprising: Before performing the reverse gap compensation motion, a plurality of independent rigidity correction components are calculated according to the machine tool operating parameters and the parameter influence weight set; The non-linear combination coefficient is dynamically adjusted based on the machine tool operating parameters; The plurality of independent rigidity correction components are combined non-linearly by using the adjusted non-linear combination coefficients to obtain a comprehensive rigidity correction factor, and the non-linear combination is adaptive non-linear combination.

[0015] Further, the non-linear combination coefficients are dynamically adjusted based on the machine tool operating parameters, including: According to the machine tool operating parameters, the dynamic influence degree of each operating parameter on the non-linear combination coefficients is calculated; Based on the dynamic influence degree, the non-linear combination coefficients between the plurality of rigidity correction components are adjusted in real time to reflect the real coupling relationship between the rigidity correction components under the current working condition.

[0016] Further, according to the machine tool operating parameters, the dynamic influence degree of each operating parameter on the non-linear combination coefficients is calculated, including: For the measurement noise of the machine tool operating parameters, the monitored operating parameters are multi-point sampled and sliding average processed to obtain processed operating parameters; For the measurement delay of each operating parameter, the processed operating parameters are time stamp calibrated and synchronized to obtain calibrated operating parameters; Based on the calibrated operating parameters, the dynamic influence degree of each operating parameter on the non-linear combination coefficients is calculated.

[0017] Further, the dynamic influence degree of each operating parameter on the non-linear combination coefficients is calculated, including: Based on the historical operating data, a trend model is constructed to predict the change trend of the machine tool operating parameters to obtain an operating parameter trend; The operating parameter trend is combined with the calibrated operating parameters and the current oscillation amplitude to generate a predicted correction factor; According to the predicted correction factor, the dynamic influence degree of each operating parameter on the non-linear combination coefficients is feedforward compensation corrected to compensate for the dynamic deviation caused by the lag of each operating parameter.

[0018] In a second aspect, the application also discloses a numerical control lathe axial positioning control system, including: The driving module is configured to drive the servo motor to perform a reverse gap compensation motion at a preset small speed when the axial motion direction is reversed. The acquisition module is configured to acquire a position signal of the workbench and a load current signal of the servo motor at a synchronous sampling period during the reverse gap compensation motion. The judgment module is configured to perform a composite judgment based on the position signal and the load current signal: whether a change amount of the position signal along the command direction reaches a preset position threshold value within a preset duration window, and whether an increase amount of the load current signal relative to a reference current value before the reverse gap compensation motion reaches a preset current threshold value. A termination module is configured to determine that the mechanical gap has been eliminated, terminate the reverse gap compensation movement, and switch to a normal double closed-loop axial positioning control mode when all the composite judgment items are satisfied simultaneously. A switching module is configured to maintain the reverse gap compensation movement when any one of the composite judgment items is not satisfied.

[0019] Beneficial effects: The present application proposes a numerical control lathe axial positioning control method, the core of which is that when the axial movement direction is reversed, the servo motor is driven to perform a reverse gap compensation movement at a preset small speed, and the position signal of the workbench and the load current signal of the servo motor are acquired at a synchronous sampling period during the process. On this basis, a composite judgment mechanism based on the position signal and the load current signal is introduced. The problem of gap compensation misjudgment caused by intermittent fluctuations of the grating ruler signal in the prior art is solved, thereby avoiding the continuous "creeping" of the workbench near the target position. By introducing the load current signal as an auxiliary judgment basis, the deficiency of a single position signal when disturbed is made up, and the mechanical system stress state is more reliably reflected; the composite judgment mechanism can effectively identify and ignore false fluctuations, improving the accuracy and robustness of the judgment; and by accurately controlling the compensation termination time, smooth switching with the double closed-loop control mode is realized, avoiding under-compensation or over-compensation. In summary, the method significantly improves the axial positioning accuracy and machining stability of the numerical control lathe, and has important application value for precision manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A flowchart of a numerical control lathe axial positioning control method provided by the present application.

[0021] Figure 2 A module structure schematic diagram of a numerical control lathe axial positioning control system provided by the present application.

[0022] In the figure: 1, driving module; 2, acquisition module; 3, judgment module; 4, termination module; 5, switching module. DETAILED DESCRIPTION

[0023] The technical solutions in the present application will be described in detail below with reference to the accompanying drawings in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations. 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 claimed application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0024] It should be noted that similar reference numerals and letters refer to like items in the accompanying drawings, and once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings. Meanwhile, in the description of the present application, the terms "first", "second", and the like are used only to distinguish descriptions, and cannot be understood as indicating or implying relative importance.

[0025] With reference to Figure 1 The present application proposes a numerical control lathe axial positioning control method, comprising: S1000: when the axial movement direction is reversed, driving the servo motor to perform a reverse gap compensation movement at a preset small speed; S2000: during the reverse gap compensation movement, acquiring the position signal of the workbench and the load current signal of the servo motor at a synchronous sampling period; S3000: based on the position signal and the load current signal, performing a composite judgment: within a preset duration window, judging whether the change amount of the position signal along the command direction reaches a preset position threshold, and judging whether the increase amount of the load current signal relative to the reference current value before the reverse gap compensation movement reaches a preset current threshold; S4000: when all items of the composite judgment are satisfied at the same time, it is determined that the mechanical gap has been eliminated, the reverse gap compensation movement is terminated, and the normal double-closed-loop axial positioning control mode is switched to; S5000: when any one item of the composite judgment is not satisfied, the reverse gap compensation movement is maintained.

[0026] Specifically, the axial movement direction reversal is the process of switching the movement direction of the workbench of the numerical control lathe from one direction to the opposite direction when performing precise positioning or eliminating mechanical gap. For example, when the workbench switches from positive movement to negative movement, or from negative movement to positive movement, the axial movement direction reversal occurs.

[0027] The servo motor is an actuator that drives the workbench to perform precise movement in the numerical control lathe, and the output torque and speed of the servo motor are precisely regulated by the control system.

[0028] The reverse gap compensation movement refers to a segment of preset, small-range reverse movement performed to eliminate the inherent mechanical gap in the transmission chain such as ball screw when the axial movement direction is reversed. The purpose is to ensure that the gap in the transmission chain has been completely eliminated before the workbench starts actual displacement.

[0029] The preset small speed refers to the speed at which the servo motor is driven when performing reverse gap compensation movement, which is usually low to ensure the smoothness of the compensation process and the accuracy of the judgment. The synchronous sampling period refers to the time interval for data collection of the position signal of the workbench and the load current signal of the servo motor, which is kept consistent to ensure the correspondence of the data in time, facilitating subsequent compound judgment.

[0030] The position signal is usually provided by a position sensor such as a grating ruler or encoder, reflecting the actual position information of the workbench. The load current signal reflects the load size of the servo motor when driving the workbench movement, and its change is closely related to the force state of the mechanical system.

[0031] The preset duration window refers to a preset time for observing the changes in position signal and load current signal when making compound judgments. The preset position threshold is a reference value used to judge whether the position signal changes in the command direction by a certain amount.

[0032] The preset current threshold is a reference value used to judge whether the load current signal increases by a certain amount. The reference current value is the load current value of the servo motor under no-load or stable state before the reverse gap compensation movement starts, serving as a reference for subsequent judgment of load current increase.

[0033] The double closed-loop axial positioning control mode is a high-precision control strategy, usually including a position loop and a speed loop, which realizes precise control of the workbench position through feedback from sensors such as grating rulers and encoders.

[0034] Specifically, when reversing the axial movement direction, the servo motor is driven to perform reverse gap compensation movement at a preset small speed to eliminate mechanical gap. For example, when the workbench of a numerical control lathe needs to move accurately from one position to another and needs to change direction during the movement, the system will start gap compensation to ensure positioning accuracy. At this time, the servo motor will move slightly in the opposite direction at a preset, relatively small speed, for example, 10 mm per minute. This small speed movement helps the system overcome mechanical gap more smoothly and provides stable conditions for subsequent signal collection and judgment.

[0035] During the reverse gap compensation motion, the system acquires the position signal of the worktable and the load current signal of the servo motor at a synchronous sampling period. For example, a high-precision grating ruler can be used as a position sensor to collect real-time position data of the worktable at a frequency of once per millisecond. At the same time, through the current sensor inside the servo driver, real-time load current data of the servo motor is collected at the same frequency of once per millisecond. This synchronous sampling ensures the accurate correspondence of position changes and current changes in time, providing a reliable data basis for subsequent compound judgment.

[0036] Next, compound judgment is performed based on the acquired position signal and load current signal. The compound judgment includes two main aspects: within a preset duration window, it is judged whether the amount of change of the position signal in the command direction reaches a preset position threshold, and it is judged whether the amount of increase of the load current signal relative to the reference current value before the reverse gap compensation motion reaches a preset current threshold. For example, the system sets a 50-millisecond duration window. Within this window, if the cumulative amount of change of the position signal of the grating ruler in the command direction (i.e., the direction of the reverse gap compensation motion) reaches the preset 0.005-millimeter position threshold, it indicates that the worktable may have started to move in reality. At the same time, if the load current signal of the servo motor increases by 0.2 amperes relative to the reference current value (e.g., 0.5 amperes when idle) before the compensation motion, reaching the preset 0.2-ampere current threshold, it indicates that the motor is overcoming mechanical resistance and may have contacted the other side of the ball screw. Both conditions need to be met simultaneously.

[0037] When all items of the compound judgment are met simultaneously, the system determines that the mechanical gap has been eliminated, and terminates the reverse gap compensation motion and switches to the normal double-closed-loop axial positioning control mode. For example, if the conditions of the above-mentioned position signal and load current signal are met simultaneously within the 50-millisecond window, the system will immediately stop the reverse gap compensation motion of the servo motor, and switch its control mode to the high-precision double-closed-loop control mode for accurate position tracking and positioning.

[0038] On the contrary, when any one of the compound judgment items does not meet, the system will maintain the reverse gap compensation motion and ignore the intermittent small fluctuations of the position signal alone. For example, if within the 50-millisecond window, the amount of change of the position signal reaches the threshold, but the amount of increase of the load current signal does not reach the threshold, or vice versa, the system will continue to perform the reverse gap compensation motion. In addition, if only the position signal has intermittent small fluctuations (e.g., due to grating contamination), but the load current signal does not have a corresponding significant increase, the system will ignore the fluctuations of the position signal, avoiding making false judgments due to the unreliability of a single signal.

[0039] The application effectively solves the misjudgment problem caused by the fluctuation of the grating ruler signal in the gap compensation process by introducing the load current signal of the servo motor as an auxiliary judgment basis and combining the position signal for compound judgment. Compared with the traditional method which only relies on the position signal, the scheme of the application has obvious advantages. When the grating ruler signal is polluted or interfered, the traditional method is easy to misjudge the intermittent small fluctuation as the actual displacement of the workbench, thereby causing the gap compensation to end early and introducing positioning deviation. This deviation can cause the double closed-loop control system to appear "creeping" near the target position, which seriously affects the machining precision.

[0040] Further, in another embodiment of the application, it is proposed that the compound judgment further includes: S3100: superimposing a micro-amplitude high-frequency oscillation instruction on the servo motor, and synchronously acquiring a load current signal; S3200: performing high-pass filtering processing on the load current signal to obtain a filtered load current signal; S3300: performing spectrum analysis on the filtered load current signal to extract a current oscillation amplitude corresponding to the frequency of the micro-amplitude high-frequency oscillation instruction; S3400: judging whether the current oscillation amplitude continuously exceeds a preset rigid contact oscillation amplitude threshold.

[0041] Specifically, superimposing a micro-amplitude high-frequency oscillation instruction on the servo motor means that, in the control instruction of the servo motor, a periodic signal with a small amplitude and a high frequency is additionally added in addition to the normal reverse gap compensation motion instruction. The purpose of the instruction is to actively excite the mechanical transmission chain to produce a detectable dynamic response in the gap elimination process. Synchronously acquiring a load current signal means that the actual load current of the servo motor is acquired at the same sampling period or synchronous clock when the oscillation instruction is superimposed, so as to ensure the time correspondence between the oscillation instruction and the current response.

[0042] Performing high-pass filtering processing on the load current signal aims to separate the response component caused by the micro-amplitude high-frequency oscillation instruction from the original load current signal, while suppressing the low-frequency motion current, the direct current bias and other low-frequency noises. Thus, the filtered load current signal can be obtained, which mainly reflects the dynamic characteristics of the mechanical system under high-frequency excitation. In actual application, the spectrum analysis is performed on the filtered load current signal, for example, through the fast Fourier transform (FFT) method, so that the current oscillation amplitude corresponding to the frequency of the micro-amplitude high-frequency oscillation instruction can be accurately extracted. The amplitude is a key index for measuring the rigid response of the mechanical system under specific high-frequency excitation.

[0043] The judgment of whether the current oscillation amplitude continuously exceeds the preset rigid contact oscillation amplitude threshold value refers to comparing the extracted current oscillation amplitude with a preset threshold value. When the ball screw nut pair transitions from the loose state with clearance to the rigid contact state, the overall stiffness of the mechanical system will significantly increase, resulting in a significant increase in the load current oscillation amplitude generated by the servo motor under the same micro-amplitude high-frequency oscillation instruction. Therefore, the threshold value is set as a critical value that can distinguish between the clearance state and the rigid contact state. Continuous exceeding of the threshold value indicates that the mechanical system has stably entered the rigid contact state, avoiding misjudgment caused by transient noise or accidental fluctuations.

[0044] The scheme of the present application can more accurately detect the elimination of mechanical clearance by introducing a micro-amplitude high-frequency oscillation instruction and analyzing the load current response of the servo motor. When the ball screw nut pair is in the clearance state, the oscillation amplitude of the load current of the servo motor generated by the micro-amplitude high-frequency oscillation instruction is relatively small due to the presence of looseness, because the energy is absorbed or dissipated by the clearance. However, once the ball screw nut pair achieves rigid contact, the stiffness of the mechanical transmission chain significantly increases, and the response characteristics of the system to high-frequency excitation change, resulting in a significant increase in the load current oscillation amplitude of the servo motor under the same micro-amplitude high-frequency oscillation instruction. Through high-pass filtering processing, this high-frequency response can be effectively isolated, and its amplitude can be accurately extracted through frequency spectrum analysis. Comparing this amplitude with the preset rigid contact oscillation amplitude threshold value can provide a more sensitive and reliable judgment basis for the rigid contact state of the mechanical system. This method can effectively make up for the shortcomings of relying solely on position change and load current increase, especially in the critical state where the clearance is about to be eliminated, and can provide clearer signal differentiation.

[0045] In some preferred embodiments, as a specific implementation: it is assumed that during the reverse gap compensation movement, a micro-amplitude high-frequency oscillation command with a frequency of 200 Hz and an amplitude of 0.05 A is superimposed on the servo motor. At the same time, the load current signal of the servo motor is synchronously acquired at a sampling frequency of 1 kHz. Subsequently, the acquired load current signal is subjected to high-pass filtering processing, for example, a digital high-pass filter with a cutoff frequency of 150 Hz is used to filter out the low-frequency motion current and the direct current component. The filtered signal is subjected to fast Fourier transform (FFT) for spectral analysis, and the current oscillation amplitude corresponding to the 200 Hz frequency component is extracted. When the gap is not eliminated, the amplitude may fluctuate around 0.01 A; when the ball screw nut pair realizes rigid contact, due to the increase in mechanical stiffness, the amplitude will rapidly rise and stabilize above 0.03 A. At this time, the preset rigid contact oscillation amplitude threshold can be set to 0.025 A. When the current oscillation amplitude is continuously detected to be higher than 0.025 A, for example, higher than the threshold for 10 consecutive sampling periods, it is determined that the mechanical gap has been eliminated, and the reverse gap compensation movement is terminated and switched to the normal double-closed-loop axial positioning control mode. This judgment mechanism based on high-frequency response can effectively distinguish the true rigid contact state of the mechanical system from the transient signal caused by friction or slight collision, ensuring the accuracy of gap elimination.

[0046] Further, in another embodiment of the present application, S3400 comprises: S3410: before performing the reverse gap compensation movement, superimposing a micro-amplitude high-frequency oscillation command on the servo motor, and synchronously acquiring the load current signal of the servo motor; S3420: high-pass filtering the load current signal to obtain a filtered load current signal, and performing spectral analysis on the filtered load current signal to obtain a current oscillation amplitude corresponding to the frequency of the micro-amplitude high-frequency oscillation command; S3430: calibrating the current oscillation amplitude according to the machine tool operating parameters, and adjusting the rigid contact oscillation amplitude threshold to a threshold value under the current working condition according to the calibration, for compound judgment.

[0047] Specifically, before the reverse gap compensation motion starts, the inherent vibration response of the mechanical system under rigid contact state can be excited by superimposing a micro high-frequency oscillation command on the servo motor. The synchronously acquired load current signal will contain a current oscillation component corresponding to the frequency of the oscillation command. Through high-pass filtering processing, the direct current component and low-frequency noise can be effectively removed, so that the current oscillation amplitude corresponding to the frequency of the micro high-frequency oscillation command is more prominent. Subsequently, the filtered load current signal is subjected to frequency spectrum analysis, and the current oscillation amplitude corresponding to the frequency of the micro high-frequency oscillation command can be accurately extracted. Among them, the machine tool operating parameters can be understood as various environmental or working condition parameters that affect the mechanical rigidity characteristics of the machine tool, such as at least one of the environmental temperature, the cumulative running time of the machine tool, the cumulative axial stroke, the spindle speed and the feed speed. Changes in these parameters will directly or indirectly affect the rigidity of the mechanical transmission chain such as the ball screw pair and the bearing, thereby changing the current oscillation amplitude generated under rigid contact. In practical applications, the calibration of the current oscillation amplitude according to the machine tool operating parameters means that the measured current oscillation amplitude is corrected according to the actual operating state of the machine tool to eliminate or reduce the measurement error or deviation caused by changes in the operating parameters. For example, when the environmental temperature rises, the mechanical parts may expand due to heat, causing the rigidity to decrease slightly, and the measured current oscillation amplitude needs to be appropriately corrected. Further, the rigid contact oscillation amplitude threshold is adjusted to the threshold under the current working condition, and the purpose is to enable the judgment threshold to dynamically adapt to the actual working state of the machine tool. This means that the threshold is no longer a fixed constant, but is dynamically calculated and updated according to the real-time monitored machine tool operating parameters, so as to ensure that the threshold can accurately represent the current oscillation amplitude characteristics of the mechanical system under rigid contact state under different working conditions.

[0048] The scheme of the present application effectively solves the problem of inaccurate judgment of the traditional fixed threshold under variable working conditions by introducing machine tool operating parameters to calibrate the current oscillation amplitude and dynamically adjusting the rigid contact oscillation amplitude threshold. Specifically, when the machine tool operating parameters change, for example, the temperature rises or the wear increases, the rigidity of the mechanical system will change, causing the current oscillation amplitude generated under rigid contact to change. By pre-acquiring and analyzing the load current signal before the reverse gap compensation motion, and combining the machine tool operating parameters to calibrate the obtained current oscillation amplitude, the real rigidity state of the mechanical system under the current working condition can be more accurately reflected. On this basis, the rigid contact oscillation amplitude threshold is dynamically adjusted to the actual threshold under the current working condition, ensuring that the threshold used in the composite judgment is highly matched with the actual physical state of the machine tool. Thus, false positives or false negatives caused by changes in the environment or working conditions are avoided, making the gap elimination judgment more accurate and reliable.

[0049] In some preferred embodiments, the following is illustrated by a specific example: Suppose that before the reverse gap compensation movement of a certain CNC lathe, the system monitors that the ambient temperature is 25℃ and the cumulative running time is 1000 hours. At this time, a micro-amplitude high-frequency oscillation command with a frequency of 500Hz and an amplitude of 0.1V is superimposed on the servo motor. The load current signal of the servo motor is synchronously acquired, and after high-pass filtering and spectrum analysis, the current oscillation amplitude corresponding to the frequency of 500Hz is 0.05A. According to the preset temperature-rigidity correction model and the running time-rigidity correction model, the system calculates that the current oscillation amplitude of 0.05A needs to be calibrated upward by 5% under the current working condition, that is, the calibrated current oscillation amplitude is 0.0525A. At the same time, based on these machine tool running parameters, the system dynamically calculates and adjusts the rigidity contact oscillation amplitude threshold. For example, under the standard working condition (20℃, new machine), the threshold value may be set to 0.06A. But under the current working condition of 25℃ and 1000 hours of running, the system calculates a comprehensive rigidity correction factor according to the preset parameter influence weight set, and adjusts the threshold value to 0.058A accordingly. When the calibrated current oscillation amplitude is continuously monitored to exceed 0.058A during the subsequent reverse gap compensation movement, it is determined that the mechanical gap has been eliminated, so as to terminate the reverse gap compensation movement and switch to the normal double-closed-loop axial positioning control mode. This dynamic adjustment mechanism ensures that when the actual running state of the machine tool changes, the judgment of gap elimination is still accurate and reliable.

[0050] Further, in another embodiment of the present application, S3430 comprises: S3431: monitoring machine tool running parameters, the machine tool running parameters comprising at least one of ambient temperature, cumulative running time, cumulative axial stroke, spindle speed and feed speed; S3432: calculating a comprehensive rigidity correction factor based on the machine tool running parameters and the preset parameter influence weight set; S3433: dynamically adjusting the rigidity contact oscillation amplitude threshold according to the current oscillation amplitude and the comprehensive rigidity correction factor.

[0051] Specifically, the machine tool operating parameters refer to various measurable physical quantities or operating indexes that affect the rigidity state of the mechanical system. Real-time monitoring of these parameters is crucial for accurately assessing the current working condition of the machine tool. For example, the ambient temperature can affect the thermal expansion of materials and the viscosity of lubricating oil, thereby changing the mechanical clearance and friction characteristics; the cumulative running time or cumulative axial stroke can reflect the degree of wear of mechanical components, which can lead to increased clearance or decreased rigidity; the spindle speed and feed speed directly affect the cutting force, vibration, and bearing load, all of which can change the dynamic rigidity of the system. By monitoring at least one of the ambient temperature, cumulative running time, cumulative axial stroke, spindle speed, and feed speed, key information affecting the rigidity state of the machine tool can be comprehensively obtained.

[0052] wherein the comprehensive rigidity correction factor is a comprehensive index quantifying the current rigidity state of the machine tool. This factor is calculated by combining multiple machine tool operating parameters and a preset parameter influence weight set. The parameter influence weight set is used to represent the relative importance or sensitivity of different operating parameters on the rigidity state of the machine tool. For example, in certain working conditions, the influence of spindle speed on rigidity may be much greater than that of ambient temperature, so the weight corresponding to the spindle speed will be higher. By weighting and combining each operating parameter with its corresponding weight, a correction factor can be obtained that can comprehensively reflect the overall rigidity change of the machine tool under the current working condition.

[0053] In practical applications, the dynamic adjustment of the rigidity contact oscillation amplitude threshold is based on the current obtained current oscillation amplitude and the calculated comprehensive rigidity correction factor. The current oscillation amplitude directly reflects the response of the mechanical system under a micro-amplitude high-frequency oscillation command and is a direct basis for judging rigidity contact. The comprehensive rigidity correction factor provides background information for calibrating this amplitude. By combining the current oscillation amplitude with the comprehensive rigidity correction factor, the preset rigidity contact oscillation amplitude threshold can be adjusted in real time and adaptively. The purpose of this adjustment is to ensure that the threshold used can accurately reflect the actual mechanical contact characteristics of the machine tool under complex working conditions such as current ambient temperature, wear degree, and load conditions, thereby avoiding false positives or false negatives caused by inappropriate thresholds.

[0054] The scheme of the present application realizes dynamic adjustment of the rigid contact oscillation amplitude threshold by introducing monitoring of multiple machine tool operating parameters and calculating a comprehensive rigidity correction factor based on these parameters and preset weights. The working principle is that the traditional fixed threshold or simple calibrated threshold cannot adapt to the complex mechanical property changes of the machine tool under different operating conditions. For example, when the ambient temperature rises, thermal expansion of mechanical components may occur, resulting in a decrease in the actual gap or an increase in the friction force. If the threshold at low temperature is still used, it may lead to misjudgment. By monitoring parameters such as ambient temperature, cumulative running time, cumulative axial travel, spindle speed and feed speed, the system can sense the working condition changes of the machine tool in real time. These parameters are input into a calculation model based on a preset parameter influence weight set to generate a comprehensive rigidity correction factor. The correction factor quantifies the comprehensive influence of the current working condition on the mechanical system rigidity. Finally, the current measured current oscillation amplitude is combined with the comprehensive rigidity correction factor to dynamically correct the rigid contact oscillation amplitude threshold. This dynamic correction mechanism makes the threshold no longer static, but can be adaptively adjusted according to the actual operating state of the machine tool, thereby ensuring that the determined mechanical gap elimination point has higher accuracy and reliability under any working condition.

[0055] In some preferred embodiments, the following is described by a specific example: Suppose that during the operation of a certain numerical control lathe, the system monitors that the ambient temperature rises from 20℃ to 35℃, and the spindle speed increases from 1000rpm to 5000rpm. In the preset parameter influence weight set, the weight of the ambient temperature is 0.3, and the weight of the spindle speed is 0.5. The system first calculates the correction component of the rigidity caused by the ambient temperature (for example, the rigidity correction factor increases by 0.01 for every 1℃ increase in temperature) and the correction component of the rigidity caused by the spindle speed (for example, the rigidity correction factor increases by 0.02 for every 1000rpm increase in speed) according to these parameter changes. Then, based on these correction components and their respective weights, a comprehensive rigidity correction factor is calculated. For example, if the initial rigid contact oscillation amplitude threshold is X, under the combined influence of the temperature rise and the speed increase, the calculated comprehensive rigidity correction factor is 1.1. At this time, the system combines the current current oscillation amplitude with this correction factor to dynamically adjust the rigid contact oscillation amplitude threshold to X*1.1 to adapt to the actual mechanical rigidity state under the current high temperature and high speed. This dynamic adjustment ensures that even when the working condition changes significantly, the system can accurately determine whether the mechanical gap has been eliminated, thereby ensuring the accuracy and stability of the axial positioning.

[0056] Further, in another embodiment of the present application, the numerical control lathe axial positioning control method further comprises: S6000: Before performing the reverse gap compensation movement, measure the actual gap value and friction torque parameters of the ball screw through a micro-probing movement, generate a gap crossing optimization trajectory according to the actual gap value and friction torque parameters, complete the reverse gap compensation movement along the gap crossing optimization trajectory, and smoothly switch to the normal double closed-loop axial positioning control mode after the completion of the reverse gap compensation movement.

[0057] Specifically, the micro-probing movement refers to a small reciprocating movement of the worktable within the gap range by applying a very small displacement command to the servo motor before the reverse gap compensation movement starts. During this process, the critical point where the ball screw contacts from one side to the other side can be accurately captured, thereby measuring the actual gap value of the ball screw. At the same time, by monitoring the current or torque response of the servo motor, the friction torque parameters of the ball screw during gap crossing, such as static friction torque and dynamic friction torque, can be evaluated.

[0058] Wherein, generating a gap crossing optimization trajectory according to the actual gap value and friction torque parameters can be understood as dynamically planning a motion trajectory that is most suitable for the current working condition based on the actual measured mechanical characteristics. For example, the trajectory can be a nonlinear velocity curve that crosses the gap at a faster speed and smoothly decelerates when about to contact, in order to avoid impact and ensure accurate contact. The purpose is to ensure the elimination of the gap while minimizing the compensation time and reducing mechanical wear.

[0059] In practical applications, completing the reverse gap compensation movement along the gap crossing optimization trajectory specifically means that the servo motor no longer simply moves at a preset small speed, but strictly follows the pre-generated optimization trajectory for movement. For example, the control system will accurately control the output of the servo motor according to the speed and acceleration instructions in the optimization trajectory, so that the worktable smoothly and efficiently crosses the mechanical gap according to the planned path. After the completion of the reverse gap compensation movement, it is smoothly switched to the normal double closed-loop axial positioning control mode, which aims to ensure that after the gap is eliminated, the machine tool can seamlessly enter the high-precision positioning and machining state, avoiding transient impact or position deviation caused by control mode switching, thereby ensuring machining precision and machine tool stability.

[0060] The scheme of the present application can accurately measure the actual backlash value and friction torque parameters of the ball screw by introducing a micro-probing motion before the reverse gap compensation motion. It is precisely because of obtaining these real-time and accurate mechanical characteristic data that the system can dynamically generate a gap crossing optimization trajectory according to the current working condition. The optimization trajectory fully considers the gap size and friction characteristics, so as to cross the gap with the most appropriate speed and acceleration curve, avoiding the low efficiency or impact problem that may be caused by the traditional fixed small speed compensation. By performing the compensation motion along the optimization trajectory, the mechanical gap can be eliminated more quickly and stably, and after the compensation is completed, the smooth switching mechanism is used to ensure the seamless connection of the control modes, effectively avoiding the transient disturbance caused by mode switching, thereby ensuring the accuracy and stability of the subsequent positioning control.

[0061] In some preferred embodiments, the following is described by a specific example: Suppose that the mechanical backlash and friction characteristics of a ball screw of a CNC lathe may change slightly after a long time of operation. When the axial motion direction needs to be reversed, first, the control system triggers a micro-probing motion. For example, the servo motor is instructed to perform a small reciprocating motion in the range of ±0.01 mm at a speed of 0.1 mm / s, while the high-precision encoder records the position of the worktable, and the current sensor records the load current of the servo motor. By analyzing the mutation points of the position and current signals, the system accurately measures that the actual backlash value of the current ball screw is 0.05 mm, and there is a static friction torque of 0.5 Nm when crossing the gap.

[0062] Based on these measurement data, the control system dynamically generates a gap crossing optimization trajectory. For example, the trajectory can be designed as follows: in the initial 0.02 mm range of the gap, accelerate to cross at a speed of 0.5 mm / s; in the next 0.02 mm range, the speed remains at 0.5 mm / s; in the last 0.01 mm before contact, smoothly decelerate to 0.1 mm / s to ensure flexible contact. Subsequently, the servo motor drives the worktable to perform a reverse gap compensation motion strictly according to the optimization trajectory. When the worktable completes the gap crossing according to the optimization trajectory and reaches the preset contact state, the control system immediately and smoothly switches to the normal double-closed-loop axial positioning control mode, so that the machine tool can quickly and accurately enter the next machining instruction, and the whole process is efficient and impact-free.

[0063] Further, in another embodiment of the present application, S3432 comprises: A1000: before performing the reverse gap compensation motion, calculating a plurality of independent rigidity correction components according to the machine tool operating parameters and the parameter influence weight set; A2000: dynamically adjusting non-linear combination coefficients based on machine tool operating parameters; A3000: non-linearly combining multiple independent rigidity correction components using the adjusted non-linear combination coefficients to obtain a comprehensive rigidity correction factor, wherein the non-linear combination is adaptive non-linear combination.

[0064] Specifically, the multiple independent rigidity correction components refer to correction values calculated for different machine tool operating parameters (such as ambient temperature, cumulative running time, cumulative axial travel, spindle speed, and feed speed, etc.) to reflect the influence of each parameter on mechanical rigidity. For example, a temperature correction component can be calculated for ambient temperature, and a speed correction component can be calculated for spindle speed, etc. The purpose is to decompose the complex comprehensive influence into sub-items that can be independently analyzed and calculated. Among them, the non-linear combination coefficients can be understood as parameters for adjusting the interaction strength between different rigidity correction components. These coefficients are not fixed but dynamically adjusted based on machine tool operating parameters to adapt to different working conditions. The purpose is to more accurately simulate the non-linear coupling effect of each operating parameter on mechanical rigidity. In practical applications, adaptive non-linear combination refers to a non-linear function that can automatically adjust the combination method and / or combination coefficients according to real-time or historical operating data. For example, machine learning algorithms such as neural networks, fuzzy logic, and support vector machines can be used, or parameter optimization can be performed based on pre-set non-linear function models (such as polynomials, exponential functions, etc.) to realize the non-linear combination of multiple rigidity correction components. The purpose is to ensure that the comprehensive rigidity correction factor can accurately reflect the actual mechanical rigidity state under the current complex working condition.

[0065] The scheme of the present application effectively solves the problem of insufficient rigidity correction factor calculation accuracy caused by the difficulty of accurately capturing the complex non-linear coupling relationship between parameters in traditional methods by decomposing the calculation of the comprehensive rigidity correction factor into multiple independent rigidity correction components, introducing non-linear combination coefficients dynamically adjusted based on machine tool operating parameters, and using adaptive non-linear combination. Specifically, by calculating multiple independent rigidity correction components, the individual influence of each operating parameter on mechanical rigidity can be quantified more meticulously. The dynamic adjustment of non-linear combination coefficients based on machine tool operating parameters enables these independent components to be combined in a manner more consistent with physical laws according to the actual working conditions, avoiding the limitations of fixed weights or linear combination. Finally, the introduction of adaptive non-linear combination further enhances the adaptability of the system to complex working conditions and the accuracy of the correction factor, ensuring that the comprehensive rigidity correction factor can accurately reflect the actual mechanical state under the current working condition.

[0066] In some preferred embodiments, the following is described through a specific example: Assume that the machine tool operating parameters include ambient temperature, cumulative running time, and spindle speed. Before performing the reverse gap compensation motion, the system can calculate three independent rigidity correction components according to these parameters: a temperature correction component, a time correction component, and a speed correction component. For example, the temperature correction component can be a function inversely proportional to the ambient temperature, the time correction component can be a function proportional to the cumulative running time (reflecting wear), and the speed correction component can be a function related to the spindle speed (reflecting vibration effects). Further, based on the current machine tool operating parameters, the system can dynamically adjust the nonlinear combination coefficients. For example, a neural network-based model can be preset, which takes the ambient temperature, cumulative running time, and spindle speed as input and outputs three nonlinear combination coefficients. These coefficients reflect the relative weights and nonlinear coupling relationships of temperature, time, and speed on the overall rigidity under the current working condition. Finally, the adaptive nonlinear combination of multiple independent rigidity correction components is performed using the adjusted nonlinear combination coefficients to obtain the comprehensive rigidity correction factor. This adaptive nonlinear combination method can more accurately capture the complex interactions between different operating parameters, so that the comprehensive rigidity correction factor can accurately reflect the actual mechanical state under the current working condition, providing a more reliable basis for the dynamic adjustment of the rigidity contact oscillation amplitude threshold.

[0067] Further, in another embodiment of the present application, A2000 includes: A2100: calculating the dynamic influence degree of each operating parameter on the nonlinear combination coefficient according to the machine tool operating parameters; A2200: based on the dynamic influence degree, real-time adjusting the nonlinear combination coefficients between multiple rigidity correction components to reflect the real coupling relationship between each rigidity correction component under the current working condition.

[0068] Specifically, "calculating the dynamic influence degree of each operating parameter on the nonlinear combination coefficient" means that the monitored machine tool operating parameters such as ambient temperature, cumulative running time, cumulative axial travel, spindle speed, and feed speed are analyzed in depth to quantify the specific contribution and influence weight of each parameter on the nonlinear combination coefficient under the current working condition. This can be achieved by means of a pre-established mathematical model, machine learning algorithms (e.g., regression analysis, neural network), or a rule base based on expert experience, with the purpose of obtaining a dynamic weight set that accurately reflects the influence of each parameter.

[0069] Wherein, "adjusting the nonlinear combination coefficients between the plurality of rigid correction components in real time based on the dynamic influence degree" can be understood as, once the dynamic influence degree of each operating parameter is obtained, the system will update and optimize the nonlinear combination coefficients used to combine each rigid correction component in real time according to the dynamic influence degree. For example, if the influence of a certain operating parameter (such as spindle speed) on mechanical rigidity is significantly enhanced under the current working condition, the weight or mode of action of the rigid correction component related to the parameter in the nonlinear combination will be adjusted accordingly to ensure that its embodiment in the comprehensive rigidity correction factor is more accurate.

[0070] In practical application, "reflecting the real coupling relationship between the rigid correction components under the current working condition" specifically refers to that through the calculation and real-time adjustment of the above-mentioned dynamic influence degree, the nonlinear combination coefficients can accurately simulate and express the interaction and dependence relationship between different rigid correction components under the current actual operating condition. For example, under high temperature and high speed working condition, the rigidity change caused by thermal deformation and the rigidity change caused by dynamic load may have specific synergistic or antagonistic effect, and the present scheme aims to adjust the combination coefficients to make these complex coupling relationships be truly and finely reflected in the comprehensive rigidity correction factor.

[0071] The scheme of the present application solves the problem of inaccurate parameter coupling relationship in the traditional method in dealing with complex working conditions by introducing the calculation of the dynamic influence degree of each operating parameter and adjusting the nonlinear combination coefficients in real time based thereon. It is precisely because the dynamic contribution of each machine tool operating parameter to the nonlinear combination coefficients can be accurately quantified, and the combination mode between the rigid correction components is adjusted accordingly, that the comprehensive rigidity correction factor can more truly and finely reflect the actual mechanical state under the current working condition. This mechanism ensures that the nonlinear combination coefficients can be adaptively adjusted when the machine tool operating parameters change, thereby avoiding the compensation error caused by the insufficient understanding of the parameter coupling relationship.

[0072] In some preferred embodiments, the following is described by a specific example: Suppose that the environment temperature, spindle speed and feed speed and other machine tool operating parameters change continuously during the machining process of a numerical control lathe. In order to accurately adjust the nonlinear combination coefficients, the following methods can be used: First, a machine learning model based on historical operating data and expert knowledge is established, such as a multilayer perceptron neural network. The input of the model includes the current machine tool operating parameters (such as environment temperature, spindle speed, feed speed), and the output is the dynamic influence degree of each operating parameter on the nonlinear combination coefficients. For example, when the environment temperature rises, the model may output a higher influence degree value, indicating that the temperature should be more sensitive to the adjustment of the nonlinear combination coefficients.

[0073] Secondly, during the reverse gap compensation movement, the system monitors the above-mentioned machine tool operating parameters in real time and inputs these parameters into the pre-trained machine learning model. The model calculates the dynamic influence degree of the ambient temperature, spindle speed, feed speed, etc. on the nonlinear combination coefficient according to the current operating parameters.

[0074] Finally, based on these calculated dynamic influence degrees, the system adjusts the nonlinear combination coefficient between multiple rigidity correction components (for example, one component reflects the rigidity change caused by temperature, and another component reflects the rigidity change caused by spindle speed) in real time. For example, if the model indicates that in the current high-temperature high-speed working condition, the influence weight of spindle speed on rigidity should be increased, and the influence weight of ambient temperature should be slightly reduced, then the nonlinear combination coefficient will be adjusted accordingly. This adjustment ensures that the comprehensive rigidity correction factor can accurately reflect the complex interaction and coupling relationship between different physical factors (reflected by the rigidity correction component) under the current working condition, thereby providing a more accurate basis for the dynamic adjustment of the rigidity contact oscillation amplitude threshold.

[0075] Further, in another embodiment of the present application, A2100 includes: A2110: For the measurement noise of the machine tool operating parameters, the monitored operating parameters are multi-point sampled and sliding average processed to obtain processed operating parameters; A2120: For the measurement delay of each operating parameter, the processed operating parameters are time stamp calibrated and synchronized to obtain calibrated operating parameters; A2130: Based on the calibrated operating parameters, the dynamic influence degree of each operating parameter on the nonlinear combination coefficient is calculated.

[0076] Specifically, for the measurement noise of the machine tool operating parameters, by multi-point sampling and sliding average processing of the monitored operating parameters, the influence of random noise on the measurement results can be effectively suppressed. Multi-point sampling refers to continuously measuring the same parameter multiple times within a short period of time to obtain a group of data points. Sliding average processing refers to averaging the continuous sampling points, for example, using a moving average filter, by averaging the data within a certain time window, thereby smoothing the data curve, reducing the amplitude of instantaneous noise, and obtaining more stable and reliable processed operating parameters. The purpose is to improve the signal-to-noise ratio of the operating parameter data and provide more accurate input for subsequent calculations.

[0077] The measurement delay for each operating parameter is calibrated and synchronized by time stamping and synchronization processing, which ensures the time consistency between different operating parameters. The measurement delay can be caused by sensor response time, data acquisition system processing speed, or data transmission path difference, etc. Time stamping refers to attaching a precise time label to each measurement data to record its acquisition time. Synchronization processing refers to aligning the data of different parameters according to these time stamps, for example, by interpolation or resampling, etc., so that at the same time point, all relevant operating parameter data can be accurately obtained and used, and the calibrated operating parameters are obtained. The purpose is to eliminate the error caused by asynchronous data acquisition and transmission, and ensure that the parameter data used in calculating the dynamic influence degree is time matched with each other.

[0078] In practical applications, the processed operating parameters refer to the machine tool operating parameter data after noise suppression, such as the environmental temperature, cumulative running time, cumulative axial travel, spindle speed and feed speed after sliding average filtering. The calibrated operating parameters refer to the operating parameter data that has been further time stamped and synchronized to ensure time consistency based on the processed operating parameters.

[0079] The scheme of the present application improves the quality of operating parameter data from the source by noise suppression and time synchronization processing of machine tool operating parameters. Specifically, multi-point sampling and sliding average processing can effectively filter out random noise generated during measurement, making the obtained operating parameter data smoother and more realistic, and avoiding misjudgment caused by noise. At the same time, time stamping and synchronization processing solve the measurement delay problem that may exist between different sensors or data channels, ensuring that all relevant operating parameter data can accurately reflect the machine tool working condition at the same time when calculating the dynamic influence degree of each operating parameter on the nonlinear combination coefficient. It is precisely because of the provision of high-precision and high-synchronization operating parameter data that the subsequently calculated dynamic influence degree of each operating parameter is more accurate, so that the nonlinear combination coefficient can be adjusted more accurately to truly reflect the coupling relationship between each rigid correction component under the current working condition.

[0080] In some preferred embodiments, the following is described by a specific example: Suppose we need to monitor three machine tool operating parameters: environmental temperature, spindle speed and feed speed. For the measurement noise of the environmental temperature, the temperature sensor can be configured to sample every 100 milliseconds, continuously collect 10 data points, and then perform sliding average processing on the 10 data points, for example, calculate their arithmetic mean, to obtain a smooth environmental temperature value.

[0081] For the measurement of spindle speed and feed speed, there may be microsecond-level delays due to different encoders or sensors and different data transmission paths. To this end, a high-precision timestamp is attached to each speed and feed data point during data acquisition. Before calculating the dynamic influence of each operating parameter, the system synchronizes the spindle speed and feed speed data based on these timestamps. For example, based on the sampling time point of the ambient temperature data, the spindle speed and feed speed data are adjusted to the same time point as the ambient temperature data by linear interpolation or nearest neighbor interpolation, etc., to obtain the calibrated operating parameters.

[0082] Based on these calibrated operating parameters after noise suppression and time synchronization processing, the system can more accurately calculate the dynamic influence of ambient temperature, spindle speed and feed speed on the non-linear combination coefficient, and then guide the real-time adjustment of the non-linear combination coefficient.

[0083] Further, in another embodiment of the present application, A2130 includes: A2131: Construct a trend model based on historical operating data to predict the change trend of the machine tool operating parameters, and obtain the operating parameter trend; A2132: Combine the operating parameter trend with the calibrated operating parameters and current oscillation amplitude to generate a prediction correction factor; A2133: According to the prediction correction factor, feed forward compensation correction is performed on the dynamic influence of each operating parameter on the non-linear combination coefficient to compensate for the dynamic deviation caused by the lag of each operating parameter.

[0084] Specifically, constructing a trend model based on historical operating data means that the system continuously collects and stores the historical operating data of the numerical control lathe under different working conditions, such as ambient temperature, cumulative running time, cumulative axial stroke, spindle speed and feed speed, etc. These historical data can be used to train various prediction models, such as time series models (e.g. ARIMA, exponential smoothing), machine learning models (e.g. support vector machines, neural networks) or statistical regression models. Through these models, the change trend of the machine tool operating parameters in the future can be predicted, and the operating parameter trend can be obtained. The purpose is to predict the dynamic change of the machine tool operating parameters in advance, and to provide a basis for subsequent compensation.

[0085] The running parameter trend is combined with the calibrated running parameter and the current oscillation amplitude to generate a prediction correction factor. This means that the predicted running parameter trend is not directly used for correction, but is comprehensively considered with the calibrated running parameter at the current time after noise and delay processing and the real-time acquired current oscillation amplitude. For example, the three types of information can be fused by weighted average, fuzzy logic or neural network to generate a prediction correction factor that can reflect the future dynamic change and the current actual state. The prediction correction factor aims to quantify the deviation of the dynamic influence degree caused by the parameter lag.

[0086] In actual application, according to the prediction correction factor, the dynamic influence degree of each running parameter on the nonlinear combination coefficient is fed forward and compensated. This means that when calculating the dynamic influence degree of the nonlinear combination coefficient, the prediction correction factor is introduced as a kind of feedforward signal instead of relying only on the current calibrated running parameter. For example, a term related to the prediction correction factor can be added to the calculation formula of the dynamic influence degree, or the preliminary calculated dynamic influence degree can be adjusted according to the prediction correction factor through lookup table, mapping function and the like. The purpose is to correct the actual dynamic influence degree in advance, so as to effectively compensate the dynamic deviation caused by the lag of each running parameter.

[0087] The scheme of the present application can predict the potential change direction and amplitude of the machine tool running parameter in advance by introducing historical running data to construct a trend model and make prediction. Due to this forward-looking prediction ability, the system can generate a predictive correction factor with foresight before the actual parameter change occurs, combined with the current calibrated running parameter and the current oscillation amplitude. The prediction correction factor is used as a kind of feedforward signal to compensate and correct the dynamic influence degree of each running parameter on the nonlinear combination coefficient. Through this feedforward compensation mechanism, the system can effectively overcome the dynamic deviation caused by the running parameter lag in the traditional method, ensure that the adjustment of the nonlinear combination coefficient has considered the future trend before the actual parameter change, and thus improve the real-time and accuracy of the dynamic influence degree calculation.

[0088] In some preferred embodiments, the following is described by a specific example: Assuming that the numerical control lathe is running for a long time, the ambient temperature and the spindle speed will gradually increase, and the changes of these parameters will affect the rigidity of the mechanical system. In the traditional scheme, even if these parameters are monitored and calibrated in real time, due to the inherent delay of sensor response, data transmission and processing, etc., when the temperature or speed actually changes, the dynamic influence degree calculated by the system will always lag one step. In order to solve this problem, the application is implemented as follows: first, the system will continuously record the historical data of the machine tool running parameters such as ambient temperature, spindle speed, etc. in the past few hours or even days. Using these historical data, a trend model based on time series analysis can be constructed. For example, the exponential smoothing method or Kalman filter can be used to predict the future trend of ambient temperature and spindle speed, so as to obtain the running parameter trend in the next 10 seconds.

[0089] Secondly, when the reverse gap compensation motion is performed, the system will obtain the current calibrated ambient temperature, spindle speed and current oscillation amplitude in real time. Then, these real-time data are combined with the predicted running parameter trend. For example, a weighted function can be designed to assign a certain weight (e.g. 0.3) to the predicted trend, a higher weight (e.g. 0.5) to the calibrated running parameter, and the remaining weight (e.g. 0.2) to the current oscillation amplitude, and a predicted correction factor is calculated by combining these weights. The predicted correction factor will reflect the potential deviation of the dynamic influence degree caused by the parameter lag under the current working condition.

[0090] Finally, when calculating the dynamic influence degree of each running parameter on the non-linear combination coefficient, the system will introduce this predicted correction factor as a feedforward quantity. For example, if the predicted correction factor indicates that the future temperature will rise, resulting in a decrease in mechanical rigidity, then when calculating the dynamic influence degree, even if the current calibrated temperature has not fully reflected the state after the rise, the system will adjust the non-linear combination coefficient in advance, making it more inclined to reflect the state of lower rigidity. Through this feedforward compensation correction, the system can adjust the non-linear combination coefficient in advance before the actual temperature or speed change is fully reflected, thereby effectively compensating for the dynamic deviation caused by the lag of each running parameter, ensuring the accuracy of gap elimination judgment and the stability of control.

[0091] In the field of modern precision manufacturing, the axial positioning accuracy of numerical control lathe is a key factor to determine the product quality. When the traditional existing numerical control lathe reverses in the axial motion direction for gap compensation, the misjudgment problem caused by the intermittent fluctuation of the grating ruler signal makes the double closed-loop control system unstable near the target position, and the continuous "creeping" phenomenon occurs, which seriously affects the machining precision.

[0092] Reference Figure 2The application further provides a numerical control lathe axial positioning control system, comprising: a driving module 1, configured to drive the servo motor to perform reverse gap compensation movement at a preset small speed when the axial movement direction is reversed; an acquisition module 2, configured to acquire the position signal of the workbench and the load current signal of the servo motor at a synchronous sampling period during the reverse gap compensation movement; a judgment module 3, configured to perform compound judgment based on the position signal and the load current signal: whether the variation of the position signal along the command direction reaches a preset position threshold value within a preset duration window, and whether the increase of the load current signal relative to the reference current value before the reverse gap compensation movement reaches a preset current threshold value; a termination module 4, configured to determine that the mechanical gap has been eliminated when all the compound judgment items are satisfied simultaneously, terminate the reverse gap compensation movement, and switch to a normal double-closed-loop axial positioning control mode; a switching module 5, configured to maintain the reverse gap compensation movement when any one of the compound judgment items is not satisfied.

[0093] The numerical control lathe axial positioning control system of the application solves the misjudgment problem caused by the fluctuation of the grating ruler signal in the gap compensation process by introducing the cooperative work of the driving module 1, the acquisition module 2, the judgment module 3, the termination module 4 and the switching module 5, especially the compound judgment mechanism of the position signal and the load current signal of the servo motor in the judgment module 3. Compared with the traditional method which only depends on the position signal, the system not only considers the position change of the workbench, but also introduces the load current signal reflecting the stress state of the mechanical system when judging the elimination of the mechanical gap. When the mechanical gap is truly eliminated and the rigid contact of the ball screw transmission chain occurs, the resistance that the servo motor needs to overcome will significantly increase, thereby causing the significant increase of the load current. By monitoring the variation of the position signal and the increase of the load current signal through the judgment module 3, and requiring both to satisfy the preset threshold value, the system can effectively distinguish the false displacement caused by the fluctuation of the grating ruler signal and the actual mechanical contact. Therefore, the system significantly improves the accuracy and robustness of the gap elimination judgment, ensures the precision and stability of the axial positioning of the numerical control lathe in the complex industrial environment, effectively eliminates the "creep" phenomenon of the workbench near the target position, and thus guarantees the quality of the precision machining task.

[0094] The above is only an embodiment of the application and is not used to limit the protection scope of the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A method for axial positioning control of a CNC lathe, characterized in that, include: When the axial movement direction is reversed, the servo motor is driven to perform backlash compensation movement at a preset low speed; During the backlash compensation motion, the position signal of the worktable and the load current signal of the servo motor are acquired with a synchronous sampling period. Based on the position signal and the load current signal, a combined judgment is made: within a preset duration window, it is determined whether the change in the position signal along the command direction reaches a preset position threshold, and whether the increase in the load current signal relative to the reference current value before the backlash compensation movement reaches a preset current threshold. When all the conditions of the composite judgment are met at the same time, it is determined that the mechanical backlash has been eliminated, the reverse backlash compensation movement is terminated, and the normal dual closed-loop axial positioning control mode is switched. If any of the composite judgments is not satisfied, the reverse backlash compensation motion is maintained.

2. The axial positioning control method for CNC lathes according to claim 1, characterized in that, The composite judgment also includes: A micro-amplitude high-frequency oscillation command is superimposed on the servo motor, and the load current signal is acquired synchronously. The load current signal is subjected to high-pass filtering to obtain the filtered load current signal; Spectral analysis is performed on the filtered load current signal to extract the current oscillation amplitude corresponding to the frequency of the micro-amplitude high-frequency oscillation command; Determine whether the current oscillation amplitude continuously exceeds the preset rigid contact oscillation amplitude threshold.

3. The axial positioning control method for CNC lathes according to claim 2, characterized in that, The step of determining whether the current oscillation amplitude continuously exceeds a preset rigid contact oscillation amplitude threshold includes: Before performing the backlash compensation motion, a micro-amplitude high-frequency oscillation command is superimposed on the servo motor, and the load current signal of the servo motor is acquired simultaneously. The load current signal is subjected to high-pass filtering to obtain a filtered load current signal, and the filtered load current signal is subjected to spectrum analysis to obtain the current oscillation amplitude corresponding to the frequency of the micro-amplitude high-frequency oscillation command. The current oscillation amplitude is calibrated according to the machine tool operating parameters, and the rigid contact oscillation amplitude threshold is adjusted to the threshold under the current working condition for the composite judgment.

4. The axial positioning control method for CNC lathes according to claim 3, characterized in that, The step of calibrating the current oscillation amplitude based on machine tool operating parameters and adjusting the rigid contact oscillation amplitude threshold accordingly to the threshold under the current operating conditions includes: The machine tool operating parameters are monitored, including at least one of ambient temperature, cumulative running time, cumulative axial travel, spindle speed, and feed rate; Based on the machine tool operating parameters and the preset parameter influence weight set, a comprehensive rigidity correction factor is calculated; The threshold value of the rigid contact oscillation is dynamically adjusted based on the current oscillation amplitude and the comprehensive rigidity correction factor.

5. The axial positioning control method for a CNC lathe according to claim 1, characterized in that, The method further includes: Before performing the backlash compensation motion, the actual backlash value and friction torque parameter of the ball screw are measured by micro-amplitude detection motion, and a backlash crossing optimization trajectory is generated based on the actual backlash value and friction torque parameter. The backlash compensation motion is completed along the backlash crossing optimization trajectory, and after the backlash compensation motion is completed, the system smoothly switches to the normal dual closed-loop axial positioning control mode.

6. The axial positioning control method for a CNC lathe according to claim 4, characterized in that, The calculation of the comprehensive rigidity correction factor based on the machine tool operating parameters and a preset set of parameter influence weights includes: Before performing the backlash compensation motion, multiple independent rigidity correction components are calculated based on the machine tool operating parameters and the parameter influence weight set; The nonlinear combination coefficients are dynamically adjusted based on the machine tool operating parameters. The adjusted nonlinear combination coefficients are used to perform a nonlinear combination on multiple independent rigid correction components to obtain the comprehensive rigid correction factor. The nonlinear combination is an adaptive nonlinear combination.

7. The axial positioning control method for a CNC lathe according to claim 6, characterized in that, The dynamic adjustment of the nonlinear combination coefficients based on the machine tool operating parameters includes: Based on the machine tool operating parameters, calculate the dynamic influence of each operating parameter on the nonlinear combination coefficients; Based on the dynamic influence level, the nonlinear combination coefficients between the multiple rigid correction components are adjusted in real time to reflect the true coupling relationship between the rigid correction components under the current working condition.

8. The axial positioning control method for a CNC lathe according to claim 7, characterized in that, The step of calculating the dynamic influence of each operating parameter on the nonlinear combination coefficients based on the machine tool operating parameters includes: To address the measurement noise of the machine tool operating parameters, the monitored operating parameters are sampled at multiple points and processed using a moving average to obtain the processed operating parameters. To address the measurement delay of each operating parameter, the processed operating parameters are timestamped and synchronized to obtain calibrated operating parameters. Based on the calibrated operating parameters, the dynamic influence of each operating parameter on the nonlinear combination coefficients is calculated.

9. The axial positioning control method for a CNC lathe according to claim 8, characterized in that, The calculation of the dynamic influence of each operating parameter on the nonlinear combination coefficients includes: A trend model is constructed based on historical operating data to predict the changing trends of the machine tool's operating parameters, thereby obtaining the operating parameter trends; The trend of the operating parameters is combined with the calibrated operating parameters and the current oscillation amplitude to generate a prediction correction factor; Based on the prediction correction factor, the dynamic influence of each operating parameter on the nonlinear combination coefficient is corrected by feedforward compensation to compensate for the dynamic deviation caused by the lag of each operating parameter.

10. An axial positioning control system for a CNC lathe, characterized in that, include: The drive module is used to drive the servo motor to perform backlash compensation motion at a preset low speed when the axial movement direction is reversed. The acquisition module is used to acquire the position signal of the worktable and the load current signal of the servo motor at a synchronous sampling period during the backlash compensation motion. The judgment module is used to make a composite judgment based on the position signal and the load current signal: within a preset duration window, it judges whether the change of the position signal along the command direction reaches a preset position threshold, and judges whether the increase of the load current signal relative to the reference current value before the backlash compensation movement reaches a preset current threshold. The termination module is used to determine that the mechanical backlash has been eliminated when all the composite judgment items are satisfied at the same time, terminate the backlash compensation movement, and switch to the normal dual closed-loop axial positioning control mode. The switching module is used to maintain the reverse backlash compensation movement when any one of the composite judgments is not satisfied.

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