A five-axis linkage machining center complex workpiece digital control method and system

Abstract

This application relates to the field of CNC machining technology and discloses a digital control method and system for complex workpieces in a five-axis linkage machining center. The method includes acquiring feedback data from multiple drive units corresponding to the same motion target; correlating the feedback data of multiple drive units to a unified reference datum in the time dimension; determining the motion command deviation of each drive unit based on the correlated feedback data, and performing a consistency analysis on the motion command deviations of multiple drive units; if the consistency analysis shows that the motion command deviation is a mechanical deviation, calculating a correction amount based on the motion command deviation, and adding the correction amount to the motion control command of the next cycle and sending it to multiple drive units; if the consistency analysis shows that the motion command deviation is a time misalignment deviation, maintaining the current output state of the motion control command. By accurately distinguishing the source of deviation, the synchronous control accuracy of complex curved surface machining and the final workpiece surface quality are improved.

Description

Technical Field

[0001] This application relates to the field of CNC machining technology, and more specifically, to a digital control method and system for complex workpieces in a five-axis linkage machining center. Background Technology

[0002] Achieving high-precision machining of complex curved surfaces in ultra-large five-axis machining centers, especially those employing multi-drive units such as three-gantry cranes to collaboratively drive a single motion axis, presents significant challenges. Conventional digital control systems collect feedback data such as position and speed from each drive unit and attempt to align this data in time to calculate and compensate for synchronization deviations. However, due to the large size of the equipment and the complexity of the electrical wiring, feedback data from different drive units must traverse communication links of varying lengths and types to reach the controller. The different transmission delays, network load fluctuations, and processing times of intermediate modules within these links result in unpredictable and dynamically changing differences in the arrival times of feedback data from various sources.

[0003] The core problem with existing technologies lies in the difficulty of effectively distinguishing between two completely different types of deviations: one is the genuine mechanical synchronization deviation caused by inconsistent physical movements of various drive units; the other is the pseudo-deviation caused by inconsistent arrival times of data during transmission, i.e., time misalignment deviation. When the control system misjudges this time misalignment as mechanical asynchrony, it generates and issues inappropriate correction commands. This erroneous correction not only fails to improve machining accuracy but also causes frequent fine-tuning and vibration of the drive system, resulting in fine vibration marks and tool steps left on the workpiece surface by the tool, severely reducing the smoothness of complex curved surfaces and the overall machining quality.

[0004] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a digital control method and system for complex workpieces in a five-axis linkage machining center, which can solve the technical problem in existing technologies where the inability to distinguish between mechanical deviations and time misalignment deviations leads to incorrect corrections that affect machining quality.

[0006] In a first aspect, this application provides a digital control method for complex workpieces in a five-axis linkage machining center, comprising: Acquire feedback data from multiple drive units corresponding to the same moving target; Correlate the feedback data from multiple drive units to a unified reference benchmark in the time dimension; Based on the correlated feedback data, the motion command deviation of each drive unit is determined, and a consistency analysis is performed on the motion command deviation of multiple drive units. If the consistency analysis shows that the motion command deviation is a mechanical deviation, the correction amount is calculated based on the motion command deviation, and the correction amount is added to the motion control command of the next cycle and sent to multiple drive units. If the consistency analysis shows that the motion command deviation is a time misalignment deviation, the current output state of the motion control command is maintained.

[0007] This technical solution enables consistency analysis of motion command deviations from multiple drive units, accurately distinguishing whether the deviation originates from actual mechanical asynchrony or time misalignment caused by data transmission. This avoids improper correction due to incorrect judgment, thereby improving the synchronous control accuracy and final workpiece surface quality in complex surface machining.

[0008] Furthermore, the step of acquiring feedback data from multiple drive units corresponding to the same moving target includes: Real-time monitoring of the feedback link status of multiple drive units; When an interruption is detected in the feedback link status of the drive unit, real-time feedback data of the drive unit whose feedback link status is not interrupted is obtained. Obtain a physical coupling constraint model of the same moving target. The physical coupling constraint model represents the kinematic relationship between multiple driving units. By combining the real-time feedback data of the drive unit whose feedback link status is not interrupted with the physical coupling constraint model, the virtual feedback data of the drive unit whose feedback link status is interrupted during the interruption period is reconstructed as its feedback data.

[0009] This technical solution utilizes a physical coupling constraint model to reconstruct the virtual feedback data of a certain drive unit when its feedback link is interrupted, ensuring the continuity and integrity of the data flow and enhancing the robustness and reliability of the control system in harsh communication environments.

[0010] Furthermore, the steps of correlating the feedback data from multiple drive units to a unified reference benchmark in the time dimension include: Obtain the monotonically increasing sequence identifier attached to the motion command issued by the machining center, and record the arrival time of the feedback data; Calculate the communication link delay corresponding to each driving unit based on the monotonically increasing sequence identifier and arrival time; The feedback data is compensated by utilizing the communication link delay corresponding to each drive unit, so as to align the feedback data of each drive unit to the reference base and use it as the associated feedback data.

[0011] This technical solution utilizes the sequence identifier and data arrival timestamp attached to the instruction to accurately calculate and compensate for the communication delay of different links, achieving high-precision alignment of feedback data from different drive units on the time base, laying the foundation for subsequent accurate deviation analysis.

[0012] Furthermore, the steps for compensating the feedback data using the communication link delay corresponding to each drive unit include: Establish a delay statistics window for each drive unit, and calculate the fluctuation characteristic value of the communication link delay within the delay statistics window; When the fluctuation characteristic value exceeds the first preset threshold, the evolution trend of the communication link delay corresponding to the driving unit in the time series is extracted. Based on the evolution trend, predictive phase correction is performed on the feedback data of the corresponding driving unit to eliminate the impact of random jitter of communication link delay on the alignment accuracy of the reference reference.

[0013] By statistically analyzing and predicting the trends of communication delay fluctuations, proactive predictive phase correction can be performed, effectively suppressing the interference of random factors such as network jitter on time alignment accuracy and further improving the stability of the synchronization reference.

[0014] Furthermore, based on the correlated feedback data, the steps of determining the motion command deviation of each drive unit and performing a consistency analysis on the motion command deviations of multiple drive units include: Based on the correlated feedback data, the positional deviation between the actual position and the command position of each drive unit is calculated. Compare the direction and magnitude differences in the positional deviations of multiple drive units; If the position deviations of all drive units are in the same direction and their magnitudes are all less than the second preset threshold, then the result of the consistency analysis is: the motion command deviation is a mechanical deviation. If the position deviation directions of at least two drive units are not the same, or the difference in their magnitudes exceeds the second preset threshold, and at least one drive unit exhibits a preset first fluctuation characteristic or a preset second fluctuation characteristic, then the result of the consistency analysis is: the motion command deviation is a time misalignment deviation.

[0015] By analyzing the consistency of the direction and magnitude of the positional deviations of each drive unit, and combining this with communication fluctuation characteristics, the fundamental nature of the deviations can be reliably determined, thus achieving effective identification of mechanical deviations and time misalignment deviations.

[0016] Furthermore, the preset first fluctuation characteristic includes: the difference between the maximum and minimum values ​​of the arrival time of the feedback data of the drive unit within a preset time window exceeds a third preset threshold.

[0017] This technical solution uses the maximum and minimum difference in data arrival time as a specific quantitative indicator of communication fluctuations, making the judgment of time misalignment deviations more specific and easier to implement, and improving the accuracy of the judgment.

[0018] Furthermore, the preset second fluctuation characteristic includes: the driving unit is located on the communication link through the intermediate conversion module, and the change in the arrival time of its feedback data between two consecutive times exceeds the fourth preset threshold.

[0019] This technical solution pays special attention to the communication link through the intermediate conversion module. By monitoring the instantaneous change in the arrival time of the feedback data, it can more sensitively capture the delay jitter introduced by the specific network topology and enhance the ability to identify time misalignment deviations in complex network environments.

[0020] Furthermore, when the consistency analysis result is that the motion command deviation is a time misalignment deviation, the method also includes: Obtain the current values ​​of multiple drive units; When the difference in current values ​​between at least two drive units exceeds a first preset ratio, and the direction of the difference in current values ​​is consistent with the expected force direction of the structure of the same moving target, the result of the consistency analysis is corrected to: the motion command deviation is the transient torsional deviation of the structure. Otherwise, the result of the consistency analysis remains: the motion command deviation is a time misalignment deviation.

[0021] By introducing a secondary diagnosis of the driving current after the initial judgment of time misalignment deviation, it is possible to further distinguish the real physical deviation caused by transient torsion of the structure, avoid misjudging the structural stress problem as a simple communication problem, and make the deviation diagnosis more in-depth and the classification more refined.

[0022] Furthermore, when the results of the consistency analysis are corrected to show that the motion command deviation is a transient torsional deviation of the structure, the method also includes the following steps: The asymmetric speed compensation amount is generated based on the difference in current values, and then superimposed on the asymmetric speed compensation amount in the motion control command of the next cycle and sent to multiple drive units to release torsional stress. When the result of the consistency analysis remains that the motion command deviation is a time misalignment deviation, the method also includes the following steps: Maintain the current output state of the motion control command, and perform weighted smoothing on the subsequently acquired feedback data to eliminate signal glitches in the feedback data.

[0023] This technical solution employs differentiated strategies to address different types of deviations diagnosed: proactive asymmetric compensation is used to release stress in cases of structural torsion, while smoothing filtering is used to suppress data noise in cases of time misalignment. This enables precise measures to be taken for different root causes of problems, significantly improving the adaptability and control effectiveness of the control system.

[0024] Secondly, this application also discloses a digital control system for complex workpieces in a five-axis linkage machining center, used to execute the digital control method for complex workpieces in a five-axis linkage machining center as described in any of the preceding claims, the system comprising: The data acquisition module is used to acquire feedback data from multiple drive units corresponding to the same moving target; The time correlation module is used to correlate the feedback data of multiple drive units to a unified reference benchmark in the time dimension; The consistency analysis module is used to determine the motion command deviation of each drive unit based on the correlated feedback data, and to perform consistency analysis on the motion command deviation of multiple drive units. The motion control module is used to calculate the correction amount based on the motion command deviation if the consistency analysis result shows that the motion command deviation is a mechanical deviation, and then add the correction amount to the motion control command of the next cycle and send it to multiple drive units. If the consistency analysis result shows that the motion command deviation is a time misalignment deviation, the current output state of the motion control command is maintained.

[0025] The core advantage of this application lies in its fundamental solution to the problem of existing technologies being unable to distinguish the source of deviations by introducing a consistency analysis step for the motion command deviations of multiple drive units. In existing technologies, control systems treat all feedback deviations as mechanical errors and compensate for them. When the deviation is actually caused by data transmission delays, this compensation is erroneous and introduces control disturbances. This application, however, first diagnoses the nature of the deviation: if the analysis results show that the direction and magnitude of the deviations of each drive unit are highly consistent, it is determined to be a genuine mechanical deviation, and correction is performed; conversely, if the deviation is inconsistent in direction or magnitude and accompanied by communication fluctuations, it is determined to be a time misalignment deviation. In this case, the system will maintain the current control command unchanged, avoiding ineffective or even harmful adjustment actions. Through this strategy of diagnosis first and then implementation, this application can accurately identify and ignore pseudo-deviations caused by communication problems, responding only to genuine mechanical asynchrony. This effectively avoids self-excited oscillations caused by misjudgment in the control system, significantly improving the stability and accuracy of multi-axis synchronous control, ultimately resulting in a substantial improvement in the quality of complex curved surfaces of workpieces. Attached Figure Description

[0026] Figure 1This is a flowchart illustrating a digital control method for complex workpieces in a five-axis linkage machining center, as provided in an embodiment of this application.

[0027] Figure 2 This is a schematic diagram of the structure of a complex workpiece digital control system for a five-axis linkage machining center, provided as an embodiment of this application.

[0028] Labeling Explanation: 210, Data Acquisition Module; 220, Time Correlation Module; 230, Consistency Analysis Module; 240, Motion Control Module. Detailed Implementation

[0029] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0030] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0031] In a typical application scenario, an ultra-large three-gantry five-axis linkage machining center is performing high-precision curved surface milling on an aluminum alloy sheet used to manufacture the wing skin of a large passenger aircraft. The two high-power servo motor drive units, located at opposite ends of the tens-of-meters-long crossbeam along the Y-axis, are called the Y1 drive unit and the Y2 drive unit. These two drive units are physically connected by a rigid crossbeam structure, and theoretically, their motion trajectories, speeds, and accelerations should remain strictly consistent at all times, collectively forming a single motion target. However, in actual machining, the CNC system often detects slight differences in the positions reported by the Y1 and Y2 drive units. Existing control systems cannot effectively determine the root cause of this difference: is it due to uneven cutting forces causing micron-level elastic torsion in the crossbeam, i.e., asynchronous actual mechanical movement; or is it simply because the feedback signal from the Y2 drive unit arrives at the controller a fraction of a millisecond later than the Y1 signal after passing through a longer cable and additional network switches, causing a time misalignment at the data level? This confusion can cause the controller to make inappropriate compensations based on incorrect timing information, such as ordering Y1 to decelerate to wait for Y2, when in fact the physical movements of Y1 and Y2 are synchronized. This erroneous intervention can trigger minute vibrations in the system, eventually leaving indelible machining marks on the smooth, mirror-like surface of the wing skin, leading to the scrapping of expensive components.

[0032] Regarding this, firstly, see... Figure 1 This application provides a digital control method for complex workpieces in a five-axis linkage machining center. Its core lies in its ability to intelligently identify the true source of deviations, thereby making correct control decisions. The method specifically includes the following steps: S1. Obtain feedback data from multiple drive units corresponding to the same moving target; S2. Correlate the feedback data from multiple drive units to a unified reference benchmark in the time dimension; S3. Based on the feedback data after association, determine the motion command deviation of each drive unit, and perform consistency analysis on the motion command deviation of multiple drive units. S4. If the consistency analysis shows that the motion command deviation is a mechanical deviation, calculate the correction amount based on the motion command deviation and add the correction amount to the motion control command of the next cycle and send it to multiple drive units. If the consistency analysis shows that the motion command deviation is a time misalignment deviation, maintain the current output state of the motion control command.

[0033] Motion command deviation refers to the difference between the actual state (e.g., position, velocity) of a drive unit at a given moment and the target state it is commanded to achieve. In the context of this application, the focus is primarily on position deviation. Mechanical deviation refers to the actual, physical asynchrony in motion between multiple cooperating drive units caused by physical factors such as cutting load, changes in friction, structural elastic deformation, and differences in driving torque. This deviation is an objectively existing physical phenomenon.

[0034] Timing misalignment refers to a situation where multiple drive units move synchronously in physical terms, but due to varying delays in the transmission of their feedback data to the controller, the data received by the controller at the same moment actually corresponds to different states in the physical world. This results in a pseudo-deviation calculated at the data level that appears to be asynchronous. This deviation is a product of the information transmission process, not a reflection of the true state of the physical world. Consistency analysis, a core diagnostic method proposed in this application, aims to determine the overall nature of the deviations by analyzing the inherent correlation characteristics of the motion command deviations of multiple drive units, such as the similarity of their direction and magnitude. Specifically, it determines whether the deviation is more likely to be attributed to mechanical misalignment or timing misalignment.

[0035] The overall process of this method will be explained in detail below.

[0036] The first step is to acquire feedback data. In the aforementioned wing skin machining scenario, the CNC system sends motion commands to the two drive units Y1 and Y2 at an extremely high frequency, such as once every millisecond, while continuously receiving status information fed back from each of them. This feedback data is typically generated by high-precision encoders mounted on the motor shaft or the final moving parts, and includes real-time position readings accurate to micrometers or smaller, as well as speed values, motor current values, etc., calculated internally by the drivers. The data acquisition process is accomplished through industrial fieldbus networks, such as EtherCAT or ProfinetIRT. The controller, acting as the master station, polls and reads these feedback data packets from designated memory addresses of each drive unit.

[0037] The second step is to correlate the feedback data to a unified reference point in the time dimension. This is a crucial preprocessing step. Since the feedback signals from the Y1 and Y2 drive units arrive at the controller at different times, directly comparing two data points received within the same controller clock cycle is meaningless. Therefore, these data points with different time delays must be converted to a common, virtual time coordinate system. A basic implementation involves maintaining a high-precision, monotonically increasing master clock internally. When a feedback data packet from any drive unit is received, an arrival timestamp is immediately added to the packet. After calculating the signal transmission delay of each drive unit, the system can correct the timestamp of each data point, thereby projecting all data points onto this unified reference point. After this step, the system can obtain the aligned position values ​​of the Y1 and Y2 drive units at the same logical point in time.

[0038] The third step is to perform consistency analysis based on the correlated feedback data. This is the core of the decision-making process in this method. The system first calculates the motion command deviation for each drive unit. For example, at a certain aligned time point t, the command position is P_cmd(t), the aligned actual position of Y1 is P_y1_aligned(t), and the aligned actual position of Y2 is P_y2_aligned(t).

[0039] Therefore, the deviation of Y1 is Dev1=P_y1_aligned(t)-P_cmd(t), and the deviation of Y2 is Dev2=P_y2_aligned(t)-P_cmd(t).

[0040] Subsequently, the system performs a consistency analysis on the deviations between Dev1 and Dev2. The logic behind this analysis is that if the deviations are caused by a common mechanical reason (such as an increase in overall cutting resistance), then the two drive units should behave similarly; that is, their deviation directions are likely to be the same, and their magnitudes will not differ significantly. Conversely, if the deviations are caused by timing misalignments in data transmission, then their behavior is often chaotic; one might show a positive deviation, the other a negative deviation, or the two might differ significantly in magnitude. Based on this, the system determines the nature of this set of deviations.

[0041] The fourth step is to implement differentiated control strategies based on the analysis results. If the consistency analysis determines that the current deviation is a mechanical deviation, for example, if the system finds that Y1 and Y2 are both lagging behind the commanded positions by approximately 5 micrometers, this clearly points to synchronization lag caused by the cutting load. In this case, the control system will consider this a real physical problem that needs correction. It will calculate an appropriate correction amount, such as adding a small speed increment to the motion commands of Y1 and Y2 in the next control cycle, to actively compensate for this lag and ensure the accuracy of the tool path.

[0042] Conversely, if the consistency analysis determines that the current deviation is a timing misalignment—for example, the system finds that Y1 is lagging by 5 micrometers while Y2 is leading by 4 micrometers—this opposite deviation is highly inconsistent with physical laws and is likely an illusion caused by Y2's feedback data arriving too early or Y1's feedback data arriving too late. In this case, the control system will determine that the beam motion in the physical world is most likely normal, and the observed deviation is unreliable. Therefore, the system will choose to remain inactive, that is, maintain the current motion control command output state unchanged, and not perform any additional correction operations.

[0043] In this way, this application effectively filters out noise interference introduced by communication delay and jitter, avoiding the control system from being misled into making unnecessary or even harmful adjustments, thereby ensuring the smoothness and accuracy of multi-axis synchronous motion in complex electromagnetic and network environments.

[0044] Furthermore, the step of acquiring feedback data from multiple drive units corresponding to the same moving target includes: Real-time monitoring of the feedback link status of multiple drive units; When an interruption is detected in the feedback link status of the drive unit, real-time feedback data of the drive unit whose feedback link status is not interrupted is obtained. Obtain a physical coupling constraint model of the same moving target. The physical coupling constraint model represents the kinematic relationship between multiple driving units. By combining the real-time feedback data of the drive unit whose feedback link status is not interrupted with the physical coupling constraint model, the virtual feedback data of the drive unit whose feedback link status is interrupted during the interruption period is reconstructed as its feedback data.

[0045] The physical coupling constraint model here is a mathematical description of the inherent kinematic relationship between multiple driving units that are cooperating in motion. For the Y1 and Y2 driving units that drive the same rigid beam, this model can be very simple, i.e., their ideal position, velocity, and acceleration should be equal at any time. This model can be pre-stored in the parameter library of the CNC system.

[0046] When the system detects an interruption in the feedback link of Y2 through a bus diagnostic mechanism (e.g., failure to receive valid data frames from the Y2 drive unit for several consecutive cycles), it does not immediately shut down and alarm, but instead initiates a data reconstruction procedure. During this period, the system continues to acquire real-time feedback data from the Y1 drive unit. Then, it uses a physical coupling constraint model to estimate the current position of Y2 based on the real-time position of Y1. In the most direct implementation, the system can directly assign the real-time position value of Y1 to Y2 as virtual feedback data for Y2 during the interruption. That is, P_y2_virtual(t) = P_y1_real(t). This virtual data is then fed into the subsequent control flow. The rationale for this approach is that, due to the rigid constraint of the beam, even without feedback, the actual position of Y2 will be highly consistent with Y1 for a short period of time. In this way, the control system can smoothly overcome short communication interruption periods without interrupting processing, greatly enhancing the robustness of the system and production continuity.

[0047] Furthermore, the steps of correlating the feedback data from multiple drive units to a unified reference benchmark in the time dimension include: Obtain the monotonically increasing sequence identifier attached to the motion command issued by the machining center, and record the arrival time of the feedback data; Calculate the communication link delay corresponding to each driving unit based on the monotonically increasing sequence identifier and arrival time; The feedback data is compensated by utilizing the communication link delay corresponding to each drive unit, so as to align the feedback data of each drive unit to the reference base and use it as the associated feedback data.

[0048] In practice, when the CNC controller broadcasts motion commands to all drive units in each control cycle (e.g., cycle T = 1 millisecond), it appends an incrementing integer, a monotonically increasing sequence identifier, to the command data packet, which can be called a frame counter. For example, in the k-th cycle, the sent command packet contains the sequence identifier k.

[0049] Meanwhile, the controller has an internal high-resolution hardware clock that timestamps the arrival of each feedback data packet returned from the drive unit. The drive unit is designed to immediately execute and prepare feedback data upon receiving an instruction with a sequence identifier k, and this feedback data packet will also contain the sequence identifier k.

[0050] In this way, when the controller receives a feedback packet, it obtains a triplet of information: (Driver Unit ID, Sequence Identifier k, Arrival Time T_arrival). The controller can maintain a table recording the time T_send(k) when the instruction for each sequence identifier k is issued. Therefore, for a given driver unit (e.g., Y1), its round-trip time (RTT_y1(k)) in response to the feedback data for sequence identifier k is RTT_y1(k) = T_arrival_y1(k) - T_send(k). The one-way delay of the communication link can be approximated as half the round-trip time, or it can be directly read in some synchronous clock buses (such as the distributed clock of EtherCAT).

[0051] By statistically analyzing the delay data over multiple consecutive periods, such as by calculating the moving average, the system can obtain a relatively stable average communication link delay for each drive unit (Y1 and Y2), denoted as AvgDelay_y1 and AvgDelay_y2.

[0052] When performing data compensation, the system uses the drive unit with the lowest latency as the benchmark, or sets a fixed virtual reference time. Assuming Y1 has the lowest latency, it becomes the benchmark. Then, for any feedback data received from Y2, its original timestamp T_arrival_y2 needs to be corrected. The corrected timestamp T_aligned_y2 = T_arrival_y2 - (AvgDelay_y2 - AvgDelay_y1). This compensation operation is equivalent to shifting the data of Y2 to the left on the time axis, logically aligning it with the data of Y1, thus achieving association with a unified reference benchmark.

[0053] Furthermore, the steps for compensating the feedback data using the communication link delay corresponding to each drive unit include: Establish a delay statistics window for each drive unit, and calculate the fluctuation characteristic value of the communication link delay within the delay statistics window; When the fluctuation characteristic value exceeds the first preset threshold, the evolution trend of the communication link delay corresponding to the driving unit in the time series is extracted. Based on the evolution trend, predictive phase correction is performed on the feedback data of the corresponding driving unit to eliminate the impact of random jitter of communication link delay on the alignment accuracy of the reference reference.

[0054] In one embodiment, the system maintains a first-in-first-out (FIFO) queue for each drive unit (such as Y1 and Y2) to store the communication link delay values ​​calculated in the most recent N cycles (e.g., N=100). This queue is called the delay statistics window. In each control cycle, the system calculates the standard deviation of the delay data within this window as a feature value describing the degree of its fluctuation.

[0055] The system will preset a first threshold, for example, 0.05 milliseconds. If the calculated standard deviation of the delay of the Y2 driver unit is less than this threshold, it indicates that its communication link is quite stable, and the moving average can continue to be used for compensation. However, if the standard deviation exceeds 0.05 milliseconds, it indicates that the Y2 communication link is experiencing significant jitter.

[0056] At this point, the system will launch a trend analysis program. It will analyze the 100 latency data points in the window, for example, by fitting a straight line using the least squares method to extract the short-term trend of latency changes, such as the latency increasing by 0.01 milliseconds every 10 periods.

[0057] When performing phase correction, the system no longer simply subtracts an average delay, but instead predicts the most likely delay for the next data packet based on this evolution trend. For example, it uses the fitted linear equation to extrapolate the predicted delay value for the next cycle. Then, it uses this more forward-looking predicted delay value to timestamp the feedback data of Y2. This predictive phase correction can proactively and dynamically adapt to changes in communication latency, acting like a shock absorber in the data alignment process, thus maintaining a highly stable time reference even in the presence of network jitter.

[0058] Furthermore, based on the correlated feedback data, the steps of determining the motion command deviation of each drive unit and performing consistency analysis on the motion command deviations of multiple drive units can specifically include: Based on the correlated feedback data, the positional deviation between the actual position and the command position of each drive unit is calculated. Compare the direction and magnitude differences in the positional deviations of multiple drive units; If the position deviations of all drive units are in the same direction and their magnitudes are all less than the second preset threshold, then the result of the consistency analysis is: the motion command deviation is a mechanical deviation. If the position deviation directions of at least two drive units are not the same, or the difference in their magnitudes exceeds the second preset threshold, and at least one drive unit exhibits a preset first fluctuation characteristic or a preset second fluctuation characteristic, then the result of the consistency analysis is: the motion command deviation is a time misalignment deviation.

[0059] The second preset threshold defines the extent to which deviations are tolerable and considered within the normal range of mechanical characteristics. This threshold needs to be set based on the specific structural rigidity, drive performance, and machining accuracy requirements of the machine tool. For example, for the aforementioned wing skin machining, this threshold might be set to 2 micrometers.

[0060] The logic for judging it as mechanical deviation is as follows: when the calculated position deviations of Y1 and Y2, Dev1 and Dev2, have the same direction (e.g., both are negative, indicating that they are both lagging behind the command), and the absolute value of the difference between them, ||Dev1|-|Dev2||, is less than 2 micrometers, the system is highly certain that this is two motors working together to resist an external load, which is a typical mechanical synchronization deviation.

[0061] The logic for identifying time misalignment is more rigorous, comprising two conditions. The first condition is that the deviation itself exhibits inconsistency, meaning the deviation directions are different (one leading and one lagging), or although the directions are the same, the magnitude difference exceeds 2 micrometers. The second condition is a confirmation condition: the system also detects signs of communication instability, also known as fluctuation characteristics. Only when both inconsistency and communication instability occur simultaneously will the system ultimately determine it as a time misalignment. This dual confirmation mechanism effectively prevents seemingly inconsistent real deviations caused by complex mechanical dynamics (such as minor structural vibrations during rapid acceleration and deceleration) from being misjudged as time misalignments. The first and second fluctuation characteristics are specific indicators used to quantify communication instability, providing strong evidence for the judgment of time misalignment.

[0062] Furthermore, the preset first fluctuation characteristic may include: the difference between the maximum and minimum values ​​of the arrival time of the feedback data of the drive unit within a preset time window exceeds a third preset threshold.

[0063] This is a direct indicator for measuring the range of communication latency jitter. The system continuously monitors the arrival timestamp of feedback data from each driver unit. Similarly, a time window can be set, for example, containing the most recent 200 data packets. The system records the earliest arrival timestamp T_min and the latest arrival timestamp T_max among these 200 data packets. Then, the difference, Range = T_max - T_min, is calculated. This difference reflects the maximum fluctuation in the feedback latency of that driver unit in the recent past. If this Range exceeds a preset threshold (for example, a third preset threshold of 0.3 milliseconds), the system considers that the driver unit has exhibited the first fluctuation characteristic.

[0064] Furthermore, the preset second fluctuation characteristic may include: the driving unit is located on the communication link through the intermediate conversion module, and the change in the arrival time of its feedback data between two consecutive times exceeds the fourth preset threshold.

[0065] In large-scale equipment, not all drive units can be directly connected to the controller. For example, the signal from a Y2 drive unit may need to pass through a protocol conversion gateway or an aggregation switch (i.e., an intermediate conversion module) before it can be connected to the main control network. The processing time of such intermediate modules may introduce additional, irregular delays.

[0066] To capture such sudden delays, the system calculates the time interval between two consecutive arrival times of the Y2 feedback data, i.e., ΔT(k) = T_arrival(k) - T_arrival(k-1). Ideally, this interval should be exactly equal to the controller's scan cycle (e.g., 1 millisecond). If a calculated ΔT(k) deviates significantly by 1 millisecond, for example, becoming 1.2 milliseconds, it means that the data packet was delayed by an additional 0.2 milliseconds in the k-th cycle. When this deviation (|ΔT(k) - 1ms|) exceeds a preset fourth threshold (e.g., 0.15 milliseconds), the system considers a second fluctuation characteristic to have occurred. This characteristic is particularly effective for detecting instantaneous delay spikes caused by network congestion, sudden increases in intermediate device load, etc.

[0067] Furthermore, when the result of the consistency analysis is that the motion command deviation is a time misalignment deviation, the method may also include: Obtain the current values ​​of multiple drive units; When the difference in current values ​​between at least two drive units exceeds a first preset ratio, and the direction of the difference in current values ​​is consistent with the expected force direction of the structure of the same moving target, the result of the consistency analysis is corrected to: the motion command deviation is the transient torsional deviation of the structure. Otherwise, the result of the consistency analysis remains: the motion command deviation is a time misalignment deviation.

[0068] The logic behind this step is that when a crossbeam tens of meters long is cutting at high speed and undergoing rapid acceleration and deceleration, due to inertia and cutting forces, the crossbeam itself will produce a slight elastic twist, like a twisted rope. This will cause the Y1 and Y2 drive units located at both ends of the crossbeam to actually produce a momentary positional difference. This difference, reflected in the feedback data, may have characteristics (such as opposite directions) that are very similar to time misalignment.

[0069] To distinguish between the two, after initially determining a time misalignment, the system immediately retrieves the motor current feedback values ​​of the Y1 and Y2 drive units. Motor current directly reflects the magnitude of its output torque. The system calculates the difference between the two motor currents, ΔI = I_y1 - I_y2. If the beam twists, the motor at the end subjected to greater deformation will inevitably output a larger torque to resist it, resulting in a significant change in ΔI.

[0070] The system further compares the direction of change of this current difference with the current motion state. For example, if the machine tool is accelerating along the positive Y-axis and the tool is located closer to Y1, then according to mechanical analysis, the load on the Y1 side will be greater than that on Y2, and the expected ΔI will increase. If the trend of ΔI observed by the system is consistent with this expected force direction, and its change exceeds a certain preset proportion (for example, the current difference changes by more than 5% of the rated current within 0.1 seconds), then the system will correct the diagnosis from time misalignment deviation to structural transient torsional deviation. This is a more accurate diagnosis because it identifies a real physical problem that needs to be actively controlled.

[0071] Furthermore, when the results of the consistency analysis are corrected to show that the motion command deviation is a transient torsional deviation of the structure, the method also includes the following steps: The asymmetric speed compensation amount is generated based on the difference in current values, and then superimposed on the asymmetric speed compensation amount in the motion control command of the next cycle and sent to multiple drive units to release torsional stress. When the result of the consistency analysis remains that the motion command deviation is a time misalignment deviation, the method also includes the following steps: Maintain the current output state of the motion control command, and perform weighted smoothing on the subsequently acquired feedback data to eliminate signal glitches in the feedback data.

[0072] Specifically, if the diagnosis indicates a transient torsional deviation in the structure, the system will consider this a physical problem requiring active intervention. Based on the magnitude of the current difference ΔI, it will generate an asymmetric velocity compensation command. For example, if I_y1 is much larger than I_y2, it indicates that the force on the Y1 side is too large and lagging. In the next cycle's command, the system will add a small positive compensation to the velocity command of Y1, while simultaneously applying a small negative compensation (or keeping it unchanged) to the velocity command of Y2. This push-pull asymmetric control can actively help the beam to twist in the opposite direction, quickly releasing the internally accumulated elastic stress, thereby eliminating physical asynchrony.

[0073] If the final diagnosis remains a time misalignment deviation, it indicates that the observed deviation is indeed a data-level artifact. In this case, the system will, on the one hand, resolutely implement a laissez-faire strategy, maintaining the original motion commands unchanged to avoid erroneous corrections. On the other hand, to reduce the interference of such artifacts at the source, the system will perform weighted smoothing on subsequent feedback data collected from this unstable link (e.g., Y2). For example, exponential smoothing can be used, weighting the currently collected position value with the smoothed value of the previous cycle to obtain a new, smoother position value for subsequent calculations. This is equivalent to adding a low-pass filter to the feedback signal, effectively filtering out high-frequency noise and glitches in the data, making the entire control system more immune to communication jitter.

[0074] Secondly, see Figure 2 This application also provides a digital control system for complex workpieces in a five-axis linkage machining center, the system comprising: The data acquisition module 210 is used to acquire feedback data from multiple drive units corresponding to the same moving target; The time correlation module 220 is used to correlate the feedback data of multiple drive units to a unified reference benchmark in the time dimension; The consistency analysis module 230 is used to determine the motion command deviation of each drive unit based on the correlated feedback data, and to perform consistency analysis on the motion command deviation of multiple drive units. The motion control module 240 is used to calculate the correction amount based on the motion command deviation if the consistency analysis result shows that the motion command deviation is a mechanical deviation, and then add the correction amount to the motion control command of the next cycle and send it to multiple drive units. If the consistency analysis result shows that the motion command deviation is a time misalignment deviation, the current output state of the motion control command is maintained.

[0075] The collaborative work of various functional modules provides a hardware and software foundation for resolving the confusion between mechanical deviation and time misalignment.

[0076] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A digital control method for complex workpieces in a five-axis linkage machining center, characterized in that, include: Acquire feedback data from multiple drive units corresponding to the same moving target; The feedback data from the multiple drive units are correlated to a unified reference benchmark in the time dimension; Based on the correlated feedback data, the motion command deviation of each drive unit is determined, and a consistency analysis is performed on the motion command deviations of the multiple drive units. If the consistency analysis shows that the motion command deviation is a mechanical deviation, the correction amount is calculated based on the motion command deviation, and the correction amount is added to the motion control command of the next cycle and sent to the multiple drive units. If the consistency analysis shows that the motion command deviation is a time misalignment deviation, the current output state of the motion control command is maintained.

2. The digital control method for complex workpieces in a five-axis linkage machining center according to claim 1, characterized in that, The step of acquiring feedback data from multiple drive units corresponding to the same moving target includes: Real-time monitoring of the feedback link status of the multiple drive units; When an interruption is detected in the feedback link status of the drive unit, real-time feedback data of the drive unit whose feedback link status is not interrupted is obtained. Obtain the physical coupling constraint model of the same moving target, wherein the physical coupling constraint model characterizes the kinematic relationship between the multiple driving units; By combining the real-time feedback data of the drive unit whose feedback link state is not interrupted with the physical coupling constraint model, the virtual feedback data of the drive unit whose feedback link state is interrupted during the interruption period is reconstructed as its feedback data.

3. The digital control method for complex workpieces in a five-axis linkage machining center according to claim 1, characterized in that, The step of correlating the feedback data of the multiple drive units to a unified reference benchmark in the time dimension includes: Obtain the monotonically increasing sequence identifier attached to the motion command issued by the machining center, and record the arrival time of the feedback data; Calculate the communication link delay corresponding to each driving unit based on the monotonically increasing sequence identifier and the arrival time; The feedback data is compensated by utilizing the communication link delay corresponding to each of the driving units, so as to align the feedback data of each driving unit to the reference benchmark and use it as the associated feedback data.

4. The digital control method for complex workpieces in a five-axis linkage machining center according to claim 3, characterized in that, The step of compensating the feedback data using the communication link delay corresponding to each of the driving units includes: Establish a delay statistics window for each of the driving units, and calculate the fluctuation characteristic value of the communication link delay within the delay statistics window; When the fluctuation characteristic value exceeds the first preset threshold, the evolution trend of the communication link delay corresponding to the driving unit in the time series is extracted. Based on the evolution trend, predictive phase correction is performed on the feedback data of the corresponding driving unit to eliminate the impact of random jitter of the communication link delay on the alignment accuracy of the reference reference.

5. The digital control method for complex workpieces in a five-axis linkage machining center according to claim 1, characterized in that, The steps of determining the motion command deviation of each drive unit based on the correlated feedback data, and performing a consistency analysis on the motion command deviations of the multiple drive units, include: Based on the associated feedback data, the positional deviation between the actual position and the command position of each drive unit is calculated. Compare the direction and magnitude differences of the position deviations of the multiple drive units; If the position deviation directions of all the drive units are the same, and the magnitude difference of all of them is less than the second preset threshold, then the result of the consistency analysis is: the motion command deviation is a mechanical deviation; If the position deviation directions of at least two of the drive units are not the same, or the difference in their magnitudes exceeds the second preset threshold, and at least one of the drive units exhibits a preset first fluctuation characteristic or a preset second fluctuation characteristic, then the result of the consistency analysis is: the motion command deviation is a time misalignment deviation.

6. The digital control method for complex workpieces in a five-axis linkage machining center according to claim 5, characterized in that, The preset first fluctuation characteristic includes: the difference between the maximum and minimum values ​​of the arrival time of the feedback data from the driving unit within a preset time window exceeds a third preset threshold.

7. The digital control method for complex workpieces in a five-axis linkage machining center according to claim 5, characterized in that, The preset second fluctuation characteristic includes: the driving unit is located on the communication link through the intermediate conversion module, and the change in the arrival time of its feedback data between two consecutive times exceeds the fourth preset threshold.

8. The digital control method for complex workpieces in a five-axis linkage machining center according to claim 5, characterized in that, When the result of the consistency analysis is that the motion command deviation is a time misalignment deviation, the method further includes: Obtain the current values ​​of the plurality of driving units; When the difference in current values ​​between at least two of the driving units exceeds a first preset ratio, and the direction of the difference in current values ​​is consistent with the expected force direction of the structure of the same moving target, the result of the consistency analysis is corrected to: the motion command deviation is the transient torsional deviation of the structure. Otherwise, the result of the consistency analysis remains as follows: the motion command deviation is a time misalignment deviation.

9. A digital control method for complex workpieces in a five-axis linkage machining center according to claim 8, characterized in that, When the result of the consistency analysis is corrected to indicate that the motion command deviation is a transient torsional deviation of the structure, the method further includes the following steps: An asymmetric speed compensation amount is generated based on the difference in the current values, and the asymmetric speed compensation amount is superimposed on the motion control command of the next cycle and sent to the multiple drive units to release torsional stress. When the result of the consistency analysis remains that the motion command deviation is a time misalignment deviation, the method further includes the following steps: Maintaining the current output state of the motion control command, the subsequently acquired feedback data is weighted and smoothed to eliminate signal glitches in the feedback data.

10. A digital control system for complex workpieces in a five-axis linkage machining center, used to execute the digital control method for complex workpieces in a five-axis linkage machining center as described in any one of claims 1 to 9, characterized in that, The system includes: The data acquisition module is used to acquire feedback data from multiple drive units corresponding to the same moving target; The time correlation module is used to correlate the feedback data of the multiple driving units to a unified reference benchmark in the time dimension; The consistency analysis module is used to determine the motion command deviation of each drive unit based on the associated feedback data, and to perform consistency analysis on the motion command deviation of the multiple drive units. The motion control module is configured to calculate a correction amount based on the motion command deviation if the consistency analysis shows that the motion command deviation is a mechanical deviation, and then add the correction amount to the motion control command of the next cycle and send it to the multiple drive units; if the consistency analysis shows that the motion command deviation is a time misalignment deviation, the module maintains the current output state of the motion control command.

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