Real-time control method for production line transmission speed based on digital twin

Abstract

This invention relates to the field of intelligent manufacturing and industrial automation control technology, specifically a real-time control method for production line transmission speed based on digital twins. The method includes: acquiring encoder speed data, photoelectric occupancy signals, workstation completion signals, driver feedback parameters, work-in-process label information, real-time occupancy data, and buffer segment occupancy count data for each section of the target production line; calling a preset digital twin model of the production line to perform virtual-real data mapping and signal anti-jitter reconstruction, generating workstation material receiving status, workpiece conveying type, equipment status, and response delay value; obtaining a real-time congestion value based on a weighted sum of static space occupancy ratio, spacing compression rate, and cycle time difference rate; determining the operating level based on the real-time congestion value, workstation material receiving status, and equipment status, and outputting the results to the frequency converter, servo motor, and brake structure to adjust the transmission speed of each section in real time; this invention reduces material accumulation and idle conveying between production line sections.

Description

Technical Field

[0001] This invention relates to the field of intelligent manufacturing and industrial automation control technology, specifically a method for real-time control of production line transmission speed based on digital twins. Background Technology

[0002] As production pace continues to increase, production lines face higher requirements in terms of continuous multi-segment conveying, buffering, and collaborative workstation handling. In particular, in scenarios involving mixed conveying of different workpieces, fluctuations in downstream workstation processing, and significant changes in local loads, how to adjust the transmission speed of each segment in a timely manner has become an important problem that needs to be solved in the field of production line control.

[0003] Traditional production line transmission control currently relies mainly on the following methods: fixed-cycle conveying, start-stop control based on single-point sensor signals, and single-section speed reduction or shutdown control according to preset thresholds.

[0004] However, fixed-cycle conveying, single-point signal start / stop control, and single-segment control based on preset thresholds all have certain drawbacks. For example, the fixed-cycle method is difficult to adapt to fluctuations in the downstream workstation's capacity and changes in buffer occupancy, which can easily lead to material accumulation or idle conveying between segments. The control method based on single-point sensor signals does not adequately reflect the actual distance between adjacent workpieces, the equipment's load-bearing status, and the trend of cycle imbalance. The method of controlling according to preset thresholds has problems with insufficient response to load jumps, pseudo-abnormal impacts, and multi-segment linkage, making it difficult to adapt to the real-time changing conveying needs of the production line. Summary of the Invention

[0005] The purpose of this invention is to provide a real-time control method for production line transmission speed based on digital twins, and to solve the following technical problems:

[0006] It avoids misjudgments caused by mismatched refreshes of different channels and oscillations of the entire line caused by local short-term fluctuations. It can also continuously quantify the segment status by calculating real-time congestion values ​​based on multi-factor weighting and dynamically adjust the transmission speed of each segment according to the status changes.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A real-time control method for production line transmission speed based on digital twins includes:

[0009] S1. Acquire encoder speed data, photoelectric occupancy signals, workstation completion signals, driver feedback parameters, work-in-process label information, and real-time occupancy data and occupancy count data of the target buffer section for each section of the target production line;

[0010] S2. Call the digital twin model to map and reorganize the encoder speed data, photoelectric occupancy signal, station completion signal, driver feedback parameters and work-in-process label information to generate a group of operating status information containing station receiving status, workpiece conveying type, equipment status and response delay value;

[0011] S3. Determine the target safety distance based on the workpiece conveying type; use the ratio of the occupancy time of the photoelectric occupancy signal to the preset statistical period as the static space occupancy ratio; obtain the material arrival rate and release rate from the number of signal triggers at the workstation within the preset time window, and divide the difference between the two by the release rate to obtain the cycle time difference rate; calculate the spacing compression rate from the encoder speed data and the target safety distance; and sum the static space occupancy ratio, spacing compression rate, and cycle time difference rate with preset static space occupancy weights, spacing compression weights, and cycle time difference weights respectively to obtain the real-time congestion value.

[0012] S4. Based on real-time congestion values, workstation material receiving status, and equipment status, threshold comparison is performed to determine the current operating level of each section of the target production line;

[0013] S5. Generate control action commands according to the operating level and output them to the actuators of each section, including frequency converters, servo motors and brake structures, to adjust the transmission speed.

[0014] Preferably, the generation of the running status information group in step S2 specifically includes:

[0015] S21. Calculate the time difference between the completion signals of the workstations in adjacent cycles to obtain the cycle completion time, and calculate the variance of the cycle completion time. Compare the variance of the cycle completion time with a preset variance threshold. If it is less than the preset variance threshold, a normal material receiving status is generated at the workstation. If it is greater than or equal to the preset variance threshold, a delayed material receiving status is generated at the workstation.

[0016] S22. Parse the product feature code in the work-in-process label information, and classify it into vulnerable type, inertia type or ordinary type according to the preset mapping relationship between feature code and conveying type, and generate workpiece conveying type;

[0017] S23. Compare the torque utilization rate and following error in the driver feedback parameters with the preset torque threshold and error threshold respectively. If both are less than the corresponding threshold, generate a full-capacity equipment state. If any is greater than or equal to the corresponding threshold and less than the limit threshold, generate a derated equipment state. If any is greater than or equal to the limit threshold, generate a prohibited equipment state. The limit threshold is greater than the corresponding threshold.

[0018] S24. Obtain the speed command issuance time of the previous control cycle, and calculate the difference between the speed command issuance time of the previous control cycle and the encoder speed data feedback time of the current cycle to generate a response delay value that characterizes the hysteresis relationship.

[0019] Preferably, the calculation of real-time congestion values ​​in step S3 specifically includes:

[0020] S31. Obtain historical steady-state operation data of each section of the target production line, and use constrained least squares method for fitting and updating to generate initial static space occupancy weights, spacing compression weights and cycle time difference weights;

[0021] S32. If the workpiece conveying type is inertia type, then add a preset first spacing compensation value to the initial spacing compression weight to obtain the corrected spacing compression weight.

[0022] S33. Calculate the physical cache balance of the target cache segment based on the real-time occupancy data and the preset total cache capacity. If the physical cache balance is greater than the preset length threshold, add the preset second space compensation value to the initial static space occupancy weight to obtain the corrected static space occupancy weight. If the physical cache balance is not greater than the preset length threshold, use the initial static space occupancy weight directly as the corrected static space occupancy weight.

[0023] S34. Multiply the corrected static space occupancy weight, the corrected spacing compression weight, and the initial beat difference weight by the static space occupancy ratio, spacing compression rate, and beat difference rate, respectively, and sum them up to obtain the corrected real-time congestion value.

[0024] Preferably, the calculation of the spacing compression ratio in step S3 specifically includes:

[0025] S301. Integrate the encoder speed data into linear velocity within a continuous sampling period, and combine it with the triggering timing of the photoelectric occupancy signal to calculate the physical distance between the current adjacent workpieces.

[0026] S302. Determine the workpiece conveying type. If it is an inertia type, set the target safety distance to the first safety distance threshold. If it is a normal type, set the target safety distance to the second safety distance threshold. If it is a fragile type, set the target safety distance to the third safety distance threshold. The third safety distance threshold is greater than the first safety distance threshold, and the first safety distance threshold is greater than the second safety distance threshold.

[0027] S303. Determine whether the physical distance value is less than the target safety distance; if so, calculate the ratio of the physical distance value to the target safety distance, and take the difference between the two as the distance compression rate; if not, set the distance compression rate to zero.

[0028] Preferably, step S4, determining the current operating level of each section of the target production line, specifically includes:

[0029] S41. Compare the real-time congestion value with the system's preset first congestion judgment threshold, second congestion judgment threshold, and third congestion judgment threshold, with the first congestion judgment threshold, second congestion judgment threshold, and third congestion judgment threshold increasing sequentially;

[0030] S42. If the real-time congestion value is less than the first congestion judgment threshold and the equipment status is full capacity, it is judged as a level one normal operation status.

[0031] S43. If the real-time congestion value is greater than or equal to the first congestion judgment threshold and less than the second congestion judgment threshold, and the equipment status is full capacity acceptance, then it is judged as a level two slow-down reception status.

[0032] S44. If the real-time congestion value is greater than or equal to the second congestion judgment threshold and less than the third congestion judgment threshold, or the equipment status is downgraded to reduced capacity acceptance, then it is judged as a level three congestion prevention state.

[0033] S45. If the real-time congestion value is greater than or equal to the third congestion judgment threshold, or the equipment status is prohibited from sending in, it is judged as a level four shutdown and congestion relief state.

[0034] Preferably, in step S5, when the operating level is Level 2 speed reduction reception state or Level 3 congestion prevention state, the specific steps include:

[0035] S51. If it is determined to be a level 2 speed reduction receiving state, a control action command to reduce the transmission speed is sent to the frequency converters of each section of the target production line, and a delayed material receiving confirmation signal is broadcast to the adjacent upstream section so that the adjacent upstream section can use the nearby buffer section for buffering and temporary storage.

[0036] S52. If the situation is determined to be a Level 3 congestion prevention state, the downstream station buffer section will be switched to a separate speed-limiting queue, and a delayed release synchronization signal will be written to the adjacent upstream section to implement upstream supply slowdown feeding.

[0037] S53. For workpieces of the vulnerable type transported in the three-level congestion prevention state, issue specific acceleration and deceleration commands with extended acceleration and deceleration times.

[0038] Preferably, the method further includes the following steps:

[0039] S61. Calculate the load change rate of each section of the target production line within a preset time window based on the driver feedback parameters. When the load change rate is greater than the preset jump threshold, ignore the aforementioned control action command generated based on the real-time congestion value and force the pre-start control to be executed.

[0040] S62. Issue intermediate frequency preparation instructions to the frequency converters in each section of the target production line, release the brake structure in advance, and zero-correct the occupancy count data, while opening a short-time high-frequency sampling window;

[0041] S63. If the system is determined to be in a level 4 shutdown and blockage relief state, the bidirectional blockage relief mechanism is triggered, the input terminal of the adjacent upstream section is locked, a low-speed jog mode enable command is sent to the frequency converter, and only the movement command in the blockage relief direction is retained.

[0042] Preferably, the method further includes the following steps:

[0043] S71. Obtain the instantaneous current data from the driver feedback parameters. If the instantaneous current data is greater than the preset current spike threshold and the encoder speed data is less than the preset speed loss threshold, skip the calculation of the real-time congestion value, directly determine it as a mechanical impact event, and block the issuance of the entire line shutdown command.

[0044] S72. When the real-time congestion value drops and the operating level is downgraded from Level 3 congestion prevention state or Level 4 shutdown and congestion relief state to Level 2 speed reduction receiving state or Level 1 normal operation state, execute a three-stage progressive recovery action to update the target speed command in the control action command.

[0045] S73. If the real-time congestion value is less than the second congestion judgment threshold and decreases for a consecutive preset number of sampling cycles, then the target speed command is set to 60% of the preset baseline process speed;

[0046] S74. If the variance of the cycle completion time of a downstream station for a consecutive preset number of cycles is less than the set steady-state threshold, then the target speed command is set to 80% of the baseline process speed;

[0047] S75. If the response delay value is less than the tolerance threshold and the photoelectric occupancy signal has no jump, then set the target speed command to 100% of the reference process speed.

[0048] The beneficial effects of this invention are:

[0049] 1. This invention maps and reassembles multi-source underlying data such as encoder speed data and photoelectric occupancy signals by calling a digital twin model, and obtains the real-time congestion value by weighted summation of static space occupancy ratio, spacing compression rate and cycle time difference rate. Compared with the traditional control method that relies on fixed cycle time or single-point sensor signals, this method combines the evaluation of space occupancy, workpiece spacing and cycle time imbalance trend, realizes continuous dynamic quantification of section status, avoids the problem of misjudgment caused by insufficient reflection of single-point signals, and can adjust the transmission speed in a timely manner according to the current actual operating status, reducing material accumulation and idle conveying between production line sections.

[0050] 2. This invention can determine the target safety distance based on different workpiece conveying types, and when the operating level is determined to be a level 2 deceleration receiving state or a level 3 congestion prevention state, it can send a delayed receiving confirmation signal or a delayed release synchronization signal to the adjacent upstream section. This cross-section synchronization linkage mechanism changes the traditional single-section control method with preset thresholds. It can use the adjacent buffer section to temporarily store and slow down the upstream feeding before obvious congestion occurs, thus digesting the risk of local congestion at the front end and taking into account both the conveying safety under different working conditions and the stability of multi-section linkage.

[0051] 3. This invention addresses complex actual operating conditions by introducing a forced coverage step to handle special load surge scenarios and a rapid judgment step to block false anomalies. By combining instantaneous current data and encoder speed data, it can identify and skip false anomalies caused by mechanical shock events, blocking unnecessary line shutdown commands. Simultaneously, it forcibly executes pre-start control during load surges and performs a three-stage progressive recovery action after congestion is cleared. This compensates for the shortcomings of traditional methods in responding to load surges and abnormal shocks, ensuring the stability of the actuator in special scenarios and avoiding line control oscillations caused by short-term fluctuations. Attached Figure Description

[0052] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0053] Figure 1 A flowchart illustrating a real-time control method for production line transmission speed based on digital twins, provided in an embodiment of this application. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Please see Figure 1 A real-time control method for production line transmission speed based on digital twins includes:

[0056] S1. Acquire encoder speed data, photoelectric occupancy signals, workstation completion signals, driver feedback parameters, work-in-process label information, and real-time occupancy data and occupancy count data of the target buffer section for each section of the target production line;

[0057] S2. Call the digital twin model to map and reorganize encoder speed data, photoelectric occupancy signal, station completion signal, driver feedback parameters and work-in-process label information to generate a group of operating status information containing station receiving status, workpiece conveying type, equipment status and response delay value;

[0058] S3. Determine the target safety distance based on the workpiece conveying type; use the ratio of the occupancy time of the photoelectric occupancy signal to the preset statistical period as the static space occupancy ratio; obtain the material arrival rate and release rate from the number of signal triggers at the workstation within the preset time window, and divide the difference between the two by the release rate to obtain the cycle time difference rate; calculate the spacing compression rate from the encoder speed data and the target safety distance; and sum the static space occupancy ratio, spacing compression rate, and cycle time difference rate with preset static space occupancy weights, spacing compression weights, and cycle time difference weights respectively to obtain the real-time congestion value.

[0059] S4. Based on real-time congestion values, workstation material receiving status, and equipment status, threshold comparison is performed to determine the current operating level of each section of the target production line;

[0060] S5. Generate control action commands according to the operating level and output them to the actuators of each section, including frequency converters, servo motors and brake structures, to adjust the transmission speed.

[0061] In this implementation, the field data is first written into the register image area of ​​the control system by the data acquisition unit. The control system reads encoder speed data, photoelectric occupancy signal, work station completion signal, driver feedback parameters, work-in-process label information, real-time occupancy data and buffer segment occupancy count data in each control cycle.

[0062] By calling the preset digital twin model of the production line, these underlying signals are mapped, recombined and judged to obtain the workstation material receiving status, workpiece conveying type, equipment status and response delay value;

[0063] Based on this, the real-time congestion value is calculated, and control action commands corresponding to the frequency converter, servo motor and brake structure are generated in combination with the operation level rules, so that the transmission speed of each section is adjusted according to the current state, instead of using fixed beat or single-point threshold control.

[0064] The implementation method of step S1 is explained in detail: the encoder speed data collected by the data acquisition device of each section of the target production line, namely the linear speed feedback value of the conveyor in the current control cycle, the photoelectric occupancy signal, namely the occupancy level change formed when the workpiece passes the detection position, the station completion signal, namely the release or completion mark given by the downstream station after completing the current workpiece processing, the driver feedback parameters including at least torque utilization rate and following error, the work-in-process label information including at least product feature code, the real-time occupancy data of the target buffer section, and the buffer section occupancy count data used to accumulate and record the number of buffered parts entering and leaving the buffer;

[0065] In practice, encoder speed data can be written to a high-speed register by the encoder input module, photoelectric occupancy signal and station completion signal can be latched by a digital input register, driver feedback parameters can be provided by a driver feedback register, and work-in-process label information can be written to the control system memory area by the label reading unit.

[0066] The state abstraction-related operation process retrieves data from the register image area according to the control cycle, and writes the current cycle snapshot to the local buffer after reading, so that the digital twin model can call it; this implementation does not directly use signals with different refresh cycles in parallel, but first fixes various raw quantities into the same cycle snapshot, and then enters the subsequent processing;

[0067] This avoids interference between multiple data sources due to asynchronous updates; this implementation method can achieve stable access to field data based on a unified periodic snapshot, avoid misjudgment caused by mismatch in refreshes of different channels, and provide a consistent data foundation for subsequent status determination;

[0068] The implementation method of step S2 is explained in detail: the preset production line digital twin model is called, and the data is mapped to virtual and real data and recombined with signal anti-shake based on encoder speed data, photoelectric occupancy signal, station completion signal, driver feedback parameters and work-in-process label information to generate a group of operating status information including station material receiving status, workpiece conveying type, equipment status and response delay value.

[0069] Among them, virtual and real data mapping refers to mapping the speed, occupancy, completion, drive feedback and tag information collected on site to the segments, workstations, workpieces and actuator objects in the digital twin model, so that each segment has a state synchronized with the site in the digital model;

[0070] Signal anti-shake reconstruction refers to time alignment and semantic merging of underlying fragmented signals to avoid single interruptions, short spikes or single-cycle fluctuations directly changing the control results.

[0071] In practical implementation, the digital twin model can maintain the operation status cache by segment. Each segment corresponds to a set of status fields, including the workstation receiving status field, the workpiece conveying type field, the equipment status field, and the response delay value field.

[0072] Within each control cycle, the model reads a data snapshot from the local buffer and updates the above fields. After the update is completed, the result is written to the decision-making state buffer for subsequent congestion calculation modules to read. After reading, the model enters the next cycle for refresh.

[0073] Step S2 generates a running status information group, which specifically includes:

[0074] S21. Calculate the time difference between the completion signals of the workstations in adjacent cycles to obtain the cycle completion time, and calculate the variance of the cycle completion time. Compare the variance of the cycle completion time with a preset variance threshold. If it is less than the preset variance threshold, a normal material receiving status is generated at the workstation. If it is greater than or equal to the preset variance threshold, a delayed material receiving status is generated at the workstation.

[0075] S22. Parse the product feature code in the work-in-process label information, and classify it into vulnerable type, inertia type or ordinary type according to the preset mapping relationship between feature code and conveying type, and generate workpiece conveying type;

[0076] S23. Compare the torque utilization rate and following error in the driver feedback parameters with the preset torque threshold and error threshold respectively. If both are less than the corresponding threshold, generate a full-capacity equipment state. If any is greater than or equal to the corresponding threshold and less than the limit threshold, generate a derated equipment state. If any is greater than or equal to the limit threshold, generate a prohibited equipment state. The limit threshold is greater than the corresponding threshold.

[0077] S24. Obtain the speed command issuance time of the previous control cycle, and calculate the difference between the speed command issuance time of the previous control cycle and the encoder speed data feedback time of the current cycle to generate a response delay value that characterizes the hysteresis relationship.

[0078] The implementation of steps S21 to S24 is explained in detail: The station completion signal is acquired, and statistical processing is performed on the station completion signal based on the cycle completion time of adjacent cycles to generate the station material receiving status; in one implementation, the length of the most recent statistical window used to balance sensitivity and stability is recorded. Completion time of adjacent cycles within And calculate its average value. :

[0079]

[0080] The variance of cycle completion time, which characterizes the degree of dispersion of the completion time of each workstation within adjacent cycles around its average value, is calculated. In the formula The current period number within the statistics window; if If the variance is less than the preset variance threshold, a normal material receiving status is generated at the workstation.

[0081] like If the variance threshold is greater than or equal to the variance threshold, a delayed material receiving status is generated at the workstation. This implementation captures the continuous fluctuations in the workstation's receiving capacity through variance statistics, distinguishing between a single occasional slowdown and a continuous slowdown in material receiving. This can reduce the situation where short-term fluctuations are amplified into speed adjustments for the entire production line.

[0082] Obtain the work-in-process label information, parse the work-in-process label information according to the mapping relationship between product feature code and conveying type, and generate the workpiece conveying type;

[0083] Among them, the vulnerable type is used to improve the safety distance and constrain acceleration and deceleration in the future, the inertia type is used to improve the weight of the distance compression evaluation in the future, and the ordinary type adopts conventional conveying control conditions.

[0084] This implementation converts the tag information into a conveying type that can be directly controlled, enabling differentiated control of the conveying process based on the workpiece type.

[0085] Obtain the driver feedback parameters, and perform threshold comparison on the driver feedback parameters based on the torque utilization rate, which reflects the current available driving capacity of the drive device, and the following error, which reflects the deviation between the command position or speed and the actual execution state, to generate the device status.

[0086] If both torque utilization and following error are less than the corresponding threshold used to distinguish between normal and derating operations, then a full-capacity operation status is generated.

[0087] If any value is greater than or equal to the corresponding threshold and less than the limit threshold used to distinguish between continued input and prohibited input, a device status of reduced acceptance is generated; if any value is greater than or equal to the limit threshold, a device status of prohibited input is generated.

[0088] This implementation method incorporates both load capacity and execution deviation into the judgment, so that the equipment status not only reflects whether the equipment has the basic operating conditions, but also reflects its current actual ability to accept incoming materials.

[0089] Obtain the speed command issuance time of the previous control cycle, and calculate the difference between the two based on the encoder speed data feedback time of the current cycle to generate a response delay value;

[0090] The response delay value represents the time difference between the field speed feedback and the encoder data after the control system issues a speed command. This response delay value represents the time difference between the time the command is issued and the time the encoder data is updated. It is used to characterize the hysteresis state of the actuator and serves as an input parameter for determining whether the output speed command is restored or corrected.

[0091] Step S3 calculates the real-time congestion value, specifically including:

[0092] S31. Obtain historical steady-state operation data of each section of the target production line, and use constrained least squares method for fitting and updating to generate initial static space occupancy weights, spacing compression weights and cycle time difference weights;

[0093] S32. If the workpiece conveying type is inertia type, then add a preset first spacing compensation value to the initial spacing compression weight to obtain the corrected spacing compression weight.

[0094] S33. Calculate the physical cache balance of the target cache segment based on the real-time occupancy data and the preset total cache capacity. If the physical cache balance is greater than the preset length threshold, add the preset second space compensation value to the initial static space occupancy weight to obtain the corrected static space occupancy weight. If the physical cache balance is not greater than the preset length threshold, use the initial static space occupancy weight directly as the corrected static space occupancy weight.

[0095] S34. Multiply the corrected static space occupancy weight, the corrected spacing compression weight, and the initial beat difference weight by the static space occupancy ratio, spacing compression rate, and beat difference rate, respectively, and sum them up to obtain the corrected real-time congestion value.

[0096] The implementation method of physical buffer capacity constraint is explained in detail; historical steady-state operation data of each section of the target production line is obtained, that is, the occupancy, spacing and entry and exit cycle data accumulated by the production line under the condition of no obvious blockage and relatively stable cycle time. According to the constrained least squares method, the static space occupancy weight, spacing compression weight and cycle time difference weight are fitted and updated to generate the initial static space occupancy weight, spacing compression weight and cycle time difference weight.

[0097] The constrained least squares method is used to make the calculated congestion evaluation results more consistent with the steady-state sample operation under the boundary conditions that each weight is not less than zero and the sum is kept within a preset range, and to make the weights of different sections more in line with their respective structural characteristics.

[0098] Obtain the workpiece conveying type, and based on the inertia type judgment result, compensate the initial spacing compression weight to obtain the corrected spacing compression weight;

[0099] If the workpiece conveying type is inertia type, an additional first spacing compensation value is added to the initial spacing compression weight for inertia type workpieces to strengthen the buffer distance requirements of inertia type workpieces during deceleration and stopping phases; this implementation method makes inertia type workpieces more distance sensitive in congestion assessment.

[0100] Obtain real-time usage data and preset total cache capacity, and calculate the physical cache reserve of the target cache segment based on the relationship between the two.

[0101] If the physical cache balance is greater than the preset length threshold used to distinguish between two cases where there is still enough buffer and where the buffer is insufficient, then a preset second space compensation value is added to the initial static space occupancy weight to obtain the corrected static space occupancy weight; if the physical cache balance is not greater than the preset length threshold, then the initial static space occupancy weight is directly used as the corrected static space occupancy weight.

[0102] Among them, the physical buffer capacity reflects the length or capacity of the buffer segment that can still accommodate workpieces. The second space compensation value is used to appropriately increase the evaluation weight of space occupancy factors when the buffer is still sufficient, so that the system can more accurately distinguish between the available buffer to absorb fluctuations and the state that is close to full. In specific implementation, if the total buffer capacity is denoted as... Real-time occupancy data is recorded as Then the physical cache space can be calculated as follows: Alternatively, it can be obtained using an equivalent length expression.

[0103] Obtain the corrected static space occupancy weight Corrected spacing compression weights Weight of difference from the initial beat Based on the static space occupancy ratio Spacing compression rate With the difference rate of rhythm The real-time congestion value is corrected and calculated, which can be expressed as:

[0104]

[0105] This yields the corrected real-time congestion value. This implementation method can combine the workpiece inertia characteristics and buffer remaining capacity to make the congestion value more closely match the actual situation, and avoid the distortion of judgment by fixed weight under different sections and different workpiece conditions.

[0106] Step S3 calculates the spacing compression ratio, specifically including:

[0107] S301. Integrate the encoder speed data into linear velocity within a continuous sampling period, and combine it with the triggering timing of the photoelectric occupancy signal to calculate the physical distance between the current adjacent workpieces.

[0108] S302. Determine the workpiece conveying type. If it is an inertia type, set the target safety distance to the first safety distance threshold. If it is a normal type, set the target safety distance to the second safety distance threshold.

[0109] If it is a vulnerable type, the target safety distance is set to the third safety distance threshold, which is greater than the first safety distance threshold and the first safety distance threshold is greater than the second safety distance threshold.

[0110] S303. Determine whether the physical distance value is less than the target safety distance; if so, calculate the ratio of the physical distance value to the target safety distance, and take the difference between the two as the distance compression rate; if not, set the distance compression rate to zero.

[0111] The implementation methods of steps S3 and S301 to S303 are explained in detail; the workpiece conveying type is obtained, and the target safety distance is determined according to the preset safety distance rules;

[0112] The photoelectric occupancy signal, workstation completion signal and encoder speed data are acquired. Based on the occupancy statistics, entry and exit cycle statistics and spacing calculation results, the various indicators are weighted to obtain a real-time congestion value that reflects the degree of congestion in the current section caused by space occupancy, workpiece spacing and cycle imbalance. The larger the value, the closer the section is to accumulation or the state that is not suitable for continued high-speed feeding.

[0113] In practice, the target safety distance is determined based on the workpiece conveying type; if the workpiece conveying type is inertia type, the target safety distance is set to the first safety distance threshold.

[0114] If it is a normal type, the target safety distance is set to the second safety distance threshold; if it is a vulnerable type, the target safety distance is set to the third safety distance threshold, and the third safety distance threshold is greater than the first safety distance threshold, and the first safety distance threshold is greater than the second safety distance threshold.

[0115] The third safety distance threshold is relatively large because fragile workpieces are more sensitive to adjacent collisions; the first safety distance threshold is in the middle because inertial workpieces need to retain more buffer when decelerating; the second safety distance threshold is relatively small, corresponding to the normal conveying needs of ordinary workpieces.

[0116] To calculate the pitch compression ratio, the encoder is used to obtain data during continuous sampling periods. Linear velocity within It can be combined with the photoelectric occupancy signal triggering timing used to determine the relative order of preceding and following workpieces, and its calculation formula is as follows:

[0117]

[0118] The displacement is obtained by accumulating the values ​​to represent the physical distance between adjacent workpieces. In the formula The number of samples taken between the previous reference trigger and the next reference trigger. From arrive The current accumulated sampling number;

[0119] Determine the physical distance value Is it less than the target safety clearance determined by the type of workpiece transport? If so, calculate the ratio of the physical distance value to the target safety distance, and use the difference between the two as the distance compression rate, which reflects the degree of compression of the current adjacent distances. ,Right now ;

[0120] If the physical distance value is not less than the target safety distance, the distance compression rate is set to zero. This implementation method incorporates the calculation of the actual distance between adjacent workpieces. Even if the physical buffer margin does not reach zero, the system can determine whether the distance between adjacent workpieces is in the critical state of interference by the distance compression rate.

[0121] To calculate the static space occupancy ratio, a statistical period is obtained. and the cumulative duration of photoelectric use within that period. You can press The static space occupancy ratio, which characterizes the degree to which the buffer or detection section is continuously occupied by the workpiece within the current statistical period, is calculated. When this ratio When the value increases, it indicates that the gap within the section has decreased;

[0122] To calculate the beat difference rate, statistics are compiled for corresponding lengths. Upstream entry count within the preset time window Number of downstream releases The upstream feed arrival rate was calculated separately. Release rate of downstream workstations ;

[0123] Press The cycle time difference rate, which characterizes the degree of deviation between downstream release capacity and upstream supply speed, was calculated. ;

[0124] When the arrival rate exceeds a certain percentage of the release rate, this difference rate A positive increase indicates that the input material flow rate exceeds the processing flow rate of the downstream station; if the release rate... If a division by zero occurs due to a value of zero, a specific compensation calculation will be performed:

[0125] Before performing division, Perform a zero-value check if If it equals zero, then directly... The system can use a preset maximum clock imbalance penalty limit, or introduce a very small normal number as a compensation denominator to replace the actual zero value in the calculation, to ensure that the system can still quantify congestion and output limiting actions normally when there is extreme congestion.

[0126] In one implementation, if If the level is low, the system can first determine that the segment status needs to be given more attention, and then send the calculation result to the subsequent weight summation stage;

[0127] To calculate real-time congestion values Obtain the static space occupancy weight used to balance the contribution of cache occupancy to congestion assessment. Spacing compression weights are used to reflect the impact of reduced distance between adjacent workpieces on collision and stacking risks. And the weight of the cycle time difference used to reflect the continuous backlog trend caused by the mismatch between incoming materials and release. ; The ratio of static space occupancy Spacing compression rate With the difference rate of rhythm Each is weighted and summed with its corresponding weight, i.e., according to the formula:

[0128]

[0129] Get real-time congestion values In one implementation, , , Non-negative values ​​can be taken and the sum is 1; this implementation combines the evaluation of three factors: space, distance and cycle time; this can both monitor the material backlog that has been formed and identify the state where the load is not yet full but the supply and demand imbalance trend is obvious;

[0130] This implementation method can calculate real-time congestion values ​​based on multi-factor weighting, thereby achieving continuous quantification of the segment status and avoiding insufficient sensitivity of a single signal.

[0131] A brief explanation of the overall execution method of steps S4 and S5 is provided: obtain the real-time congestion value, workstation material receiving status and equipment status, and judge the current operating level of each section of the target production line according to the preset threshold rules; obtain the operating level, generate control action commands according to the corresponding action rules, and output them to the frequency converter, servo motor and brake structure.

[0132] Among them, the control action command can be written into the actuator command buffer. The execution layer reads the target speed, acceleration and deceleration parameters and action enable bit in the buffer in the current control cycle, and refreshes it to the inverter control word, servo enable word and brake control bit. In this way, the aforementioned congestion evaluation result will not stay at the calculation layer, but will directly become the conveyor speed adjustment action.

[0133] This implementation method completes the entire process from on-site data collection, state reorganization, congestion calculation to actuator action output, enabling each section of the production line to adjust the transmission speed in real time according to the current state.

[0134] In this embodiment of the invention, step S4, determining the current operating level of each section of the target production line, specifically includes:

[0135] S41. Compare the real-time congestion value with the system's preset first congestion judgment threshold, second congestion judgment threshold, and third congestion judgment threshold, with the first congestion judgment threshold, second congestion judgment threshold, and third congestion judgment threshold increasing sequentially;

[0136] S42. If the real-time congestion value is less than the first congestion judgment threshold and the equipment status is full capacity, it is judged as a level one normal operation status.

[0137] S43. If the real-time congestion value is greater than or equal to the first congestion judgment threshold and less than the second congestion judgment threshold, and the equipment status is full capacity acceptance, then it is judged as a level two slow-down reception status.

[0138] S44. If the real-time congestion value is greater than or equal to the second congestion judgment threshold and less than the third congestion judgment threshold, or the equipment status is downgraded to reduced capacity acceptance, then it is judged as a level three congestion prevention state.

[0139] S45. If the real-time congestion value is greater than or equal to the third congestion judgment threshold, or the equipment status is prohibited from sending in, it is judged as a level four shutdown and congestion relief state.

[0140] The implementation methods of steps S41 to S45 are explained in detail: real-time congestion values ​​and equipment status are obtained, and the current operating level of each section of the target production line is judged according to the first congestion judgment threshold, the second congestion judgment threshold, and the third congestion judgment threshold preset by the system, which correspond to the boundaries of slightly restricted, obviously restricted, and severely restricted, respectively.

[0141] Among them, the equipment status includes full capacity acceptance, reduced capacity acceptance, and prohibited input. Its function is to directly incorporate the equipment's capacity into the operation level judgment, rather than determining it solely based on the congestion value.

[0142] In practical implementation, the real-time congestion value can be set first. With three congestion determination thresholds that increase sequentially , , Perform sequential comparison: when When the equipment is in full capacity, it is judged as a level one normal operating state, indicating that the section can be taken over at the normal pace.

[0143] when Furthermore, when the equipment is in full-capacity receiving state, it is determined to be in a level two slow-down receiving state, which means that it can continue to receive materials but needs to actively slow down the incoming materials;

[0144] when When the equipment status changes to reduced capacity acceptance, it is determined to be a level 3 congestion prevention state, which indicates that the real-time congestion value is in the level 3 limit range. The system triggers the upstream feed restriction command and sets the downstream front buffer segment as an independent speed limit queue control object.

[0145] when If the equipment status is prohibited from feeding in, it is judged as a level four shutdown and blockage relief state, indicating that it is not advisable to continue feeding in and the clearing should be the main focus. This implementation method does not trigger strong actions only after congestion occurs, but divides the section operation into four levels, so that the control actions can be tightened step by step according to the status. This can reduce the oscillation of the entire line caused by local short-term fluctuations.

[0146] This implementation method can determine the operational level based on both real-time congestion values ​​and equipment capacity status, avoiding biased control decisions based on only a single indicator.

[0147] In step S5, when the operating level is Level 2 speed reduction reception state or Level 3 congestion prevention state, the specific steps include:

[0148] S51. If it is determined to be a level 2 speed reduction receiving state, a control action command to reduce the transmission speed is sent to the frequency converters of each section of the target production line, and a delayed material receiving confirmation signal is broadcast to the adjacent upstream section so that the adjacent upstream section can use the nearby buffer section for buffering and temporary storage.

[0149] S52. If the situation is determined to be a Level 3 congestion prevention state, the downstream station buffer section will be switched to a separate speed-limiting queue, and a delayed release synchronization signal will be written to the adjacent upstream section to implement upstream supply slowdown feeding.

[0150] S53. For workpieces of the vulnerable type transported under Level 3 congestion prevention conditions, issue specific acceleration / deceleration commands with extended acceleration / deceleration times.

[0151] The implementation of steps S51 to S53 is explained in detail: the determination result of the secondary speed reduction reception state or the tertiary congestion prevention state is obtained, and control action instructions and synchronous linkage signals are generated according to the operation level and written into the execution layer instruction buffer and the adjacent segment status register; wherein, the synchronous linkage signal is not an additional prompt information, but a control bit used to trigger the action change of the adjacent segment.

[0152] The delayed receiving confirmation signal is used to notify the upstream section that the current section can still receive materials but the receiving capacity has decreased. The delayed release synchronization signal is used to notify the upstream section to actively slow down the release. The separate speed limit queue refers to the use of speed limit rules for the buffer section before the downstream station, which are independent of the ordinary conveying section, in order to reduce the speed at which the workpiece in this section continues to be compressed towards the front of the station.

[0153] If the receiving state is determined to be at level 2 speed reduction, a control action command to reduce the transmission speed is sent to the frequency converters of each section of the target production line, and a delayed material receiving confirmation signal is broadcast to the adjacent upstream section so that the adjacent upstream section can use the nearby buffer section for buffering and temporary storage.

[0154] Among them, the instruction to reduce transmission speed control action, which includes the new target speed value and the corresponding speed refresh enable bit, is written into the inverter control register;

[0155] The delayed material receiving confirmation signal can be written into the shared status bit of the adjacent upstream section, so that the upstream section selects the nearest buffer section for temporary storage in the current cycle, instead of continuously advancing to the main feed path of that section; this implementation method still maintains continuous conveying in the secondary state, but absorbs short-term fluctuations by slowing down and temporary storage in the nearest buffer.

[0156] This implementation method can achieve gentle adjustment when the material receiving capacity decreases but before serious congestion occurs, thus avoiding unnecessary line stoppages;

[0157] If the situation is determined to be a Level 3 congestion prevention state, the downstream workstation buffer section will be switched to a separate speed-limiting queue, and a delayed release synchronization signal will be written to the adjacent upstream section to implement the upstream supply slowdown feeding.

[0158] Among them, the separate speed limit queue refers to separating the speed control parameters corresponding to the downstream workstation buffer section from the ordinary queue, using a lower speed limit value and restricted speed increase rules; after the delayed release synchronization signal is written into the status register of the adjacent upstream section, the upstream section reduces the supply speed or delays the release cycle in the release logic of this section.

[0159] This synchronous linkage mechanism synchronously adjusts the front-end buffer conveying speed and upstream release rhythm of the workstation. By calling the front-end buffer and reducing the upstream feeding rate, it controls the workpiece stacking density and suppresses the evolution of the real-time congestion value to the fourth-level shutdown and congestion relief state.

[0160] For workpieces of the vulnerable type transported in the three-level congestion prevention state, a specific acceleration and deceleration command with extended acceleration and deceleration time is issued; the purpose of extending the acceleration and deceleration time is to reduce the impact of vulnerable workpieces when switching speeds and avoid collisions or unstable posture during low-speed protection and readjustment.

[0161] This specific acceleration / deceleration command can be written into the inverter parameter buffer along with the speed limit command in the third-level state, and refreshed according to the vulnerable type template when executed in the current segment; this implementation method continues to bring the workpiece type into the third-level action execution, so that vulnerable workpieces can get more suitable conveying parameters during congestion prevention.

[0162] This implementation method can balance conveying safety and cycle time control during the quasi-congestion protection phase, preventing damage to fragile workpieces due to excessively rapid speed changes.

[0163] In this embodiment of the invention, the method further includes the following steps:

[0164] S61. Calculate the load change rate of each section of the target production line within a preset time window based on the driver feedback parameters. When the load change rate is greater than the preset jump threshold, ignore the aforementioned control action command generated based on the real-time congestion value and force the pre-start control to be executed.

[0165] S62. Issue intermediate frequency preparation instructions to the frequency converters in each section of the target production line, release the brake structure in advance, and zero-correct the occupancy count data, while opening a short-time high-frequency sampling window;

[0166] S63. If the system is determined to be in a level 4 shutdown and blockage clearance state, the bidirectional blockage clearance mechanism is triggered, the input terminal of the adjacent upstream section is locked, a low-speed jog mode enable command is sent to the frequency converter, and only the movement command in the blockage clearance direction is retained.

[0167] The implementation methods of steps S61 to S63 are explained in detail; the driver feedback parameters are obtained, and the load change rate of each section of the target production line is calculated based on the changes within the preset time window;

[0168] When the load change rate, which characterizes how fast the driving load changes within a short window, exceeds a preset jump threshold, the aforementioned control action command generated based on the real-time congestion value is ignored, and pre-start control is forcibly executed.

[0169] A preset jump threshold is used to define the range of abnormal load changes. When the load change rate exceeds this range, the actuator is in an unsteady state constrained by mechanical inertia and brake release. The system disables the adjustment mechanism based on the conventional real-time congestion value and directly executes the forced overwrite command.

[0170] In one implementation, the load characterization at the beginning of the window is obtained by deriving the torque utilization rate from the driver feedback parameters. and the load representation at the end of the window You can press Alternatively, the load change rate can be calculated using an equivalent method;

[0171] This implementation method employs forced coverage in special abrupt change scenarios, allowing the actuator to first enter a ready state suitable for subsequent actions; this implementation method can handle mechanical preparation issues in advance when the load changes abruptly, reducing execution instability caused by direct control switching;

[0172] When the forced pre-start control is triggered, an intermediate frequency preparation instruction is sent to the inverters in each section of the target production line to release the brake structure in advance, and the buffer section occupancy counter is zeroed and corrected. At the same time, a short-time high-frequency sampling window is opened.

[0173] Among them, the intermediate frequency preparation command refers to the transition speed command between the stop state and the normal operating frequency, which is used to put the drive system into a preparation state that can respond quickly; the early release brake structure is used to reduce mechanical drag during subsequent actual start-up.

[0174] The buffer occupancy counter zeroing correction is used to eliminate counting errors that may accumulate during special switching processes; the short-time high-frequency sampling window is used to increase the observation density of changes in speed, occupancy, and drive feedback during the transition phase;

[0175] In practice, this pre-start control can be implemented by writing to the inverter's target frequency register, brake control bit, and counter reset bit. The high-frequency sampling window can be implemented by temporarily shortening the sampling interval or increasing the sampling call frequency. After the forced coverage phase is completed, the system returns to the normal control cycle.

[0176] This implementation method enables the actuator to have a more stable mechanical state before entering subsequent actions, and brings the cache statistics back to a reliable range.

[0177] If the system is determined to be in a level 4 shutdown and blockage clearance state, the bidirectional blockage clearance mechanism is triggered, the input terminal of the adjacent upstream section is locked, a low-speed jog mode enable command is sent to the frequency converter, and only the movement command in the blockage clearance direction is retained.

[0178] Among them, the two-way deblocking mechanism refers to stopping new upstream input while retaining downstream release and necessary deblocking direction movement capabilities; the input end of the adjacent upstream section is blocked to prevent new workpieces from continuing to enter the congested section; the low-speed jog mode enable command is used to allow the section to discharge the backlog of workpieces in a low-speed, controlled short-stroke manner.

[0179] Retaining only the movement command in the direction of clearing blockage means that movement commands in the opposite direction or not required for clearing blockage will no longer be executed, in order to prevent the congestion from worsening; this implementation method does not simply stop the machine in the fourth state, but retains the movement capability that is conducive to clearing blockage, so that the blockage can be gradually cleared.

[0180] This implementation method can shift the control focus to stopping further inflows and retaining outflows during severe congestion, thereby reducing the continued expansion of the congestion.

[0181] The method also includes the following steps:

[0182] S71. Obtain the instantaneous current data from the driver feedback parameters. If the instantaneous current data is greater than the preset current spike threshold and the encoder speed data is less than the preset speed loss threshold, skip the calculation of the real-time congestion value, directly determine it as a mechanical impact event, and block the issuance of the entire line shutdown command.

[0183] S72. When the real-time congestion value drops and the operating level is downgraded from Level 3 congestion prevention state or Level 4 shutdown and congestion relief state to Level 2 speed reduction receiving state or Level 1 normal operation state, execute a three-stage progressive recovery action to update the target speed command in the control action command.

[0184] S73. If the real-time congestion value is less than the second congestion judgment threshold and decreases for a consecutive preset number of sampling cycles, then the target speed command is set to 60% of the preset baseline process speed;

[0185] S74. If the variance of the cycle completion time of a downstream station for a consecutive preset number of cycles is less than the set steady-state threshold, then the target speed command is set to 80% of the baseline process speed;

[0186] S75. If the response delay value is less than the tolerance threshold and there is no jump in the photoelectric occupancy signal, then set the target speed command to 100% of the reference process speed.

[0187] The implementation of steps S71 to S75 is explained in detail: instantaneous current data and encoder speed data in the driver feedback parameters are obtained, and abnormal event judgment is performed based on the current spike threshold used to filter abnormal peak current and the speed loss threshold used to determine that the encoder speed is lower than the set working lower limit.

[0188] If the instantaneous current data is greater than the preset current spike threshold and the encoder speed data is less than the preset speed loss threshold, the calculation of the real-time congestion value is skipped, and it is directly judged as a mechanical impact event, thus blocking the issuance of the entire line shutdown command.

[0189] Among them, mechanical impact events refer to short-term anomalies caused by instantaneous collisions, brief jams, or structural vibrations, rather than continuous congestion;

[0190] The system performs event type determination by synchronously comparing instantaneous current data and encoder speed data. If the above threshold conditions are met, it is marked as a non-continuous short-distance impact, thereby blocking the output of the full-line shutdown command and maintaining the normal working mode.

[0191] When the real-time congestion value drops and the operating level is downgraded from Level 3 congestion prevention state or Level 4 shutdown and congestion relief state to Level 2 speed reduction and reception state or Level 1 normal operation state, a three-stage progressive recovery action is executed to update the target speed command in the control action command.

[0192] The three-stage progressive recovery process does not restore the process speed to the baseline all at once. Instead, it first verifies whether the congestion continues to decrease, then confirms whether the downstream workstations are stable, and then confirms whether the instruction execution has returned to normal. In order to avoid mutual interference or conflict between the judgment conditions of each stage during the fluctuation period, the recovery process is based on the management of a constrained state machine in the actual implementation. It is only allowed to flow to the judgment of stage two after the stage one condition is strictly met and the output speed is running stably at 60%.

[0193] Similarly, only after the output speed of stage two is 80% and the status is confirmed, the speed judgment of stage three is unlocked, thereby preventing acceleration beyond the stage. This three-stage gradual recovery mechanism suppresses the secondary material accumulation caused by the step speed jump by setting the target speed command in a step-by-step manner.

[0194] If the real-time congestion value is less than the second congestion judgment threshold and decreases for a preset number of consecutive sampling cycles, the target speed command will be set to 60% of the preset baseline process speed.

[0195] Among them, the continuous preset number of sampling cycles decrease is used to confirm that the congestion value is not a single jitter and drop, but a continuous downward trend; 60% corresponds to the verification recovery speed of recovery segment 1, which is used to observe the changes in buffer and workstation at a more conservative speed; this implementation method gives a lower recovery speed in the initial recovery segment to prevent the high cycle time from being returned immediately after the congestion is relieved.

[0196] If the variance of the cycle completion time of the downstream station for a number of consecutive preset cycles is less than the set steady-state threshold, then the target speed command will be set to 80% of the baseline process speed.

[0197] Among them, the variance of the cycle completion time is less than the steady-state threshold, which means that the cycle time of the downstream station has stabilized again. Eighty percent corresponds to the steady-state confirmation speed of recovery section 2, which is used to continue to observe under conditions that are closer to normal production.

[0198] This implementation adds a check on the cycle stability of the downstream workstation, so that the recovery action is simultaneously constrained by two conditions: the section is not blocked and the workstation is stable. This implementation can confirm that the downstream workstation has indeed recovered and stabilized in the middle of the recovery process, reducing repeated speed increases and decreases.

[0199] If the response delay value is less than the tolerance threshold and there is no jump in the photoelectric occupancy signal, the target speed command is set to 100% of the baseline process speed; where the response delay value is less than the tolerance threshold, it means that the hysteresis between the command and the execution feedback has been restored to the allowable range.

[0200] The absence of a jump in the photoelectric occupancy signal indicates that there has been no abnormal interruption or unstable change in occupancy detection; both together indicate that the actuator, detection signal, and conveying status have returned to relatively stable conditions and can be restored to the reference process speed.

[0201] This implementation method can complete the full recovery based on the execution response and occupancy stability at the end of the recovery phase, avoiding premature recovery to full speed before the execution lag has been eliminated.

[0202] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for real-time control of production line transmission speed based on digital twins, characterized in that, include: S1. Acquire encoder speed data, photoelectric occupancy signals, workstation completion signals, driver feedback parameters, work-in-process label information, and real-time occupancy data and occupancy count data of the target buffer section for each section of the target production line; S2. Call the digital twin model to map and reorganize the encoder speed data, photoelectric occupancy signal, station completion signal, driver feedback parameters and work-in-process label information to generate a group of operating status information containing station receiving status, workpiece conveying type, equipment status and response delay value; S3. Determine the target safety distance according to the workpiece conveying type; take the ratio of the occupancy time of the photoelectric occupancy signal to the preset statistical period as the static space occupancy ratio; obtain the material arrival rate and release rate from the number of times the workstation completes the signal trigger within the preset time window, and take the difference between the two and divide it by the release rate to obtain the cycle time difference rate; The spacing compression ratio is calculated from the encoder speed data and the target safety distance; the static space occupancy ratio, spacing compression ratio and beat difference rate are weighted and summed with preset static space occupancy weight, spacing compression weight and beat difference weight respectively to obtain the real-time congestion value; S4. Based on the real-time congestion value, workstation material receiving status and equipment status, a threshold comparison is performed to determine the current operating level of each section of the target production line; S5. Generate control action commands according to the operating level and output them to the actuators of each section, including frequency converters, servo motors and brake structures, to adjust the transmission speed.

2. The real-time control method for production line transmission speed based on digital twin as described in claim 1, characterized in that, The step S2 of generating the running status information group specifically includes: S21. Calculate the time difference of the station completion signal within adjacent cycles to obtain the cycle completion time, and calculate the variance of the cycle completion time. Compare the variance of the cycle completion time with a preset variance threshold. If it is less than the preset variance threshold, a normal material receiving station receiving state is generated; if it is greater than or equal to the preset variance threshold, a delayed material receiving station receiving state is generated. S22. Parse the product feature code in the work-in-process label information, and classify it into vulnerable type, inertia type or ordinary type according to the preset mapping relationship between feature code and conveying type, and generate workpiece conveying type; S23. The torque utilization rate and following error in the driver feedback parameters are compared with the preset torque threshold and error threshold respectively. If both are less than the corresponding threshold, a full-capacity equipment state is generated. If either is greater than or equal to the corresponding threshold and less than the limit threshold, a derated equipment state is generated. If either is greater than or equal to the limit threshold, a prohibited equipment state is generated. The limit threshold is greater than the corresponding threshold. S24. Obtain the speed command issuance time of the previous control cycle, and calculate the difference between the speed command issuance time of the previous control cycle and the encoder speed data feedback time of the current cycle to generate a response delay value characterizing the hysteresis relationship.

3. The real-time control method for production line transmission speed based on digital twin as described in claim 2, characterized in that, The calculation of the real-time congestion value in step S3 specifically includes: S31. Obtain historical steady-state operation data of each section of the target production line, and use constrained least squares method for fitting and updating to generate initial static space occupancy weight, spacing compression weight and cycle time difference weight; S32. If the workpiece conveying type is inertia type, then a preset first spacing compensation value is added to the initial spacing compression weight to obtain the corrected spacing compression weight. S33. Calculate the physical cache balance of the target cache segment based on the real-time occupancy data and the preset total cache capacity. If the physical cache balance is greater than the preset length threshold, add a preset second space compensation value to the initial static space occupancy weight to obtain the corrected static space occupancy weight. If the physical cache balance is not greater than the preset length threshold, use the initial static space occupancy weight directly as the corrected static space occupancy weight. S34. Multiply the corrected static space occupancy weight, the corrected spacing compression weight, and the initial beat difference weight by the static space occupancy ratio, the spacing compression rate, and the beat difference rate, respectively, and sum them up to obtain the corrected real-time congestion value.

4. The real-time control method for production line transmission speed based on digital twin according to claim 2, characterized in that, The calculation of the spacing compression ratio in step S3 specifically includes: S301. Integrate the encoder speed data linearly within a continuous sampling period, and calculate the physical distance between adjacent workpieces by combining the triggering timing of the photoelectric occupancy signal. S302. Determine the type of workpiece conveying. If it is an inertia type, set the target safety distance to a first safety distance threshold. If it is a normal type, set the target safety distance to a second safety distance threshold. If it is a fragile type, set the target safety distance to a third safety distance threshold. The third safety distance threshold is greater than the first safety distance threshold, and the first safety distance threshold is greater than the second safety distance threshold. S303. Determine whether the physical distance value is less than the target safety distance; if yes, calculate the ratio of the physical distance value to the target safety distance, and take the difference between the physical distance value and the target safety distance as the distance compression ratio; if no, set the distance compression ratio to zero.

5. The real-time control method for production line transmission speed based on digital twin according to claim 2, characterized in that, The step S4, determining the current operating level of each section of the target production line, specifically includes: S41. Compare the real-time congestion value with the system's preset first congestion determination threshold, second congestion determination threshold, and third congestion determination threshold, wherein the first congestion determination threshold, second congestion determination threshold, and third congestion determination threshold increase sequentially. S42. If the real-time congestion value is less than the first congestion determination threshold, and the equipment status is full capacity, then it is determined to be a level one normal operation status. S43. If the real-time congestion value is greater than or equal to the first congestion determination threshold and less than the second congestion determination threshold, and the device status is full-capacity acceptance, then it is determined to be a level 2 slow-down reception state. S44. If the real-time congestion value is greater than or equal to the second congestion determination threshold and less than the third congestion determination threshold, or if the equipment status is downgraded to reduced capacity acceptance, then it is determined to be a level three congestion prevention state. S45. If the real-time congestion value is greater than or equal to the third congestion determination threshold, or if the equipment status is prohibited from receiving, then it is determined to be a level four shutdown and congestion relief state.

6. The real-time control method for production line transmission speed based on digital twin as described in claim 5, characterized in that, In step S5, when the operating level is a level 2 slowdown reception state or a level 3 congestion prevention state, the specific steps include: S51. If the secondary speed reduction receiving state is determined, a control action command to reduce the transmission speed is sent to the frequency converters of each section of the target production line, and a delayed material receiving confirmation signal is broadcast to the adjacent upstream section so that the adjacent upstream section can use the adjacent buffer section for buffering and temporary storage. S52. If the situation is determined to be the three-level congestion prevention state, the downstream station buffer section is switched to a separate speed-limiting queue, and a delayed release synchronization signal is written to the adjacent upstream section to implement upstream supply slowdown feeding. S53. For workpieces of the fragile type transported in the three-level congestion prevention state, issue a specific acceleration / deceleration command with extended acceleration / deceleration time.

7. The real-time control method for production line transmission speed based on digital twin as described in claim 5, characterized in that, The method further includes the following steps: S61. Calculate the load change rate of each section of the target production line within a preset time window based on the driver feedback parameters. When the load change rate is greater than the preset jump threshold, ignore the control action command generated based on the real-time congestion value and force the pre-start control to be executed. S62. Issue an intermediate frequency preparation instruction to the frequency converters of each section of the target production line, release the brake structure in advance, and perform zero correction on the occupancy count data, while opening a short-time high-frequency sampling window; S63. If the system is determined to be in the fourth-level shutdown and blockage relief state, the bidirectional blockage relief mechanism is triggered, the input terminal of the adjacent upstream section is locked, a low-speed jog mode enable command is sent to the inverter, and only the movement command in the blockage relief direction is retained.

8. The real-time control method for production line transmission speed based on digital twin as described in claim 5, characterized in that, The method further includes the following steps: S71. Obtain the instantaneous current data in the driver feedback parameters. If the instantaneous current data is greater than the preset current spike threshold and the encoder speed data is less than the preset speed loss threshold, skip the calculation of the real-time congestion value, directly determine it as a mechanical impact event, and block the issuance of the entire line shutdown command. S72. When the real-time congestion value drops and the operating level is downgraded from Level 3 congestion prevention state or Level 4 shutdown and congestion relief state to Level 2 speed reduction reception state or Level 1 normal operation state, a three-stage progressive recovery action is executed to update the target speed command in the control action command. S73. If the real-time congestion value is less than the second congestion determination threshold and decreases for a consecutive preset number of sampling periods, then the target speed command is set to 60% of the preset baseline process speed; S74. If the variance of the cycle completion time of a downstream station for a consecutive preset number of cycles is less than a set steady-state threshold, then the target speed command is set to 80% of the baseline process speed; S75. If the response delay value is less than the tolerance threshold and the photoelectric occupancy signal has no jump, then the target speed command is set to 100% of the reference process speed.

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