Buffering and limiting control method and system for servo bending machine

Abstract

This application relates to the field of industrial automatic control technology and discloses a buffer limit control method and system for a servo bending machine. The invention acquires bilateral operational observation information during the approach process of the bending terminal, generates bilateral target limit references using a side-by-side limit reference fusion method, and forms bilateral terminal approach observation results. Based on these results, a terminal approach stage label is generated to identify the state where one side limit reaches the limit first. Furthermore, left and right position synchronization residuals, bilateral equivalent load differences, equivalent relative displacement of the crossbeam, and position load consistency residuals are generated to produce the crossbeam torsional conflict state and synchronization deviation source results. Then, based on the synchronization deviation source results and the crossbeam torsional conflict state, a compensation gating result is generated to restrict the bilateral synchronous catching-up compensation action and execute differentiated buffer limit control. This method can reduce the risks of unilateral approach, crossbeam torsion, and terminal load impact, and improve the control stability of the bending terminal.

Description

Technical Field

[0001] This application relates to the field of industrial automatic control technology, and in particular to a buffer limit control method and system for a servo bending machine. Background Technology

[0002] Servo bending machines are widely used in sheet metal forming. They typically use a CNC system to control the left and right servo axes to synchronously drive the slider downwards, completing the bending of the sheet metal through the cooperation of the upper and lower dies. In long plate bending, offset workpiece bending, continuous processing of multiple batches of sheet metal, and small-batch multi-specification production, differences in sheet metal placement, material thickness distribution, die wear, guide rail friction, and the stiffness of the left and right transmission chains can cause the slider ends to experience different motion resistance and bending loads as they approach the bending end. For example, if one end of the sheet metal contacts the die first or there is slight wear in the lower die groove on one side, although the left and right servo axes execute downward control according to the same target position, differences will occur in the remaining limit distance, torque growth trend, and pressure build-up process on both sides. Since the bending end stage simultaneously involves deceleration, bending, pressure holding, and limit confirmation, the control system needs to complete synchronous adjustment and limit protection within a short stroke. Premature approach to the limit on either side or abnormal local force can be amplified into beam posture deviation, local die impact, and bending angle deviation.

[0003] Existing servo bending machines typically employ control methods such as left and right axis position synchronization, master-slave axis following control, fixed buffer distance deceleration, soft limit protection, overload alarm, and left and right pressure or current difference monitoring. While these methods can meet the synchronous operation and end-point protection requirements of conventional bending processes, their judgment criteria are mostly concentrated on left and right position differences, speed differences, or single limit thresholds, lacking a combined assessment of the degree of proximity of left and right limits, the trend of synchronization error changes, left and right torque differences, pressure distribution differences, and the torsional state of the crossbeam. In actual end-point approach processes, left and right position differences may originate from normal off-center loading, from one side entering the limit risk zone first, or from the elastic torsion of the crossbeam or frame. Especially when the crossbeam experiences slight torsion, the feedback positions of the left and right encoders may still be within the allowable synchronization error range, while the actual bending line experiences significantly uneven stress. If compensation is continued based on position differences, the side that reaches the limit first may continue to be pressured, forcing the side that hasn't reached the limit to follow and correct, leading to single-sided die collisions, prolonged torsion of the crossbeam, overpressure on one end of the workpiece and underpressure on the other, and misjudgments by safety protection mechanisms. Therefore, the existing control method still needs to be improved to adapt to the differentiated buffer limit control requirements of the dual-sided servo axes at the bending end stage. Summary of the Invention

[0004] This application proposes a buffer limit control method and system for a servo bending machine to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this application adopts the following technical solution: a servo bending machine buffer limit control method, comprising: S1, acquire bilateral running observation information during the approach of the bending terminal, correct and generate bilateral target limit references by using the side limit reference fusion method, convert the actual positions of both sides into the left limit remaining distance and the right limit remaining distance in the unified downlink coordinate, collect the speed attenuation, load establishment and position following changes of both sides, form the single-sided terminal approach description quantity and the bilateral difference description quantity, and generate bilateral terminal approach observation results. S2, based on the bilateral terminal approach observation results, generate terminal approach stage labels for the left and right servo axes, and form bilateral stage difference quantities from the bilateral terminal approach stage labels, and identify the unilateral limit arrival state by combining the bilateral difference description quantities. S3, based on the first arrival state of the single-sided limit and the observation results of the approach of the double-sided terminal, subtract the left and right command position difference from the actual left and right position difference to form the left and right position synchronization residual, form the double-sided equivalent load difference from the load state of both sides, convert the double-sided equivalent load difference into the equivalent relative displacement of the beam through the beam stiffness calibration data, and form the position load consistency residual from the equivalent relative displacement of the beam and the left and right position synchronization residual, generating the torsional conflict state of the beam and the result of the synchronization deviation source; S4 generates compensation gating results based on the synchronous deviation source results and the torsional conflict state of the crossbeam. It uses the compensation gating results to limit the synchronous leveling compensation actions on both sides, executes differentiated buffer limit control, and outputs differentiated buffer limit control results.

[0006] Furthermore, the specific operation of correcting and generating target limit references on both sides using the side limit reference fusion method is as follows: the left servo axis and the right servo axis are treated as independent limit objects. Based on the equipment calibration record, bending program and safety limit rules, the equipment calibration offset, program target offset and terminal safety reserve on both sides are uniformly merged downlink coordinates. Then, the merged side offsets are fused to the target limit references on the corresponding sides, so that the left target limit reference and the right target limit reference correspond to the terminal limit constraints of the left servo axis and the right servo axis, respectively. Subsequently, the actual position of the left servo axis and the actual position of the right servo axis are mapped to the corresponding target limit references to obtain the remaining distance of the left limit and the remaining distance of the right limit.

[0007] Further, the specific operation for generating the bilateral terminal proximity observation results is as follows: The starting distance for terminal observation is determined based on the set buffer distance and set bending speed recorded in the bending program record, and the rated deceleration of the servo axis recorded in the equipment calibration record. After the remaining distance of the limit switch on either side enters the starting distance for terminal observation, the terminal observation window is activated. Within the terminal observation window, a left-side single-sided terminal proximity description quantity and a right-side single-sided terminal proximity description quantity are generated. The single-sided terminal proximity description quantity is formed by the convergence state, velocity decay state, load establishment state, and position following change state of the corresponding side limit switch remaining distance. The left-side single-sided terminal proximity description quantity and the right-side single-sided terminal proximity description quantity are then differentially aggregated to form a bilateral differential description quantity. Finally, the left-side single-sided terminal proximity description quantity, the right-side single-sided terminal proximity description quantity, and the bilateral differential description quantity are all included in the bilateral terminal proximity observation results.

[0008] Furthermore, the specific operation for generating terminal approach stage labels for the left and right servo axes is as follows: According to the progressive relationship of the terminal approach process from the regular synchronous approach stage, the buffer limit approach stage, to the limit confirmation stage, a stage determination chain is established for the left and right servo axes respectively; when the corresponding side does not meet the buffer approach determination condition, a regular synchronous approach stage label is assigned; when the remaining limit distance on the corresponding side continues to converge, and the speed decay state and load establishment state meet the buffer establishment condition, a buffer limit approach stage label is assigned. The buffer establishment condition is jointly determined by the buffer approach reference, the speed decay reference, the load establishment reference, and the continuous establishment time reference; when the corresponding side approaches the corresponding target limit reference, the speed converges to the limit confirmation range, and the load change enters the limit confirmation fluctuation range, a limit confirmation stage label is assigned.

[0009] Furthermore, the specific operation for identifying the first-arrival state of a single-sided limit switch is as follows: Based on the terminal approach stage labels of the left and right servo axes, a bilateral stage difference is formed, and the side in the later progressive stage is identified as the candidate first-arrival side, while the other side is identified as the candidate non-arrival side. Between the candidate first-arrival side and the candidate non-arrival side, the limit approach difference, speed decay difference, load establishment difference, and position following change difference are continuously sampled within the same direction for verification. When the candidate first-arrival side arrives first in the terminal approach stage, and the limit approach difference, speed decay difference, load establishment difference, and position following change difference meet the first-arrival condition, a single-sided limit switch first-arrival state is generated. The single-sided limit switch first-arrival state includes the first-arrival side identifier, the non-arrival side identifier, the bilateral stage difference, and the state duration.

[0010] Furthermore, the specific operations for forming the left and right position synchronization residuals and the bilateral equivalent load difference are as follows: the difference between the actual position of the left servo axis and the actual position of the right servo axis is subtracted from the difference between the commanded position of the left servo axis and the commanded position of the right servo axis to obtain the left and right position synchronization residuals, so that the differences in the command reference of the two sides, the zero-point calibration difference, and the process compensation difference do not participate in the judgment of the torsional conflict of the crossbeam; at the same time, the load state of the left side and the load state of the right side are converted into the equivalent load of the left side and the equivalent load of the right side under the same mechanical scale; when the independent load sensor and the servo torque feedback exist at the same time, the equivalent load of the corresponding side is formed according to the fusion weight determined by the standard load test record or the sensor calibration record, thereby obtaining the bilateral equivalent load difference used to characterize the uneven force on the left and right sides.

[0011] Further, the specific operations for generating the torsional conflict state and synchronous deviation source results of the crossbeam are as follows: Based on the current slider height, mold installation position, and bending length setting, the current differential stiffness of the crossbeam is obtained by selecting or interpolating from the crossbeam stiffness calibration data, and the difference between the two sides of the equivalent load is converted into the equivalent relative displacement of the crossbeam; the equivalent relative displacement of the crossbeam and the left and right position synchronous residuals are used to determine the position load consistency residual; when the left and right position synchronous residuals are within the allowable range of synchronous error, the difference between the two sides of the equivalent load exceeds the current working condition baseline difference, and the position load consistency residual reaches the residual establishment benchmark, the torsional conflict state of the crossbeam is generated. The current working condition baseline difference is formed by the historical qualified bending records of the same type. When the historical records are insufficient, they are formed by the standard specimen off-center bending test records, the no-load synchronous downward test records, or the equipment factory calibration records; combined with the state of the unilateral limit arriving first, the synchronous deviation source results are classified into normal off-center load synchronous difference, unilateral limit arriving first, crossbeam torsional conflict state, or composite source.

[0012] Furthermore, the specific operations for generating compensation gating results are as follows: the synchronization deviation source result is converted into a gating constraint on the synchronous catching-up compensation action on both sides; when the synchronization deviation source result is a normal off-center load synchronization difference, the predetermined range of action of the synchronous catching-up compensation action on both sides is maintained; when the synchronization deviation source result is that the limit on one side arrives first, a convergence gating is applied to the compensation trend of the first-arriving side towards the target limit, and the following action of the non-arriving side is jointly constrained by the remaining distance of the limit on the non-arriving side and the upper limit of the terminal buffer speed; when the synchronization deviation source result is a crossbeam under torsional conflict state, the action ratio of the synchronous catching-up compensation action on both sides is converged and corrected, and the common downward speed of both sides is converged synchronously; when the synchronization deviation source result is a composite source, the crossbeam under torsional conflict state is taken as the priority constraint in the compensation gating result.

[0013] Furthermore, the specific operation of differential buffer limit control is as follows: Within the speed control domain, the final speed commands for the left and right servo axes are generated. These final speed commands are jointly determined by the basic buffer speed, the synchronous speed correction amount limited by the compensation gating result, and the torsional conflict speed correction amount formed based on the torsional conflict state of the crossbeam. In the state where a single-sided limit is reached first, the downward approach speed of the first-reaching side converges according to the compensation gating result, while the non-reaching side approaches the corresponding target limit reference at a speed not exceeding the upper limit of the terminal buffer speed. In the state of torsional conflict of the crossbeam, the high-load side and low-load side are determined based on the equivalent load difference between the two sides. The continued approach trend of the high-load side is converged and corrected, and the low-load side follows within the upper limit of the terminal buffer speed. When the remaining limit distance on either side is less than the limit confirmation retention distance, the speed command in the direction of the target limit on that side is set to zero and the limit holding state is entered.

[0014] A servo bending machine buffer limit control system includes: The terminal observation construction module acquires bilateral operation observation information during the approach process of the bending terminal, corrects and generates bilateral target limit references by using the side limit reference fusion method, converts the actual positions of both sides into the left limit remaining distance and the right limit remaining distance in the unified downlink coordinate, collects the velocity attenuation, load establishment and position following changes of both sides, forms the single-sided terminal approach descriptive quantity and the bilateral difference descriptive quantity, and generates bilateral terminal approach observation results. The single-sided first-arrival recognition module generates terminal approach stage labels for the left and right servo axes based on the observation results of the two-sided terminal approach. The two-sided stage difference quantity is formed by the two-sided terminal approach stage labels and combined with the two-sided difference description quantity to identify the single-sided limit first-arrival state. The synchronization deviation source explanation module, based on the single-sided limit arrival state and the observation results of the double-sided terminal approach, subtracts the left and right command position difference from the actual left and right position difference to form the left and right position synchronization residual, and forms the double-sided equivalent load difference from the load state of both sides. The double-sided equivalent load difference is converted into the equivalent relative displacement of the beam through the beam stiffness calibration data, and the position load consistency residual is formed by the equivalent relative displacement of the beam and the left and right position synchronization residual, generating the torsional conflict state of the beam and the synchronization deviation source result; The compensation gating control module generates compensation gating results based on the source of synchronization deviation and the torsional conflict state of the crossbeam. It uses the compensation gating results to limit the synchronous leveling compensation action on both sides, executes differentiated buffer limit control, and outputs differentiated buffer limit control results.

[0015] The beneficial effects of this invention are as follows: 1. This invention acquires bilateral operational observation information during the approach of the bending terminal and generates target limit references on both sides using a side-by-side limit reference fusion method. This allows the zero-point calibration differences, process compensation differences, and terminal safety reserve differences between the left and right servo axes to be incorporated into the corresponding side limit references. Then, the remaining distances of the left and right limit references are formed in a unified downlink coordinate system. This process enables the approach states of the two terminals to be compared within the same coordinate scale and the same observation window, avoiding misjudging the differences in the side-by-side target limit references as synchronization anomalies. It also provides a consistent data foundation for subsequent terminal approach stage label determination, single-side limit arrival state identification, and crossbeam torsional conflict state identification.

[0016] 2. This invention generates terminal approach stage labels for the left and right servo axes based on bilateral terminal approach observation results. It also identifies the state where the unilateral limit is reached first by combining bilateral stage difference and bilateral difference description. This enables the system to distinguish between normal synchronous approach, unilateral early entry into the buffer limit area, and misalignment of the terminal stages on both sides. Subsequently, this invention generates left and right position synchronization residuals by subtracting the left and right command position difference from the actual left and right position difference. It then generates the torsional conflict state of the beam by combining the bilateral equivalent load difference, beam stiffness calibration data, and position load consistency residuals. This enables the control system to identify the hidden torsional state where the left and right position synchronization residuals are still within the allowable range but the load imbalance cannot be explained by the position synchronization residuals. This avoids the risk of beam torsion being missed due to relying solely on the left and right position difference for synchronization judgment.

[0017] 3. This invention generates compensation gating results based on the synchronous deviation source and the torsional conflict state of the crossbeam, and uses these results to restrict the synchronous leveling compensation actions on both sides. This allows the terminal buffer limit control to perform differentiated control based on normal off-center load synchronous difference, first arrival of the single-sided limit, torsional conflict state of the crossbeam, and combined sources. In the scenario where the single-sided limit arrives first, the first-arriving side is gating-restricted, while the non-arriving side approaches the corresponding target limit reference according to the following coefficient. In the scenario of torsional conflict of the crossbeam, the synchronous leveling compensation action is restricted, the tendency of the high-load side to approach is constrained, and the low-load side performs following correction within the upper limit of the terminal buffer speed. This process avoids forced leveling in the terminal area, which can cause single-sided approach, crossbeam torsion, and load impact, ensuring that the bending terminal limit process simultaneously considers synchronous control, buffer safety, and bending quality stability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort: Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a system framework diagram of the present invention. Detailed Implementation

[0019] 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.

[0020] Example 1 like Figure 1 As shown, this invention discloses a buffer limit control method for a servo bending machine, including the following specific steps: In one implementation, step S1 is used to acquire bilateral operation observation information of the servo bending machine during the bending terminal approach process, and organize the remaining limit state, speed decay state, load establishment state and position following change state of the left servo axis and the right servo axis into bilateral terminal approach observation results. The bilateral terminal approach observation results serve as the input for step S2 to determine the terminal approach stage label and identify the state where the single-sided limit arrives first, and serve as the data basis for subsequent interpretation of the source of synchronization deviation.

[0021] The dual-side operation observation information includes the actual position, actual speed, actual acceleration, servo torque, current feedback, load feedback, command position, bending program target position, bending process parameters, and crossbeam stiffness calibration data of the left and right servo axes during the bending terminal approach process. The bending process parameters include plate thickness, plate length, material type, die opening width, target bending angle, set bending speed, set buffer distance, set holding time, workpiece center offset relative to machine tool center, bending length, back gauge coordinates, and left and right support positions. The crossbeam stiffness calibration data is formed from the equipment factory calibration record, no-load synchronous downward test record, standard specimen off-center bending test record, or equipment maintenance calibration record. In step S1, it is used as constraint data output with the dual-side terminal approach observation results for subsequent identification of the crossbeam torsional conflict state.

[0022] Load feedback serves as input data for the load establishment state on the corresponding side. When the equipment is equipped with force sensors, pressure sensors, or strain sensors, the sensor output is converted into load feedback under the same mechanical scale based on the sensor calibration coefficient, effective pressure area, or strain-load calibration relationship. When the equipment is not equipped with an independent load sensor, the servo torque is converted into an equivalent vertical load based on the servo motor torque constant, transmission ratio, lead screw, and transmission efficiency, and the equivalent vertical load is used as load feedback. When both independent load sensors and servo torque feedback exist, the fusion weight is determined based on standard load test records or sensor calibration records. If historical records are insufficient, the conversion result of the independent load sensor is used as the master data, and the conversion result of the servo torque is used as the consistency verification data. The load feedback converted to the same mechanical scale participates in the formation of the load establishment state, the bilateral difference descriptor, and the subsequent bilateral equivalent load difference.

[0023] After acquiring the dual-side operational observation information, unified time base processing and unified downlink coordinate processing are performed. The interpolation cycle of the CNC system or the feedback cycle of the servo drive is used as the unified sampling cycle, with the dimension of the unified sampling cycle being time, preferably 1ms to 10ms. When the actual control cycle of the equipment is greater than 10ms, the minimum control cycle that the equipment can stably and synchronously acquire is used as the unified sampling cycle, and the number of sampling points in the continuous sampling window is determined according to this sampling cycle. When the feedback times of the left and right servo axes are inconsistent, interpolation is performed on the data between adjacent sampling points based on the target sampling time, so that the position, velocity, acceleration, torque, current, and load feedback on both sides correspond to the same sampling time. When the downward direction of the slider in the original coordinates of the equipment is the direction of decreasing position value, the downward direction of the slider is uniformly converted to the direction of increasing position value, and then the remaining limit distance and terminal approach state processing are performed. The output of this processing is the dual-side operational observation information under the same sampling time and the same downlink coordinate.

[0024] After unifying the time base, the observation information of both sides is used to perform data validity verification. If any sampling point has missing position data, current feedback exceeds the rated acquisition range of the driver, load feedback is lower than the sensor zero-point calibration lower limit, or the same sampling channel loses more than 3 consecutive sampling cycles, the corresponding sampling point will be marked as an invalid sampling point. The judgment rule for losing more than 3 consecutive sampling cycles is determined by communication frame loss records, equipment factory test records, or field debugging records. When the proportion of invalid sampling points in the terminal observation window exceeds the integrity limit, a low-confidence observation mark is written into the bilateral terminal proximity observation results of this bending cycle. The integrity limit represents the proportion of invalid sampling points to the total number of sampling points in the terminal observation window, preferably 5% to 10%, and its value is determined by equipment sampling stability verification records, communication frame loss records, or factory test records. When historical records are insufficient, the continuous sampling stability results during the equipment debugging stage are used to determine the value. The low-confidence observation mark serves as the triggering basis for subsequent steps to execute the security degradation path.

[0025] In the fusion processing of the side limit references, the left and right servo axes are treated as independent limit objects. For the left servo axis, the bending program target position, the left servo axis zero point calibration offset, the left end safety reserve, and the left limit confirmation retention amount are merged into a unified down-going coordinate system to form the left target limit reference. For the right servo axis, the bending program target position, the right servo axis zero point calibration offset, the right end safety reserve, and the right limit confirmation retention amount are merged into a unified down-going coordinate system to form the right target limit reference. The dimension of the end safety reserve is length, which is determined based on the equipment positioning accuracy, lead screw return clearance, die closure safety margin, and bending process specifications. The end safety reserve of conventional small and medium-sized servo bending machines is preferably 0.1mm to 1mm. The end safety reserve of long plate bending or large-tonnage bending equipment is determined based on the equipment debugging records and standard test piece bending verification records, and is preferably 0.5mm to 2mm. This end safety reserve is used to ensure that the target limit references on both sides avoid mechanical hard limits, die closure boundaries, and high-load end contact points.

[0026] After establishing target limit references on both sides, the actual position of the left servo axis is mapped to the left target limit reference in a unified downlink coordinate system to obtain the remaining distance of the left limit; the actual position of the right servo axis is mapped to the right target limit reference to obtain the remaining distance of the right limit. The dimensions of the remaining distances of the left and right limits are both lengths, expressed along the downlink direction of the slider, and used to characterize the remaining travel between the actual position on the corresponding side and the corresponding target limit reference. By establishing the remaining distances of the limits on both sides through the target limit references on both sides, the differences in zero-point calibration, process compensation, and terminal safety reserve on both sides are incorporated into their respective limit references, avoiding misjudging the differences in the two-side references as terminal synchronization anomalies.

[0027] When the remaining distance of the limit switch on either side enters the terminal observation starting distance range, the terminal observation window is started; when both sides enter the limit confirmation stage, or when the slider begins to return, the terminal observation window is closed. The dimension of the terminal observation starting distance is length, which is jointly determined by the set buffer distance, the set bending speed, and the rated deceleration of the servo axis. Specifically, the basic observation range is determined according to the set buffer distance in the bending program, and the braking distance required to meet safe convergence is determined according to the set bending speed and the rated deceleration of the servo axis. The maximum value between the basic observation range and the braking distance is taken as the terminal observation starting distance. The terminal observation starting distance is not less than the set buffer distance. The terminal observation starting distance of commonly used servo bending machines is preferably 5mm to 30mm. In high-speed approach or long plate bending conditions, the terminal observation starting distance is determined according to the equipment braking test record and bending quality verification record, preferably 10mm to 60mm. The terminal observation starting distance is used to ensure that the observation of the terminal status on both sides is earlier than the limit confirmation process, and to reserve control response time for the subsequent identification of the single-sided limit arriving first.

[0028] Within the terminal observation window, a single-sided terminal approach description quantity on the left and a single-sided terminal approach description quantity on the right are formed respectively. Each single-sided terminal approach description quantity is formed by the convergence state, velocity decay state, load establishment state, and position following change state of the remaining distance of the corresponding side limit.

[0029] The convergence state of the remaining limit distance is calculated based on the ratio of the remaining limit distance on the corresponding side to the starting distance of the terminal observation. It is a dimensionless result used to characterize the degree of approach of the target limit reference on the corresponding side servo axis. This processing enables the left and right sides to be compared under the same terminal approach scale even when they have different target limit references.

[0030] The speed decay status is formed based on the ratio of the current speed of the corresponding side to the speed when entering the terminal observation window. It is a dimensionless result. The speed when entering the terminal observation window is used as the reference value of the terminal speed of the corresponding side. When the speed when entering the window is lower than the minimum stable speed of the servo driver, the terminal speed is set as the reference value using a bending program. The minimum stable speed of the servo driver is determined by the rated speed resolution of the servo driver, the equipment debugging record, or the no-load synchronous downlink test record. The speed decay status is used to characterize whether the corresponding side has entered the buffer deceleration process, avoiding the need to judge the terminal status solely based on the degree of proximity.

[0031] The load establishment state is formed based on the offset of the corresponding side load feedback relative to the no-load load baseline. The no-load load baseline is preferentially formed by the stable sampling segment within 100ms to 300ms before the start of the terminal observation window, where no bending contact has occurred. The dimension of this time window is time, and the value is based on the sampling stability of the non-contact segment before terminal observation and the response time of the load feedback sensor. If this sampling segment is insufficient, the non-contact segment baseline in the no-load synchronous downlink test record or the most recent qualified bending record under the same working condition is used. The load establishment state is used to characterize the load formation process caused by plate contact, mold contact, or terminal pressure. The load feedback involved in the formation of the load establishment state is first converted to the same mechanical scale, and then participates in the same-side comparison and the two-side comparison.

[0032] The position following change state is formed based on the change of the position following error between the commanded position and the actual position within a sliding window. The length of the sliding window is measured in units of time and is determined based on the servo driver response time and the sampling period of the control system, preferably between 20ms and 80ms. When the servo driver response time of the device exceeds this range, the length of the sliding window is synchronously corrected based on the device debugging record. The position following change state is used to characterize the degree of lag or deviation of the actual movement of the corresponding side relative to the control command, providing a basis for the motion execution level for subsequent identification of the candidate first-arriving side.

[0033] After the single-sided terminal approach descriptive quantities on the left and right sides are formed, they are further differentiated and aggregated to form a bilateral differential descriptive quantity. The bilateral differential descriptive quantity includes limit approach difference, velocity decay difference, load establishment difference, and position following change difference. Each type of difference retains the difference direction and difference magnitude. The difference direction is used to indicate whether the left or right side is in the leading state in the corresponding descriptive quantity, and the difference magnitude is used to indicate the degree of separation between the two terminal approach states. The output of this process is the bilateral differential descriptive quantity, which is used by S2 to determine the candidate first arrival side and by S3 to distinguish between ordinary position difference and structural conflict caused by load imbalance when interpreting the source of synchronization deviation.

[0034] Finally, the left-side single-sided terminal approach descriptor, the right-side single-sided terminal approach descriptor, the bilateral difference descriptor, the start and end times of the terminal observation window, the data quality marker, the bending process parameters, and the beam stiffness calibration data are combined as the bilateral terminal approach observation results and output to step S2. Step S1 processes the differences between the zero-point calibration, program target, and terminal safety reservation on both sides through the side limit reference fusion method. Then, through the unified observation of limit remainder, speed attenuation, load establishment, and position following change, it provides a common data basis for subsequent terminal approach stage label determination, single-sided limit first arrival state identification, and beam torsional conflict state identification.

[0035] In one implementation, step S2 receives the bilateral terminal proximity observation results output by step S1, and generates terminal proximity stage labels for the left servo axis and the right servo axis respectively based on the bilateral terminal proximity observation results. Then, the bilateral terminal proximity stage labels are used to form a bilateral stage difference quantity. Combined with the bilateral difference descriptive quantity, the unilateral limit first arrival state is identified. The bilateral terminal proximity observation results include the left unilateral terminal proximity descriptive quantity, the right unilateral terminal proximity descriptive quantity, the bilateral difference descriptive quantity, the start and end times of the terminal observation window, the data quality mark, the bending process parameters, and the beam stiffness calibration data. The beam stiffness calibration data does not participate in the unilateral limit first arrival state identification in step S2, and is transmitted to step S3 along with the output results of step S2.

[0036] When the data quality marker indicates that the bilateral terminal approach observation results have low confidence observation markers, step S2 retains the low confidence observation markers, does not perform the unilateral limit first arrival state identification, and passes the low confidence observation markers to step S3. This process is used to avoid continuing to perform the terminal approach stage judgment when sampling is missing, load feedback is abnormal, or bilateral data cannot be reliably aligned.

[0037] Before determining the terminal approach stage label, the terminal approach stage judgment criteria are formed based on bending process parameters, historical qualified bending records, and equipment calibration records. The terminal approach stage judgment criteria include buffer approach criteria, speed attenuation criteria, load establishment criteria, continuous establishment time criteria, limit confirmation approach criteria, limit confirmation speed criteria, and load stability criteria. Insufficient historical qualified bending records refer to fewer than 30 historical qualified bending records under the same working conditions, or fewer than 3 production batches covered.

[0038] The buffer approach reference is determined based on the terminal observation starting distance formed in step S1 and the set buffer distance in the bending program. It is used to determine whether the corresponding side has entered the buffer limit related area. The speed attenuation reference is determined based on the speed reduction ratio when entering the buffer limit approach stage in the historical qualified bending records. It is used to determine whether the corresponding side has entered the buffer deceleration process. If the historical qualified bending records are insufficient, the initial value is determined based on the servo drive rated deceleration, set bending speed and no-load synchronous downward test records. The load establishment reference is determined based on the historical qualified bending records under the same mold type, same plate thickness, same material category and same bending angle. It is used to determine whether the load establishment caused by terminal contact or pressure has occurred on the corresponding side. If the historical qualified bending records are insufficient, it is determined by the equipment factory calibration record, no-load synchronous downward test record or standard specimen off-center bending test record. The dimension of the continuous establishment time reference is time. It is used to limit the stage misjudgment caused by the fluctuation of a single sampling point. It is preferably 10ms to 50ms. This range is determined based on the servo drive response time, load feedback sensor response time and control system sampling period. If the equipment response time exceeds this range, it is synchronously corrected according to the equipment debugging record.

[0039] The normal synchronous approach phase is configured as the first phase, the buffer limit approach phase is configured as the second phase, and the limit confirmation phase is configured as the third phase. The phase number is used to compare the progressive relationship between the left and right servo axes during the bending end approach process. The servo axis with the later phase number indicates that its end approach is closer to the limit confirmation phase.

[0040] For the left and right servo axes, buffer approach judgment results are formed based on the approach descriptors of the corresponding single-side terminals. The buffer approach judgment results are formed by the convergence state of the remaining limit distance, the speed decay state, and the load establishment state. Specifically, the convergence state of the remaining limit distance is compared with the buffer approach benchmark to form the limit approach judgment result; the speed decay state is compared with the speed decay benchmark to form the speed decay judgment result; and the load establishment state is compared with the load establishment benchmark to form the load establishment judgment result. All three judgment results are converted into dimensionless evaluation values ​​from 0 to 1 and formed according to corresponding weights. The weights are determined by the contribution of the three judgment results in the historical qualified bending records to the buffer limit approach stage. When there are insufficient historical qualified bending records, equal weights are used as the initial setting and updated in subsequent qualified bending records.

[0041] When the corresponding side does not meet the buffer approach judgment condition, the terminal approach stage label of that side is determined as the normal synchronous approach stage. The buffer approach judgment condition is formed by the buffer approach reference, the speed attenuation reference, the load establishment reference and the continuous establishment time reference. Specifically, when the corresponding side does not reach the buffer approach reference, or the speed attenuation judgment result and the load establishment judgment result do not reach the buffer establishment condition within the continuous establishment time reference, the side maintains the normal synchronous approach stage label.

[0042] When the remaining distance of the corresponding side limit continues to converge, and the buffer approach judgment result meets the buffer establishment condition within the continuous establishment time reference, the terminal approach stage label of that side is determined as the buffer limit approach stage. The continuous convergence of the remaining limit distance means that within the sampling window corresponding to the continuous establishment time reference, the remaining distance of the corresponding side limit does not expand in the opposite direction, and the corresponding side is still approaching along the target limit reference direction. This condition is used to exclude stage misjudgment caused by instantaneous fluctuations of the sensor, slider rebound or temporary pause.

[0043] When the corresponding side approaches the corresponding target limit reference, the speed converges to the limit confirmation range, and the load change enters the limit confirmation fluctuation range, the terminal approach stage label of that side is determined as the limit confirmation stage. The limit confirmation approach reference is determined based on the equipment positioning accuracy, limit confirmation retention amount, and bending process specifications; the limit confirmation speed reference is determined based on the minimum stable speed of the servo drive, the terminal pressure holding requirements, and the equipment debugging records; the load stability reference is determined based on the load fluctuation range of the pressure holding section in the historical qualified bending records. If the historical qualified bending records are insufficient, the standard test piece bending verification records or the no-load synchronous downward test records are used to form the initial reference.

[0044] After determining the terminal approach stage labels for the left and right servo axes, the stage numbers corresponding to the terminal approach stage labels on both sides are compared to form a bilateral stage difference. When the stage number of the left servo axis is higher than that of the right servo axis, the left servo axis is identified as the candidate first-arrival side and the right servo axis is identified as the candidate non-arrival side. When the stage number of the right servo axis is higher than that of the left servo axis, the right servo axis is identified as the candidate first-arrival side and the left servo axis is identified as the candidate non-arrival side. When the stage numbers on both sides are the same, no candidate first-arrival side is generated, and the bilateral stage difference is recorded as 0.

[0045] Between the candidate first-arrival side and the candidate non-arrival side, a unidirectional verification is performed on the bilateral difference description quantities within a continuous sampling window. The unidirectional verification is used to determine whether the candidate first-arrival side continuously meets the first-arrival conditions in terms of limit approach difference, speed decay difference, load establishment difference, and position following change difference. The unit of the continuous sampling window is time, which is used to confirm the unilateral limit first-arrival state, preferably 10ms to 60ms. This range is determined based on the continuous establishment time reference, sampling period, servo drive response time, and load feedback response time. If the equipment response time or load feedback response time exceeds this range, it is corrected based on the equipment debugging record and standard specimen bending verification record.

[0046] Specifically, within the continuous sampling window, when the limit approach difference between the candidate first-arriving side and the candidate non-arriving side reaches the limit approach difference benchmark, the speed decay difference reaches the speed decay difference benchmark, the load establishment difference reaches the load establishment difference benchmark, and the position following change difference reaches the position following change difference benchmark, the bilateral difference description quantity is determined to meet the first-arrival condition. The limit approach difference benchmark is determined by the normal position difference and normal time difference of the left and right axes when entering the buffer limit approach stage in the historical qualified bending records; the speed decay difference benchmark is determined by the servo drive deceleration response error and the no-load synchronous downward test record; the load establishment difference benchmark is determined by the normal fluctuation range of the left and right loads under the same mold type, the same plate thickness, and the same material category; the position following change difference benchmark is determined by the servo drive position following accuracy, the screw backlash calibration record, and the no-load synchronous downward test record. When the historical qualified bending records are insufficient, the equipment factory synchronization accuracy, load feedback sensor repeatability, torque detection repeatability, and standard specimen off-center bending test record are used to form the initial difference benchmark.

[0047] During the same-direction verification process, the differences in limit approach, speed attenuation, load establishment, and position following changes are converted into difference judgment results of 0 to 1 according to the corresponding difference benchmarks. Based on each difference judgment result, a single-sided limit arrival first establishment quantity is formed. The single-sided limit arrival first establishment quantity is used to characterize the comprehensive establishment degree of the candidate first arrival side relative to the candidate non-arrival side in terms of stage precedence and bilateral difference description quantity. The weight of each difference judgment result is determined by the contribution of the corresponding difference in the historical qualified bending records to the distinction of the single-sided limit arrival first state. When there are insufficient historical qualified bending records, equal weights are used as the initial setting and updated in subsequent qualified bending records.

[0048] When the candidate first-arrival side arrives first in the terminal approach phase, and the first-arrival establishment amount of the single-sided limit reaches the first-arrival establishment threshold within the continuous sampling window, a single-sided limit first-arrival state is generated. The first-arrival establishment threshold is determined by historical qualified bending records, abnormal terminal approach records, or standard specimen off-center bending verification records. If historical qualified bending records and abnormal terminal approach records are insufficient, the standard specimen off-center bending verification records are used to form the initial threshold. The single-sided limit first-arrival state includes a state flag, a first-arrival side identifier, a non-arrival side identifier, a bilateral phase difference amount, a single-sided limit first-arrival establishment amount, and a state duration. The state duration is calculated from the first time the single-sided limit first-arrival state is established and is updated with the continuous sampling window.

[0049] The candidate first-arrival side goes first in the terminal approach phase, but if the first-arrival establishment amount of the single-sided limit does not reach the first-arrival establishment threshold within the continuous sampling window, the single-sided limit first-arrival state is not generated, and the terminal approach phase labels of both sides and the difference between the two sides are retained as reference inputs for the subsequent interpretation of the source of synchronization deviation. This process is used to avoid determining the single-sided limit first-arrival state based solely on the short-term jump of the phase label.

[0050] Step S2 outputs the left servo axis terminal approach stage label, the right servo axis terminal approach stage label, the bilateral stage difference amount, the unilateral limit first arrival state, the first arrival side identifier, the non-arrival side identifier, the unilateral limit first arrival establishment amount and the state duration, and passes them to step S3. Step S2 converts the terminal approach process of the left and right servo axes into comparable stage labels, and performs joint verification of the stage precedence relationship and the bilateral difference description amount to identify the unilateral limit first arrival state, providing input for the subsequent explanation of the source of synchronization deviation.

[0051] In one implementation, step S3 receives the bilateral terminal approach observation results output by step S1, and the left servo axis terminal approach stage label, right servo axis terminal approach stage label, bilateral stage difference amount, single-sided limit first arrival state, first arrival side identifier, non-arrival side identifier, single-sided limit first arrival establishment amount and state duration output by step S2. Step S3 is used to interpret the source of the synchronization difference on both sides during the bending terminal approach process, and generate the synchronization deviation source result and the crossbeam torsional conflict state. The synchronization deviation source result is used as the input for step S4 to generate the compensation gating result.

[0052] When the result transmitted in step S2 contains a low-confidence observation marker, step S3 does not perform the identification of the crossbeam torsion conflict state, retains the low-confidence observation marker and transmits it to step S4. This process is used to avoid interpreting sensor abnormalities, sampling omissions or time base inconsistencies as the crossbeam torsion conflict state when the data quality of the observation results is insufficient at both ends.

[0053] Step S3 first determines the synchronization deviation source analysis window. The synchronization deviation source analysis window starts at the sampling time when the terminal approach stage label changes and ends at the sampling time when both sides enter the limit confirmation stage or the slider begins to return. When step S2 has generated the unilateral limit first arrival state, the load response window is traced back from the moment the unilateral limit first arrival state is first established as the analysis starting point. The dimension of the load response window is time, preferably 20ms to 80ms. Its value is based on the response time of the load feedback sensor, the response time of the servo drive, and the sampling period of the control system. When the equipment response time exceeds this range, it is corrected according to the equipment debugging record and the standard specimen off-center bending test record. This window is used to cover the load change process before and after the formation of the unilateral limit first arrival state, avoiding the explanation of the synchronization deviation source based solely on single-point data after the state is established.

[0054] Within the synchronization deviation source analysis window, step S3 constructs the current working condition baseline difference based on the bending process parameters. The current working condition baseline difference is used to characterize the allowable range of left and right position synchronization residuals, left and right load difference range, and left and right load fluctuation range during qualified processing under the current bending working condition. The current working condition baseline difference is preferentially formed from similar historical qualified bending records. Similar historical qualified bending records are filtered according to the same mold type, the same material category, the same plate thickness level, the same bending angle level, the same plate length level, and the same set bending speed level. When there are fewer than 30 historical qualified bending records or fewer than 3 production batches covered, the initial baseline is formed sequentially using standard specimen off-center load bending test records, no-load synchronous downward test records, or equipment factory calibration records. The output of this process is the current working condition baseline difference, which is used to ensure that the identification of the crossbeam torsional conflict state is established above the normal difference range of the current processing working condition, avoiding the interpretation of normal off-center load processing as abnormal torsion.

[0055] Subsequently, step S3 generates left and right position synchronization residuals. Specifically, the difference between the actual position of the left servo axis and the actual position of the right servo axis is subtracted from the difference between the commanded position of the left servo axis and the commanded position of the right servo axis to obtain the left and right position synchronization residuals. The dimension of the left and right position synchronization residuals is length, which is used to eliminate the influence of the difference between the side target limit reference, the zero point calibration difference and the process compensation difference on the difference between the actual left and right positions. The output of this process is the left and right position synchronization residuals, which are used to separate the left and right differences that are allowed to exist in the command reference from the synchronization deviation formed during the execution process.

[0056] Step S3 further generates a bilateral equivalent load difference from the load states on both sides. The load states on the left and right sides are derived from the bilateral terminal proximity observation results generated in step S1 and have been converted to the same mechanical scale. When the equipment uses an independent load sensor, the corresponding equivalent load is generated based on the sensor calibration coefficient, effective pressure area, or strain load calibration relationship. When the equipment is not equipped with an independent load sensor, the corresponding equivalent load is converted from the servo torque based on the servo motor torque constant, transmission ratio, lead screw, and transmission efficiency. When both independent load sensors and servo torque feedback exist, the fusion weight is determined based on the standard load test record or sensor calibration record to generate the corresponding equivalent load. When historical records are insufficient, the conversion result of the independent load sensor is used as the master data, and the conversion result of the servo torque is used as the consistency verification data. The difference between the equivalent load on the left and the equivalent load on the right forms the bilateral equivalent load difference. The dimension of the bilateral equivalent load difference is force, which is used to characterize the direction and amplitude of the uneven force on the left and right sides and serves as the input for the conversion of the equivalent relative displacement of the beam.

[0057] Then, in step S3, the equivalent relative displacement of the beam is calculated based on the beam stiffness calibration data. The beam stiffness calibration data includes records of the beam differential stiffness under different slider heights, different mold installation positions, and different bending length levels. In the current bending cycle, the current beam differential stiffness is obtained by selecting or interpolating from the beam stiffness calibration data based on the current slider height, mold installation position, and bending length level. The dimension of the current beam differential stiffness is the ratio of force to length, which is used to characterize the load strength required for a unit relative displacement caused by the difference in equivalent loads on both sides. After the difference in equivalent loads on both sides is converted by the current beam differential stiffness, the equivalent relative displacement of the beam is obtained. The dimension of the beam equivalent relative displacement is length, which is used to represent the relative deformation on the beam structure corresponding to the uneven loads on the left and right sides.

[0058] After the equivalent relative displacement of the beam is formed, step S3 compares the equivalent relative displacement of the beam with the left and right position synchronous residuals to form the position load consistency residual. The position load consistency residual is used to characterize whether the relative deformation calculated from the difference of the equivalent loads on both sides can be explained by the left and right position synchronous residuals. When the difference between the equivalent relative displacement of the beam and the left and right position synchronous residuals does not exceed the consistency benchmark, the current load difference is interpreted as being able to be borne by the normal position synchronous residuals or the structural elastic response. When the difference is greater than the consistency benchmark and less than the residual establishment benchmark, the position load consistency residual is recorded as pending confirmation and is updated continuously within the continuous window. When the difference reaches the residual establishment benchmark, it indicates that the left and right position synchronous residuals cannot explain the current load imbalance state, and the consistency benchmark is less than the residual establishment benchmark. The two are determined by the no-load synchronous downward test record, the standard specimen off-center bending test record, the equipment factory synchronization accuracy and maintenance calibration record. When there are fewer than 30 historical qualified bending records or fewer than 3 production batches covered, the equipment factory calibration record and the standard specimen off-center bending test record are used to form the initial benchmark.

[0059] When the current differential stiffness of the crossbeam meets the effective lower limit of stiffness, the calculation of the crossbeam torsional conflict is performed; when the current differential stiffness of the crossbeam is less than the effective lower limit of stiffness, the crossbeam torsional conflict state judgment is not performed, and the equipment preset safety buffer limit strategy is switched to output a stiffness calibration abnormality prompt. The effective lower limit of stiffness is determined by the equipment factory stiffness calibration record, maintenance calibration record and standard specimen off-center bending test record.

[0060] In this embodiment, the torsional conflict of the crossbeam is calculated using the following formula: ; in, The quantity representing the crossbeam torsional conflict at the current sampling moment is a dimensionless result ranging from 0 to 1. It is used to characterize whether there is an imbalance state in the current bending terminal approach process where the left and right position synchronization residuals are still within the allowable range, but the left and right load states have already appeared that cannot be explained by the position synchronization residuals. The quantity representing the crossbeam torsional conflict serves as the basis for judging the generation of the crossbeam torsional conflict state and is passed to step S4 to generate the compensation gating result.

[0061] This represents the current sampling time, which originates from the sampling time after unified time base processing in step S1. All quantities that change with time in the formula correspond to the same sampling time.

[0062] This represents the position synchronization characteristic quantity, a dimensionless result ranging from 0 to 1. It is obtained by mapping the left and right position synchronization residuals relative to the allowable range of synchronization error. The allowable range of synchronization error is determined by the equipment's factory synchronization accuracy, no-load synchronous downlink test records, and historical qualified bending records. The closer the position synchronization characteristic quantity is to 1, the closer the left and right position synchronization residuals are to the allowable range of synchronization error; the closer the value is to 0, the closer the left and right position synchronization residuals are to the allowable range of synchronization error. This quantity is used as a gating term in the formula.

[0063] The load unevenness characterization quantity is a dimensionless result ranging from 0 to 1. It is obtained by mapping the difference between the two-sided equivalent load difference and the current working condition baseline. The current working condition baseline difference is formed by the historical qualified bending records of the same type. When there are fewer than 30 historical qualified bending records or fewer than 3 production batches covered, the initial baseline is formed by using the standard specimen off-center bending test record, the no-load synchronous downward test record, or the equipment factory calibration record in sequence. The closer the load unevenness characterization quantity is to 1, the more the two-sided equivalent load difference exceeds the allowable load difference range of qualified processing under the current working condition.

[0064] The difference in equivalent loads on both sides is expressed in N. It corresponds to the difference between the equivalent loads on the left and right sides in step S3. The difference in equivalent loads on both sides is used to characterize the direction and magnitude of the uneven force on the left and right sides, and serves as the input for the conversion of the equivalent relative displacement of the beam.

[0065] This represents the current differential stiffness of the crossbeam, in N / mm. It corresponds to the stiffness result obtained in step S3 by selecting or interpolating the crossbeam stiffness calibration data according to the current slider height, mold installation position, and bending length setting. The current differential stiffness of the crossbeam is used to convert the difference in equivalent loads on both sides into the equivalent relative displacement of the crossbeam.

[0066] This represents the stiffness denominator protection amount, in N / mm, with a value greater than 0. Its value is based on the minimum effective resolution of the beam stiffness calibration data. The purpose of setting the stiffness denominator protection amount is to avoid denominator failure when the current beam differential stiffness is close to 0. When the current beam differential stiffness is less than the effective lower limit of stiffness, the calculation of the beam torsional conflict corresponding to this formula will not be executed.

[0067] By introducing the scale transformation from mechanics to kinematics, the non-negative truncation of residuals (max function), and the normalization constraint function with upper and lower limits ( This paragraph clearly elucidates the mathematical logic of how position-load mismatch is transformed into conflict intensity.

[0068] This represents the equivalent relative displacement of the beam calculated from the difference in equivalent loads on both sides, in mm. This item is used to convert the load difference from a mechanical scale to a displacement scale, so that it can be compared with the synchronous residuals of the left and right positions in the same dimension.

[0069] The left and right position synchronization residual is expressed in mm. It corresponds to the intermediate result formed by subtracting the left and right command position difference from the actual left and right position difference in step S3. The left and right position synchronization residual is used to eliminate the influence of the side target limit reference, zero point calibration difference and process compensation difference on the left and right position difference.

[0070] This represents the non-negative part of the position load consistency residual, in mm. This term characterizes the extent to which the equivalent relative displacement of the beam calculated from the difference in equivalent loads on both sides exceeds the range that can be explained by the left and right position synchronization residuals. When the equivalent relative displacement of the beam is less than or equal to the left and right position synchronization residuals, this difference is 0, indicating that the current load difference can be explained by the left and right position synchronization residuals or the structural elastic response, and is not used as the basis for establishing the torsional conflict state of the beam. When the equivalent relative displacement of the beam is greater than the left and right position synchronization residuals, the excess part enters the subsequent normalization mapping.

[0071] This represents a normalization constraint function used to map the non-negative part of the position load consistency residual to a dimensionless result of 0 to 1 according to the residual starting datum and the upper limit datum of the beam torsional conflict residual. When the input is less than or equal to the residual starting datum, the output is 0; when the input is greater than or equal to the upper limit datum of the beam torsional conflict residual, the output is 1; when the input is between the two, the output is linearly proportional. This normalization constraint function is used to form the conflict intensity evaluation result corresponding to the position load consistency residual.

[0072] The residual starting reference is expressed in mm and is used to characterize the upper limit of the position load consistency residual that can be explained by system synchronization error, sensor error and assembly clearance. This reference is determined by the no-load synchronous downlink test record, the equipment factory synchronization accuracy, sensor error calibration record and maintenance calibration record.

[0073] The upper limit benchmark of the crossbeam torsional conflict residual is expressed in mm. It is used to characterize the residual level at which the positional load consistency residual has reached the level where the crossbeam torsional conflict is significantly established. This benchmark is determined by the standard specimen off-center bending test record, crossbeam stiffness calibration data and maintenance calibration record. The upper limit benchmark of the crossbeam torsional conflict residual is greater than the residual starting benchmark to ensure that the normalization boundary is legal.

[0074] The weighting of the load unevenness indicator. The weights represent the position load consistency residuals and are both dimensionless, with a sum of 1. The weights are determined by the contribution of the corresponding characterization quantities in historical qualified bending records, standard specimen off-center bending test records, and maintenance calibration records to the differentiation of the torsional conflict state of the crossbeam. When there are fewer than 30 historical qualified bending records or fewer than 3 production batches covered, equal weights are used as the initial setting and are updated in subsequent maintenance calibration records and qualified bending records. The weights are only allocated between the load unevenness characterization quantity and the position load consistency residuals, without changing the role of the position synchronization characterization quantity as a gating item.

[0075] The design logic of the formula is as follows: First, use the position synchronization characterization quantity to determine whether the left and right position synchronization residuals are still within the allowable range of synchronization error. Then, use the load unevenness characterization quantity to evaluate whether the left and right forces exceed the current working condition baseline difference. Furthermore, use the position load consistency residual to evaluate whether the equivalent relative displacement of the beam calculated from the equivalent load difference on both sides can be explained by the left and right position synchronization residuals. Since the key feature of the beam under torsion conflict state is that the position is synchronized but the load unevenness cannot be explained by the position residuals, the position synchronization characterization quantity is set as the outer gating term of the formula, and the load unevenness characterization quantity and the position load consistency residual are combined as conflict intensity terms for calculation. The calculation result is used to generate the beam under torsion conflict state and support the compensation gating of the synchronous leveling compensation action on both sides in step S4.

[0076] When the position synchronization characteristic reaches the position synchronization establishment benchmark within a continuous window, the load unevenness characteristic reaches the load unevenness establishment benchmark within a continuous window, and the position load consistency residual reaches the residual establishment benchmark within a continuous window, a torsional conflict state of the crossbeam is generated. The dimension of the continuous window is time, preferably 10ms to 60ms, determined by the control system sampling period, servo driver response time, and load feedback response time. When the equipment response time exceeds this range, it is corrected based on the equipment debugging record and the standard specimen off-center bending test record. The position synchronization establishment benchmark is determined by the equipment factory synchronization accuracy, no-load synchronous downward test record, and historical qualified bending record. The load unevenness establishment benchmark is determined by the current working condition baseline difference, the standard specimen off-center bending test record, and historical qualified bending record. The residual establishment benchmark is determined by the current crossbeam differential stiffness, sensor error, assembly clearance, and maintenance calibration record.

[0077] When the current equivalent load difference between the two sides is within the load difference range corresponding to the normal off-center load record, the torsional conflict state of the crossbeam is not generated. The normal off-center load record is formed by the workpiece center offset relative to the machine tool center, bending length, back gauge coordinates, left and right support positions, plate placement offset record and historical qualified off-center load bending record in the bending program. This process is used to distinguish between normal off-center load processing and the torsional conflict state of the crossbeam, and to avoid interpreting the off-center load force that conforms to the bending process arrangement as a structural conflict.

[0078] The torsional conflict state of the crossbeam includes a state mark, the amount of torsional conflict of the crossbeam, the position load consistency residual, the difference between the two sides of the equivalent load, the duration of the state, and the torsional direction mark. The torsional direction mark is determined by the direction of the difference between the two sides of the equivalent load and is used to distinguish the high load side and the low load side in step S4.

[0079] After generating the torsional conflict state of the crossbeam, step S3 combines the unilateral limit arrival state to generate the synchronous deviation source results. The synchronous deviation source results include normal off-center load synchronous difference, unilateral limit arrival, crossbeam torsional conflict state, and composite sources. When the left servo axis terminal approach stage label and the right servo axis terminal approach stage label are the same, or the difference between the two stages does not continuously meet the requirements for the unilateral limit arrival state, and the equivalent load difference between the two sides is within the current working condition baseline difference range, and the position load consistency residual does not reach the residual establishment benchmark, then... The source of the synchronization deviation is determined to be normal off-center load synchronization difference. When the state of unilateral limit arrival is established in step S2 and the state of crossbeam torsion conflict is not established, the source of the synchronization deviation is determined to be unilateral limit arrival. When the state of crossbeam torsion conflict is established and the state of unilateral limit arrival is not established, the source of the synchronization deviation is determined to be crossbeam torsion conflict. When the state of unilateral limit arrival and the state of crossbeam torsion conflict are established at the same time, the source of the synchronization deviation is determined to be a composite source, and the dominant source label is set to crossbeam torsion conflict.

[0080] Step S3 outputs the results of the synchronous deviation source, the torsional conflict state of the crossbeam, the dominant source label, the equivalent load difference between the two sides, the position load consistency residual, the establishment amount of the torsional conflict of the crossbeam, the torsional direction label, the first-arriving side label, and the non-arriving side label, and passes them to step S4. Based on the observation results of the first-arriving state of the single-sided limit and the approach of the double-sided terminal, step S3 distinguishes the normal off-center load synchronous difference, the first-arriving state of the single-sided limit, the torsional conflict state of the crossbeam, and the composite source, so that the subsequent compensation gating results can perform differentiated control based on the synchronous deviation source results.

[0081] In one implementation, step S4 receives the synchronization deviation source result, crossbeam torsional conflict state, dominant source label, bilateral equivalent load difference, position load consistency residual, crossbeam torsional conflict establishment amount, torsional direction identifier, first-arrival side identifier, and non-arrival side identifier output by step S3, and generates a compensation gating result based on the synchronization deviation source result and crossbeam torsional conflict state. The compensation gating result is used to limit the synchronization tracking compensation action of the left servo axis and the right servo axis, and forms a differentiated buffer limit control result.

[0082] When the result transmitted in step S3 contains a low-confidence observation marker or a stiffness calibration anomaly prompt, step S4 does not adjust the synchronous tracking compensation action based on the torsional conflict state of the crossbeam, but switches to the equipment preset safety buffer limit strategy and outputs a data confidence anomaly prompt or a stiffness calibration anomaly prompt. This anomaly branch is only triggered when the two-sided terminals are close to the observation result or the crossbeam stiffness calibration data does not meet the judgment conditions.

[0083] In this embodiment, the speed control domain is used to form the final control output. When the servo driver adopts the position control mode, the final speed command is converted into a position increment command according to the sampling period of the control system and then output to the servo driver. The final speed command adopts a non-negative speed amplitude along the downward direction of the slider. The negative correction is only used to converge the downward speed on the corresponding side and does not directly generate a reverse return action in the final speed command. When reverse unloading or return is required, the equipment preset protection control or return control strategy is executed.

[0084] Before generating the compensation gating result, the pre-gating synchronous speed correction and the terminal buffer speed upper limit are first formed. The pre-gating synchronous speed correction is calculated from the left and right position synchronous residuals and equipment synchronous control parameters formed in step S3. Its dimension is speed. It is used as the input for compensation gating processing and is not directly used as the final speed command output. The equipment synchronous control parameters are determined by the equipment's factory synchronous control parameters, no-load synchronous downward test records, or historical qualified bending records. The terminal buffer speed upper limit is formed by the left limit remaining distance, the right limit remaining distance, the servo axis rated safe deceleration, and the limit confirmation retention amount. Its dimension is speed. It is used to ensure that the corresponding side has a safe convergence margin before reaching the corresponding target limit reference. The limit confirmation retention amount is determined by the side limit reference fusion method in step S1. Its value is based on the equipment positioning accuracy, the lead screw return clearance, the die closing safety margin, and the bending process specifications.

[0085] The compensation gating results include the synchronization gating coefficient, the common downlink suppression coefficient, the first-arrival gating coefficient, the non-arrival side following coefficient, the control mode label, and the control priority label. The synchronization gating coefficient is used to limit the proportion of the synchronization speed correction before gating; the common downlink suppression coefficient is used to constrain the common downlink speed of the left and right servo axes; the first-arrival gating coefficient is used to limit the first-arrival side from continuing to approach the corresponding target limit reference; and the non-arrival side following coefficient is used to constrain the speed at which the non-arrival side approaches the corresponding target limit reference. All coefficients are dimensionless results ranging from 0 to 1.

[0086] The synchronization leveling gate coefficient is formed based on the crossbeam torsional conflict establishment amount and the crossbeam torsional conflict threshold. When the crossbeam torsional conflict establishment amount does not reach the crossbeam torsional conflict threshold, the synchronization leveling gate coefficient maintains the range of action corresponding to the equipment synchronization control parameters. After the crossbeam torsional conflict establishment amount reaches the crossbeam torsional conflict threshold, the synchronization leveling gate coefficient converges towards the lower gate limit according to the degree to which the crossbeam torsional conflict establishment amount exceeds the crossbeam torsional conflict threshold. The crossbeam torsional conflict threshold is a dimensionless threshold from 0 to 1, preferably 0.6 to 0.8, determined by historical... The threshold is determined by historical abnormal terminal approach records, standard specimen off-center bending test records, and maintenance calibration records. If there are fewer than 5 historical abnormal terminal approach records or the off-center bending condition is not covered, the standard specimen off-center bending test records are used to form the initial threshold. The lower limit of the threshold is a dimensionless result of 0 to 1, preferably 0.1 to 0.4, which is determined by the equipment's safe deceleration capability, bending quality verification records, and the equipment's allowable rate of acceleration change. If the historical records are insufficient, the initial lower limit of the threshold is determined by the equipment debugging records and standard specimen off-center bending verification records.

[0087] The common downward suppression coefficient is formed based on the amount of torsional conflict of the crossbeam. When the amount of torsional conflict of the crossbeam reaches the torsional conflict threshold, the common downward suppression coefficient converges according to the allowable rate of change of acceleration of the equipment, the upper limit of the terminal buffer speed and the load feedback response time, so that the common downward speed of the left servo axis and the right servo axis is limited. The common downward suppression coefficient is a dimensionless result from 0 to 1. Its value is based on the equipment's safe deceleration capability, bending terminal speed, load feedback response time and historical anomaly handling records. When there are fewer than 5 historical anomaly handling records, the initial coefficient is formed by the equipment debugging records and the standard test piece off-center bending verification records.

[0088] When the synchronization deviation source result is that the single-sided limit arrives first, the first-arrival side gating coefficient and the non-arrival side following coefficient are generated according to the single-sided limit first-arrival establishment amount, the first-arrival side identifier, and the non-arrival side identifier formed in step S2. After the single-sided limit first-arrival establishment amount reaches the first-arrival establishment threshold, the first-arrival side gating coefficient converges according to the degree of the single-sided limit first-arrival establishment amount exceeding the first-arrival establishment threshold, which is used to limit the first-arrival side from continuing to press closer to the corresponding target limit reference direction. The non-arrival side following coefficient is jointly determined by the remaining distance of the non-arrival side limit, the upper limit of the non-arrival side terminal buffer speed, the first-arrival side gating coefficient, and the bilateral stage difference amount.

[0089] When the non-reaching side is in the normal synchronous approach phase, it approaches the corresponding target limit reference at a speed not exceeding the terminal buffer speed limit. When the non-reaching side enters the buffer limit approach phase, the non-reaching side's following coefficient converges to the following allowable range according to the continuous sampling window. The following allowable range is jointly determined by the limit confirmation retention amount, the limit confirmation speed reference, and the terminal buffer speed limit. When the non-reaching side enters the limit confirmation phase, the non-reaching side's following speed in the direction of the corresponding target limit reference is set to zero. The dimension of the limit confirmation speed reference is speed, which is determined by the servo drive's minimum stable speed, terminal pressure holding requirements, and equipment debugging records. This process is used to avoid the non-reaching side initiating new load impacts in the terminal area in order to catch up with the position difference.

[0090] The control mode label is determined based on the synchronization deviation source result. When the synchronization deviation source result is normal off-center load synchronization difference, the control mode label is set to normal off-center load synchronization difference mode. The left and right servo axes perform terminal buffer limit control according to the pre-gated synchronization speed correction and the terminal buffer speed upper limit. When the synchronization deviation source result is that the single-sided limit arrives first, the control mode label is set to single-sided limit arrives first mode. Convergence gating is applied to the compensation trend of the first-arriving side towards the corresponding target limit reference direction, and the non-arriving side is controlled to approach the corresponding target according to the non-arriving side following coefficient. For the limit reference, when the result of the synchronization deviation is the crossbeam torsion conflict state, the control mode label is set to the crossbeam torsion conflict mode. Based on the crossbeam torsion conflict establishment amount, the synchronous chasing compensation action on both sides is limited, and the torsion conflict speed correction amount is formed according to the torsion direction mark and the equivalent load difference on both sides. When the result of the synchronization deviation is a composite source, the control priority label is set to the crossbeam torsion priority. First, the synchronous chasing compensation action and common downward speed are limited according to the crossbeam torsion conflict state, and then the first-arriving side gating and the non-arriving side following control in the single-side limit first-arrival state are superimposed.

[0091] In the torsional conflict mode of the crossbeam, the high-load side and low-load side are determined based on the equivalent load difference between the two sides and the torsional direction indicator. For the high-load side, the torsional conflict speed correction is used to offset the speed correction trend of its continued approach to the corresponding target limit reference direction. For the low-load side, the torsional conflict speed correction forms a following speed correction within the upper limit of the terminal buffer speed. The torsional conflict speed correction is determined by the load unevenness characterization, the crossbeam torsional conflict establishment amount, and the speed correction mapping relationship. The input of the speed correction mapping relationship is the load unevenness characterization and the crossbeam torsional conflict establishment amount, and the output is the torsional conflict speed correction. The output boundary is constrained by the upper limit of the terminal buffer speed and the allowable rate of change of the equipment acceleration. The speed correction mapping relationship is determined by the standard specimen off-center bending test record, the allowable rate of change of the equipment acceleration, and the bending quality verification record. When the historical records are insufficient, the equipment debugging records are used to form the initial mapping relationship. This processing makes the speed correction corresponding to the load unevenness directly act on the approach trend of the high-load side and the following trend of the low-load side, avoiding the need for compensation based solely on the left and right position synchronous residuals.

[0092] The final speed command is formed according to the following textual logic: For either the left or right servo axis, firstly, the terminal speed and the upper limit of the terminal buffer speed on that side are set according to the bending program to form the basic buffer speed on that side; then, the corresponding buffer execution coefficient is determined according to the current control mode on that side, which comes from the common downlink suppression coefficient, the gating coefficient of the first-arriving side, or the following coefficient of the non-arriving side; then, the basic buffer speed is corrected according to the buffer execution coefficient to form the buffer speed component on that side; then, the synchronization speed correction amount before gating is limited according to the synchronization catching gating coefficient to form the synchronization speed correction component on that side; when the crossbeam is under torsional conflict, the torsional conflict speed correction component on that side is further formed according to the equivalent load difference between the two sides, the torsional direction mark, and the speed correction mapping relationship; finally, the buffer speed component, the synchronization speed correction component, and the torsional conflict speed correction component on that side are synthesized, and the synthesis result is limited to 0 to the upper limit of the terminal buffer speed on that side to obtain the final speed command on that side.

[0093] In the final speed command formation logic, the basic buffer speed, the synchronization speed correction component, the torsional conflict speed correction component, and the terminal buffer speed upper limit are all speed quantities with the dimension of mm / s; the buffer execution coefficient and the synchronization matching gating coefficient are both dimensionless results between 0 and 1. This process first forms the speed components and then applies gating and boundary restrictions, so that the final speed command not only inherits the terminal buffer control but also constrains the synchronization matching compensation action according to the synchronization deviation source result, and does not generate downlink speeds that exceed the terminal buffer speed upper limit or directly generate reverse return speeds.

[0094] In the normal off-center load synchronization difference mode, the buffer execution coefficient is 1, the torsional conflict speed correction component is 0, and the synchronization balancing gate coefficient maintains the range of action corresponding to the equipment synchronization control parameters. In the single-sided limit first arrival mode, the buffer execution coefficient of the first arrival side is determined by the first arrival side gate coefficient, and the buffer execution coefficient of the non-arrival side is determined by the non-arrival side follow coefficient. In the beam torsional conflict mode, the buffer execution coefficient is determined by the common downward suppression coefficient, and the torsional conflict speed correction component is formed based on the high load side and the low load side respectively. In the composite source mode, the gate restriction in the beam torsional conflict mode is used first, and then the first arrival side gate and the non-arrival side follow control in the single-sided limit first arrival mode are superimposed.

[0095] The final speed command is constrained by speed boundaries, acceleration boundaries, and limit confirmation retention amounts. When the speed change in adjacent sampling periods exceeds the allowable range of the servo axis's rated safe deceleration, the servo axis's rated safe deceleration is used for limitation. When the remaining limit distance on either side is less than the limit confirmation retention amount, the final speed command in the corresponding target limit reference direction on that side is set to zero, and that side enters the limit holding state. When the load feedback exceeds the equipment overload protection threshold, the equipment's preset overload protection logic is executed first. The equipment overload protection threshold is determined by the equipment's rated load, the mold's rated load-bearing capacity, and the bending process specifications.

[0096] After executing differentiated buffer limit control, the actual position, actual speed, actual torque, and load feedback of the left and right servo axes are collected to form the feedback status after the execution of differentiated buffer limit control. The feedback status includes the final speed command on both sides, actual speed, position following error, load establishment change, change in the amount of torsional conflict of the crossbeam, change in the duration of the first-to-reach state of the single-sided limit, control mode label, and control priority label, which are used to determine whether the control mode is maintained, switched, or released.

[0097] When the crossbeam torsional conflict threshold falls below the release threshold and continues to meet the release time reference, the synchronous balancing gate coefficient is restored to the range of action corresponding to the equipment synchronous control parameters in each sampling cycle, with each sampling cycle not exceeding the preset recovery step size. The release threshold is a dimensionless result of 0 to 1, and is less than the crossbeam torsional conflict threshold, used to form a hysteresis interval to avoid repeated switching of the control mode in adjacent sampling cycles. The release threshold is determined by historical abnormal terminal proximity records, standard specimen off-center bending test records, and maintenance calibration records, preferably 0.3 to 0.5. The historical abnormal terminal proximity records are less than 5. Next, the initial release threshold is formed using the standard specimen off-center bending test record. The dimension of the release time reference is time, which is determined by the servo drive response time, load feedback response time, and control system sampling period, preferably 30ms to 150ms. If the equipment response time exceeds this range, it is corrected according to the equipment debugging record. The preset recovery step size is a dimensionless result of 0 to 1, preferably 0.01 to 0.05 per sampling period. The value is based on the allowable rate of change of equipment acceleration and historical anomaly handling records. If there are fewer than 5 historical anomaly handling records, the initial value is formed using the equipment debugging record.

[0098] When the initial value of the unilateral limit first arrival is lower than the unilateral limit first arrival release reference, and the terminal approach stage labels of the left and right servo axes are consistent again, the unilateral limit first arrival state is determined to be released. The unilateral limit first arrival release reference is a dimensionless result of 0 to 1, determined by historical qualified bending records, abnormal terminal approach records, and standard specimen off-center bending verification records. If the historical records are insufficient, the standard specimen off-center bending verification records are used to form the initial reference. After the unilateral limit first arrival state is released, the system switches to normal off-center synchronization difference mode or enters the limit holding state according to the terminal approach stage labels of the left and right servo axes.

[0099] The final output is a differentiated buffer limit control result, which includes the final speed command for the left and right servo axes, control mode label, control priority label, limit holding status, and abnormal prompt information.

[0100] Example 2 like Figure 2 As shown, the present invention also discloses a servo bending machine buffer limit control system, comprising: The terminal observation construction module acquires bilateral operation observation information during the approach process of the bending terminal, corrects and generates bilateral target limit references by using the side limit reference fusion method, converts the actual positions of both sides into the left limit remaining distance and the right limit remaining distance in the unified downlink coordinate, collects the velocity attenuation, load establishment and position following changes of both sides, forms the single-sided terminal approach descriptive quantity and the bilateral difference descriptive quantity, and generates bilateral terminal approach observation results. The single-sided first-arrival recognition module generates terminal approach stage labels for the left and right servo axes based on the observation results of the two-sided terminal approach. The two-sided stage difference quantity is formed by the two-sided terminal approach stage labels and combined with the two-sided difference description quantity to identify the single-sided limit first-arrival state. The synchronization deviation source explanation module, based on the single-sided limit arrival state and the observation results of the double-sided terminal approach, subtracts the left and right command position difference from the actual left and right position difference to form the left and right position synchronization residual, and forms the double-sided equivalent load difference from the load state of both sides. The double-sided equivalent load difference is converted into the equivalent relative displacement of the beam through the beam stiffness calibration data, and the position load consistency residual is formed by the equivalent relative displacement of the beam and the left and right position synchronization residual, generating the torsional conflict state of the beam and the synchronization deviation source result; The compensation gating control module generates compensation gating results based on the source of synchronization deviation and the torsional conflict state of the crossbeam. It uses the compensation gating results to limit the synchronous leveling compensation action on both sides, executes differentiated buffer limit control, and outputs differentiated buffer limit control results.

[0101] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A buffer limit control method for a servo bending machine, characterized in that, include: The observation information of the two sides during the approach of the bending terminal is obtained. The two-sided limit reference is corrected and generated by the fusion method of the two-sided limit reference. The actual positions of the two sides are converted into the left limit remaining distance and the right limit remaining distance in the unified down-going coordinate. The speed attenuation, load establishment and position following changes of the two sides are collected to form the single-sided terminal approach descriptive quantity and the double-sided difference descriptive quantity, and the double-sided terminal approach observation results are generated. Based on the observation results of the two-sided terminal approach, terminal approach stage labels for the left and right servo axes are generated, and the two-sided stage difference quantity is formed by the two-sided terminal approach stage labels. Combined with the two-sided difference description quantity, the state of the unilateral limit arriving first is identified. Based on the observation results of the first arrival state of the single-sided limit and the approach of the double-sided terminal, the difference between the actual left and right positions is subtracted from the difference between the left and right commanded positions to form the left and right position synchronization residual. The double-sided equivalent load difference is formed by the load state of both sides. The double-sided equivalent load difference is converted into the equivalent relative displacement of the beam through the beam stiffness calibration data. The position load consistency residual is formed by the equivalent relative displacement of the beam and the left and right position synchronization residual. The results of the torsional conflict state of the beam and the source of synchronization deviation are generated. Based on the results of the synchronous deviation source and the torsional conflict state of the crossbeam, a compensation gating result is generated. The compensation gating result is used to limit the synchronous leveling compensation action on both sides, and differentiated buffer limit control is executed. The differentiated buffer limit control result is then output.

2. The servo bending machine buffer limit control method according to claim 1, characterized in that, The specific operation of correcting and generating target limit references on both sides using the side limit reference fusion method is as follows: the left servo axis and the right servo axis are treated as independent limit objects. Based on the equipment calibration record, bending program and safety limit rules, the equipment calibration offset, program target offset and terminal safety reserve on both sides are uniformly merged downlink coordinates. Then, the merged side offsets are fused to the target limit references on the corresponding sides, so that the left target limit reference and the right target limit reference correspond to the terminal limit constraints of the left servo axis and the right servo axis, respectively. Subsequently, the actual position of the left servo axis and the actual position of the right servo axis are mapped to the corresponding target limit references to obtain the remaining distance of the left limit and the remaining distance of the right limit.

3. The servo bending machine buffer limit control method according to claim 1, characterized in that, The specific operation for generating bilateral terminal proximity observation results is as follows: The starting distance for terminal observation is determined based on the set buffer distance and set bending speed recorded in the bending program record, and the rated deceleration of the servo axis recorded in the equipment calibration record. After the remaining distance of the limit switch on either side enters the starting distance for terminal observation, the terminal observation window is activated. Within the terminal observation window, a left-side single-sided terminal proximity description quantity and a right-side single-sided terminal proximity description quantity are generated. The single-sided terminal proximity description quantity is formed by the convergence state, velocity decay state, load establishment state, and position following change state of the corresponding side limit switch remaining distance. The left-side single-sided terminal proximity description quantity and the right-side single-sided terminal proximity description quantity are then differentially aggregated to form a bilateral differential description quantity. Finally, the left-side single-sided terminal proximity description quantity, the right-side single-sided terminal proximity description quantity, and the bilateral differential description quantity are all included in the bilateral terminal proximity observation results.

4. The servo bending machine buffer limit control method according to claim 1, characterized in that, The specific operation for generating terminal approach stage labels for the left and right servo axes is as follows: Based on the progressive relationship of the terminal approach process from the regular synchronous approach stage, the buffer limit approach stage, to the limit confirmation stage, a stage determination chain is established for the left and right servo axes respectively. When the corresponding side does not meet the buffer approach determination condition, a regular synchronous approach stage label is assigned. When the remaining limit distance on the corresponding side continues to converge, and the speed decay state and load establishment state meet the buffer establishment condition, a buffer limit approach stage label is assigned. The buffer establishment condition is jointly determined by the buffer approach reference, speed decay reference, load establishment reference, and continuous establishment time reference. When the corresponding side approaches the corresponding target limit reference, the speed converges to the limit confirmation range, and the load change enters the limit confirmation fluctuation range, a limit confirmation stage label is assigned.

5. The servo bending machine buffer limit control method according to claim 1, characterized in that, The specific operation for identifying the first-arrival state of a single-sided limit switch is as follows: Based on the terminal approach stage labels of the left and right servo axes, a bilateral stage difference quantity is formed, and the side in the later progressive stage is identified as the candidate first-arrival side, and the other side is identified as the candidate non-arrival side; between the candidate first-arrival side and the candidate non-arrival side, the limit approach difference, speed decay difference, load establishment difference, and position following change difference are continuously sampled within the same direction for verification; when the candidate first-arrival side moves first in the terminal approach stage, and the limit approach difference, speed decay difference, load establishment difference, and position following change difference meet the first-arrival condition, a single-sided limit switch first-arrival state is generated. The single-sided limit switch first-arrival state includes the first-arrival side identifier, the non-arrival side identifier, the bilateral stage difference quantity, and the state duration.

6. The servo bending machine buffer limit control method according to claim 1, characterized in that, The specific operation for forming the left and right position synchronization residuals and the double-sided equivalent load difference is as follows: the difference between the actual position of the left servo axis and the actual position of the right servo axis is subtracted from the difference between the command position of the left servo axis and the command position of the right servo axis to obtain the left and right position synchronization residuals, so that the difference between the command reference of the two sides, the difference between the zero point calibration and the difference between the process compensation do not participate in the judgment of the torsional conflict of the crossbeam; at the same time, the load state of the left side and the load state of the right side are converted into the left equivalent load and the right equivalent load under the same mechanical scale; when the independent load sensor and the servo torque feedback exist at the same time, the corresponding side equivalent load is formed according to the fusion weight determined by the standard load test record or the sensor calibration record, thereby obtaining the double-sided equivalent load difference used to characterize the uneven force on the left and right sides.

7. The servo bending machine buffer limit control method according to claim 1, characterized in that, The specific operation for generating the torsional conflict state and synchronous deviation source results of the crossbeam is as follows: Based on the current slider height, mold installation position, and bending length setting, select or interpolate the current crossbeam differential stiffness from the crossbeam stiffness calibration data, and convert the equivalent load difference on both sides into the equivalent relative displacement of the crossbeam; determine the position load consistency residual by comparing the equivalent relative displacement of the crossbeam with the left and right position synchronous residuals; when the left and right position synchronous residuals are within the allowable range of synchronous error, the equivalent load difference on both sides exceeds the current working condition baseline difference, and the position load consistency residual reaches the residual establishment benchmark, the torsional conflict state of the crossbeam is generated. The current working condition baseline difference is formed by the historical qualified bending records of the same type. If the historical records are insufficient, they are formed by the standard specimen off-center bending test records, no-load synchronous downward test records, or equipment factory calibration records; then, combined with the state of the unilateral limit arriving first, the synchronous deviation source results are classified into normal off-center load synchronous difference, unilateral limit arriving first, crossbeam torsional conflict state, or composite source.

8. The servo bending machine buffer limit control method according to claim 1, characterized in that, The specific operation for generating compensation gating results is as follows: the synchronous deviation source result is converted into a gating constraint on the synchronous catching-up compensation action on both sides; when the synchronous deviation source result is normal off-center load synchronous difference, the predetermined range of action of the synchronous catching-up compensation action on both sides is maintained; when the synchronous deviation source result is that the limit on one side arrives first, a convergence gating is applied to the compensation trend of the first-arriving side towards the target limit, and the following action of the non-arriving side is jointly constrained by the remaining distance of the limit on the non-arriving side and the upper limit of the terminal buffer speed; when the synchronous deviation source result is the crossbeam under torsional conflict state, the action ratio of the synchronous catching-up compensation action on both sides is converged and corrected, and the common downward speed of both sides is converged synchronously; when the synchronous deviation source result is a composite source, the crossbeam under torsional conflict state is taken as the priority constraint in the compensation gating result.

9. The servo bending machine buffer limit control method according to claim 1, characterized in that, The specific operation of differential buffer limit control is as follows: the final speed commands of the left and right servo axes are generated in the speed control domain. The final speed commands are jointly determined by the basic buffer speed, the synchronous speed correction amount after being limited by the compensation gating result, and the torsional conflict speed correction amount formed according to the torsional conflict state of the crossbeam. In the state where the single-sided limit arrives first, the downward approach speed of the first-arriving side converges according to the compensation gating result, and the non-arriving side approaches the corresponding target limit reference at a speed not exceeding the upper limit of the terminal buffer speed. In the state where the crossbeam is under torsional conflict, the high load side and the low load side are determined according to the equivalent load difference between the two sides. The continued approach trend of the high load side is converged and corrected, and the low load side follows within the upper limit of the terminal buffer speed. When the remaining distance of the limit switch on either side is less than the limit switch confirmation retention distance, the speed command in the target limit switch direction on that side is set to zero and the limit switch holding state is entered.

10. A servo bending machine buffer limit control system, employing the servo bending machine buffer limit control method as described in any one of claims 1-9, characterized in that, include: The terminal observation construction module acquires bilateral operation observation information during the approach process of the bending terminal, corrects and generates bilateral target limit references by using the side limit reference fusion method, converts the actual positions of both sides into the left limit remaining distance and the right limit remaining distance in the unified downlink coordinate, collects the velocity attenuation, load establishment and position following changes of both sides, forms the single-sided terminal approach descriptive quantity and the bilateral difference descriptive quantity, and generates bilateral terminal approach observation results. The single-sided first-arrival recognition module generates terminal approach stage labels for the left and right servo axes based on the observation results of the two-sided terminal approach. The two-sided stage difference quantity is formed by the two-sided terminal approach stage labels and combined with the two-sided difference description quantity to identify the single-sided limit first-arrival state. The synchronization deviation source explanation module, based on the single-sided limit arrival state and the observation results of the double-sided terminal approach, subtracts the left and right command position difference from the actual left and right position difference to form the left and right position synchronization residual, and forms the double-sided equivalent load difference from the load state of both sides. The double-sided equivalent load difference is converted into the equivalent relative displacement of the beam through the beam stiffness calibration data, and the position load consistency residual is formed by the equivalent relative displacement of the beam and the left and right position synchronization residual, generating the torsional conflict state of the beam and the synchronization deviation source result; The compensation gating control module generates compensation gating results based on the source of synchronization deviation and the torsional conflict state of the crossbeam. It uses the compensation gating results to limit the synchronous leveling compensation action on both sides, executes differentiated buffer limit control, and outputs differentiated buffer limit control results.

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