A method for improving and controlling the quality of steel coils

Abstract

This invention belongs to the field of steel coil production technology. It provides a method for improving and controlling the quality of steel coils, including: collecting data on the coil expansion and contraction status, unloading trolley position, coiler speed, and rolling speed to determine whether the steel coil has entered the coil change preparation stage; continuously monitoring the tension before the last stand, coiling tension, tension roll motor load, and strip speed to assess the risk of tension loss and accumulation and predict the accumulation length; after triggering a risk alarm, activating a looper detection device to dynamically adjust the tension roll torque through PID control, feedforward compensation, and zone control to maintain the actual accumulation height within the target range; collecting the new coil diameter expansion completion signal and tension building command, predicting tension impact, and adopting a phased incremental tension building strategy. This invention achieves active suppression of tension fluctuations throughout the coil change process, effectively solving the problems of tension loss and accumulation and tension impact during coil change, and significantly improving the thickness accuracy and surface quality of the steel coil head.

Description

Technical Field

[0001] This invention belongs to the field of steel coil production technology, specifically a method for improving and controlling the quality of steel coils. Background Technology

[0002] In the continuous production of cold-rolled strip steel, coil changing is an unavoidable process. After coiling a steel coil, a coil change operation is required, involving unwinding, loading a new drum, and re-establishing tension. Under this specific condition, traditional tension control systems face a dilemma: during coil change, the coiling tension drops sharply from the set value to zero, while the tension before the last stand cannot be unloaded in time due to the lag in the adjustment mechanism, resulting in loose accumulation of strip steel between the tension roller and the coiler; when the new drum starts to establish tension, the accumulated strip steel is instantly straightened, generating a tension impact with a peak value of more than 2.5 times the set value. This impact not only causes scratches and micro-cracks on the strip surface but also leads to excessive fluctuations in strip thickness, and in severe cases, even strip breakage.

[0003] In addition, existing control methods often only optimize a single link and fail to establish a closed-loop strategy for the entire process from roll change identification, risk warning, looper adjustment to tension control, making it difficult to fundamentally solve the problem of tension fluctuation at the moment of roll change.

[0004] Therefore, the present invention provides a method for improving and controlling the quality of steel coils. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for improving and controlling the quality of steel coils, comprising the following steps:

[0007] Step 1: Collect data on the expansion and contraction status of the coil, the position of the unloading trolley, the speed of the coiler, and the rolling speed. By analyzing the changes in the expansion and contraction of the coil and the status of the unloading trolley, accurately determine whether the steel coil has entered the coil change preparation stage.

[0008] Step 2: After entering the roll change preparation stage, continuously monitor the tension before the last frame, the winding tension, the load of the tension roll motor and the strip speed, analyze the tension changes and load fluctuations before and after the tension roll, comprehensively assess the risk of tension loss and accumulation, if there is a risk, start the accumulation amount estimation model to predict the accumulation length and determine whether to trigger a risk alarm.

[0009] Step 3: After the risk alarm is triggered, the looper detection device is put into operation to provide real-time feedback on the actual stacking height of the strip steel, compare it with the target looper range, monitor the rate of change of the stacking height, predict the stacking trend, and dynamically adjust the torque output of the tension roller according to the deviation to ensure that the looper quantity is always maintained within the target looper range.

[0010] Step 4: Collect the new drum expansion completion signal and tensioning command, and evaluate them in conjunction with the current looper quantity status. If it is predicted that direct tensioning will cause tension impact exceeding the safety threshold, a phased and incremental tensioning strategy will be adopted to ensure that the impact peak is controlled within the safe range.

[0011] As a further aspect of the present invention: in step one, the method for collecting the coil expansion / contraction state, the unloading trolley position, the coiler speed, and the rolling speed is as follows:

[0012] Multi-source signals are collected in real time by a sensor network arranged in the winding area. The expansion and contraction status of the drum is collected by a proximity switch installed on the drum drive side and outputs a digital signal of expansion or contraction. The position of the unwinding trolley is detected by a displacement sensor. The winding machine speed is collected in real time by an encoder at the tail of the winding motor and converted into a speed value. The rolling speed is collected by the speed measuring roller encoder of the last stand and outputs the strip wire speed.

[0013] As a further aspect of the present invention: the process of determining whether the steel coil has entered the coil changing preparation stage in step one is as follows:

[0014] Monitor the expansion and contraction status signal. When the signal changes from expansion to contraction, determine that the drum is ready to start unwinding.

[0015] The real-time position of the unloading trolley is compared with the preset coil receiving position threshold. When the position value enters the threshold range and remains stable for more than a set time, it is determined that the unloading trolley is in place. When the three conditions are met simultaneously—the expansion state of the coil changes from expansion to contraction, the position of the unloading trolley is at the coil receiving position, and the rolling speed is higher than the preset minimum speed threshold—it is determined that the steel coil has entered the coil changing preparation stage.

[0016] As a further aspect of the present invention: in step two, the method for continuously monitoring the tension before the last stand, the winding tension, the load on the tension roller motor, and the strip speed is as follows:

[0017] Signals are collected in real time by a sensor network deployed in the cold rolling exit area. The tension before the last stand is collected in real time by a tension meter installed between the last stand and the tension roll group. The coiling tension is collected in real time by a tension meter installed between the tension roll group and the coiler. The load of the tension roll motor is read in real time through the torque feedback interface of the tension roll drive frequency converter. The strip speed is collected by the speed measuring roll encoder of the last stand and the tension roll linear speed, respectively.

[0018] As a further aspect of the present invention: the process of comprehensively assessing the risk of tension loss and accumulation in step two is as follows:

[0019] The tension difference between the front and rear of the tension roller is calculated in real time and the rate of change is monitored. The real-time value and rate of change of the tension roller motor load are monitored. The strip speed difference and integral value between the last stand and the tension roller are calculated.

[0020] The parameters are weighted and summed to obtain the risk value of tension loss and accumulation. The evaluation rules are set to include the risk value reaching a preset threshold, at least two parameters entering an abnormal state and continuously meeting the set time. When both conditions are met, it is determined that there is a risk of tension loss and accumulation.

[0021] As a further aspect of the present invention: In step two, the process of starting the accumulation volume estimation model to predict the accumulation length and determining whether a risk alarm is triggered is as follows: The real-time value of the speed difference between the last frame and the tension roller is input into the accumulation volume estimation model, and the model obtains the predicted value of the accumulation length by integrating the speed difference over time.

[0022] The predicted stacking length is compared with the preset stacking length warning threshold. A risk alarm is triggered when the predicted value reaches the warning threshold.

[0023] The accumulation estimation model is based on historical production data, and the model parameters are verified by actual measurement data.

[0024] As a further aspect of the present invention: in step three, the process of using the looper detection device to provide real-time feedback on the actual stacking height of the strip steel is as follows:

[0025] A laser rangefinder sensor is installed below the strip between the tension roll group and the coiler. The sensor detection area covers the strip stacking area. The signal is collected by setting a sampling period and converted into the actual height value to obtain the actual stacking height of the strip.

[0026] As a further aspect of the present invention: in step three, the process of dynamically adjusting the torque output of the tension roller is as follows:

[0027] Preset target looper range and target value, and calculate in real time the deviation between the actual stacking height and the target value, as well as the rate of change of the stacking height;

[0028] PID control is used to calculate the adjustment amount with the deviation as input. Feedforward compensation is used to predict the trend based on the rate of change of stacking height and to add the adjustment amount. At the same time, differentiated control strategies are adopted according to the different ranges in which the current looper quantity is located.

[0029] The adjustment amount is superimposed on the basic torque setting value and then output to the tension roller drive system.

[0030] As a further aspect of the present invention: the process of acquiring the new drum expansion completion signal and tensioning instruction in step four is as follows:

[0031] The new drum is equipped with a tension limit switch, which outputs a tension completion signal when the drum completes the tensioning action; the tensioning command comes from the winding operation screen or the automatic winding program, and when the tensioning command signal is received, it confirms that the winding machine has entered the tensioning state; at the same time, it calls up the actual stacking height of the strip steel obtained in step three, and records the height value at the moment the tensioning command is issued.

[0032] As a further aspect of the present invention: the process of adopting a phased incremental expansion strategy in step four is as follows:

[0033] Using the current looper quantity, target looper quantity, and set tension value as inputs, the impact prediction model calculates and predicts the peak impact value. When the predicted value exceeds the set threshold, the phased tension building is initiated.

[0034] In the first stage, the winding machine operates at low speed and the tension is set at a low proportion to adjust the loop amount to the target range.

[0035] In the second stage, the take-up speed is increased to medium speed and the tension is increased at a high percentage of the set value in a ramp manner.

[0036] In the third stage, the winding speed is gradually increased to the normal rolling speed and the tension is smoothly applied to the set value, completing the tension building process.

[0037] The beneficial effects of this invention are as follows:

[0038] By constructing a closed-loop optimization system for tension control throughout the entire coil changing process, a complete technical chain from condition identification to control execution is realized. This effectively solves the problems of strip slack accumulation and excessively high impact peaks during subsequent tension building caused by the sudden drop in coiling tension and the lag in tension response before the last stand during coil changing, which are common problems in traditional methods. First, this invention accurately identifies the coil changing preparation stage by real-time acquisition of multi-source signals such as the coil expansion and contraction status and the position of the unloading trolley. Then, by performing single-index trend identification and multi-parameter weighted fusion evaluation on the tension difference before and after the tension roller, the load descent rate, and the cumulative speed difference, a loss-of-tension accumulation risk index and accumulation amount estimation model are constructed. This achieves a leap from qualitative risk judgment to quantitative early warning, providing accurate decision-making basis for subsequent buffer control. Secondly, when a risk alarm is triggered, the present invention uses a looper quantity detection device to provide real-time feedback on the actual strip stacking height. It employs a strategy combining PID control, feedforward compensation, and zoned control to dynamically adjust the tension roll torque output, stabilizing the looper quantity within a preset target range. This prevents strip wrinkling caused by excessive stacking and avoids tension impacts caused by the looper being straightened, significantly reducing the risk of strip breakage and edge cracking during coil changing. Furthermore, the present invention innovatively proposes a phased incremental tension building strategy. By establishing an impact prediction model, it predicts the peak impact of direct tension building based on the current looper quantity and operating parameters at the tension building decision point. When the predicted value exceeds a safety threshold, it automatically switches to a three-stage tension building mode: low-speed looper adjustment, medium-speed tension ramp-up, and full-speed normal rolling. This disperses the originally concentrated impact energy across various stages for a smooth transition, keeping the peak tension impact within a safe range and significantly improving the quality stability and yield of the coil head. Attached Figure Description

[0039] The invention will now be further described with reference to the accompanying drawings.

[0040] Figure 1 This is a flowchart illustrating the steps of a steel coil quality improvement and control method according to an embodiment of the present invention.

[0041] Figure 2 This is a logic diagram of a steel coil quality improvement control method according to an embodiment of the present invention. Detailed Implementation

[0042] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0043] For examples, please refer to Figures 1-2 As shown in the embodiment of the present invention, a method for improving and controlling the quality of steel coils includes the following steps:

[0044] Step 1: Collect data on the expansion and contraction status of the coil, the position of the unloading trolley, the speed of the coiler, and the rolling speed. By analyzing the changes in the expansion and contraction of the coil and the status of the unloading trolley, determine whether the steel coil has entered the coil change preparation stage.

[0045] In step one, the methods for collecting the expansion and contraction state of the roll, the position of the unwinding trolley, the winding machine speed, and the rolling speed can be:

[0046] Multi-source signals are acquired in real time through a sensor network deployed in the winding area, specifically including:

[0047] Drum expansion / contraction status: acquired by a proximity switch or magnetic switch installed on the drum drive side, and output as a digital signal (0 indicates shrinkage, 1 indicates expansion).

[0048] Unloading trolley position: The trolley's position is detected by a displacement sensor or encoder, and the output is an analog or digital signal with an accuracy controlled within ±5mm.

[0049] Winder speed: The speed is collected in real time by the encoder at the tail of the winding motor, which outputs a pulse frequency signal and converts it into a speed value (unit: rpm or m / s).

[0050] Rolling speed: acquired by the speed measuring roller encoder or laser tachometer on the last stand, and output as the strip linear speed (unit: m / s).

[0051] In step one, the process of analyzing the expansion and contraction changes of the winding drum and the status of the unloading car is as follows:

[0052] Monitor the edge changes of the expansion and contraction state signal. When the signal changes from "1" to "0" (i.e. from expansion to contraction), determine that the drum is ready to be unwound.

[0053] The real-time position of the unloading trolley is compared with the preset "receiving position" threshold (e.g., set to within 100mm below the center of the roll). When the position value enters the threshold range and remains stable for more than 0.5 seconds, it is determined that the unloading trolley is in place.

[0054] In step one, the process of determining whether the steel coil has entered the coil change preparation stage is as follows:

[0055] Judgment conditions are set based on the analysis results of the expansion and contraction changes of the drum and the status of the unloading car, specifically including:

[0056] Judgment condition 1: The expansion state of the drum changes from expansion to contraction (i.e., unwinding begins);

[0057] Judgment condition two: The unloading trolley is located at the receiving position (i.e., the trolley is in place);

[0058] Judgment condition 3: The rolling speed is continuously higher than the minimum speed threshold allowed for coil changing (e.g., >10m / s, ensuring that the rolling process is in a high-speed and stable state).

[0059] If all the judgment conditions are met, the steel coil is determined to enter the coil changing preparation stage.

[0060] Understandably, the significance of step one lies in its ability to accurately identify whether a steel coil has entered the coil change preparation stage by real-time acquisition of multi-source signals, including the coil expansion and contraction status, the unloading trolley position, the coiler speed, and the rolling speed, and by analyzing changes in coil expansion and contraction and the unloading trolley status. This step provides accurate operating condition triggering conditions for subsequent tension loss and accumulation risk assessment and tension control, ensuring that the control system activates the corresponding strategy only when intervention is truly needed, avoiding misjudgments and ineffective interventions. It is the foundation and prerequisite for tension control throughout the entire coil change process.

[0061] Step 2: After entering the roll change preparation stage, continuously monitor the tension before the last frame, the winding tension, the load of the tension roll motor and the strip speed, analyze the tension changes and load fluctuations before and after the tension roll, comprehensively assess the risk of tension loss and accumulation, if there is a risk, start the accumulation amount estimation model to predict the accumulation length and determine whether to trigger a risk alarm.

[0062] In step two, the method for continuously monitoring the tension before the last stand, the winding tension, the load on the tension roller motor, and the strip speed can be:

[0063] Multi-source signals are acquired in real time through a sensor network deployed in the cold rolling exit area, specifically including:

[0064] Tension before the last frame: It is collected in real time by a tension meter (tension measuring roller) installed between the last frame and the tension roller group. The output is an analog signal (unit: kN) and converted into the actual tension value. The sampling period is set to 10ms.

[0065] Winding tension: is collected in real time by a tension meter installed between the tension roller group and the winding machine, and compared with the tension before the end frame;

[0066] Tension roller motor load: The actual torque value of the motor (unit: % or Nm) is read in real time through the torque feedback interface of the tension roller drive frequency converter, reflecting the current load size of the tension roller;

[0067] Strip speed: The strip speed is collected by the speed measuring roller encoder and the tension roller motor encoder of the last stand, respectively, to obtain the linear speed at the exit of the last stand and the linear speed of the tension roller (unit: m / s), which is used to calculate the front and rear speeds;

[0068] In step two, the process of analyzing the tension changes and load fluctuations before and after the tension roller, and comprehensively assessing the risk of tension loss and buildup, is as follows:

[0069] Perform anomaly trend identification for single parameters (including tension difference before and after the tension roller, load descent rate, and cumulative speed difference), specifically including:

[0070] The tension difference ΔT before and after the tension roller is calculated in real time as T_before the last stand - T_winding, and the rate of change of ΔT d(ΔT) / dt is monitored. When ΔT continues to increase and exceeds the preset threshold (the rated maximum tension difference ΔT), the value is recorded. max If the tension imbalance is increasing (60% of the original value), and d(ΔT) / dt remains positive for more than the set time (300ms), it is determined that the tension imbalance is intensifying.

[0071] Monitor the real-time value and rate of change of the load on the tension roller motor. When the load value drops rapidly (the rate of drop ΔP > 5% / s) and the duration is > 200ms, it is determined that there is a risk of tension loss and accumulation.

[0072] Calculate the strip speed difference Δv between the last stand and the tension roll = v_last stand - v_tension roll. When Δv is continuously positive (i.e., the speed of the last stand is faster than that of the tension roll) and the integral of the speed difference exceeds the threshold (50mm), it is determined that the strip is accumulating.

[0073] For example, the identification of abnormal trends for single parameters (including the tension difference before and after the tension roller, the load descent rate, and the cumulative speed difference) is shown in Table 1 below:

[0074] Table 1: Identification and Judgment of Abnormal Trends in Single Parameters;

[0075] parameter Calculation method Trend Anomaly Detection Tension difference between front and back of tension roller ΔT = T_before the last rack - T_winding ΔT continues to increase and its absolute value exceeds 60% of ΔT_max, while d(ΔT) / dt>0 persists for 300ms. Load descent rate ΔP=d(P_tension roller) / dt ΔP > 5% / s and duration > 200ms Accumulated speed difference Δv = v_last frame - v_tension roller Δv>0 and ∫Δv·dt>50mm (cumulative accumulation)

[0076] If any single parameter exhibits an abnormal trend, a risk assessment of tension loss and accumulation is conducted, specifically as follows:

[0077] The weighted summation of the tension difference before and after the tension roller, the load descent rate, and the cumulative speed difference is calculated using the following formula:

[0078]

[0079] Where R represents the risk of tension buildup, and ΔT max ΔP is the rated maximum tension difference. max L is the rated maximum load descent rate. max For the maximum allowable stacking length (e.g., 300 mm), α, β, and γ are weighting coefficients;

[0080] It should be noted that the weighting coefficients α, β, and γ are set as follows: historical data from N (e.g., 50) roll change processes are collected, including: whether an actual tension loss and accumulation accident occurred each time (manually labeled, 0 / 1), and ΔT / ΔT for each process. max |ΔP| / ΔP max ,∫Δv·dt / Lmax The real-time curves were used to calculate the Pearson correlation coefficients between the three parameters and the accident label: if the correlation coefficient of ΔT was the highest (e.g., 0.85), it indicated that the tension difference was the best predictor of the accident, and α should be the largest; if the correlation coefficient of |ΔP| was low (e.g., 0.45), it indicated that the predictive ability of load reduction was weak, and β should be small. Logistic regression was performed with the accident label as the dependent variable Y and the three parameters as independent variables X1, X2, and X3. The coefficients obtained from the regression are the optimal weights. The maximum likelihood estimation is used to solve the problem, which maximizes the accuracy of the model in predicting historical accidents.

[0081] Establish rules for assessing the risk of tension buildup, specifically including:

[0082] Assessment Rule 1: The risk value of tension loss and accumulation, R, is ≥ 0.7;

[0083] Evaluation Rule 2: At least two single parameters have entered an abnormal trend state;

[0084] Evaluation Rule 3: Evaluation Rule 1 and Evaluation Rule 2 must be met continuously for at least 200ms (excluding transient interference);

[0085] If all evaluation rules are met, it indicates that there is a risk of tension buildup.

[0086] In step two, the process of starting the accumulation volume estimation model to predict the accumulation length and determining whether a risk alarm is triggered is as follows:

[0087] The current real-time data is used as input to the accumulation estimation model, specifically including: the speed difference Δv between the last stand and the tension roll (real-time value), the risk value of tension loss accumulation R, the strip specifications (thickness, width) and the current tension status;

[0088] The core of the stacking volume estimation model is to perform time integration of the velocity difference: L_stacked=∫(v_last frame-v_tension roller)dt, the integration start time is the risk judgment moment, and the integration step size is synchronized with the sampling period (10ms).

[0089] The model updates the predicted stack length value L_pred every 100ms and compares L_pred with a preset stack length warning threshold (e.g., 200mm):

[0090] If L_pred reaches the preset stack length warning threshold, a risk alarm will be triggered; otherwise, it will not be triggered.

[0091] It should be noted that the process of establishing the accumulation volume estimation model is as follows:

[0092] The physical process of tension loss and accumulation is analyzed, and the kinematic relationship between the strip and the tension roll and coiler is established. The root cause of accumulation is the mismatch between the speed of the last stand and the speed of the tension roll. The accumulation length L has an integral relationship with the speed difference Δv: L = ∫Δv·dt. Simultaneously, considering the elastic deformation of the strip, a correction coefficient k_elastic is introduced to reflect the elastic elongation of the strip caused by tension changes.

[0093] Data from multiple roll-changing operations during historical production were collected, including last stand speed, tension roll speed, tension variation curves, and actual stacking length (obtainable via industrial camera or manual measurement). A sample database was established, and a system identification method was used to estimate the unknown parameters in the mechanistic model. Using the measured stacking length as output and the speed difference integral and tension variation as input, correction coefficients and dynamic response parameters were determined using the least squares method or maximum likelihood estimation to minimize the error between the model output and the actual value.

[0094] The model is validated using test data that was not used in training. Prediction errors (such as root mean square error RMSE and mean absolute percentage error MAPE) are calculated to ensure that the model accuracy meets the control requirements (such as prediction error <10%), and finally the accumulation volume estimation model is obtained.

[0095] Understandably, the significance of step two lies in the following: After entering the roll change preparation stage, by continuously monitoring key parameters such as the tension before the last stand, the winding tension, the load on the tension roll motor, and the strip speed, and analyzing the tension changes and load fluctuation characteristics before and after the tension roll, the risk of tension loss and accumulation can be comprehensively assessed. When a risk is identified, the accumulation amount estimation model is activated to predict the accumulation length and trigger a risk alarm, realizing a closed loop from risk identification to risk quantification. This provides accurate decision-making basis for subsequent buffer control and effectively prevents strip breakage and edge cracking accidents caused by tension loss and accumulation.

[0096] Step 3: If a risk alarm is triggered, the looper detection device will be activated to provide real-time feedback on the actual stacking height of the strip steel. The actual stacking height will be compared with the preset target looper range. At the same time, the rate of change of the stacking height will be monitored to predict the stacking trend. The torque output of the tension roller will be dynamically adjusted according to the deviation to keep the actual stacking height within the target looper range, thus preventing excessive stacking and avoiding the looper from being straightened.

[0097] In step three, the process of using the looper measurement device to provide real-time feedback on the actual stacking height of the strip steel is as follows:

[0098] A laser rangefinder or ultrasonic sensor is used as the looper measurement device, with a range of 0-1000mm, an accuracy requirement of ±2mm, and a response time of ≤20ms. The sensor is installed below or above the strip between the tension roll group and the coiler, perpendicular to the strip surface, and the detection area covers the entire range where the strip may accumulate. The sampling period is set to 10-20ms. The electrical signal output by the sensor is converted into the actual physical height value to obtain the actual accumulation height H_actual of the strip.

[0099] In step three, the process of dynamically adjusting the torque output of the tension roller is as follows:

[0100] The preset target looper range is [H_min, H_max], for example, H_min=150mm, H_max=250mm, and the target value H_ref=200mm. The preset basis is: lower limit H_min: to ensure that the looper will not be straightened due to being too small (avoiding tension impact), upper limit H_max: to ensure that the looper will not pile up and touch the ground due to being too large (avoiding wrinkles or scratches).

[0101] The deviation e = H_actual - H_ref and the relative deviation e_rel = e / (H_max - H_min) are calculated in real time.

[0102] Calculate the rate of change of the stacking height: vH = dH_actual / dt;

[0103] If vH>0 and e>0, it means that the accumulation is intensifying and has exceeded the target.

[0104] If vH<0 and e<0, it means that the loop is being straightened and has already fallen below the target.

[0105] If |vH| is large (e.g., >20mm / s), it indicates a strong trend and an early response is required;

[0106] The torque output of the tension roller is dynamically adjusted by combining PID control, feedforward compensation, and zone control. Specifically, this includes:

[0107] PID feedback control: Using the deviation e as input, calculate the PID output u_PID.

[0108]

[0109] Wherein, Kp is the proportional term (0.5) to make the loop quickly return to the target range, Ki is the integral term (0.1) to eliminate steady-state deviation (such as continuous deviation from the target), and Kd is the differential term (0.05) to suppress overshoot and prevent loop oscillation;

[0110] The PID output serves as a correction factor for the tension roller torque and is added to the base torque setpoint.

[0111]

[0112] in, For the torque setpoint, The torque base setting value;

[0113] Feedforward compensation: Feedforward compensation is performed based on vH to respond to trend changes in advance.

[0114]

[0115] Wherein, the feedforward coefficient K ff Determined based on strip specifications, if vH > 0 (accelerated accumulation), u FF When the value is negative, appropriately reduce the torque (relax the tension roller) to slow down accumulation. When vH < 0 (the looper decreases), u FF If positive, appropriately increase the torque (tensioning the tension roller) to slow down the straightening process;

[0116] As shown in Table 2, a differentiated control strategy is adopted based on the current range of the looper quantity:

[0117] Table 2: Differentiated Control Strategies;

[0118] interval Looping range Control strategy safe zone H_min ≤ H ≤ H_max PID control is normal, maintaining looper stability. Warning Zone H < H_min or H > H_max Increase PID gain for faster callback Danger Zone H < H_min - Δ (warning margin) or H > H_max + Δ Strong intervention: Torque limit is rapidly adjusted, simultaneously triggering an operator alarm. Extreme Zone H < H_min-2Δ or H > H_max+2Δ Emergency stop (belt breakage protection)

[0119] Understandably, the significance of step three lies in the following: when a risk alarm is triggered, the actual strip stacking height is fed back in real time through the looper measurement device and compared with the preset target range. Simultaneously, the rate of change in stacking height is monitored to predict trends. A strategy combining PID control, feedforward compensation, and zone control is used to dynamically adjust the tension roller torque output, ensuring the actual stacking height remains within a safe range. This step achieves proactive intervention and closed-loop control of tension loss during stacking, preventing both over-stacking causing wrinkles and straightening of the looper, thus avoiding tension shocks.

[0120] Step 4: Collect the new drum expansion completion signal and tensioning command, and evaluate them in conjunction with the current actual stacking height. If it is predicted that direct tensioning will generate tension impact exceeding the safety threshold, a phased and incremental tensioning strategy will be adopted to control the peak tension impact within a safe range.

[0121] In step four, the process of acquiring the new drum expansion completion signal and tensioning command is as follows:

[0122] The new drum is equipped with a tension limit switch (proximity switch or magnetic switch). When the drum's mechanical structure completes the expansion action and reaches the normal working diameter, the switch outputs a digital signal "1" (expansion complete). The signal status is scanned every 10ms. At the same time, the drum pressure sensor signal is collected to confirm that the expansion hydraulic pressure has reached the set value (e.g., ≥15MPa), serving as an auxiliary verification of expansion completion. The tension building command comes from the winding operation screen or the automatic winding program. When the operator clicks the "tension building" button or the program automatically enters the tension building stage, the tension building command signal (digital, 1 is valid) is received. At the same time, the winding speed setpoint is collected to confirm that the winding machine has entered the speed control mode and is ready to build tension.

[0123] In step four, the current actual stacking height is evaluated as follows:

[0124] Call the real-time feedback value H_actual of the looper quantity detection device in step 3 (the sampling time is synchronized with the tensioning command), and at the same time obtain the rate of change of the stacking height vH=dH / dt; at the moment before the tensioning command is issued (such as 100ms before), record the H_actual (the looper height value at the instant before the tensioning command is issued) and vH at that time;

[0125] In step four, the process of predicting that direct tensioning will generate tensile impacts exceeding the safety threshold is as follows:

[0126] Using the looper quantity H_actual, the target looper quantity H_target (taken as the target value of 200mm from step three), strip steel specifications (thickness, width, grade), and the set tension value as inputs, an impact prediction model is established:

[0127]

[0128] in, To reach the peak, To set the tension value, K is calibrated using historical impact data, with a value of 0.5, and ΔH = H_actual - H_target;

[0129] Input the current looper quantity, target looper quantity, strip steel specifications (thickness, width, grade), and set tension value. Output the peak impact value. If the peak impact value is greater than the peak impact value threshold (1.5 times the set tension), it means that a phased increasing tension building strategy is required; otherwise, it is not required.

[0130] In step four, the process of using a phased, incremental tension-building strategy to control the peak tension impact within a safe range is as follows:

[0131] Preparation phase for setting up the loop (low-speed release / absorption of loops): Adjust the current loop quantity H_actual to a range close to the target loop quantity H_target, specifically including:

[0132] The coiler operates at an extremely low speed (e.g., 0.5~1.0 m / s), lower than the normal rolling speed. The tension setting is 20%~30% of the normal value (e.g., 4~6 kN when T_set=20 kN). The running direction is determined based on the current deviation between H_actual and H_target.

[0133] If H_actual > H_target (excessive accumulation): the coiler runs at low speed in the forward direction, slowly tightening the strip and consuming excess looper;

[0134] If H_actual < H_target (insufficient looper): the coiler reverses or holds, waiting for material to replenish the looper (must be coordinated with the speed of the last frame).

[0135] The conditions for the end of the preparation stage for the establishment of the facility are: the looper quantity enters the target range: H_min≤H_actual≤H_max (e.g., 150-250mm and the looper change rate |vH|<5mm / s (tending to stabilize);

[0136] During the medium-speed tension building phase (tension ramp-up), the tension is gradually increased from a low value to near the target value while maintaining looper stability. This specifically includes:

[0137] The winding speed is increased to 3~5 m / s (still lower than the normal speed), the tension is increased in a ramp manner, the rate of increase is 5~10kN / s (or 10% / second of the rated tension), the looper quantity closed-loop control is put into operation (the PID adjustment in step 3 continues to run), the torque is finely adjusted in real time to maintain the stability of the looper, and the actual tension value T_actual and looper quantity H_actual are monitored to ensure that the two change synchronously without sudden changes;

[0138] The conditions for ending the medium-speed tensioning stage are: the tension reaches 80%~90% of the set value (e.g., T_set=20kN, reaching 16~18kN) and the looper quantity is stable within the target range;

[0139] The full-speed tension building stage (transition to normal rolling) smoothly transitions to normal rolling, completing the tension building process, specifically including:

[0140] The coiling speed is gradually increased to the normal rolling speed (matching the speed of the last stand), and the tension is smoothly loaded from 80%~90% to 100% of the set value at a loading rate of 2~5 kN / s (slower than stage 2). The looper quantity PID adjustment continues to run, and the target value is maintained at 200mm. At the same time, the tension before the last stand is gradually increased to the normal value to complete the establishment of the two-stage tension.

[0141] The conditions for ending the full-speed tensioning stage are: tension reaches 100% of the set value, stable operation lasts ≥2 seconds, looper quantity is stable within the target range, and speed is synchronized with the last stand;

[0142] Understandably, the significance of step four lies in: after acquiring the signal indicating the completion of the new coil's diameter expansion and the tensioning command, an assessment is made based on the current actual stacking height. An impact prediction model is used to determine whether direct tensioning will generate a tension impact exceeding the safety threshold. If the predicted impact exceeds the safety threshold, a phased, incremental tensioning strategy is adopted, smoothly transitioning through three stages: low-speed looper adjustment, medium-speed tension ramp-up, and full-speed normal rolling. This step effectively suppresses the peak tension impact at the moment of coil change, ensuring the surface quality and thickness stability of the strip, and significantly reducing product quality losses during the coil change process.

[0143] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving and controlling the quality of steel coils, characterized in that: Includes the following steps: Step 1: Collect data on the expansion and contraction status of the coil, the position of the unloading trolley, the speed of the coiler, and the rolling speed. By analyzing the changes in the expansion and contraction of the coil and the status of the unloading trolley, accurately determine whether the steel coil has entered the coil change preparation stage. Step 2: After entering the roll change preparation stage, continuously monitor the tension before the last frame, the winding tension, the load of the tension roll motor and the strip speed, analyze the tension changes and load fluctuations before and after the tension roll, comprehensively assess the risk of tension loss and accumulation, if there is a risk, start the accumulation amount estimation model to predict the accumulation length and determine whether to trigger a risk alarm. Step 3: After the risk alarm is triggered, the looper detection device is put into operation to provide real-time feedback on the actual stacking height of the strip steel, compare it with the target looper range, monitor the rate of change of the stacking height, predict the stacking trend, and dynamically adjust the torque output of the tension roller according to the deviation to ensure that the looper quantity is always maintained within the target looper range. Step 4: Collect the new drum expansion completion signal and tensioning command, and evaluate them in conjunction with the current looper quantity status. If it is predicted that direct tensioning will cause tension impact exceeding the safety threshold, a phased and incremental tensioning strategy will be adopted to ensure that the impact peak is controlled within the safe range.

2. The method for improving and controlling the quality of steel coils according to claim 1, characterized in that: In step one, the methods for collecting the expansion and contraction state of the coil, the position of the unloading trolley, the coiler speed, and the rolling speed are as follows: Multi-source signals are collected in real time by a sensor network arranged in the winding area. The expansion and contraction status of the drum is collected by a proximity switch installed on the drum drive side and outputs a digital signal of expansion or contraction. The position of the unwinding trolley is detected by a displacement sensor. The winding machine speed is collected in real time by an encoder at the tail of the winding motor and converted into a speed value. The rolling speed is collected by the speed measuring roller encoder of the last stand and outputs the strip wire speed.

3. The method for improving and controlling the quality of steel coils according to claim 2, characterized in that: In step one, the process of determining whether the steel coil has entered the coil change preparation stage is as follows: Monitor the expansion and contraction status signal. When the signal changes from expansion to contraction, determine that the drum is ready to start unwinding. The real-time position of the unloading trolley is compared with the preset coil receiving position threshold. When the position value enters the threshold range and remains stable for more than a set time, it is determined that the unloading trolley is in place. When the three conditions are met simultaneously—the expansion state of the coil changes from expansion to contraction, the position of the unloading trolley is at the coil receiving position, and the rolling speed is higher than the preset minimum speed threshold—it is determined that the steel coil has entered the coil changing preparation stage.

4. The method for improving and controlling the quality of steel coils according to claim 1, characterized in that: In step two, the method for continuously monitoring the tension before the last stand, the winding tension, the load on the tension roller motor, and the strip speed is as follows: Signals are collected in real time by a sensor network deployed in the cold rolling exit area. The tension before the last stand is collected in real time by a tension meter installed between the last stand and the tension roll group. The coiling tension is collected in real time by a tension meter installed between the tension roll group and the coiler. The load of the tension roll motor is read in real time through the torque feedback interface of the tension roll drive frequency converter. The strip speed is collected by the speed measuring roll encoder of the last stand and the tension roll linear speed, respectively.

5. The method for improving and controlling the quality of steel coils according to claim 4, characterized in that: In step two, the process of comprehensively assessing the risk of tension buildup is as follows: The tension difference between the front and rear of the tension roller is calculated in real time and the rate of change is monitored. The real-time value and rate of change of the tension roller motor load are monitored. The strip speed difference and integral value between the last stand and the tension roller are calculated. The weighted summation of the parameters yields the risk value of tension stacking. The assessment rules include the risk value reaching a preset threshold, at least two parameters entering an abnormal state and continuously meeting the set time. When both conditions are met, it is determined that there is a risk of tension accumulation.

6. The method for improving and controlling the quality of steel coils according to claim 5, characterized in that: In step two, the process of starting the accumulation volume estimation model to predict the accumulation length and determining whether a risk alarm is triggered is as follows: the real-time value of the speed difference between the last frame and the tension roller is input into the accumulation volume estimation model, and the model obtains the predicted value of the accumulation length by integrating the speed difference over time. The predicted stacking length is compared with the preset stacking length warning threshold. A risk alarm is triggered when the predicted value reaches the warning threshold. The accumulation estimation model is based on historical production data, and the model parameters are verified by actual measurement data.

7. The method for improving and controlling the quality of steel coils according to claim 1, characterized in that: In step three, the process of using the looper measurement device to provide real-time feedback on the actual stacking height of the strip steel is as follows: A laser rangefinder sensor is installed below the strip between the tension roll group and the coiler. The sensor detection area covers the strip stacking area. The signal is collected by setting a sampling period and converted into the actual height value to obtain the actual stacking height of the strip.

8. The method for improving and controlling the quality of steel coils according to claim 7, characterized in that: In step three, the process of dynamically adjusting the torque output of the tension roller is as follows: Preset target looper range and target value, and calculate in real time the deviation between the actual stacking height and the target value, as well as the rate of change of the stacking height; PID control is used to calculate the adjustment amount with the deviation as input. Feedforward compensation is used to predict the trend based on the rate of change of stacking height and to add the adjustment amount. At the same time, differentiated control strategies are adopted according to the different ranges in which the current looper quantity is located. The adjustment amount is superimposed on the basic torque setting value and then output to the tension roller drive system.

9. The method for improving and controlling the quality of steel coils according to claim 1, characterized in that: In step four, the process of acquiring the new drum expansion completion signal and tensioning instruction is as follows: The new drum is equipped with a tension limit switch, which outputs a tension completion signal when the drum completes the tensioning action; the tensioning command comes from the winding operation screen or the automatic winding program, and when the tensioning command signal is received, it confirms that the winding machine has entered the tensioning state; at the same time, it calls up the actual stacking height of the strip steel obtained in step three, and records the height value at the moment the tensioning command is issued.

10. The method for improving and controlling the quality of steel coils according to claim 9, characterized in that: In step four, the process of adopting a phased incremental expansion strategy is as follows: Using the current looper quantity, target looper quantity, and set tension value as inputs, the impact prediction model calculates and predicts the peak impact value. When the predicted value exceeds the set threshold, the phased tension building is initiated. In the first stage, the winding machine operates at low speed and the tension is set at a low proportion to adjust the loop amount to the target range. In the second stage, the take-up speed is increased to medium speed and the tension is increased at a high percentage of the set value in a ramp manner. In the third stage, the winding speed is gradually increased to the normal rolling speed and the tension is smoothly applied to the set value, completing the tension building process.

Images