Method for controlling tail deviation of hot-rolled thin strip steel
By employing a dual closed-loop control strategy, combined with information on looper angle and rolling force deviation, the problem of tail deviation in hot-rolled thin strip steel was solved, achieving rapid and precise automated control, reducing quality defects such as tail breakage, and improving production stability and yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-03-24
AI Technical Summary
Existing technologies for hot-rolled thin strip steel tail rolling processes suffer from slow response, low adjustment accuracy, high labor intensity, poor consistency, and complex and costly automatic control schemes, leading to quality problems such as strip centerline deviation, tail warping, and breakage.
A dual closed-loop control strategy is adopted, which combines looper angle information and rolling force deviation information to construct a looper control module and a rolling force adjustment module. Through real-time collaborative control, the tension at the tail of the strip is smoothly transitioned and deviation is corrected, including the dynamic adjustment of looper angle and rolling force deviation.
It significantly reduced the incidence of quality defects such as tail-end crushing, improved production stability and yield, and achieved rapid and precise automated control.
Smart Images
Figure CN121715426A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of automated control technology for the strip steel rolling process, specifically to a method for controlling tail deviation of hot-rolled thin-gauge strip steel. Background Technology
[0002] During the rolling of strip steel at the tail end of a hot strip mill, the successive throwing of steel from upstream stands causes drastic changes in strip tension, easily leading to quality problems such as abnormal looper operation, strip centerline deviation, tail-end warping, and even breakage. Existing technologies mainly rely on manual intervention based on operator experience, which suffers from drawbacks such as slow response, low adjustment precision, high labor intensity, and poor consistency. Some automatic control schemes only use single signals such as rolling force deviation for judgment, failing to fully consider the dynamic characteristics of the looper system and the tension change process, easily causing over-adjustment or mis-adjustment, resulting in unstable control effects. Furthermore, while some machine vision-based solutions can directly detect deviation, the systems are complex and costly, hindering large-scale application on existing production lines. Therefore, there is an urgent need for an automated control method that is responsive, precise, easy to implement, and low-cost to stabilize the tail-end rolling process and improve the yield and product quality of thin-gauge strip steel. Summary of the Invention
[0003] (a) Technical problems to be solved The technical problem to be solved by this invention is to provide a method for controlling the tail deviation of hot-rolled thin strip steel. This method utilizes looper angle information and rolling force deviation information in real time before and after the steel is thrown from the upstream stand to construct a dual closed-loop control strategy that includes a looper control module and a rolling force adjustment module. This achieves a smooth transition of tension at the tail of the strip steel and automatic correction of deviation, thereby significantly reducing the incidence of quality defects such as tail breakage and improving production stability and product yield.
[0004] (II) Technical Solution To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a method for controlling tail deviation of hot-rolled thin strip steel, characterized by comprising the following steps: S1. Before the steel is thrown from the upstream stand of the hot strip finishing mill, record the initial rolling force deviation of the current stand. ,in =F operating side - F transmission side; S2. After receiving the steel throwing signal from the upstream stand, start the tail leveling program, which includes a looper control module and a rolling force adjustment module; S3. The looper control module performs the following operations: (1) Based on the current thickness of the strip, the basic speed compensation value is preset, and the mill speed is reduced within 0.3 seconds to assist the looper to fall back; (2) Record the actual angle θ1 of the loop at the end of the loop control and compare it with the set reference angle θref1, wherein the value range of θref1 is 14°~18°; (3) Record the actual angle θ2 of the looper when the rolling mill throws the steel, and compare it with the set reference angle θref2. The value range of θref2 is 12°~16°. (4) Based on the comparison results of θ1 and θref1, dynamically adjust the control time of the small sleeve of the next piece of steel and the foundation speed compensation value; (5) Based on the comparison results of θ2 and θref2, dynamically adjust the starting control time for the next piece of steel to be dropped into the sleeve; S4. The rolling force adjustment module performs the following operations: (1) Real-time calculation of rolling force deviation change ; (2) When |Δ(ΔF)| exceeds the set threshold, determine the direction of strip deviation and output the roll gap leveling amount; (3) Stop adjusting when the leveling amount reaches the preset maximum allowable range or when the current frame throws steel, and clear the output to zero after the current frame throws steel.
[0005] As an improvement, the adjustment range of the basic speed compensation value is 0 to 5%, the adjustment range of the small sleeve control time is 0.3 to 0.8 seconds, and the adjustment range of the sleeve drop start control time is 0.1 to 0.3 seconds.
[0006] As an improvement, the original looper angle height control output is expressed as follows: ; The correction amount for its programmable slope limiting is: ; Where e(t) is the looper angle deviation (the difference between the actual angle and the set reference angle); K p K i These are the proportional and integral gains of the PI controller, respectively. Δu(t) is the feedforward correction amount, the absolute value of which is no greater than ΔUmax (≤5% of the reference speed compensation value), and is corrected according to a fixed slope |dΔu / dt|≤ΔUmax / T, where T correction ∈ [0.1s, 0.3s]. It is linearly accumulated cycle by cycle (PLC scan cycle 30ms) until the target correction amount is reached, so as to achieve smooth fine adjustment of "small sleeve control time" or "sleeve start-up time".
[0007] As an improvement, in the rolling force adjustment module: the set threshold is 50kN. If Δ(ΔF) < -50kN, the operating side roll gap is raised and the transmission side roll gap is pressed; if Δ(ΔF) > +50kN, the operating side roll gap is pressed and the transmission side roll gap is raised.
[0008] As an improvement, the calculation method for the roll gap leveling amount in the rolling force adjustment module is: ΔS=Δ(ΔF) / Km, where Km is the mill stiffness.
[0009] As an improvement, the adjustment speed of the roll gap leveling action is limited to the maximum adjustment speed set by the frame, and is performed in an integral manner, accumulating cycle by cycle.
[0010] As an improvement, the method is characterized in that it is applicable to the F1 to F7 stands of the hot strip mill finishing mill, and control is preferentially applied to the last three stands.
[0011] As an improvement, the method achieves forced centering of the strip before steel throwing through the fast small sleeve function during the looper control stage, and immediately starts rolling force correction control after steel throwing on the upstream stand.
[0012] As an improvement, in step S3: If θ1 > θref1, the control time of the small sleeve is increased by 0.03 to 0.1 s and the base speed compensation value is increased for the next piece of steel; if θ1 < θref, the control time of the small sleeve is decreased by 0.03 to 0.1 s and the base speed compensation value is decreased. If θ2 > θref2, the starting control time for the next piece of steel is increased by 0.03 to 0.1 s; if θ2 < θref2, the starting control time for the next piece of steel is decreased by 0.03 to 0.1 s.
[0013] As an improvement, the set threshold can be adjusted online within the range of 0 to 200 kN.
[0014] (III) Beneficial Effects The advantages of this invention compared to existing technologies are as follows: By collecting rolling force deviation and looper angle in real time before and after strip throwing at the upstream stand, a dual closed-loop strategy of looper control module and rolling force adjustment module is constructed to achieve tail tension stability and automatic correction of strip centering, significantly reducing the tail breakage rate. Looper adjustment is completed before strip throwing at the mill, ensuring forced centering of the strip during the throwing process. Through optimized small looper control, the small looper control time is shortened as much as possible, achieving rapid and continuous looper descent. During the descent, the tension gradually increases to achieve strong centering before strip throwing. After strip throwing at the tail of the mill, the strip loses the centering effect of tension and is in a free state. Its deviation is reflected through rolling force deviation. At this time, it is necessary to immediately and quickly adjust the roll gap deviation to resist the change in rolling force deviation and achieve the purpose of correction. Attached Figure Description
[0015] Figure 1 This invention relates to a method for controlling tail deviation of hot-rolled thin strip steel, and a looper drop-off trend diagram.
[0016] Figure 2This is a schematic diagram of the structure of the control method for tail deviation of hot-rolled thin strip steel according to the present invention, and a leveling effect diagram of the F6 frame. Detailed Implementation
[0017] The invention will now be described in further detail with reference to specific embodiments, but this should not be construed as limiting the scope of the subject matter of the invention to the following embodiments. Example
[0018] Taking the rolling of thin-gauge strip steel in a hot continuous rolling mill (F1-F7) of a steel plant as an example, this paper illustrates the implementation process of this method on the F6 stand.
[0019] Data preparation and triggering: Just before the upstream F4 stand is about to discard the strip (i.e., the tail of the strip is about to leave F4), the control system of the F6 stand records its initial rolling force deviation at this moment. Subsequently, the system received a "steel throwing complete" signal from frame F4 and immediately triggered the tail leveling procedure for frame F6.
[0020] Loop control module operation (taking the loop between F5 and F6 racks as an example): The program presets a base speed compensation value based on the strip thickness (for example, to slightly reduce the speed of the F6 frame) and completes the deceleration in about 0.3 seconds, assisting the looper between F5 and F6 to begin a smooth descent.
[0021] The system monitors the angle of the looper. At the end of the preset "small looper control" phase, the angle θ1 is recorded; at the moment when the F6 frame throws steel, the angle θ2 is recorded.
[0022] Compare θ1 with the set value θref1 (e.g., 16°), and compare θ2 with the set value θref2 (e.g., 14°).
[0023] If θ1 is greater than θref1, it indicates that the looper is falling back too slowly. The control system will then learn and, when rolling the next strip of the same type, appropriately increase the looper control time (e.g., by 0.05s) and slightly increase the speed compensation value to promote an earlier and faster looper fall. Conversely, it will reduce the speed compensation value.
[0024] If θ2 is greater than θref2, it means that the looper is still too high when throwing the steel, so the starting control time for the next piece of steel should be increased. Conversely, it should be decreased.
[0025] The above parameters are adjusted by superimposing a feedforward correction Δu(t) onto the output of the standard looper angle PI controller. The absolute value of Δu(t) does not exceed a limit and increases linearly at a fixed slope of ΔUmax / T correction per second (T correction is within 0.1 to 0.3 seconds) until the target correction value is reached. This "programmable slope limiting" method ensures that the change in control quantity is smooth, avoiding any impact on the rolling speed. See the full process below. Figure 1 The trend shown is a trap that leads to a trap.
[0026] Rolling force adjustment module operation: After the self-leveling program is started, this module begins to calculate the change in rolling force deviation of the F6 stand in real time: .
[0027] The deviation detection threshold is set to 50kN. When |Δ(ΔF)|>50kN, the module immediately takes action.
[0028] For example, if the calculated Δ(ΔF) = +80kN (+50kN), it indicates that the strip is deviating towards the operating side. The system then outputs a roll gap leveling command: press down the operating side roll gap while simultaneously raising the drive side roll gap. The leveling amount ΔS is calculated using the formula ΔS = Δ(ΔF) / Km (Km is the stiffness of the F6 frame, for example, 4000kN / mm, then ΔS is approximately 0.02mm). The adjustment speed is limited to the system's maximum capacity (e.g., 2mm / s), and an adjustment is performed cumulatively once per PLC scan cycle (30ms).
[0029] This adjustment will continue until the strip misalignment is corrected (|Δ(ΔF)| falls below the threshold), or the accumulated leveling reaches the safety limit, or the F6 rack itself throws out strip. Once the F6 rack throws out strip, the module output is reset to zero, preparing for the next cycle. See [link to procedure] for details. Figure 2 The F6 rack leveling effect is shown.
[0030] System application scope: This method can be applied sequentially or selectively to each stand of the finishing mill. Considering that the effects of tail tension decay and deviation are most prominent in the last stand, this tail leveling function is usually activated first on the last three stands, F5, F6, and F7, to achieve the best control effect.
[0031] In summary, this invention effectively solves the problem of tail-end deviation control in hot-rolled thin strip steel by employing a collaborative control strategy that integrates feedforward, feedback, and self-learning mechanisms, demonstrating high engineering application value. Although embodiments of this invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of this invention is defined by the appended claims and their equivalents. In short, if those skilled in the art, inspired by this invention, design similar structures and embodiments without departing from its inventive spirit, such designs should fall within the protection scope of this invention.
Claims
1. A method for controlling tail deviation of hot-rolled thin strip steel, characterized in that, Includes the following steps: S1. Before the steel is thrown from the upstream stand of the hot strip finishing mill, record the initial rolling force deviation of the current stand. ,in =F operating side - F transmission side; S2. After receiving the steel throwing signal from the upstream stand, start the tail leveling program, which includes a looper control module and a rolling force adjustment module; S3. The looper control module performs the following operations: (1) Based on the current thickness of the strip, the basic speed compensation value is preset, and the mill speed is reduced within 0.3 seconds to assist the looper to fall back; (2) Record the actual angle θ1 of the loop at the end of the loop control and compare it with the set reference angle θref1, wherein the value range of θref1 is 14°~18°; (3) Record the actual angle θ2 of the looper when the rolling mill throws the steel, and compare it with the set reference angle θref2. The value range of θref2 is 12°~16°. (4) Based on the comparison results of θ1 and θref1, dynamically adjust the control time of the small sleeve of the next piece of steel and the foundation speed compensation value; (5) Based on the comparison results of θ2 and θref2, dynamically adjust the starting control time for the next piece of steel to be dropped into the sleeve; S4. The rolling force adjustment module performs the following operations: (1) Real-time calculation of rolling force deviation change ; (2) When |Δ(ΔF)| exceeds the set threshold, determine the direction of strip deviation and output the roll gap leveling amount; (3) Stop adjusting when the leveling amount reaches the preset maximum allowable range or when the current frame throws steel, and clear the output to zero after the current frame throws steel.
2. The method for controlling tail deviation of hot-rolled thin strip steel according to claim 1, characterized in that, The adjustment range of the basic speed compensation value is 0-5%, the adjustment range of the small sleeve control time is 0.3-0.8 seconds, and the adjustment range of the sleeve drop start control time is 0.1-0.3 seconds.
3. The method for controlling tail deviation of hot-rolled thin strip steel according to claim 1, characterized in that, The original looper angle and height control output is expressed as: ； Therefore, the correction amount for its programmable slope limiting is: ； Where e(t) is the looper angle deviation (the difference between the actual angle and the set reference angle); K p K i These are the proportional and integral gains of the PI controller, respectively. Δu(t) is the feedforward correction amount, the absolute value of which is no greater than ΔUmax (≤5% of the reference speed compensation value), and is corrected according to a fixed slope |dΔu / dt|≤ΔUmax / T, where T correction ∈ [0.1s, 0.3s]. It is linearly accumulated cycle by cycle (PLC scan cycle 30ms) until the target correction amount is reached, so as to achieve smooth fine adjustment of "small set control time" or "set start time".
4. The method for controlling tail deviation of hot-rolled thin strip steel according to claim 1, characterized in that, In the rolling force adjustment module: the set threshold is 50kN. If Δ(ΔF) < -50kN, the operating side roll gap is raised and the transmission side roll gap is pressed; if Δ(ΔF) > +50kN, the operating side roll gap is pressed and the transmission side roll gap is raised.
5. The method for controlling tail deviation of hot-rolled thin strip steel according to claim 1, characterized in that, The calculation method for the roll gap leveling amount in the rolling force adjustment module is: ΔS=Δ(ΔF) / Km, where Km is the mill stiffness.
6. The method for controlling tail deviation of hot-rolled thin strip steel according to claim 1, characterized in that, The adjustment speed of the roller gap leveling action is limited to the maximum adjustment speed set by the frame, and is performed in an integral manner, accumulating cycle by cycle.
7. The method for controlling tail deviation of hot-rolled thin strip steel according to any one of claims 1 to 6, characterized in that, The method is applicable to stands F1 to F7 of hot strip mill finishing mills, and control is preferentially implemented in the last three stands.
8. The method for controlling tail deviation of hot-rolled thin strip steel according to claim 1, characterized in that, The method achieves forced centering of the strip before steel throwing through the rapid small looper function during the looper control stage, and immediately starts rolling force correction control after steel throwing on the upstream stand.
9. The method for controlling tail deviation of hot-rolled thin strip steel according to claim 1, characterized in that, In step S3: If θ1 > θref1, the control time of the small sleeve is increased by 0.03 to 0.1 s and the base speed compensation value is increased for the next piece of steel; if θ1 < θref, the control time of the small sleeve is decreased by 0.03 to 0.1 s and the base speed compensation value is decreased. If θ2 > θref2, the starting control time for the next piece of steel is increased by 0.03 to 0.1 s; if θ2 < θref2, the starting control time for the next piece of steel is decreased by 0.03 to 0.1 s.
10. The method for controlling tail deviation of hot-rolled thin strip steel according to claim 4, characterized in that, The set threshold can be adjusted online within the range of 0 to 200 kN.