A strip thickness control method based on thickness measurement value delay compensation

Abstract

The application provides a strip thickness control method based on thickness measurement value delay compensation; comprising: step 1, establishing a strip thickness dynamic system; step 2, establishing a strip thickness measurement value considering the installation position offset of a thickness gauge; step 3, establishing a strip thickness inertia link prediction value; step 4, designing a mill roll gap setting value feed-forward quantity offsetting the effect of rolling pressure; step 5, designing a mill roll gap setting value feedback quantity of strip thickness deviation prediction value proportional feedback; step 6, designing a final mill roll gap setting value; and step 7, inputting the mill roll gap setting value into a mill hydraulic roll gap adjusting system for mill roll gap adjustment. The strip thickness inertia link prediction designed in the application not only makes up for the influence of strip thickness measurement value delay on thickness control, but also improves the thickness control response effect in the strip rolling transition process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plate and strip rolling in the metallurgical industry, and particularly relates to a plate and strip thickness control method based on thickness measurement value delay compensation. BACKGROUND

[0002] Modern industry development puts forward higher requirements for plate and strip production, and the plate and strip thickness is one of important indexes for measuring the plate and strip quality. The thickness control is an important process in the cold rolling process and is a core link in the rolling process. The plate and strip thickness control refers to a process of rolling the strip with different incoming thicknesses into the strip with a specified thickness. The basic principle of the plate and strip thickness control is to adjust the set value of the rolling mill roll gap according to the plate and strip thickness measurement value, and then change the roll gap through the hydraulic roll gap adjusting system, so as to realize the real-time regulation and control of the plate and strip thickness at the rolling mill outlet.

[0003] In the actual production process, the rolling process is complex and dangerous, in order to prolong the service life of the plate and strip thickness gauge, the installation position of the plate and strip thickness gauge is kept a safe distance from the rolling mill outlet. Due to the offset of the installation position of the plate and strip thickness gauge, the plate and strip thickness value obtained by measurement has a certain delay. If the delayed plate and strip thickness measurement value is directly used without processing, the plate and strip control effect will be delayed, the plate and strip thickness control quality will be reduced, and the plate and strip quality will be affected. For the plate and strip thickness measurement value delay phenomenon caused by the offset of the installation position of the plate and strip thickness gauge, if the predicted value of the plate and strip thickness measurement value is designed and the adjusting method of the rolling mill roll gap set value is designed, the transient control performance and closed-loop control effect of the plate and strip thickness can be improved, so as to improve the control precision of the plate and strip thickness and improve the plate and strip rolling quality. SUMMARY

[0004] The application aims to provide a plate and strip thickness control method based on thickness measurement value delay compensation.

[0005] The application is implemented by the following technical scheme:

[0006] The application relates to a plate and strip thickness control method based on thickness measurement value delay compensation, comprising the following steps:

[0007] Step 1, establishing a plate and strip thickness dynamic system;

[0008] Step 2, establishing a plate and strip thickness measurement value considering the offset of the installation position of the thickness gauge;

[0009] Step 3, establishing an inertial link predicted value of the plate and strip thickness;

[0010] Step 4, designing a rolling mill roll gap set value feedforward quantity for offsetting the action of the rolling pressure;

[0011] Step 5, design the feedback amount of rolling mill roll gap setting value proportional feedback of strip thickness deviation prediction value;

[0012] Step 6, design the final rolling mill roll gap setting value;

[0013] Step 7, input the rolling mill roll gap setting value into the rolling mill hydraulic roll gap adjustment system for rolling mill roll gap adjustment, and finally form a complete closed-loop strip thickness control method.

[0014] Preferably, in step 1, the specific step of establishing the strip thickness dynamic system is: according to the rolling mill bounce equation and the rolling mill roll gap adjustment system, the strip thickness dynamic system is established, as shown in formula (1):

[0015]

[0016] In formula (1), is the derivative operation, t∈R is the running time of the rolling mill system, H(t)∈R is the strip thickness at time t, S(t)∈R is the rolling mill roll gap setting value at time t, A∈R is the strip thickness dynamic coefficient, P∈R is the rolling pressure, and M∈R is the rolling mill stiffness coefficient.

[0017] Preferably, in step 2, the specific step of establishing the strip thickness measurement value considering the installation position offset of the thickness gauge is:

[0018] Based on the influence of the installation position offset of the thickness gauge on the control accuracy of the strip thickness, the strip thickness measurement value considering the installation position offset of the thickness gauge is established, as shown in formula (2):

[0019]

[0020] In formula (2), H m (t)∈R is the strip thickness measurement value at time t, v∈R is the rolling speed of the strip, and l∈R is the installation position offset distance of the strip thickness gauge, that is, the distance from the installation position of the strip thickness gauge to the outlet of the rolling mill.

[0021] Preferably, in step 3, the formula for establishing the inertia link prediction value of the strip thickness is as shown in formula (3):

[0022]

[0023] In formula (3), H p (t)∈R is the inertia link prediction value of the strip thickness at time t, H m (t)∈R is the strip thickness measurement value at time t, v∈R is the rolling speed of the strip, and l∈R is the installation position offset distance of the strip thickness gauge, that is, the distance from the installation position of the strip thickness gauge to the outlet of the rolling mill.

[0024] Preferably, in step 4, the specific steps of designing the feedforward amount of the rolling mill roll gap setting value to offset the rolling pressure effect are:

[0025] According to the dynamic system of plate and strip thickness, the feedforward value of the mill roll gap setting value is designed to offset the rolling pressure effect, as shown in formula (4):

[0026]

[0027] In formula (4), S ff (t)∈R is the feedforward value of the mill roll gap setting value at time t, P∈R is the rolling pressure, and M∈R is the mill stiffness coefficient.

[0028] Preferably, in step 5, the specific steps of designing the rolling mill roll gap set value feedback amount for the proportional feedback of the strip thickness deviation prediction value are as follows:

[0029] (I) First, based on the predicted value of the inertia link of the strip thickness, the predicted value of the strip thickness deviation is established, as shown in formula (5):

[0030] H ep (t) = H p (t)-H r (5)

[0031] In formula (5), H r ∈R is the target value of strip rolling thickness, H ep (t)∈R is the predicted value of the strip thickness control deviation at time t, H p (t)∈R is the inertia link prediction value of the strip thickness at time t;

[0032] (2) According to the predicted value of the strip thickness deviation, the feedback amount of the mill roll gap setting value of the strip thickness deviation predicted value proportional feedback is designed, as shown in formula (6):

[0033] S fb (t) = -k p H ep (t)+H p (t) (6)

[0034] In formula (6), S fb (t)∈R is the rolling mill roll gap setting value feedback of the strip thickness deviation prediction value at time t, k p ∈R is the proportional feedback gain coefficient, H ep (t)∈R is the predicted value of the strip thickness control deviation at time t, H p (t)∈R is the inertia link prediction value of the strip thickness at time t.

[0035] Preferably, in step 6, the specific step of designing the final rolling mill roll gap setting value is: adding the rolling mill roll gap setting value feedforward amount in step 4 and the rolling mill roll gap setting value feedback amount in step 5 to obtain the final rolling mill roll gap setting value, as shown in formula (7):

[0036] S(t)=S ff (t)+S fb (t) (7)

[0037] In formula (7), S fb (t)∈R is the rolling mill roll gap setting value feedback of the strip thickness deviation prediction value at time t, S ff (t)∈R is the feedforward value of the rolling mill roll gap setting value at time t.

[0038] In the above formula of the present invention, the symbols are explained as follows:

[0039] R: the set of all real numbers;

[0040] t: running time of the rolling mill system, t∈[0,∞);

[0041] H(t): Strip thickness at time t, H(t)∈R;

[0042] S(t): mill roll gap setting value at time t, S(t)∈R;

[0043] A: dynamic coefficient of strip thickness, A∈R;

[0044] P: rolling pressure, P∈R;

[0045] M: rolling mill stiffness coefficient, M∈R;

[0046] H m (t): measured thickness of the plate at time t, H m (t)∈R;

[0047] v: strip rolling speed, v∈R;

[0048] l: installation offset distance of the strip thickness gauge, l∈R;

[0049] H p (t): The predicted value of the inertia link of the plate thickness at time t, H p (t)∈R;

[0050] S ff (t): The feedforward value of the mill roll gap setting value at time t, S ff (t)∈R;

[0051] H r : Target value of strip rolling thickness, H r ∈R;

[0052] H ep (t) is a plate strip thickness control deviation prediction value at time t, H ep (t) is a plate strip thickness control deviation prediction value at time t, H

[0053] S fb (t) is a plate strip thickness control deviation prediction value at time t, H

[0054] S fb (t) is a plate strip thickness control deviation prediction value at time t, H

[0055] k p : proportional feedback gain coefficient, k p ∈R.

[0056] The present application aims at the plate strip thickness measurement value delay phenomenon caused by the installation position offset of a plate strip thickness gauge, and a plate strip thickness control method using an inertial link prediction is invented. In the present application, the establishment of the inertial link prediction of the plate strip thickness, the design of the rolling mill roll gap setting value feedforward amount, the design of the rolling mill roll gap setting value feedback amount of the plate strip thickness deviation prediction value proportional feedback, and then the use of the rolling mill roll gap setting value feedforward amount and feedback amount to obtain the rolling mill roll gap setting value, and finally the input of the rolling mill roll gap setting value into the rolling mill hydraulic roll gap adjusting system for rolling mill roll gap adjustment, form a complete closed-loop plate strip thickness control method, so as to improve the thickness control effect under the condition of plate strip thickness measurement value delay.

[0057] The present application has the following advantages:

[0058] (1) The present application aims at the plate strip thickness measurement value delay phenomenon caused by the installation position offset of a plate strip thickness gauge, and uses an inertial link to obtain a prediction value of the plate strip thickness, thereby reducing the influence of measurement value delay on the plate strip thickness control precision.

[0059] (2) In the design process of the rolling mill roll gap setting value, the present application designs not only the rolling mill roll gap setting value feedforward amount for offsetting the rolling pressure, but also the rolling mill roll gap setting value feedback amount of the plate strip thickness deviation prediction value proportional feedback, thereby improving the transient response performance of the plate strip thickness control. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is a flow chart of the method of the present application;

[0061] Figure 2 is a control structure diagram of the method of the present application;

[0062] Figure 3 is a comparison diagram of the plate strip thickness control results of the method of the present application and the method without using the inertial link prediction;

[0063] Figure 4This is a comparison chart of thickness control errors in the plate and strip rolling transition process using the method of the present invention and the method without using the inertia link prediction method. DETAILED DESCRIPTION

[0064] The present invention will be described in detail below with reference to specific embodiments. It should be noted that the following embodiments are only for further explanation of the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0065] Example

[0066] This embodiment relates to a strip thickness control method based on thickness measurement value delay compensation, see Figure 1 and Figure 2 As shown, the following steps are included:

[0067] Parameters: A = 1.1, M = 4900000N / mm 3 , l=0.5m,v=4m / S,H r =4.3mm, P=5484000(1+0.1sin(0.5t))N / mm 2 .

[0068] Step 1: Establish a dynamic system for strip thickness. Substitute the above-mentioned relevant parameters into formula (1), and transform it into formula (8):

[0069]

[0070] Step 2: Establish the plate and strip thickness measurement value considering the offset of the thickness gauge installation position: Substitute the above relevant parameters into formula (2), and it is transformed into formula (9):

[0071]

[0072] Step 3: Establish the predicted value of the inertia link of the strip thickness: Substitute the above-mentioned relevant parameters into formula (3), and it is transformed into formula (10):

[0073]

[0074] Step 4: Design the feedforward value of the mill roll gap setting value to offset the rolling pressure effect: After substituting the above-mentioned relevant parameters into formula (4), it is transformed into formula (11):

[0075]

[0076] Step 5: Design the feedback amount of the mill roll gap setting value for the proportional feedback of the strip thickness deviation prediction value:

[0077] First, based on the predicted value of the inertia link of the strip thickness, the predicted value of the strip thickness deviation is established. After substituting the parameters into formula (5), it is transformed into formula (12):

[0078] H ep (t) = H p (t)-4.3 (12)

[0079] Among them H r ∈R is 4.3, H ep (t)∈R is the predicted value of the strip thickness control deviation at time t.

[0080] Then, according to the strip thickness deviation prediction value (12), the rolling mill roll gap set value feedback amount of the strip thickness deviation prediction value proportional feedback is designed, see formula (13):

[0081] S fb (t) = -k p H ep (t)+H p (t) (13)

[0082] The design k p =6.

[0083] Step 6, designing the final mill roll gap setting value;

[0084] The feedforward value of the mill roll gap setting value in step 4 is added to the feedback value of the mill roll gap setting value in step 5 to obtain the final mill roll gap setting value. After substituting the parameters into formula (7), it is transformed into formula (14):

[0085] S(t)=S ff (t)+S fb (t) (14)

[0086] In step 7, the rolling mill roll gap setting value (14) obtained in step 6 is input into the rolling mill hydraulic roll gap adjustment system to adjust the rolling mill roll gap, thereby finally forming a complete closed-loop strip thickness control method.

[0087] To further validate the applicability of the proposed method, simulation software was used to compare the strip thickness control performance of the proposed method with that of a prediction method that does not utilize an inertia link. This method, which does not utilize an inertia link to obtain prediction values, directly uses the measured strip thickness. This approach, in turn, fails to consider the impact of thickness measurement delays caused by thickness gauge installation position offsets on strip thickness control accuracy.

[0088] Depend on Figure 3 The strip thickness control results in the experiment show that when the inertia link prediction method is not used, the strip thickness will overshoot in the transition process of 0 to 2s. The method of the present invention can solve the overshoot problem of the strip thickness in the initial section. Figure 4The comparison chart of thickness control errors during the strip rolling transition process shows that, without the inertia link prediction method, the strip thickness control steady-state error overshoots by 30 μm at 0.5 s, then falls back to within 10 μm, resulting in overshoot oscillation during the transition process. However, using the method of the present invention, the strip thickness transition is smooth, with no overshoot. Therefore, the strip thickness inertia link prediction designed in the present invention compensates for the impact of strip thickness measurement delay on thickness control, improving the thickness control response during the strip rolling transition process.

[0089] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A strip thickness control method based on thickness measurement value delay compensation, characterized in that: The following steps are involved: Step 1: Establish a dynamic system for strip thickness; Step 2: Establishing the plate and strip thickness measurement value taking into account the offset of the thickness gauge installation position; Step 3, establishing the inertia link prediction value of the strip thickness; Step 4, designing a feedforward value of the mill roll gap setting value to offset the rolling pressure effect; Step 5, designing a rolling mill roll gap set value feedback amount for proportional feedback of the strip thickness deviation prediction value; Step 6, designing the final mill roll gap setting value; Step 7: Input the mill roll gap set value into the mill hydraulic roll gap adjustment system to adjust the mill roll gap, and finally form a complete closed-loop strip thickness control method; In step 1, the specific steps of establishing the strip thickness dynamic system are: according to the rolling mill bounce equation and the rolling mill roll gap adjustment system, the strip thickness dynamic system is established, as shown in formula (1): In formula (1), For the derivation operation, t∈R is the running time of the rolling mill system, s; H(t)∈R is the strip thickness at time t, S(t)∈R is the roll gap setting value of the rolling mill at time t, A∈R is the dynamic coefficient of strip thickness, P∈R is the rolling pressure, N / mm 2 ; M∈R is the rolling mill stiffness coefficient, N / mm 3 ; In step 2, the specific steps of establishing the plate and strip thickness measurement value taking into account the thickness gauge installation position offset are: Based on the influence of the thickness gauge installation position offset on the plate and strip thickness control accuracy, the plate and strip thickness measurement value considering the thickness gauge installation position offset is established, as shown in formula (2): In formula (2), H m (t)∈R is the plate thickness measurement value at time t, v∈R is the plate and strip rolling speed, m / s, l∈R is the installation offset distance of the plate and strip thickness gauge, m; In step 3, the formula for establishing the inertia link prediction value of the strip thickness is shown in (3): In formula (3), H p (t)∈R is the inertia link prediction value of the strip thickness at time t, H m (t)∈R is the plate thickness measurement value at time t, v∈R is the plate and strip rolling speed, and l∈R is the offset distance of the plate and strip thickness gauge installation position, that is, the distance from the plate and strip thickness gauge installation position to the rolling mill exit; In step 4, the specific steps of designing the feedforward amount of the mill roll gap setting value to offset the rolling pressure effect are: According to the dynamic system of plate and strip thickness, the feedforward value of the mill roll gap setting value is designed to offset the rolling pressure effect, as shown in formula (4): In formula (4), S ff (t)∈R is the feedforward value of the mill roll gap setting value at time t, P∈R is the rolling pressure, and M∈R is the mill stiffness coefficient; In step 5, the specific steps of designing the rolling mill roll gap set value feedback amount of the strip thickness deviation prediction value proportional feedback are: (I) First, based on the predicted value of the inertia link of the strip thickness, the predicted value of the strip thickness deviation is established, as shown in formula (5): H ep (t)=H p (t)-H r (5) In formula (5), H r ∈R is the target value of strip rolling thickness, H ep (t)∈R is the predicted value of the strip thickness control deviation at time t, H p (t)∈R is the inertia link prediction value of the strip thickness at time t; (2) According to the predicted value of the strip thickness deviation, the feedback amount of the mill roll gap setting value of the strip thickness deviation predicted value proportional feedback is designed, as shown in formula (6): S fb (t)=-k p H ep (t)+H p (t) (6) In formula (6), S fb (t)∈R is the feedback value of the mill roll gap setting value of the strip thickness deviation prediction value at time t, k p ∈R is the proportional feedback gain coefficient, H ep (t)∈R is the predicted value of the strip thickness control deviation at time t, H p (t)∈R is the inertia link prediction value of the strip thickness at time t; In step 6, the specific steps of designing the final rolling mill roll gap setting value are: adding the rolling mill roll gap setting value feedforward amount in step 4 and the rolling mill roll gap setting value feedback amount in step 5 to obtain the final rolling mill roll gap setting value, as shown in formula (7): S(t)=S ff (t)+S fb (t) (7) In formula (7), S fb (t)∈R is the rolling mill roll gap setting value feedback of the strip thickness deviation prediction value at time t, S ff (t)∈R is the feedforward value of the rolling mill roll gap setting value at time t.

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