Plate and strip thickness control method based on thickness measurement value delay compensation

Abstract

The invention provides a strip thickness control method based on thickness measurement value delay compensation. Comprising the steps of 1, establishing a plate and strip thickness dynamic system; step 2, establishing a plate and strip thickness measurement value considering the installation position offset of the thickness gauge; step 3, establishing an inertial link forecast value of the thickness of the plate strip; 4, designing the feed-forward quantity of the set value of the roll gap of the rolling mill for counteracting the action of rolling pressure; 5, designing a mill roll gap set value feedback quantity fed back by the plate strip thickness deviation forecast value proportion; step 6, designing a final roll gap set value of the rolling mill; and 7, inputting the rolling mill roll gap set value into a rolling mill hydraulic roll gap adjusting system to adjust the rolling mill roll gap. The plate and strip thickness inertia link prediction designed by the invention not only makes up the influence of plate and strip thickness measurement value delay on thickness control, but also improves the thickness control response effect in the plate and strip rolling transition process.

Description

Technical Field

[0001] The invention belongs to the technical field of plate and strip rolling in the metallurgical industry; in particular, it relates to a plate and strip thickness control method based on thickness measurement value delay compensation. Background Art

[0002] The rapid development of modern industry has put forward higher requirements for plate and strip production, and the thickness of plate and strip has always been one of the important indicators for measuring the quality of plate and strip. Thickness control is an important process in the cold rolling process and the core link of the rolling process. Plate and strip thickness control refers to the process of rolling strips of different incoming thicknesses into strips of specified thickness. The basic principle of plate and strip thickness control is to adjust the set value of the mill roll gap according to the measured value of the plate and strip thickness, and then change the roll gap through the hydraulic roll gap adjustment system, so as to realize real-time control of the plate and strip thickness at the mill outlet.

[0003] In the actual production process, the rolling process is complex and prone to danger. In order to extend the service life of the plate and strip thickness gauge, the installation position of the plate and strip thickness gauge will maintain a certain safety distance from the mill exit. Due to the offset of the installation position of the plate and strip thickness gauge, there is a certain delay in the measured plate and strip thickness value. If the delayed plate and strip thickness measurement value is directly used without processing, it will delay the plate and strip control effect, reduce the quality of plate and strip thickness control, and affect the quality of the plate and strip. For the delay in the plate and strip thickness measurement value 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 can be designed in a targeted manner, and the corresponding adjustment method of the rolling mill roll gap setting value can be designed, it will be able to improve the transient control performance and closed-loop control effect of the plate and strip thickness, thereby improving the control accuracy of the plate and strip thickness and improving the rolling quality of the plate and strip. Summary of the invention

[0004] The object of the present invention is to provide a strip thickness control method based on thickness measurement value delay compensation.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention 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 dynamic system of plate and strip thickness;

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

[0009] Step 3, establishing the inertia link prediction value of the plate thickness;

[0010] Step 4, designing a feedforward amount of a rolling mill roll gap setting value to offset the rolling pressure effect;

[0011] Step 5, designing a rolling mill roll gap set value feedback amount for proportional feedback of the strip thickness deviation prediction value;

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

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

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

[0015]

[0016] In formula (1), For the derivation operation, t∈R is the operating time of the rolling mill system, H(t)∈R is the strip thickness at time t, S(t)∈R is the 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 mill stiffness coefficient.

[0017] Preferably, 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:

[0018] 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):

[0019]

[0020] 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, 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.

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

[0022]

[0023] In formula (3), H p (t)∈R is the inertia link prediction value of the plate 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.

[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 feedback amount of the rolling mill roll gap setting value for proportional feedback of the strip thickness deviation prediction value are:

[0029] (I) First, according to the predicted value of the inertia link of the plate thickness, the predicted value of the plate 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 the strip rolling thickness, H ep (t)∈R is the predicted value of the plate thickness control deviation at time t, H p (t)∈R is the inertia link prediction value of the plate thickness at time t;

[0032] (ii) 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 feedback value of the mill roll gap setting value of the proportional 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 plate thickness control deviation at time t, H p (t)∈R is the inertia link predicted value of the plate 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 feedback value of the mill roll gap setting value of the proportional 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 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 plate 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 plate and 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): predicted value of plate thickness control deviation at time t, H ep (t)∈R;

[0053] S fb (t): The rolling mill roll gap setting value feedback of the plate and strip thickness deviation prediction value at time t;

[0054] S fb (t)∈R;

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

[0056] The present invention aims at the phenomenon of delayed strip thickness measurement value caused by the offset of the installation position of the strip thickness gauge, and invents a strip thickness control method using inertia link prediction. The present invention includes establishing the inertia link prediction of the strip thickness, designing the mill roll gap setting value feedforward, designing the mill roll gap setting value feedback of the strip thickness deviation prediction value proportional feedback, and then using the mill roll gap setting value feedforward and feedback to obtain the mill roll gap setting value, and finally inputting the mill roll gap setting value into the mill hydraulic roll gap adjustment system to adjust the mill roll gap, forming a complete set of closed-loop strip thickness control methods, thereby improving the thickness control effect in the case of delayed strip thickness measurement value.

[0057] The present invention has the following advantages:

[0058] (1) In order to solve the problem of strip thickness measurement value delay caused by the installation position offset of the strip thickness gauge, the present invention adopts an inertia link to obtain the predicted value of the strip thickness, thereby reducing the influence of the measurement value delay on the strip thickness control accuracy.

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

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

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

[0062] Figure 3 This is a comparison chart of the plate and strip thickness control results using the method of the present invention and the prediction method without using the inertia link;

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

[0064] The present invention is described in detail below in conjunction with specific embodiments. It should be noted that the following embodiments are only further descriptions 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 of plate thickness. Substitute the above related 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 related parameters into formula (2), and it is transformed into formula (9):

[0071]

[0072] Step 3, establish the inertia link prediction value of the plate thickness: after substituting the above related parameters into formula (3), 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 related 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, according to 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 predicted value of the strip thickness deviation (12), the feedback amount of the mill roll gap setting value for the proportional feedback of the predicted value of the strip thickness deviation is designed, as shown in 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 rolling mill roll gap setting value in step 4 is added to the feedback value of the rolling mill roll gap setting value in step 5 to obtain the final rolling 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] Step 7, inputting the rolling mill roll gap setting value (14) obtained in step 6 into the rolling mill hydraulic roll gap adjustment system to adjust the rolling mill roll gap, and finally forming a complete closed-loop strip thickness control method.

[0087] In order to further verify the applicability of the method of the present invention, simulation software was used to compare the plate and strip thickness control effects of the method of the present invention and the prediction method without using the inertia link. The prediction method without using the inertia link refers to a design method that does not use the inertia link to obtain the prediction value, but directly uses the plate and strip thickness measurement value, that is, it does not consider the influence of the thickness measurement value delay caused by the offset of the thickness gauge installation position on the plate and strip thickness control accuracy.

[0088] Depend on Figure 3 The plate and strip thickness control results in the embodiment show that when the inertia link prediction method is not used, the plate and strip thickness will overshoot in the transition process of 0 to 2s; the overshoot problem of the plate and strip thickness in the initial stage can be solved by adopting the method of the present invention. Figure 4The thickness control error comparison chart of the plate and strip rolling transition process shows that when the inertia link prediction method is not used, the overshoot reaches 30μm when the steady-state error of the plate and strip thickness control is 0.5s, and then it is adjusted back to the range of 10μm, and the transition process produces overshoot oscillation phenomenon; using the method of the present invention, the plate and strip thickness transition is smooth and no overshoot phenomenon occurs. Therefore, the plate and strip thickness inertia link prediction designed by the present invention makes up for the influence of the delay of the plate and strip thickness measurement value on the thickness control, and can improve the thickness control response effect during the plate and 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 modifications or variations within the scope of the claims, which will 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, establishing a dynamic system of plate and strip thickness; Step 2, establishing a 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 plate thickness; Step 4, designing a feedforward amount of a rolling 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, inputting the rolling mill roll gap setting value into the rolling mill hydraulic roll gap adjustment system to adjust the rolling mill roll gap, and finally forming a complete closed-loop strip thickness control method.

2. The strip thickness control method based on thickness measurement value delay compensation according to claim 1, characterized in that: 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 operating time of the rolling mill system, H(t)∈R is the strip thickness at time t, S(t)∈R is the 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 mill stiffness coefficient.

3. The strip thickness control method based on thickness measurement value delay compensation according to claim 1, characterized in that: 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 measured value of the plate thickness at time t, v∈R is the rolling speed of the plate and strip, and l∈R is the installation offset distance of the plate and strip thickness gauge.

4. The strip thickness control method based on thickness measurement value delay compensation according to claim 1, characterized in that: 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 plate 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.

5. The strip thickness control method based on thickness measurement value delay compensation according to claim 1, characterized in that: 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: according to the dynamic system of the plate and strip thickness, designing the feedforward amount of the rolling mill roll gap setting value 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.

6. A strip thickness control method based on thickness measurement value delay compensation as claimed in claim 1, characterized in that: In step 5, the specific steps of designing the feedback amount of the rolling mill roll gap setting value for proportional feedback of the strip thickness deviation prediction value are as follows: (I) First, according to the predicted value of the inertia link of the plate thickness, the predicted value of the plate 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 the strip rolling thickness, H ep (t)∈R is the predicted value of the plate thickness control deviation at time t, H p (t)∈R is the inertia link prediction value of the plate thickness at time t; (ii) 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 proportional 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 plate thickness control deviation at time t, H p (t)∈R is the inertia link predicted value of the plate thickness at time t.

7. The strip thickness control method based on thickness measurement value delay compensation according to claim 1, characterized in that: 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 feedback value of the mill roll gap setting value of the proportional 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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