Robust self-adaptive plate strip thickness control method

Abstract

The invention provides a robust self-adaptive plate and strip thickness control method. Comprising the following steps: step 1, establishing a plate and strip thickness dynamic system considering unknown disturbance interference; step 2, establishing a plate strip thickness control deviation value; 3, designing an estimated value of the deviation value of the dynamic coefficient of the thickness of the strip; 4, designing a rolling mill roll gap set value for compensating the plate strip thickness dynamic coefficient deviation value; 5, designing a rolling mill roll gap set value fed back by the plate and strip thickness control deviation value proportion; and step 6, designing a final roll gap set value of the rolling mill. According to the method, the plate and strip thickness dynamic coefficient deviation value is actively estimated, so that the rolling mill roll gap set value for compensating the plate and strip thickness dynamic coefficient deviation value is established, meanwhile, the rolling mill roll gap set value fed back by the plate and strip thickness control deviation value proportion is added, and finally the two values are added to obtain the final rolling mill roll gap set value. And the anti-interference capability and the operation stability of the plate and strip thickness control system are improved, so that the plate and strip thickness control precision is improved.

Description

Technical Field

[0001] The invention relates to the technical field of plate and strip rolling in the metallurgical industry, and in particular to a robust and adaptive plate and strip thickness control method. 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 to measure 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 material thicknesses into strips of specified thickness. The basic principle of plate and strip thickness control is to change the set value of the roll gap, and then change the roll gap through the hydraulic roll gap adjustment system, so as to control the thickness of the plate and strip at the exit of the rolling mill.

[0003] At present, the commonly used strip thickness control methods include BISRA-AGC method, thickness gauge AGC method with coefficient compensation, dynamic setting AGC method, etc. In all the current methods, the dynamic coefficient of strip thickness needs to be known, and the influence of the fluctuation of the dynamic coefficient of strip thickness on the strip thickness is not considered. During the strip rolling process, it will be affected by various unknown disturbances, such as random fluctuations in the strip thickness at the entrance of the rolling mill, changes in external temperature, lubrication conditions, surface wear of the rollers, etc. Various random disturbances will cause unknown deviations in the dynamic coefficient of strip thickness. In the strip thickness control, if the influence of the deviation of the dynamic coefficient of strip thickness is not considered, the control accuracy of the strip thickness will be reduced, which will affect the quality of the finished product. For the deviation of the dynamic coefficient of strip thickness caused by various unknown disturbances, if a robust and adaptive strip thickness control method can be designed specifically, the control accuracy of the strip thickness will be improved and the strip rolling quality will be improved. Summary of the invention

[0004] The purpose of the present invention is to provide a robust and adaptive strip thickness control method. The method of the present invention establishes an estimated value of the strip thickness dynamic coefficient deviation, designs a rolling mill roll gap setting value that compensates for the strip thickness dynamic model, and designs a rolling mill roll gap setting value for proportional feedback of the strip thickness control deviation, thereby improving the control accuracy of the strip thickness.

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

[0006] The present invention relates to a robust and adaptive strip thickness control method, comprising the following steps:

[0007] Step 1, establish a dynamic system of plate thickness considering unknown disturbance interference;

[0008] Step 2, establishing the strip thickness control deviation;

[0009] Step 3, design an estimated value of the dynamic coefficient deviation of the plate thickness;

[0010] Step 4, designing a setting value of the mill roll gap that compensates for the deviation of the dynamic coefficient of the plate and strip thickness;

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

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

[0013] Preferably, in step 1, the specific steps of establishing a plate and strip thickness dynamic system considering unknown disturbance interference are: according to the rolling mill bounce equation and the rolling mill roll gap adjustment system, a plate and strip thickness dynamic system considering unknown disturbance interference is established, see formula (1):

[0014]

[0015] In formula (1), For the derivation operation, 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, M∈R is the mill stiffness coefficient, and a Δ ∈R is the deviation of the dynamic coefficient of strip thickness caused by disturbance.

[0016] Preferably, in step 2, the formula for establishing the strip thickness control deviation is shown in formula (2):

[0017] H e (t) = H(t) - H r (2)

[0018] In formula (2), H(t)∈R is the thickness of the plate at time t, H r ∈R is the target value of the strip rolling thickness, H e (t)∈R is the thickness control deviation of the plate at time t.

[0019] Preferably, in step 3, the specific process of estimating the deviation of the dynamic coefficient of the designed plate thickness is shown in formula (3):

[0020]

[0021] In formula (3), k a ∈R is the dynamic estimation coefficient of the dynamic coefficient deviation of the plate thickness, H(t)∈R is the plate thickness at time t, H e (t)∈R is the plate thickness control deviation at time t, It is the estimated value of the dynamic coefficient deviation of the plate thickness at time t.

[0022] Preferably, in step 4, the specific process of designing the rolling mill roll gap setting value for compensating the strip thickness dynamic coefficient deviation is: according to the strip thickness dynamic system considering unknown disturbance interference and the estimated value of the strip thickness dynamic coefficient deviation, the rolling mill roll gap setting value for compensating the strip thickness dynamic coefficient deviation is designed, as shown in formula (4):

[0023]

[0024] In formula (4), H(t)∈R is the thickness of the plate at time t, S m (t)∈R is the mill roll gap setting value for compensating the dynamic coefficient deviation of the strip thickness at time t, P∈R is the rolling pressure, M∈R is the mill stiffness coefficient, a∈R is the dynamic coefficient of the strip thickness, It is the estimated value of the dynamic coefficient deviation of the plate thickness at time t.

[0025] Preferably, in step 5, the rolling mill roll gap setting value for the designed strip thickness control deviation proportional feedback is as shown in formula (5):

[0026]

[0027] In formula (5), S p (t)∈R is the rolling mill roll gap setting value of the proportional feedback of the strip thickness control deviation at time t, H e (t)∈R is the plate thickness control deviation at time t, a∈R is the plate thickness dynamic coefficient, k p ∈R is the proportional feedback gain coefficient.

[0028] 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 that compensates for the strip thickness dynamic coefficient deviation and the rolling mill roll gap setting value that is proportionally fed back to the strip thickness control deviation to obtain the final rolling mill roll gap setting value, see formula (6):

[0029] S(t)=S m (t)+S p (t) (6)

[0030] In formula (6), S m (t) is the mill roll gap setting value for compensating the dynamic coefficient deviation of the strip thickness, S p (t) is the rolling mill roll gap setting value for proportional feedback of the strip thickness control deviation.

[0031] In the above formulas involved in the present invention, the symbols are explained as follows:

[0032] R: the set of all real numbers;

[0033] t: running time of rolling mill system, t∈[0,∞);

[0034] H(t): Strip thickness at time t, H(t)∈R;

[0035] S(t): mill roll gap setting value at time t, S(t)∈R;

[0036] a: dynamic coefficient of plate thickness, a∈R;

[0037] P: rolling pressure, P∈R;

[0038] M: rolling mill stiffness coefficient, M∈R;

[0039] a Δ : Deviation of dynamic coefficient of plate thickness caused by disturbance, a Δ ∈R;

[0040] H r : Target value of strip rolling thickness, H r ∈R;

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

[0042] k a : Dynamic estimation coefficient of the dynamic coefficient deviation of the plate thickness, k a ∈R;

[0043] The estimated value of the dynamic coefficient deviation of the plate thickness at time t,

[0044] S m (t): The mill roll gap setting value for compensating the dynamic coefficient deviation of the strip thickness at time t, S m (t)∈R;

[0045] S p (t): The rolling mill roll gap setting value of the strip thickness control deviation proportional feedback at time t, S p (t)∈R;

[0046] k p : Proportional feedback gain coefficient, k p ∈R.

[0047] The present invention aims at the phenomenon of dynamic coefficient deviation of strip thickness caused by various unknown disturbances. By actively estimating the deviation of the dynamic coefficient of strip thickness, a rolling mill roll gap setting value for compensating the deviation of the dynamic coefficient of strip thickness is established. At the same time, a rolling mill roll gap setting value for proportional feedback of the strip thickness control deviation is added. Finally, the two are added together to obtain the final rolling mill roll gap setting value, which improves the anti-interference ability and operation stability of the strip thickness control system, thereby improving the strip thickness control accuracy.

[0048] The present invention has the following advantages:

[0049] (1) The present invention aims to solve the technical problem that the existing strip thickness control method does not specifically deal with the deviation of the dynamic coefficient of strip thickness. The present invention takes into account the influence of the deviation of the dynamic coefficient of strip thickness, designs a system for generating an estimated value of the deviation of the dynamic coefficient of strip thickness, and designs a setting value of the rolling mill roll gap that compensates for the deviation of the dynamic coefficient of strip thickness, thereby compensating for the influence of the deviation of the dynamic coefficient of strip thickness.

[0050] (2) In addition to compensating for the rolling mill roll gap setting value of the strip thickness dynamic coefficient deviation, the present invention also adds a rolling mill roll gap setting value for proportional feedback of the strip thickness control deviation, thereby enhancing the overall stability of the strip thickness control closed-loop system. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is a flow chart of the method of the present invention;

[0052] Figure 2 It is a control structure diagram of the method of the present invention;

[0053] Figure 3 A comparison diagram of the results of the strip thickness control using the method of the present invention and the method not using the estimation and compensation method for the strip thickness dynamic coefficient deviation;

[0054] Figure 4 It is a comparison diagram of the steady-state error of the strip thickness control using the method of the present invention and the method not using the estimation and compensation method of the dynamic coefficient deviation of the strip thickness. DETAILED DESCRIPTION

[0055] 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.

[0056] Example

[0057] This embodiment relates to a robust and adaptive strip thickness control method. Figure 1 and Figure 2 As shown;

[0058] The parameters involved in this embodiment are: a = 1.101, M = 5100000 N / mm 3 , H r =4.5mm, P=5787000(1+0.1sin(t))N / mm 2 ;

[0059] The specific steps are as follows:

[0060] Step 1: Establish a dynamic system of plate thickness considering unknown disturbances. Substitute the above parameters into formula (1), and we get formula (7):

[0061]

[0062] Step 2: Establish the strip thickness control deviation. Substitute the above parameters into formula (2) to obtain formula (8):

[0063] H e (t) = H(t) - H r (8)

[0064] Step 3, design the estimated value of the dynamic coefficient deviation of the plate thickness. Substituting the above parameters into formula (3), we get formula (9):

[0065]

[0066] In formula (9), design k a =3.

[0067] Step 4, design the mill roll gap setting value that compensates for the dynamic coefficient deviation of the strip thickness. Substituting the above parameters into formula (4), we get formula (10):

[0068]

[0069] Step 5, design the mill roll gap setting value for the proportional feedback of the strip thickness control deviation amount. Substituting the above parameters into formula (5), we get formula (11):

[0070]

[0071] In formula (11), design k p =10.

[0072] Step 6, design the final mill roll gap setting value: according to the mill roll gap setting value S of the compensation strip thickness dynamic coefficient deviation m (t) The mill roll gap setting value S which is proportional to the strip thickness control deviation feedback p (t), add them together to get the final setting value of the mill roll gap. After substituting the above parameters into formula (6), we get formula (12):

[0073]

[0074] In order to further verify the applicability of the method of the present invention, the dynamic coefficient deviation of the plate thickness is set to Δ =0.2, comparing the strip thickness control effect of the method of the present invention with that of the method not using the strip thickness dynamic coefficient deviation estimation and compensation method.

[0075] Depend on Figure 3 The strip thickness control results in the paper show that when the strip thickness dynamic coefficient deviation estimation and compensation method is not used, the actual strip thickness has a deviation of about 0.1mm from the target value; when the method of the present invention is used, the deviation of the actual strip thickness from the target value is within 0.01mm. Figure 4 The steady-state error of the strip thickness control in the experiment shows that: without using the method of estimating and compensating the deviation of the dynamic coefficient of the strip thickness, the steady-state error of the strip thickness control oscillates in the range of -60μm to -80μm; with the method of the present invention, the steady-state error of the strip thickness control is in the range of -5μm to +5μm. In comparison, it is further proved that the method of the present invention can improve the control accuracy of the strip thickness.

[0076] 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 robust and adaptive strip thickness control method, characterized in that: The following steps are involved: Step 1, establish a dynamic system of plate thickness considering unknown disturbance interference; Step 2, establishing the strip thickness control deviation; Step 3, design an estimated value of the dynamic coefficient deviation of the plate thickness; Step 4, designing a setting value of the mill roll gap that compensates for the deviation of the dynamic coefficient of the plate and strip thickness; Step 5, designing a rolling mill roll gap setting value for proportional feedback of the strip thickness control deviation amount; Step 6, design the final mill roll gap setting value.

2. The robust adaptive strip thickness control method according to claim 1, characterized in that: In step 1, the specific steps of establishing a dynamic system of plate and strip thickness considering unknown disturbance interference are: according to the rolling mill bounce equation and the rolling mill roll gap adjustment system, a dynamic system of plate and strip thickness considering unknown disturbance interference is established, as shown in formula (1): In formula (1), For the derivation operation, 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, M∈R is the mill stiffness coefficient, and a Δ ∈R is the deviation of the dynamic coefficient of strip thickness caused by disturbance.

3. The robust adaptive strip thickness control method according to claim 1, characterized in that: In step 2, the formula for establishing the plate strip thickness control deviation is shown in formula (2): H e (t)=H(t)-H r (2) In formula (2), H(t)∈R is the thickness of the plate at time t, H r ∈R is the target value of the strip rolling thickness, H e (t)∈R is the thickness control deviation of the plate at time t.

4. The robust adaptive strip thickness control method according to claim 1, characterized in that: In step 3, the specific process of estimating the deviation of the dynamic coefficient of the designed plate thickness is shown in formula (3): In formula (3), k a ∈R is the dynamic estimation coefficient of the dynamic coefficient deviation of the plate thickness, H(t)∈R is the plate thickness at time t, H e (t)∈R is the plate thickness control deviation at time t, It is the estimated value of the dynamic coefficient deviation of the plate thickness at time t.

5. The robust adaptive strip thickness control method according to claim 1, characterized in that: In step 4, the specific process of designing the rolling mill roll gap setting value for compensating the strip thickness dynamic coefficient deviation is as follows: according to the strip thickness dynamic system considering unknown disturbance interference and the estimated value of the strip thickness dynamic coefficient deviation, the rolling mill roll gap setting value for compensating the strip thickness dynamic coefficient deviation is designed, as shown in formula (4): In formula (4), H(t)∈R is the thickness of the plate at time t, S m (t)∈R is the mill roll gap setting value for compensating the dynamic coefficient deviation of the strip thickness at time t, P∈R is the rolling pressure, M∈R is the mill stiffness coefficient, a∈R is the dynamic coefficient of the strip thickness, It is the estimated value of the dynamic coefficient deviation of the plate thickness at time t.

6. The robust adaptive strip thickness control method according to claim 1, characterized in that: In step 5, the rolling mill roll gap setting value of the designed strip thickness control deviation proportional feedback is shown in formula (5): In formula (5), S p (t)∈R is the rolling mill roll gap setting value of the proportional feedback of the strip thickness control deviation at time t, H e (t)∈R is the plate thickness control deviation at time t, a∈R is the plate thickness dynamic coefficient, k p ∈R is the proportional feedback gain coefficient.

7. The robust adaptive strip thickness control method 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 of the compensation strip thickness dynamic coefficient deviation and the rolling mill roll gap setting value of the strip thickness control deviation proportional feedback to obtain the final rolling mill roll gap setting value, see formula (6): S(t)=S m (t)+S p (t) (6) In formula (6), S m (t) is the mill roll gap setting value for compensating the dynamic coefficient deviation of the strip thickness, S p (t) is the rolling mill roll gap setting value for proportional feedback of the strip thickness control deviation.

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