A method for controlling segmented cooling of a roll based on pi control

Abstract

The present application relates to strip production technical field, especially to a kind of based on PI control's roll segmented cooling control method, specifically including the following steps: step one, determine segmented cooling input parameter;Step two, establish the relationship between cooling liquid injection variation and plate shape deviation value, convert plate shape deviation value into the cooling liquid injection variation of spray head;Step three, limit maximum and minimum cooling liquid injection variation;Step four, using PI control regulates cooling liquid injection variation;Step five, increase a manual control and PI automatic control switching procedure, and the cooling liquid injection amount of basic cooling liquid injection amount and PI control or the cooling liquid injection amount of manual control cooling liquid injection variation is added to form the cooling liquid injection amount of each spray head actual output;Step six, using cooling liquid over-injection control determines final cooling liquid injection amount, using the segmented cooling control method of the present application, can reduce the roll gap variation caused by temperature change of roll, significantly reduce the deviation of plate shape.

Description

Technical Field

[0001] This invention relates to the field of strip steel production technology, and in particular to a method for segmented cooling control of rolls based on PI control. Background Technology

[0002] During the rolling process of cold-rolled strip steel, the friction between the rolls and between the rolls and the strip generates a large amount of heat. This heat causes uneven thermal convexity on the surface of the work rolls, which in turn alters the roll gap distribution, ultimately resulting in uneven, high-order shape defects in the strip. However, conventional shape control methods, such as roll tilting, roll lateral movement, and roll bending control, are difficult to eliminate localized and uneven shape defects. In modern shape control, segmented roll cooling control is often used to eliminate localized high-order shape defects. The basic principle of segmented cooling is that work roll emulsion segmented cooling nozzles are installed at the inlet of the mill. The nozzles spray coolant of the required concentration for the rolling process onto the surface of the rolls and strip steel at a certain flow rate and pressure. The controller controls the thermal convexity change of the corresponding work roll area by individually controlling the opening and closing of each nozzle, thereby effectively eliminating irregular shape, localized high-order shape defects, and shape defects that cannot be controlled by mechanical shape adjustment mechanisms (tilting, roll bending, roll shifting, etc.). Traditional segmented cooling control methods include fuzzy control and PI control. While fuzzy control offers good real-time performance and accuracy, its drawbacks include complex control principles, large program size, difficulty in porting to different platforms, and challenging system maintenance. Traditional PI control, compared to fuzzy control, boasts lower control costs, simpler control principles, and a more mature control methodology, making it widely used in various practical panel control applications. However, traditional PI control involves individual nozzle control, which can lead to interference between adjacent nozzles' coolant injection rates, resulting in poor panel control accuracy. Summary of the Invention

[0003] The purpose of this invention is to provide a PI-based method for segmented cooling control of rolling mill rolls, so as to solve the technical problems existing in the background art.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: A PI-based method for segmented cooling control of rolling mill rolls includes the following steps: S1. Determine the input parameters for segmented cooling; S2. Establish the relationship between the coolant injection variation and the plate shape deviation value, and convert the plate shape deviation value into the coolant injection variation of the nozzle; S3, Limits the maximum and minimum coolant injection variation; S4. Use PI control to regulate the amount of coolant injected; S5. Add a manual control and PI automatic control switching program, and add the basic coolant injection quantity and the coolant injection change quantity controlled by PI or the coolant injection change quantity controlled by manual to form the actual coolant injection quantity output by each nozzle. S6. Use coolant over-injection control to determine the final coolant injection amount.

[0005] Furthermore, the input parameter in S1 is specifically: the maximum reference value of the coolant injection quantity. and minimum reference value Plate shape deviation value ; conversion factor , Basic coolant injection volume The basic proportional gain of a PID controller The basic integral gain of a PID controller ; Coolant over-injection parameters , .

[0006] Furthermore, the formula for calculating the plate shape deviation value in S2 is as follows: ,in, For ideal plate shape values, This represents the actual plate shape value; the conversion formula between plate shape deviation and coolant injection variation is: ,in, This is the plate shape deviation value. As the conversion factor, This represents the change in coolant injection volume.

[0007] Furthermore, the allowable limits for the maximum and minimum coolant injection variations in S3 are as follows: ; ;in, Minimum coolant injection quantity, This is the maximum coolant injection volume. Based on the amount of coolant injected. To minimize the change in coolant injection volume, This represents the maximum variation in coolant injection.

[0008] Furthermore, the specific control flow of the PI control in S4 is as follows: S41. Check the change in coolant injection volume. If the coolant injection variation is within the range of the maximum and minimum values, then if the coolant injection variation is greater than the maximum value, then the outhi mode is activated, where outhi directly outputs the coolant injection variation as the maximum output coolant injection variation. If the coolant injection variation is less than the minimum value, then the outlo mode is activated, where outlo directly outputs the coolant injection variation as the minimum output coolant injection variation. If the coolant injection variation is within the variable range, then proceed to the next step. S42, Coolant Injection Variation The proportional control calculation value is obtained through proportional control calculation. ; S43. Determine the coolant injection variation as the input value. Whether to use integral control mode depends on whether the coolant injection variation is within the variable range. Integral control calculations should be used to obtain the integral control value. ; In S44 and S43, the integral control mode also takes into account the state of manual input. If there is manual input, the value after integral control is converted into the manual input value. S45, Proportional Control Calculation Value And integral control calculation value The sums become the final value after proportional-integral control. ; S46. Limit the output range; the total proportional integral value is limited to the adjustable range. The final output is the change in coolant injection volume controlled by PI. .

[0009] Furthermore, in S4, during PI control, Indicates the change in coolant injection volume , This indicates the change in coolant injection after PI control; the PI control formula is: ,in, This is the basic proportional gain of the PID controller. This represents the basic integral gain of the PID controller. The PI control formula is a continuous integral formula, which needs to be discretized in actual PLC control. The discretized formula is as follows: ,in, For computer sampling sequence number, The time required for the computer to take one sample. This is the basic proportional gain of the PID controller. This is the basic integral gain of the PID controller.

[0010] Furthermore, the proportional control calculation value in S42 The proportional formula is: ,in, This represents the change in coolant injection volume. The set basic proportional gain, Changes in coolant injection The value calculated by proportional control; the value calculated by integral control in S43 The integral formula is: ,in, Changes in coolant injection , The time required for the computer to take one sample. For computer sampling sequence number, The basic integral gain is set. Changes in coolant injection The value calculated by integral control; the final value in S45. The calculation formula is: ,in, Changes in coolant injection The value calculated by integral control. Changes in coolant injection The value calculated after proportional control.

[0011] Furthermore, the formula for calculating the actual coolant injection volume of each nozzle in S5 is as follows: or ,in, This represents the change in coolant injection after PI control. Based on the amount of coolant injected. This refers to the total coolant injection volume. To manually control the amount of coolant injected.

[0012] Furthermore, the coolant over-injection control in S6 specifically includes: , , ,in, For overspray parameters, , , Let it be an intermediate variable; , , are variable, where This is the nozzle serial number. , , Coolant injection volume before over-injection control , This refers to the amount of coolant injected after over-spray control. The maximum value is 43, the minimum value is 1, and the total number of nozzles is 44. , , ; , .

[0013] Compared with the prior art, the beneficial effects of the present invention are: Compared with the traditional PI control method, the PI-based segmented cooling control method for rolls provided by this invention adds an over-spray control system, which effectively solves the problem of mutual influence of coolant spray volume between adjacent nozzles, reduces roll gap changes caused by temperature variations, and significantly reduces plate shape deviation. Attached Figure Description

[0014] Figure 1 This is the overall flowchart of the present invention; Figure 2 This is the PI control flowchart of the present invention; Figure 3 This is a schematic diagram of coolant injection in this invention. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0016] See Figures 1-3 As shown, a segmented cooling control method for rolls based on PI control specifically includes the following steps: Step 1: Segmented cooling of the emulsion is an important means of controlling the strip shape. Segmented cooling can effectively control high-order strip shape defects. Before implementing segmented cooling control, it is necessary to determine the various parameters required for segmented cooling control and input the parameters into the local storage of the coolant injection system. The following are the various parameters required; If the coolant spray volume from the nozzle is too large, the strip crown will be less than the ideal strip crown, making it difficult to control the strip shape deviation using segmented cooling methods. If the coolant spray volume is too small, the basic cooling requirements of the strip cannot be met. Therefore, a maximum reference value for the coolant spray volume needs to be set. and minimum reference value To limit the output range of coolant injection; Plate shape deviation value is obtained through plate shape sensor. The analog signal is then converted into a digital signal by an analog-to-digital converter for subsequent program operations; Set conversion factor , This factor can convert the plate shape deviation value into the coolant injection variation, which is the basic parameter for subsequent segmented cooling. Set the basic coolant injection volume This value is the amount of coolant injected before PI control and is a constant value to ensure the cooling of the rolls and strip. Setting the basic system gain of the PID controller: Basic proportional gain and basic integral gain These initial gains take into account rolling parameters such as strip speed, roll gap shape, and roll gap distance. PI control controls the coolant injection rate of a single nozzle. However, because the nozzles are close together, their injection rates can affect each other. Therefore, over-spray control is required, where the over-spray parameter is... , .

[0017] Step 2: During the strip shape control process, when deviations occur between the ideal and actual strip shape values, the PID controller needs to control the coolant injection rate of the nozzles. Therefore, it is necessary to establish a relationship between the coolant injection rate change and the strip shape deviation value. When the strip shape deviation value increases, the strip crown decreases, thus requiring a reduction in coolant injection volume or shutdown of the nozzles. Therefore, the relationship between the strip shape deviation value and the coolant injection rate increment is inverse, hence the conversion factor... The formula for calculating the plate shape deviation is: ,in, For ideal plate shape values, This represents the actual plate shape value; the conversion formula between plate shape deviation and coolant injection variation is: ,in, This is the plate shape deviation value. As the conversion factor, This represents the change in coolant injection volume.

[0018] Step 3: During PI control, the coolant injection quantity cannot exceed the specified maximum value. However, the PID controller controls the coolant injection variation, therefore, a relationship needs to be established between the maximum and minimum coolant injection variation and the maximum and minimum coolant injection quantity. These limits are enforced by the PID controller; the formulas for the maximum and minimum allowable coolant injection variation are: ; ;in, Minimum coolant injection quantity, This is the maximum coolant injection volume. Based on the amount of coolant injected. To minimize the change in coolant injection volume, This represents the maximum variation in coolant injection.

[0019] Step 4: When a transient change in the plate shape deviation is detected, PI control is implemented. This control operates on a single nozzle, with proportional and integral control calculated separately and then summed to obtain the final proportional-integral control change in coolant injection. The specific PI control flowchart is shown below. Figure 2 As shown. In PI control, Indicates the change in coolant injection volume , This indicates the change in coolant injection after PI control; the PI control formula is: ,in, This is the basic proportional gain of the PID controller. This represents the basic integral gain of the PID controller. The PI control formula is a continuous integral formula, which needs to be discretized in actual PLC control. The discretized formula is as follows: ,in, For computer sampling sequence number, The time required for the computer to take one sample. This is the basic proportional gain of the PID controller. This is the basic integral gain of the PID controller; The specific control process of PI control is as follows: 1) Check the change in coolant injection volume If the coolant injection variation is within the range of the maximum and minimum values, then if the coolant injection variation is greater than the maximum value, then the outhi mode is activated, where outhi directly outputs the coolant injection variation as the maximum output coolant injection variation. If the coolant injection variation is less than the minimum value, then the outlo mode is activated, where outlo directly outputs the coolant injection variation as the minimum output coolant injection variation. If the coolant injection variation is within the variable range, then proceed to the next step. 2) Changes in coolant injection volume The proportional control calculation value is obtained through proportional control calculation. ; 3) Determine the coolant injection variation as the input value. Whether to use integral control mode depends on whether the coolant injection variation is within the variable range. Integral control calculations should be used to obtain the integral control value. ; 4) The integral control mode in the previous step also takes into account the state of manual input. If there is manual input, the value after integral control is converted into the value of manual input. 5) Proportional control calculation value And integral control calculation value The sums become the final value after proportional-integral control. ; 6) Limit the output range; the total proportional integral value is limited to the adjustable range. The final output is the change in coolant injection volume controlled by PI. For a detailed flowchart of PI control, please see [link / description]. Figure 2 .

[0020] Step 5: To achieve greater control versatility and flexibility, add a manual control and PI automatic control switching program, and adjust the base coolant injection quantity and the coolant injection variation controlled by the PI or the manual control. The sum of these values ​​constitutes the actual coolant injection volume from each nozzle. The formula for calculating the actual coolant injection volume of each nozzle is as follows: or ,in, This represents the change in coolant injection after PI control. Based on the amount of coolant injected. This refers to the total coolant injection volume. To manually control the amount of coolant injected.

[0021] Step Six: The above process controls the coolant injection volume of a single nozzle. In actual segmented cooling control, the distance between nozzles is generally quite close, causing the emulsion sprayed from one nozzle to enter the control area of ​​other nozzles, affecting the final plate shape control. Therefore, over-spray control needs to be applied to each nozzle to limit the amount of mutual influence between nozzles. After applying over-spray control to the nozzles, minimum and maximum limits need to be set for the coolant injection volume. The minimum limit is... (Minimum coolant injection volume), maximum limit is: (Maximum coolant injection volume); The specific measures for controlling excessive coolant injection are as follows: , , ,in, For overspray parameters, , , Let it be an intermediate variable; , , are variable, where This is the nozzle serial number. , , Coolant injection volume before over-injection control , This refers to the amount of coolant injected after over-spray control. The maximum value is 43, the minimum value is 1, and the total number of nozzles is 44. , , ; , .

[0022] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for segmented cooling control of rolling mill rolls based on PI control, characterized in that, Specifically, the following steps are included: S1. Determine the input parameters for segmented cooling; The input parameter in S1 is specifically: the maximum reference value of the coolant injection quantity. and minimum reference value Plate shape deviation value ; conversion factor , Basic coolant injection volume The basic proportional gain of a PID controller The basic integral gain of a PID controller ; Coolant over-injection parameters , ; S2. Establish the relationship between the coolant injection variation and the plate shape deviation value, and convert the plate shape deviation value into the coolant injection variation of the nozzle; S3, Limits the maximum and minimum coolant injection variation; S4. Use PI control to regulate the amount of coolant injected; S5. Add a manual control and PI automatic control switching program, and add the basic coolant injection quantity and the coolant injection change quantity controlled by PI or the coolant injection change quantity controlled by manual to form the actual coolant injection quantity output by each nozzle. S6. Use coolant over-injection control to determine the final coolant injection amount; The coolant over-spray control in S6 specifically refers to: , , ,in, For overspray parameters, , , Let it be an intermediate variable; , , are variable, where This is the nozzle serial number. , , Coolant injection volume before over-injection control , This refers to the amount of coolant injected after over-spray control. The maximum value is 43, the minimum value is 1, and the total number of nozzles is 44. , , ; , .

2. The method for segmented cooling control of rolls based on PI control according to claim 1, characterized in that: The formula for calculating the plate shape deviation value in S2 is as follows: ,in, For ideal plate shape values, This represents the actual plate shape value; the conversion formula between plate shape deviation and coolant injection variation is: ,in, This is the plate shape deviation value. As the conversion factor, This represents the change in coolant injection volume.

3. The method for segmented cooling control of rolls based on PI control according to claim 2, characterized in that: The formulas for the allowable limits on the maximum and minimum coolant injection variations in S3 are as follows: ; ;in, Minimum coolant injection quantity, This is the maximum coolant injection volume. Based on the amount of coolant injected. To minimize the change in coolant injection volume, This represents the maximum variation in coolant injection.

4. The method for segmented cooling control of rolls based on PI control according to claim 3, characterized in that: The specific control flow of PI control in S4 is as follows: S41. Check the change in coolant injection volume. Whether it is within the range of the maximum and minimum values ​​that can be changed; if the change in coolant injection is greater than the maximum change in coolant injection, then the outhi mode is enabled, and outhi directly outputs the change in coolant injection as the maximum output change in coolant injection. If the coolant injection variation is less than the minimum coolant injection variation, then the outlo mode is activated. outlo directly outputs the coolant injection variation as the minimum output coolant injection variation. If the amount of coolant injection variation is within the variable range, proceed to the next step; S42, Coolant Injection Variation The proportional control calculation value is obtained through proportional control calculation. ; S43. Determine the coolant injection variation as the input value. Whether to use integral control mode depends on whether the coolant injection variation is within the variable range. Integral control calculations should be used to obtain the integral control value. ; In S44 and S43, the integral control mode also takes into account the state of manual input. If there is manual input, the value after integral control is converted into the manual input value. S45, Proportional Control Calculation Value And integral control calculation value The sums become the final value after proportional-integral control. ; S46. Limit the output range; the total proportional integral value is limited to the adjustable range. The final output is the change in coolant injection volume controlled by PI. .

5. The method for segmented cooling control of rolls based on PI control according to claim 4, characterized in that: S4, in PI control, Indicates the change in coolant injection volume , This indicates the change in coolant injection after PI control; the PI control formula is: ,in, This is the basic proportional gain of the PID controller. This represents the basic integral gain of the PID controller. The PI control formula is a continuous integral formula, which needs to be discretized in actual PLC control. The discretized formula is as follows: ,in, For computer sampling sequence number, The time required for the computer to take one sample. This is the basic proportional gain of the PID controller. This is the basic integral gain of the PID controller.

6. The method for segmented cooling control of rolls based on PI control according to claim 4, characterized in that: The proportional control calculation value in S42 The proportional formula is: ,in, This represents the change in coolant injection volume. The set basic proportional gain, Changes in coolant injection The value calculated by proportional control; the value calculated by integral control in S43 The integral formula is: ,in, Changes in coolant injection , The time required for the computer to take one sample. For computer sampling sequence number, The basic integral gain is set. Changes in coolant injection The value calculated by integral control; the final value in S45. The calculation formula is: ,in, Changes in coolant injection The value calculated by integral control. Changes in coolant injection The value calculated after proportional control.

7. The method for segmented cooling control of rolls based on PI control according to claim 6, characterized in that: The formula for calculating the actual coolant injection volume of each nozzle in S5 is as follows: or ,in, This represents the change in coolant injection after PI control. Based on the amount of coolant injected. This refers to the total coolant injection volume. To manually control the amount of coolant injected.

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