A method for controlling elongation of a continuous annealing six-high cold rolling skin pass mill

Abstract

This invention discloses a method for controlling the elongation rate of a continuous six-roll cold rolling leveling mill, comprising the following steps: collecting actual production data of the cold rolling production line; monitoring the tracking data of the cold rolling production line, using a field control PLC to read the strip production data, and establishing a linear regression model between the strip thickness, width, target elongation, and PID control parameters; selecting the optimal PID control parameters based on the target elongation rate of the strip, and using a PID controller to regulate the elongation rate of the strip, allowing the strip to enter the leveling process; detecting whether the elongation rate of the strip changes during the leveling process, and if it changes, readjusting the PID control parameters; if it does not change, maintaining the current PID control parameters until the end of the strip completes the leveling process. This method can automatically adjust the strip elongation rate according to different specifications of strip, reducing overshoot and adjustment time for different steel grades, reducing the mismatch between the beginning and end elongation lengths, and improving the strip yield.

Description

Technical Field

[0001] This invention relates to the field of cold-rolled strip steel production parameter control, specifically to a method for controlling the elongation of a continuous six-roll cold rolling leveling mill. Background Technology

[0002] The elongation rate of a six-roll continuous annealing cold rolling mill is a key process parameter for cold-rolled strip steel, determining the final performance of the strip product. The main control parameters in the leveling process are the leveling rolling force and the tension before and after leveling. The primary control objectives of the leveling process are the elongation rate and surface quality of the coil, and the quality of elongation rate control directly affects the product quality. During production, the strip elongation rate exhibits characteristics such as lag and mismatch with the strip thickness and width.

[0003] Currently, the most widely used control strategy in practical applications is the conventional PID (proportional, integral, derivative) control strategy. Its principle is simple and its stability is good. However, conventional PID control usually involves pre-setting fixed basic parameters. Offline tuning of PID parameters has been the subject of various control studies in cold-rolled strip steel production.

[0004] For example, Chinese patent document with application number 201310139128.1 discloses a method for accurately controlling the elongation of strip steel when the weld seam passes through a leveling machine. This method quickly and accurately controls the elongation value of the strip steel by adjusting the traveling speed of the strip steel before the weld seam passes through the leveling machine and the rolling force after the weld seam passes through the leveling machine, thereby improving the yield of the strip steel.

[0005] For example, a method for controlling the elongation fluctuation of a leveling machine is disclosed in Chinese patent document with application number 201510765500.9. The method subdivides the PID control parameters corresponding to different strip speeds, thereby improving the control accuracy of the elongation.

[0006] For example, a fuzzy PID controller and its control method based on genetic algorithm are disclosed in Chinese patent document with application number 201210521099.0. The fuzzy control algorithm is used to control the controlled object, and the three parameters of the PID controller are generated according to the fuzzy principle.

[0007] The above control methods can meet the initial operating conditions of the equipment well. However, due to the limitations of the PID control parameter tuning method, the above control methods cannot adapt to the frequent changes in the field. For example, when the thickness and width of the strip change, the strip elongation cannot be well controlled. There is a lack of a control method in the existing technology that can automatically adjust the strip elongation according to strips of different widths and thicknesses. Summary of the Invention

[0008] The purpose of this invention is to provide a method for controlling the elongation of a continuous six-roll cold rolling mill, which can automatically adjust and control the elongation of strip steel according to different specifications and parameters, reduce the overshoot and adjustment time of elongation control for different steel grades, reduce the mismatch between the head and tail elongation lengths, and improve the strip steel yield.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for controlling the elongation of a continuous six-roll cold rolling mill includes the following steps:

[0011] Step 1: Collect actual production data from the cold rolling production line. The actual production data shall include at least strip thickness, strip width, and target strip elongation.

[0012] Step Two: Monitor the tracking data of the cold rolling production line. Use the on-site control PLC to read the thickness, width, and target elongation of the strip. When the weld position of the next coil of strip approaches the leveling machine, use the thickness, width, and target elongation of the next coil of strip as input values ​​and the PID control parameters of the next coil of strip as output values. Establish a linear regression model between the input and output values. The linear regression model is as follows:

[0013] K p =1.58t*10 -1 -1.59w*10 -4 +4.99e*10 -1 ,

[0014] K i =9.98t*10 -2 -5.95w*10 -4 -1.65e*10 -2 ,

[0015] K d = -2.05t * 10 -4 +4.61w*10 -7 +1.18e*10 -4 ,

[0016] Where t is the strip thickness, w is the strip width, e is the target elongation of the strip, and K p K i K d These are the three control parameters of a PID controller: proportional, derivative, and integral.

[0017] Step 3: Store the PID control parameters obtained in Step 2 into the PLC data block. When the weld seam between the next coil of strip and the current coil of strip reaches the leveling machine, select the optimal PID control parameters according to the target elongation of the strip, and use the PID controller to regulate the elongation of the strip. The strip then enters the leveling process.

[0018] Step 4: Check if the elongation of the strip changes during the leveling process. If it does, return to Step 2 and readjust the PID control parameters to the optimal parameters that match the current strip thickness and width. If it does not change, maintain the current PID control parameters and continue the strip leveling process until the end of the strip is leveled. Then return to Step 2 and calculate the PID control parameters for the new coil of strip.

[0019] Preferably, in step one, the actual production data of the cold rolling production line is directly collected by the on-site control PLC.

[0020] Preferably, in step two, when the weld seam of the next strip and the current strip are close to the leveling machine, the distance between the weld seam and the leveling machine is 50m.

[0021] The beneficial effects of this invention are as follows: This method provides relevant parameters of the PID controller for strip steel of different widths, thicknesses and target elongation rates when passing through a continuous six-roll cold rolling leveling mill, thereby reducing the overshoot and adjustment time of controlling the elongation rate of different steel grades, reducing the mismatch between the head and tail elongation lengths, and improving the strip steel yield. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a six-roll cold rolling leveling machine in an embodiment of the present invention.

[0023] Figure 2 This is a fluctuation curve diagram of the PID control parameter adjustment corresponding to the elongation control method in the embodiments of the present invention and the traditional technology. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will now be described with reference to the accompanying drawings.

[0025] A method for controlling the elongation of a continuous six-roll cold rolling mill includes the following steps:

[0026] Step 1: Collect actual production data from the cold rolling production line. The actual production data shall include at least strip thickness, strip width, and target strip elongation.

[0027] Step Two: Monitor the tracking data of the cold rolling production line. Use the on-site control PLC to read the thickness, width, and target elongation of the strip. When the weld position of the next coil of strip approaches the leveling machine, use the thickness, width, and target elongation of the next coil of strip as input values ​​and the PID control parameters of the next coil of strip as output values. Establish a linear regression model between the input and output values. The linear regression model is as follows:

[0028] K p =1.58t*10 -1 -1.59w*10 -4 +4.99w*10 -1 ,

[0029] K i =9.98t*10 -2 -5.95w*10 -4 -1.65e*10 -2 ,

[0030] K d = -2.05t * 10 -4 +4.61w*10 -7 +1.18e*10 -4 ,

[0031] Where t is the strip thickness, w is the strip width, e is the target elongation of the strip, and K p K i K d These are the three control parameters of a PID controller: proportional, derivative, and integral.

[0032] Step 3: Store the PID control parameters obtained in Step 2 into the PLC data block. When the weld seam between the next coil of strip and the current coil of strip reaches the leveling machine, select the optimal PID control parameters according to the target elongation of the strip, and use the PID controller to regulate the elongation of the strip. The strip then enters the leveling process.

[0033] Step 4: Check if the elongation of the strip changes during the leveling process. If it does, return to Step 2 and readjust the PID control parameters to the optimal parameters that match the current strip thickness and width. If it does not change, maintain the current PID control parameters and continue the strip leveling process until the end of the strip is leveled. Then return to Step 2 and calculate the PID control parameters for the new coil of strip.

[0034] Preferably, in step one, the actual production data of the cold rolling production line is directly collected by the on-site control PLC.

[0035] Preferably, in step two, when the weld seam of the next strip and the current strip are close to the leveling machine, the distance between the weld seam and the leveling machine is 50m.

[0036] Combination Figure 1 As shown, taking the production process of a strip steel with a thickness of 0.808 mm, a width of 1353 mm, and a target elongation of 1 as an example, the local control PLC is used to read the thickness, width, and target elongation of the strip steel. When the strip steel is about to enter the six-roll cold rolling mill, the PID control parameter output calculated using the linear regression model is K. p =0.4, K i =-0.7, K d =0.0006, and then based on the PID control parameters calculated by the linear regression model, the PID controller is used to regulate the elongation of the strip. Please refer to [reference needed]. Figure 2 , Figure 2 This is a graph showing the fluctuation curves of the PID control parameters corresponding to the elongation control method described in this invention and the conventional technology. Curve A is the fluctuation curve of the PID control parameters adjusted in this method, and curve B is the fluctuation curve of the PID control parameters adjusted in the conventional technology. After the strip steel passes through the six-roll cold rolling mill, it is... Figure 2 It can be seen that, within the same time period, the PID control parameter adjustment of curve A is more precise and efficient than that of curve B, reducing the overshoot of the strip. Compared with the adjustment time used by curve B, the more precise PID control parameters of curve A reduce the adjustment time of the strip elongation. In summary, using the control method described in this invention to control the strip elongation can effectively reduce the overshoot and adjustment time in the control process when processing strips of different specifications, while also reducing the mismatch between the beginning and end elongation lengths and improving the strip yield.

Claims

1. A method for controlling the elongation of a continuous six-roll cold rolling mill, characterized in that: Includes the following steps: Step 1: Collect actual production data from the cold rolling production line. The actual production data shall include at least strip thickness, strip width, and target strip elongation. Step Two: Monitor the tracking data of the cold rolling production line. Use the on-site control PLC to read the thickness, width, and target elongation of the strip. When the weld position of the next coil of strip approaches the leveling machine, use the thickness, width, and target elongation of the next coil of strip as input values ​​and the PID control parameters of the next coil of strip as output values. Establish a linear regression model between the input and output values. The linear regression model is as follows: K p =1.58t*10 -1 -1.59w*10 -4 +4.99e*10 -1 , K i =9.98t*10 -2 -5.95w*10 -4 -1.65e*10 -2 , K d =-2.05t*10 -4 +4.61w*10 -7 +1.18e*10 -4 , Where t is the strip thickness, w is the strip width, e is the target elongation of the strip, and K p K i K d These are the three control parameters of a PID controller: proportional, derivative, and integral. Step 3: Store the PID control parameters obtained in Step 2 into the PLC data block. When the weld seam between the next coil of strip and the current coil of strip reaches the leveling machine, select the optimal PID control parameters according to the target elongation of the strip, and use the PID controller to regulate the elongation of the strip. The strip then enters the leveling process. Step 4: Check if the elongation of the strip changes during the leveling process. If it does, return to Step 2 and readjust the PID control parameters to the optimal parameters that match the current strip thickness and width. If it does not change, maintain the current PID control parameters and continue the strip leveling process until the end of the strip is leveled. Then return to Step 2 to calculate the PID control parameters for the new coil of strip.

2. The elongation control method for a continuous six-roll cold rolling mill according to claim 1, characterized in that: In step one, the actual production data of the cold rolling production line is directly collected by the on-site control PLC.

3. The elongation control method for a continuous six-roll cold rolling mill according to claim 1, characterized in that: In step two, when the weld seam of the next strip and the current strip are close to the leveling machine, the distance between the weld seam and the leveling machine is 50m.

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