Rolling Mill Speed Ratio Control for Tail-End Tension Changes
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Solution Overview
Problem
In rolling mills, the tail end and sections next to the tail end of rolling materials often exit with a larger cross-section, causing tension changes that result in sections being outside permitted tolerances, leading to scrap material, and manual adjustments to rolling speed by users yield unsatisfactory results.
Innovation Solution
The method involves keeping a predetermined speed ratio constant until the tail end reaches a specific location upstream of the front group of roll stands and then increasing it according to a predetermined function, using a PID controller to control the rolling speed, tension, and cross-section, and optionally incorporating a feed forward control signal and adapting the function based on detected speed deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the rolling speed of the rear group of roll stands is manually adjusted by a user, then the tension in the rolling material can be adapted, but the results are often unsatisfactory and dependent on user experience
Solution Approach 1:
The system automatically detects run-out speed and run-in speed, calculates the predetermined value, and adjusts the rolling speed without manual intervention. The control device performs the entire adjustment process autonomously based on detected speeds, eliminating dependency on user experience while maintaining precise cross-section control
Solution Approach 2:
The control device continuously detects run-out speed from the front group and run-in speed from the rear group, uses this feedback to calculate the predetermined value, and dynamically adjusts the rolling speed accordingly. This closed-loop feedback system ensures precise tension control and cross-section tolerance compliance
2Manufacturing precision
If the rolling speed relation is kept constant, then the control is simplified, but the tension change during tail end rolling causes cross-section to exceed tolerances
Solution Approach 1:
The predetermined value is not fixed but dynamically adjusted based on the detected run-out speed and run-in speed. The system transitions from static constant-speed control to dynamic speed adjustment, allowing the rolling speed relation to adapt to changing tension conditions during tail end rolling while maintaining manageable control through automated calculation
3Manufacturing precision
If the predetermined value is increased according to a predetermined function after the tail end reaches a specific location, then the tail end cross-section is controlled within tolerances, but the control system becomes more complex
Solution Approach 1:
The control device detects when the tail end reaches a specific location upstream of the front group and preliminarily increases the predetermined value according to a predetermined function before the tail end enters the front group. This preliminary action prepares the system to handle the upcoming tension change, ensuring cross-section tolerance compliance while managing control complexity through structured timing
Data Source
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AI summary
A rolling material (1) is rolled firstly in roll stands (3) of a front group (2) of roll stands (3) of a rolling mill and then in roll stands (5) of rear group (4) of roll stands (5) of said rolling mill. During rolling of front sections (12) of said rolling material (1) in the roll stands (5) of said rear group (4) of roll stands (5), rear sections (13) of said rolling material (1) are rolled in the roll stands (3) of said front group (2) of roll stands (3). A run-out speed (v1) with which the rolling material (1) is exiting said front group (2) of roll stands (3) is detected. A run-in speed (v2) with which the rolling material (1) is entering said rear group (4) of roll stands (5) is detected. A rolling speed (v) with which the rear group (4) of roll stands (5) is driven is controlled by a controller (16) such that a relation (V) of the run-in speed (v2) to the run-out speed (v1) equals a predetermined value (a). Said predetermined value (a) is kept constant until a time point (t0) at which a tail end (18) of the rolling material (1) reaches a predetermined location upstream of the front group (2) of roll stands (3), and is changed according to a predetermined function after said time point (t0).