Stainless Steel Strip Flatness Control in Sendzimir Rolling
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Solution Overview
Problem
Existing methods for measuring and adjusting flatness and strip tension in high-grade steel strips during cold rolling in cluster mills, such as 20-roll Sendzimir rolling mills, fail to accurately account for all sources of errors, leading to suboptimal product quality and reduced rolling speed.
Innovation Solution
A method that compares a tension vector with a reference curve, decomposes the flatness error into proportional tension vectors using an analytical module, and supplies these components to control modules to actuate corresponding actuators, while also considering residual errors and using orthogonal components to independently control strip edges, ensuring stable rolling with minimal breakage and increased speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional flatness measurement and adjustment methods are used, then the rolling process can be maintained, but flatness errors are not accurately accounted for leading to suboptimal product quality
Solution Approach 1:
The flatness error curve is decomposed into multiple orthogonal tension vectors that represent different error components. This segmentation allows each component to be measured and corrected independently, improving both measurement precision and manufacturing precision by addressing specific error sources rather than treating flatness as a single parameter.
Solution Approach 2:
Orthogonal tension vectors serve as intermediaries between the raw flatness measurement and the actuator control signals. These vectors transform the complex flatness error into manageable components that can be systematically corrected, enabling more precise flatness control while maintaining system stability.
2Manufacturing precision
If multiple actuators with different time responses are used to control flatness, then comprehensive flatness adjustment is possible, but the different time responses create coordination difficulties
Solution Approach 1:
The control system dynamically adapts to the different time responses of multiple actuators by using orthogonal decomposition. Each actuator receives control signals tailored to its specific characteristics, allowing comprehensive flatness control while simplifying coordination through mathematical decoupling of the control problem.
Solution Approach 2:
The system changes the parameter representation from a single flatness error value to multiple orthogonal tension vector components. This parameter transformation allows each actuator to be controlled based on its specific dynamics, reducing coordination complexity while maintaining comprehensive control capability.
3Adaptability or versatility
If manual adjustment of actuators is performed, then flexibility in handling different conditions is possible, but operator qualifications and manual errors affect product quality uniformity
Solution Approach 1:
The system performs automatic flatness control by computing orthogonal tension vectors and generating actuator commands without manual intervention. The automated system eliminates operator errors and qualifications as factors affecting quality uniformity, while the adaptive nature of the orthogonal decomposition maintains versatility in handling different rolling conditions.
Solution Approach 2:
The system continuously measures flatness errors, decomposes them into orthogonal components, and adjusts actuators accordingly in a closed-loop feedback manner. This automated feedback mechanism ensures consistent product quality by eliminating manual adjustment variations while adapting to changing conditions through real-time measurement and correction.
4Productivity
If rolling speed is increased to improve productivity, then output increases, but strip breakage risk increases and flatness control becomes more difficult
Solution Approach 1:
The system performs preliminary decomposition of flatness errors into orthogonal tension vectors before actuator adjustment. This pre-processing allows the control system to anticipate and correct flatness deviations proactively, enabling higher rolling speeds while maintaining reliability by preventing the development of severe flatness errors that could lead to strip breakage.
Data Source
AI summary
A method and device for measuring and adjusting the evenness and/or tension of a stainless steel strip (1) during cold rolling in a 4-roll stand (2) provided with at least one control loop (4) comprising several actuators (3), resulting in more precise measurement and adjustment due to the fact that an evenness defect (10) is determined by comparing a tension vector (8) with a predefined reference curve (9), whereupon the characteristic of the evenness defect (10) along the width of the strip is broken down into proportional tension vectors (8) in an analysis building block (11) in a mathematically approximated manner and the evenness defect proportions (C1 . . . Cx) determined by real numerical values are supplied to respectively associated control modules (12a; 12b) for actuation of the respective actuator (3).