Roll Stand Flatness Control with Constrained Actuator Optimization
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Solution Overview
Problem
Current flatness control methods for metal strips in rolling processes are prone to errors due to manual efficiency determination, lack of independent control over actuators, and slow reaction times, leading to increased wear and tear and quality losses.
Innovation Solution
An operating method for a roll stand that implements a first optimizer to determine current correction variables by minimizing the deviation between actual and target flatness values, considering linear constraints and secondary conditions, and a flatness controller to adjust manipulated variables for actuators, enabling online optimization and real-time control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If manual efficiency determination is used for flatness control, then the control system is simple to implement, but the measurement precision and reliability of flatness control deteriorates due to errors
Solution Approach 1:
The patent replaces manual efficiency determination with an automated optimization algorithm that calculates actuator effectiveness matrices through singular value decomposition. This substitution eliminates human error in manual measurements while providing precise, repeatable results for flatness control parameters.
Solution Approach 2:
The system implements a feedback mechanism where the measured flatness values are continuously compared with target values, and the optimization algorithm adjusts the manipulated variables based on this feedback. This closed-loop control improves measurement precision by automatically correcting deviations and validating measurements against actual performance.
2Device complexity
If actuators are controlled without independent optimization, then the control system is simpler, but the manufacturing precision of flatness control deteriorates due to increased wear and tear
Solution Approach 1:
The patent segments the flatness control problem by independently optimizing each actuator's manipulated variables through separate optimization calculations. The effectiveness matrix is decomposed into individual actuator contributions, allowing each actuator to be controlled independently based on its specific effectiveness, thereby reducing wear and improving precision without requiring overly complex coupled control.
Solution Approach 2:
The system dynamically adjusts the manipulated variables for each actuator based on real-time flatness measurements and target values. The optimization algorithm recalculates the effectiveness matrix and adjusts actuator commands continuously, enabling adaptive control that maintains precision while managing wear through optimized actuator usage patterns.
3Ease of operation
If standard regulation based on target/actual comparison is used, then the control method is simple, but the reaction time deteriorates leading to quality losses
Solution Approach 1:
The patent performs preliminary optimization calculations by pre-computing the effectiveness matrix and determining optimal manipulated variables before the rolling process completes. The system predicts the required actuator adjustments based on current flatness measurements and target values, allowing advance preparation of control commands that reduce reaction time and prevent quality losses.
4Manufacturing precision
If singular value decomposition is used to determine manipulated variables, then the control precision is improved, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical control adjustments with computational singular value decomposition. The mathematical algorithm automatically determines the optimal manipulated variables by decomposing the effectiveness matrix, providing precise control without requiring complex mechanical control mechanisms or manual calculations.
Data Source
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AI summary
According to the invention, a metal strip (1) is rolled in a roll stand. A control device (4) for the roll stand determines, by means of a working cycle (T), a number of manipulated variables (S) for evenness members (8) of the roll stand and actuates them accordingly. The control device (4) implements an optimizer (9, 9'), which provisionally sets the current correction variables (s), according to the relationship: f(s) = f0 + W • (s - s') or f(s) = f0 + W • s, determines a totality of evenness values (f), wherein f0 are initial evenness values (f0), W is an effectiveness matrix (W) and s' is a totality of the correction variables (s') determined in the preceding work cycle (T). Then, the optimizer (9, 9') minimizes the relationship by varying the current correction variables (s): ∥f(s) - f*∥ + α∥s - s0∥ + β∥s - s'∥. s0 is a totality of target values (s0) for the correction variables (s), f* the totality of the evenness target values (f*). α and β are weighting factors (α, β). When determining the current correction variables (s), the optimizer (9, 9') considers linear ancillary conditions at least of the form: C • s ≤ B, also of the form |s - s'| < c as applicable. C is a matrix, B is a vector having the ancillary conditions to be upheld by the current correction values (s) and c is a vector having the ancillary conditions to be upheld by the difference of the current correction values (s) relative to the correction values (s') of the preceding working cycle (T). The control device (4) determines the manipulated variables (S) for the evenness members (8) in consideration of the determined current correction variables (s).