Rolling Mill Actuator Control via Inverse Frequency Response
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Solution Overview
Problem
Existing rolling mill technologies face challenges in fully compensating for higher-frequency thickness deviations in metal strips, leading to residual thickness variations after cold rolling, due to inadequate consideration of actuator frequency responses.
Innovation Solution
The method involves a control device that determines target values for actuators in a rolling mill by accounting for the inverse frequency behavior of each actuator, using mass flow control and feedback control mechanisms to accurately compensate for thickness deviations, including filtering high-frequency fluctuations and utilizing inverse models to minimize computational effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional control methods are used without considering actuator frequency response, then the control system is simpler, but higher-frequency thickness deviations cannot be fully compensated
Solution Approach 1:
The control device determines setpoints by accounting for the inverse frequency behavior of actuators in advance, rather than reacting to thickness deviations after they occur. This preliminary compensation approach allows the system to pre-correct for the known frequency-dependent response characteristics of actuators, enabling full compensation of higher-frequency thickness variations without requiring complex real-time adjustments
Solution Approach 2:
The control device uses feedback from measured thickness deviations to continuously adjust setpoints for actuators. By combining this feedback with the inverse frequency response model, the system can predict and compensate for actuator behavior at different frequencies, improving thickness control precision while maintaining a manageable control architecture
2Manufacturing precision
If the control device compensates for higher-frequency thickness deviations by considering actuator frequency response, then manufacturing precision improves, but computational effort increases
Solution Approach 1:
The control device transforms the control problem into the frequency domain by using the inverse frequency response of actuators as a parameter. This transformation allows the system to efficiently compute compensation setpoints by applying frequency-dependent gain and phase adjustments, rather than requiring computationally intensive time-domain simulations or iterative optimization methods
Data Source
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Figure 4~5
AI summary
In a rolling mill (2), a metal strip (1) is rolled, which is fed to the rolling mill (2) by a feeding device (3). The rolled metal strip (1) is removed from the rolling mill (2) by a discharge device (4). A control unit (9) cyclically determines setpoint values (e.g. s*) for actuators (e.g. 13) based on the final thickness deviations (δd2) of sections (12) of the metal strip (1) from a target thickness (d2*) on the exit side of the metal strip (1) and outputs the determined setpoint values (e.g. s*) to the actuators (e.g. 13). The actuators (3, 4, 13, 14) comprise the feed device (3), an adjustment device (13) for the roll gap of the rolling stand (2), a drive (14) for driving rolls of the rolling stand (2) and/or the discharge device (4). For the feed device (3), the drive (14) and the discharge device (4), the setpoint (M3*, M2*, M4*, v3*, vU*, v4*) is a setpoint speed (v3*, vU*, v4*) or a setpoint torque (M3*, M2*, M4*).For the adjusting device (13), the setpoint (s*) is a roll gap setpoint (s*). The control device (9) determines at least one of the setpoints (e.g. s*) based on the number of final thickness deviations (δd2), taking into account a description of the inverse frequency response of the respective actuator (e.g. 13).