Force-Limited Lateral Guides for Metal Strip Position Control
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Solution Overview
Problem
Existing rolling train systems face challenges in maintaining the straightness and central guidance of metal strips during the threading phase, leading to asymmetrical deformations, lateral migration, and potential damage due to uncontrolled lateral movement, which results in flatness errors and increased risk of the strip missing or doubling in the roll gap of downstream stands.
Innovation Solution
Implementing a force-limited adjustment method for lateral guides, where the position controller determines commands based on the time derivative of the strip's deviation from the target position, allowing the guides to yield and reduce the risk of band doublers, ensuring the strip runs straight by counteracting changes in deviation with finely dosed counter-control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If strong lateral guides are used to firmly hold the metal strip, then the strip position control is improved, but the risk of band doublers and damage to strip edges increases
Solution Approach 1:
The lateral guides are designed with force-limited adjustment capability, allowing them to dynamically adapt their holding force. The guides can yield when excessive force is detected, preventing band doublers and strip damage, while still maintaining adequate position control during normal operation. This dynamic behavior resolves the contradiction between firm holding and damage prevention.
Solution Approach 2:
The system changes the force parameter of the lateral guides from a fixed strong holding force to a variable force-limited adjustment. By controlling the guides with a maximum force limit, the system maintains sufficient position control while preventing excessive forces that cause band doublers and edge damage.
2Manufacturing precision
If lateral guides are operated with position control to limit lateral migration, then the strip guidance is improved, but the lateral guides may damage the strip edges due to one-sided grinding
Solution Approach 1:
The control parameter for lateral guides is changed from pure position control to force-limited adjustment. This allows the guides to maintain adequate position control while limiting the force they can exert on the strip, thereby preventing edge damage from one-sided grinding during lateral migration events.
3Object-affected harmful factors
If the metal strip is allowed to move laterally freely, then the risk of band doublers is reduced, but the strip exits the roll stand with poor straightness
Solution Approach 1:
The system implements force-limited adjustment as an intermediate parameter between complete freedom and rigid position control. This allows sufficient lateral movement to prevent band doublers while maintaining enough guidance through the force-limited guides to ensure the strip exits with good straightness.
Solution Approach 2:
The lateral guides provide dynamic, force-limited guidance that adapts to the strip's movement needs. This dynamic control allows the strip to move when necessary to avoid band doublers while maintaining straightness through controlled guidance forces.
4Manufacturing precision
If strong forces are applied by lateral guides to correct strip position, then the strip position control is improved, but the lateral guides and roughing stand may be damaged
Solution Approach 1:
The force parameter of lateral guides is limited to a maximum value that prevents damage to the guides and roll stand while maintaining sufficient position control capability. This force limitation resolves the contradiction between effective position control and component durability.
Solution Approach 2:
The force-limited adjustment acts as a protective measure beforehand, preventing excessive forces from being applied to the lateral guides and roll stand. This cushioning effect protects the components from damage while still allowing effective position control within safe force limits.
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A metal strip (1) comprising a strip head (7) is rolled on a rolling mill. The rolling mill comprises at least one front roll stand (2a) and one rear roll stand (2b) arranged downstream of the front roll stand (2a). Between the two roll stands (2a, 2b), the rolling mill further comprises lateral guides (8, 8') for the metal strip (1). The lateral guides (8, 8') are operated with force limitation. During the period between the exiting of the strip head (7) from the front roll stand (2a) and the entry of the strip head (7) into the rear roll stand (2b), an amount of deviation (δy) of the lateral position (y) of the strip head (7) from a setpoint position (y*) is measured by means of the lateral guides (8, 8'). A control command (S) for the front roll stand (2a) is worked out by a strip position controller (13). The front roll stand (2a) of the strip position controller (13) is controlled on the basis of the control command (S). The strip position controller (13) works out the control command (S) using the time derivative of the deviation (δy) of the lateral position (y) of the strip head (7) from the setpoint position (y*) in such a way as to counteract a change in the deviation (δy) of the lateral position (y) of the strip head (7) from the setpoint position (y*).