Roll Stand Bending Control for Stable Entry Force
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Solution Overview
Problem
Roll stands for metal rolling experience unstable bending force during the entry process of metal rolling stock, leading to potential hook formation and damage, as the existing methods take time to correct the bending force drop, causing unscheduled interruptions and potential damage to equipment.
Innovation Solution
An operating method where an additional setpoint and manipulated variable are introduced before the actual entry time to maintain a higher bending force level, ensuring the hydraulic valve is partially open, thereby reducing the drop in bending force and minimizing hook formation by adjusting the bending system's control variables during the entry period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the bending force is reduced to the base setpoint before entry, then energy consumption is minimized, but the bending force drops significantly during entry causing instability and hook formation
Solution Approach 1:
The hydraulic valve is opened in advance before the rolling stock enters the roll stand, initiating the bending force increase before entry occurs. This preliminary action ensures that the bending force has already increased when entry happens, preventing the harmful drop and hook formation while maintaining energy efficiency by only increasing force when necessary.
Solution Approach 2:
The control system anticipates the harmful bending force drop that would occur during entry and applies a counteracting action by opening the hydraulic valve beforehand. This preliminary anti-action prevents the instability and hook formation by ensuring the bending force is already at the appropriate level before entry disrupts the rolling process.
2Reliability
If the bending force is maintained at a high level during entry, then entry stability is improved, but the time required for the bending force to reach the base setpoint increases
Solution Approach 1:
The control system dynamically adjusts the bending force based on the real-time position of the rolling stock. The hydraulic valve is opened temporarily during the entry period to increase bending force, then closed once entry is complete. This dynamic adjustment maintains stability during the critical entry phase while minimizing the time the bending force remains elevated, allowing the system to return to the base setpoint quickly.
Solution Approach 2:
The hydraulic valve is activated periodically only during the entry phase rather than continuously. The control system opens the valve for a specific time window corresponding to the entry period, then closes it to allow the bending force to return to the base setpoint. This periodic action provides stability when needed while minimizing the overall time and energy associated with maintaining elevated bending force.
3Reliability
If the hydraulic valve is opened during entry, then the drop in bending force is reduced, but the complexity of the control system increases
Solution Approach 1:
The control system uses feedback from the rolling stock position detection to automatically control the hydraulic valve. When the rolling stock is detected approaching the roll stand, the system automatically opens the valve to increase bending force, then closes it after entry. This feedback-based automation reduces control system complexity by using simple position-triggered logic rather than complex manual or continuous control mechanisms.
Data Source
AI summary
In a roll stand, the working roll inserts are pressed apart by a bending system. A base set-point value (FBB*) is supplied to a bending controller to determine a resultant set-point value (FB*). An actual value (FB) of the bending force is also supplied to the bending controller to determine a base controlled variable (SB) for the bending system so that, when the bending system is actuated with (SB), (FB) is brought as close as possible to (FBB*). From a stabilisation time (t3) after an entry time (t2), the bending controller determines (FB*), additionally taking an actual rolling force (F) into consideration. During an entry time period before (t2) and ending at (t3), an additional set-point value (FBZ*) is supplied to the bending controller for determining (FB*). (FB) is thus greater than (FBB*).