Roll Train Control With Frequency-Filtered Stand Distribution

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Solution Overview

Problem

In metal rolling processes, maintaining the contour and flatness of metal strips across multiple rolling stands is challenging due to the limitations of existing closed-loop control systems, which struggle to adjust the contour quickly and accurately, especially in large roll trains, leading to flatness errors in interstand regions.

Innovation Solution

The implementation of an operating method for a roll train that uses frequency filtering to determine provisional manipulated variables for upstream rolling stands, shifting rapid contour changes to rear stands and slower changes to front stands, allowing for highly dynamic control while minimizing flatness errors in interstand regions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the contour is adjusted in rear rolling stands to achieve rapid response, then the dynamics of control is improved, but flatness errors propagate to interstand regions

Engineering Contradiction:

Improvecontrol response speedVSAvoidflatness precision

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The control system performs preliminary action by calculating provisional manipulated variables for upstream rolling stands based on frequency-filtered characteristic variables before the actual rolling process. This allows the system to pre-compensate for contour changes and prevent flatness errors in interstand regions while maintaining rapid response capability in rear stands

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The closed-loop control system uses feedback from the characteristic variable (measured contour deviation) to continuously adjust the manipulated variables for each rolling stand. The frequency filtering of this feedback signal enables the system to respond rapidly to contour errors while distributing the control action to prevent flatness errors

Inventive Principle:

Principle #23Feedback

2Manufacturing precision

If the roll train has many upstream rolling stands to distribute the control action, then the flatness precision is improved, but the device complexity increases

Engineering Contradiction:

Improveflatness precisionVSAvoidcontrol system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The control system replaces complex mechanical coordination between multiple rolling stands with a signal processing approach. By using frequency filtering and mathematical transformation of the characteristic variable, the system simplifies the control architecture while still distributing control actions across multiple stands to maintain flatness precision

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11623258B2Frequency-dependent distribution of manipulated variables for changing the rolling stock cross section in a roll train

Publication Date: 2023.04.11 PRIMETALS TECH GERMANY GMBH

AI summary

Rolling stock (2) composed of metal is rolled in rolling stands (3a to 3f) of a roll train (1) under the control of a control device. The control device, on the basis of a variable (δQ) (which is characteristic of the change in the cross section with which the rolling stock (2) is supposed to run out of a rolling stand (3e) of the roll train (1)), first determines all provisional manipulated variables (Sb to Se) for the rolling stand (3e) and rolling stands (3b to 3d) located upstream of the rolling stand (3e), and uses said provisional manipulated variables to determine final manipulated variables (Sb′ to Se′), which influence the cross section with which the rolling stock (2) runs out of the respective rolling stand (3b to 3e). The control device determines the provisional manipulated variables (Sb to Sd) for the upstream rolling stands (3b to 3d) by frequency filtering.