Rolling Stand Eccentricity Compensation for Strip Thickness Control
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Solution Overview
Problem
Conventional thickness control systems in rolling stands fail to effectively compensate for periodic deviations in strip thickness caused by roll eccentricities and out-of-roundness, particularly when there are deviations between the operating and drive sides, leading to disturbances in rolling force and material tension.
Innovation Solution
A control method that compensates for both symmetrical and asymmetrical eccentricities by using a control device that determines target values for adjusting devices based on symmetrical and asymmetrical measured variables, with separate processing for each type of eccentricity, and employs observers and plant models to refine these values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional thickness control systems are used, then the system is simple to operate, but periodic deviations in strip thickness caused by roll eccentricities cannot be compensated
Solution Approach 1:
The control system is segmented into two independent subsystems: one for compensating symmetrical eccentricities and another for asymmetrical eccentricities. Each subsystem processes specific measured variables (symmetrical or asymmetrical) separately, allowing complex eccentricity compensation to be divided into manageable, specialized control paths that can be implemented without overwhelming system complexity
Solution Approach 2:
Measured variables act as intermediaries between the physical eccentricity conditions and the control responses. The system introduces symmetrical and asymmetrical measured variables that mediate the information flow from the rolling process to the control device, enabling precise differentiation and compensation of different eccentricity types without requiring direct physical modification of the rolling stand
2Manufacturing precision
If separate procedures are used for operating side and drive side eccentricity compensation, then compensation accuracy improves, but compatibility with existing symmetrical compensation systems is lost
Solution Approach 1:
The control device merges symmetrical and asymmetrical compensation procedures into a single integrated control architecture. Both compensation types are processed simultaneously within the same control device using a unified mathematical model that combines symmetrical and asymmetrical measured variables, achieving high compensation accuracy while maintaining compatibility with existing symmetrical compensation systems
Solution Approach 2:
The control device is designed with universal functionality to handle both symmetrical and asymmetrical eccentricities through a single integrated system. The control device can process different types of measured variables and apply appropriate compensation strategies, making it adaptable to various rolling conditions and compatible with existing control systems while providing enhanced compensation capabilities
3Reliability
If roll eccentricities are not compensated, then the control system remains simple, but periodic disturbances in rolling force and material tension occur
Solution Approach 1:
The system implements feedback control by continuously measuring symmetrical and asymmetrical variables during the rolling process and using these measurements to adjust the roll gap in real-time. The control device receives feedback from the measuring devices and automatically modifies the adjusting devices to compensate for detected eccentricities, stabilizing rolling force and tension without requiring complex mechanical modifications
Solution Approach 2:
The system replaces complex mechanical solutions for eccentricity compensation with a control-based approach. Instead of using mechanical means to physically correct roll positioning, the system uses measuring devices to detect eccentricities and control algorithms to calculate compensatory adjustments, substituting mechanical complexity with intelligent control that achieves the same stabilization effect
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
In a rolling stand (1), a flat metal stock is rolled at a rolling speed. A control device of the rolling stand (1) receives a symmetrical target roll gap (s*). The control device receives measured variables (MOS, MDS) determined by measuring devices (6 to 8) and dependent on a symmetrical eccentricity occurring during rolling of the stock in the rolling stand (1) and an asymmetrical eccentricity occurring during rolling of the stock in the rolling stand (1).The control device determines respective setpoints for an operator-side and a drive-side adjustment device of the roll stand (1), by means of which the roll gap is adjusted on the drive side and operator side of the roll stand (1), taking into account the target roll gap (s*), an implicitly or explicitly specified target roll gap wedge (k*), a symmetrical compensation value (δs), and an asymmetrical compensation value (δk), and controls the adjustment devices accordingly. The control device determines the symmetrical compensation value (δs) using the symmetrical measured variable (MS) and the asymmetrical compensation value (δk) using the asymmetrical measured variable (MA).When determining the target values for the adjusting devices, the control device takes into account the target roll gap (s*) and the symmetrical compensation value (δs) with the same sign and the target roll gap wedge (k*) and the asymmetrical compensation value (δk) with the opposite sign.