Tandem Cold Rolling Thickness Control Using Entry Thickness Transfer
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Solution Overview
Problem
Existing thickness control methods in cold rolling mills face challenges such as delayed response and inaccurate control of delivery thickness due to reliance on proportional integrator modifications and preset reduction rates, which are not adaptive to changing rolling conditions.
Innovation Solution
A control system for a tandem cold rolling mill that includes entry and delivery thickness gauges and a control device, which transfers entry thickness data at the same speed as the material, calculates thickness changes, and adjusts the rolling speed of upstream stands to achieve target entry and delivery thicknesses, enhancing control response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If constant force control is executed using roll gap of the final stand, then surface roughness transfer is made uniform, but delivery thickness control accuracy deteriorates due to large lag time
Solution Approach 1:
The control system calculates a preliminary target rolling force based on the measured delivery thickness deviation before the actual rolling operation. This preliminary target value is then used to adjust the roll gap of the upstream stand, enabling proactive thickness control that compensates for the inherent lag time in the constant force control system.
Solution Approach 2:
The system implements a feedback mechanism where the actual delivery thickness is continuously measured and compared with the target thickness. The deviation information is fed back to adjust the target rolling force, creating a closed-loop control system that maintains both surface roughness uniformity and delivery thickness accuracy.
2Manufacturing precision
If modification of target value is performed by inputting delivery thickness deviation to proportional integrator, then delivery thickness control is achieved, but control response is delayed
Solution Approach 1:
Instead of waiting for the proportional integrator to process the deviation, the system preliminarily calculates the target rolling force by directly applying the deviation to a base rolling force. This preliminary target value is immediately used for control, significantly reducing the time delay associated with iterative integration processes.
3Ease of manufacture
If preset reduction rate is used to calculate target entry thickness, then calculation is simplified, but control accuracy deteriorates under changing rolling conditions
Solution Approach 1:
The system dynamically adjusts the reduction rate based on actual rolling conditions rather than using a fixed preset value. The reduction rate is modified in real-time according to the measured delivery thickness and current rolling parameters, enabling the system to adapt to changing conditions while maintaining control accuracy.
Data Source
AI summary
In thickness control processing, transfer processing of an entry thickness He(N) is performed (step S1). In the transfer processing, data of the entry thickness He(N) is transferred from a position P11 to a position P12 at the same speed as the speed of a material to be rolled M. Subsequently, an amount of change in a thickness ΔH(N) is calculated (step S2). The amount of the change in the thickness ΔH(N) is calculated based on data of a delivery thickness Hd(N) and data of a transferred thickness Hc(N) transferred to the position P12 at a timing when the data of the delivery thickness Hd(N) is measured. Then, a target entry thickness He(N)_tgt is calculated (step S3). Subsequently, a manipulated amount of rolling speed VR(N−2) and VR(N−k) are calculated (step S4).