Rolling Mill Thickness Measurement Using Eddy Current Resistivity Compensation
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Solution Overview
Problem
Conventional pulsed eddy current measurement technologies are not sufficiently accurate for thin metal plates, leading to noisy measurements and limited applicability below a certain thickness limit, which affects the quality and control of rolled products in rolling mills.
Innovation Solution
A method that acquires a data signal reflecting the time dependence of eddy current decay caused by a pulsed magnetic field, determines a thickness parameter value based on the ratio between the work item's thickness and resistivity, and computes an instantaneous resistivity value to improve thickness measurement accuracy, using a control unit to generate an output signal indicative of the present thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pulsed eddy current measurement technology is used, then thickness measurements can be obtained, but measurement accuracy deteriorates for thin metal plates leading to noisy measurements
Solution Approach 1:
The patent changes the measurement parameter from direct thickness extraction to extraction of a thickness parameter that reflects the ratio between thickness and resistivity. By measuring eddy current decay characteristics and deriving a parameter proportional to thickness/resistivity ratio, the method achieves improved accuracy for thin plates where conventional direct measurement fails due to noise.
2Adaptability or versatility
If conventional methods are used for thin plates, then measurements can be performed, but applicability is limited below a lower thickness limit
Solution Approach 1:
The patent transforms the measurement approach by deriving a parameter that reflects the thickness-to-resistivity ratio from eddy current decay characteristics. This parameter transformation enables accurate measurement of thin plates below the conventional lower thickness limit, expanding the applicability range while maintaining precision through the ratio-based measurement principle.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy of thickness measurements for thin work items, enabling better control of rolled products, increased production speed, and improved final product quality by eliminating the need for uncertain resistivity values and using empirical models to relate eddy current decay to thickness and resistivity ratios.
Implementation Method 1
conventional pulsed eddy current measurement technology is based on measuring eddy currents induced in the metal plate by a rapidly varying magnetic field applied to the metal plate
Implementation Method 2
measuring eddy currents induced in the metal plate by a rapidly varying magnetic field applied to the metal plate
Data Source
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AI summary
The present invention relates to determining a present thickness of a work item while being processed in a rolling mill (100), the method comprising: acquiring (S102) a data signal reflecting a time dependence of an eddy current decay in the work item caused by an applied pulsed magnetic field, determining (S104) a thickness parameter value based on the acquired signal, the thickness parameter value being determined from samples in the data signal, the thickness parameter value being dependent on a ratio between a thickness of the work item and a resistivity of the work item, computing (S106) a ratio between a reference thickness value of the work item and the thickness parameter value to thereby provide an instantaneous resistivity value, determining (S108) a mean resistivity value based on the instantaneous resistivity value, and providing (S110) an output signal based on the mean resistivity of the work item and the thickness parameter value, the output signal being indicative of the determined present thickness of the work item.