Rolling Mill Thickness Measurement Using Eddy Current Decay
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Solution Overview
Problem
Conventional pulsed eddy current measurement technologies are not sufficiently accurate for determining the thickness of thin metal plates in rolling mills, often resulting in noisy measurements and limited applicability below a certain thickness limit.
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 this signal, and computes an instantaneous resistivity value using a ratio between the thickness and resistivity of the work item, allowing for improved thickness measurement accuracy by eliminating uncertain resistivity dependencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pulsed eddy current measurement technology is used, then thickness measurement is possible, but measurement accuracy deteriorates for thin metal plates due to noisy measurements
Solution Approach 1:
The patent changes the measurement parameters by using a pulsed magnetic field instead of continuous excitation, and processes the time-dependent eddy current decay signal to extract thickness information. This parameter change enables accurate measurement of thin metal plates by analyzing the temporal characteristics of eddy current decay rather than relying on steady-state measurements, thereby improving measurement accuracy while reducing noise for thin work items
Solution Approach 2:
The patent implements a feedback mechanism where the measured eddy current decay signal is processed to determine thickness, and this thickness information is fed back to control the rolling mill operation. The system uses the measured thickness to adjust rolling parameters in real-time, improving measurement reliability and enabling closed-loop control for maintaining consistent thickness in thin metal plate production
2Adaptability or versatility
If conventional thickness measurement methods are used, then measurement is possible, but applicability is limited below a certain thickness limit
Solution Approach 1:
The patent extends the applicability range by changing the measurement approach to analyze the time-dependent decay characteristics of eddy currents. This parameter change allows the system to accurately measure thin metal plates below the conventional thickness limit, expanding the versatility of the measurement system while maintaining manufacturing precision for thin work items
Solution Approach 2:
The patent adds a temporal dimension to the measurement by analyzing the time-dependent decay of eddy currents. Instead of relying solely on amplitude measurements, the system processes the temporal characteristics of the decay signal, which provides additional information that enables accurate measurement of thin plates and extends the applicable thickness range
3Measurement precision
If thickness is determined directly from thickness parameter value and uncertain resistivity, then measurement is possible, but accuracy deteriorates due to temperature-dependent resistivity variations
Solution Approach 1:
The patent eliminates resistivity uncertainty by using a feedback approach where the thickness is determined from the time-dependent eddy current decay characteristics rather than from a single measurement combined with uncertain resistivity values. The system processes the temporal decay signal to directly extract thickness information, eliminating the need to multiply by uncertain temperature-dependent resistivity values and thereby improving measurement accuracy
4Manufacturing precision
If rolling mill operation is controlled based on upstream thickness measurements, then final product quality is improved, but production speed is limited by measurement accuracy
Solution Approach 1:
The patent improves both product quality and production speed by changing the measurement parameters to use pulsed magnetic field excitation and time-dependent signal processing. This enables accurate thickness measurement of thin plates at higher speeds, allowing the rolling mill to operate faster while maintaining control quality through reliable real-time thickness feedback
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 method provides more accurate thickness measurements for thin work items, enabling better control of the rolling process, increased production speed, and improved quality of the final product.
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
AI summary
A method for determining a present thickness of a work item while being processed in a rolling mill, the method including: acquiring a data signal reflecting a time dependence of an eddy current decay in the work item caused by an applied pulsed magnetic field, determining 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 a ratio between a reference thickness value of the work item and the thickness parameter value to thereby provide an instantaneous resistivity value, determining a mean resistivity value based on the instantaneous resistivity value, and providing 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.