Virtual Channels for Eddy Current Array Probe Coverage Loss
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Solution Overview
Problem
Eddy current array inspection systems face signal amplitude variation due to limited channel coverage, known as 'coverage loss,' which reduces sensitivity to defects not directly under the center point of sensors, particularly for defects oriented parallel to the direction of motion.
Innovation Solution
The introduction of virtual channels, calculated based on the properties of physical channels, using vector interpolation of EC signals from adjacent channels, with calibration defects located mid-way between physical channels, to compensate for coverage loss and enhance probe sensitivity and defect imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If physical channels are used for EC array inspection, then the system structure is simple and easy to implement, but coverage loss occurs and signal amplitude varies for defects located between sensor centers
Solution Approach 1:
The patent introduces virtual channels as intermediary elements between physical sensor channels. These virtual channels are calculated based on signals from adjacent physical channels and serve as mediators to capture defect signals that would otherwise be missed due to the discrete nature of physical sensors, thereby reducing coverage loss and improving signal amplitude consistency.
Solution Approach 2:
The patent creates virtual channel copies by interpolating signals from physical channels. The virtual channels are mathematical representations that replicate the sensing capability of physical channels at intermediate positions, allowing the system to detect defects located between physical sensor centers without adding physical sensors.
2Measurement precision
If sensors are placed closer together to reduce coverage loss, then the detection sensitivity improves, but the device complexity and cost increase
Solution Approach 1:
Instead of adding more physical sensors to improve detection sensitivity, the patent creates virtual sensor copies through signal interpolation. The virtual channels provide additional detection points at intermediate positions without requiring additional physical sensors, maintaining detection sensitivity while avoiding increased device complexity.
Solution Approach 2:
The patent replaces the mechanical approach of adding more physical sensors with a signal processing approach. By using mathematical interpolation to generate virtual channel signals, the system achieves improved detection sensitivity without the mechanical complexity of denser sensor arrays.
3Measurement precision
If virtual channels are introduced to reduce coverage loss, then measurement precision improves, but signal processing complexity increases
Solution Approach 1:
The patent performs preliminary signal processing by pre-calculating virtual channel signals from physical channel measurements. The virtual channels are generated in advance through interpolation algorithms, allowing the system to compensate for coverage loss before defect detection and analysis, thereby improving coverage uniformity with manageable processing complexity.
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
The use of virtual channels improves probe sensitivity and defect imaging by effectively interpolating signals from defects located between physical channels, reducing coverage loss and providing improved resolution and sensitivity.
Implementation Method 1
Some of the coils are configured as driver coils, creating a variable magnetic field in a test object
Implementation Method 2
other coils are configured as sensing coils which detect magnetic fields generated by eddy currents in the test object
Implementation Method 3
magnetic fields generated by eddy currents in the test object
Data Source
AI summary
Disclosed is an apparatus and method for generating virtual inspection channels mid-way between the physical inspection channels of an eddy current array probe, thereby reducing the coverage loss and improving defect sizing and imaging. The method is based upon a calibration to determine the mid-channel coverage loss for parallel defects having their long axis parallel to the scanning direction. Based on the coverage loss measurement, a vector analysis system is constructed enabling generation of virtual channel signals which are available for processing in the same way as physical channels, with impedance plane representation including real and/or imaginary signal components. The system differentiates between parallel and perpendicular defects and employs different algorithms to generate virtual channel signals for parallel and perpendicular defect orientations.