Probe Signal Decimation With Adaptive Filter Clocking
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Solution Overview
Problem
Existing nondestructive material testing methods face challenges in reliably and easily implementing material testing at variable relative speeds between the test object and probe, as they require relative-speed-dependent filter sets and face issues with adapting cut-off frequencies during operation.
Innovation Solution
The method involves detecting and digitizing probe signals with a constant word repetition rate, using n-stage decimation to reduce the word repetition rate, and dynamically adapting the digital filter's clock frequency to the instantaneous signal frequency, allowing for unchanged filter coefficients and automatic adjustment of cut-off frequencies based on relative speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If relative-speed-dependent filter sets are used for probe signal processing, then material testing can be performed at variable relative speeds, but device complexity increases due to additional filter sets and switching mechanisms
Solution Approach 1:
The patent changes the parameter of word repetition rate dynamically based on instantaneous relative speed. By adjusting the sampling rate to match the signal frequency at different speeds, the system maintains optimal filtering performance without requiring multiple fixed filter sets. This parameter adaptation allows a single digital filter to handle variable speed conditions effectively.
Solution Approach 2:
The digital filter is designed to serve multiple functions across different operating conditions. By making the word repetition rate adaptive, the same filter structure can process signals at various relative speeds, eliminating the need for speed-specific filter sets and reducing overall system complexity while maintaining versatility.
2Measurement precision
If filter cut-off frequencies are adapted during operation by reloading coefficients, then filtering performance is optimized for current speed, but transient effects and stability issues occur
Solution Approach 1:
The system prepares multiple sets of filter coefficients in advance, corresponding to different word repetition rates. Based on the instantaneous relative speed, the appropriate coefficient set is selected before it is needed, avoiding any reloading during operation. This preliminary preparation ensures continuous stable operation without transient effects.
Solution Approach 2:
The system dynamically switches between pre-prepared filter coefficient sets based on changing relative speed conditions. This dynamic adaptation allows the filter to maintain optimal performance across varying speeds without the instability associated with reloading coefficients during operation, as the switching occurs between complete, pre-validated coefficient sets.
3Measurement precision
If high word repetition rates are maintained for accurate signal representation, then signal fidelity is preserved, but processing efficiency decreases and filter implementation becomes more difficult
Solution Approach 1:
The word repetition rate is made dynamic rather than fixed at a high constant value. The sampling rate adapts to the signal frequency corresponding to the instantaneous relative speed, using the minimum necessary rate to accurately represent the signal. This dynamic adjustment maintains signal fidelity while improving processing efficiency by avoiding unnecessarily high sampling rates.
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 enables reliable and easily implementable material testing at variable relative speeds without the need for relative-speed-dependent filter sets, ensuring stable and efficient signal processing across changing speeds.
Implementation Method 1
The eddy currents thereby induced in the test object in turn induce in a probe, for example in the form of a coil or coil arrangement, a periodic electrical signal
Implementation Method 2
The eddy currents thereby induced in the test object
Data Source
AI summary
A method for testing the material of a test object (8) in a nondestructive manner, said test object being moved relative to a probe (1) at a variable relative speed, comprises the following steps: detecting a probe signal (US) by means of the probe (1), subjecting the probe signal (US) to analog-to-digital conversion in order to generate a digitized probe signal (USD) in the form of a sequence of digital words with a predefined, in particular constant, word repetition rate, n-stage decimation of the word repetition rate of the digitized probe signal (USD) or of a digital demodulation signal (UM) derived from the digitized probe signal by means of n cascaded decimation stages (5_1 to 5_n), where n≧2, selecting an output signal (UA_1 to UA_n) of one of the n decimation stages (5_1 to 5_n) depending on the instantaneous relative speed and filtering the selected output signal by means of a digital filter (7), which is clocked with the word repetition rate of the selected output signal.