Active temperature compensation technique for structural health monitoring sensors

A structural health monitoring system comprising:

• a structure having a surface;
• first and second piezoelectric transducers arranged on the surface in a first pitch-catch configuration;
• third and fourth piezoelectric transducers arranged on the surface in a second pitch-catch configuration;
• a voltage source configured to generate a first voltage signal representing an uncompensated waveform having a first amplitude;
• voltage biasing circuitry configured to convert the first voltage signal to digital voltage amplitude samples;
• an adaptive filter configured to adaptively filter the digital voltage amplitude samples and output a second voltage signal representing a second waveform having a second amplitude different than the first amplitude;
• a first comparator connected to receive reference and test voltage signals from the second and fourth piezoelectric transducers respectively and configured to output a difference voltage signal representing differences between the reference and test voltage signals;
• and
• an analog-to-digital converter connected to receive the reference voltage signal from the second piezoelectric transducer and configured to convert the reference voltage signal to digital reference voltage amplitude samples, wherein:
• the adaptive filter is further connected to receive the digital reference voltage amplitude samples from the analog-to-digital converter and further configured to output the second voltage signal representing the compensated waveform in dependence on the digital reference voltage amplitude samples received from the analog-to-digital converter;
• the first and third piezoelectric transducers are connected to receive the second voltage signal from the adaptive filter and respectively configured to generate reference and test guided waves in first and second portions of the structure in response to receipt of the second voltage signal;
• the second piezoelectric transducer is configured to sense a first one of the reference and test guided waves and output the reference voltage signal having a characteristic dependent on the first one of the reference and test guide waves;
• and
• the fourth piezoelectric transducer is configured to sense a second one of the reference and test guided waves and output the test voltage signal having a characteristic dependent on the second one of the reference and test guided waves.

A method for detecting an anomaly in a structure, the method comprising:

• (a) sending a first voltage signal having a first amplitude to a reference piezoelectric actuator which is acoustically coupled to generate a guided wave in a structure in response to receipt of the first voltage signal;
• (b) receiving a reference voltage signal from a reference piezoelectric receiver which is acoustically coupled to detect the guided wave generated by the reference piezoelectric actuator in response to sending the first voltage signal;
• (c) determining a second amplitude which is optimized to compensate for nonlinear behavior of the reference piezoelectric actuator and reference piezoelectric receiver based on the reference voltage signal;
• (d) concurrently sending a second voltage signal having the second amplitude to the reference piezoelectric actuator and to a test piezoelectric actuator which is acoustically coupled to generate a guided wave in the structure in response to receipt of the second voltage signal;
• (e) concurrently receiving reference and test voltage signals from reference and test piezoelectric receivers in response to sending the second voltage signal;
• (f) outputting a difference voltage signal representing differences between the reference and test voltage signals received in response to sending the second voltage signal;
• and
• (g) recording data representing the difference voltage signal in a non-transitory tangible computer-readable storage medium,
• wherein steps (a) through (d) are performed by an adaptive filter.