US 6,006,163 A · Active damage interrogation method for structural health monitoring

Abstract

An active damage interrogation (ADI) system (and method) which utilizes an array of piezoelectric transducers attached to or embedded within the structure for both actuation and sensing. The ADI system actively interrogates the structure through broadband excitation of the transducers. The transducer (sensor) signals are digitized and the transfer function of each actuator/sensor pair is computed. The ADI system compares the computed transfer function magnitude and phase spectrum for each actuator/sensor pair to a baseline transfer function for that actuator/sensor pair which is computed by averaging several sets of data obtained with the structure in an undamaged state. The difference between the current transfer function and the baseline transfer function for each actuator/sensor pair is normalized by the standard deviation associated with that baseline transfer function. The transfer function deviation for each actuator/sensor pair is then represented in terms of the number of standard deviations, or sigmas, from the baseline. This statistic, termed the TF Delta, is then processed by a windowed local averaging function in order to reduce minor variations due to random noise, etc. The Windowed TF Delta for each actuator/sensor pair is then integrated over the entire excitation frequency spectrum, to thereby produce the Cumulative Average Delta, which provides a single metric for assessing the magnitude of change (deviation from baseline) of that particular actuator/sensor transfer function. The Cumulative Average Delta (CAD) for each actuator/sensor transfer function provides key, first-level information which is required for detecting, localizing, and quantitatively assessing damage to the structure.

Claims45

Dependent claims

A method for monitoring the structural health of a structure having a plurality of transducers, including a plurality of pairs of actuators and sensors, secured thereto, comprising the steps of:

exciting the actuators with broadband excitation across a prescribed frequency range, wherein each of the sensors produces an analog sensor signal in response to the excitation of the actuators;
digitizing the analog sensor signals to thereby produce digitized sensor signals;
computing a transfer function for each actuator/sensor pair using the digitized sensor signals;
comparing the magnitude of each computed transfer function with a baseline transfer function for the corresponding actuator/sensor pair;
and,
deriving a composite damage indication value for the structural health of the structure at the location of each actuator from the determined differences between the computed and baseline transfer functions for each actuator/sensor pair.

3 more elements

A system for monitoring the structural health of a structure having a plurality of transducers, including a plurality of pairs of actuators and sensors, secured thereto, comprising:

a first section which excites the actuators with broadband excitation across a prescribed frequency range, wherein each of the sensors produces an analog sensor signal in response to the excitation of the actuators;
a second section which digitizes the analog sensor signals to thereby produce digitized sensor signals;
and,
a third section which computes a transfer function for each actuator/sensor pair using the digitized sensor signals, which compares the magnitude of each computed transfer function with a baseline transfer function for the corresponding actuator/sensor pair, which determines the difference between the computed and baseline transfer functions for each actuator/sensor pair, and which derives a composite damage indication value for the structural health of the structure at the location of each actuator from the determined differences between the computed and baseline transfer functions for each actuator/sensor pair.

1 more element

Dependencies are inferred from the claim text.

Active damage interrogation method for structural health monitoring

Life of this patent

Active damage interrogation method for structural health monitoring

Life of this patent

Abstract

Claims45