Method and apparatus for structural integrity monitoring

A method of monitoring and identifying icing on and fatigue to a structure comprising the steps of:

• a) acquiring and storing at least one of time and frequency domain signatures of known failure modes of said structure;
• and
• b) forming a database of patterns which are correlated to icing conditions, wherein said step of forming employs pattern recognition software, said software being employed to perform the steps of:
• i) generating features;
• ii) analyzing histograms;
• and
• iii) classifying signals,
• so as to enable a processor to make icing and fatigue measurements on said structure by correlating at least one of said time and frequency domain signatures of said known failure modes with at least one of time and frequency domain signals obtained from said structure.

An apparatus for monitoring and identifying disturbances to a structure comprising:

• a) first processing means for processing signals so as to monitor and identify disturbances to said structure;
• b) a plurality of switch means each separately controlled by said first processing means for gating a voltage signal;
• c) a plurality of actuation means each coupled to one of said plurality of switch means for applying a physical impulse to said structure upon receiving a voltage signal gated by the switch means to which it is coupled, each of said plurality of actuation means having a pair of electromagnetic coils separated by a gap and configured such that an application of said voltage signal causes said gap to change, thereby applying said physical impulse to said structure;
• d) a plurality of sensor means attached to various portions of said structure, search for detecting the effects of said physical impulse on said structure and outputting an analog signal, said effects of said physical impulse indicative of disturbances of said structure;
• e) second processing means for converting any one of said analog signals into a corresponding digital signal;
• f) multiplexer means for selectively applying any of said analog signals to said second processing means;
• and
• g) means for providing any one of said digital signals to said first processing means so as to monitor and identify disturbances to said structure.

A method of monitoring and identifying faults and physical disturbance to a structure comprising the steps of:

• a) mechanically exciting said structure so as to induce vibration of said structure;
• b) transducing said vibration so as to produce a first analog signal corresponding to said vibration;
• c) deriving a baseline vibration signal from said first analog signal, said baseline vibration signal representing a baseline or normal response of said structure;
• d) monitoring said structure by transducing said physical disturbances so as to produce a second analog signal corresponding to said faults and physical disturbances;
• e) deriving another vibration signal from second analog signal, said another vibration signal representing a response of said structure due to said faults and physical disturbances;
• f) obtaining a first plurality of features from said baseline vibration signal, said feature being influenced by the nature of said structure;
• g) obtaining a second plurality of features from said another vibration signal, said features being influenced by the nature of said structure;
• and
• h) analyzing said first plurality and said second plurality of features so as to monitor and identify the nature and extent of said faults and physical disturbances, wherein said step of analyzing is performed in a pattern space of a plurality of known features which are known to be indicative of specific disturbances and faults.

An apparatus for monitoring and detecting faults in a structure comprising:

• a) a continuity sensor comprising a first low resistance layer, said first low resistance layer being in the form of at least one elongated low resistance path having a first electrode and having first and second ends;
• and
• b) a dynamic strain sensor adapted for attachment to a surface of said structure and having:
• i) a first piezoelectric layer;
• and
• ii) said first low resistance layer, said first
• electrode being attached to one side of said piezoelectric layer and electrically insulated from said structure, wherein an opposite side of said piezoelectric layer is adapted for attachment to said structure which forms a second low resistance layer, and continuity faults are detected by monitoring electrical resistance between said first and second ends, and strains are detected by monitoring said first low resistance layer and said second low resistance layer for electrical signals, wherein a capacitance value of said dynamic strain sensor is determined by a dielectric constant of said piezoelectric layer, a distance separating said first electrode from said second low resistance contact, and a surface area of said first electrode attached to said piezoelectric layer, and wherein the measured electrical resistance, strain, and capacitance vary in accordance with the nature and extent of the faults in the structure to be monitored and detected.

An apparatus for monitoring and detecting faults in a structure comprising:

• a) a continuity sensor comprising a first low resistance layer, said first low resistance layer being in the form of at least one elongated low resistance path having a first electrode and having first and second ends;
• and
• b) a dynamic strain sensor adapted for attachment to a surface of said structure and having:
• i) a piezoelectric layer attached to said first low resistance layer;
• and
• ii) a second low resistance layer attached to an opposite side of said piezoelectric layer and adapted for attachment to said structure,
• wherein continuity faults are detected by monitoring electrical resistance between said first and second ends, strains and detected by monitoring said first low resistance layer and said second resistance layer for electrical signals, and a capacitance value of said dynamic strain sensor is determined by a dielectric constant of said piezoelectric layer, a distance separating said first electrode from said second low resistance contact, and surface area of said first electrode attached to said piezoelectric layer, and wherein the measured electrical resistance, strain, and capacitance vary in accordance with the nature and extent of the faults in the structure to be monitored and detected.

An apparatus for monitoring strains in a structure comprising:

• a) a piezoelectric layer which produces electrical signals in response to application of a dynamic force to said layer;
• and
• b) a first low resistance layer attached on one side to a first side of said piezoelectric layer, and adapted for attachment to said structure on another side;
• c) a second low resistance layer attached to a second side of said piezoelectric layer;
• and
• d) means for monitoring said first and second low resistance layers for electrical signals so as to determine the existence and extent of strains experienced by said structure.

An apparatus for monitoring strains in a structure comprising:

• a) a piezoelectric layer which produces electrical signals in response to application of a dynamic force to said layer;
• and
• b) a first low resistance layer attached on one side to a first side of said piezoelectric layer, and adapted for attachment to said structure on another side;
• c) a second low resistance layer attached to a second side of said piezoelectric layer;
• and
• d) means for detecting a capacitance value of said piezoelectric layer by determining the capacitance between said first and second low resistance layers so as to determine the existence and extent of strains experienced by said structure.

An apparatus for monitoring and identifying disturbances to a structure comprising:

• a) first processing means for processing signals so as to monitor and identify disturbances to said structure;
• b) switch means controlled by said first processing means for gating a voltage signal;
• c) actuation means for applying a physical excitation to said structure upon receiving said voltage signal gated by said switch means, wherein the application of said physical excitation to said structure by said actuation means results in said structure experiencing an initial force of magnitude "F" in a first direction followed by a plurality of reactive forces in a direction opposite said first direction and having a total magnitude of "F" wherein said plurality of forces are applied to said structure at positions away from where said force of magnitude "F" was applied;
• d) sensor means for detecting the effects of said physical excitation on said structure and outputting an analog signal, said effects of said physical excitation indicative of said disturbances on said structure;
• e) second processing means for converting said analog signal into a digital signal;
• and
• f) means for providing said digital signal to said first processing means so as to monitor and identify disturbances to said structure.