Method and apparatus for reducing crosstalk in a structural health monitoring system

• US 20070175279A1
• Filed: 11/10/2005
• Published: 08/02/2007
• Est. Priority Date: 11/10/2005
• Status: Active Grant

• Current Assignee: Acellent Technologies, Inc.
• Original Assignee: Acellent Technologies, Inc.
• Inventors: Qing, Xinlin, Beard, Shawn
• Granted Patent: US 7,596,078 B2
• Time in Patent Office: Days
• US Class Current: 73/584
• CPC Class Codes: G01N 2203/0073 Fatigue
• CPC Class Codes: G01N 2291/0258 Structural degradation, e.g. fatigue of composites, ageing of oils
• CPC Class Codes: G01N 2291/105 two or more emitters, two or more receivers
• CPC Class Codes: G01N 2291/106 one or more transducer arrays
• CPC Class Codes: G01N 29/32 Arrangements for suppressing undesired influences, e.g. temperature or pressure variations , compensating for signal noise
• CPC Class Codes: G01N 29/36 Detecting the response signal , e.g. electronic circuits specially adapted therefor

Abstract

Methods and apparatus for reducing crosstalk in a structural health monitoring system. A pair of actuator input signals are sent to an actuator, each resulting in the transmission of stress waves to a corresponding sensor. The sensor then converts these stress waves to a pair of output signals, each having a crosstalk portion due to electromagnetic interference from the input signals to the actuator, and a stress wave portion corresponding to the stress waves. Various methods of varying the actuator input signals, the input to the actuator, and the output of the sensor result in two output signals that can be combined so as to reduce the crosstalk portions and isolate the stress wave portions. This allows actuators and sensors to be placed sufficiently close together that the stress wave portions of sensor output signals can overlap their crosstalk, without corrupting or otherwise compromising the data contained therein.

Claims

1. A method of monitoring the health of a structure according to stress waves transmitted from an actuator to a sensor through the structure, comprising:

initiating the transmission of first and second actuation signals to the actuator so as to facilitate the generation of first and second stress waves within the structure;

receiving first and second sensor signals from the sensor, the sensor signals each having a crosstalk portion corresponding to an electromagnetic interference from the respective actuation signal, and a stress wave portion corresponding to the respective stress wave; and

combining the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

2. The method of claim 1 wherein:

the initiating further comprises initiating the transmission of the second actuation signal, the second actuation signal being approximately identical to the first actuation signal;

the receiving further comprises inverting an output of the sensor so as to receive the second sensor signal, the stress wave portion of the second sensor signal being approximately inverse to the stress wave portion of the first sensor signal and the crosstalk portion of the second sensor signal being approximately identical to the crosstalk portion of the first sensor signal; and

the combining further comprises subtracting the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

3. The method of claim 1 wherein:

the initiating further comprises initiating the transmission of the second actuation signal, the second actuation signal being approximately inverse to the first actuation signal;

the receiving further comprises inverting an output of the sensor so as to receive the second sensor signal, the crosstalk portion of the second sensor signal being approximately inverse to the crosstalk portion of the first sensor signal and the stress wave portion of the second sensor signal being approximately identical to the stress wave portion of the first sensor signal; and

the combining further comprises adding the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

4. The method of claim 1 wherein:

the initiating further comprises, after initiating the transmission of the first actuation signal, inverting an output of the actuator and subsequently initiating the transmission of the second actuation signal, the second actuation signal being approximately identical to the first actuation signal;

the receiving further comprises receiving the second sensor signal, the stress wave portion of the second sensor signal being approximately inverse to the stress wave portion of the first sensor signal and the crosstalk portion of the second sensor signal being approximately identical to the crosstalk portion of the first sensor signal; and

the combining further comprises subtracting the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

5. The method of claim 1 wherein:

the initiating further comprises, after initiating the transmission of the first actuation signal, inverting an output of the actuator and subsequently initiating the transmission of the second actuation signal, the second actuation signal being approximately inverse to the first actuation signal;

the receiving further comprises receiving the second sensor signal, the crosstalk portion of the second sensor signal being approximately inverse to the crosstalk portion of the first sensor signal and the stress wave portion of the second sensor signal being approximately identical to the stress wave portion of the first sensor signal; and

the combining further comprises adding the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

6. A computer readable medium having computer executable instructions thereon for a method of monitoring the health of a structure according to stress waves transmitted from an actuator to a sensor through the structure, the method comprising:

initiating the transmission of first and second actuation signals to the actuator so as to facilitate the generation of first and second stress waves within the structure;

receiving first and second sensor signals from the sensor, the sensor signals each having a crosstalk portion corresponding to an electromagnetic interference from the respective actuation signal, and a stress wave portion corresponding to the respective stress wave; and

combining the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

7. The computer readable medium of claim 6 wherein:

the initiating further comprises initiating the transmission of the second actuation signal, the second actuation signal being approximately identical to the first actuation signal;

the receiving further comprises inverting an output of the sensor so as to receive the second sensor signal, the stress wave portion of the second sensor signal being approximately inverse to the stress wave portion of the first sensor signal and the crosstalk portion of the second sensor signal being approximately identical to the crosstalk portion of the first sensor signal; and

the combining further comprises subtracting the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

8. The computer readable medium of claim 6 wherein:

the initiating further comprises initiating the transmission of the second actuation signal, the second actuation signal being approximately inverse to the first actuation signal;

the receiving further comprises inverting an output of the sensor so as to receive the second sensor signal, the crosstalk portion of the second sensor signal being approximately inverse to the crosstalk portion of the first sensor signal and the stress wave portion of the second sensor signal being approximately identical to the stress wave portion of the first sensor signal; and

the combining further comprises adding the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

9. The computer readable medium of claim 6 wherein:

the initiating further comprises, after initiating the transmission of the first actuation signal, inverting an output of the actuator and subsequently initiating the transmission of the second actuation signal, the second actuation signal being approximately identical to the first actuation signal;

the receiving further comprises receiving the second sensor signal, the stress wave portion of the second sensor signal being approximately inverse to the stress wave portion of the first sensor signal and the crosstalk portion of the second sensor signal being approximately identical to the crosstalk portion of the first sensor signal; and

the combining further comprises subtracting the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

10. The computer readable medium of claim 6 wherein:

the initiating further comprises, after initiating the transmission of the first actuation signal, inverting an output of the actuator and subsequently initiating the transmission of the second actuation signal, the second actuation signal being approximately inverse to the first actuation signal;

the receiving further comprises receiving the second sensor signal, the crosstalk portion of the second sensor signal being approximately inverse to the crosstalk portion of the first sensor signal and the stress wave portion of the second sensor signal being approximately identical to the stress wave portion of the first sensor signal; and

the combining further comprises adding the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

11. A system for monitoring the health of a structure, comprising:

an actuator configured to generate a stress wave from an actuation signal;

a sensor configured to receive the stress wave and to generate a sensor signal having a first portion corresponding to an electromagnetic interference from the actuation signal, and a second portion corresponding to the stress wave; and

a processor in communication with the actuator and the sensor;

wherein the actuator and the sensor are configured for placement upon a structure at a distance apart from each other, the distance corresponding to the second portion of the sensor signal overlapping the first portion; and

wherein the processor is configured to isolate the second portion of the sensor signal from the overlapping first portion.

12. The system of claim 11 wherein the processor is further configured to:

initiate the transmission of first and second actuation signals to the actuator so as to facilitate the generation of first and second stress waves within the structure;

receive first and second sensor signals from the sensor, the sensor signals each having a crosstalk portion corresponding to an electromagnetic interference from the respective actuation signal, and a stress wave portion corresponding to the respective stress wave; and

combine the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

13. The system of claim 12 wherein the processor is further configured to:

initiate the transmission of the second actuation signal, the second actuation signal being approximately identical to the first actuation signal;

invert an output of the sensor so as to receive the second sensor signal, the crosstalk portion of the second sensor signal being approximately identical to the crosstalk portion of the first sensor signal; and

subtract the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

14. The system of claim 12 wherein the processor is further configured to:

initiate the transmission of the second actuation signal, the second actuation signal being approximately inverse to the first actuation signal;

invert an output of the sensor so as to receive the second sensor signal, the second sensor signal having a crosstalk portion approximately inverse to the crosstalk portion of the first sensor signal; and

add the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

15. The system of claim 12 wherein the processor is further configured to:

after initiating the transmission of the first actuation signal, invert an output of the actuator so as to transmit the second actuation signal, the second actuation signal being approximately identical to the first actuation signal;

receive the second sensor signal from the sensor, the crosstalk portion of the second sensor signal being approximately identical to the crosstalk portion of the first sensor signal; and

subtract the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.

16. The system of claim 12 wherein the processor is further configured to:

after initiating the transmission of the first actuation signal, invert an output of the actuator and subsequently transmit the second actuation signal, the second actuation signal being approximately inverse to the first actuation signal;

invert an output of the sensor so as to receive the second sensor signal, the crosstalk portion of the second sensor signal being approximately inverse to the crosstalk portion of the first sensor signal; and

add the first and second sensor signals so as to isolate the stress wave portions from the crosstalk portions.