Structural monitoring system for helicopter rotor components

• US 6,693,548 B2
• Filed: 08/08/2001
• Issued: 02/17/2004
• Est. Priority Date: 08/08/2001
• Status: Active Grant

• Current Assignee: Sikorsky Aircraft Corporation (Martin Marietta Corporation)
• Original Assignee: Sikorsky Aircraft Corporation (Martin Marietta Corporation)
• Inventors: Hawman, Michael W., Boyce, William C.
• Primary Examiner(s): Wu, Daniel J.
• Assistant Examiner(s): Nguyen, Tai T.
• Application Number:
  US09/924,909
• Publication Number:
  US 20030030564A1
• Time in Patent Office: 923 Days
• Field of Search: 340/657, 340/665, 340/870.16, 340/653, 340/661, 340/672, 736/60, 735/93, 736/49, 736/58, 735/87
• US Class Current: 340/657
• CPC Class Codes: B64C 27/007 adapted for detection of blade cracks
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00
• CPC Class Codes: G01N 29/227 related to high pressure, tension or stress conditions

Abstract

A system for monitoring the structural condition of a helicopter rotor assembly component includes a piezoelectric sensor. Acoustic emission signal techniques allow for recognizing the relatively high frequency stress waves associated with the propagation of cracks or defects in a rotor assembly component. A signal conditioner processes the sensor signal and provides an output signal that includes at least one characteristic that is indicative of the content of the sensor signal and, therefore, the structural condition of the item of interest. A signal analyzer utilizes the output signal from the signal processor to determine the structural condition of the component.

Claims

1. A system for determining a structural condition of a portion of a helicopter rotor assembly, comprising:

a piezoelectric sensor that is adapted to be supported on a portion of the rotor assembly and that provides a sensor signal indicative of stress waves in the portion of the rotor assembly;

a signal processor that processes the sensor signal and provides an output signal having at least one characteristic that is indicative of the content of the sensor signal, the signal processor including a demodulator portion that demodulates the sensor signal to thereby generate an envelope representation of the sensor signal; and

a signal analyzer that receives the envelope representation output signal and determines the structural condition based upon the output signal characteristic.

2. The system of claim 1, wherein the signal analyzer utilizes an amplitude characteristic of the output signal.

3. The system of claim 1, wherein signal analyzer utilizes a time characteristic of the output signal.

4. The system of claim 1, wherein the output signal characteristic is indicative of a rise time of the sensor signal and wherein the signal analyzer utilizes the rise time information as an indicator of the structural condition.

5. The system of claim 1, wherein the signal processor includes a filter element that filters out sensor signal components outside of a chosen frequency range.

6. The system of claim 5, wherein the filter element filters out signal components that are below 100 KHz.

7. The system of claim 1, including a wire connection between the signal processor and the signal analyzer.

8. The system of claim 1, including a transmitter that transmits the output signal and a remotely located receiver associated with the signal analyzer that receives the transmitted output signal.

9. The system of claim 1, including a slip ring interface that communicates the output signal from the signal processor to the signal analyzer.

10. A method of determining a structural condition of a portion of a helicopter rotor assembly, comprising the steps of:

(A) attaching a piezoelectric sensor to a portion of the rotor assembly;

(B) detecting stress waves in the portion using the sensor;

(C) generating a stress signal indicative of the detected stress waves;

(D) demodulating the stress signal to generate an output signal that is an envelope representation of the stress signal and has at least one characteristic indicative of the content of the stress signal;

(E) determining the structural condition of the portion based upon the output signal characteristic.

11. The method of claim 10, including using at least one of the group of characteristics consisting of amplitude, time, energy, spectral content, pulse width and frequency as the characteristic of the output signal while performing step (E).

12. The method of claim 10, including using a rise time characteristic of the output signal while performing step (E).

13. The method of claim 10, wherein the output signal characteristic is indicative of a rise time of the stress signal and including using the rise time characteristic while performing step (E).

14. The method of claim 10, wherein step (D) includes removing selected frequency components prior to performing step (E).