Remote self-powered structure monitor

• US 6,014,896 A
• Filed: 02/02/1999
• Issued: 01/18/2000
• Est. Priority Date: 08/31/1994
• Status: Expired due to Fees

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Schoess, Jeffrey N.
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US09/241,452
• Time in Patent Office: 350 Days
• Field of Search: 73/587, 73/801, 73/583, 73/802, 340/665, 340/870.16, 364/508, 310/328
• US Class Current: 73/583
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence
• CPC Class Codes: G01H 11/08 using piezoelectric devices
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0066 by exciting or detecting vibration or acceleration vibration testing of structures G01M7/00
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/0289 Internal structure, e.g. defects, grain size, texture
• CPC Class Codes: G01N 2291/101 one transducer
• CPC Class Codes: G01N 2291/2693 Rotor or turbine parts
• 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 29/42 by frequency filtering or by tuning to resonant frequency
• CPC Class Codes: G01N 29/46 by spectral analysis, e.g. Fourier analysis or wavelet analysis spectral signal processing per se G06F17/14

Abstract

An acoustic rotor monitor that is an autonomous self-powered measurement instrument which can detect embedded and hidden fatigue cracks in remotely inaccessible devices such as helicopter rotor system components. A predictive maintenance-related problem for rotor craft is the detection of fatigue cracks as a continuous real-time monitoring process under dynamic rotor system loading conditions. The rotor monitor focuses on the embedding an acoustic emission-based smart sensor directly into the rotor system to measure the high frequency stress waves indicating that a structural crack has propagated as a "self-powered" measurement without reducing structural integrity.

Claims

1. A remote metal rotating structure monitor, comprising:

an acoustic emission energy PVDF piezoelectric transducer mounted on a metal rotating structure to be monitored for detecting a condition of said metal rotating structure using non repetitive high frequency acoustic emission events of 1 to 10 MHz, stress wave acoustic emission energy and to generate self-contained electrical power from vibrations by said metal rotating structure;

a signal conditioner connected to said transducer to receive stress wave acoustic emission energy therefrom and identify a signal indicative of crack propagation on said metal rotating structure;

a power controller connected to said transducer to selectively use power from said transducer as a secondary power supply source;

a power storage device connected to said power controller and said signal controller to receive and discharge power as determined by said power controller, said power storage device being positioned on said sensor to provide an inertial load; and

a radio frequency telemetry circuit connected to said signal conditioner and said power storage device to transmit data from said signal conditioner identifying crack propagation and transmit power to said power storage device; and

an antenna system connected to said telemetry circuit and said power controller to transmit said data and transmit said power;

wherein said transducer outputs the electrical power signals due to compression, stretching and/or bending of the sensor caused by the vibration of the structure and enhanced by said inertial load.

2. The monitor of claim 1, which further includes a signal processor connected to said piezo acoustic emission transducer for receiving the electrical signals from said emission sensor.

3. The monitor of claim 2, wherein said piezo acoustic emission sensor is formed from a plurality of piezo-electric layers and a plurality of elastomeric layers situated between the plurality of piezo-electric layers, wherein said sensor outputs the electrical power signals due to compression, stretching and/or bending of the plurality of piezo-electric layers, caused by vibration of the structure.

4. The monitor of claim 3, wherein said piezo acoustic emission sensor wherein the piezo-electric and elastomeric layers are stacked on one another alternately in that one elastomeric layer is situated between adjacent piezo-electric layers.

5. The monitor of claim 4, wherein said piezo electric transducer is flexible and conformable to the structure being monitored.

6. The monitor of claim 1, wherein a single piezo acoustic emission sensor is used per structural member.