Granted Patent B2

US 12,571,701 · App. 18/437,773 · Granted Mar 10, 2026

Inventors: Weidong Zhu (Ellicott City, MD); Linfeng Lyu (Halethorpe, MD)

Assignee: University of Maryland, Baltimore County

G01M7/025F03D17/00G01H9/00

Abstract

Claims (56)

1 . A system comprising:

a laser vibrometer that produces a laser beam;

a camera configured to capture an image of a rotating structure; and

a scanner electrically coupled to a controller, wherein the scanner includes a first mirror and a second mirror positioned orthogonally relative to the first mirror;

wherein the laser beam is reflected by the first mirror and the second mirror to the rotating structure; and

wherein the scanner is controlled by the controller based on a position of the rotating structure in the image detected by the camera to move the laser beam along a path on the rotating structure; and wherein the path is two-dimensional; and

wherein the laser vibrometer is configured to:

measure a response of the rotating structure;

determine a Fast Fourier Transform (FFT) of the response;

apply a bandpass filter to the response with a passband that includes a damped natural frequency of the rotating structure to create a filtered response;

determine a time interval between a minimum value and a maximum value of the filtered response;

multiply the filtered response in the time interval by sinusoidal signals to create a plurality of processed responses; and

apply a lowpass filter to the plurality of processed responses to obtain an end-to-end undamped mode shape of the rotating structure.

2 . The system of claim 1 , further comprising a tripod, wherein the laser vibrometer, the scanner, and the camera are mounted on the tripod.

3 . The system of claim 1 , wherein the camera includes a frame rate of at least 25 frames per second.

4 . The system of claim 1 , further including a reference mark positioned on the rotating structure, wherein the position of the rotating structure is determined by the reference mark in the captured image of the camera.

5 . The system of claim 1 , further comprising the rotating structure, wherein the rotating structure is a wind turbine blade.

6 . A method comprising:

measuring a response of a rotating structure subject to random excitation with a tracking continuous scanning laser vibrometer system;

determining a Fast Fourier Transform (FFT) of the response;

applying a bandpass filter to the response with a passband that includes a damped natural frequency of the rotating structure to create a filtered response;

determining a time interval between a minimum value and a maximum value of the filtered response;

multiplying the filtered response in the time interval by sinusoidal signals to create a plurality of processed responses; and

applying a lowpass filter to the plurality of processed responses to obtain an end-to-end undamped mode shape of the rotating structure.

7 . The method of claim 6 , wherein the sinusoidal signals include cos(ω d,i t) and sin(ω d,i t), where ω d,i is the damped natural frequency of the rotating structure.

8 . The method of claim 6 , wherein the rotating structure is rotating at a non-constant speed.

9 . The method of claim 6 , wherein the rotating structure is rotating at a constant speed.

10 . The method of claim 6 , wherein the time interval is measured by the tracking continuous scanning laser vibrometer system from a first end of a scan path to a second end.

11 . The method of claim 6 , further including determining end-to-end undamped mode shapes of the structure.

12 . A method comprising:

measuring a response of a structure subject to an arbitrary excitation with a tracking continuous scanning laser vibrometer system;

interpolate positions of the response on a grid to generate a plurality of interpolated positions;

rectifying the plurality of interpolated positions to create a plurality of rectified interpolated positions;

identifying a plurality of zero-crossings from the plurality of rectified interpolated positions;

determine a portion of the plurality of zero-crossings with a time increment; and

interpolate and lift measurements at the portion of the plurality of zero-crossings.

13 . The method of claim 12 , wherein the structure is rotating.

14 . The method of claim 13 , wherein the method includes capturing images of the rotating structure.

15 . The method of claim 13 , wherein the rotating structure is a wind turbine blade.

16 . The method of claim 12 , wherein rectifying the plurality of interpolated positions includes determining negative absolute values of differences between the plurality of interpolated positions and a position of a virtual measurement point on a scan path.

17 . The method of claim 12 , wherein the time increment is equal to the inverse of a scan frequency.

18 . The method of claim 12 , further including determining a damped natural frequency, a damping ratio, and/or an undamped mode shape of the rotating structure.

19 . A system comprising:

a laser vibrometer that produces a laser beam;

a camera configured to capture an image of a rotating structure; and

a scanner electrically coupled to a controller, wherein the scanner includes a first mirror and a second mirror positioned orthogonally relative to the first mirror;

wherein the laser beam is reflected by the first mirror and the second mirror to the rotating structure; and

wherein the scanner is controlled by the controller based on a position of the rotating structure in the image detected by the camera to move the laser beam along a path on the rotating structure; and wherein the path is two-dimensional; and wherein the laser vibrometer is configured to:

measure a response of the rotating structure;

interpolate positions of the response on a grid to generate a plurality of interpolated positions;

rectify the plurality of interpolated positions to create a plurality of rectified interpolated positions;

identify a plurality of zero-crossings from the plurality of rectified interpolated positions;

determine a portion of the plurality of zero-crossings with a time increment; and

interpolate and lift measurements at the portion of the plurality of zero-crossings.

20 . The system of claim 19 , further comprising a tripod, wherein the laser vibrometer, the scanner, and the camera are mounted on the tripod; wherein the camera includes a frame rate of at least 25 frames per second.

21 . The system of claim 19 , further including a reference mark positioned on the rotating structure, wherein the position of the rotating structure is determined by the reference mark in the captured image of the camera.

Assignments (1)

Continuity (3)

References Cited (64)