Tracking continuously scanning laser doppler vibrometer systems and methods

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.

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.

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.