Rotor Vibration Measurements Using Laser Doppler Vibrometry: Essential Post-Processing for Resolution of Radial and Pitch/Yaw Vibrations

Laser Doppler vibrometry is now a well established technique enabling noncontact vibration measurements in the most challenging of environments. Rotor vibration measurements are often highlighted as a major application of laser vibrometers due to their noncontact operation and inherent immunity to shaft runout. In such measurements, resolution of the individual axial and torsional vibration components is possible via particular arrangement of the laser beam(s). Resolution of the radial or pitch/yaw vibration components, however, can only be achieved by essential post-processing of the data from simultaneous orthogonal measurements. This paper describes the principle and rigorous examination of a novel, dedicated resolution algorithm enabling, for the first time, real-time post-processing of the outputs from standard commercial instruments. The system performed well, even in the presence of noise and other typical measurement errors, and was implemented successfully in an engine vibration study.