Rotor vibration measurements using laser Doppler vibrometry: essential post-processing for resolution of radial and pitch/yaw vibrations

Background: 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 non-contact operation and inherent immunity to shaft run-out. Method of Approach: 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. Results: 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. Conclusions: The system performed well, even in the presence of noise and other typical measurement errors, and was implemented successfully in an engine vibration study.