Vibration Measurements of Rotating Objects Using an Optomechatronical Image Derotator

The need of investigations on rotating objects during operation is constantly increasing. Therefore, obtaining detailed information about the dynamic system behavior (such as vibrations) is essential. Vibrations are described as periodic, deforming mechanical oscillations of a structural component. In general, measurements of vibration amplitudes and frequencies are performed using a laser Doppler vibrometer on a non-rotating measurement object. In order to quantify vibrations of the object during operation, a laser Doppler vibrometer can be used in combination with an optomechatronical image derotator. Thus, the laser beam is tracked to the rotating object continuously. In this presentation, the conventional measurements at standstill are compared with the extended measurements on rotating objects by using the derotator to prove the enormous potential of this measuring system. This comparison demonstrates the need of the derotator by measuring, investigating and interpreting the characteristic eigenmodes of a blade wheel and a blisk using a laser Doppler vibrometer.