Bending and torsion measuring system of rotary parts and it’s uncertainty analysis

In order to accurately diagnose the shafting vibration characteristics,a method based on the principle of laser Doppler frequency shift was proposed to measure the rotation shaft bending vibration,torsional vibration and shaft rotation speed at the same time. Combining with the optical heterodyne technique and the reference light technology, the Doppler heterodyne interference light path was designed for separating the twist vibration,and the mathematical model of the measurement system was constructed.Moreover, the main factors were analyzed for affecting the laser Doppler bending torsional vibration measurement, the influence of various parameters on the measuring results were discussed and the corresponding measurement uncertainty was presented . In the confidence level of 95%, the uncertainty of the instantaneous speed is 0.079 r/min,and that of the bending vibration velocity component is 0.001 4 mm/s, which can meet the requirement of the rotating shaft vibration comprehensive measurement.