Measurement of radial expansion and tumbling motion of a high-speed rotor using an optical sensor system

In order to investigate the load capacity and the strength properties of high-speed rotors, dynamic deformation and vibration measurements are of importance, in particular at lightweight composite devices which cannot be simulated reliably. This is a challenging task in metrology since non-contact inspection techniques are required which offer micron uncertainties and high temporal resolution simultaneously, also under vacuum conditions. In order to meet these requirements, a non-incremental laser Doppler distance sensor system was developed using fiber and diffractive optics. In this paper we present for the first time high-speed deformation measurements of a cylindrical steel rotor using this novel sensor system. The radial rotor expansion of only some microns was determined despite the presence of an unsteady tumbling motion of the rotor, which was measured simultaneously. Future prospects are discussed including the possibility to measure non-metallic devices such as fiber-reinforced composites.