Metrology

Abstract

The measurement of structure dynamics is a common technique to characterise the dynamic behaviour of structures, analysing reasons of disturbing vibrations, design optimization and as comparison data to check and improve simulation results. Depending on the measurement task, different measurement devices are used such as laser vibrometers and accelerometers. A recent approach is to perform modal analyses using a trackinginterferometer. Firstly the fundamentals of vibration measurement and modal analysis with tracking-interferometers are discussed. Due to the adaption of the measurement device from geometry measurement to vibration measurement several issues have to be considered. Two of them are focused in this paper. The first discussed issue is the influence of the connection of the targets and nests to the vibrating structure. Moreover, for an automation of modelling of the machine it is necessary to measure the absolute distance between tracking-interferometer and the target mounted at the structure. Due to the fact that the used LaserTRACER does not have an absolute distance measurement unit, alternative methods to acquire the absolute distance information out of the signals of the available position sensitive diode are presented.