In the laboratory, the true-to-scale model situation of the view of a wind turbine was built, which corresponded to the real requirements in angles and dynamics. It served in particular as a test setup for the implementation of the tracking and SNK control algorithms. The resulting prototype of the measurement system was demonstrated at CeBIT 2014.
The further development for measurements on real WTGs required two steps: first the adaptation of the tracking method to field conditions, then the adaptation of tracking and vibrometry to the dynamics of large WTGs. In the first step, a model setup in the outdoor area of the Fraunhofer IOSB offered all the challenges for image processing that arise from changing light and background situations during the detection of rotor motion. As a second step, measurements on large turbines in the wind farm provided the prerequisites for extending the tracking method to include geometric degrees of freedom such as the pre-tensioning of the rotor blades against the wind pressure or counter-rotating bending vibrations that lead to deviations in the intermediate blade angles. Vibrometry was further developed on the basis of wind farm measurements for the macro-Doppler shifts, which bring about the high absolute speeds that large rotor blades exhibit at the same angular speeds compared to the model wind turbine.
Within the scope of the project WEADYN (running time 09.2015 to 11.2018), which is funded by the BMWi, these developments made it possible for the first time to measure vibrations on rotor blades of large wind turbines during operation by means of laser Doppler vibrometry. In addition, vibration data of stationary plant components were obtained, which were also used e.g. in a comparative study with seismic measurements of the KIT.