DEVELOPMENT OF A FAN-SHAPED DISTANCE METER SYSTEM FOR MEASURING MOVING ROTOR BLADES – CONCEPT, PHOTOGRAMMETRIC ORIENTATION AND FIRST RESULTS
Keywords: fan-shaped distance meter system, laser spot, camera, photogrammetry, sensor fusion, relative orientation, wind turbine, rotor blade torsion
Abstract. For wind turbines, the actual deformation of the rotor blades during operation is of great interest to manufacturers. Photogrammetry and laser scanning are suitable for contactless measurement. The torsion of the rotor blade is of major interest and should be determined with an accuracy of less than 1°. This requires a high precision in the recording distance. The combination of photogrammetry and laser scanning thus enables the acquisition of the relevant data. The nacelle movement is photogrammetrically measured. To measure the torsion, laser scanners in 1D mode are used. A further development of the measuring scenario is a novel fan-shaped distance meter system, presented in this contribution. It consists of four distance measuring units of a Z+F Imager 5006 laser scanner, whose laser beams span a plane in object space. The distance measuring units provide synchronous range measurements. For the calculation of 3D coordinates, their relative orientation is required. Two photogrammetric approaches are presented in this paper. In the first method, the meter system is moved relative to the testfield. The data acquisition and evaluation is complex. In the second method, a stereo camera is built onto the meter system so that 3D coordinates can be measured directly. This method allows a fast data acquisition and evaluation for system calibration. The realization on a real wind turbine is possible. This contribution discusses challenges and advantages of measuring the rotor blades during operation and presents the realisation of the novel meter system and the determination of the relative orientation. The new meter system makes it possible to measure the torsion during operation of the wind turbines without any targeting with required accuracy.