Measuring Structure Deformations of a Composite Glider by Optical Means with on-Ground and in-Flight Testing

Kurzfassung

In aeronautical research experimental data sets of high quality are essential to verify and improve simulation algorithms. For this reason the experimental techniques need to be constantly refined. The shape, movement or deformation of structural aircraft elements can be measured implicitly in multiple ways; however, only optical, correlation-based techniques are able to deliver direct high-order and spatial results. In this paper two different optical approaches are used for on-ground preparation and the actual execution of in-flight wing deformation measurements on a PW-6U glider. First, the commercial PONTOS system is used for static tests on the ground and for wind tunnel investigations to successfully certify an experimental sensor pod mounted on top of the test bed fuselage. Secondly, a modification of the glider is necessary to implement the optical method named Image Pattern Correlation Technique (IPCT), which has been developed by the German Aerospace Center DLR. This scientific technology uses a stereoscopic camera set-up placed inside the experimental pod and a stochastic dot matrix applied to the area of interest on the glider wing to measure its in-flight deformation. The flight test installation, including its preparation, is described here and results are presented briefly. Focussing on the compensation for typical error sources, the paper concludes with a recommended procedure to enhance the data processing for better results. Within this project IPCT has been developed and optimized for a new type of test bed. Adapted to the special requirements of the glider, the IPCT measurements were able to deliver a valuable wing deformation data base which now can be used to improve corresponding numerical models and simulations. The presented activities were carried out within the collaborative research project “Advanced In-Flight Measurement Techniques 2” (contract No. 266107) funded by the European Commission under the Seventh Framework Programme for Research.