Measuring structure deformations of a composite glider by optical means with on-ground and in-flight testing

Abstract

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 metrologies are used for on-ground preparation and the actual execution of in-flight wing deformation measurements on a PW-6U glider. Firstly, 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 the deformation of the upper wing surface in-flight. The flight test installation, including the preparation, is described 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 the presented 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.

In-flight investigations of the unsteady behaviour of the boundary layer with infrared thermography

“…The deformation field was captured by digital optical scanner. The details of measurement procedure and results may be found in [24]. The authors of this paper based error estimation on aforementioned results.…”

An Error Estimation System for Close-Range Photogrammetric Systems and Algorithms

“…Photogrammetric measurements in the aerospace industry, including flight tests [ 17 , 19 , 20 , 21 ], can be described separately. Such measurements are performed under specific conditions: a small tilt angle between the optical axis and the observation plane, a high level of vibration, and difficult conditions such as strong natural illumination.…”

Editorial for the special feature on Advanced In-flight Measurement Techniques AIM2

“…In the work presented, the optical measurement techniques are continuously developed throughout the project. These techniques include the structural shape and deformation measurement method IPCT ('image pattern correlation technique') [5,7,10], the flow field measurement techniques PIV ('particle image velocimetry') [3], IRT ('infrared thermography') [8] and LIDAR ('light detection and ranging') [1], as well as the method of 'interferometric laser imaging for droplet sizing' (ILIDS) [2] and pressure and strain sensors based on optical fibre sensor technology [9]. Therefore we hope you will enjoy reading these papers and would encourage you to directly contact the authors of the papers and the editors for your feedback and to get information about the latest developments.It has been our pleasure to be part of the outstanding AIM 2 project and finally be the Guest Editors of this special issue.…”