Detection And Track Of Markers In Wind Tunnel And Wing Deformation Measurements

The wing deformation will be inevitably induced by aerodynamic loading, and it will be more obvious if the aerodynamic loading is heavier. As the elastic deformation will seriously affect the performance evaluation of the aircraft, it is necessary to be considered in the design of the aircraft. Wind tunnel test as the only way to evaluate aerodynamic characteristics of the aircraft currently, is required to accurately measure the elastic deformation of the model wing during the aerodynamic testing to correct the test data. VMD (Videogramme trie model deformation)measurement technique is the most widely optical method for measuring aeroelastic deformation and attitude of a model during aerodynamic testing in wind tunnel. VMD technique is used to determine the spatial coordinates of markers on a model surface from the markers centroids in a series of images. From these spatial coordinates, the model deformation induced by aerodynamic loading is computed. This paper focuses on the markers and their detection and track in a VMD measurement system with two cameras, and the main contents and contributions are presented as following:First, According to the environment in a transonic wind tunnel, a ring markers is designed, and a method to detect and locate the markers is given;Second, some markers will sometimes be blown away or lost because of the model reflective in detecting process during the wind tunnel test, so a encoding method is proposed with the markers encoded according to its absolute positon in a white strips, that the matching of images acquired by two cameras comes true even there are some markers missing;Third, based on the local region of interest and the encoding information of markers, a automatic tracking method is proposed, when some markers are blocked or covered, their locations will be predicted by the other tracked markers which are in the same strips with the missing ones;Fourth, the spatial coordinates of markers on a model surface are determined from the markers centroids in a series of images. From markers’spatial coordinates, the model elastic deformation induced by aerodynamic loading is computed in real time and real-time display.Finally, the markers are used in the wing deformation measurement in a transonic wind tunnel. The success of measurement proves that detection and track of markers in wind tunnel are effective and practical.