The Development Spinning Measurement System For Vertical Wind Tunnel

Theφ5 meter vertical wind tunnel is the first vertical wind tunnel in China. The spin measurement system that equipped in the wind tunnel uses advanced Videogrammetric technique. It has achieved the non-invasive and non-contact measurement. And it has achieved the measurement of six dimension spin parameters of spin model and process automatically while the model moves complexly. This paper presents the researches of the spin measurement system, including lighting, camera calibration methods, marks cover in and identify, attitude parameters'calculate and so on, and following is the details.1. Because the use of 60 fps high-speed camera, the normal lighting method will bring the bad frequency flicker effect. In this system, using the three-phase supply and combined light lamp can successfully avoid the frequency flicker.2. The camera calibration basing on moving planar pattern is demarcated, which the pixel error is smaller than 0.1 pixels.3. After the set of several sets marks which has a certain redundance, it has been successful to avoid cannot calculating the model attitude parameters when some marks cover in.4. In order to avoid losing marks, adaptive threshold method is used. The difference of relative position between model and camera can bring more contrast at image gray. If we use just one threshold, some mark will be lost.5. This is done with a gray-scale centroid arithmetic to sub-pixel resolution after subtracting background. The error of mark location is smaller than 0.1 pixels.6. Different model attitude parameters arithmetics are designed for different situations when marks occur simultaneously. Judging the mark occur simultaneously is based on identified marks. Selecting the best arithmetic is based on condition of the mark occur simultaneously. Then the model attitude parameters can be calculated.7. The detail of debug process, test results, and application of this system is introduced. After static and dynamic debugging, all technical characteristics conform to the requirements of design guideline. It has been successfully used in wind tunnel.