Design And Implementation Of Measurement System For Wind Tunnel Spin Attitude Under Full Field Of View Based On Stereo Vision

Spin is an abnormal flight state of aircraft, complex and dangerous. It can easily cause flight accident. Vertical wind tunnel test is the main technique to study the phenomenon of spin. At present China's own vertical wind tunnel has been put into use, however, the traditional attitude measurement method still exists disadvantages of poor measurement accuracy and incomplete data curve, and it also can`t be suitable for all kinds of aircrafts. It can`t meet the require of aerodynamics research. Therefore, the study of new spin attitude measurement system in wind tunnel has important theoretical and engineering application value.According to the problems of traditional measurement method, the full field of view spin measurement system based on stereo vision is designed. The key technologies of marker recognition, three-dimensional reconstruction and attitude solution are studied. It develops a set of spin attitude measurement system suitable for different kinds of aircrafts. The main research is as follows:(1) The scheme for full field of view measurement system based on two sets of binocular stereo vision systems is proposed. Due to the difficulty of image recognition and matching of binocular stereo vision in complex background, the method that 8 bit coded markers are as the feature points is proposed. To get more completed and effective test data, two sets of binocular stereo vision system are used based on the test site conditions. The complementary field is formed, and it solves the problem of marker blocking, poor measurement perspective and camera blind field. Test data integrity is improved.(2) Attitude solution requires three-dimensional data of feature points. Three-dimensional coordinates of coded markers in wind tunnel are measured by binocular stereo vision system. Large field calibration based on mobile board of binocular stereo vision system is achieved. The test shows that the calibration accuracy get better with the increase of number of images when images are less than 10 pairs, the calibration results stabilize when images are more than 11 pairs, and the three-dimensional reconstruction error is calculated.(3) Due to the difficulty of measuring complex shape of the aircraft objects, a new method which is nothing to do with the shape is proposed. The coded markers can be attached to arbitrary position of model surface. Transferring relationship of coordinates is created by three markers between body axis coordinate system and wind axis coordinate system. The axis vector of body axis coordinate system is converted to the wind axis coordinate system, and attitude parameter is calculated.The measurement system is realized. The test shows that measurement accuracy is better than 1°, and the image utilization rate reaches 95%. Accuracy and effectiveness meet the design requirement, and are greatly improved compared with traditional method. The system is successfully put into use in wind tunnel test and achieves all kinds of spin test.