Research On The Key Technologies Of The Aircraft Spin Parameters Measurement In The Vertical Spin Tunnel

Spin is the very dangerous flight status of aeroplane and has caused many air disasters. The free spin test in vertical wind tunnel is an important way to study spin and is very useful for spin avoid. Conventional methods to estimate the plane attitudes in spin are time consuming, inefficient and uneliable. To develop efficient system for spin test, supported by the military project'Vertical Wind Tunnel Build', this dissertation concentrates its attention on the key technologies of estimating the plane attitudes in the free spin test efficiently. With the purpose of developing the plane attitudes estimation equipment with own intellectual property rights, the dissertation studies several techniques, including the plane attitudes estimation techniques based on stereo vision, the techniques to design the manmade vision signs, the improved line detection algorithm adapted for amoeboid line segments recognition, the occlusion in stereo vision and the construction of the stereo vision equipment to estimate the plane attitudes in spin time.The main contents and contributions of this dissertation are as follow:1. Aiming at estimating the plane attitudes in spin time efficiently with advanced techniques, a method is proposed based on the stereo vision technique and a set of manmade signs. The stereo vision technique should conceive the 3D coordinates of manmade signs and from their coordinates, the spin parameters of model should been worked out. Compared with traditional ways, this method is automatic and intellectualized with advantages in better efficiency and heigher data density.2. Matching is a difficult problem for stereo vision applications. To solve the matching problem, a method though a set of manmade signs is set up. The matching way is based on the absolute distinguish and classification of manmade signs. The signs'design principle is shown such as their size, amount and distribution. Finally, some studies focus on the signs classification and orientation of the signs'center.3. In spin tests images, manmade signs are represented as irregularly line segments and are hardly distinguished with existing line detectors. To solve the problem, a new way for blurry line segment detection is presented, named rolling ball detection. In this way, a detecting window is just like a ball rolling through the line segments. The rolling ball method does a good work to detect the blurry line segments and is tolerant of segments'wide, length and even deformations. The questions, how detecting window steps over the intersection area, are also studied, so it is feasible to detect the manmade signs. The new line detector is also useful to distinguish abnormal segments for other works.4. Occlusion is another hard problem in stereo vision. The previously proposed means always count out all the occluded space. It is computationally expensive and hard to come true. In this dissertation, a new way based on the credit coefficients is presented. By the distance constraint condition, the occluded signs would be searched until the best optimal estimates are gotten. The credit coefficients are introduced into the process to improve the accuracy of positions. Effects of the assistant signs are also analyzed and to be sure that the occluded signs are searched based on the very reliable signs. The credit coefficients could whittle the affections of signs with poor definition. Simulations and experiments on real images validate our method useful and the spin figures using probability has been increased for 60% to above 80% with occlusion problem solved.5. A system used to estimate the plane attitudes in spin time in the vertical wind tunnel is built up successfully with own intellectual property rights. The fixed parameters rotary balance experiments on ground and the actual spin tests have validated the system meet all targets. In a vision field from 3m×3m to 6m×6m, the relative precisions of angles are better than 0.5% and the relative precision of spin rolling velocity is better than 0.96%.In Dec.2007, the system has passed the item identification with the comments that its performance index is better than traditional system in Russia and has come up to an international advanced level. The system has been used for several aircraft types for spin tests and has assisted to airman parachuting trainings.