Method And Implementation Of Binocular Measurement For Model Deformation In Intermittent High-Speed Wind Tunnel

During the wind tunnel test,the test model is subjected to aerodynamic loading,and it will inevitably undergo elastic deformation.Some of these deformations will make the aerodynamic characteristics of the test target seriously deviate from the original intention of the aircraft designer,resulting in a decrease in the range and bearing capacity of the aircraft.In order to accurately design the aerodynamic shape of the aircraft,the actual aerodynamic performance of the aircraft can be estimated accurately at the design stage.It is necessary to accurately measure the elastic deformation of the experimental model during the wind tunnel test,and the aerodynamic correction of the test data is carried out based on it.Due to the need of large aircraft design and development,this test technology has become one of the most urgent wind tunnel test technologies in China.The high-speed wind tunnel in China is mostly intermittent.Compared with the continuous high-speed wind tunnel in foreign countries,there is a large vibration noise during tests,so it is not suitable for the model deformation measurement technology which is existing in the foreign wind tunnel.For this reason,this paper aims at the model deformation measurement technology of intermittent high-speed wind tunnel and carries out the following research work on the model deformation binocular measurement method under the vibration environment.Firstly,in the view of the deformation measurement of the environment of intermittent high-speed wind tunnel,a model deformation measurement binocular method is proposed in the process of considering the pose vibration of the cameras.In the process of method,the disturbance of the camera attitude is solved in real time,and the high precision positioning of the circular marking point on the model surface is realized.Compared with the existing model deformation measurement method in the continues wind tunnel which is based on binocular stereo vision,the proposed method takes into account the relative pose disturbance between two cameras,the position and pose disturbance of camera coordinates relative to wind tunnel,and the model coordinate relative to the wind tunnel.So it can effectively compensate the 3D positioning error of the model mark point caused by the interference of vibration noise during the blowing process of intermittent high-speed wind tunnel.Secondly,in order to solve the problem of the perturbation of the camera in the world coordinate system in the proposed measurement method,a 4-point camera relative attitude solution method based on the plane constraint of unknow background point is proposed.Compared with the existing homography decomposition methods,the proposed method is concisely and has less computational steps,fastest speed and the highest accuracy.Thirdly,in order to solve the relative pose between two cameras in the proposed measurement method,a multi constraint algorithm about camera relative attitude is proposed.Compared with the traditional 5-point algorithm,the proposed method considers the motion constraints of the rigid body.Therefore,there are non-exist multiple solutions and scale problems in the process of solving the camera attitude and position.Then,in order to solve the problems of center location and 3D reconstruction of the model mark in wind tunnel,a calculation method is proposed to calculate the position of the center projection point based on the projective contour parameters.The method first solves the projection homography matrix,and then calculates the location of the center projection point and the direction of the circle.Compared with the existing method,the proposed method only needs two parallel circles in any position to determine the correct projection point,which is more flexible.Then the method of determining the correct position of a single model traget point under the disturbance of cameras in intermittent high-speed wind tunnel is proposed.Finally,a prototype system of model deformable measurement is set up in the full-span test section of the 2.4m intermittent tansonic wind tunnel.The measurement results of the system are compared with the Stereo Pattern Tracking(SPT)system in the continuous transonic wind tunnel ETW.The experimental results show that the data consistency of the two wind tunnels is very good,which confirms the correctness of our method.