Study On Helicopter Blades Deformation Identification Using Videoly Measurment

Because of its advantages of simplicity, non-destruction, non-contacting, real-time analysis andcontrol, video measurement has been widely used in scientific research and actual engineering fields.In this thesis, the methods of measuring blade deformation by video measurement are systematicallyinvestigated. To measure3-dimensional deformations, an integrated system based on the proposedmethods is also developed.First, a circular landmarks calibration procedure is developed by using the camera imagingmodel as the theoretical basis, and combining with the Zhang Zhengyou calibration method. Thedisplacement in two-dimensional plane is measured by using a single camera, and influences of thequality of camera, methods of camera calibration and size of camera view field on the measurementaccuracy are analyzed.Second, the displacement mode, the correlation function, the method of search and sub-pixelestimation are determined according to the principles of digital image correlation method. Because ofthe weakness of the previous initial estimation for the Newton-Rapson algorithm, a new initialestimation method based on Harris corner detection and matching is proposed. The method ofinterpolation for the Newton-Rapson algorithm is optimized, and the computing speed and efficiencyof the new method for the Newton-Rapson algorithm are validated by simulated tests. The tensiledeformation and the Poisson’s ration of the aluminum are measured by the digital image correlation.Third, the calibration method for the binocular measurement system is studied. Then the3-dimensional reconstruction is conducted to obtain the spatial displacements of the feature points, bymatching the feature points in the images according to the principle of the binocular camerameasurement. According to the measuring tests results of the translational displacement and thebending of the equal-intensity beam, the measurement accuracies of the landmarks and3-dimensionaldigital image correlation method are compared.Finally, a simple binocular camera measurement system is established by analyzing the hardwareparameters required to measure the deformations of rotating blades. The torsional deformation of astatic blade and deformation of rotating fan blades are tested to verify the reliability of the system.