Research On Three-Dimensional Topography Measurement Technology Of Engine Blade Based On Grating Projection

As the power source of aircraft,engine performance plays a vital role in aircraft.Blade is an important part of aeroengine,and its quality directly determines the performance of the engine.At present,many methods for measuring the three-dimensional topography of blades have been proposed by researchers at home and abroad,but these methods still can not meet the requirements of high accuracy,high speed and low cost at the same time.Therefore,it is of great significance to study how to achieve high accuracy,high efficiency and low cost three-dimensional topography measurement of engine blades.Firstly,a three-dimensional topography measurement system of engine blades based on grating projection is designed.The hardware and software requirements of the blade measurement system are analyzed.The optical technology in grating projection measurement is introduced.The measuring optical path is analyzed and the measuring form in the experiment is determined.On this basis,the hardware selection and software design are completed.It lays a foundation for subsequent measurement system calibration,image acquisition and processing.Secondly,the calibration method of the topography measurement system is studied.The traditional Zhang Zhengyou calibration method is analyzed in this paper,which is widely used.Aiming at the problem of dynamic change of calibration parameters,a calibration method considering the change of parameters is proposed.Two methods are used to calibrate the measuring system,and the length of the line is measured by calibration parameters,and accuracy of the two calibration methods is compared.An accurate correspondence isestablished between the point information of physical surface and the point information of stripe image,which lays a foundation in improving the accuracy of blade three-dimensional topography measurement.Thirdly,the generation and processing technology of fringe image is studied in the process of topography measurement.The standard sinusoidal grating fringes are generated by computer software.The phase demodulation and phase unwrapping of grating fringes are performed by four-step phase-shifting method and time-phase unwrapping method respectively.The traditional phase unwrapping algorithm of differential frequency is improved,and the phase unwrapping accuracy before and after the improvement is compared and analyzed.By extracting more accurate phase information,the accuracy of blade three-dimensional topography measurement is improved significantly.Finally,a grating projection three-dimensional topography measurement platform is built to measure the three-dimensional profile of engine blades,and the errors that affect the measurement of blade profile in the experiment are analyzed.The wrapped phase of the measured blade is obtained by phase demodulation of the deformed fringes collected by four-step phase-shifting method.The absolute phase of the measured blade is obtained by improved phase unwrapping method.Finally,three-dimensional point cloud reconstruction of engine blades is realized.