Research On Flapping Angle Measurement Of Helicopter Rotor Blade Based On Binocular Vision

The changes of flapping angle, swing angle and the torsion angle form the helicopter rotor blade deformation parameters.Measuring the deformation parameters of the blade when the rotor blade is rotating can determine the range of the blade and the trajectory of the blade tip, and provide an important basis for the designing of the rotor structure, the hub limit block,and the adjustment of the helicopter rotor common taper.The rotor blade deformation measurement is directly related to the helicopter safety, comfort, reliability and accuracy of the weapons system.It is a important examination items of the helicopter development,production and maintenance. In the view of the exiting measurement methods have the problem of improving the operation,automation and accuracy, This paper carried out the flapping angle measurement method of helicopter rotor blade based on the stereo vision measurement method using the coded targets method and the rotor coordinate method.The main research contents and results are as follows:(1) The helicopter rotor blade flapping angle measure system based on Binocular vision has been build.The design of hardware and software of the measurement system is carried out.The hardware system is divided into three modules, data processing,binocular vision and trigger signal control; Firstly, the selection of the PC is analyzed according to the system requirements of the date processing efficiency and the storage space size; secondly, the selection of the camera and lens is analyzed according to the system requirements of the accuracy of the binocular vision measurement system;Finally, the design of the frequency multiplier is analyzed according to the binocular vision system requirements of the trigger signal. The software system is divided into three modules,image collection, targets 3D coordinates calculation and flapping angel calculation, to analysis the functions of software. The system realize collation of the high definition binocular image of the high speed rotor blade, and construct a framework of the flapping angel measurement.(2) A target 3D information measure method based on binocular vision has been realized. Firstly, the calibration and correction of the binocular camera has been realized.Then, the principle of the annular artificial coded target has been researched.It is realized the automatic detection of the coded target with the methods ofOTSU,morphological filtering,shape factor,and ellipse fitting.And it is realized the automatic matching of the targets with the principle of the equal of the target value.Finally, according to the target matching results it is realized the measure of the target3 D information using the re-projection equation.The result of the experiment shows that the error of the camera calibration is less than 0.37 pixel, and the error of the target 3D information measure is less than 2 mm.This method realize the target 3D information measure automatically and accurately.(3) The helicopter rotor blade flapping angel measure method has been realized.Firstly, the definition and measure method of the helicopter rotor blade flapping angel has been researched. Secondly,according to the definition, the rotor coordinate system has been build and the target coordinates has been changed form the original coordinate system to the rotor’s by calculating the target 3D coordinates. Finally,The rotor blade flapping angel has been calculated in the rotor coordinate system.The simulation experiment shows that the error of the rotor coordinate system parameters is less than 2 mm. The value of the flapping angel is stable.And this method can meet the requirements of the helicopter rotor blade flapping angel measurement.