Pyramid Angle Measurement Methods Of Helicopter Rotor Blades

The helicopter rotor blades pyramid angle is a main examination index of the rotor characteristics which directly related to the helicopter safety and the other important performances. And it is the most important examination item in helicopter’s production, operation and maintenance. In order to improve the rotor blades pyramid angle measurement precision to satisfy with different measurement purpose, it is necessary to analyze and research the rotor blades pyramid angle measurement. Previous studies were limited by the testing technology development and no suitable equipment to support the studies, even if using certain equipment to test the pyramid angle and the low accuracy made the studies lose theirs significances.The helicopter rotor blades is researched in this paper, we research on the helicopter rotor blades pyramid angle measurement based on the laser technology, monocular vision technology and omni-directional vision technology, the Zernike moments sub-pixel edge detection operator key technologies, etc. The mainly contents of the article are as follows.1. The principle of helicopter rotor blades pyramid angle based on laser technology is analyzed, solving the blades height differences through different angle blades time value when they cross the same right triangle, puts forward a new optical structure which can obtain three coplanar lasers right triangle through two spectroscopes and a reflector. The design method of the bottom parallel data acquisition system and the top data processing system are researched. The linear velocity uncertainty and the time difference uncertainty which cause by laser un-coplanar are researched.2. The principle of helicopter rotor blades pyramid angle based on monocular vision is analyzed. The key parameters relationship between blades angle difference and the imaging distance, the relationship between the rotor system space offset and the imaging distance, the relationship between the focal length and the imaging distance are detailed researched. The calibration method for imaging system structure spatial position, dimensional orientation is proposed. The pixel calibration error uncertainty is studied. Design image processing software in order to extract rotor blades pixel values and convert them into corresponding spatial height. Finally design and implement of the experimental system based on monocular vision is researched and system relative error is obtained.3. Analyze the helicopter rotor blades pyramid angle principle based on omni-directional vision technology, using this theory mathematical model between the blades height difference and optical target is derived, the key technology between space object resolution and the parameter of the omni-directional vision system is analyzed and simulated. Two methods of the omni-directional system calibration including arbitrary image and fringe coordinate paper are compared. The fringe coordinate paper calibration method uncertainty is researched. At last the design and implement of measurement system is developing which obtain the system relative error and provide theory for later engineering practice work.4. Through discussion with the Zernike moments sub-pixel edge detection operator principle and calculation method, derived the Zernike moments radical polynomial value form0to12orders, based on which4orders Zernike moments9x9mask coefficient is given, the edge detection criterion based on4orders direction angle is proposed. Comparison with Zernike moments mask orders, distance model, step model, direction angle model edge detection ability and testified theirs accuracy.5. Observe the Zernike moments edge detection operator practice application ability through compared with common pixel level edge detection operator. Using4orders direction angle Zernike moments criterion in monocular vision. By comprehensive consideration the monocular vision and the omni-directional vision detection results, calculate the circle center and two rotor blades sub-pixel coordinates value, and test the above operators accuracy through experiment and simulation.