Generation Methods Of Bidirectional Uneven Fringes And Its Application In 3D Measurement System Of Aero Engine Defected Vanes

With the rapid development of international aviation industry, the total number of aircraft expanded quickly. Aerospace business is attracting more and more attention in the same time. As the key part of aviation industry, aeroengine vanes has been the key repair object since it is numerous, complex-shaped, easily defective and expensive to be manufactured. Since 3-D measurement can provide data basis for aeroengine vanes automatic welding repair equipment, research of high precision 3-D measurement technology is significant for our country.In the system of vanes’ phase measuring profilometry(PMP), oblique angle projection of vertical and horizontal even fringes on the reference plat can obtain uneven fringes of changing period, which can lead to pixel-phase nonlinearity in the result of phase unwrapping. To solve this problem, generation methods of bidirectional uneven fringes were proposed.A generation methods of vertical piecewise uneven sine fringes has been proposed, which makes the fringes’ relationship of pixel-phase nonlinearity. There made a simulation experiment on the plane, which is 50 mm high, the result turned out to be that the mean value of measurement error is 0.4882 mm when projected uneven fringes, and the mean value even fringes projection is 3.0648 mm. The contrast simulation experiment was made with the arch bridge, which is 100 mm high. The result indicated that uneven fringes can made error range of the degree of symmetry between 0.23%-2.31%, even fringes can made error range of 24%-27%. Thus that project vertical piecewise uneven sine fringes can improve measurement the accuracy.Generation method of vertical piecewise uneven gray code and trapezoidal fringes has been proposed. According to the simulation experiment on the plane, uneven gray code and trapezoidal fringes can improve the nonuniformity of the projecting result.Generation method of horizontal partitional uneven sine fringes has been proposed too. The method can generate uneven fringes. This kind of uneven fringes’ pixel-phase realationship can be described by partitional function. By projecting this kind of fringes can get even fringes on reference. There made a simulation experiment on the plane, which is 50 mm high. The result showed that the mean value of uneven fringes projection measurement error is 0.4099 mm, and the mean value of even fringes is 2.5235 mm. The result of simulation experiment on the globe, which is 50 mm high, turned out to be that the rang of the symmery error is between 3.1%-9.3% when project even fringes, and it tured out to be 0.03%-1.6% when projected uneven fringes. So measurement accuracy can be increased by horizontal partitional uneven fringes projection.Based on even and picewise uneven sinusoidal fringes, simulation experiment and actual experiment has benn implemented, and can obtain vane’s points cloud.