Large Scale Measurement Without Guide For Machined Part

Large-scale measurements can be divided into displacement measurement and absolute distance measurement. The measurement of absolute distance is a key factor to ensure the equipment's quality in manufacture and installation of the large-scale mechanical equipment and weaponry. For a long time, many domestic and foreign scholars have made a lot of research and tried a variety of measurement methods, however, there is not an ideal way to realize the large-range, high-precision and no-guide. In this paper, the length measurement technology with large range for large part in major equipment's manufacturing process was researched in particular, the primary content includes:Surface's reflective properties of large machining parts were analyzed in theory. The surface was treated as a random process described by random distribution theory, then build the illumination model of the measurement system based on surface parameter's statistics description random model. The influence of laser speckle to measurement uncertainty was analyzed based on laser speckle theory, the effect of surface roughness decline to uncertainty was also analyzed.Base on the laser trigonometry measurement theory, a new measurement device was constructed by adding half transparent and half reflecting mirror and CCD, and find the best way to process the signal by studying signal processing methods, design the program for serial communication based on Visual C++ 6.0, the effect factors were analyzed and the corresponding processing methods were also provided, the large range measurement of large machine parts was realized..The facular center orientation in CCD and neural network compensation for the non-linear error caused by measure theory were discussed. The optimal threshold of the facual image segmentation was calculated by iteration threshold method, intercept the imaging area of facual feature point, and then realize sub-pixels orientation of the position feature center position using bilinear interpolation.The BP neural network was introduced to compensate the non-linear error of the system for its preferable arbitrary approximation and self-learning ability for nonlinear function.At last, some parameters of the measurement system such as measure range, repetitive precision and error were presented by experiment, the result shows that the system work well in large-scale measure.