Detection Of Straightness Error Of Crankshaft Axis Based On Machine Vision

In response to the current problem of low accuracy and productivity, and the deficiency of geometric tolerance measurements during the process of detecting crankshaft journal, through the research of machine vision, a method of detecting straightness error for crankshaft journal axis based on machine vision was proposed in this paper. The performance index of machine in all aspects is largely determined and restricted by the quality of crankshaft. In the structure of crankshaft, the operation smoothness of engine is determined by the straightness error of its spindle. Therefore, the straightness error of crankshaft journal in engine was analyzed in this paper, through large numbers of experimental verification. The main research contents and results are listed as follows:(1) On the basis of error conversion, the evaluation model of straightness error for image data collection was established;(2) The image processing of spindle journal image was performed, which was collected by the acquisition system of journal image, such as image preprocessing, sub-pixel edge extraction, the fitting of axis and crankshaft, et al. Then, the image processing for the shaft end face was performed, and the template matching was introduced.The noise smoothing, threshold segmentation and the extraction of feature region during the image processing were solved. The data points extracted from images were transformed to the metric units in the world coordination, and the deep research of error calculation was conducted;(3) Through deep research, the method of detecting straightness error for journal axis automatically was designed, and the appropriate optics was selected according to the demand of research. And the experimental system of detecting straightness error for journal axis was established;(4) Through several experiments, the reason for straightness error generated in automatic detecting system was analyzed, and the optimal experiment method was chosen, reducing the experiment error and improving detection accuracy. The system calibration of detecting straightness error for crankshaft journal axis was completed during the experiment process.According to the research contents of this paper, large numbers of experiments detecting the straightness error for engine spindle were performed, and the final measuring results were compared with the data measured by CMM, indicating that the detecting method of straightness error for crankshaft journal axis has good performance, with the accuracy 1 μm and duplicate detection error less than 1 μm. The results show that this method can be applied for detecting the straightness error of crankshaft.