Research On Automatic Measurement Method Of Car Seat Piece Size

The cutting piece is an indispensable middleware in the manufacturing process of the finished car seat.The precise measurement of its geometric dimensions is the key to quality control.At present,the size measurement of cutting piece is mainly manual,and the measurement accuracy and efficiency cannot meet the needs of industrial production inspection.Therefore,the research on automatic measurement of cutting piece sizes is of great value.In this thesis,an automatic measurement method based on machine vision is proposed to measure the size deviation between cutting piece and CAD.First,based on the combination of image edge shape features and geometric moments,the method of retrieving the CAD corresponding to the cutting piece is studied,which solves the problem that the unique CAD cannot be retrieved from the template library based on the shape features alone.Secondly,according to the characteristics of easy deformation of cutting piece,a matching algorithm based on shape segmentation is researched to improve the matching accuracy of cutting piece and CAD.Then,the sub-pixel edge extraction method based on the gray moment of the image is used to improve the accuracy of the edge detection of the cutting piece,and then obtain a more accurate outer contour deviation.After the overlapping display of cutting piece and CAD by affine transformation,the circular feature and non-circular feature are extracted by using the method of roundness,rectangularity and position constraint,so as to solve the difficulty of extracting the internal feature of cutting piece when the shape is unknown.Finally,a corner-constrained notch detection method is proposed,which extracts the notch on the CAD and the cutting piece respectively,and then calculates the deviation of the notch position and depth of the two.In order to verify the method in this thesis,the experimental results in the field of view of 700mm×500mm show that the accuracy is 99.96% when the corresponding CAD is retrieved from the data set of this thesis(including 7539 cutting piece),and the matching accuracy between cutting piece and CAD is improved.When measuring the size deviation of the two,the maximum deviation of the outer contour is 0.5mm,the maximum deviation of the center position and diameter of the inner circular hole and the maximum deviation of the center position and outer contour of the non-circular hole is 0.3mm,and the maximum deviation of the notch position and depth is 0.3mm,which meets the needs of industrial production.