| Ring forging is an important forging workpiece.It is widely used in aerospace,petrochemical,nuclear power and other fields.With the development of science and technology and the increase of the complexity of ring forgings,the quality and measurement accuracy of ring forgings are required to be higher.The measurement of the outer diameter is the key technology to ensure that the ring forgings meet the technological requirements.Therefore,the measurement accuracy of the outer diameter of ring forgings had been paid a lot of attention by researchers.How to measure the outer diameter of ring forgings efficiently and accurately has become a research hotspot.In this paper,two measurement methods were proposed for the measurement accuracy of the outer diameter of ring forgings.The main innovative work was as follows:Firstly,based on the two-dimensional point cloud data characteristics and standard deviation theory,a point cloud data resampling method was proposed to measure the outer diameter of ring forgings.In this method,the densely distributed point cloud data was extracted from the laser scan data as the resampling result.The mean filtering method was used to smooth the extracted point cloud data,and the point cloud data with good circular arc characteristics was obtained.The principle of least square method was used to make ellipse fitting to the processed data.As a result the outer diameter information of ring forgings can be obtained.Secondly,on the basis of the above measurement method,a method with higher measurement accuracy was proposed.This method mainly combines laser scanning and CCD for measurement.In the measurement process,the point cloud data were successively divided into a group of three,and the position discrimination method of line fitting was used to simplify the point cloud data,in which the points below the fitting line were retained,and the points below the fitting line were excluded.At the same time,CCD image edge detection technology was used to obtain the edge points on both sides of the ring forging and transform them into the real space.The simplified laser point cloud data and the actual space points of the edge points on both sides of the ring forging were placed in the same Cartesian coordinate system.The outer diameter dimension information of ring forgings was obtained by circle fitting based on least square principle.In addition,the rotation formula was used to rotate the processed data to obtain the data points with complete sections,and the same processing was done for each section of the ring forgings to obtain the three-dimensional point cloud data of the ring forgings and construct its three-dimensional model.Finally,the outer diameter measurement platform of ring forgings was built.Standard ring forgings,first order ring forgings and third order ring forgings were used as measurement objects.The measurement results were compared with the standard values,and the error analysis was made to verify the feasibility and accuracy of the measurement method for the outer diameter of ring forgings. |
