Research On The Parametric Inverse Algorithm Of Cam Profile Curve Based On Random Sampling Consistenc

Manufacturing industry is the foundation of national economy.The mutual introduction,absorption and innovation of scientific and technological achievements among countries has become an important means to promote the development of manufacturing industry and technological progress as well as a key engine to catch up with other countries.The design and manufacture of cam mechanism is a key technology in manufacturing industry,which mainly controls the motion law of follower through the change of its contour curve.Cam mechanism is widely used in imported automation machinery such as high-speed cigarette packer and printing equipment.When it is necessary to innovate the imitation,digestion,absorption or modification of cam parts and products without CAD model,it is an important step in the process of introducing digestion,absorption and domestication to create geometric model of existing objects by using reverse engineering technology.The existing cam reverse seeking methods mainly approach the measured data points through fitting,interpolation,correction,fairing and other algorithms,or reverse seek the motion law through motion simulation.These methods do not reverse the original design parameters of the cam,and can not get the original cam intention and design parameters.The contour curve after reverse calculation can not realize modification and innovative design by modifying the design parameters.Therefore,this thesis puts forward the parametric reverse calculation method of cam contour curve,and studies the cam angle conversion algorithm,the parametric reverse calculation algorithm of cam contour curve and the cam parametric modeling technology respectively.The main contents and innovations of this thesis are as follows:(1)Parametric representation of cam profile curve: this thesis studies the relationship between cam angle and cam center angle in the process of parametric representation of cam curve,puts forward the cam angle offset model,analyzes the causes of cam angle offset in principle,deduces the cam angle conversion algorithm through the corresponding geometric relationship and formula,and applies it to the parametric reverse algorithm to preprocess the cam contour data;(2)The reverse algorithm of cam contour curve parameterization: the inverse method of cam parameterization is proposed,and the corresponding algorithm is designed to estimate the original design parameters of cam.The experimental verification is carried out with manual simulation data and measured data respectively,and the error of each parameter is calculated through the simulation data.Aiming at the problems that there are many parameters to be solved in the process of parametric reverse engineering,resulting in huge solution space,low efficiency of solving with standard RANSAC algorithm and large error of the result,an improved piecewise error back propagation optimization algorithm based on RANSAC is proposed.By comparing the three algorithms of standard RANSAC,RANSAC + step-by-step iteration and RANSAC + step-by-step iteration + piecewise error,according to the test results,it can be seen that the efficiency of the combined algorithm of RANSAC + step-by-step iteration + piecewise error is greatly improved,and the efficiency and convergence speed of the parametric reverse algorithm are improved;(3)Cam parameter verification: aiming at the problems of complex cam modeling and low modeling efficiency,the parametric modeling of cam contour curve and the one key visualization module of characteristic curve are developed based on UG,which can greatly improve the efficiency of cam mechanism design and reduce the development cycle of corresponding product design.The corresponding parametric model is established by using the parameters after reverse calculation,and the model is simulated and verified by motion simulation software.The results show that the acceleration curve after parametric reverse calculation is consistent with that after fitting fairing,the maximum angular acceleration after parametric reverse calculation is reduced by 11.4%,and the fluctuation caused by measurement and fitting fairing error is reduced to a certain extent.