Research On NURBS Curve Fitting And Interpolation Algorithm For Robot Polishing

Since the introduction of the "Made in China 2025" strategic development plan,people have increasingly high requirements for the processing quality of various industrial products,especially for their surface accuracy.The fitting back calculation of complex curves on the work piece surface during grinding and polishing processing and the motion accuracy during machining and feeding directly affect the final surface accuracy of industrial products.For industrial robots,as representatives of new productivity,The design of NURBS curve fitting and interpolation algorithms is the key to improving surface accuracy during grinding and polishing machining.Currently,the commonly used NURBS curve fitting methods have relatively general fitting accuracy under the condition of compressing the initial data amount,and most traditional interpolation algorithms do not have speed foresight and there are sudden changes in acceleration,which cannot fully meet the requirements of high-precision machining.Therefore,in order to further improve the surface accuracy during grinding and polishing processing,this article takes industrial robots as the application object,Based on existing relevant research,explore NURBS curve fitting and interpolation algorithms,and the main research work is as follows:(1)By analyzing the problems of traditional local interpolation methods in NURBS curve fitting that require a large number of auxiliary control vertices,resulting in overly complex calculations and a single global approximation method that cannot take into account the local accuracy and global error of the curve,a NURBS curve fitting method based on iteration of the Whale Optimization Algorithm was proposed,with the initial control vertices obtained by local interpolation of feature points as the object,The whale optimization algorithm is used to globally approximate the curve to obtain the optimal control vertex,which greatly reduces the amount of data required for curve fitting and further improves the curve fitting accuracy.(2)Aiming at the problems of discontinuous feed rate and speed interference between speed characteristic points in traditional NURBS curve interpolation speed planning methods,adaptive speed constraints are first introduced to adjust the feed rate,and then considering the actual acceleration and deceleration capabilities during machining feed,a forward looking interpolation algorithm based on quadric polynomial speed planning is proposed,which makes the change of feed rate during interpolation motion continuous and improves machining flexibility,At the same time,forward-looking speed planning improves the speed interference phenomenon,making machining feed more efficient.(3)The proposed NURBS curve fitting method based on the whale optimization algorithm and the NURBS curve interpolation algorithm based on the forward planning of quartic polynomial velocity were simulated and validated,respectively,with a 6-DOF industrial robot as the application object,taking into account the kinematic constraints of the 6-DOF industrial robot in joint space.The experimental results were compared with other methods and analyzed.The experimental results show that the NURBS fitting curve obtained by this method has higher fitting accuracy compared to traditional methods.The improved NURBS curve interpolation algorithm effectively improves the acceleration mutation phenomenon and improves the machining flexibility of the system.