Research On Cnc Algorithms And Design Of CNC System For A Five-axis Hybrid Machining Robot

The five-axis hybrid machining robot integrates the advantages of series and parallel mechanisms and is promising in important manufacturing such as aerospace industry.The purpose of this article is to develop a open Computer Numerical Control(CNC)system for a new five-axis hybrid machining robot to fully utilize its motion and machining capabilities.The main research contents of this article are as follows:Firstly,the smoothing method for the five-axis linear toolpath is studied,and a local smoothing algorithm and a global smoothing algorithm based on cubic B-spline curves are designed.For the local smoothing algorithm,the rotation vector is used to describe the change of the tool orientation,and the tool orientation is smoothed in rotation vector space,which effectively realizes the second-order continuous change of the tool orientation with the movement of the tool tip at the transition joint.In the global smoothing algorithm,the double-B-spline curve is used to fit the five-axis toolpath.An adaptive noise reduction method for curvature curve is designed,the Bspline node is initialized with the curvature characteristics,and the nodes are further refined according to the fitting error,which achieves strict control of fitting precision and compression of path data.Secondly,a novel adaptive velocity planning method for the five-axis robots is proposed.Taken the bow height error,tool tangential and each axis velocity,acceleration and jerk of each axis and tool feed into consideration,a velocity planning model was established with machining efficiency and velocity smoothness as optimization target.The model optimization variables are compressed by constructing the velocity curve in the form of b-spline.A robust velocity curve solving strategy based on BFGS is designed.The simulation results show,the algorithm is efficient and the planned velocity profile is smooth and can effectively improve the machining efficiency under the set constraints.Finally,the CNC system was designed and developed based on the Twin CAT3 platform.With multi-thread parallel frame design and reasonable assignment of threads and computing resources,the computer performance is fully utilized.The core modules such as human-machine interface,code compilation,path detection,and manual control have been developed.Besides,a B-spline curve accurate interpolation method has been designed based on Newton’s method.The numerical control system is applied to the hybrid machining robot,and its effectiveness is verified in the actual movement and machining tests.