Research On 5-axis Linear Interpolation And Error Control Method Based On Knife Contact

Compared with the traditional three-axis CNC machine tool,the five-axis CNC machine tool adds two rotating axes to the three translational axes.It can effectively avoid the problems of tool interference and collision during the machining process,and can obtain better parts surface.Machining accuracy,especially when machining complex,high-precision free-form surfaces.Linear interpolation is the most basic trajectory control method for CNC systems,which can achieve better processing results in three-axis machining.The current five-axis numerical control system generally adopts the linear interpolation method.Since the two rotating shafts and the three translational axes jointly realize the motion synthesis of the linear trajectory during the five-axis machining,the complex trajectory curve will be generated in the space after the tool swings.The tool contact path will also deviate from the pre-set linear path of the tool contact,resulting in a knife contact path nonlinearity error.The nonlinear error is the inherent error of the five-axis CNC machine tool.This paper focuses on a series of specific problems such as reducing the nonlinear error.The main research content of the thesis consists of the following three parts:(1)The motion mathematical model of five-axis linkage CNC machine tools with three different structural forms is discussed and the relationship between each axis coordinate system and its transformation relationship is established.The calculation method of the tool contact solution for machine tool post-processing is derived.Discuss the conventional five-axis linear interpolation process without cutter contacting(CC)and the process of five-axis linear interpolation with cutter contacting(CC).(2)Aiming at the compensation and repair of the nonlinear error of the five-axis CNC linkage CNC machining tool contact,the mathematical model of the AC doublerotation five-axis CNC machine tool kinematics transformation is established.Based on the analysis of the nonlinear error generation mechanism at the cutter contacting(CC),A nonlinear error compensation and repair algorithm for the linear path of the cutter contacting(CC)is proposed.In the proposed method,the corresponding cutter contacting(CC)is obtained for the current interpolation tool point,the error is judged for the tool contact point,and the position of the tool point is repaired by the cutter contacting(CC)error,and a new cutter location point is obtained.The interpolator delivered to the machine tool is machined to reduce nonlinear errors at the cutter contacting(CC).Finally,the MATLAB simulation proves that this method has a significant effect on reducing the nonlinear error of the cutter contacting(CC)path.(3)The interpolation acceleration/deceleration control algorithm is analyzed in the acceleration and deceleration process of the five-axis linkage numerical control system.Compared with other acceleration and deceleration algorithms,the application of S shape acceleration/deceleration control algorithm in the machining process is studied,and the S shape addition during the interpolation process is applied.When the deceleration interpolation algorithm does not have a uniform velocity section,the actual maximum machining speed is solved by the two-point iteration method,and the interinterpolation speed is transitioned to ensure smooth operation during the machining process.Finally,the S shape acceleration/deceleration interpolation control algorithm is used to simulate the correctness of the interpolation algorithm.