Simulation Analysis And Optimization Of Detection Trajectory Of Tracking Error Of Five-axis Hybrid Machine Tool Based On RTCP

Hybrid machine tool is a new concept machine tool that has only appeared in recent years,Because it is the product of the combination of serial machine structure and parallel robot structure,which has high-tech added value.So it is also known as a “machine tool of the 21 st century”.In this paper,the 3-PRS parallel mechanism is taken as the main body of the hybrid machine tool,and then the mechanism was connected in the translation table in XYaxis,thus a new type five axis hybrid machine of five-degree-of-freedom was built.Base on the RTCP(Rotation Tool Center Point)function of CNC machine tools,the motion trajectory error of the tool tip caused by servo system tracking error of the hybrid five-axis machine tool was studied.Furthermore,the RTCP function of the machine tool is used for error detection.Compare with other methods,this detection method has the advantages of simple operation,flexible trajectory,high precision and less interference.By constructing a linkage simulation platform for hybrid five-axis machine tools,the research evaluates the detection performance of different RTCP trajectories on the tracking errors of each drive shift,and proposes an error detection optimization trajectory that is more suitable for 3PRS-XY hybrid machine tools.The detailed work of this paper is as followed:Firstly,The five-axis hybrid machine tool linkage simulation model needs to be established,the mathematical model of the hybrid machine's forword and inverse solutions are obtained by the geometric method.The simulation model of CNC machine tool's servo feed system was built,the items of three-loop control system of drive shaft was obtained and the servo control system model was optimized by adding feedforward,By studying the PID control principle,the relationship between the dynamic parameters of the servo system and the tracking error was analyzed,It provides advise for the parameters adjustment of machine's servo control system model,which is convenient for the subsequent simulation experiments.Then,Based on the kinematics control,the servo control system models of each drive shaft were combining to bulid up the five-axis linkage model,the model was used to simulate thre hybrid machines' tool point motion.Secondly,this paper study the detection performance of different RTCP trajectories for the tracking errors of each driving shaft,The simulation experiments were conducted to simulated the multi-axis linkage of the hybrid machine tool,the dynamic performance of the hybrid machine tool reflected by ths ISO standard trajectory and the function generated trajectory was compared,and the 8-shaped RTCP came form the function generated trajectory was selected,which is optimized for tracking error of hybrid machine.Finally,this study optimized the existing 8-shaped trajectory.Based on the of Jacobian matrix and first order perturbation,The transfer relationship between the following error of the hybrid machine tool and the position error of the tool tip was obatained.The relationship is used to analyze the sensitivity of the tool path to the machine tool linkage performance parameters.Taking the maximum sensitivity as the fitness value,the genetic algorithm is used to optimize the RTCP detection trajectory,and the superiority of the RTCP optimized trajectory in detecting tracking error of the hybrid machine tool is verified through simulation.