Study On Contouring Control Of Mirror Milling For Large Thin-walled Parts

With the rapid development of aerospace industry and growing complicacy of space missions,the demand for larger payload capability becomes more prominent.Large thin-walled parts are critical to the heavy-lift rockets,large aircrafts and many other national major projects as the key components.Large thin-walled parts have the characteristics of large size,low structural rigidity,irregular profile,high material removal ratio,long processing cycle and so on.For the sake of meeting the processing demands of large thin-walled parts,the research group came up with a NC milling system depended on mirror processing approach to resolve the processing difficulties of large thin-walled parts.In terms of this background,this paper mainly contrives the CNC equipment of large thin-walled parts mirror milling facility,and researches the contouring control of machining processing.According to the demands and technical indexes of large thin-walled parts mirror milling facility,this paper displays the design solution of open CNC equipment which is fit for the mirror processing procedure of thin-wall parts.This paper investigates the overall structure and functional performance of the open CNC equipment,and deploys the "IPC + motion controller" method of open CNC equipment.The hardware platform and full-closed loop servo structure are designed and modular software structure consisting of user management,motion control and communication control are established.In regard to the contouring control of the equipment in the mirror milling processing procedure,this paper simplifies the issue to dual axis contouring control,and comes up with the corresponding solutions.This paper proposes an improved contour error model aiming at estimating the contour error and compares the precision with the traditional contour error models.A contouring controller based on cross-coupled control structure is designed in this paper.Simulations on the performance of different contour error models and the precision of contouring controllers based on different contour error models are conducted on the MATLAB/Simulink software system.Finally,for the sake of testing the precision of the improved contour error model and validity of the raised contouring controller,this paper contrives a dual axis contouring control facility based on the NC cross sliding table and the LabVIEW software system,and the control algorithm is utilized to the controlling of the dual axis motion platform.The experimental results indicate that the improved contour error model can enhance the processing precision effectively.Compared to the traditional tangent model,the average,maximum and RMS values of the estimation biases have decreased 64.47%,52.89% and 62.50%;the contouring controller using cross-coupled control structure based on the improved contour error model can largely improve the contouring control precision,the RMS value of contour errors has decreased 89.61%,48.39% and 11.11% compared to the structure without cross-coupled control structure.