Critical Techniques And Applications Of Real-Time Error Compensation On High-End CNC Machine Tools

With the rapid development of aerospace technology and electronic information technology,the demand for high-end CNC machine tools,which is represented by five-axis machine tool,is increasing rapidly.For the five-axis machine tools,there is a large gap between china and foreign countries,such as Germany,Japan.With the support of the National Science and Technology Special Project "Error Measurement,Analysis and Compensation Technology for CNC Machine Tools",the research of real-time error compensation techniques is carried out on a table-table five-axis CNC machine tool.The main research contents of this thesis are described as follows:(1)The volumetric error model of five-axis machine tool is build based on the Homogeneous Transfer Matrix method.According to the structure feature of the research subject,moving coordinate systems attached to each axes are established and their initial position relation is clarified.Then the transformation matrix between any two adjacent parts in the kinematic chain is derived by Homogeneous Transfer Matrix method.Finally,the forward kinematics model and volumetric error model of the five axis machine tool are obtained.(2)A real-time calculation strategy of volumetric-error compensation value is proposed.It is time-consuming to solve the kinematics equation which contains all geometric error components using a computer,therefore it is not suitable for real-time error compensation.By solving ideal kinematics equation iteratively and modifying the posture of tool in the workpiece coordinate system gradually,the posture of tool can be corrected in the end.In this way,the compensation values can be derived and the real-time requirement can be satisfied.(3)The distortion rule of measured values along with set-up errors is obtained through mathematical simulation,and a new identification and separation method of set-up errors is put forward.Simulation and experimental prove that the proposed method can identify set-up errors with high accuracy.On this basis,by separating ball bar set-up error firstly,the classical error measurement and identification method of rotating axes is improved and higher accuracy can be achieved.(4)A new real-time error-compensation implementation method is presented,which is based on secondary development of SIEMENS 840 D Human Machine Interface.Since the SIEMENS 840 D CNC has an open structure,a real-time error compensation application is developed which can be embedded into the Human Machine Interface.By choosing appropriate machine parameters as the compensation interface,real-time volumetric error compensation is realized using the dynamic data exchange protocol.Based on the above research,a solution which contains error component measurement,volumetric error modeling and error compensation technique is proposed,and the effectiveness is verified through machining comparison experiments.