Research And Implementation Of The Three-Axis Cnc System Contour Error Compensation Method

The feed servo control is one of the key technologies of the CNC(Computer Numerical Control) system. With the machining accuracy increasing, the CNC system servo control is proposed high demands. The contour accuracy directly affects the quality of machining parts, and gradually becomes an important indicator of the CNC system. This thesis studies the contour error compensation method in the machining process based on a three-axis servo control device. Through a lot of reading literature and summary, the cross-coupled iterative learning control method is proposed, and it is implemented based on NI Compact RIO controller and Lab VIEW development environment. This thesis studies the content and results are as follows:Firstly, the current situation of the CNC system is introduced. Reading the relevant literature, the current situation of contour error control is analyzed and summarized, and the cross-coupled iterative learning control method is proposed.Secondly, the overall framework of the three-axis CNC system and each axis feed servo control device are presented. According to the experiment, the data of the frequency characteristic is obtained, then the transfer function parameters can be estimated by using the least square fit method. The mathematical model of the feed servo control device is established eventually.Thirdly, some causes of the contour error are analyzed. Considered the characteristics of repeatability and matching for each axis in machining process, the cross-coupled iterative learning control is proposed to compensate for the contour error, further the effectiveness of the algorithm is verified through MATLAB simulation.Fourthly, the motion controller of the CNC system is designed based on NI Compact RIO, and the cross-coupled iterative learning control and the G-code interpreter algorithms are programmed based on Lab VIEW graphical language.Fifthly, the system hardware and software are tested. Both a two dimensional clover and a three dimensional concentric circles are machined using the designed three-axis CNC system. Experiment results show that the contour error can be decreased by the proposed cross-coupled iterative learning control algorithm.Finally, the work of this thesis is summarized, and the research works also be prospected in the future.