Research On Modeling And Compensation Method Of Contour Error In Complex Surface Machining

In the multi-axis CNC machining system,the machining quality of the part surface is the most important concern of many scholars and researchers.Due to factors such as the response delay of the servo mechanism and the dynamic structure mismatch between the axes,tracking errors and Contour error.Among them,contour error is the main factor affecting the machining quality of the workpiece.How to calculate and reduce the contour error is the main means to ensure the machining quality of the workpiece surface.Therefore,this topic will study the compensation algorithm of contour error.Modeling and calculation,tracking error calculation and compensation algorithm design,system coupling analysis,and design of collaborative error compensation algorithm as research content.Considering the structural coupling of the multi-axis machining system,the stability of the coupled system is analyzed.After designing the contour error and tracking error compensation algorithms,the uncertainty factors of the system are analyzed to design a cooperative compensation algorithm to achieve simultaneous compensation of tracking errors and Purpose of contour error.The main content and results of this article are as follows:First,Analyze the causes of tracking error and contour error,comprehensively analyze the current status of research at home and abroad,study the theoretical methods and applications of tracking error and contour error calculation and control strategies,study the characteristics of CNC servo control systems and error characteristics,and analyze PID control The application of theory in NC machining,the function analysis of proportional,integral and differential control in PID control is realized through MATLAB,and the parameter tuning method of PID controller is integrated.Second,A method based on the three-point arc theory is proposed.First,the reference position closest to the actual position is calculated based on the interpolation reference position and the actual position during processing,and then the nearest reference position and its neighboring positions are calculated.The approximate circumscribed arc formed by the left and right points is used to calculate the distance from the actual position to the arc,that is,to obtain the contour error of the tool tip position.When calculating the contour error of the tool direction,a proportional factor is introduced to ensure the tool tip position and the tool direction.The coordinates are consistent.The algorithm based on the three-point arc theory only needs to consider the coordinates of the actual position and the reference point closest to the actual position.The calculation method can also accurately calculate at large curvatures.Third,design a collaborative error compensation algorithm,first design the tracking error compensation algorithm and the contour error compensation algorithm separately.First,for the single-axis tracking error,a closed-loop transfer function combined with a proportion is used to model and analyze the single-axis tracking error to obtain the tracking error compensation value,and a compensation algorithm is designed to improve the single-axis processing accuracy.The contour error is modeled and analyzed.An algorithm based on the space approximation circle is proposed to calculate the contour error magnitude,and a contour error compensation algorithm is designed.It is verified by experiments that the proposed tracking error calculation algorithm and contour error calculation algorithm can achieve ideal calculation results in high speed and high curvature machining.Fourth,After obtaining the compensation values for tracking error and contour error,considering the interaction between the axes,based on the traditional cross-coupling control,analyze the stability of the coupled system,and combine the tracking error error compensation value with the contour error compensation value.,Calculate the comprehensive contour error compensation value,design a coordinated error compensation algorithm,and perform collaborative real-time compensation for contour and tracking errors.Experiments verify that the proposed compensation algorithm has a significant improvement effect before and after error compensation.