Research On Interpolation Precision Control And Error Compensation Method For Hybrid Machine Tool

This dissertation takes a five-axis hybrid machine tool based on a 3-DOF parallel spindle head developed by Tianjin University as the research object.In order to improve its machining accuracy,in-depth analysis of the interpolation process and error compensation method is carried out.The specific work and main results are as follows:Based on the robot kinematics,the kinematics characteristics of hybrid machine tools are studied.Workspace interpolation and joint space interpolation are used to control the machining path of the machine tool.In the workspace,a dual-line interpolation algorithm is used to coarsely interpolate the tool path.In the joint space,the motion of each drive shaft is finely interpolated by using the PVT algorithm.In order to verify the validity of the interpolation strategy,a simulation analysis was carried out.The results show that the proposed trajectory control method can effectively reduce the contour error caused by linear interpolation of tool angle.In order to achieve precise interpolation,a two-step velocity control method corresponding to the interpolation strategy is proposed.For the continuous small linear segments,a dual-arc corner transition model is adopted and the maximum velocity at the transition point is derived according to the error and motion constraints.In order to verify the effect of the transition model,it is applied to the adaptive S-curve velocity control method.The velocity simulation of partial paths of the S specimen shows that the proposed control method not only ensures the smooth movement of the tool,but also effectively reduces the machining time.The shortcomings of the model-based error compensation method are expounded.Based on the continuity and correlation of spatial error,a grid-based non-model error compensation method is proposed.The method mainly includes error estimation and error compensation.When constructing the compensation model,the tool error is decomposed into the orientation error and position error according to the structural and motion characteristics of the hybrid machine tool.When meshing the error space,A space conversion method is proposed by analyzing the parameters that affect the orientation error and position error.The irregular space of A3 head are mapped into standardized space.On this basis,a grid-based polynomial error estimation model is constructed in the corresponding error space.Finally,the error compensation is implemented by modifying the system input through the error estimation model.The simulation results show that the non-model error compensation method can achieve better effect.