| As the core component of the machine tool,the servo feed system of CNC machine tool directly determines the machining accuracy of CNC machine tools.The change of inertia ratio and load inertia of servo feed system has an important influence on system control performance and natural frequency of mechanical structure.The paper takes the servo feed system of MCH63 horizontal machining center as the research object,the main research contents include four aspects: the influence of load inertia on the control performance of servo feed system,the influence of load inertia on the contour error and synchronization error of servo feed system,the influence of load on the dynamic characteristics of feed system,the identification of moment of inertia and the tuning of control parameters.Firstly,the structure,control mode and motion characteristics of each module of MCH63 servo feed system are analyzed,and its mathematical model is established.The two-axis motion friction model of feed system is measured by SERVO GUIDE software.The simulation control model is established in simulink.According to the inertia matching problem,the dynamic response characteristics,anti-jamming characteristics and contour errors of the system under different inertia ratios are analyzed,and the appropriate inertia ratio is given.Secondly,based on the mechanical structure characteristics of the dual-drive feed system,the important sources of synchronization error of the dual-drive feed system are analyzed by combining theoretical analysis with simulation,and the variation law of synchronization error of the feed system under different load inertia is analyzed.By measuring the synchronization error of Z-axis feed system under different load inertia,the correctness of simulation results is verified.Based on the theory of recursive least square method,forgetting factor is introduced into the algorithm to improve its correction ability to identify the system’s moment of inertia.On this basis,the identification results are fed back to the system controller,and the parameters of the controller are tuned online according to the transfer function of the mathematical model of the servo motor.The simulation results prove the accuracy of the inertia identification module and the effectiveness of the parameter tuning method.Finally,based on the energy method,the dynamic model of the double screw drive system is established.The influence of the load change of the worktable on the natural frequency of the feed system is studied by numerical calculation.The natural frequencies and modal modes of the worktable under different load masses are measured by modal experiments of machine tools,and the correctness of the calculation results is verified. |
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