| As a key part of the computer numerical control(CNC)machine tools,the CNC turntable can not only realize circumferential feed,but also achieve accurate CNC indexing,which can realize the processing of complex curved surfaces such as spiral surfaces and linkage with linear coordinate feed.Efficiency and processing accuracy play a very important role.However,with the rapid development of advanced manufacturing,the machinery industry has put forward higher requirements for the quality of machine tools,product accuracy and reliability,and the dynamic characteristics such as the controllability and stability of existing rotary tables can no longer fully meet the needs of the market.This paper takes the fourth-axis drive control system of FANUC 0i Mate MD CNC system as the research object,and focuses on the electromechanical characteristics of the fourth axis servo control of FANUC 0i Mate MD CNC system.(1)Based on an overview of the current status of the research on the dynamic performance of the feed servo system of the CNC rotary table,the composition of the fourth-axis drive control system of the FANUC 0i Mate MD CNC system and the performance index requirements to be achieved are analyzed and studied.The experimental platform of servo control VMC850 CNC machining center and the CNC rotary working table of the fourth axis feed servo control mechanical drive device are described.(2)Firstly,based on the principle of mechanical dynamics,the dynamic equations of the mechanical transmission system of the numerical control turntable are established.On this basis,the natural frequency and vibration mode of the mechanical transmission system of the turntable are obtained by modal analysis.The modal sensitivity is analyzed.Through the above analysis,the factors that have the greatest influence on the natural frequency in the rotary table drive system are obtained,and the methods for improving the natural frequency are given.Secondly,the mechanical transmission system of the turntable is simplified into a second-order system through research,and the influence of the damping coefficient on the time-domain response and frequency-domain characteristics of the turntable is analyzed.Based on this,the means for improving the characteristics of the mechanical transmission system of the turntable are given.(3)Using MATLAB software to establish a complete model of CNC turntable closed-loop servo system,design and calculation of PID controller of servo system current,speed and position control loop,and the time domain of each control link of the system with the help of MATLAB/Simulink,the frequency domain characteristics are analyzed,and the design parameters of the control links of position,speed and current are obtained,which reaches the engineering control level required by the CNC turntable servo system.(4)Based on the CNC turntable servo system model,MATLAB/Simulink is used as a tool,and the particle swarm optimization algorithm is used to optimize the PID parameters of the system.Using GISE as the optimization criterion,a system optimization model is established on the Simulink platform,combined with the particle swarm optimization algorithm program,the system parameter optimization simulation is performed by selecting different initial values and ? values,and the obtained optimization results are analyzed and verified by the system It is concluded that when the parameter ? is 0.003,the GISE objective function is more ideal for PID parameter optimization.The optimized parameters improve the dynamic performance of the system to a certain extent.In this paper,a series of simulation analysis methods are used to study the influencing factors and parameter optimization of the electromechanical characteristics of the fourth axis servo control of the FANUC 0i Mate MD numerical control system.It provides theoretical guidance for the realization of the fourth axis feed control of CNC machine tools in engineering application research. |
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