Research On Control Technology Of AC Servo System Based On Model Tracking

AC servo system has the characteristics of small volume,high response,high precision and so on.It is widely used in CNC machine tools,high-end electronic equipment,robots and other automation equipment.However,in flexible connection applications such as electronic package swing arm and robot linkage mechanism,the system is prone to mechanical vibration,which will affect the dynamic response and control precision of the system,and even damage the equipment in serious cases.In view of the above phenomenons,a control method of AC servo system based on model tracking is proposed.By constructing the reference model which simulates the actual servo system,identifying the characteristic parameters and adjusting the control parameters of the reference model,the system input response performance and motion tracking accuracy are improved.Firstly,based on the two-mass model of servo system,the influence of vibration on the servo system are analyzed,which combined with the vibration characteristics of the system.On the basis of the traditional servo three-ring control structure,a servo control scheme using model tracking is proposed.Based on the input response performance of the model and its simulation accuracy,the reference model of the model tracking method is built.Taking the model iteration real-time performance as the index,the two-mass model and the Q axis voltage equation are simplified.The motor load model and the motor electrical model are established.Using Simulink model for simulation and verification,the simulation results are compared with the servo experimental platform.The high input response performance and simulation accuracy of the reference model are verified.In order to further improve the simulation precision of the reference model,the least square method is used to identify the characteristic parameters of the load model,and the step DC excitation method is used to identify the phase resistance parameters of the electrical model.Simulation and experiment show that the identification error is within11 % and the identification accuracy is good.In order to optimize the comprehensive performance of the reference model,the setting method is designed based on the model transfer function.The zero-pole cancellation method is used to tune the PI parameters of the current loop according to the performance index of the second-order system.The pole placement method is used to configure the same real pole position,and the PI control parameters of the speed loop are set.The Simulink model simulation shows that the tuning PI parameters can achieve good comprehensive performance for the reference model.Finally,the model tracking control method designed is integrated into the self-designed driver of the research group,and the related experiments are carried out on the two-mass servo experimental platform.The experimental results show that,compared with no model tracking control,for the position step command,the position response of the model tracking control has no overshoot while its rise time is reduced by 29.8%.For the velocity step signal,when the overshoot is 3%,the speed response rise time of the model tracking control is reduced by 72%,and the position tracking error is reduced by59.7%.It is proved that the proposed model tracking control has the advantages of high tracking accuracy and strong responsiveness.