Research On The Compensation Method Of Frictional Force Disturbance In Precision Servo System

The servo system of CNC machine tools has been widely used in the field of modern precision machining and manufacturing.With the development of science and technology and the continuous improvement and iteration of machining technology,the quality requirements for processing devices are also continuously improved,and the performance of the servo system also puts forward higher requirements.However,the friction disturbance in the servo system seriously inhibits the performance and hinders the development of the servo system.Therefore,the compensation of friction disturbance in the system has strong research value and application prospect.Aiming at the friction disturbance in the precision permanent magnet synchronous servo system,this thesis realizes the compensation of the friction disturbance of the system by means of theoretical analysis modeling,simulation analysis and experimental verification.Firstly,the analysis and modeling of each link of the precision servo motion control platform are carried out,and the mathematical model and vector control strategy of the permanent magnet synchronous motor in the synchronous rotating coordinate system are introduced.At the same time,a mathematical model of the mechanical transmission links of the servo system is established.On this basis,the source of the friction force of the system is analyzed,and a LuGre friction force model is established for the system friction force to achieve an accurate description of the friction torque.MATLAB/Simulink simulates the identification method and proves the validity of the parameter identification method.Secondly,the three-loop control structure of the permanent magnet synchronous servo system is introduced.On this basis,the friction force feedforward compensation method is designed by using the LuGre friction force model to realize the compensation of the system friction force.In the feedforward compensation method using the friction force model with fixed parameters,changes in the operating environment of the system will lead to changes in the parameters of the friction force model,resulting in under-compensation and overcompensation of the friction force in the actual compensation process.The force disturbance is observed and further compensated by the reduced-order extended state observer with simple structure and strong disturbance observation capability,to reduce the influence of friction disturbance on the system position tracking accuracy.Finally,in order to overcome the problem that the parameters of the friction force model may change when the fixed parameter friction force model is used for compensation,which will lead to poor compensation effect,the friction force adaptive controller is designed based on the Lyapunov stability theory to realize the friction force disturbance.The self-adaptive compensation improves the control precision of the system.In this thesis,the proposed friction disturbance compensation method is experimentally verified on the permanent magnet synchronous precision servo system platform,which proves the effectiveness of the proposed method.