Research On Disturbance Compensation Technology For Permanent Magnet Linear Synchronous Motor Servo System

The motion control for various types of linear motor servo system has attracted much attention with the high-speed and high-precision machining needs growing.The permanent magnet linear synchronous motor(PMLSM)servo system has many advantages,such as large thrust,fast response and high accuracy,and it has been widely applied in industrial production.For PMLSM that is vulnerable to influence of parameter change,unmodeled dynamics and external disturbances such as friction force,force ripple and so on.Periodic learning disturbance observer(PLDOB)and extended Kalman filter(EKF)were designed to compensate periodic disturbance and aperiodic disturbance respectively.First,the basic structure and working principle of PMLSM were described,the causes of the disturbance in PMLSM and its influence on the control accuracy of the system were analyzed,the dynamic mathematical model of PMLSM with uncertain factors such as disturbance was established,and the basic principle of PMLSM servo system vector control and coordinate transformation were introduced,which laid the foundation for the design of disturbance compensation scheme.Then,the PLDOB was designed in order to compensate for the periodic disturbance existing in the PMLSM servo system that performs the repetitive motion tasks.The disturbance is estimated by the disturbance observer(DOB)at the initial time period,and then,the estimated disturbance is utilized as the initial condition of the periodic learning law in PLDOB to update the disturbance for each subsequent time period.The innovations of the disturbance compensation scheme are that it requires no mathematical models of disturbances and control laws of model parameters;it was designed from the point of view of disturbances directly;and it also can overcome the limitation of DOB in disturbance compensation.The effectiveness of the proposed disturbance compensation scheme was verified by system simulations.Finally,the 7th-order EKF algorithm was designed to compensate for the non-periodic disturbance existing in the actual PMLSM servo system.A disturbance model which consists of position dependent was developed and utilized as a disturbance feed-forward compensator.Then,the initial position of the translator and varying mass information are estimated by the 7th-order EKF and reflected to the disturbance feed-forward compensator.In addition,the coefficients of the disturbance model are adjusted adaptively to create synchronization between the disturbance model and real disturbance,and achieve the purpose of varying mass estimation and disturbance compensation.The system simulation results prove the convergence of the 7th-order EKF algorithm and its validity and feasibility for compensate non-periodic disturbance in PMLSM servo system.