The Research Of The Error Compensation And The Technology Of Feedforward Control For The Permanent Magnet Synchronous Linear Motor

Permanent magnet synchronous linear motors are increasingly applied in high speed and high precision positioning system.The drive mode using the permanent magnet linear motor can directly provide linear motion,without intermediate conversion links,thereby reducing the error introduced by the transmission chain and avoiding shortcomings like reverse clearance of ball screw drive,inertia and insufficient stiffness.Then providing driving force without contact makes the system more stable,eventually obtaining high speed and high repeat positioning accuracy.However,Direct drive feed system omits intermediate conversion links,causing the system vulnerable to external disturbance factors(such as friction, the thrust fluctuation,etc.) which affects the system dynamic accuracy and is easy to cause the system unstable.It limits the application of permanent magnet synchronous linear motor.In the meantime,the method of feedback control only exists the response lag problem,which affects the tracking accuracy of the motor.Thus,it is necessary to research the method of restraining the friction disturbance and influence of the disturbance of the thrust fluctuation and the way of improving the system dynamic tracking accuracy.The three-closed controller is built based on dSPACE1103 and Copley Xenus.For the thrust fluctuation disturbance rejection problem,this paper firstly analyze the characteristics of the force ripple and build the mathematic model of the trust fluxtuaion based on the position frequency and initial phase information.Model parameters are identified through genetic algorithm method, The feedforward compensation controller is designed to achieve the suppression of the force ripple. For the friction disturbance rejection problem,this paper,firstly,analyzes the characteristics of the friction and chooses the Gauss model as the friction model. Secondly, speed feed-forward controller and acceleration feed-forward controller are designed and they decrease the tracking error obviously.With measured friction values of the motor under different speeds,the friction model parameters are identified through differential evolution algorithm, and the feed-forward controller is designed to achieve the friction suppression of the permanent magnet synchronous linear motor. For the problem of the tracking error caused by the method of feedback control,the adjustable factor fuzzy feedforward controller that combines fuzzy theory using Mamdani reasoning method is built with the experience obtained by tuning the motor ago. The simulation analysis results shows,when this feedforward is applied,that the biggest position tracking error of the motor is decreased from 17.8μm to 1μm;when this kind of feedforward is applied to the experiment system, the biggest position tracking error of the motor is decreased from 18.3μm to 4.3μm,which verifies the effectiveness of the proposed method.This paper builds experimental platform according to a permanent magnet synchronous linear motor controlled object. The friction and the thrust fluctuation suppression methods affecting the system tracking performance are studied, and a feedforward controller based on fuzzy logic theory is designed.It helps to improve the performance of direct drive servo and it is meaningful and valuable for the application of direct drive feed system.