| The permanent magnet linear synchronous motor has the characteristics of fast dynamic response and large thrust.At the same time,because of its "zero transmission" mechanical structure,it eliminates the adverse effects of motion lag and nonlinear errors caused by traditional mechanical transmission devices,making the high-precision linear positioning has become possible,so it has been widely used in the fields of industrial automation,ogistic transportation and rail traffic.However,due to the unbuffered and direct-drive mechanical structure of the permanent magnet linear motor,under low-speed operating conditions of the motor system,the disadvantages of external disturbance,positioning force disturbance of the permanent magnet linear motor body and low resolution of the displacement sensor will limit the low-speed permanent magnet linear motor system.Steady state and dynamic performance improvement.Therefore,this subject takes the permanent magnet linear synchronous motor equipped with a low-resolution sine and cosine encoder as the research object,and uses the linear motor vector control as the starting point to analyze and study the influencing factors of the permanent magnet linear motor at low speed.Based on this Select the appropriate control algorithm to suppress low-speed speed fluctuations and improve the low-speed performance of permanent magnet linear motors.For the issues of speed fluctuations of permanent magnet linear motors caused by the low resolution of sine-cosine encoders in low-cost application occasions,which cannot update the accurate position and angle information required for motor control in time,a new position interpolation algorithm utilizing the features of cangent and cotangent function is proposed to get the high-resolution position of linear motor with sine-cosine encoder.The subdivision principles and the influence of encoder deviation are discussed theoretically,and the corresponding deviation compensation measures are put forward.Simulation results verify the correctness of position interpolation algorithm and compensation measures.In view of the problem that the speed of the permanent magnet linear synchronous motor fluctuates periodically under the influence of the positioning force when it runs at a low speed,combining the structural characteristics of the PMLSM and the distribution model of the linear motor's magnetic field,using the vector magnetic potential equation and the boundary conditions of the magnetic field,a mathematical analytical models of the cogging effect force and the end effect force of the PMLSM are established,Maxwell 2D finite element simulation is used to verify it's correctness;the q-axis current instantaneous injection strategy is adopted to suppress the periodic speed fluctuation of permanent magnet linear motor,simulation results verify the effectiveness of the proposed detent force suppression algorithm.Aimed at the problems of poor anti-disturbance performance and large dynamic speed fluctuation of permanent magnet linear motors in low-speed operation situation with dual PI controler,an improved linear active disturbance rejection speed controller is adopted to solve the problems.Considering the defect of traditional auto-disturbance controller,which has steady observation error for slope disturbance,the optimization measure of a cascade of extended state observers is proposed to eliminate the steady observation error of the slope disturbance and to improve the observation speed and accuracy for different forms of disturbance,and then to improve the anti-disturbance performance of permanent magnet linear motors.The simulation results show that compared with PI controler and classical linear active disturbance rejection controller,the improved linear active disturbance rejection controller can restrain the dynamic speed change of permanent magnet linear motor better and can shorten the dynamic recovery time,can improve the low-speed dynamic performance of permanent magnet linear motors effectively. |
PDF Full Text Request