Research On Current Decoupling Control Based On Active Disturbance Rejection For PMLSM

Due to the advantages of high magnetic density,small size,fast heat dissipation,permanent magnet linear synchronous motor（PMLSM）has direct drive structure and large thrust characteristics,and it is widely used in high-speed and high-precision applications such as medical treatment and optoelectronics.However,the currents of PMLSM have a strong coupling phenomenon,which reduces the robustness of the system.In order to solve the disturbance of parameter changes and the problem that the d-q axis current cannot be decoupled due to parameters variation during the operation of PMLSM,an active disturbance rejection controller and an improved extended sliding mode observer（IESMO）are designed to combine the current deviation control（CDDC）.It realizes a certain degree of decoupling for d-q axis current,reduces the sensitivity of the system to parameter changes,and improves the robustness of system.Firstly,the structure and principle of working and coordinate transformation theory for PMLSM were introduced.The mathematical model of PMLSM considering the influence of parameter changes was established under the rotating coordinate axis,and the dual-loop PMLSM vector control system with the maximum thrust per ampere was established based on the vector control theory.It laid the foundation to design CDDC,IESMO and active disturbance controller.Then,in view of the inability of PMLSM to decouple the d-q axis current when parameters vary,a current deviation decoupling control scheme based on an improved extended sliding mode observer（IESMO-CDDC）was designed.From the point of difference between the reference and actual current,d-q axis cross coupled branch was introduced.Then the current deviation decoupling controller（CDDC）was designed by establishing the current control dynamics with the coupling term and calculating the coupling term for system compensation,which weakened the influence of the d-q axis current coupling.However,the decoupling value cannot be eliminated when the value of inductance varies.In order to achieve decoupling,the multi-dimensional sliding mode surface was selected to design ESMO for estimating the disturbance.While ESMO has chattering and the convergence speed was slow,the Hurwitz exponential reaching law was designed to improve ESMO to achieve current decoupling to a certain extent.The theoretical analysis proved that IESMO-CDDC can ensure the stability of the system and improve the robustness of the system.Through simulation comparison,the validity of the designed scheme was verified.Finally,in view of the disturbance of parameter changes that made IESMO-CDDC unable to be completely decoupled,an IESMO-CDDC method based on active disturbance rejection was designed.The integral sliding mode surface was selected to design the state error feedback control law in active disturbance rejection controller for ensuring the robustness of the system.Then,aiming at the disturbance caused by parameters variation,an extended state observer with continuous gains was designed.Due to the peak phenomenon of extended state observer with continuous gains,an extended state observer with variable continuous gains was designed to observe the disturbance of the parameter change,and then further decoupling effect of the d-q axis current was realized.The theoretical analysis proved that the IESMO-CDDC method based on active disturbance rejection can ensure the stability of the system.Through system simulation comparison,it was verified that the proposed method can further improve the decoupling effect and improve the robustness of system.