Position Control For A Permanent Magnet Linear Synchronous Motor Based On Disturbance Observer

Linear feeding system cancels all the middle transmission links from the motor to the worktable and makes the transmission links of feeding system zero. "Zero-transmission" of feeding system has been obtained, which makes linear servo motor drive system apply widely in many aspects. But during the period that linear system moving as to all kinds of interior and exterior reasons, its parameter and exterior disturbance have large uncertainty. Owing to this uncertainty, control quality of system may decrease badly. In allusion to influence of mover mass variety disturbance, outside disturbance and friction disturbance under low speed to servo system, some studies have been done and relevant schemes has been put forward.At first, based on reading many domestic and international relative literatures the improvements of linear feeding system are overviewed; the domestic and international research status of permanent magnet linear synchronous motor (PMLSM) feeding system robust control are outlined; the control schemes of PMLSM servo system are described. Secondly, based on the analyzing the basic structure and work principle of PMLSM, the vector control principle is introduced; the mathematic model of PMLSM is established; the influences of main disturbance factors of linear motor servo control system to the dynamic qualities are analyzed simply. In allusion to disturbance, a disturbance observer based on inverse dynamic equations of controlled systems is designed, the thrust is feedforward by the disturbance observer to resist disturbance outside and improve the robustness of system. In allusion to mover mass variety disturbance, methods of disperse model reference adapt identification and self-tuning of position controller parameters are adopted, the current value of identifying mover mass is sent to the position controller and disturbance observer to amend parameters in the controller and update the mover mass parameter in disturbance observer. The system shows good dynamic and static performance when mover mass changes through this control strategy. In allusion to nonlinear friction which can decrease servo system track performance, the model reference adaptive system based on Coulomb friction is designed to compensation the friction on-line. The designed model reference adaptive parameter identifier is combined with the adaptive friction compensation system, the mover mass identified by the parameter identifier is used to update mover mass in the model reference adaptive control system based on Coulomb friction.Simulation results show that the position tracking precision of system and robustness are improved through the control scheme proposed in this paper, which could meet the requirement for high-precision numerical control machines.