Optimization Design Of Controllers In PMLSM Servo System

Machine tool with permanent magnet linear synchronous motor (PMLSM) is a directdrive feed mode, which has many advantages including large thrust, high acceleration and fastfeed rate. However, time-varying system parameters and load disturbance factors restrict theposition accuracy and dynamic performance. This thesis was supported by Doctoral Programof Higher Education of Special Fund (20112102110002), National Natural Science Foundationof China (51075281) and Liaoning Province University Innovation Team (LT2010081). inorder to meet the high precision control of AC linear servo system. This thesis optimizedposition loop, speed loop and current loop of permanent magnet linear servo system.First of all, some disturbances and control strategies were studied, the mathematicalmodel of PMLSM servo control system was built based on Matlab/simulink.this Thesis alsoanalyzed the position, speed and current loops in PI linear regulators, which cannot meet thehigh precision control requirements of servo system and discussed major problems and theadvantages of sliding mode control(SMC).Secondly, the current loop plays a decisive role to system performance as an inner loop ofPMLSM servo system. The thesis proposed sliding mode control to optimize the current loop,which improved the tracking performance of current significantly. In order to decreaseinfluence on varying load thrust and suppress the chattering of the SMC system,a method ofcurrent sliding control with sliding mode observer of load thrust was put forward. The loadthrust observer observed changes of load thrust in real time and was equaled to correspondingcurrent input of the system.Finally, to solve the speed limit problem of the conventional sliding mode control of thepermanent magnet linear feed servo system, a new integrated control method was proposed forposition and speed control, the controller achieved the position and speed limist, the dynmicperformances of the system were improved significantly, which is favorable to achieve digitalcontrol. Simulation results show that the integrated control strategy for position and speed iseffective.