The Second Order Sliding Mode Control Of Permanent-magnet Linear Synchronous Motor

Permanent magnet AC servo technique has grown rapidly since 1980's, the applications of permanent-magnet linear synchronous motor become more and more complex and diversified, many higher requests are offered, the servo systems are hoped to have the good performances of speed-tracking and against disturbance. In that variable structure sliding mode control theory has some advantages, such as high response, good robustness and easy realization, this theory has been applied gradually in the electric drive control area. But there is a drawback—chattering in the engineering application, i.e. high frequency oscillation is caused by switching control. The reason is that high frequency switch is impossible for controller and implement machine, and system has steady error at steady state, even system elements are destroyed by high frequency. In order to overcome the blight caused by parameter variety and disturbance outside, and realized high performance and strong robustness of AC servo system, second sliding mode control theory is used based on the comprehensively deep research on the PMLSM mathematics model and control theory in this thesis.Traditional sliding mode is introduced firstly in this thesis, then higher sliding mode theory is expatiated, the reason of weakening chattering is introduced particularly. Attach most importance to the second sliding mode control theory, the keystone and some algorithms is introduced, twisting algorithm and sup-twisting algorithm are separately researched in allusion to continues and discrete PMLSM servo system. The results of simulation show that second sliding mode reserve all of advantages of traditional sliding mode, and attenuates chattering availably.In that PMLSM servo system has characteristic of multi time scales, the singular perturbation method and second sliding mode theory are combined in order to solve nonlinear of system model and the coupling between the variables. The singular perturbation method is applied to decouple the permanent magnet linear synchronous motor into subsystems with different time scales, then the second order sliding mode control algorithm—twisting algorithm is applied to realize the control of each subsystem, the composite control of the permanent magnet linear synchronous motor is composed of control of each subsystem. The difficulty of controller designing is reduced by this method. The singular perturbation method has quasi steady state method and block diagonalized method aim at big and small discrepancy of time scales of subsystems. Two different PMLSM is used as control plant in order to validate two methods validity in this thesis. The results of simulation show that this strategy has very good speed-tracking performance, and has very strong robustness against load disturbances, parameters varieties and the other uncertainties.