Sliding Mode Control of Permanent Magnet Synchronous Motor Based on Load Observer
|Course||Control Theory and Control Engineering|
|Keywords||Permanent Magnet Synchronous Motor (PMSM) Sliding-mode Variable Structure Control(SMC) Load Observer Chattering Fuzzy Control Fuzzy Sliding Mode Control(FSMC)|
Permanent Magnet Synchronous Motor (PMSM) has the advantages of smallvolume, light in weight, small torque ripple, simplicity in torque control, steady rotatespeed, fast dynamical speed response and strong overload ability, so it is widely usedin AC speed regulating system. PMSM is a multi-variable, nonlinear and strongcoupling system, the conventional PID controller is easily subjected to the influenceof motor parameter variation and load disturbance. So it is difficult to meet the speedand torque control requirements of high accuracy circumstances when load variationis big.Sliding-mode variable structure control which sliding mode can be designed isinsensitive to system parameters change and load disturbance. And it has theadvantages of good robustness, quick response, easy realization and so on. So it’shopeful to achieve a control strategy of high quality by applying sliding modecontrol(SMC) to the PMSM speed control system. Thus, this paper mainly researchesthe application of SMC to PMSM speed control system.Firstly, based on the detailed analysis on the mathematical model of PMSM, thispaper gives the linear decoupling state equation of PMSM in the d-q coordinates bycombining with Vector Control technique. Then the simulation model of PMSM speedcontrol system is built with Matlab/SIMULINK by using rotor position orientedcontrol scheme of Vector control.Secondly, based on the analysis of SMC theory, characteristics, the causes ofchattering and decreased methods, a general sliding mode controller is adopted to thespeed control of PMSM in this paper. Then the control effect of this controller and theinfluence of controller parameter on system performance are analyzed by thesimulation.Thirdly, based on the general sliding mode controller, this paper proposes anmodified sliding mode controller, which is the time-varying switch gain sliding modecontroller based on Load Observer. The simulation results show that the modifiedsliding mode controller can obviously decrease chattering, and has good robustness toload disturbance and system parameters change. At last, with the combination of the merits of SMC and fuzzy control, this paperdesigns the sliding mode controller based on fuzzy self-adjusting of switch gain forPMSM speed control, and accomplishes S-function realization of the controller. Forthis controller, the switch gain of SMC is adjusted in real time by using fuzzy logic,so it not only can fully exert the characteristics of SMC which are insensitive toparameters change and disturbance, but also has the ability of fuzzy self-adjusting,thereby the aim of decreasing chattering can be achieved. The simulation results showthat this controller has the capability of chattering-decreasing, strong robustness toload disturbance and system parameters change. It attains expected control effect.