Research On Sliding-Mode Variable Structure Control For PMSM Servo Systems

Permanent Magnet Synchronous Motor (PMSM) has the advantages of high magnet density, small torque pulse, big torque-inertia ratio, high efficiency, simple construct and so on. PMSM has been applied to the occasions that requires high precision of control and high reliability far and wide, such as avigation, numerical control machine tool, radar and some military weapons follow systems, robot and so on. In addition, it plays an important part in Ac motors in modern times.Sliding-mode variable structure control which sliding mode can be designed is insensitive to system parameters change and load disturbance, and has the advantages of good robustness, quick response, easy realization and so on. Accordingly, it's hopeful to design a control strategy of high quality by applying sliding mode control (SMC) to the control of PMSM servo system. Thus, this paper mainly researches the application of SMC to PMSM control.Firstly, based on the detailed analysis on the mathematical model of PMSM, this paper gives the linear decoupling state equation of PMSM in the d - q coordinates by combining with Vector Control technique. Then the simulink model of PMSM servo system is built with Matlab/Simulink by using rotor position oriented control scheme of Vector control.Secondly, based on the analysis of SMC theory, characteristics, the causes of chattering and decreased methods, a general sliding mode controller is adopted to the speed control of PMSM in this paper. Then the simulation of the general sliding mode controller is done and through the simulation curves, the control effect of this controller and the influence of controller parameter on system performance are analysed.Thirdly, based on the general sliding mode controller, this paper proposes an modified sliding mode controller, which is the sliding mode speed controller based on subsection integral switch gain. The simulation results show that the modified sliding mode controller can obviously decrease chattering, and has good robustness to load disturbance and system parameters change.At last, with the combination of the merits of SMC and fuzzy control, this paper designs the sliding mode controller based on fuzzy self-adjusting of switch gain for PMSM speed control, and accomplishes S-function realization of this controller algorithm. For this 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 to parameters change and disturbance, but also has the ability of fuzzy self-adjusting, thereby the aim of decreasing chattering can be achieved. Thesimulation results show that this controller can effectively decrease chattering, has strong robustness to load disturbance and system parameters change, and attains expected control effect.