Research Of The Direct Torque Control And Variable Structure Slide Mode In The Permanent Magnet Synchronous Motor

Permanent Magnet Synchronous Motor (PMSM) has the advantages of high magnet density,small torque pulse, big torque-inertia, high efficiency, simple construct and so on. PMSM hasbeen applied to the occasions that requires high precision of control and high reliability far andwide, such as avigation, numerical control machine tool, radar and some military weaponsfollow systems, robot and so on. In addition, it plays an important part in Ac motors in moderntimes.Firstly, the organization and characteristic of PMSM is introduced, and the mathematicsmodels in various coordinates are set up. Then the principle of PMSM DTC is discussed deeply.And the action of voltage space vector on flux linkage and torque is analyzed. The figure ofprinciple structure is proposed.According to the principle and structure of PMSM DTC, the thesis set up the sub-modelsof PMSM DTC system by MatLab/SimuLink. The simulation of opened-loop and closed-loopare carried out. And the simulation results show the method is effective in virtue of thecharacteristic of the quickly dynamics response of DTC technology.Due to the large torque ripple of induction motor in DTC system, especially in low speed,this thesis introduced a sliding theory. Variable structure control system with sliding mode whichcan be designed is insensitive to system parameters change and load disturbance, and has theadvantages of good robustness, quick response and so on. Accordingly, it's hopeful to design acontrol strategy of high quality by applying sliding mode control to the control of PMSM servosystem.Based on the analysis of sliding mode control theory, characteristics, the causes ofchattering and decreased methods, a sliding mode controller is adopted to the control of PMSM in this paper. Then the simulation of the sliding mode controller is done and through thesimulation curves, the control effect of this controller are analysed.