| Permanent magnet synchronous motor (PMSM) has a lot of advantages, such assmall volume, light weight, high power density and simple structure. With thedevelopment of the permanent magnet material NdFeB`s performance and powerelectronics, it will have wide application prospects by combining high-performancePMSM with modern control methods to develop high-performance speed controlsystems. In addition, closed loop speed or position control systems with mechanicalsensors have some drawbacks, like increasing system volume and cost, reducingsystem reliability and so on. For these reasons, this article aims to improve theperformance of traditional PMSM direct torque control (DTC) system and to realizesensorless control.Firstly, this paper takes one PI regulator and the space vector modulation(SVPWM) method to replace the bang-bang controller and the fixed voltage spacevector method of the conventional DTC system. Based on the above-mentionedimprovements, this paper uses a sliding mode speed observer to realize sensorlesscontrol.At first, this paper simply introduces the theory. Then with the help of MATLAB /Simulink simulation tool, the methods this article takes are verified. The simulationresults show that the improved DTC method can significantly reduce the fluctuationof motor torque, flux linkage and currents. And the results also show that the controlsystem'performance is enhanced. Besides, they also verify the feasibility of thesensorless control based on sliding mode speed observer. These theoretical studiesprovide the reference for further experimental researches. Then this articleexperiments the methods mentioned above on one transducer which uses TI'sTMS320F2812 digital signal processor (DSP) as the control core, the IR's IRF450MOSFET as the converter switches. The experiments preliminary verify that themethod this paper takes, which is DTC of PMSM without speed sensors based onsliding mode variable structure (VSS) has good dynamic and static performance, andthe method is feasible.
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