Research And Design Of Direct Torque Control System For Brushless DC Motor

Brushless DC motor is widely used, it is easy to control and high reliability.Direct torque control (DTC) is simple and fast , and has good dynamic and static performance.At present it has been successfully applied in asynchronous motor and permanent magnet synchronous motor. The main purpose of this paper is to apply a DTC method based on Hall signal to the brushless DC motor control system,which is used to reduce the torque ripple and improve the control performance of brushless DC motor on the basis of simplifying the structure of the control system.Based on the principle and characteristics of DTC,an improved DTC scheme based on Holzer signal is adopted on the detailed analysis of the traditional DTC method of Brushless DC motor.On the basis of the original system,the scheme has made two improvements: first, according to the stator flux linkage amplitude and the electromagnetic torque value between the one-to-one relationship,the stator flux linkage control loop is omitted in the two-phase conduction which can simplify the control system; second, an electromagnetic torque measurement method based on Holzer signal is proposed, which can observe the electromagnetic torque only by the bus current with the phase current and back EMF logic values.In order to verify the feasibility , the simulation model of Brushless DC motor DTC system based on Holzer signal is established by MATLAB/Simulink.In order to ensure the rationality of the experiment, the double closed loop control and the DTC simulation model are respectively established for comparative analysis.Finally,a DTC software and hardware system of Brushless DC motor based on TMS320F2812 is designed, and as a platform for a preliminary experiment.