Research On New Direct Torque Control Of Brushless DC Motor Based On Sliding Mode Variable Structure

In order to improve the control performance of the permanent magnet brushless DC motor,the optimization of Brushless DC motor control strategy is studied in this paper.The basic theory research questions include:(1)main working principle and mathematical model of brushless motor;(2)study and analyze the direct torque control method of Brushless DC motor;(3)research and Analysis on the given way of stator flux amplitude in direct torque control;(4)using sliding mode variable structure instead of PI control to realize a new scheme of torque given.Details are as follows:1.The basic characteristics and development trend of BLDCM are briefly introduced,and the characteristics and development of BLDCM direct torque control strategy are expounded.The main advanced control algorithms of BLDCM are introduced and compared in detail.2.The basic principle of permanent magnet brushless motor is analyzed in this paper,and a mathematical model based on idealized motor is given on the basis of this.What’s more,this paper analyzes the most outstanding pulsating problem of brushless motor and several popular control systems,which provides evidence for the design of brushless motor control system.3.The basic idea of direct torque control(DTC)and its application in brushless motor are introduced.The basic principle and several main modules of the brushless motor direct torque control system are analyzed and studied.On this basis,the modeling simulation and the result analysis are carried out.The experimental results prove the excellent dynamic and static performance of Brushless DC motor direct torque control system,but there is still room for improvement in torque ripple,robustness and other static and dynamic performances.4.A new stator flux given method is proposed,and the comparison analysis and experimental modeling analysis are carried out with the traditional flux given method.The comparative study shows that the BLDCM DTC based on the new stator flux given method has obvious advantages on torque ripple suppression and dynamic response performance.In addition,the trajectory of the armature flux under the new flux given method can dynamically reflect the change of torque,which is beneficial to the analysis of the experimental results of the system.5.A sliding mode variable structure is used to replace the conventional PI control for a torque given module in BLDCM-DTC.The sliding mode control based on the traditional linear sliding mode surface and the exponential reaching rate is analyzed.Based on that,a sliding mode control method based on nonlinear integral sliding surface and hybrid reaching rate is designed,and the approaching time and chattering are analyzed.The simulation results show that the proposed sliding mode variable torque control scheme is superior to the traditional PI control in the whole dynamic and static performance.