Research On Torque Ripple Minimization Techniques For Brushless DC Motor

Brushless DC Motor has got more and more attention due to it's high power density and simple control method in recent years. The torque ripple problem of brushless DC motor, however, limits the application of servo control systems which requires high accuracy position and speed control. Therefor,studying the method of reducing torque ripple utilized in brushless DC motor is becoming a hot spot of research, this paper mainly studies about the torque ripple reduction of brushless DC motor in the process of commutation.First, this paper analyzes the basic structure and operating principle of brushless DC motor. Besides, hall sensor configuration rules is given under the control of positive inversion. Then using electromagnetic field finite element analysis software establish the basic model of brushless DC motor based on the actual basic dimensions and parameters.Transient performance of the motor under no-load and load were simulated in both cases by using 2D finite element module of the software. The above provides a theoretical basis and simulation platform for torque ripple restraint strategy proposed in this paper. Second, this paper analyzes the causes of the commutation torque ripple of brushless DC motor. Then this paper proposes delayed conduction control method of overlapping commutation for the Brushless DC motor under rated load and steady-state operating conditions. For the overlapping commutation angle is difficult to determine, this paper calculates the optimal overlapping commutation angle of the given motor by setting the external circuit of the 2D finite element model. Thus, the issue that overlapping commutation angle can not be determined is solved. Subsequently, the inhibitory effect of the torque ripple is verified by the use of the derived optimal overlapping commutation angle combined with double-loop control scheme. In order to verify the proposed theory, the total hardware platform is designed, taking FPGA as the digital controller while IGBT as the core of inverter circuit.The software is designed with the modularized program method based on the model of hardware platform. By using luxuriant logic cells of FPGA and combined with the characteristics of signal detection and motor control, the hardware logic circuits of all motor control modules including PWM module, commutation module, filter module and speed measurement imodule are constructed in Verilog HDL. Each function module is simulated by Quartus ?. Finally, the partial commissioning experiments are completed and the given experimental waveforms are analyzed through the approach of joint commissioning of hardware and software of the control system after finished debugging of each hardware circuit module.This Paper represent the research on reducing commutation torque ripple of brushless DC motor with rated load under the steady state operation condition. Meanwhile,it also illustrate the deficiencies on the control method of reducing torque ripple, and point out the direction for further research work.