Research On Torque Ripple Suppression And Control Method Of Brushless DC Motor Based On DSP

Brushless DC motors are widely used in fans, pumps and air-conditioning systems, whichare all the situations requiring low energy consumption and low noise. Improving the motorcontrol methods to enhance the efficiency of the brushless DC motor, reduce the energyconsumption, suppress torque ripple and reduce noise is a hot research point of brushless DCmotor control field. Brushless DC motor has two control methods, square-wave control methodand sine-wave control method. But the brushless DC motors driven by square-wave have ashortcoming that is big torque ripples and noise, so its applications are greatly limited. Drivingby sine-wave can effectively reduces the torque ripples of brushless DC motors, but usually,when we want to drive a brushless DC motor by sine-wave, we need to increase the system’shardware, and increase the cost of the system. Therefore, with the same hardware conditions asdriving by square-wave, realizing that driving brushless DC motor by sine-wave has greatpractical significance.At present, the most widely used sine-wave brushless DC motor control method is theSPWM control method. However, the inverter’s DC voltage utilization rate is rather low, theswitching loss of the inverter is big, and the harmonic content in the output voltage of theinverter is big. Because the SPWM control method has the above shortcomings, on the basis ofline-voltage control method, this paper proposed a new, named two-phase saddle-shaped PWMcontrol method to drive the brushless DC motor. This paper simulated the two-phase saddle-shaped PWM control method by MATLAB, the simulation results show that the two-phasesaddle-shaped PWM control method can enhance the DC voltage utilization, reduce theswitching losses. In addition, The relevant algorithms of the two-phase saddle-shaped PWMcontrol method, including the square-wave starting control algorithm, two-phase saddle-shapedPWM calculation methods and leading angle adjustment are introduced.The sine-wave brushless DC motor torque ripple suppression is another focus of this paper. This paper analyzed the suppression methods of the torque ripples from two aspects: improve themotor body and optimize the control method. Specially, this paper analyzed the suppressionmethods of the torque ripple caused by position estimation error. Two position estimationmethods based on Hall position signals, i.e. the zero-order and first-order position estimationalgorithms are introduced, and the two position estimation algorithms’ performance arecompared by MATLAB simulation. In order to improve the fist-order position estimationalgorithm’s performance, this paper proposed a first-order position estimation algorithm optimalmethod, which is based on step-by-step speed PI control method. This optimal method is verifiedby simulation that it can reduce the position error, torque ripples and make the motor accelerateor decelerate more smoothly.At last, this paper designed the hardware and software solutions for a brushless DC motor,which is based on TMS320F2812DSP. The experimental results verified the two-phasesaddle-shaped PWM control method based on Hall position sensors is effective and feasible, andunder the step by step speed PI control, the estimation error of first-order position estimationalgorithm is more small, which can make the motor run more smoothly.