Research On The Torque Pulsation Of The Permanent Magnet Brushless Direct Current Motor

The permanent magnet brushless DC motor is a DC motor using electronic commutation in place of mechanical commutation in fact, so it has excellent characteristics of DC motors, for example good start and timing performance. It simplifies the motor's structure and overcomes the friction disadvantages of ordinary DC motor because it doesn't use mechanical commutation. It is extensively used in aviations , robots , digital machine tool and so on. But it has the disadvantages of torque pulsation, it can't achieve accurate position and speed of higher performance.From the basic operation principles of the permanent magnet brushless DC motor, this paper analyses the producing reasons of torque pulsation and establishes the mathematical model. In course of the simulation of mathematical model, this paper analyses and calculates quantitatively the key variables of torque pulsation, that is electromotive force wave and current wave, and tables a proposal through controlling the angle of PWM supply voltage, at the same time the results are given.Because the permanent magnet brushless DC motor has a series of advantages, it suits higher performance alternating servo system. But how to reduce the torque pulsation in a wide timing range is the main discussing issue of alternating servo system. This paper simulates and analyses the torque pulsation because of the modulation frequency and speed variation under ambipolar pulse width modulation,at the same time the results are given.