| The brushless DC motor (BLDCM) is a newly developed type of motor,which replaces the mechanical commutation by the electric commutation. It has the merits of both the good speed control performance of the Brush DC motor and the simple structure of the asynchronous motor. With the research development on BLDCM and its control system, the BLDCM has been widely applied in industry especially in electric vehicle (EV) field in which the BLDCM has become the preferred motor. The research on motor drive and regenerative brake in developing electric vehicle is so important that this paper has studied the drive and regenerative brake of the BLDCM and the work has been done as the following:Firstly, the operating principle of the BLDCM has been discussed and the mathematic models on drive and regenerative brake states of the BLDCM were analyzed. The back EMF of the BLDCM is trapezoidal waveform with 120°platform width.Secondly, the hardware circuits of the system has been designed which includes power inversion circuit,driving and protecting circuit of the IGBT, current limited and chopper circuit used in regenerative brake,the electrifying delay circuit, DSP peripheral circuit, current detecting circuit and DC voltage detecting circuit.Lastly, the control method of both drive and regenerative brake has been studied. And the method of controlling the regenerative current was also be studied. The software is designed which based on that including the program of the commutation, the program of sampling current and voltage, the program of regulating the PWM wave, the program of calculating rotate speed, the program of regulating the current and rotate speed in close loop, the program of controlling the regenerative current according to the charge of the battery.The result of the experiment shows that the BLDCM has an excellent dynamic and static performance and the effect of the regenerative brake is notable. The regenerative current was also controlled according to the charge state of the battery, so the motor works well on the regenerative brake state. |
