| In order to solve the problem of oil resource depletion and environmental pollution preferably,electric vehicles emerge at a historic moment.The motor and its control strategy are playing more important roles in electric vehicle.The control strategy of the motor had been studied of international and domestic academics for a long time.Brushless DC motor has the advantages of high efficiency,low consumption and simple structure.Because of these,it has been widely used in more and more fields.Therefore,in this paper a control system of electric vehicle based on direct torque control of brushless DC motor is designed.In addition,the simulation system about the performance of electric vehicle at low speed is analied.First of all,based on the structure of brushless DC motor,the classification,working principle and characteristics of brushless DC motor are introduced detailedly.Secondly,brushless DC motor has a large torque ripple problem in the running at low speed.Aimed at this problem,the control methods used in brushless DC motor are analied and contrasted.On the basis of analysis of the principle of direct torque contol,the simulation model of brushless DC motor direct torque control system is bulided by Matlab/Simulink.Besides,each of simulation module of the simulation model is introduced in detail and obtain the simulation wavefore figures.Compared with the simulation waveform figures in vector control,a conclusion is drawn that direct torque control not only has good dynamic response but also can restrain the torque ripple effiectively.Finally,based on electric vehicle parameters and power indicators,electric vehicle’s drive system and drive motor parameters are designed and selected.Furthermore,combined with the car equation,electric vehicle model is established.And we simulate the running state of electric vehicle at low speed,the simulation results confirmed that the simulation system can well meet the requirements of the electric vehicle when it is running. |
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