| In recent years,fog and haze weather has seriously affected people’s physical and mental health.According to relevant research the data shows that the using of fossil fuels to provide power to the traditional car is one of the culprits caused by fog and haze.So the development of low pollution,low energy consumption of electric vehicles around the world is imminent.Despite the rapid development of electric vehicles in recent years,however,it is difficult to solve the bottleneck problem of short range and low energy density of battery.In this thesis,by optimizing the control strategy of regenerative braking,the power line is customized,and the energy can be recovered efficiently when the vehicle is braked,so as to improve the mileage of the vehicle.Firstly,the thesis introduces the current situation of the development of electric vehicles,analyzes the driving motor used in various electric vehicles,and describes the significance of regenerative braking control strategy to improve the efficiency of electric vehicles.Secondly,the thesis introduces the basic principle of brushless direct current motor and regenerative braking circuit,in the mathematical model and the regenerative braking of the full bridge and half bridge modulation mode in every state of the comprehensive analysis and comparison.Comparative analysis on the basis of a pulse width modulation cycle of the back electromotive force,feedback braking current,duty cycle and other parameters of the relationship between the main influencing factors,the efficiency of regenerative braking for the duty ratio and the counter electromotive force.Then,in the comparison of different front and rear wheel braking force distribution strategy,in order to improve the efficiency of regenerative braking,to meet existing industry standard requirements of the premise,put forward the maximum driving wheel braking force curve,as much as possible in order to recover braking energy.Finally,in order to make the vehicle braking energy feedback system in strict accordance with the maximum driving wheel braking force curve in the operation,in-depth analysis of the braking process,determine the design using fuzzy control theory to complete the energy feedback system,and built the largest driving wheel braking energy recovery system based on fuzzy controller,this system can guarantee in the premise of safety braking,let the car recovery more braking energy.The fuzzy controller is used to optimize the dynamic distribution of the feedback system,which can effectively improve the overall performance of the system and the efficiency of energy recovery.The fuzzy control toolbox in the design of a fuzzy controller in Matlab,established on the basis of the mathematical simulation model of brushless direct current motor regenerative braking,the simulation results prove that the control strategy used in this paper and the fuzzy controller can achieve better effect and energy feedback braking effect. |
