| The vigorous development of the traditional automotive industry has exacerbated environmental pollution and global energy shortage crises.Electric vehicles,relying on their advantages in environmental protection and energy conservation,are currently one of the research hotspots in the automotive field.However,due to limitations in technologies such as power batteries,the driving range has become a bottleneck restricting the development of electric vehicles.Electric vehicle braking energy recovery,as a key technology to improve the energy economy of electric vehicles,can effectively increase the range.Therefore,this article relies on the National Natural Science Foundation of China’s "Research on the Coordinated Coupling Control Mechanism of Distributed Drive Electric Vehicle Composite Braking Based on Driving Intention and Vehicle Speed Prediction"(project number: 52172362)to study the torque distribution strategy of pure electric vehicles during the braking energy recovery process.The main research work is reflected in:Firstly,based on the working principle of the braking energy recovery system,the energy flow of electric vehicles during the braking process is analyzed,and an evaluation index for the braking energy recovery performance is proposed.A comprehensive evaluation method is proposed based on the entropy method.Analyzed the influencing factors of braking energy recovery performance,and elaborated on the braking force distribution method of typical braking energy recovery control strategies.Secondly,based on the ideal braking force distribution curve,the Economic Commission for Europe automotive regulation curve,and the front and rear braking force distribution curve under the critical front wheel lock state,a safety zone for front and rear braking force distribution and a strategy curve for front and rear braking force distribution are proposed and optimized.Then,based on the distribution strategy of front and rear braking forces,a regenerative braking force distribution strategy for the drive shaft motor was proposed based on fuzzy logic control,and the regenerative braking force was constrained based on the external characteristics of the motor and battery charging power.Then,aiming at the problem that the membership function of the fuzzy controller depends on subjective experience and its performance cannot reach the optimal level,a genetic Firefly algorithm is proposed to optimize the fuzzy controller.Selecting the characteristic parameters of the membership function of the fuzzy controller as the optimization variable,with the goal of maximizing braking energy recovery,a hybrid optimization algorithm is designed to find the optimal solution in the feasible domain.Based on AVL＿Cruise built a pure electric vehicle model,and based on Simulink,built the motor braking force distribution strategy model proposed in this paper based on fuzzy logic control,and achieved joint simulation of the two.Finally,the effectiveness of the improved front and rear braking force distribution strategy and fuzzy controller control rules proposed in this paper was verified under CLTC-P and conventional braking conditions,respectively.Selecting NEDC,CLTC-P,and WLTC cycle conditions for control strategy comparison simulation experiments,the results show that the motor braking force distribution strategy based on fuzzy control in this paper has significantly improved the braking energy recovery performance compared to the parallel distribution strategy;The braking energy recovery performance of the fuzzy control strategy optimized by the genetic Firefly algorithm is further improved.While ensuring the braking safety,its braking energy recovery performance is close to the maximum energy recovery control strategy. |
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