Research On Control Of Rear-drive Electric Light Truck Braking Energy Recovery System

With the increasingly serious environmental pollution and the rapid development of new energy vehicle technology in China,pure electric vehicles have become an important developing direction of energy-saving and environment-friendly vehicles in the future.Compared with traditional fuel vehicles,the driving motor of pure electric vehicles can participate in braking to recover braking energy from the kinetic energy consumed in the process of braking,which is an important means to improve the energy utilization rate and driving distance of vehicles.In this paper,a rear-drive pure electric light truck is studied.The research focuses on the hierarchical control design of the regenerative braking system and the simulation and bench test are carried out.The main research contents of this paper are as follows:Firstly,the hardware solution of the regenerative braking system based on electronic pneumatic braking axle valve and electronic foot valve is proposed and the principle of their coordination work is introduced in detail.Based on the analysis of hardware structure,the hierarchical control scheme of regenerative braking system is designed.Secondly,in order to improve the response hysteresis,oscillation and imprecision of the pneumatic braking system,the operating modes of the electronic pneumatic braking axle valve is analyzed and its structure is simplified.The coupling dynamic model of "electric-magnetic-pneumatic-mechanical" based on high speed on-off solenoid valves and pneumatic braking circuit is established.Simulation analysis and open-loop test are carried out to obtain the pneumatic system characteristics.According to the characteristics,a combined control method based on PID control and fuzzy control is proposed to effectively improve the control accuracy and response speed of pneumatic braking force during regenerative braking process.Moreover,the required models including vehicle dynamics model is build up.In view of the regenerative braking system optimization contradictory characteristics of different needs,three different braking force distribution strategies are designed: strategy of maximum braking energy recovery optimization,strategy of great braking performance optimization and strategy of comprehensive optimization,which consider the influence of the drive motor,battery and other components characteristics and braking safety in the meantime.Based on the driver's braking intention,the classification recognition for three basic intentions are proposed: emergency braking intention and secondary braking intention and smooth braking intention.Combined with braking intentions,the vehicle can switche different braking force distribution strategies.The feasibility and effectiveness of the braking strategies are verified by software simulation analysis of indicators.Finally,dSPACE hardware is used to build the semi-physical test bench of electronic pneumatic braking system.Based on three different regenrative braking control strategies,the rapid control prototype tests are carried out to analyze braking characteristics,energy recovery efficiency and the contribution rate of driving distance of different regenrative braking control strategies under different typical braking conditions and cycle conditions,which verify the feasibility and effectiveness of the strategies.