Analysis On Energy-saving Mechanism Of Hydraulic Hybrid Vehicle Based On Compound Accumulator

With the rapid development of the world economy,the environmental pollution and energy shortage are becoming more and more prominent,which makes energy-saving and new energy vehicles become the focus of international automobile industry competition.The short battery life of electric vehicles,long charging time and imperfect charging facilities have always been the bottleneck restricting the popularization and development of electric vehicles.While hybrid electric vehicles take into account the advantages of traditional internal combustion engine vehicles and electric vehicles,can achieve the purpose of energy saving and emission reduction,Hydraulic hybrid electric vehicles have the characteristics of high power density,can fully recover the braking energy of vehicles,and is suitable for frequent start-stop vehicles.Aiming at the problem that the energy recovery and braking performance of traditional parallel hydraulic hybrid vehicle with single accumulator can not be taken into account,a new configuration of parallel hydraulic hybrid vehicle with compound accumulator is proposed in this paper.The main research is as follows:(1)Analyzed the working characteristics of the traditional hydraulic regenerative braking system and researched a new configuration of the hydraulic hybrid system based on composite accumulator.The key components of the hydraulic regenerative braking system are matched and selected.(2)Analyzed the working mode of the hydraulic hybrid vehicle and established the logic threshold driving control strategy based on the optimal working range of the engine.Combined with the characteristics of energy recovery of hydraulic regenerative braking system,the parallel composite braking regenerative braking control strategy based on ECE regulation is proposed.(3)The engine model,vehicle dynamics model,transmission system model,transmission model,hydraulic pump/motor model,composite accumulator model and driver model modified by PID are established for parallel hydraulic hybrid vehicle based on composite accumulator,which lays a foundation for identification of control strategy and simulation analysis.(4)The parallel hydraulic hybrid vehicle regenerative braking system model and vehicle model based on composite accumulator are established.Through the simulation analysis of braking process,the influence of accumulator parameters on energy recoveryand braking performance under the same initial conditions is proved.The improved vehicle performance and control strategy are simulated and analyzed under the improved NEDC cycle conditions,and the energy-saving mechanism of the hydraulic hybrid vehicle based on composite accumulator is obtained.(5)Built the experimental platform of hydraulic hybrid power system and designed the experimental method of parallel hydraulic hybrid vehicle.For the braking process,the braking energy recovery experiment of the parallel hydraulic hybrid power system under typical braking conditions was carried out,and the control effect of the strategy was verified through the experiment under NEDC cycle conditions.