Research And Optimization Of Regenerative Braking System For Parallel Hydraulic Hybrid Vehicle

A large portion of the energy is consumed in the braking process when the vehicle is on the frequently start and stop urban driving cycle.The hydraulic hybrid system that has the advantages of simple structure,high power density and high efficiency of energy recovery can fully recover the kinetic energy consumed in the braking process,and the energy is stored in the accumulator.When the vehicle starting or accelerating the energy stored is released,so as to reach the purpose of energy conservation and emissions reduction.In this paper,a parallel hydraulic hybrid power system(PHHS)is selected as the research object,and the process of hydraulic regenerative braking is studied with the purpose of improving energy recovery the efficiency of system.This article does researches on PHHS as follows:(1)The advantages and disadvantages of the layout of three kinds of hydraulic hybrid vehicles are compared and analyzed,and the parallel structure is selected as the subject of the study.(2)According to the mathematical models of main components of liquid mixing system,the bench simulation model of liquid mixing system is built in Simulink,and the test bench of the system is built.The simulation results are basically consistent with the experimental results.The experimental and simulation studies show that the braking characteristics of the PHHS are related to the accumulator pressure and the hydraulic pump displacement.The braking torque provided by the PHHS is linear with the accumulator pressure and the hydraulic pump discharge respectively.(3)The ADVISOR platform was redeveloped,and the hydraulic regenerative braking system was added to the traditional vehicle model.The simulation results i ndicate that when the vehicle is braking,the hydraulic regenerative braking system restores energy and accumulator pressure increases;when the vehicle is driven,the hydraulic regenerative braking system drives the car forward with the accumulator pressure decreases.The electric vehicle with the hydraulic regenerative braking system increases the energy efficiency and the endurance of the vehicle is increased.(4)In order to improve the energy recovery efficiency of hydraulic regenerative braking system,a dynamic programming algorithm was adopted,and the optimal control schemes of the displacement and transmission ratio under the 1015 urban drive cycles and UDDS cycle were obtained.The simulation results show that the energy recovery efficiency was significantly increased after optimization.The optimization scheme based on the dynamic programming algorithm improves the energy recovery efficiency of PHHS.In this paper,a parallel hydraulic hybrid vehicle is studied with experiment and simulation,and the influencing factors of the braking process is analyzed.The DP algorithm is used to optimize the system,which improves the energy recovery efficiency of the system.