| With the development of Chinese automobile industry,the number of domestic automobiles has increased year by year,which has brought about major problems such as massive consumption of petroleum resources and environmental pollution.In response to these problems,the state vigorously promotes the development of new energy vehicles,and related researches have become a hot spot in the industry.Relying on the national key research and development program "development of high performance pure electric sport utility vehicle(SUV)",this paper designs a new four-wheel drive SUV electric-hydraulic hybrid power system,and completes related parameter matching and model building works.And based above works,energy management strategy(EMS)of the system is studied emphatically for the economic performance of the vehicle.The specific work content is as follows:(1)Based on the front and rear dual motors pure electric vehicle(SUV)configuration,a four-wheel drive SUV electric-hydraulic hybrid power system with a front motor and a hydraulic pump/motor connected in parallel is designed,and multiple working modes of the system are analyzed.And based on the vehicle parameters and performance indicators,the theoretical calculation method,the comprehensive analysis method of driving cycle and the optimized matching design method are flexibly used for parameter matching of key components of system,such as hydraulic pump/motor,torque coupler transmission ratio,accumulator,front motor,rear motor and battery.(2)On the MATLAB software platform,models of the key component of the four-wheel drive SUV electric-hydraulic hybrid power system,such as hydraulic pump/motor,accumulator,motors,battery,and the longitudinal dynamics model of the vehicle are built.And from the three dynamic performance indicators of maximum speed,maximum climbing degree and 100 kilometers acceleration time,dynamic simulation was performed to verify the correctness of the parameter matching results.(3)In order to obtain the global optimal simulation results as the evaluation criteria for other real-time EMS,a global optimal energy management strategy based on dynamic programming is proposed,simulation is performed under CLTC-P,and the global optimal simulation results are obtained.(4)Through the analysis of the limitations of the dynamic programming global optimal EMS,an EMS based on the optimal instantaneous efficiency under the premise of meeting the instantaneous power demand of the vehicle is proposed: Under driving conditions,the drive control strategy is formulated based on the principle of optimal power output instantaneous efficiency,and under the braking conditions,the braking control strategy is formulated based on the principle of instantaneous maximum energy recovery efficiency under the premise of complying with ECE braking regulations and as close to the I curve as possible under medium and high braking intensity.In order to verify the effectiveness of this strategy,simulations were carried out under multi-braking intensity braking conditions and CLTC-P.The simulation results show that this strategy has good economic performance and can achieve a global optimal effect of 97.43%.(5)Through the analysis of the instantaneous efficiency optimal energy management strategy,the optimization method of the instantaneous efficiency optimal EMS based on model predictive control(MPC)is proposed.A one-step acceleration prediction model based on Markov chains,a feedback correction model using the error between the predicted acceleration and the actual acceleration,and rolling optimization model that a dynamic programming algorithm are used to solve the smallest energy consumption in the prediction domain are built.Under CLTC-P,the optimized strategy was simulated and verified.The simulation results showed that through the optimization of MPC,the economic efficiency of the instantaneous efficiency optimal EMS is increased by 1.13%,and it can achieve a global optimal effect of 98.54%. |
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