Study On Optimal Control Method For The Hybrid Electric Vehicle Equipped With CVT

Vigorously developing new energy vehicles not only promotes scientific and technological progress,but also satisfies the demand for environmental protection,green,and low-carbon ecological civilization construction.It is also a major measure for China's auto industry to realize "Curve Overtaking" and is in line with the country's sustainable development strategy.Hybrid electric vehicles(HEV)are increasingly becoming the focus of the automotive industry with their advantages of long mileage and low fuel consumption.In this paper,HEV equipped with CVT(Continuously Variable Transmission)is taken as the research object.The energy distribution of its power source and the CVT shift strategy are studied and simulated by using dynamic programming algorithm.The research contents are as follows:(1)The system structure plan of single motor and parallel type for HEV equipped with CVT is determined,and various performance indexes of the vehicle are formulated by the parameters of the mainstream vehicle in the market.According to the requirement of the target model,the parameter matching of the hybrid powertrain and the key power unit are completed.(2)The principle of DP algorithm is described,and its calculation process is analyzed.The method of dynamic programming backward simulation modeling is determined in this paper.The vehicle backward simulation model based on DP algorithm is further established,and the concrete process and steps of DP algorithm to solve the optimization problem are summarized.(3)Under the drive cycles of NEDC and JN1015,the minimum equivalent fuel consumption is taken as the objective function and the simulation results are analyzed;compared with the energy management strategy based on ECMS(Equivalent Consumption Minimization strategy),it is found that under the drive cycle of NEDC,compared with the instantaneous optimization,the overall energy management strategy improves the fuel economy of the whole vehicle by 10.03%,and the fuel economy of the whole vehicle increases by 13.23%under the drive cycle of JN1015.(4)The control rules of the motor,engine torque distribution coefficient and CVT speed ratio were extracted under the drive cycle of NEDC,and the three-dimensional graphics of vehicle speed and vehicle demand torque were plotted,which is expected to be applied to the energy management strategy of forward simulation model.The research results of this paper can provide practical reference for designing the energy distribution and CVT shift control strategy of hybrid electric vehicles equipped with CVT,which have certain theoretical research value.