Research On Configuration And Parameters Optimization Method Of Single Planetary Gear Multi-mode EVT Hybrid Powertrain Under Multi-objective Conditions

In today’s social situation,energy saving and environmental protection have become the benchmark for the development of the automotive industry,and the development of hybrid vehicles is an effective way to improve the current environmental pollution and energy crisis.The EVT(Electrical Varibel Transmission)hybrid powertrain system,as a typical representative of a Parallel-Sereis Hybrid Elctrical Vehicle,can achieve the decoupling of the engine and wheel speed,and has better performance.The multi-mode EVT powertrain has better performance in terms of fuel economy and power performance due to its multiple modes and strong adaptability to operating conditions.The research object of this thesis is a single planetary gear set multi-mode EVT hybrid electrical powertrian.The main work includes the study of its topology configuration and the optimization of configration and parameters.This thesis carried out the following research:(1)The hierarchical topology of EVT powertrain and its matrix expression model are established and improved.The common speed transmission matrix representing the speed relationship is proposed,which enriches the research theory of graph theory in EVT powertrain design and further solves the problem of computer description of EVT powertrain topology.(2)Based on the method of hierarchical topological graph theory,the dynamic model of EVT powertrain graph theory was built,and the formation law of configuration topological dynamics was analyzed.Based on the algorithm of search tree and the the metamorphic theory,a dynamic automatic modeling method of EVT powertrain configuration was proposed,which improves the dynamic automatic modeling theory based on hierarchical topological graph,and realizes the computer identification and dynamic automatic modeling of batch EVT powertrain configuration.(3)Based on the graph theory,the optimization of a single planetary gear set multimode EVT powertrain scheme was studied.Through the generation of EVT system configuration patterns,automatic modeling of dynamics,isomorphic screening,mode classification,multi-mode combination and other methods,the automatic generation of multi-mode EVT powertrain configuration scheme and dynamic automatic modeling was realized.Using the comprehensive evaluation method of fuel economy based on PEARS+ algorithm and acceleration performance based on DP algorithm,the planetary gear set multi-mode EVT configuration scheme was optimized,and the better scheme was selected for statistical analysis based on DP algorithm and for key mode analysis.(4)The EVT powertrain parameter optimization study was carried out under multiobjective conditions.Based on the multi-objective optimization algorithm NSGA-Ⅱ,the transmission parameters and power component parameters of the optimized configuration was optimized with the fuel economy,power performance and EVT powertrain cost as the optimization objectives.(5)Based on NSGA-Ⅱ algorithm,the joint optimization method of configuration scheme and parameters was studied under the multi-objective conditions.In the design domain of 9 better configuration schemes and 6 key parameters,the key parameters was identified based on the Optimal Latin hypercube Design,and the joint optimization of configuration and parameters was carried out for the identified design domain.The relationship between the better design schemes and optimization sub objectives of EVT powertrain was discussed.