Research On Matching Of Power System And Shifting Schedule For Parallel Hybrid Electric City Bus

The global warming and scarcity of non-renewable energy has been an increasingly serious environmental issue for decades.As one of the most effective measure to the problem of environment pollution and energy shortage,Parallel hybrid electric vehicle(PHEV)takes advantage of pure electric vehicle and traditional internal combustion engine vehicle,it can also optimize the distribution of two different power sources(engine and motor),and improve the efficiency of hybrid power system,furthermore,reach the target of energy saving and emission reduction.So PHEV has become one of the most vital fields to new energy study.Researching areas of PHEV such as parameters calculating and matching for hybrid power system and vehicle control strategy,shifting schedule,etc.,these directly affected the performance of exhaust emissions,vehicle dynamic performance and fuel economy performance.By analyzing the advantages and shortcomings of different kinds of hybrid power systems structure,this thesis designed single-axis parallel structure,on this basis,dynamics and automobile theory analysis the parallel hybrid electric bus(PHEB)and presents the parameter matching of its power assembly system,which can meet the power and fuel economy requirements under the corresponding circulation condition.For advanced analysis,this thesis builds forward simulation models of PHEB on AVL Cruise.Second,this thesis compared and analyzed the modes of vehicle status,and designed the rules of modes switch and torque distribution strategy based on logic threshold.In order to validate the shifting schedule for optimal fuel economy,this thesis made two-parameter(velocity and throttle position)shift rule which is consistent with real parallel hybrid electric bus and designed three-parameter(velocity,engine torque and motor torque)shift rule respectively.Three-parameter shifting surfaces are calculated in Matlab,combined this with fuzzy control in Matlab/Simulink for shifting schedule model,the results of co-simulated technique proved that three-parameter shift rule is better than two-parameter shift rule and can get obvious improvement on vehicle fuel economy performance,which based on the vehicle dynamic performance.Finally,this thesis applied above method for Chinese City Bus Cycle co-simulation.By comparing the simulation and real vehicle road test results,it proved that the three-parameter shift rule can improve the performance of exhaust emission and fuel economy.And the reliability and validity of vehicle model can be verified by comparing the two simulation results.In summary,this thesis applied theoretical calculation method and driving cycle test for powertrain parameter matching,simulation combined with road test which analyzed the energy management strategy and shift rules after the model has been verified.It added weight to the rationality and feasibility of control and shift strategy,provided theoretical foundation and also designed an effective process which can be referred for PHEV developing and research.