Simulation And Parameter Optimization Of Regenerative Braking System Of Hydraulic Hybrid Vehicle

In hybrid power technology, the hydraulic transmission technology has the advantagesof the higher power density and the stronger ability of full charging and discharging, and thehydraulic system occupies absolute advantages in weight and braking efficiency, and themost of braking energy can be recycled. So the application of hydraulic system on the hybridvehicle can effectively improve the fuel economy, significantly reduce exhaust emissionsand the noise pollution. Due to parallel hybrid vehicle has the smallest modification to theoriginal driving system, so the parallel hybrid vehicle is selected as the research objective.The configuration scheme and parameters matching of the hydraulic hybrid systemhave a great influence on the fuel economy and vehicle performance. Therefore the couplingscheme of vehicle, the parameters design and the parameter influence analysis of thehydraulic system are researched combined by the National Natural Science Foundation (No:51075179), and a method of multi-objective optimization is proposed. The main researchworks are as follows:1. Configuration Selection and Parameters Matching of Regenerative BrakingSystemThe energy storage form of hybrid vehicle and the series, parallel and compound formof hydraulic hybrid vehicle are analyzed. The parallel hydraulic system is selected as ahybrid regenerative braking device, and the parameter matching of the hydraulicregenerative braking system are introduced.2. Coupling Scheme Analysis of Hydraulic Regenerative Braking SystemFour coupling schemes are got according to the different coupling position of engineand hydraulic system and whether is pressure oil supplying. The parameters of the hydraulicsystem of the four coulping schemes are design and the simulation models are established inthe AMESim software. DARE is used to evaluate the four coupling schemes from the threeaspects of fuel economy, power performance and system cost. According to the evaluationresult shows that the scheme, which the engine and hydraulic system is coupled in front ofthe transmission and pressure oil supplying, has a higher fuel economy and the comprehensive appraisal score is highest. Therefore this hydraulic hybrid scheme is selectedas the research objective.3. Influence Analysis of Parameters on Hydraulic Regenerative Braking SystemThe influence of the parameters on the vehicle performance are studied, the studiedparameters include hydraulic pump/motor displacement, accumulator volume, prefilledpressure, working pressure of accumulator and ratio of torque coupler. And the influenceregulations of hydraulic system parameters on vehicle performance are summarized.4. Parameter Optimization of Hydraulic Regenerative Braking SystemBased on bi-level programming method and combinational optimization method,hierarchical multi-objective optimization method is put forward for multi-objectiveoptimization. The fuel consumption and emissions are selected as the first-class optimizationobjectives, and the starting accelerate time is selected as the second-class optimizationobjective. The design variables are selected according to the influence analysis of theparameters and the rules of parameters matching. OLHD is used to gain sample points, andKriging is used to establish the surrogate models of the objective functions. NSGA-II andNLPQL are selected as the first-class and second-class optimization algorithmsseparately. Fuzzy evaluation method is used to gain a compromise solution from the Paretosolutions of multi-objective optimization. In order to prove the validity of the hierarchicaloptimization method, a multi-objective optimization is done which the fuel consumption andemissions are the optimize objectives, the starting accelerate time is the constraint conditions.The comparing results show that the proposed hierarchical optimization method can be usedto solve the optimization design problem between the fule consumption, the emission andthe power performance.