The Study Of Parallel Series Hydraulic Hybrid Vehicle Based On Urban Driving Cycles

Hydro-mechanical variable transmission combines the advantages of mechanical transmission and hydraulic transmission, it has great foreground in heavy-duty vehicles due to its characteristics of variable speed regulation and high efficiency. The hydraulic regenerative braking system based on HMT which adopts hydraulic pump/motor and hydraulic accumulator as energy conversion and storage units can not only implement the steepless change of transmission ratio,but also realize the recycling and reusing of the braking energy efficiently, which is suitable for the condition of frequent stop and go. The key technology of parallel-series hydraulic vehicle such as parameter matching, energy control strategy is a hot research area in this field.This paper aims at the parallel-series hydraulic vehicle, the main content includes:(1) According to the parameters of the vehicle and the requirements of the urban driving cycles, a new transmission scheme of parallel-series hydraulic vehicle based on hydro-mechanical variable transmission is proposed, parameters of the main components are calculated under the urban driving cycles, and the power train configuration are chosen on basis of actual product parameters.(2) The forward simulation model of parallel-series hydraulic vehicle is established, including the engine model, the hydraulic accumulator model, the hydraulic pump/motor model, the controller model and the driver model. The deviation between the desired speed and the actual speed of the driver model is amended by the PID controller.(3) A logic threshold control strategy of hydraulic hybrid vehicle based on the engine optimal work region is proposed, and the control strategy model is established in MATLAB/SIMULINK simulates. At last, analysis of the control strategy is carried on under the urban driving cycles, and the energy releasing rate is obtained, the analysis of the hybrid system performance is also carried out under the hydraulic stepless speed change condition and the mechanical condition.(4) An optimal control strategy of energy recovery which is based on the brake by wire system is proposed, and the control strategy model is established in MATLAB/SIMULINK simulates. At last, analysis of the regenerative braking effectiveness is carried on under the urban driving cycles, the condition of light braking and composite braking. The energy recovery rate and the utilization ratio of recovery system are obtained. In this paper, the study which is about parameter matching and control strategy of hydraulic hybrid vehicle can provide guidance for the follow-up study and vehicle design.