Research On Energy Management Strayegy Of Parallel Hydraulic Hybrid Vehicle

Using hydraulic pump/motor quadrant operating characteristics, the hydraulic hybrid system can effectively recover braking energy and reuse gravity potential energy. Because of its high power density, the hydraulic hybrid system fits for heavy load city bus and construction machinery very much. When all parts of the structure and properties of the characteristics are confirmed, the fuel economy and emission levels depend on energy management strategy.The HEV has been deeply researched in our country. Because the hydraulic units are of great different in characteristics with electric units, so the design experiences, control diagrams and energy management strategies in HEV can not be transplant to HHV directly. So separately researches on HHV should be done in this paper.This research work is mainly about hydraulic energy-saving vehicle energy management strategy, aiming at the best fuel economy; strategies are found and optimized considering the accumulator SOC, GIS, etc. The main research work includes:1. Put forward an equivalent engine and equivalent tank theory to evaluate HHV's fuel economy from the sign of energy for the convenience of optimizing and evaluation the energy management strategies with computer simulation methods.2. Key components models, driver operation purpose fuzzy logic model, and hydraulic hybrid system dynamic model are established.3. HHV transient energy management strategy in driving condition are established. Based on the equivalent model, the hybrid system energy charge and releasing efficiency model is built. The regenerative braking energy recovery influence coefficient is introduced to reflect the regenerative braking energy recovery of energy management strategy of influence and the reduction of car fuel consumption. And the function from SOC to the influence coefficient is studied.4. HHV energy management strategy under the certain driving cycles is built up considering SOC. And the empty and full-load HHV fuel economy simulations are operated with the UDDS driving cycle.5. The experiments as vehicle start, power assistant, energy recovery control and driving cycle energy control are operated by means of a hydraulic hybrid system test bench.The proposed research prepared a series of theory for HHV design and produce, and made the theoretical base for hydraulic hybrid system fuel consumption evaluation and control strategy development during the stage of design, which are of great theoretical meaning and application value.