Study On Control Strategy And Parameter Optimization Of Hybrid Electric Bus Based On Hybrid System Theory

The most challenging goals the sustainable development of automotive industry facing are energy crisis and environment pollution. The hybrid electric vehicle (HEV), which applied the internal-combustion engine and battery as power sources, is considered as a most promising kind of electric vehicle for industrialization currently. The research on the parameters matching and control strategy is the key technology of the HEV.In this paper, the 6110 type Series Hybrid Electric Bus (SHEB) was selected as the studying object. Based on the analysis on characteristics of the city bus cycle, the overall design was designed for the 6110 type SHEB. The simulation method which combined the forward facing method and backward facing method was applied. The simulation models of SHEB and key parts (including engine-generator model, motor model, battery model, multi-energy control strategy model, braking force distribution model and the integrated vehicle model) were constructed based on the characteristics of the rear wheel driving city hybrid electric bus. The models were simulated and analyzed for the verification combined with the test of the sample vehicle. The result shows that the models satisfied the requirements of actual instance and it could be the base of the research on the control strategy simulation of SHEB and parameters matching of powertrain.The hybrid system theory was introduced for the first time based on the analysis of energy flow modes of SHEB. Based on the concept of hybrid dynamic system and the model of hybrid automata, the mathematic model for the dynamic control system of 6110 type SHEB was founded. Base on the analysis on the design objects and rules of energy control strategy, the mode transform control strategy was designed, which got the advantages of constant temperature type and power-follow type together, and the harmonious regenerative control strategy for the regenerative braking force of motor, the friction braking force, the braking force for the front and rear wheel is adopted.The simulation models of mode transform energy control strategy, regenerative braking control strategy of harmonious control for braking force and integrated vehicle were founded based on Simulink/Stateflow by the combined modeling method. The three kinds of control strategy simulation were conducted under typical urban driving cycles by the mode transform type, constant temperature type and power-follow type. The result shows that the economic performance of mode transform control strategy is preferable to constant temperature type and power-follow type, the fuel consumption was 23.9L/100km, which is reduced by 4.8% compared with the sample applied synthesis type control strategy, and reduced by 17.3% compared with tradition city bus. The simulation of the harmonious control strategy of braking force and the fixed-ration braking force distribution strategy were conducted. The result shows that the harmonious control strategy was improved by 11.5% compared with the vehicle applied the fixed-ration distribution strategy, and the fuel consumption was reduced by 3.2%.On the basic of the primary parameters matching for the powertrain of SHEB, an orthogonal optimization method for the synthesized parameters, which is composed of powertrain control parameters and the parameters of parts, was introduced for the 6110 SHEB according to the orthogonal test design theory. A set of parameters was acquired after the optimization:H=43.3%,C=75Ah, ig=2.73 and the mode transform type control strategy was applied. The simulation of 6110 SHEB was conducted after the optimization. The result shows that the dynamic performance was improved and the fuel consumption was reduced by 8.4% compared with the road test before the optimization.Based on the design theory of modularization, the powertrain assembly test bench and the testing system were constructed based on the design theory. The testing methods and criteria were enacted. The performance test for the key parts of the SHEB and the road tests for the dynamic and economic performance of real vehicle were conducted. The result shows that the powertrain could satisfy the requirement of integrated vehicle. The performance of the sample vehicle could satisfy the requirements of the design task. It verified that the structure of the powertrain and the method of parameters matching are proper. By comparing simulation results with road test results, it proved that the simulation model is exact and the energy management strategy based on dynamic mode transform is feasible.