Study On Optimization Of Powertrain Matching Of City Bus Under The Constraint Of Exhaust Emission

Currently, environment pollution and energy shortage have became two striking conflicts which threaten the human existence. The increase of vehicle possessive quantity not only makes China an oil-imported country, but also makes the environment in the city become worse and worse. In some area, the environment was badly polluted. For the city-bus, its fuel economy and exhaust emission are bad because of bad operating conditions. The vehicles performance mainly depend on the reasonable matching of its powertrain systsms. So it's necessary to make fuel economy and exhaust emission the important factor of evaluating the synthesized performance of city-bus, and make a further study on fuel economy and exhaust emission besides power performance, on account of overlooking the exhaust emission in powertrain optimal matching.ADVISOR is used to be the performance simulation platform.As to the limitations of the software which can only simulate the front drive vehicles, ADVISOR is redeveloped, and the models of rear drive and each part of powertrain are establish in this paper. The models are feasible by simulation analysis.The pointers of power performance,fuel economy and exhaust emission are the most basic and important one used to evaluate the vehicle.But the development of these is relative restraint,which leads to hard to judge the matching scheme.So a synthesized evaluating system is investigated by principal compontents analysis.which provides a reference for optimal design of powertrain,and avoids the subjectivity of choosing the weight coefficient when.According to the theory of vehicle, the powertrain system is predesigned, including the fixing of the engine power,maximum and minimum tansmission ratios and driving axle ratio.Based on the optimal design theory, considering the power performance,fuel economy and exhaust emission integrately, it unites three target functions which are origin underway accelerate time, the oil consumption at the cycle of muti-working conditons and pollutant emission into an aim function by using linear weighted combination, and it is solved with penalty function method. Finally, a city-bus is taken as an example,by comparing the performance of the three matching schemes,the matching degree calculated by the evaluating method proposed above is 42.9475,13.2111 and 13.1345 separately,and the smaller the result,the better. From this, the vehicle's synthetic performance after optimization is developed,and the purpose of optimal matching of powertrain system is got.