Study On The Method Of Urban Bus Gearshift Decision Optimization For Fuel Economy

Urban bus operation is a “man-vehicle-road” closed loop system.The traditional automatic transmission control system with a fixed shift schedule to judge the gearshift point is difficult to adapt to different operating conditions,different road environment,especially unexpected and back-to-back shifting under road conditions such as uphill roads,downhill roads and curves,greatly increase the fuel consumption.Therefore,how to improve the fuel economy on the basis of ensuring the power performance of urban buses is the key to the optimization of gearshift decision.Aiming at fuel saving,this paper focuses on the problems that the original gearshift mode of urban bus can not adapt to different conditions and road environment,and can not take into account the power performance and economic performance.Firstly,based on Global Navigation Satellite System(GNSS),this paper puts forward the overall architecture of urban bus gearshift decision optimization system,and introduces the acquisition of CAN information and GNSS road information,then the evaluation index of gearshift decision is put forward from three aspects of power,economy and drivability.Secondly,on the basis of reasonable simplification of urban bus transmission system,the overall model of gearshift decision is built,and the correctness of the model is verified by speed following simulation.Then,using principal component analysis and K-means clustering analysis,the line working conditions are divided into three types of working conditions: unimpeded,generally unimpeded and crowded.Based on this,dynamic programming algorithm is used to extract the static optimal shift schedule applicable to different working conditions.Finally,based on preobtained road information by GNSS,the gearshift optimization strategy of uphill roads,downhill roads and curves is formulated.Compared with the original shift schedule,the simulation analysis under three road environments and comprehensive line conditions shows that the proposed strategy effectively reduces the phenomenon of unexpected and back-to-back shifting,increases high gears utilization ratio by 11%,reduces the number of gears switch by 14.75%,reduces the cumulative fuel consumption by 4.85%,and the engine working point is closer to the economic working area.