Optimization Of Shifting Strategy For Electric Buses Equipped With4-AMT

Environmental protection and sustainable energy development have been the majorthemes in the world and they have restricted the keys to future world economic development,while the pure electric vehicle becomes a hot spot in today’s automotive industry because ofits zero-emission characteristics. Due to its simple structure, reliable, high transmissionefficiency, low manufacturing and maintenance cost, automatic mechanical transmission(AMT) has been widely used in pure electric buses.After matching of the powertrain system, the vehicle needs a reasonable shifting strategyto take full advantages of the electric vehicle, thereby improving the power, economy andreliability characteristics of the vehicle. This paper carries out theoretical calculation,modeling, simulation and real vehicle tests of shifting strategy for an electric bus, which isbased on the National863Project “Technology research of electric commercial vehicle(M3/N3) power system platform”, mainly expanding the following three aspects:Firstly, comparing many simulation softwares, MATLAB/Simulink is used to establishvehicle dynamics model ultimately, including AMT controller to simulate shifting process.The model is based on the analyzed data from the electric vehicle. After establishing themodel, simulate the power and economy characteristics of the vehicle and compare with thereal vehicle. The results show that the simulation platform can be used as a basic platform ofshifting strategy research.Secondly, according to dynamic programming, the electric vehicle control strategymodel has been set. After determining the control variables and state variables, the m.file hasbeen written to calculate the problem under the Chinese typical urban condition. Bysummarizing the calculation results, the decision variables of the control strategy has beenobtained. The shifting schedule is extracted from the result which can be used in the realvehicle. Fuel economy has been simulated in the simulation platform and the result iseffective obviously. Shifting schedule occupies an important position for electric vehicle, butthe existed shifting decisions are not perfect. The shifting schedule based on dynamicprogramming algorithm is firstly used in the real vehicle, and a satisfactory results is obtained.To optimize shifting strategy, the road condition has been taken into account on the basis of longitudinal dynamics analysis. Estimations of road slope have been accomplished withthe method of Kalman filter (KF). Finally, the3-parameter shifting schedule consideringslope is designed and the improved shifting control method introduces predictive target speedcontrol to replace the traditional time-varying target speed control in the stage of motor activesynchronization if vehicle is on a slope. The simulation verifies the effectiveness of optimizedshifting strategy that improve the power, economy and reliability characteristics of thevehicle.