Research On Shift Control Of Parallel Hybrid Bus With Single Planetary Power Coupling

The emissions of pollutants of bus is quite large in major cities in China even though its market share is not much, while hybrid electric bus has the advantages of high efficiency and low emission, which is of significanceto be develeped.During the driving process of the bus, the manual shift is difficult due to frequent shift resulted from complex running conditions and multivariate shift strategy in hybrid buses equipped with a motor system and engine system. However, the bus equipped with automatic transmission will lighten the burden of the driver because of its automatic transform of gear based on road conditions. Automatic mechanical transmission(Automated Mechanical Transmission, referred to as AMT) is the ideal option in many kinds of automatic transmission for its advantages of simple structure, low cost, high transmission efficiency as well as decreasing emissions in case of excellent control strategy.However, due to restrictions on the structure of AMT, the process of shift exist powerinterruption and pulse and other defects, which will seriously affect the riding comfort. Therefore, this paper, using single planetary row dynamic coupling of parallel hybrid electric bus as the research platform, tries to improve the shift quality by researching the control strategy of AMT shifting process. The main contents of this paper are as follows:(1) Analyze the structural features of single planetary power coupling of the hybrid system. This paper acquires characteristics of speed and torque of the planetary gear mechanism by using the imitating leverage method. On the basis of the characteristics, 8 operation modes of the hybrid system are analyzed, laying the foundation for the establishment of AMT shift control strategy.(2)The shifting control strategy of hybrid bus can be divided into two categories according to whether or notthe wet clutch is participated in the operation process. The dynamics model of transmission system are established according to the speed coupling driving mode(shift without clutch operation) and enginedriving mode(shift clutch operation).Thena detailed analysis of shift process is done to find out key factors toshift quality in every stage of the shift processaccording to the corresponding evaluation index.(3) Design the shift control strategy. In speed coupling mode, by controlling the opening degree of engine throttle andmotor speed to ensure good shiftquality. In engine driving mode, fuzzy control rules for wet clutch are established to improve the bonding qualityaccording to operation characteristics of the wet clutch. In addition, automatic shift control system is created using Stateflow.(4) Based on Matlab/Simulink and AMESim co-simulation platform, up-and-down shift modelsrespectively forfirst gear and second gear in engine driving mode and third gear and fourth gear inspeed coupling driving mode are created, and then simulation results are analyzed. After the offline simulation, this paper constructs Moto Tron hardware-in-the-loop simulation testplatform, and verifies the reliability of the control strategy and the accuracy of the simulation model.