Study On Intelligent Gear Shift Strategy For Automatic Mechanical Transmission Of Light Commercial Vehicle

The shift strategy design is one of the most important step during the automatic transmission application process.The continuous progress of science and technology makes the performance of automatic transmission system has not only meet the performance of automatic shifting control,but also requires the system to integrate in different road environments and the driver's intention,then the vehicle can get better power,economy,comfort and even security performance.Integrated intelligent shift strategy is one of the hottest research direction in automatic transmission control system.As the driving conditions of light commercial vehicle(LCV)are complex,transmission control system need to control the gear to shift more frequently in strict conditions.Lower system cost determines the mechanical automatic transmission(AMT)is the preferred type for light commercial vehicle.Based on one domestic light commercial vehicle,the following aspects about AMT shift control system are studied and analyzed:Firstly,in order to simplify the development process of the shift strategy,the vehicle's driveline dynamic system is modeled.The sub-models are also established and integrated,including the engine steady-state torque model,the clutch torque transmission model,the transmission and main reducer dynamics model and the vehicle dynamics model.Besides,on the basis of summarizing all types and characteristics of the basic shift strategy,the optimal power shift strategy and the optimal economy shift strategy are established based on the strategy with the speed and throttle opening as control parameters.The dynamic simulation model are established by Matlab/Simulink,which laid the foundation for the simulation study of shift strategy with different driving intentions and the road environments.Then,based on the analysis of driver's intention,a multi-input single output(MISO)fuzzy reasoning model is established.the drivers' intention recognition model is studied and verified by relevant simulation experiment.The relationship betweendrivers' intention(including drivers' acceleration and deceleration and the maintenance intention)and shift strategy is studied,and relevant shift strategies are also established.A series simulation test cases prove the rationality of the shift operation.Finally,on the basis of analyzing the vehicle's longitudinal dynamic model,the slope value of the current road environment is identified by calculating the vehicle load L.Gear shift control rules are developed according to the different characteristics of the uphill and downhill environments.The simulation results show that the phenomenon of the shift circulation problem disappears with the uphill shift strategy;the downhill shift strategy can take reasonable downshift control in time so as to make better use of the engine braking characteristic.