Dynamic Modeling And Integrated Control For Automatic Transmission Shift Process

With the social and economic development as well as the improvement of people’slife, consumer’s requirements for vehicle fuel economy, power, handling convenience andride comfort and drive safety are also rising, while governments are also taking more andmore stringent restrictions on vehicle emissions. As a key assembly of vehicle components,transmission influences vehicle’s comprehensive performance deeply. Highly automatedtransmission has become an inevitable development trend of the automotive powertrain,and also become an inevitable link for the development of intelligent vehicles.For vehicle equipped with automatic transmission, constantly changing drivingconditions, lots of unknown and nonlinear factors in powertrain and dynamiccharacteristics of numerous hydraulic transmission and control links bring varyingdifficulties to automatic transmission control, especially the engine-automatic integratedcontrol for shift process.This paper is supported by "Off-Road Vehicle Integrated Control Technology-ATControl Technology Research" project which is studied by Jilin University and ChinaFAW Group Corporation R&D Center. In this paper, a vehicle with Allison3500R AT isstudied, and then the structural characteristics and working mechanism of AT are analyzedsystematically. Based on the analysis of AT workings, dynamic modeling method is usedto build the vehicle powertrain simulation platform including the engine output torquedynamic model, the torque converter model, the planetary gear drive mechanism model,the clutch/brake model and hydraulic control system model as well as vehicle dynamicsmodel. And this simulation platform is validated and improved by the bench test.Based on the work done, shift process of AT is divided into torque phases and inertiaphase, and the control principle of clutch to clutch shift is studied with the lever method.Then, inertia phase engine&transmission integrated control principle and entire shift process engine&transmission integrated control principle are respectively studied withtaking power on up shift as study example and taking the transmission output torquefluctuations during shifting minimum as control target.For the factors that affect shifting during different stages and the characteristics ofdifferent shift control principles, inertia phase engine&transmission integrated controlstrategy based on the transmission output torque observer which is designed based on thetorque converter model as well as entire shift process engine&transmission integratedcontrol strategy based on clutch pressure observer which is designed based oninput-to-state stability (ISS) is designed.Finally, inertia phase engine&transmission integrated control strategy based on thetransmission output torque observer which is designed based on the torque convertermodel is applied on the vehicle simulation platform, then it is simulated with power on upshift. Simulation results are compared to the results of power on up shift without engine&transmission integrated control, and it is proved that the transmission output torqueovershoot peak with inertia phase engine&transmission integrated control strategy isdecreased significantly and shifting jerks are reduced. Shift quality is improvedsignificantly.