Gear shift strategy for a new 8-speed automatic transmission

In order to achieve engineering application for a new 8-speed automatic transmission, a simplified dynamic model for hydraulic automatic transmission was built and key control parameters that affect shift quality were analyzed. For the four basic shift types, the ideal curves of shift clutch and engine control were set up. Based on torque estimation method, PI slip control algorithm and engine coordinated control theory, the control model and transmission controller were developed for three shift phases which included rapid-fill phase, torque phase and speed phase. In rapid-fill phase the command pressure at oncoming clutch was set as the kiss point at which point the oncoming clutch just transmits torque , in torque phase the torque change rate at off going clutch was controlled as similar as oncoming clutch based on torque estimation, in speed phase the engine torque reduction control was added to reduce the shift jerk. An environment of the rig and vehicle tests was built and the testing results obtained in extreme conditions can verify the accuracy and feasibility of this shift control strategy. The peak jerk during shift process was reduced significantly and the smooth gearshift was obtained. The strategy has high value for engineering application.