Temperature Observation Model for Wet Clutch of 9AT Based on Heat Transfer Theories

During vehicle driving, the surface temperature of the wet clutch is difficult to be measured directly, which poses a huge challenge for accurate clutch temperature control. To the above problem, this paper investigates a 9-speed automatic transmission (9AT) as the research object, the clutch slip calculation Model is established based on the kinematic equations, which contains the following different driving conditions: driving in neutral or fixed gear, shifting process, and the engaged clutch sliding under a certain specific circumstances. Then the temperature observation model for the wet clutch is established based on the heat transfer theories, which realize the real-time observation of clutch temperature during the vehicle driving process. The dynamic simulation model of 9AT is built based on SimulationX software to verify the accuracy of the clutch slip calculation results. The temperature observation simulation model is also built based on Matlab/Simulink software, and the simulation results are compared with the real test results of a benchmarking vehicle. The results show that the temperature observation model could better fit the actual temperature changes during the working process of the wet clutch, in which, compared with the real vehicle test data, the maximum error is within ± 5 °C, which can meet the requirements of real-time observing and control of clutch temperature during vehicle driving.