Coordinated Clutch Slip Control for the Engine Start with Power-On Downshift in a P2 Hybrid Automatic Transmission

The impact and vibration problem during gear shifting and mode switching of the P2 hybrid 8AT system of new energy vehicles seriously affects driving comfort. This paper proposed a collaborative clutch slip and friction control strategy for a P2 hybrid power system with power downshifting and engine starting to reduce transient shock vibration during the power system operation. A dynamic model of the P2 hybrid system was established, including a physical model of the engine, motor, clutch, 8AT transmission mechanism, and driving resistance. The transient dynamic behavior of the P2 hybrid system with power downshifting and engine starting was systematically studied. On this basis, with the goal of consistent power response and smooth gear shifting, a multi-stage collaborative control strategy including the motor, engine, and clutch under the power downshifting condition was formulated. Model-in-loop simulation verification was carried out based on MATLAB/Simulink platform. The simulation results show that compared with traditional methods, the proposed control method can effectively improve the power performance and comfort of the P2 hybrid power system.