The automatic transmission enables automatic vehicle launch and automatic gear shifting, improving driving comfort and reducing driver fatigue. It also improves vehicle power performance, fuel economy and emissions, and has gradually become standard equipment in modern vehicles. The automatic transmission system consists of the TCU, the gear selector mechanism and the clutch mechanism: the TCU acquires sensor information and CAN bus data, and after computation controls the actuators to realize gear selection and shifting, clutch operation and engine handover control.

Without a P-gear function, an electric vehicle can only be left in neutral when parked, which poses a safety risk. To ensure safe and reliable parking, electric vehicles should be equipped with a P-gear locking mechanism. The P-gear control on an electric vehicle serves the same function as the “parking gear” of a conventional automatic transmission, and this function is accomplished by a complex motor system.