transmission 26 and a battery 28 the hcu 10 controls operation of other controllers which mutually exchange information in an entire operation of a hybrid electric vehicle so that the hcu 10 controls output torque of the engine 20 and the motor 24 by cooperating with the other controllers the ecu 12 controls an entire operation of the engine 20 according to conditions of the engine 20 such as a demand torque of a driver a coolant temperature and an engine torque the mcu 14 controls an entire operation of the motor 24 according to a demand torque of a driver a driving mode of the hybrid electric vehicle and an soc condition of the battery 28 the tcu 16 controls an entire operation of the transmission 26 such as speed ratios of the transmission 26 depending on output torque of the engine 20 and the motor 24 and an amount of regenerative braking the engine 20 outputs power as a power source while turned on the engine clutch 22 is disposed between the engine 20 and the motor 24 to receive a control signal of the hcu 10 and selectively connects the engine 20 and the motor 24 according to a driving mode of the hybrid electric vehicle the motor 24 is operated by a 3 phase ac voltage applied from the battery 28 through an inverter to generate torque and operates as a power generator and supplies regenerative energy to the battery 28 in a coast down mode the transmission 26 supplies a sum of an output torque of the engine 20 and an output torque of the motor 24 determined by coupling and releasing of the engine clutch 22 as an input torque and selects any shift gear according to a.