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A parallel type HEV (Hybrid Electric Vehicle) has a power transfer device that is constructed by wet clutches and the device is called 'Engine Clutch'. The Engine Clutch is located between engine and electric traction motor so it transfers power of engine when the engine is started and clutches are engaged or cut the power when regenerative braking is occurred. When a traction motor of a parallel type HEV (Hybrid Electric Vehicle) could not generate torque to launch, the HEV should launch only by engine power.Because the engine should rotate at the stated idle speed to prevent the engine stop the relative rotational speed of clutch input and output shaft starts from engine idle speed and ends to zero when clutches engaged.In this study a method for control pressure command of engine clutch is proposed to satisfy desired clutch engagement time and decrease shock. A dynamic model of a parallel type HEV powertrain (including hydraulic clutch control components) is constructed to validate the method proposed.

The series-parallel hybrid electric vehicle, which employs a planetary gear set to combine one internal combustion engine and two electric motors, can take advantages of both series and parallel hybrid system by controlling power flows. In this system, the control of power flows means adjusting not only the amount and direction of mechanical and electrical power but also the operating point of the engine. This study introduces the power distribution strategy which uses control maps to minimize the loss in power flow and operate engine on efficient point. And the control maps can be obtained by optimization process seeking efficient operating point for the given speed, load and battery charge/discharge power. The suggested strategy distributes the power flows efficiently and further, it helps to build energy control strategy since battery power can be controlled easily.I.