In this paper, the performance of a hydraulic control system using a direct solenoid valve was investigated for a two mode hybrid electric vehicle (HEV). Experimental apparatuses for each direct solenoid valve and for the hydraulic control system were developed to evaluate the control performance of the hydraulic system. The dynamic characteristics of the direct solenoid valve and hydraulic control system were analyzed via experiment and simulation. Using a dynamic model of the hydraulic control system, a performance simulator for a two mode HEV was developed. The mode change performance from the first to the third fixed gear modes and from the first fixed gear mode to the input split mode were investigated using the simulator. It was found that mode change was carried out via the hydraulic pressure control of the clutch and brake using the direct solenoid valve
