Abstract
In this paper, control analysis was performed for a hybrid electric vehicle (HEV) equipped with a continuously variable transmission (CVT) under various driving conditions. First, a dynamic CVT model was developed by considering hydraulic and mechanical losses. The hydraulic loss accounts for the majority of the total losses at low vehicle speeds, whereas the mechanical loss accounts for the majority at high speeds. In addition, CVT ratio control and clamping force control strategies were developed, including manipulation of the CVT shift dynamics. On the basis of the dynamic model of the CVT, an HEV performance simulator was developed using Argonne National Laboratory (ANL)’s model-based simulation program, Autonomie. Second, by analysing the test results from ANL, an engine optimal operating line was constructed on the basis of the engine brake-specific fuel consumption. Third, the battery state-of-charge range and the battery characteristics of the maximum charging and discharging power were investigated. Using the analysis results, vehicle operation control strategies were developed for the acceleration, cruising, deceleration and idling modes. Also, control algorithms were developed for each vehicle operation mode. Finally, the control algorithms were verified by comparing the simulation results with the test results.