Fuzzy-logic-based torque control strategy for parallel-type hybrid electric vehicle

In a parallel-type hybrid electric vehicle (HEV), torque assisting and battery recharging control using the electric machine is the key point for efficient driving. In this paper, by adopting the decision-making property of fuzzy logic, the driving map for an HEV is made according to driving conditions. In this fuzzy logic controller, the induction machine torque command is generated from the acceleration pedal stroke and its rotational speed. To construct a proper rule base of fuzzy logic, the dynamo test and road tests for a hybrid powertrain are carried out, where the torque and the nitrogen oxides (NO_x) emission characteristic of the diesel engine and the driver´s driving patterns are acquired, respectively. An HEV, a city bus for shuttle service, with the proposed fuzzy-logic-based driving strategy was built and tested at a real service route. It reveals that the improved NO_x emission and better charge balance without an extra battery charger over the conventional deterministic-table-based strategy