City-bus-route demand-based efficient coupling driving control for parallel plug-in hybrid electric bus

Recently, plug-in hybrid electric bus has been one of the energy-efficient solutions for urban transportation. However, the current vehicle efficiency is far from optimum, because the unpredicted external driving conditions are difficult to be obtained in advance. How to further explore its fuel-saving potential under the complicated city bus driving cycles through an efficient control strategy is still a hot research issue in both academic and engineering area. To realize an efficient coupling driving operation of the hybrid powertrain, a novel coupling driving control strategy for plug-in hybrid electric bus is presented. Combined with the typical feature of a city-bus-route, the fuzzy logic inference is employed to quantify the driving intention, and then to determine the coupling driving mode and the gear-shifting strategy. Considering the response deviation problem in the execution layer, an adaptive robust controller for electric machine is designed to respond to the transient torque demand, and instantaneously compensate the response delay and the engine torque fluctuation. The simulations and hard-in-loop tests with the actual data of two typical driving conditions from the real-world city-bus-route are carried out, and the results demonstrate that the proposed method could guarantee the hybrid powertrain to track the actual torque demand with 10.4% fuel economy improvement. The optimal fuel economy can be obtained through the optimal combination of working modes. The fuel economy of plug-in hybrid electric bus can be significantly improved by the proposed control scheme without loss of drivability.