Design and modeling of a parallel hydraulic hybrid bus

Abstract

In the present paper a hydraulic hybrid propulsion system for an urban bus has been designed, modeled and simulated. The propulsion system consists of a diesel Internal Combustion Engine (ICE) as the primary and a hydraulic pump/motor (P/M) as the secondary power generation components. The hydraulic accumulators have been used as the energy storage components. The two power generating components have been connected to the driven shaft through a post-transmission torque coupling. For designing of hybrid propulsion system, the initial sizing of two power generation components has been performed by using MATLAB software. Then, the hydraulic hybrid propulsion components have been modeled in the MATLAB/Simulink and are combined to form a feed-forward model of the hydraulic hybrid bus. In addition, a control strategy has been designed so as to distribute appropriate torque among the hybrid power generation components. This control strategy also includes regenerative braking. After the designing and modeling of the hydraulic hybrid bus, its operation has been simulated in the Tehran and the Nuremburg drive cycles and assessment of fuel consumption and performance are obtained. In comparison to the conventional bus, at least 26 percent reduction in the fuel consumption of the hydraulic hybrid bus has been achieved by the simulation results.