An energy saving rule-based strategy for electric-hydraulic hybrid wheel loaders

Recently, hybrid electric vehicles are getting popular as they are both clean and efficient. As one of the hybrid electric powertrains, the battery powered parallel electric-hydraulic hybrid powertrain (PEHHP) is zero emission and has better drive performance. But the energy use of the PEHHP highly depends on the control strategy. A proper energy management strategy is critical for torque distribution and hybrid powertrain efficiency improvement. In this paper, a real-time rule-based strategy is proposed to determine the torque distributions of the PEHHP. The proposed rule-based strategy is based on the component efficiency analysis. And it optimizes the electric motor operating points. Experiments are conducted to show the operation results of the parallel electric-hydraulic hybrid wheel loaders. The powertrain energy use of the proposed rule-based strategy is close to that of the global optimal dynamic programing strategy, with energy use gaps of 2.99%, and 6.10% in simulation and experiment respectively.