Efficiency control algorithm for hybrid wheel loader based on instantaneous total system efficiency equations and demand frequency dependent battery utilisation

Abstract

Energy management systems (EMSs) play a crucial role in reducing the fuel consumption of series hybrid electric wheel loaders. However, designing an EMS is challenging due to unpredictable driving cycles and the necessity of maintaining a certain level of battery energy reserve. Optimisation-based strategies are widely adopted in the literature; however, these methods rely on prior estimations of the duty cycle, making them highly sensitive to prediction inaccuracies. Such inaccuracies can cause fuel consumption to deviate from near-optimal performance under real-world conditions. To address this limitation, this paper proposes a novel optimisation-based algorithm that maximises efficiency, termed efficiency control algorithm (ECA), guiding the system toward higher efficiency operating points under inaccuracies of the estimation. The ECA was evaluated utilising real-world wheel loader data in a transient model-in-the-loop simulation under two scenarios with distinct load behaviours. The results demonstrate that ECA outperforms the adaptive equivalent consumption minimisation strategy, achieving efficiencies of 0.3762 pu and 0.3703 pu, which correspond to deviations of only 2.0 % and 3.6 % from the theoretical maximum efficiency.