A novel braking energy management strategy for battery electric trucks with hydraulic retarder on long downhill

Battery electric heavy-duty trucks (BETs) are crucial for future sustainable transport, especially for long-distance transportation scenarios. However, driving on long downhill roads poses safety risks due to thermal degradation of braking components. The composite braking system of BETs integrates friction braking, regenerative braking, and auxiliary braking subsystems. This paper proposes a novel braking energy management strategy based on receding horizon control to optimize braking energy distribution during downhill driving. The strategy targets four objectives: maximizing brake energy recovery, minimizing battery temperature rise rate, minimizing brake drum temperature rise, and limiting hydraulic retarder gear shifts. Dynamic programming algorithm is adopted to solve the optimal control sequence, while ensuring computational efficiency by constraining the reachable ranges of state variables. Offline and driver-in-the-loop real-time simulations validate the effectiveness of the proposed strategy. The results demonstrate that the strategy prevents brake thermal degradation, ensuring braking safety, while recovering substantial braking energy and preserving battery health. Compared to a benchmark strategy, it delivers comparable control performance but with enhanced dynamic response. Furthermore, it significantly reduces hydraulic retarder gear shifts compared to the rule-based strategy, thereby improving braking torque tracking performance and comfort.