Power management strategy for a parallel hybrid electric truck

TLDR

Hybrid vehicle techniques are studied for their potential to improve fuel economy and drivability, yet intuition‑based control strategies often fail to exploit the full capabilities of dual‑power‑source vehicles. This paper proposes a procedure to design a near‑optimal power‑management strategy for parallel hybrid electric trucks. The procedure defines a cost function that balances fuel consumption and emissions, applies dynamic programming to determine optimal gear shifts and power split while maintaining battery SOC, extracts implementable near‑optimal rules from the DP solution, and evaluates the strategy using the HE‑VESIM hybrid vehicle model with a trade‑off analysis between fuel economy and emissions. The strategy achieves significant emission reductions with only a modest increase in fuel consumption.

Abstract

Hybrid vehicle techniques have been widely studied recently because of their potential to significantly improve the fuel economy and drivability of future ground vehicles. Due to the dual-power-source nature of these vehicles, control strategies based on engineering intuition frequently fail to fully explore the potential of these advanced vehicles. In this paper, we present a procedure for the design of a near-optimal power management strategy. The design procedure starts by defining a cost function, such as minimizing a combination of fuel consumption and selected emission species over a driving cycle. Dynamic programming (DP) is then utilized to find the optimal control actions including the gear-shifting sequence and the power split between the engine and motor while subject to a battery SOC-sustaining constraint. Through analysis of the behavior of DP control actions, near-optimal rules are extracted, which, unlike DP control signals, are implementable. The performance of this power management control strategy is studied by using the hybrid vehicle model HE-VESIM developed at the Automotive Research Center of the University of Michigan. A tradeoff study between fuel economy and emissions was performed. It was found that significant emission reduction could be achieved at the expense of a small increase in fuel consumption.