Comparison of early-stage design methods for a two-mode hybrid electric vehicle

A challenge in the early-stage design of hybrid propulsion system architectures is dealing with a vast design space consisting of distinct subsystems, such as engine, motor, transmission, and battery. In this paper, two design optimization methods for a two-mode hybrid vehicle are examined: The first integrates the subsystems into a single virtual system and solves an All-In-One (AIO) problem; the second maintains system decomposition and updates individual subsystem designs through iterative exchange of information. The analysis models are detailed high-fidelity simulations of engine and electric motor components combined with two-mode transmission and overall vehicle models. Results indicate that the AIO system-optimal solution provides little additional benefit, suggesting that the industry practice to use ad-hoc decomposition-based optimization is sufficient for early-stage design in this class of problems.