A two-layer control strategy for fuel-efficient connected vehicles

This paper proposes a two-layer control strategy to enhance connected vehicles fuel efficiency. Compared with previous works, this study proposes an approach to optimize both the vehicle speed and gearbox position to achieve better fuel efficiency. The control task is given in two stages: the upper layer and the lower layer. Before trip departure, the upper layer concurrently optimizes the vehicle speed and gearbox position based on road map information, and engine and vehicle parameters for an entire route. Then, while driving, the lower layer is used to follow the pre-computed optimal profiles. Model predictive control follows the optimal speed while ensuring an adaptive safe distance constraint with a preceding vehicle. For gear shifting, an online shift control assuring the tracking of the optimal gear position is developed based on look-ahead road data and vehicle actions. The effectiveness of the proposed control strategy was evaluated with comprehensive simulations and comparison tests using Matlab and CarSim software. The mean online optimization calculation time is 0.065 s, indicating its real-time capability. The proposed method can be used as a driving assist system or implemented as a speed and gear controller for self-driving vehicles.