Energy Efficient and Safe Control Strategy for Electric Vehicles including Driver Preference

Abstract

In this manuscript, a control strategy for electric vehicles is developed to optimise the energy consumption while respecting constraints associated with both inter-vehicle safety and comfort, which is a challenge in typical optimal control solution methodologies. Firstly, the long-term optimal control is developed using Pontryagin's Maximum Principle (PMP). Thereafter, the obtained PMP solution is used to bound the state space for a computationally tractable Dynamic Programming (DP) optimisation to ensure the satisfaction of the safety constraints. While the acceleration subproblem solution is similar to internal combustion engine vehicles (ICEVs), the combination of regenerative and hydraulic braking significantly alters the nature of the optimal braking profile. Since a DP solution is not tractable for real-time implementation of combined braking, a fast heuristic is developed, which achieves 98% of the optimal energy recovery calculated by the DP in the simulated cases. Simulation results demonstrate that the proposed strategy respects the acceleration and safety constraints while saving approximately 5% energy use without significantly increasing travel time. Further simulations were conducted to evaluate the effect of driver preferences on energy use. It was shown that a 9.5% reduction in energy use if the driver is willing to accept a 10% speed reduction.