A Comparison of Fixed and Dynamic Regenerative Braking Low-Speed Boundary on Eco-driving of Autonomous Electric Vehicles

Regenerative Braking (RB) is one of the capabilities of Electric Vehicles (EVs) which has the potential to not only make EVs more efficient but also extend the range of these vehicles for a single charge. This capability has the potential to provide even more energy savings when considered in the speed planning stage of Autonomous Electric Vehicles (AEVs). The RB process, however, suffers from low-speed limitation which can have adverse effects on energy recuperation at low speeds. This paper presents a comparison of two approaches that use fixed and dynamic low-speed boundaries (LSBs) to address RB limitation at low speeds and studies the impact of each approach on the eco-driving control problem for AEVs. The eco-driving problem is executed with Mixed Integer Linear Programming (MILP), and two different case studies associated with the operation of RB at low speeds are analyzed for a predetermined signalized route. It is shown that up to 3.9% increase in energy harvesting is achievable by employing dynamic LSB. The results of this study further illustrate the importance of considering a dynamic RB boundary when it comes to solving the eco-driving problem for AEVs.