String Stability of Connected Vehicle Platoons Under Lossy V2V Communication

Recent advances in vehicle connectivity have allowed formation of autonomous vehicle platoons for improved mobility and traffic throughput. In order to avoid a pile-up in such platoons, it is important to ensure platoon (string) stability, which is the focus of this work. As per conventional definition of string stability, the power (2-norm) of the spacing error signals should not amplify downstream in a platoon. But in practice, it is the infinity-norm of the spacing error signal that dictates whether a collision occurs. We address this discrepancy in the first part of our work, where we reconsider string stability from a safety perspective and develop an upper limit on the maximum spacing error in a homogeneous platoon as a function of the acceleration maneuver of the lead vehicle. In the second part of this paper, we extend our previous results by providing the minimum achievable time headway for platoons with two-predecessor lookup schemes experiencing burst-noise packet losses. Finally, we utilize throttle and brake maps to develop a longitudinal vehicle model and validate it against a Lincoln MKZ which is then used for numerical corroboration of the proposed time headway selection algorithms.

I. Introduction

Vehicle platooning has been studied since the late 1950s, with early efforts on car following [1] simply attempting to replicate human driving behaviour. Modern approaches to platooning focus on achieving small inter-vehicle spacing to improve traffic throughput (mobility) as well as reduce fuel consumption [2], [3]. At the same time, a sufficient headway has to be maintained between vehicles to prevent pile-ups. Consequently, a majority of contemporary research on vehicle platooning involves achieving the smallest possible inter-vehicle spacing while guaranteeing safety.