Selection of Time Headway in Connected and Autonomous Vehicle Platoons under Noisy V2V Communication

TL;DR

This paper addresses robust string stability in connected and autonomous vehicle platoons under noisy V2V communication by modeling the acceleration information from the predecessor as transmitted over an $n$-bit channel with signal-to-noise ratio $\rho$. It develops a Constant Time Headway Policy (CTHP) based control law and derives a deterministic averaged model that yields a spacing-error propagation transfer function $\tilde{H}(s;\tau)$ with numerator $\tilde{\mathcal{N}}(s)= \tilde{k}_a s^2 + k_v s + k_p$ and denominator $\mathcal{D}(s)= \tau s^3 + s^2 + \gamma s + k_p$, where $\gamma = k_v + h_w k_p$ and $\tilde{k}_a = k_a\mathbb{E}[w_{i,i-1}(t)]$. The authors establish robustness conditions $\|\tilde{H}(j\omega;\tau)\|_\infty \le 1$ for all $\tau \in (0,\tau_0]$, derive bounds and optimal expressions for $k_a^*$ and $h_{w,lb}^*$ as functions of the SNR $\rho$, and show that a nonempty feasible region for $(k_p,k_v)$ exists even under channel noise. Numerical simulations corroborate the theory, demonstrating how to synthesize gains and time headway to guarantee robust stability at a given $\rho$, and highlight throughput gains from optimal headway choices. The results provide a principled procedure for selecting CTHP gains and $h_w$ under noisy V2V to ensure safe and efficient platooning in practice.

Abstract

In this paper, we investigate the selection of time headway to ensure robust string stability in connected and autonomous vehicle platoons in the presence of signal noise in Vehicle-to-Vehicle (V2V) communication. In particular, we consider the effect of noise in communicated vehicle acceleration from the predecessor vehicle to the follower vehicle on the selection of the time headway in predecessor-follower type vehicle platooning with a Constant Time Headway Policy (CTHP). Employing a CTHP based control law for each vehicle that utilizes on-board sensors for measurement of position and velocity of the predecessor vehicle and wireless communication network for obtaining the acceleration of the predecessor vehicle, we investigate how time headway is affected by communicated signal noise. We derive constraints on the CTHP controller gains for predecessor acceleration, velocity error and spacing error and a lower bound on the time headway which will ensure robust string stability of the platoon against signal noise. We provide comparative numerical simulations on an example to illustrate the main result.

Figures (13)

• Figure 1: Autonomous and connected vehicle platoon with V2V communication.
• Figure 2: An illustration of the admissible region for the signal noise in the communicated acceleration signal ($\rho = 5$).
• Figure 3: An illustration of the admissible region of the communicated acceleration signal with respect to the actual one ($\rho = 5$).
• Figure 4: $f(k_a)$ vs. $k_a$ when $\rho = 5$.
• Figure 5: The feasible region of $k_p$ and $k_v$ when $k_a = 0.5$, $h_w = 0.95$ s.