String stability of interconnected vehicles under communication constraints

In this paper, we present a novel modelling and string stability analysis method for an interconnected vehicle string in which information exchange takes place via wireless communication. The usage of wireless communication introduces time-varying sampling intervals, delays, and communication constraints of which the impact on string stability requires a careful analysis. In particular, we study a Cooperative Adaptive Cruise Control (CACC) system which regulates inter-vehicle distances in a vehicle string and utilizes information exchange between vehicles through wireless communication in addition to local sensor measurements. The propagation of disturbances through the interconnected vehicle string is inspected by using the notion of so-called string stability which is formulated here in terms of an ℒ2-gain requirement from disturbance inputs to controlled outputs. This paper provides conditions on the uncertain sampling intervals and delays under which string stability can still be guaranteed. These results support the design of CACC systems that are robust to uncertainties introduced by wireless communication.