Characterization of Bidirectional Information Flow Topology on Time Headway in Connected and Autonomous Vehicles

This paper investigates the effect of bidirectional Information Flow Topology (IFT) on reducing the minimum employable time headway in connected and autonomous vehicles described by double integrator dynamics with first-order inertia acceleration actuation model subject to uncertain parasitic actuation lag. First, an asymmetric bidirectional control law is designed by integrating the motion information from the adjacent vehicles of both directions. Second, the resultant bidirectional intervehicular spacing error propagation is modeled as a two-input single-output system. Further, by using tools and techniques from H ∞ control and singular value decomposition, the bidirectional string stability conditions characterized by the feasible ranges of the time headway with respect to the uncertainty bounds of the parasitic actuation lag as well as the bidirectional control gains are deduced, the quasi necessity of which for ensuring unidirectional string stability is also elaborated. In addition, the inclusion of the internal stability criterion in the bidirectional string stability conditions is revealed as well. Moreover, the potential of bidirectional IFT in lowering both local and global minimum allowable time headways is expounded by comparing with the unidirectional one. An illustrative example and comparative simulations are finally presented to validate the effectiveness of the achieved results.