Dynamics of a long platoon of cooperative adaptive cruise control vehicles

Abstract

The dynamics of long platoons of adaptive cruise control vehicles with Vehicle-to-Vehicle communications are analyzed. The effects of feedback of the position, velocity and acceleration from the platoon’s lead vehicle are evaluated with numerical simulations. An alternative derivation of the equations pertaining to small deviations about equilibrium and a linear extrapolation for a general control law are given. Under a constant headway time range policy the upstream vehicles of platoons with lead velocity feedback reach a velocity plateau as the lead vehicle accelerates. The headway remains constant at the equilibrium value until the end of the plateau. Simulations show that velocity feedback produces improvements, especially reductions of platoon acceleration. Adding position feedback smooths the response to lead vehicle acceleration. Unlike the case of constant headway range policy where acceleration feedback is essential, only minor effects are found for acceleration feedback for the constant headway time policy. Simulations show that typical communication interruptions (treated simply as delays) do not have significant effects. However, if simulations take into account the discrete nature of occasional failures of information transmissions (packet drops), oscillations are induced in platoon vehicle acceleration. Simulations demonstrate that replacing feedback from the lead vehicle with feedback from a few immediately preceding vehicles can be effective.