An Adaptive Spacing Policy Guaranteeing String Stability in Multi-Brand Ad Hoc Platoons

A method is presented for the longitudinal control of autonomous vehicles forming a multi-brand, ad hoc platoon. A leader and predecessor following (LPF) control architecture is known to allow string stable platooning with shorter safety gaps between vehicles as compared with predecessor following schemes. General LPF strategies, however, require the exact knowledge of spacing policies of predecessor vehicles for correctly specifying a spacing with respect to the leader. It follows that arbitrary spacing policies in ad hoc platoons prevent the applicability of classical LPF control structures. It is shown in this paper that it is possible to exploit the advantages of LPF architectures in multi-brand platoons without a priori knowledge of spacing policies of predecessors. The unknown spacing policies are replaced by a virtual one, which serves as an input to a two degree of freedom LPF controller. The resulting control structure enables the organization of ad hoc platoons consisting of vehicles with different spacing policies. Computer simulations are presented to illustrate the statements.