| dc.description.abstract | Vehicle platooning is a concept in which a group of vehicles follow a lead vehicle and travel together in a coordinated formation. Various control policies have been suggested for the longitudinal control of vehicles in a vehicle platoon. Constant Time Headway Policy (CTHP) employs a desired inter-vehicular distance proportional to the velocity of the vehicle known as time headway. Previous studies have focused on finding the minimum employable time headway that would guarantee string stability in the presence of disturbances. However, those studies have assumed homogeneous parameters for all vehicles in the platoon. This study investigates the effects of heterogeneity in time headway on string stability of vehicle platoons. In this study, the error propagation transfer function for a platoon with heterogeneous time headways is presented. It is found that, owing to the stability of this error propagation transfer function, the minimum employable time headway for heterogeneous case has to be greater than τo/ka , which is higher than that of the homogeneous case given by 2τo/1+ka . A sufficient condition for string stability is presented, using which string stability of the platoon can be guaranteed if the headway values are monotonically decreasing from the head to the tail of the platoon. However, using this sufficient condition does not provide any insights on how different combinations of headways affect string stability of the vehicle platoon. Finally, to investigate the evolution of spacing errors for other combinations of headways, the transfer function between error of a vehicle and the lead vehicle acceleration is derived. From this error transfer function, it is found that, for a finite range of time headways, the maximum spacing error of a vehicle for any combination of headways can be bounded irrespective of the size of the platoon. | en |
